In this short information article we will look at the main technical characteristics of speakers that you need to know when choosing car speakers or when making car speakers with your own hands.
The picture below shows the main components of a typical audio speaker:
Let's consider what features good sound speakers for car acoustics should have.
The powerful speaker will have two separate voice coils wound on the same frame. Each coil can be connected to a separate channel on a stereo amplifier, or they can be connected in series or in parallel and powered from the same source. One DVC speaker can be used instead of two conventional speakers when space is at a premium.
Filters
A filter is an electronic circuit in an audio system that allows certain frequencies to pass through at the same time while blocking others. Active filters contain components that require additional power. These are so-called operational amplifiers (op-amps) and, as a rule, they are built in front of the main amplifier. Passive filters do not contain components requiring power and are usually built between the amplifier and speaker.
Types of filters that are commonly used in audio system designs:
- Low-pass filters: pass low frequencies, attenuate high frequencies.
- High-pass filters: passes high frequencies, attenuates low frequencies.
- Adjustable Bandwidths: When frequencies outside a certain range are attenuated.
Isobaric speaker system
The name comes from the ancient Greek ἴσος - “same” and βάρος “heaviness”. In other words, a distributed load. This is a method using two speakers working in tandem to achieve a smaller cabinet size while keeping design requirements in mind. Theoretically, the VAS (Value Equivalent Speaker Volume) of a dual system will be half that of two separate speakers, resulting in the design size of the enclosure being halved as well. The sensitivity of an isobar system will be the same as a single speaker system, but you will lose some SPL power. The clamshell mount, where the speakers are mounted face to face and one speaker is connected out of phase with the other, seems to be the most popular isobaric system in use today, as it is the easiest to manufacture.
Wife Acceptance Factor (WAF) - wife approval factor
In general, refers to design elements that increase the likelihood that your wife will approve of the purchase of expensive consumer electronics products such as high-end speaker systems, home theaters and personal computers, etc. Stylish, compact shapes and attractive colors tend to increase WAF levels. The term is playful electronics slang for "Form Factor" and "Form Attractiveness" and comes from the gender stereotype that men are predisposed to value technical innovations based on efficiency, while women are attracted to visual and aesthetic factors. In other words, the rough measurement is that you can go home to your missus without her making a fuss about the appearance of your acquisition.
Subwoofer
A speaker designed to reproduce low sound frequencies at an adequate volume. Most subwoofers, or "subs" as they are commonly called, are designed to operate from 80 Hz and below to a level where the human ear can detect sounds. The bass units of small three-component systems are also commonly called "subwoofers", but they often have limited ability to reproduce frequencies below 50 Hz or so.
T/S (Tiel Small) parameters
A collection of terms/parameters commonly used to describe the characteristics of a specific speaker. The most common T/S parameters we encounter are:
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Taken from the website of the magazine "Avtozvuk"Context
In the previous part of our conversation, it became clear what is good and what is bad about different types of acoustic design. It would seem that now “the goals are clear, let’s get to work, comrades..” But that was not the case. Firstly, the acoustic design, in which the speaker itself is not installed - just a box assembled with varying degrees of care. And often it is impossible to assemble it until it is determined which speaker will be installed in it. Secondly, and this is the main fun in the design and manufacture of car subwoofers - the characteristics of a subwoofer are worth little outside the context of the characteristics, at least the most basic ones, of the car where it will work. There is also a third thing. A mobile speaker system that is equally suited to any music is an ideal rarely achieved. A competent installer can usually be recognized by the fact that, when “taking readings” from a client ordering an audio installation, he asks to bring samples of what the client will listen to on the system he ordered after its completion.
As you can see, there are a lot of factors influencing the decision and there is no way to reduce everything to simple and unambiguous recipes, which turns the creation of mobile audio installations into an activity very much akin to art. But it is still possible to outline some general guidelines.
Tsifir
I hasten to warn the timid, lazy and humanitarian educated - there will be practically no formulas. As long as possible, we will try to do without even a calculator - a forgotten method of mental calculation.
Subwoofers are the only part of car acoustics where measuring harmony with algebra is not a hopeless task. To put it bluntly, it is simply unthinkable to design a subwoofer without calculations. The initial data for this calculation are the speaker parameters. Which? Yes, not the ones they hypnotize you with in the store, rest assured! To calculate, even the most approximate, characteristics of a low-frequency loudspeaker, you need to know its electromechanical parameters, of which there are a ton. This is the resonant frequency, and the mass of the moving system, and the induction in the gap of the magnetic system, and at least two dozen more indicators, some understandable and some not so clear. Upset? Not surprising. Two Australians, Richard Small and Neville Thiel, were similarly upset about twenty years ago. They suggested using a universal and fairly compact set of characteristics instead of the Tsifiri mountains, which immortalized, quite deservedly, their names. Now, when you see a table in the speaker description entitled Thiel/Small parameters (or simply T/S) - you know what we're talking about. And if you don’t find such a table, move on to the next option - this one is hopeless.
The minimum set of characteristics that you will need to find out is:
Natural resonant frequency of the speaker Fs
Full quality Qts
Equivalent volume Vas.
In principle, there are other characteristics that would be useful to know, but this, in general, is enough. (the diameter of the speaker is not included here, since it is already visible without documentation.) If at least one parameter from the “extraordinary three” is missing, the matter is at seams. Well, now what does all this mean?
Natural frequency- this is the resonance frequency of the speaker without any acoustic design. This is how it is measured - the speaker is suspended in the air at the greatest possible distance from surrounding objects, so that now its resonance will depend only on its own characteristics - the mass of the moving system and the stiffness of the suspension. There is an opinion that the lower the resonant frequency, the better the subwoofer will be. This is only partly true; for some designs, an excessively low resonance frequency is a hindrance. For reference: low is 20 - 25 Hz. Below 20 Hz is rare. Above 40 Hz is considered high for a subwoofer.
Complete goodness. The quality factor in this case is not the quality of the product, but the ratio of elastic and viscous forces existing in the moving speaker system near the resonance frequency. The moving speaker system is much like a car suspension, where there is a spring and a shock absorber. A spring creates elastic forces, that is, it accumulates and releases energy during oscillations, and a shock absorber is a source of viscous resistance; it does not accumulate anything, but absorbs and dissipates in the form of heat. The same thing happens when the diffuser and everything attached to it vibrates. A high quality factor means that elastic forces predominate. It's like a car without shock absorbers. It is enough to run over a pebble and the wheel will start jumping, unrestrained by anything. Jump at the very resonant frequency that is inherent in this oscillatory system.
