Driver below recommended Vas, but all other requirements are perfect

[jimbo7]

I'm wanting to build a THT with an Infinity 1232w, but the Vas is only 78.50 liters when the requirements are between 100-320 liters. Is it a worthy candidate?

PDF download of T/S specs
https://pdf.crutchfieldonline.com/Image ... 81230W.PDF

[Keryn O'Shea]

Hi mate,

"Vas doesn't matter all that much, so long as it isn't hugely large" -Bill

https://billfitzmaurice.info/forum/view ... &start=165
Towards the bottom

[Seth]

Hi mate,

"Vas doesn't matter all that much, so long as it isn't hugely large" -Bill

https://billfitzmaurice.info/forum/view ... &start=165
Towards the bottom

The quote being in response to a driver for a top, presumably DR280. I'm curious if the advice you quoted is cab specific or fairly universal to horns general, and therefore also applicable to the Tuba's and Titans's

[jimbo7]

The quote being in response to a driver for a top, presumably DR280. I'm curious if the advice you quoted is cab specific or fairly universal to horns general, and therefore also applicable to the Tuba's and Titans's

Thanks, Seth.

I've always adhered to the 10% above or below rule for crossover components, but speakers I like to get within the recommendations. After trying to understand T/S measurements and how Vas works, I gave up and decided to ask the pro(s).

[Keryn O'Shea]

I'm curious if the advice you quoted is cab specific or fairly universal to horns general..

Me too, I guess though when you're off reservation and you know it, if the driver is cheap/free it's up to the builder to take a chance and live with the peformance difference, I've been there many times! Sometimes you win..

Is the 1232 something you have already jimbo? Also how wide were you thinking?

[Bill Fitzmaurice]

It's universal to speakers in general. Vas simply put is related to the size required of the driver chamber. Smaller Vas allows smaller rear chambers, but it's not the only factor where that's concerned, Fs being more important. No matter how small the Vas you can only go so small with the rear chamber to realize a given F3. Very large Vas demands larger rear chambers. You don't often see very large Vas anymore, but with vintage drivers we did. The 3015LF Vas is 5.6 cu ft. The Altec 421-8LF was 20.3 cu ft.

[jimbo7]

Is the 1232 something you have already jimbo? Also how wide were you thinking?

Yes, I was gifted the driver and matching power amp from a friend. It was part of an Infinity home theater setup. As far as width, I'd like to make it whatever size works best (but <or= 28" to get through doorway)

Smaller Vas allows smaller rear chambers, but it's not the only factor where that's concerned, Fs being more important.

So being under the recommend Vas is not a bad thing? Since fs is on the higher end, a smaller width would be better, correct? But the Vas is way low so that also means a smaller cab is better?

BTW the Infinity 1232w specs are:
Fs 27.27
Qts 0.44
Vas 78.50L
Xmax 12.25mm

[Keryn O'Shea]

Yes, I was gifted the driver and matching power amp from a friend.

Sweet!!

Since fs is on the higher end, a smaller width would be better, correct?

According to the plans, yes I beleive so

[Keryn O'Shea]

.. The Altec 421-8LF was 20.3 cu ft.

[Bill Fitzmaurice]

But the Vas is way low so that also means a smaller cab is better?

Vas being low doesn't change the required length and mouth area of a horn for a given response.

[jimbo7]

But the Vas is way low so that also means a smaller cab is better?

Vas being low doesn't change the required length and mouth area of a horn for a given response.

Doesn't a narrower cab mean a smaller driver chamber and less horn mouth area? I know the horn path will stay the same regardless of width. I'm so confused now. Are we on the same page here? I'm just wondering if this driver is a good choice and what width is best for a THT since I'm beginning my home theater build. Sorry if I'm being difficult. But I do appreciate these little audio theory lessons.
I also have another option to build a Simplex 18 using a 18" JBL 2242HPL that came from a movie theater. That monster is just waiting to push some air.

[Bill Fitzmaurice]

The chamber size is the least important factor. #1 is horn length, which determines how low the horn will go. #2 is the mouth area, which determines low frequency sensitivity. The wider the better. Simplexx 18 won't equal THT in either low frequency extension or sensitivity. No direct radiating speaker has the sensitivity of a horn. That's why the Simplexx cabs have a performance quotient of 5, the THT is a 10.

[Tom Smit]

Would it help jimbo7 if he installed a chunk or two of 2x4 to take up some space in the driver chamber?

[Keryn O'Shea]

But the Vas is way low so that also means a smaller cab is better?

Vas being low doesn't change the required length and mouth area of a horn for a given response.

This ^

Yes, I was gifted the driver and matching power amp from a friend..

Wicked man! Hey there's a 20" THT here l wish you could feel, the thing has proper grunt! It's LAB15 loaded which has only around 20L more VAS than your driver..
I don't think you'll be disappointed at any width in a normal sized room with the THT personally.
I was leak testing the other day and as l was packing up l walked past and gave this THT 12v @30hz.. everything in the house was shaking, upstairs included, and our house is brick & steel
Go for it man..!

[jimbo7]

So it'll work fine?