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Old 04-09-2015, 06:17 AM
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Default Thiele Small Parameters.....

It seems as though these parameters are completely meaningless to a large majority of people now...

So, why would so many speaker manufacturers (99% of them) give out meaningless parameters? Doesn't make sense in my head, because they aren't meaningless... But, a lot of people seem to think otherwise and it seems as though NO ONE (in the car audio world)models out their subwoofers with a modeling program and the TSP's provided by the subwoofer manufacturer...

So, why would I be griping about this? Well, mainly because I see a lot of people (almost everyone) here, posting threads asking how this speaker would respond in box A or in box B (just an example) for X # of speakers, and X amount of power... ANYONE should be able to do this themselves, with a little 5th grade math, and some patience...

So, what is Thiele Small Parameters? Well, a quick google search, quickly finds quite a few explanations.

http://www.hometheatershack.com/foru...arameters.html

Page Title

Measuring Loudspeaker Driver Parameters

Now, for a program.. Here is a list of FREE programs, that you can use to model out your speaker.

WinISD- LinearTeam

Unibox- UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard (Requires Excel)

Speakerbuilding.com- This site has several different programs available.
SpeakerBuilding.com - Software

Micka- Loudspeaker enclosure calculating with Thiele Small parameter (This one is all done online... you don't even have to download anything, but it is limited in comparison to these other programs.

Now... This should allow you to get the general "idea", if you are wanting to see how a speaker responds, in certain enclosures... Hopefully, this can be helpful.. Let me know what you guys think, I'd love to hear other peoples input.

Last edited by nissanbasshead; 04-09-2015 at 06:28 AM.
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Old 04-09-2015, 06:19 AM
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"Thiele/Small" commonly refers to a set of electromechanical parameters that define how a loudspeaker driver performs. They are useful when designing speakers because they are more easily determined experimentally than more fundamental mechanical parameters. They are named after A. N. Thiele of the Australian Broadcasting Commission, and Richard H. Small of the University of Sydney, who pioneered this line of analysis for loudspeakers.

Fundamental small signal mechanical parameters...

These are the physical parameters of a loudspeaker driver, as measured at small signal levels, used in the equivalent electrical circuit models. Some of these values are neither easy nor convenient to measure in a finished loudspeaker driver, so when designing speakers using existing drive units (which is almost always the case), the more easily measured parameters listed under Small Signal Parameters are more practical.
Sd - Projected area of the driver diaphragm, in square metres.
Mms - Mass of the diaphragm, including acoustic load, in kilograms.
Cms - Compliance of the driver's suspension, in metres per newton (the reciprocal of its 'stiffness').
Rms - The mechanical resistance of a driver's suspension (ie, 'lossiness') in Ns/m
Le - Voice coil inductance measured in millihenries (mH).
Re - DC resistance of the voice coil, measured in ohms.
Bl - The product of magnet field strength in the voice coil gap and the length of wire in the magnetic field, in Tm (teslametres).
Large signal parameters...

These parameters are useful for predicting the approximate output of a driver at high input levels.
Xmax - Maximum linear peak (or sometimes peak-to-peak) excursion (in mm) of the cone. Note that, because of mechanical issues, the motion of a driver cone becomes non-linear with large enough inputs, ie those in excess of this parameter.
Xmech - Maximum physical excursion of the driver before physical damage. With a sufficiently large input, the voice coil and cone will cause voice coil damage or to some mechanical part of the driver.
Pe - Thermal power handling capacity of the driver, in watts. This value is difficult to characterize and is often overestimated, by manufacturers and others.
Vd - Peak displacement volume, calculated by Vd = SdXmax
Descriptions...

Fs
Also called F0, measured in hertz (Hz). The frequency at which the combination of the moving mass and suspension compliance maximally reinforces cone motion. A more compliant suspension or a larger moving mass will cause a lower resonance frequency, and vice versa. Usually it is less efficient to produce output at frequencies below Fs, though motion below Fs can cause uncontrolled motion, mechanically endangering the driver. Woofers typically have an Fs in the range of 13–60 Hz. Midranges usually have an Fs in the range of 60–500 Hz and tweeters between 500 Hz and 4 kHz.


Qts
A unitless measurement, characterizing the combined electric and mechanical damping of the driver. In electronics, Q is the inverse of the damping ratio. The value of Qts is proportional to the energy stored, divided by the energy dissipated, and is defined at resonance (Fs). Most drivers have Qts values between 0.2 and 0.8.


Qms
A unitless measurement, characterizing the mechanical damping of the driver, that is, the losses in the suspension (surround and spider.) A typical value is around 3. High Qms indicates lower damping losses, and low Qms indicates higher. The main effect of Qms is on the impedance of the driver, with high Qms drivers displaying a higher impedance peak. One predictor for low Qms is a metallic voice coil former of a particular configuration. These act as eddy-current brakes and increase damping, reducing Qms. The same former, with an electrical break in the cylinder (so no conducting loop) avoids these losses.