In relation to a loudspeaker, this means an overshoot of the frequency response at the resonance frequency, the greater the higher the total quality factor of the system. The highest quality factor, measured in thousands, is that of a bell, which, as a result, does not want to sound at any frequency other than the resonant one, fortunately no one demands this from it.
A popular method for diagnosing a car's suspension by swaying is nothing more than measuring the quality factor of the suspension using a homemade method. If you now put the suspension in order, that is, attach a shock absorber parallel to the spring, the energy accumulated during compression of the spring will not all come back, but will be partially ruined by the shock absorber. This is a decrease in the quality factor of the system. Now let's go back to the dynamics. Is it okay that we go back and forth? This, they say, is useful... Everything seems to be clear with the spring on the speaker. This is a diffuser suspension. What about the shock absorber? There are two shock absorbers, working in parallel. The total quality factor of a speaker consists of two things: mechanical and electrical. The mechanical quality factor is determined mainly by the choice of suspension material, mainly by the centering washer, and not by the external corrugation, as is sometimes believed. There are usually no large losses here and the contribution of the mechanical quality factor to the total does not exceed 10 - 15%. The main contribution comes from the electrical quality factor. The stiffest shock absorber operating in the oscillating system of a speaker is an ensemble of a voice coil and a magnet. Being an electric motor by its nature, it, as befits a motor, can work as a generator and this is exactly what it does near the resonance frequency, when the speed and amplitude of movement of the voice coil are maximum. Moving in a magnetic field, the coil generates current, and the load for such a generator is the output impedance of the amplifier, that is, practically zero. It turns out to be the same electric brake that all electric trains are equipped with. There, too, when braking, the traction motors are forced to work as generators, and their load is a battery of braking resistors on the roof.
The amount of current generated will naturally be greater, the stronger the magnetic field in which the voice coil moves. It turns out that the more powerful the speaker magnet, the lower, other things being equal, its quality factor. But, of course, since both the length of the winding wire and the width of the gap in the magnetic system are involved in the formation of this value, it would be premature to draw a final conclusion based only on the size of the magnet. And the preliminary one - why not?...
Basic concepts - the total quality factor of the speaker is considered low if it is less than 0.3 - 0.35; high - more than 0.5 - 0.6.
Equivalent volume. Most modern loudspeaker drivers are based on the "acoustic suspension" principle.
We sometimes call them “compression”, which is incorrect. Compression heads are a completely different story, associated with the use of horns as an acoustic design.
The concept of an acoustic suspension is to install a speaker in a volume of air whose elasticity is comparable to the elasticity of the speaker suspension. In this case, it turns out that another spring was installed in parallel to the spring already existing in the suspension. In this case, the equivalent volume will be such that the newly appeared spring is equal in elasticity to the already existing one. The amount of equivalent volume is determined by the stiffness of the suspension and the diameter of the speaker. The softer the suspension, the larger the air cushion will be, the presence of which will begin to disturb the speaker. The same thing happens with a change in the diameter of the diffuser. A large diffuser at the same displacement will compress the air inside the box more strongly, thereby experiencing a greater response force of elasticity of the air volume.
It is this circumstance that often determines the choice of speaker size, based on the available volume to accommodate its acoustic design. Large diffusers create the prerequisites for high output from the subwoofer, but also require large volumes. The argument from the repertoire of the room at the end of the school corridor “I have more” must be used carefully here.
The equivalent volume has interesting relationships with the resonant frequency, without awareness of which it is easy to miss. The resonant frequency is determined by the rigidity of the suspension and the mass of the moving system, and the equivalent volume is determined by the diameter of the diffuser and the same rigidity.
As a result, such a situation is possible. Let's assume there are two speakers of the same size and with the same resonance frequency. But only one of them achieved this frequency value due to a heavy diffuser and a rigid suspension, while the other, on the contrary, had a light diffuser with a soft suspension. The equivalent volume of such a pair, despite all the external similarity, can differ very significantly, and when installed in the same box, the results will be dramatically different.
So, having established what the vital parameters mean, let’s finally begin to choose a betrothed. The model will be like this - we believe that you have decided, based on, say, the materials of the previous article in this series, the type of acoustic design and now you need to choose a speaker for it from hundreds of alternatives. Having mastered this process, the reverse process, that is, choosing a suitable design for the selected speaker, will be easy for you. I mean, almost without difficulty.
Closed box
As was said in the above article, a closed box is the simplest acoustic design, but far from primitive; on the contrary, it has, especially in a car, a number of important advantages over others. Its popularity in mobile applications is not fading at all, so we’ll start with it.
What happens to the speaker's performance when installed in a closed box? It depends on one single quantity - the volume of the box. If the volume is so large that the speaker practically does not notice it, we come to the infinite screen option. In practice, this situation is achieved when the volume of the box (or other closed volume located behind the diffuser, or, more simply put, what is there to hide - the trunk of a car) exceeds the equivalent volume of the speaker by three times or more. If this relationship is satisfied, the resonant frequency and overall quality factor of the system will remain almost the same as they were for the speaker. This means that they must be chosen accordingly. It is known that the acoustic system will have the smoothest frequency response with a total quality factor of 0.7. At lower values, the impulse characteristics improve, but the frequency decay begins quite high in frequency. At large values, the frequency response becomes higher near resonance, and the transient characteristics deteriorate somewhat. If you are focused on classical music, jazz or acoustic genres, the optimal choice would be a slightly overdamped system with a quality factor of 0.5 - 0.7. For more energetic genres, emphasizing the lows, which is achieved with a quality factor of 0.8 - 0.9, will not hurt. And finally, rap fans will have a blast if the system has a quality factor equal to one or even higher. The value of 1.2 should, perhaps, be recognized as the limit for any genre that claims to be musical.
We must also keep in mind that when installing a subwoofer in the car interior, low frequencies rise, starting from a certain frequency, determined by the size of the cabin. Typical values for the beginning of the rise in frequency response are 40 Hz for a large car, such as a jeep or minivan; 50 - 60 for medium, like an eight or a loin; 70 - 75 for a small one, from Tavria.
Now it’s clear - to install in the infinite screen mode (or Freeair, if it doesn’t bother you that the latter name is patented by Stillwater Designs), you need a speaker with a total quality factor of at least 0.5, or even higher, and a resonant frequency no lower than 40 hertz - 60, depending on what you bet. Such parameters usually mean a rather rigid suspension, which is the only thing that saves the speaker from overload in the absence of “acoustic support” from the closed volume. Here's an example - Infinity produces in the Reference and Kappa series versions of the same heads with the indices br (bass reflex) and ib (infinite baffle). The Thiel-Small parameters, for example, for the ten-inch Reference differ as follows:
Parameter T/S 1000w.br 1000w.ib
Fs 26 Hz 40 Hz
Vas 83 l 50 l
It can be seen that the ib version, in terms of its resonant frequency and quality factor, is ready to work “as is,” and judging by both the resonance frequency and the equivalent volume, this modification is much tougher than the other one, optimized for operation in a bass reflex, and, therefore, is more likely to survive in difficult conditions Freeair.
