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Discussion Starter · #1 ·
I have a limited understanding of Vas and other parameters and characteristics that affect things. I believe smaller motors are dsired for IB setups to keep a flat responce, where usually larger motored drivers will have a peaky responce?


So how does an IB3 model so close to a Maelstrom-X or Avalanche when the two latter drivers are pretty decent for strength?
 

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Look at the Q, the Xmax and the Fs.
 

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Discussion Starter · #3 ·

Quote:
Originally Posted by penngray /forum/post/19567892


Look at the Q, the Xmax and the Fs.

IB3 Qms 3.41 MX18 3.62

Qes .81 .42 the MX is 1/2 that of the IB3

Qts .65 .37 the MX is 1/2 the IB3


Xmax close, IB3 a little higher
 

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The IB3 Qts seems really high, especially for an IB design.


I remember Thomas stating that the Qts should be fairly low and the drivers should simply have lots of displacement, since many drivers are in an IB install there isnt another parameter that is going to be as meaningful considering 4 or 8 of them should never operate more then 50% of their max potential.


Could you post the model differences?
 

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The Mal X will obtain a higher system Q via the smaller box it was designed for; thus, in order to end up with a damping factor neither too high (ringing/boomy) or too low (low gain) the Mal X must have a lower Q.


A lower Q may be associated with a larger motor in 'good' designs; after all, if you need to drive a cone harder to go the same distance as a higher Q driver, you need to apply more power. Which explains why using a Mal X is 'overkill' for an IB; you can probably feed it a fair bit of power, but in the end a lighter duty motor with a higher Q will do the same job.


EDIT: attached is a quick WinISD plot comparing an IB3 in an IB to a Mal X in both a small box and an IB. As you can see, the large IB doesn't alter Q by much, but the small box drastically increases it. As a result, the efficiency of the Mal X suffers in the IB.
 

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Quote:
Which explains why using a Mal X is 'overkill' for an IB

yeah its overkill but we have to remember that IBs are all about having multiple drivers, the more drivers you add the less dependance you have on any specific more design.


We do not build IBs with ONE driver in mind so we do not need to spend more $$$ on getting overbuilt motors. Its really all about $$$/liter of displacement. That has always been the biggest factor in selecting an IB driver (Thomas W. stressed the Q values too)



Someone should posts these questions on the IB Cult forum. They will answer these questions properly.
 

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Penn--while I don't particularly disagree with anything you stated, I'm kinda viewing this thread as a good forum to answer the question "What is Q and how does it affect my system?"


System Q defines how damped the speaker's response is. Below .707, the response is 'Overdamped'; the response is very accurate but you will not achieve optimal efficiency. Above that value, the system is 'Underdamped' and will tend to ring, but this ringing effect also increases the apparent efficiency. .707 is considered to be 'Critically Damped', the happy medium between the two; the rise/fall time is the fastest possible and thus minimizes ringing whilst maximizing gain.
 

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Thanks Starkiller, its a great post explaining Q values in any model. FWIW, all my sealed box models tend to end up around .5 instead of .7...just many factors to consider.


I have always wondered how EQing effects the Q of these modelled boxes?
 

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Discussion Starter · #9 ·

Quote:
Originally Posted by penngray /forum/post/19569008


The IB3 Qts seems really high, especially for an IB design.


I remember Thomas stating that the Qts should be fairly low and the drivers should simply have lots of displacement, since many drivers are in an IB install there isnt another parameter that is going to be as meaningful considering 4 or 8 of them should never operate more then 50% of their max potential.


Could you post the model differences?

Basically you want a low Q motor to begin with, as it will be in a super low Q "enclosure" that will have minimal effect on the driver's own Q.
 

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Discussion Starter · #10 ·

Quote:
Originally Posted by kryptonitewhite /forum/post/19568790



IB3 Qms 3.41 MX18 3.62

Qes .81 .42 the MX is 1/2 that of the IB3

Qts .65 .37 the MX is 1/2 the IB3


Xmax close, IB3 a little higher

TC Sounds 18" LMS-5400 DVC Qms- 13.01 Qes- .39 Qts- .37

SoundSplinter RL-p 18 D2 Qms- 4.54 Qes- .48 Qts- .44

Mach 5 Audio IXL-18.4 Qms- 5.59 Qes- .39 Qts- .37

Avalanche 18" Qms - 6.00 Qes - .429 Qts - .400
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by Starkiller4299 /forum/post/19569177


Penn--while I don't particularly disagree with anything you stated, I'm kinda viewing this thread as a good forum to answer the question "What is Q and how does it affect my system?"


System Q defines how damped the speaker's response is. Below .707, the response is 'Overdamped'; the response is very accurate but you will not achieve optimal efficiency. Above that value, the system is 'Underdamped' and will tend to ring, but this ringing effect also increases the apparent efficiency. .707 is considered to be 'Critically Damped', the happy medium between the two; the rise/fall time is the fastest possible and thus minimizes ringing whilst maximizing gain.

Thank you Killer, I am asking what these different terms mean and that is a good answer for one of them
 

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I have 4 IXL-18's in my IB and they work great!! I can't wait for the new version to come out. I've seen them and they are pretty badass looking!
 

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Glad I could help some, KW. As for Vas and Fs, my layman's understanding (this is more audio than electrical, which is my specialty
), Vas is a measurement of the driver's suspension's compliance (or stiffness). The quantity, Vas, tells how much air is necessary to match the stiffness of the driver to the stiffness of the box, although 1:1 is not always the 'ideal' ratio as far as I can tell.


