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Old 07-29-2006, 11:11 AM   #1
bassfreak

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T/S parameters

Explanation Of Audio Terms

* FS- is the free air resonance of the driver. this in its simplest form means the driver moves easiest and impedance is at its highest. so you get the most output with the least work.
* VAS- its the volume of air that has the same compliance as the suspension. compliance is the measure of the stifness of the air equal to the suspension. so a VAS of 3.5 cubes means that the suspension has the same stiffness as 3.5 cubic feet of air(imagine compression of that air as for stiffness).
* CMS- is how "stiff" the suspension is. this is the measure of the stiffness of the suspension in n/m usually at or close to rest, where the VAS is the measure of the elasticity of the suspension in cubic feet related to the air that is equal to its CMS. think about this in a tire. you have the same amount of space to fill, but you put 25PSI in the left tire and 40 PSI in the right tire(off the car) the left tire has about the same air space but the amount of air inside is lower so CMS is higher. while the 40 PSI tire very similar amount of space but the amount of compressed air inside is greater, so CMS is lower the result is the tire with the lower CMS and same VAS(amount of space) is a stiffer tire!.

* QES- is the electrical dampening of the driver. so in other words you pass a signal through the voice coil, and the lower QES (electromotive force) is somewhat "over controlling" while the higher QES tends to have less control when the signal is passed through. so the higher QES is less controling over the input or change of input. in its simplest form it can be described as how well the motor USES its input... both over and under damped alignments will have cons(doesn't return fast enought or returns too fast). above and below FS these parameters mean a great deal(QES and QMS)

* QMS- is the damping of the mechanical aspects of the driver. so the QMS is how it controls the cone movement when the woofer resonates. the higher the QMS the softer the suspension and it has less control over its resonance. The lower the QMS the more it opposes resonance because of being "over controlling".. so there for the lower the QMS the "stiffer" the suspension. basically both oppose resonance but opposes it because the suspension wants to "stop it" from its stiffness and one does NOT want to stop it because it has little to no control over its inertia...

* QTS- is the total Q before you has electrical and mechanical dampening losses so to say. its the raw driver dampening.

* RMS- is the losses of the suspension meaning that the stiffer the suspension with the same vas the higher the "losses".this can contribute to how much a drive is able to move in a certain box with a given power... softer suspensions will move easier...

* KMS- is the measure of how linear the suspensions stiffness remains through its excursion. the result of the suspension stiffness exceed 4X its CMS is defined as Xsus.

* Xmax- this spec is often over looked and very hyped. It is the measure of excursion of the motor in linear terms similar to KMS but for the electrical side of the driver. its defined as when the B/L drops to 71% of total B/L you have a QES that has doubled and its consider non linear.

* Xmag - is the measure of how far the motor can move the coil. this is limited to coil height and the gap's fringe field also power handling. some woofers may have a Xmag well beyond its coil height because of the flux fields outside the gap and extreme power handling(DD9515 for example) this is a good indicator of how strong the motors actual strength is beyond linear excursion. both the magnetic field and electromagnetic field from the coil.
* B - is the measure of the flux density in the gap. the less space between the gaps the more density you have. this is often complemented with a lower QTS.
* L - is equal to the length of the voice coil in the gap. so the longer the voice
the higher your L. so if you use a smaller gauge wire you can get more L, but you add more MMS. its a trade off adn there really is no better option only the one for the application...
* B/L - is both the B and the L combined.
* RE - is the at rest DC resistance. so when no voltage is applied and when the amp first turns on this the resistance the amp sees.
* Impedance - is the measure of the resistance of the voice coil when a AC signal is passed through. this varies as frequency varies and boxes/aligmetns vary.

* Pe - is the power handling of the woofer. its not thermal or mechanical but both. i think there should be both a thermal and mechanical spec but oh well.
* FB - is the tuning frequency of the alignment.
* F3 - is the -3 DB down point of the woofer, meaning that you are now relying on the mechanical dampening of the woofer instead of the dampening of the box and the woofer along with the port. in ported alignments you can hear anything under about -3 DB point, while the sealed boxes compliance stays much more linear so below this you can often hear it when you have the proper cabin gain.
* SD - is the measure of the woofers cone area. a lot of people use 1/3 of the surround but i don't like to use this for a few reasons. as it doesn't relate to the actual cones displacement as its not constant.
* BL^2/RE - this is to see how much B/L you have despite the RE rating. the lower the Re the less B/L you have so you can't compare a woofer rated with a B/L of 29@8 ohm and a woofer with a Re of 3.6 with a B/L of 22.

quick example. 9515 with dual 4ohm coils 29tm so.. 29^2/7.2-116
the 9515 with an RE of 1.8 per or series RE of 3.6 the BL is 21tm or 122.5
its important to look at this instead of B/L when comparing woofers with different RE's
also B/L is potential motor strength meaning its not actual, but it part of the actual strength. power handling and QES also indicate motor strength!
The voltage x amperage(power in watts) that is applied to the voice coil is important and equally important is how much is used(wasted as heat vs turned into electromotive force).

* MMS - referred to as the Moving mass of the speakers moving parts. its really simple but something that every good designer HAS to find a "balance" with among other parameters.
sometimes people ask when is too much? or how do you "balance" it. if anyone shows interest in this maybe we can have a discussion on this.
* KMS curves - its a simple graph of the suspension stiffness VS excursion! the flatter the better? not always! don't be fooled buy marketing and "ideal designs" because many designs aren't ideal for every application! another subject that can be dug into. questions!?
* BL curve - and what in the hell does this mean!? simply it is a estimate(small signal parameter) of how well the motor maintains QES, along with B/L which is potential motor strength. is flatter better? generally yes, but there are sacrifices that MUST be made!! something else i would like to discuss and is a very hot topic between many people.

