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Discussion Starter · #1 ·
I came across an old Adire Brahma 15", 4ohm total subwoofer driver on Craigslist for $100. At $100 I figured it would be a fun driver to play with. This teenager had it in the trunk of his mustang in a really nicely done, sealed 2.5sqr ft box so it seemed a good deal.

First, I am spectacularly happy with my Shiva X, 10sqr ft cabinet, and Behringer EP combo (there are a bunch of people with exactly the same set up so you are a familiar with it). So I am not looking for a replacement home theater sub. So I threw the Brahma 15" in my unfinished Shiva test cabinet that was 9.5ft with the crude bracing and hooked up the Behringer……WHOA! The Brahma is loud as hell! BUT!!! I can’t hide TWO enclosures this size in my living due to wife constraints. Not to mention my Shiva cabinet is already finished very nicely.

So I slapped it back in the sealed 2.5ft enclosure it came in. I then cut a hole in back of the box and installed my unused MCM 300watt plate amp with an Elemental Designs sub eq on top. Finally, I finished it off with some decorate wooden legs to make it look more “Home” audio oriented. It sounds surprisingly nice in this set up. With room re-enforcement and a 20hz eq bump it sounds much better than it modeled. In fact, it is surprisingly loud for its footprint (not Shiva loud at 20Hz of course ;) )


Now I did upgrade the MCM amp's power supply by replacing the 2 x 6800uF 80vlt caps with a bank of 4 x 8200uf 80vlt caps (and beefier rectifier to charge them) I had left over just to keep it in line with the whole 10,000uF per 100watt general rule of thumb. But it is still only 300watts so I am only using roughly half the Brahma's capable Xmax according to model.

The cabinet is ¾” MDF and internals are 15.5”x15.5”x21” – minus driver volume, stuffed with 2lbs of acoustic fill and has NO internal bracing. I don’t think I can spare much airspace plus it is fun to have a small foot print sub project that I don't have to fill the garage with sawdust again to play with.

QUESTION: So should I add bracing since I am not putting a butt-load of power to it? If so, how much bracing should I add for such a small wall area? I also have a 4’x 5’ x 1/8” sheet of lead I could cut and glue to the interior walls to bring down the resonant frequency instead of bracing the walls. I am curious to the expert and not so experts forum. thoughts
 

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With subs, you don't want to bring down the resonant frequency of enclosure panels. If you did, it would be more excited by the sub. What you want to do is raise the resonant frequency so that a sub has no effect on producing audible box vibrations.

Bracing takes a panel that would normally be 20" across and cuts it down into 2, 10" panels. A 10" panel has a much higher resonant frequency (double?) than that of a 20" panel.

So don't add lead, that won't help anything. If you want to add bracing, with minimal effect to volume, use dowel rods and connect parallel panels together.
 

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Discussion Starter · #3 ·
THANK YOU THANK YOU THANK YOU! That is EXACTLY what I needed to know! I great appreciate the info!
 

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Discussion Starter · #5 ·
Yeah, the poor guy had started out a lot higher than than $100...... about 3 months ago. But it IS an older driver from a now defunct company so I had some bargaining tools.

Since Adire's site is gone it has been a pain in the butt to find a lot of info on it for hometheater use. But I have been lucky that WinSD already had parameters for. I probably would be totally hosed otherwise.


The funniest thing is when I fired it up in the 9.5ft ft box with the Behringer, my wife said quote "Holy **** that thing is like slap your mama loud!":bigsmile:
 

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Bracing takes a panel that would normally be 20" across and cuts it down into 2, 10" panels. A 10" panel has a much higher resonant frequency (double?) than that of a 20" panel.
Hmm... I had this conversation with thxgoon a while back and I am not sure that is the case. Take a look at page two of this topic and in particular post #40. I was never able to track down difinitive references. It seems to me that a lot of bracing is designed around how people think panel resonance works as opposed to the actual physics/science.
 

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Discussion Starter · #8 ·
I have learned to purposely misspell names and descriptions when searching Craigslist. You find some GREAT deals that way!!!! People start knocking down prices because they can't figure out why no one is responding to their ad. Especially in the DFW area where the listings move REALLY quickly.
 

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Hmm... I had this conversation with thxgoon a while back and I am not sure that is the case. Take a look at page two of this topic and in particular post #40. I was never able to track down difinitive references. It seems to me that a lot of bracing is designed around how people think panel resonance works as opposed to the actual physics/science.
Can you post that link again. It's not correct.
 
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