But what happens if, without paying attention to the small letters, you drive into these conditions a speaker with the br index that looks like two peas in a pod? But here's what: due to the low quality factor, the frequency response will begin to fall off at frequencies of about 70 - 80 Hz, and the unrestrained “soft” head will feel very uncomfortable at the lower edge of the range, and it’s easy to overload it there.
So, we agreed:
For use in the “infinite screen” mode, you must select a speaker with a high total quality factor (not less than 0.5) and a resonant frequency (not less than 45 Hz), specifying these requirements depending on the type of predominant musical material and the size of the cabin.
Now about the “non-infinite” volume. If you place a speaker in a volume comparable to its equivalent volume, the system will acquire characteristics that are significantly different from those with which the speaker came into this system. First of all, when installed in a closed volume, the resonant frequency will increase. The rigidity has increased, but the mass has remained the same. The quality factor will also increase. Judge for yourself - by adding the rigidity of a small, that is, unyielding air volume to help stiffen the suspension, we thereby, as it were, installed a second spring, and left the old shock absorber.
As the volume decreases, the quality factor of the system and its resonant frequency increase equally. This means that if we saw a speaker with a quality factor of, say, 0.25, and we want to have a system with a quality factor of, say, 0.75, then the resonant frequency will also triple. What is it like on the speaker? 35 Hz? This means that in the correct volume, in terms of the shape of the frequency response, it will be 105 Hz, and this, you know, is no longer a subwoofer. So it doesn't fit. You see, you didn’t even need a calculator. Let's look at the other one. Resonant frequency 25 Hz, quality factor 0.4. The result is a system with a quality factor of 0.75 and a resonance frequency somewhere around 47 Hz. Quite worthy. Let’s try right there, without leaving the counter, to estimate how big the box will be needed. It is written that Vas = 160 l (or 6 cu.ft, which is more likely).
(I wish I could write the formula here - it’s simple, but I can’t - I promised). Therefore, for calculations at the counter, I’ll give you a cheat sheet: copy and put in your wallet if buying a bass speaker is part of your shopping plans:
The resonant frequency and quality factor will increase in If the volume of the box is from Vas
1.4 times 1
1.7 times 1/2
2 times 1/3
3 times 1/8
For us it’s about double, so it turns out to be a box with a volume of 50 - 60 liters. It will be a bit much... Let’s go with the next one. And so on.
It turns out that in order for a conceivable acoustic design to emerge, the speaker parameters not only must be in a certain range of values, but also be linked with each other.
Experienced people have combined this relationship into the Fs/Qts indicator.
If the Fs/Qts value is 50 or less, the speaker is born for a closed box. The required volume of the box will be smaller, the lower Fs or the smaller Vas.
By external data, “natural recluses” can be recognized by heavy diffusers and soft suspensions (which gives a low resonant frequency), not very large magnets (so that the quality factor is not too low), long voice coils (since the cone stroke of a speaker operating in a closed box , can reach quite large values).
Bass reflex
Another type of popular acoustic design is a bass reflex, which, with all the ardent desire, cannot be counted at the counter, even approximately. But you can estimate the suitability of the speaker for it. And we will generally talk about calculation separately.
The resonant frequency of a system of this type is determined not only by the resonant frequency of the speaker, but also by the bass reflex setting. The same applies to the quality factor of the system, which can change significantly with changes in the length of the tunnel, even with a constant volume of the housing. Since the bass reflex can be, unlike a closed box, tuned to a frequency close to or even lower than that of the speaker, the head’s own resonant frequency is “allowed” to be higher than in the previous case. This means, with a successful choice, a lighter diffuser and, as a result, improved impulse characteristics, which the bass reflex needs, since its “innate” transient characteristics are not the best, worse than that of a closed box, at least. But it is advisable to have the quality factor as low as possible, no more than 0.35. Reducing this to the same Fs/Qts indicator, the formula for choosing a speaker for a bass reflex looks simple:
Speakers with an Fs/Qts value of 90 or more are suitable for use in a bass reflex.
External signs of phase-inverted rock: light diffusers and powerful magnets.
Bandpasses (very briefly)
Bandpass loudspeakers, for all their loud advantages (this is in the sense of greatest efficiency in comparison with other types), are the most difficult to calculate and manufacture, and matching their characteristics with the internal acoustics of a car with insufficient experience can turn into absolute hell, so with this type When it comes to acoustic design, it’s better to walk the rocks and use the recommendations of the speaker manufacturers, although this ties your hands. However, if your hands are still in a free state and itching to try: for single bandpasses, almost the same speakers are suitable as for bass reflexes, and for double or quasi-bandpasses, they are the same or, more preferably, heads with an Fs/Qts index of 100 and higher.
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19.01.2006 15:47 # 0+
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Administration of the Car Audio ForumThis is a group of parameters introduced by A.N. Thiele and later R.H. Small, with the help of which it is possible to fully describe the electrical and mechanical characteristics of mid- and low-frequency loudspeaker heads operating in the compression region, i.e. when longitudinal vibrations do not occur in the diffuser and it can be likened to a piston.
Fs (Hz) is the natural resonance frequency of the loudspeaker head in open space. At this point its impedance is maximum.
Fc (Hz) - resonance frequency of the acoustic system for a closed enclosure.
Fb (Hz) - bass reflex resonance frequency.
F3 (Hz) - cutoff frequency at which the head output is reduced by 3 dB.
Vas (cubic m) - equivalent volume. This is a closed volume of air excited by the head, which has a flexibility equal to the flexibility Cms of the movable system of the head.
D (m) is the effective diameter of the diffuser.
Sd (sq.m) - effective diffuser area (approximately 50-60% of the design area).
Xmax (m) - maximum diffuser displacement.
Vd (cubic m) - excited volume (product of Sd by Xmax).
Re (Ohm) - resistance of the head winding to direct current.
Rg (Ohm) - output impedance of the amplifier, taking into account the influence of connecting wires and filters.
Qms (dimensionless quantity) - mechanical quality factor of the loudspeaker head at the resonant frequency (Fs), takes into account mechanical losses.
Qes (dimensionless quantity) - the electrical quality factor of the loudspeaker head at the resonant frequency (Fs), takes into account electrical losses.