Fs is the free air resonance of the driver; the frequency at which the driver resonates in free air. It is the most fundamental statistic for determining the low corner of a driver's frequency response.


These are, of course, interrelated. The stiffness of the suspension would clearly dictate the Q of the driver and the Vas, for instance.
 

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Discussion Starter · #14 ·
I think I like drivers with soft/loose suspensions and a low low Fs. What is a low Vas number and what is a high Vas number? (I get confused sometimes it seems like golf and a high number is a low if that makes any sense)
 

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Quote:
Originally Posted by kryptonitewhite /forum/post/19571840


I think I like drivers with soft/loose suspensions and a low low Fs. What is a low Vas number and what is a high Vas number? (I get confused sometimes it seems like golf and a high number is a low if that makes any sense)

For 15'' drivers, I've seen Vas from 300+L (some peerless driver I tested, Fs=17hz) all the way down to 11L (car audio SPL specced driver, Fs=71hz), seem to average roughly around 100-150L.
 

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Penn... We actually want a higher q driver for ib. Right at .7 is perfect. This is because .7 system q gives the flattest response to f3 without overshoot and ringing. Lower system q has a falling response as you approach f3. Higher q has a peak near f3 increasing efficiency bit adding overshoot.


Because an ib doesn't add to the system q, the value is determined solely by the driver. Thus we want the driver near .7. This same rule applies to open baffle for the same reasons.


In a small box the box q adds significantly to the total q, so we need a lower driver q as a starting point so that the total isn't way too high. Many comercial subs are still too high though, with peak at f3. One note wonder.


Of course, that's the simple view. In reality each room has a different gain starting at a diffrent frequency. You might need a a lower system q with gradual rolloff so that with room gain you get back to flat response.


And to answer another question above, eq does affect system q. Frequency and time domain are intertwined. Add an eq bump at a given frequency and you add ringing. Add eq of the right bandwidth and you alter system q. In fact, this is the principle behind a linkwitz transform. You can add a tailored eq to any sealed sub and box system to create whatever final f3 and q you want. The tradeoff is that you may require more power to get there. Which again is the point of not using a malx with big motor and stiff suspension and heavy cone for an ib. You'll have to linkwitz transform it back to flat response, and it will take a lot more power to get there than say an ib3. You're burning needless power just to get the big motor and cone and suspension moving at all. But then, it doesn't take much power to drive any speaker to full excursion at low frequencies in an ib so we really don't care much about loss of efficiency down low. It becomes a matter of cost per displacement. Get the most displacement you can with good distortion measurements for the dollar. It doesn't matter what the rest of the specs are. Just linkwitz transform it to flat.
 

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Discussion Starter · #17 ·
Fs 71Hz!!!!!!!!!!
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19569177


.707 is considered to be 'Critically Damped', the happy medium between the two; the rise/fall time is the fastest possible and thus minimizes ringing whilst maximizing gain.

I actually thought that 0.5 was considered to be critically damped.
 

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Quote:
Originally Posted by Bigus /forum/post/19572037


Penn... We actually want a higher q driver for ib. Right at .7 is perfect. This is because .7 system q gives the flattest response to f3 without overshoot and ringing. Lower system q has a falling response as you approach f3. Higher q has a peak near f3 increasing efficiency bit adding overshoot.

Thanks

I do see the latest IB choices having higher Qts values these days but 5 years ago when Scott from Ficar audio first wanted to get some drivers into the Home market there was discussion about modifications. I was one of the first individuals to order from Scott, I know that the Q18s he spec'd for me where modified with slightly different surrounds and the Q value was lowered a little.


Its been 5 years so its pretty well forgotten now.



btw, I always have used this spreadsheet for finding the best IB driver

http://pages.sbcglobal.net/ginmtb/wo...ison_chart.htm
 

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Quote:
Originally Posted by Antripodean /forum/post/19573113


I actually thought that 0.5 was considered to be critically damped.

Correct
Quote:
Originally Posted by Starkiller4299 /forum/post/19569177


.707 is considered to be 'Critically Damped', the happy medium between the two; the rise/fall time is the fastest possible and thus minimizes ringing whilst maximizing gain.

Qts of 0.707 is 'maximally flat', Qtc of 0.50 is 'critically damped'
Quote:
Originally Posted by penngray /forum/post/19569200


I have always wondered how EQing effects the Q of these modelled boxes?

EQ (other than a LT circuit) raises "Q". The biggest offenders are narrow filters with a bunch of cut/gain. Least problematic are wide (broadband) filters with minimal cut/gain.
Quote:
Originally Posted by kryptonitewhite /forum/post/19566397


I have a limited understanding of Vas and other parameters and characteristics that affect things. I believe smaller motors are dsired for IB setups to keep a flat responce, where usually larger motored drivers will have a peaky responce?

IB specific drivers have smaller motors because they're excursion limited not thermal limited. No need to pay for a massive motor structure when it can't be used. IB drivers hit the excursion limits of the suspension before they encounter thermal limiting.
Quote:
Originally Posted by Bigus /forum/post/19572037


We actually want a higher q driver for ib. Right at .7 is perfect. This is because .7 system q gives the flattest response to f3 without overshoot and ringing. Lower system q has a falling response as you approach f3. Higher q has a peak near f3 increasing efficiency bit adding overshoot. .

Lower Qtc isn't a problem IMO. I prefer the 'dryer' sound of a low "Q" system to that of one with a "Q" of .7 or higher, especially when the effects of room gain are accounted for.
 
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