Qes
A unitless measurement, describing the electrical damping of the loudspeaker. As the coil of wire moves through the magnetic field, it generates a current which opposes the motion of the coil. This so-called "Back-EMF" decreases the total current through the coil near the resonance frequency, reducing cone movement and increasing impedance. In most drivers, Qes is the dominant factor in the voice coil damping.


Bl
Measured in tesla-metres (Tm). Technically this is B x l (vector cross product or B * l * sin(θ)), but the standard geometry of a circular coil in an annular voice coil gap gives sin(θ)=1. Bl is also known as the 'force factor' because the force on the coil imposed by the magnet is Bl multiplied by the current through the coil. The higher the Bl value, the larger the force generated by a given current flowing through the voice coil. Bl has a very strong effect on Qes.


Vas
Measured in litres (L), is a measure of the free air 'stiffness' of the suspension -- the driver must be mounted in free air. It represents the volume of air that has the same stiffness as the driver's suspension when acted on by a piston of the same area (Sd) as the cone. Larger values mean lower stiffness, and generally require larger enclosures. Vas varies with the square of the diameter.


Mms
Measured in grams (g), this is the mass of the cone, coil and other moving parts of a driver, including the acoustic load imposed by the air in contact with the driver cone. Mmd is the cone mass without the acoustic load, and the two should not be confused. Some simulation software calculates Mms when Mmd is entered.


Rms
Units are not usually given for this parameter, but it is in mechanical 'ohms'. Rms is a measurement of the losses, or damping, in a driver's suspension and moving system. It is the main factor in determining Qms. Rms is influenced by suspension topology, materials, and by the voice coil former (bobbin) material.


Cms
Measured in metres per Newton (m/N). Describes the compliance (ie, the inverse of stiffness) of the suspension. The more compliant a suspension system is, the lower its stiffness, so the higher the Vas will be.


Re
Measured in ohms (Ω), this is the DC resistance of the voice coil. American EIA standard RS-299A specifies that DCR should be at least 80% of the rated driver impedance, so an 8-ohm rated driver will have a DC resistance of at least 6.4 ohms, and a 4-ohm unit should measure 3.2 ohms minimum. Advertised values are often approximate at best.


Le
Measured in millihenries (mH), this is the inductance of the voice coil. The coil is an inductor in part due to losses in the pole piece, so the apparent inductance changes with frequency. Large Le values limit the high frequency output of the driver and cause response changes near cutoff. Simple modeling software often neglects the effects of Le, and so does not include its consequences. Building a copper cap into the magnet structure can reduce this effect.


Sd
Measured in square metres (m). The effective area of the cone or diaphragm. It varies with the conformation of the cone, and details of the surround. Generally accepted as the cone body diameter plus half the width of the annulus (surround). Wide roll surrounds can have significantly less Sd than conventional types.


Xmax
Specified in millimeters (mm). In the simplest form, subtract the height of the voice coil winding from the height of the magnetic gap, take the absolute value and divide by 2. This technique was suggested by JBL's Mark Gander in a 1981 AES paper, as an indicator of a loudspeaker motor's linear range. Although easily determined, it neglects non-linearities and limitations introduced by the suspension. Subsequently, a combined mechanical/acoustical measure was suggested, in which a driver is progressively driven to high levels at low frequencies, with Xmax determined at 10% THD. This method better represents actual driver performance, but is harder and more time-consuming to determine.


Vd
Specified in litres (L). The volume displaced by the cone, equal to the cone area (Sd) multiplied by Xmax. Any particular value may be achieved in any of several ways. For instance, by having a small cone with a large Xmax, or a large cone with a small Xmax. Comparing Vd values will give an indication of the maximum output of a driver at low frequencies. High Xmax, small cone diameter drivers are likely to be inefficient, since much of the voice coil winding will be outside the magnetic gap at any one time and will therefore contribute little or nothing to cone motion. Likewise, large cone diameter high Xmax drivers are likely to be more efficient as they will not need, and so may not have, long voice coils.

η0
Specified in percent (%). Comparing drivers by their reference efficiency is more useful than using 'sensitivity' since manufacturer sensitivity figures are too often overly optimistic.


Referenced link. TS Parameters (Thiele/Small Parameters) - Home Theater Forum and Systems - HomeTheaterShack.com
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Old 04-09-2015, 06:49 AM
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Nice informational thread.
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Old 04-09-2015, 07:50 AM
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Good info indeed. To answer your question in the 1st post, few sentences, a lot of people are looking for those who have exp with the speaker(s) and seeking best overall performance out of it/them and/or for an all out SPL burp vehicle or maybe just a daily ground pounder.