Qts (dimensionless quantity) - the total quality factor of the loudspeaker head at the resonant frequency (Fs), takes into account all losses.
Qmc (dimensionless quantity) - mechanical quality factor of the acoustic system at the resonant frequency (Fs), takes into account mechanical losses.
Qec (dimensionless quantity) - the electrical quality factor of the acoustic system at the resonant frequency (Fs), takes into account electrical losses.
Qtc (dimensionless quantity) - the total quality factor of the acoustic system at the resonant frequency (Fs), takes into account all losses.
Ql (dimensionless quantity) is the quality factor of the acoustic system at frequency (Fb), taking into account leakage losses.
Qa (dimensionless quantity) is the quality factor of the acoustic system at frequency (Fb), taking into account absorption losses.
Qp (dimensionless quantity) is the quality factor of the acoustic system at frequency (Fb), taking into account other losses.
N0 (dimensionless quantity, sometimes %) - relative efficiency (efficiency) of the system.
Cms (m/N) - flexibility of the moving system of the loudspeaker head (displacement under the influence of mechanical load).
Mms (kg) - effective mass of the moving system (includes the mass of the diffuser and the air oscillating with it).
Rms (kg/s) - active mechanical resistance of the head.
B (T) - induction in the gap.
L (m) - length of the voice coil conductor.
Bl (m/N) - magnetic induction coefficient.
Pa - acoustic power.
Pe - electrical power.
C=342 m/s - speed of sound in air under normal conditions.
P=1.18 kg/m^3 - air density under normal conditions.
Le is the inductance of the coil.
BL is the magnetic flux density value multiplied by the length of the coil.
Spl – sound pressure level in dB.
Re: Thiel-Small parameters and acoustic design of the speaker.
Cool program BassBox 6.0 PRO for calculating the acoustic design of a 12MB speaker, serial number inside in *.txt file:The program has a huge database of din parameters from a large number of manufacturers, and can calculate the volume taking into account the wall thickness. In general, very comfortable.
Small-Thiele parameters
Small-Thiele parametersUntil 1970, there were no convenient, accessible, industry-standard methods for obtaining comparative data on loudspeaker performance. Individual tests performed by laboratories were too expensive and time-consuming. At the same time, methods for obtaining comparative data on loudspeakers were needed both by buyers to select the desired model, and by equipment manufacturers to more accurately describe their products and reasoned comparison of various devices.
Loudspeaker DesignIn the early seventies, a paper was presented at the AES conference, authored by Neville Thiele and Richard Small. Thiele was Chief Engineering and Development Engineer at the Australian Broadcasting Commission. At that time, he was in charge of the Federal Engineering Laboratory and was analyzing the operation of equipment and systems for transmitting audio and video signals. Small was a postgraduate student at the School of Engineering at the University of Sydney.
Thiele and Small's goal was to show how the parameters they derived could help match a cabinet to a specific speaker. However, the result is that these measurements provide significantly more information: they can draw much deeper conclusions about how a loudspeaker performs than based on the usual data on size, maximum output power or sensitivity.
List of parameters called “Small-Thiele parameters”: Fs, Re, Le, Qms, Qes, Qts, Vas, Cms, Vd, BL, Mms, Rms, EBP, Xmax/Xmech, Sd, Zmax, operating frequency range (Usable Freq. Range), rated power (Power Handling), sensitivity (Sensitivity).Fs
Re
This parameter describes the DC resistance of the speaker as measured using an ohmmeter. It is often called DCR. The value of this resistance is almost always less than the rated resistance of the speaker, which worries many buyers because they are afraid that the amplifier will be overloaded. However, because loudspeaker inductance increases with frequency, it is unlikely that the constant impedance will affect the load.
Le
This parameter corresponds to the inductance of the voice coil, measured in mH (millihenry). According to the established standard, inductance measurements are performed at a frequency of 1 kHz. As the frequency increases, the impedance will increase above the Re value, since the voice coil acts as an inductor. As a result, the impedance of the loudspeaker is not constant. It can be represented as a curve that changes with the frequency of the input signal. The maximum value of impedance (Zmax) occurs at the resonant frequency (Fs).
Q parameters
Vas/Cms
The Vas parameter tells you what the volume of air should be, which, when compressed to a volume of one cubic meter, would have the same resistance as the suspension system (equivalent volume). The flexibility factor of the suspension system for a given loudspeaker is denoted as Cms. Vas is one of the most difficult parameters to measure as air pressure changes according to humidity and temperature and thus requires a very high-tech laboratory to measure. Cms is measured in meters per newton (m/N) and represents the force with which the mechanical suspension system resists the movement of the diffuser. In other words, Cms corresponds to a measurement of the stiffness of the loudspeaker's mechanical suspension. The relationship between Cms and Q-parameters can be compared to the choice made by car manufacturers between increased comfort and improved driving performance. If we think of the peaks and troughs of an audio signal as the bumps in a road, then the loudspeaker suspension system is similar to the springs of a car - ideally it should withstand very fast driving on a road littered with large boulders.
Vd
This parameter indicates the maximum volume of air that can be pushed out by the diffuser (Peak Diaphragm Displacement Volume). It is calculated by multiplying Xmax (the maximum length of the part of the voice coil that extends beyond the magnetic gap) by Sd (the working surface area of the diffuser). Vd is measured in cubic centimeters. Subwoofers usually have the highest Vd values.
B.L.
Expressed in tesla per meter, this parameter characterizes the driving force of the loudspeaker. In other words, BL indicates how much mass a loudspeaker can “lift.” This parameter is measured as follows: a certain force is applied to the cone, directed inside the loudspeaker, and the current required to counteract the applied force is measured - the mass in grams is divided by the current in amperes. A high BL value indicates a very strong speaker.
mms
This parameter is a combination of the weight of the cone assembly and the mass of air flow moved by the speaker cone during operation. The weight of the diffuser assembly is equal to the sum of the weight of the diffuser itself, the centering washer and the voice coil. When calculating the mass of the air flow displaced by the diffuser, the air volume corresponding to the Vd parameter is used.
Rms
This parameter describes the mechanical resistance losses of the loudspeaker suspension system. It is a measurement of the absorptive qualities of a loudspeaker surround and is measured in N i s/m.
EBP
This parameter is equal to Fs divided by Qes. It is used in many formulas related to the design of loudspeaker cabinets, and in particular to determine which cabinet is better to choose for a given loudspeaker - a closed-back or a phase-reflex design. When the EBP value approaches 100, it means that the speaker is best suited for use in a bass reflex enclosure. If the EBP is close to 50, it is better to install this speaker in a closed enclosure. However, this rule is only a starting point when creating an acoustic system and allows exceptions.
