What Volume to use for a 4-way with 18" woofer? - diyAudio
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Old 30th May 2012, 07:23 PM   #1
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Default What Volume to use for a 4-way with 18" woofer?

Hi folks!

How can I know / calculate the "preferred volume" (in cubic feet or cubic centimeters) for the enclosure of my 18" woofer speaker?

Its for my 4-way speakers (consisting of an 18"woofer, a Kef B200, a midtone and a ribbon tweeter)

Dayton Audio PA460-8 18" woofer Specifications

Thanks very much!

Click the image to open in full size.

Last edited by Eftegarie; 30th May 2012 at 07:37 PM.
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Old 30th May 2012, 07:29 PM   #2
tt398 is offline tt398  United States
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Default T/S parameters

You must obtain the Thiele / Small parameters for the woofer and design an enclosure for it using some design software. This is a start..
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Old 30th May 2012, 07:40 PM   #3
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The parameters are listed on the link he provided.

There is free software for this. Not sure how good it is though. Do you know if you want vented or sealed? What are you doing for the crossover?

AJ Audio Subwoofer Box Enclosure Design Software - Sub Speaker Cabinet Building Program Downloads
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Old 30th May 2012, 08:17 PM   #4
CCU is offline CCU  Denmark
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Hold on!

Designing a 4 way system is NOT an easy task.. and i gather that you don't have a lot of experience.
I would start with a kit if i were you OR do it as an active system, so it easy to tweak your way out of design "fault"
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Old 30th May 2012, 09:48 PM   #5
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 30th May 2012, 10:57 PM   #6
tvrgeek is offline tvrgeek  United States
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CCU, dead on.

If anyone does not believe how difficult it is to build a speaker system well, just go to the store and see how many build and sell speakers that are terrible. (most). Then go pick a speaker that is done well. Vanderstein 2Ce for example. Look carefully and ask yourself, "Now what am I going to do better?" It is not easy.

A few tips for first timers:
Build an established design. The place to start is to pick up Joe DeApollito's book on measuring speakers.

I do my box modeling in WinIsd even though I have SoundEasy. I do my T/S measurements with WooferTester II. I actually use TrueRta for acoustic testing more than I should ( paid high res version). At some point, you are going to buy a mic. Do not mess around, get one that is calibrated first. It will save you a lot of money.

Now here is what beginners do not want to know. 90% of the result is the crossover. Not the drivers, not the box. The crossover. Stick with cheap drivers and unfinished boxes until you understand this. I can design and build a box to be optimum for the problem in a couple of days. I can (and do) just send ScanSpeak or Seas lots of money and buy fantastic drivers. I have spent 35 years trying to understand crossovers for just a two-way. ( subs are easy. Electronic, 4th order at least)
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Old 31st May 2012, 07:46 AM   #7
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Thanks very much for all info!

Indeed, I will be using ACTIVE 4-way crossovers (from minidsp.com which are widely applauded by experienced users who only believed the quality after they compared these to expensive pro crossovers) with 4 amplifiers. so I have lots of room for tuning and adjustments.

The online free software over here

LinearTeam

advises an optimum of 80 as Vb, for a closed box which is what I want. But is this Cubic Feet or Cubic Centimeters??
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Old 31st May 2012, 12:06 PM   #8
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I can't open the software you linked to on my work computer, but I'd guess the 80 is liters, since it appears the website author is European.
Another great resource for DIY speaker building is the Parts-Express techtalk forum Techtalk Speaker Building. There are a lot of very knowledgeable and helpful members on techtalk. I've met several of them and have built some of their designs.
If you solicit some advice from some of the "gurus" for your build, you'll end up with a very good speaker. If you go it alone, you're missing out on a valuable resource. There is a LOT of physics involved with a properly designed speaker. There is a LOT of gratification in applying the principles correctly.
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Old 31st May 2012, 12:41 PM   #9
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It's not a good candidate for sealed, but maybe you can find it possible.
Test here. EBS Software.
Their site is wrong "Compliance Equivalent Volume (Vas) - 473.50 cu. ft.". It says Cuft instead of liters. You can find good Vas (liters) data on the pdf.
If you go on with the choice for your sub you can use it like this in a BR,
DAYTON PA460-8 18, VB = 154.0 L, FB = 28.8 Hz, 97.6 dB2.83Vm.
F3=44 Hz, F6=34 Hz, F12=24 Hz 05.2012
but be advise that you can get better l.f. extension with this 5" woofer in a 8 liter enclosure. TangBand W5-1138SM
PA woofers are not that great l.f. champions reproducers.
(This is advise for others as of course you can manipulate with dsp and equalization, but I don't have the experience. Please post your findings)
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Old 31st May 2012, 02:30 PM   #10
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Thanks for your advise! I will go for a closed box indeed. I trust my 4-way active crossovers and driver quality within my budget range.

I assume that a given VOLUME van be freely divided between whidth, height and deppth?

If so, then I am really in love with the following pproportions that would give me the perfect volume and a very compact tall speaker. See my drawing below.

Is this very possible or very utopian?

Click the image to open in full size.
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