Enclosures design software issues

[Ilianh]

I started a subwoofer project today,
Using a Max Pentivent PV-1030 10" driver.

I entered the same specs in 2 apps
The JBL Speakershop Enclosure module V 1.0
and WinISD 0.5a6

The specs are basic Theile-small specs, Vas, qts,qms,qes,Fs mms,Xmas...

http://www.maxspeakers.net/products/pentivent/

But the two apps gave me major differences, winISD considers the woofer a 85 dB/w/m woofer, and JBL considers it 90db/w/m.

and JBL tells me a 1.6cuft box would be enough, and winisd gives me a 2.6cuft i think..

If you click on the model in the specs sheet, I noticed that Max themselves are using the same version of JBL speakershop and are having the same results as I am.

Wich one to trust?

 

[planet10]

You aren't really giving us enuff info... sealed, reflex? What Q?

For a sealed box:

Q=0.707 (butterworth) 1.5 cu ft
Q=0.57 (bessel) 2.8 cu ft
Q=0.5 (best group delay) 4.4 cu ft

dave

 

[Ilianh]

Oh... forgot to specify, its for a vented Enclosure

On the page I posted, theres a link with the woofer's specs, click on the "Max pentivents specifications" on the right.

 

[planet10]

Oh... forgot to specify, its for a vented Enclosure

There is even a larger range of potential box-sizes for vented. Both programs may be right (althou no program should just give you a single alignment) but with different alignments.

I don't as a rule do vented boxes so i'm not going to be much more help.

dave

 

[philb]

i used these

I built a sub using two 1030's, each put in a 2 foot box, ported (can't remember port size), and put lots of dampening on back wall of box. The box is huge, but it really sounds good.

 

[mikee12345]

i dont have the luxury of having winisd a6 and a7 and subsim on the same pc ,recently got a 486 to use now..

But compare the programs,with the SAME alignment,see if theirs discrepencys.

The winisd calculator is just that,a calculator using the available specs. i find it close to stated manufacturers #s in accuracy for efficiency guesstimation.

 

[GM]

The JBL program appears to be designed for prosound apps, or what Wayne Parham calls his Pi Align alignments. They are quite good for their intended apps, but unless you use a sub, or possibly stuck in a corner, these aren't really suited to a typical HIFI app.. JBL appears to be using Re to calc a 2.83V/m sensitivity, again, typical for prosound apps..

WRT WinISD, I avoid it like the plague, though in this case 2.6ft^3 is 'close enough'. BoxPlot calcs 2.58ft^3 and Margolis-Small, 2.87ft^3, but it assumes no damping material so ideally will need to be tuned a couple of Hz lower.

Anyway, the specs appear to be somewhat off since I calc a 100.4g Mms Vs the published 62g, with efficiency at 85.67dB/W/m, No = 0.232% Vs the published 0.4%, which could also indicate considerable inductance, so Caveat Emptor.

GM