Xmax/Xmech
The parameter defines the maximum linear deviation. The loudspeaker output becomes non-linear when the voice coil begins to move out of the magnetic gap. Although the suspension system can create non-linearity in the output signal, distortion begins to increase significantly at the moment when the number of turns of the voice coil in the magnetic gap begins to decrease. To determine Xmax, you need to calculate the length of the part of the voice coil that extends beyond the upper cut of the magnet and divide it in half. This parameter is used to determine the maximum sound pressure level (SPL) that a loudspeaker can provide while maintaining signal linearity, i.e. the normalized THD value.
When determining Xmech, the voice coil stroke length is measured until one of the following situations occurs: either the centering washer breaks, or the voice coil rests against the safety back cover, or the voice coil moves out of the magnetic gap, or other physical limitations of the cone begin to play a role. The smallest of the obtained coil stroke lengths is divided in half and the resulting value is taken as the maximum mechanical displacement of the diffuser.Sd
This parameter corresponds to the area of the working surface of the diffuser. Measured in cm2.
Zmax
This parameter corresponds to the impedance of the loudspeaker at the resonant frequency.
Usable frequency range
Manufacturers use different methods to measure the operating frequency range. Many methods are considered acceptable, but they lead to different results. As the frequency increases, the off-axis radiation from a loudspeaker decreases in proportion to the diameter. At a certain point it becomes sharply directed. The table shows the dependence of the frequency at which this effect occurs on the size of the loudspeaker.
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Rated power (Power handling)
This is a very important parameter when choosing a speaker. It is necessary to know for sure that the emitter will withstand the power of the signal supplied to it. Therefore, you need to choose a loudspeaker that can withstand the power supplied to it with a reserve. The determining criterion for how much power a loudspeaker will have is its ability to dissipate heat. The main design features that influence effective heat dissipation are voice coil size, magnet size, design ventilation, and the high-tech, advanced materials used in the voice coil design. The larger voice coil and magnet provide more efficient heat dissipation, and ventilation keeps the design cool.
When calculating the power of a loudspeaker, in addition to its ability to withstand heat, the mechanical properties of the loudspeaker are also important. After all, the device can withstand the heating that occurs when a power of 1 kW is supplied, but even before reaching this value it will fail due to structural damage: the voice coil will rest against the back wall or the voice coil will come out of the magnetic gap, the diffuser will be deformed, etc. d. Most often, such breakdowns occur when playing too powerful a low-frequency signal at high volume. To avoid breakdowns, you need to know the real range of reproduced frequencies, the Xmech parameter, as well as the rated power.Sensitivity
This parameter is one of the most important in the entire loudspeaker specification. It allows you to understand how efficiently and at what volume the device will reproduce sound when a signal of one or another power is supplied. Unfortunately, loudspeaker manufacturers use different methods to calculate this parameter - there is no single established one. When determining sensitivity, the sound pressure level is measured at a distance of one meter when a power of 1 W is applied to the loudspeaker. The problem is that sometimes the 1m distance is calculated from the dust cap, and sometimes from the speaker hanger. Because of this, determining the sensitivity of speakers can be quite difficult.
Taken from
The characteristics of a modern car are not only the technical aspects of the vehicle, but also attributes, which mean, for example, speakers. It's hard to imagine car trips without musical accompaniment. At the same time, sound quality comes to the fore, which is only possible with the “right” speakers. To acquire these, you need to know, if not everything, then a lot about them, so we will dwell on the criteria for choosing these acoustic devices.
Kinds
Depending on the type, acoustics are divided into coaxial and component. In the first case, ease of installation and cost savings are ensured, since such systems have a lower price, and in the second, higher sound quality is achieved.
- Coaxial acoustics - all speakers are enclosed in one housing. There are several such speakers, and they differ in their individual sound from a technical point of view. Coaxial acoustics are classified based on how many subbands there are. Each subrange is a separate speaker. Smaller speakers are placed directly in front of the larger diffuser.
- Component acoustics – all speakers are separate devices, the installation of which is not limited to one housing. The sound quality of such a system depends on how the speakers are positioned to design the acoustics. As a result, you can achieve almost perfect sound if the layout is implemented optimally. Performing this task is somewhat problematic, since the formation of a sound series is based on several frequencies. The cost of these systems is higher, but such expenses are justified.
Coaxial acoustics are losing their admirers, as car enthusiasts put sound quality first, which only component audio systems can provide. This is possible due to speakers that differ in sound frequencies. For example, the mid and low ranges are midbass, and the high ranges are tweeters. In a number of systems you can see that they are equipped with speakers (one or two), distinguished by larger cymbals. Their purpose is low frequencies.
Price
It is not an indisputable fact that only expensive acoustics guarantee high-quality sound. In some cases, high fees are charged for the brand. An alternative to an expensive system can be individual speakers at an affordable price, characterized by quite acceptable characteristics. The lower price threshold for coaxial acoustics with satisfactory parameters is 1,500 rubles. If you want to get truly high-quality sound, then you need to tune in to the price tag of 5,000 rubles.
Attention! To eliminate unnecessary expenses, you need to select speakers that suit your car radio. Pay attention to its standard holes, oriented towards connecting speakers.
Component acoustics cheaper than 3,000 rubles should not be considered as a possible purchase option. High-quality systems cannot cost less than 5,000–7,000 rubles. When choosing individual speakers, keep in mind that there are savings to be had. Two speakers with satisfactory sound can cost 2,000 rubles. For more powerful samples of such products you will have to pay much more.
Costs for high-end equipment usually fall within the range of 20–30 thousand rubles. Such systems can satisfy the needs of most car enthusiasts. Those who strive for maximum sound quality and are willing to incur corresponding expenses should focus on professional systems with a price tag of 40 thousand rubles.
Size
They all differ in size, which is very important in terms of acoustic design. You should not choose speakers that are smaller than 16 cm. Otherwise, you will not be able to achieve acceptable sound quality in the low and mid-frequency ranges. In relation to high-frequency frequencies, this recommendation should not be followed.
Attention! In order for the sound at low frequencies to acquire bass depth, speakers of considerable size are required.
If you are not going to use a subwoofer, then it is advisable to ensure that the front acoustics correspond to a size of 16–17 cm. The presence of a subwoofer can reduce the permissible parameters to 13 cm without loss of sound quality.
Power, resonant frequency and sensitivity
Power is an important indicator of speakers, which must be selected taking into account the capabilities of the radio. The power of the latter should be slightly lower at the output compared to what the speakers are capable of.