Last edited by bassfreak; 04-19-2007 at 02:40 AM.
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Old 07-29-2006, 02:54 PM   #2
xxPunk0Ramaxx

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honestly, if you're going to take the time to do a write up on anything and hope to get any feedback, perhaps you should run it through a spell checker?
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Old 07-29-2006, 03:20 PM   #3
bassfreak

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Quote:
Originally Posted by xxPunk0Ramaxx
honestly, if you're going to take the time to do a write up on anything and hope to get any feedback, perhaps you should run it through a spell checker?
ok, done.
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Old 07-29-2006, 03:32 PM   #4
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Um, if you did type all this out, why didn't you simply just paste this link instead:

http://www.the12volt.com/caraudio/thiele.asp

Its useful info, but you really could have saved yourself some time with this link. Also, I think some of this stuff is in the STICKIES.
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Old 07-29-2006, 04:25 PM   #5
bassfreak

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Quote:
Originally Posted by PuffDaddy_d
Um, if you did type all this out, why didn't you simply just paste this link instead:

http://www.the12volt.com/caraudio/thiele.asp

Its useful info, but you really could have saved yourself some time with this link. Also, I think some of this stuff is in the STICKIES.
maybe a thank you? or maybe i wanted to type it up for the people who couldn't fine the other sources. hell i didn't find that one when i searched.

Last edited by bassfreak; 04-11-2007 at 03:06 PM.
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Old 07-29-2006, 04:53 PM   #6
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Quote:
Originally Posted by bassfreak
maybe a thank you? or maybe i wanted to type it up for the people who couldn't fine the other sorces. hell i didn't find that one when i searched.
you dont know how to google but you use a computer
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Old 07-29-2006, 05:09 PM   #7
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Quote:
Originally Posted by bassfreak
maybe a thank you? or maybe i wanted to type it up for the people who couldn't fine the other sorces. hell i didn't find that one when i searched.
http://en.wikipedia.org/wiki/Thiele/Small

http://sound.westhost.com/tsp.htm

http://yu-ra.tripod.com/ts_parameter.htm

http://www.silcom.com/~aludwig/Sysde...parameters.htm

http://www.speakerfactoryusa.com/glossary/index.html

http://www.diysubwoofers.org/definitions.htm

http://www.mmxpress.com/technical/terms.htm

http://www.faqs.org/faqs/car-audio/part3/

http://www.mhsoft.nl/TSP_ex.html

http://66.49.188.60/tsp_calc.html

http://hometheaterhifi.com/forum/showthread.php?p=10678

Great job on reinventing the wheel
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Old 07-29-2006, 10:18 PM   #9
bassfreak

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thank you that is a great list! just a few people have PMed me so i thought it would be of use to them.
systemtek- i srearched google and found a few links but i thought i would type them here so the people who asked could review with ease. plus it gives us a chance to go into more detail if any concerns or questions are brought up.
thewacokid could start by asking how CMS and compliance is affected by ported boxes above tuning so he don't recommend the wrong boxes.
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Old 07-30-2006, 04:20 PM   #10
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I haven't clicked any of those links in that list, but if they are like "all the others" out there, what they have are the textbook descriptions of what the specs are.
Blah, blah, blah.

I like to process information that I read through this filter:
"How can I take that to the store and use it to buy a loaf of bread?"


Those textbook definitions - they probably won't help you understand where one specs trades off in favor of another, they probably won't help you understand how to compare one sub against another in pursuit of ultimate "bang for the buck", and they probably won't help you understand how to build your enclosure, or determine the enclosure needs, or trade-offs of one sub compared to another...

And if you find yourself reading those "textbook" definitions, and not understanding how to apply them in a practical context - you'll still end up looking on the manufacturer's spec sheets right past the specs, down to the "manufacturer's recommended enclosures" section.

So, I wrote up a list of "what really matters" with T/S specs:
http://www.caraudiocentral.net/forum...ead.php?t=4005

(I thought I started a thread on this forum too... guess I didn't, probably was "too busy" that day or something. Maybe I should create a sticky in the Technical forum, for how often this question gets raised around here these days? )

I hope that helps with what I believe you are actually looking for.
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Old 07-30-2006, 04:25 PM   #11
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...otherwise, Bassfreak's write-up is very good, and does even avoid those sterile, impractical "textbook" definitions pretty well.

(just wanted to throw that in there )
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Old 07-30-2006, 06:31 PM   #12
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Quote:
Originally Posted by geolemon
(I thought I started a thread on this forum too... guess I didn't, probably was "too busy" that day or something. Maybe I should create a sticky in the Technical forum, for how often this question gets raised around here these days? )
I did:

http://www.caraudioforum.com/vbb3/sh...d.php?t=249411

Let me know what you think - I think you can see the difference between "defining what each spec is" and what I've written there - "what can I actually use that spec for?"

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Old 07-30-2006, 06:42 PM   #13
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Quote:
Originally Posted by geolemon
I did:

http://www.caraudioforum.com/vbb3/sh...d.php?t=249411

Let me know what you think - I think you can see the difference between "defining what each spec is" and what I've written there - "what can I actually use that spec for?"

Having a conversation with yourself again?
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Old 07-30-2006, 06:50 PM   #14
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Quote:
Originally Posted by Immacomputer
Having a conversation with yourself again?


he likes to type as you can see..... always imformative....
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Old 07-30-2006, 07:26 PM   #15
bassfreak

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i missed a few GEO!
MMS IS important and it often over looked by many companies. some even claim that a certain amoutn is ideal for the proper "transiant response". haha. its important thought def not to be over looked or misjuged when designing a woofer. BTW thanks, i tried to simplfiy it so everyone would have a mental understanding of wha they mean.
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