Who knows. Lazyness? Perhaps...

I've also seen some people ask for an enclosure to an obselete sub...that isn't made anymore and looking for t/s parameters hoping somebody on here has them as well as any type of enclosure recommendation.

Can't wait for Jake's response tho...
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Old 04-09-2015, 08:17 AM
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Quote:
Originally Posted by Boomintahoe View Post
Good info indeed. To answer your question in the 1st post, few sentences, a lot of people are looking for those who have exp with the speaker(s) and seeking best overall performance out of it/them and/or for an all out SPL burp vehicle or maybe just a daily ground pounder.

Who knows. Lazyness? Perhaps...

I've also seen some people ask for an enclosure to an obselete sub...that isn't made anymore and looking for t/s parameters hoping somebody on here has them as well as any type of enclosure recommendation.

Can't wait for Jake's response tho...
If you can't get TSP's for a driver, I recommend getting a parameter puller, like this one Dayton Audio DATS V2 Audio Test System. It's only $100 and that is well worth it, if you are are an audio enthusiast and do a lot of testing and installing (which most people on this forum do quite a bit of that), then this would definitely be a useful tool to test parameters on drivers.
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Old 04-09-2015, 08:45 AM
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I agree with the OP. Alot of people either dont understand the difference it will make when using the tsp, or people are misled from other. I met a quite of few people who dont use them and say because they know what work and what doesnt work. And people fellow that bs because he has 5 or more trophies and or burp 150db. It some crazy shit i saw on my local car audio facebook page.

What came first the subwoofer or design? Tell them before there was a sub there a was a design and those tsp mean alot. Its a science not some kinda throw your own box together and be happy with the outcome
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Old 04-09-2015, 08:53 AM
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It's not that car audio guys negate t/s parameters from their build due to laziness, cabin gain in a vehicle is far from linear. Spend all the time to produce a flat response in a given enclosure to find it peaking at the Fs of the cabin. I gave up on flat response and typically build as big as possible With an aero port to adjust tuning. Taylor the sound to my liking in the real world situation over the theoretical response given by a simulation program.
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Old 04-09-2015, 08:59 AM
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Quote:
Originally Posted by lunchbox View Post
It's not that car audio guys negate t/s parameters from their build due to laziness, cabin gain in a vehicle is far from linear. Spend all the time to produce a flat response in a given enclosure to find it peaking at the Fs of the cabin. I gave up on flat response and typically build as big as possible With an aero port to adjust tuning. Taylor the sound to my liking in the real world situation over the theoretical response given by a simulation program.
TSP's are not used to calculate cabin gain... They are there so that you can see how the driver responds in a specific enclosure... You can also compare the output and response between several different enclosures for one driver... The general idea is to give you a "ballpark" for the output and response that you will get from a specific enclosure... If aiming for a flat response, and say for instance you design a speaker enclosure that gives an F3 cutoff of 30 hz with a flat response up to 120 hz... When you put that in your vehicle, home, etc., it will change the response due to cabin gain, as you stated. But, with a little equalization and proper tuning and setup, you can still achieve the response and output that you want for a specific environment.

Last edited by nissanbasshead; 04-09-2015 at 09:09 AM.
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Old 04-09-2015, 09:45 AM
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Quote:
Originally Posted by nissanbasshead View Post
TSP's are not used to calculate cabin gain... They are there so that you can see how the driver responds in a specific enclosure... You can also compare the output and response between several different enclosures for one driver... The general idea is to give you a "ballpark" for the output and response that you will get from a specific enclosure... If aiming for a flat response, and say for instance you design a speaker enclosure that gives an F3 cutoff of 30 hz with a flat response up to 120 hz... When you put that in your vehicle, home, etc., it will change the response due to cabin gain, as you stated. But, with a little equalization and proper tuning and setup, you can still achieve the response and output that you want for a specific environment.
Not sure how you got from what I said. I know t/s parameters are not for cabin gain. What I was trying to get across was that the effects of cabin gain will make the theoretical linear response none linear. I don't know anyone who plays 120hz through their subs in a ground pounder build. It really depends on the goals of the individual, not many people on caco are looking for SQ that's why you see SPL numbers as the bragging rights here. I wouldn't have 4 18's and 30kw if SQ was my goal, same goes for the majority of caco users. Check out SQ oriented forums and they are all about modeling response prior to building, not so much in the world of SPL where nothing makes any sense. Very few of us would attenuate a peak for the flatter response, we would meter that peak and brag about our score.
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Old 04-09-2015, 09:46 AM
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TS will tell you what it will do in a open air environment. Not what it will do in the cabin when you take into account cabin gain and loading.
Unless your software will tell you what it will do in every single install, dampening applied, port location, driver location, real world power. It is not useless but still not real world.
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