The resonant frequency, characterized by low rates, contributes to the depth of the bass. It is optimal if its value is from 60 to 75 Hz.
When a column is highly sensitive, this has certain advantages. One of these advantages is the ability to abandon the amplifier, which reduces the cost of the system as a whole.
Acoustic design
An important point that is directly related to sound quality. A general classification is provided, implying acoustic design, defined as loaded or unloaded.
In the first case, the presence of a rigid suspension and air that provides resistance leads to the fact that the diffuser is limited in its vibrations. In relation to the second classification, this is achieved solely due to the rigidity of the suspension.
In this case, systems are divided into single and double, where the former provide one-way sound radiation, and the latter – two-way. Manufacturers of car acoustics largely focus on only a few acoustic design options that are popular among car enthusiasts.
Acoustic design of the “closed box” type has become widespread. The principle here is this: a body made of sound-absorbing material and a hole in it that connects the air inside and outside. It contains a so-called free speaker, the body of which acts as a huge screen.
Location
Building a sound system within a limited space, which is the interior of a vehicle, does not look like a simple process. If at home you can simply move the speakers to the sides, then this will not work here. The speakers in the car must be installed correctly. Only compliance with a certain installation scheme and rules can lead to truly high-quality sound.
The basic rules for installing acoustics are as follows:
- the speakers should be placed as far forward as possible;
- To obtain a consistent sound, speakers with different frequencies must be installed in close proximity to each other.
Almost all cars have special places for installing speakers:
- doors – high frequency;
- rear of the car – midbass.
The most common scheme is when the speakers are installed at the rear. If this is the case, then you should separate the subwoofer and speakers at a sufficient distance. The optimal implementation of such a scheme is when the speakers are placed in the rear doors, and the subwoofer in the trunk. The front of the car is suitable for installing mid- and high-frequency speakers. For example, a suitable place for such speakers is close to the mirrors.
In any case, the operation of powerful acoustics contributes to the generation of extraneous noise as a result of the rattling of doors. This situation can be corrected by carrying out vibration and sound insulation work. If you do all this to the maximum, then not only will unnecessary noise in the cabin disappear, but the sound will also gain depth. Carrying out such a procedure requires high-quality materials, and this is expensive.
At the same time, even partial insulation of doors against excess noise with an addition such as wooden rings allows you to save money. You can install inexpensive speakers and get sound comparable to that produced by expensive acoustic models installed in standard places.
The installation of acoustics in a car is usually initiated by the driver himself. It is he who is the main listener, which forces him to position the speakers taking into account his location in the cabin. To do this, mid- and high-frequency speakers should be placed not just in front, but at the greatest distance from the listener. This allows you to make a podium mounted on the dashboard.
Attention! The required soundstage width is achieved when the tweeters on the front pillar are positioned at a certain angle. Usually they are directed at each other.
When the speakers are located throughout the car, the sound they produce reaches the driver's ears at different times. To avoid this, a temporary correction is required. It is provided through the appropriate processor, which is equipped with the radio or is installed separately. The sound quality in no way depends on the processor itself. It only gives the opportunity to evaluate its quality to someone who physically cannot be in the center in relation to the speakers.
Which speakers are the best?
To determine the best speakers, they will need to be nominated depending on the type.
Coaxial
- Pioneer TS-1339 - a large number of car enthusiasts recognize these speakers as the best. Their size is 13 cm, which allows you to install the speakers in specially designated places. They produce clear sound and correct bass, transmitted without distortion. If your sound requirements are not very picky, then these speakers are the best choice, as they have an affordable price and acceptable characteristics.
- Morel Tempo Coax 6 – the ability to create a two-way system with unique sound quality. Sound comfort is achieved by turning the “tweeter” by 20 degrees. The soft dome of the tweeter and its low resonance level are the conditions for reproducing frequencies over a wide range. The positive aspects of this system include power, as well as optimal sound balance and the fact that there is virtually no distortion. At the same time, low frequencies lack the so-called velvety sound.
- The JBL GTO-938 delivers serious sound power as a hallmark of these speakers, which also feature high sensitivity. They have an oval shape, which contributes to a stylish design. They are distinguished by balanced frequencies (high and low).
Component
- Morel Tempo 6 is a full-fledged acoustic system, characterized by high technical parameters and high-level assembly. Its configuration includes 2 tweeters, 2 crossovers, main speakers and a bonus in the form of an additional bowl. Highly detailed sound.
- Focal Performance PS 165 is a phenomenal sounding system that guarantees balanced, rich sound. Suitable for use as front speakers. This brand produces truly high-quality speakers that can satisfy the needs of even inveterate skeptics.
- Mystery MJ 105BX is one of the best speakers among its kind. Affordable price, high technical characteristics and excellent sound. The advantages of this cabinet speaker include its compactness and ease of installation.
Conclusion
Before you go shopping for car speakers, you need to answer a couple of questions for yourself:
- what type of sound system is needed?
- What is the maximum allowable size of acoustic elements?
The answer to the first question determines the sound quality, and the second - the possibility of installing the system.
If you are interested in high-quality and clear sound, it is not always provided only by expensive speaker systems. Some models of budget acoustics sound quite decent. In terms of powerful and flawless sound, it is expensive but worth it.
Also, the quality of the acoustic design will depend on where exactly you install the speakers, but here you will have to experiment.
Video
Speaker for car radio
Probably, many car owners were interested in how to choose speakers for their car radio. Making a smart choice is not so difficult if you know certain rules.
Speakers for car radios are selected in accordance with the main factors that must be taken into account. They and much more will be discussed in the article.
Main factors influencing the quality of speakers
What does everyone want when considering purchasing speakers? Of course, to achieve powerful and, most importantly, clear sound in your salon.
Naturally, the quality of the speakers alone will not be enough for this, because many factors influence surround sound, but still. High-quality speakers, selected wisely and in accordance with the rules, are the basis.
So, in order to get clear and spacious sound, you should take into account at least these main factors:
- location of speakers in the car;
- high-quality noise and vibration insulation;
- and much more.
Column types
The first question that will be asked to a buyer in an acoustics store will be the following: which speakers do you prefer to purchase, coaxial or component?
Coaxial speakers
Component speakers are a device where high-frequency speakers are located separately from mid-range and low-frequency speakers. These are already completely professional speakers that allow you to parse a melody into its components and enjoy the music to its fullest.
Note. Even an inexperienced person who listens to music through these speakers will be able to recognize the playing of individual musical instruments, everything is so effectively thought out in them. Needless to say, the sound quality in these speakers is much higher than in coaxial ones, but they also cost much more.
Component speakers are designed to reproduce sound within a specific frequency range. The sound quality is always up to par with these speakers, and the speakers must be installed according to the following guidelines.
So:
- If the speakers selected are small, then they reproduce only high frequencies (this is described in detail below). For this reason, you should try to place them so that the sound goes directly to the driver or passenger.
If you can mount them on the front panel or on a rack, that would be ideal. - You can’t install larger speakers in front (although this is possible), but they reproduce mid and low frequencies. They can be easily installed in the car doors or behind them, directly on the glass shelf.
In principle, there is no difference in the placement of large speakers.
Speaker size
Of course, this is the second most important question that a store salesperson will ask. It is usually not possible to install huge dimensions in a car, and every owner should remember this.
In addition, if you purchase speakers larger than the standard ones intended for this car by the manufacturer, who has prepared a place for them in advance, you will have to make modifications.
Note. You need to know that speakers measuring 10-13 cm (4-5 inches) diagonally are capable of reproducing only high frequencies. But speakers measuring 16-17 cm (6-6.5 inches) diagonally reproduce low frequencies in addition.
We can say that this is the main difference in size. The speakers are large, and in any case they will reproduce sound better, but this is not an axiom.
Power
This is probably the most important parameter for amateurs who imagine that they understand music. But we hasten to disappoint them.
It turns out that the power of the speakers in itself cannot act as a quality characteristic. There is even a rule according to which this very power must be selected, otherwise you cannot expect clear sound.
So, according to the rules, the power parameter should not be less than the power of the car radio. This is already an axiom that you can’t argue with.
Loss of sound quality and much more is the result of incorrect selection of speaker power. On the other hand, the power of the speakers should not significantly exceed the parameters of the car radio, as this will also not lead to anything good.
Power, as such, is usually divided into:
- rated power;
- maximum power;
- peak power.
The smallest of the three is, naturally, the rated power, but it is also the most correct. Some unscrupulous manufacturers, in order to attract clientele, indicate maximum or peak power in the passport data.
In reality, a competent buyer who knows about the rated power should look for its value in that data, as the determining and only correct one.
Note. It is the rated power that determines the limits within which you can listen to music loudly and for a long time.
It is not uncommon for a speaker with a lower power rating to be able to produce the same sound level as a more powerful speaker (provided its sensitivity is higher).
Power cannot act as the only criterion for high-quality sound, because you can improve the performance in another way: by installing a speaker system with a resistance of 2.5-3.5 Ohms. In addition, the amplifier, which must be adapted to the power, is of great importance, otherwise it will not be possible to avoid the imminent failure of the equipment, no matter how expensive it is.
Acoustic design
This is one of the important factors affecting sound reproduction. There are many varieties of acoustic design, but it is customary to divide it into two main ones: unloaded and loaded.
Note. Unloaded design implies limiting the vibrations of the diffuser by the rigidity of the suspension. As for the loaded design, it implies limiting vibrations not only by the rigidity of the suspension, but also by radiation resistance.
In addition, it is customary to divide acoustic design into single- and double-acting systems. The first is characterized by sound emission from only one side of the diffusers, and the second - from both sides.
Now let's look at the most popular types of acoustic design:
- A “closed box” is a speaker housing that is covered with sound-absorbing components that effectively dampen waves.
- This type of acoustic design is ideal for those music lovers who put high-quality playback first, or, in other words, so that there is a slight loss of sound pressure and all this is compensated by the simplicity and small size of the speaker.
A bass reflex is a housing in which a special hole is made. It is responsible for the connection between external and internal air.
- Ideal for music lovers who prefer to listen to sound in two blocks at the same time.
Free acoustic design, implying the use of a large body acting as a screen.
Other factors
In addition to the types of speakers we have analyzed, their sizes and power, there are other factors that many perceive as trifles.
- Sensivity – or the input sensitivity of the speakers. The higher this parameter is, the better.
Again, not everything is so simple here and in order not to confuse anything, we remember that the recommended indicator of this sensitivity should be within 92.
- FS is already a resonant purity of reproduction, which also acts as a separate factor influencing the sound. The lower the value, the better and the speakers will be able to produce deeper bass.
The normal and recommended value in this case is the limit of 60-75. - The range of reproduced frequencies is an indicator that indicates frequency boundaries. Recommended value is +/- 3 dB.
- QTS – or sound quality factor. This factor must also be carefully paid attention to.
The fact is that if the speakers are installed in the car door (which is fashionable today), then the Q value of the speakers should exceed 0.6. Otherwise, there can be no talk of any sound quality.
Note. Normal correct sound should reach the person in front. This is a law of physics, but there is no such option in a car to install speakers in front.
Some owners, however, manage to do this by making fundamental design changes, modifying the pillars and dashboard, but not everyone can afford it. In this regard, the sound from the speakers installed in the door will come from the side and to the feet.
Therefore, the quality factor must be assessed correctly.
Conclusion
At the end of our article, I would like to provide a list, or rather an algorithm of actions, that will be most correct when choosing.
So:
- We determine the structure of the speakers based on the installation method and the number of sound reproduction bands.
- We select speakers in accordance with technical standards (rated power, amplifier matching, etc.).
- We do not forget to take into account the correct size of the speakers, remembering that there are standard sizes.
- We select the speaker manufacturer recommended by the car manufacturer.
- We determine the type of acoustic design.
Instructions on how to install speakers directly into a car with your own hands can be easily downloaded online. Photos and video materials will be useful during the work process.
The price of speakers varies and it all depends on the specific model, size and technical capabilities.
So I decided to write an article myself, which is very important for acousticians. In this article I want to describe ways to measure the most important parameters of dynamic heads - the Thiel-Small parameters.
Remember! The technique below is only effective for measuring the Thiel-Small parameters of speakers with resonant frequencies below 100 Hz (i.e. woofers), the error increases at higher frequencies.
The most basic parameters Tilya-Smolla, by which it is possible to calculate and produce an acoustic design (in other words, a box) are:
- Speaker resonant frequency F s (Hertz)
- Equivalent volume V as (liters or cubic feet)
- Total quality factor Q ts
- DC resistance R e (Ohm)
For a more serious approach, you will also need to know:
- Mechanical quality factor Q ms
- Electrical quality factor Q es
- Diffuser area S d (m 2) or its diameter Dia (cm)
- Sensitivity SPL (dB)
- Inductance L e (Henry)
- Impedance Z (Ohm)
- Peak power Pe (Watt)
- Mass of the moving system M ms (g)
- Relative stiffness (mechanical flexibility) C ms (meters/newton)
- Mechanical resistance R ms (kg/sec)
- Motor power (product of induction in the magnetic gap by the length of the voice coil wire) BL (Tesla*m)
Most of these parameters can be measured or calculated at home using not particularly sophisticated measuring instruments and a computer or calculator that can extract roots and exponentiate. For an even more serious approach to designing acoustic design and taking into account the characteristics of speakers, I recommend reading more serious literature. The author of this “work” does not claim any special knowledge in the field of theory, and everything stated here is a compilation from various sources - both foreign and Russian.
Measurement of Thiel-Small parameters R e, F s, F c, Q es, Q ms, Q ts, Q tc, V as, C ms, S d, M ms.
To measure these parameters you will need the following equipment:
- Voltmeter
- Audio frequency signal generator. Generator programs that generate the necessary frequencies are suitable. Like Marchand Function Generator or NCH tone generator. Since it is not always possible to find a frequency meter at home, you can completely trust these programs and your sound card installed on your computer.
- Powerful (at least 5 watts) resistor with a resistance of 1000 ohms
- Accurate (+- 1%) 10 ohm resistor
- Wires, clamps and other rubbish to connect it all into a single circuit.
Measuring circuit
Calibration:
First you need to calibrate the voltmeter. To do this, instead of the speaker, a resistance of 10 Ohms is connected and by selecting the voltage supplied by the generator, it is necessary to achieve a voltage of 0.01 volts. If the resistor is of a different value, then the voltage should correspond to 1/1000 of the resistance value in Ohms. For example, for a 4 ohm calibration resistance, the voltage should be 0.004 volts. Remember! After calibration, the generator output voltage cannot be adjusted until all measurements are completed.
Finding R e
Now, by connecting a speaker instead of a calibration resistance and setting the frequency on the generator to close to 0 hertz, we can determine its resistance to direct current Re. It will be the voltmeter reading multiplied by 1000. However, Re can be measured directly with an ohmmeter.
Finding Fs and Rmax
The speaker during this and all subsequent measurements must be in free space. The resonant frequency of a speaker is found at the peak of its impedance (Z-characteristic). To find it, smoothly change the frequency of the generator and look at the voltmeter readings. The frequency at which the voltage on the voltmeter will be maximum (a further change in frequency will lead to a voltage drop) will be the main resonance frequency for this speaker. For speakers with a diameter greater than 16cm, this frequency should be below 100Hz. Don't forget to record not only the frequency, but also the voltmeter readings. Multiplied by 1000, they will give the speaker resistance at the resonant frequency Rmax, necessary for calculating other parameters.
Finding Q ms , Q es and Q ts
These parameters are found using the following formulas: 
As you can see, this is a sequential finding of additional parameters R o, R x and measurement of previously unknown frequencies F 1 and F 2. These are the frequencies at which the speaker impedance is equal to Rx. Since Rx is always less than Rmax, there will be two frequencies - one is slightly less than Fs, and the other is slightly more. You can check the accuracy of your measurements with the following formula:
If the calculated result differs from the previously found one by more than 1 hertz, then you need to repeat everything all over again and more carefully. So, we have found and calculated several basic parameters and can draw some conclusions based on them:
- If the resonant frequency of the speaker is above 50Hz, then it has the right to claim to work, at best, as a midbass. You can immediately forget about the subwoofer on such a speaker.
- If the resonant frequency of the speaker is above 100Hz, then it is not a woofer at all. You can use it to reproduce mid frequencies in three-way systems.
- If the F s /Q ts ratio of a speaker is less than 50, then this speaker is intended to operate exclusively in closed boxes. If more than 100 - exclusively for working with a bass reflex or in bandpasses. If the value is between 50 and 100, then you need to carefully look at other parameters - what type of acoustic design the speaker gravitates towards. It is best to use special computer programs for this that can graphically simulate the acoustic output of such a speaker in different acoustic designs. True, one cannot do without other, no less important parameters - V as, S d, C ms and L.
Finding Sd
This is the so-called effective radiating surface of the diffuser. For the lowest frequencies (in the zone of piston action) it coincides with the design one and is equal to:
The radius R in this case will be half the distance from the middle of the width of the rubber suspension on one side to the middle of the rubber suspension on the opposite side. This is due to the fact that half the width of the rubber suspension is also a radiating surface. Please note that the unit of measurement for this area is square meters. Accordingly, the radius must be substituted into it in meters.
Finding the inductance of the speaker coil L
To do this, you need the results of one of the readings from the very first test. You will need an impedance (impedance) of the voice coil at a frequency of about 1000 Hz. Since the reactive component (X L) is separated from the active R e by an angle of 900, we can use the Pythagorean theorem:
Since Z (coil impedance at a certain frequency) and R e (coil DC resistance) are known, the formula converts to:
Having found the reactance X L at frequency F, you can calculate the inductance itself using the formula:
V as measurements
There are several ways to measure equivalent volume, but at home it is easier to use two: the “additional mass” method and the “additional volume” method. The first of them requires several weights of known weight from materials. You can use a set of weights from pharmacy scales or use old copper coins of 1,2,3 and 5 kopecks, since the weight of such a coin in grams corresponds to the face value. The second method requires a sealed box of a known volume with a corresponding hole for the speaker.(mospagebreak)
Finding V as using the added mass method
First you need to evenly load the diffuser with weights and measure its resonant frequency again, writing it down as F" s. It should be lower than F s. It is better if the new resonant frequency is 30% -50% less. The weight of the weights is approximately 10 grams for every inch of diffuser diameter. That is, for a 12" head you need a weight weighing about 120 grams.
where M is the mass of added weights in kilograms.
Based on the results obtained, V as (m 3) is calculated using the formula:
Finding V as by the additional volume method
It is necessary to seal the speaker in the measuring box. It is best to do this with the magnet facing out, since the speaker does not care which side it has volume on, and it will be easier for you to connect the wires. And there are fewer extra holes. The volume of the box is designated as V b.
Then you need to measure Fc (the resonant frequency of the speaker in a closed box) and, accordingly, calculate Q mc, Q ec and Q tc. The measurement technique is completely similar to that described above. Then the equivalent volume is found using the formula:
The data obtained as a result of all these measurements is sufficient for further calculation of the acoustic design of a low-frequency link of a sufficiently high class. But how it is calculated is a completely different story.
Determination of mechanical flexibility C ms
Where S d is the effective area of the diffuser with a nominal diameter D. How to calculate is written earlier.
Determination of the mass of the mobile system Mms
It is easily calculated using the formula:
Motor power (product of induction in the magnetic gap and the length of the voice coil wire) BL
Most importantly, do not forget that for more accurate measurement values of the Thiel-Small parameters, it is necessary to conduct the experiment several times, and then obtain more accurate values by averaging.
