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DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

okay so i just bought (2) JBL GT5-15 subs and i need some advice on the box i got. its 3/4 mdf and 2.45 cub. ft. per chamber. the requirements for my subs in a sealed box is 1.5 cub. ft. per chamber.will it b bad for my subs to have this much extra space? do you guys recommend cutting the box down to size? will it make much of a difference? i appreciate all advice!!!:D:D:D
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

Just stuff the chamber with pieces of wood to bring the size down. Simple, and cheap. Changing the volume of an enclosure is not rocket science.
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

Thanks :laugh:Do you recommend gluing them down or something so they dont bounce?
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

I'd first recommend listening to it before you do anything, then judge any change you make against that. You may be smart to take notes on paper because the ear and human mind has a hard time remembering differences.

IMO, if you got the requirements from JBL's papers, then it is a bit too small anyway. You have to map out your own spec if you want to get ideal. JBL is simply providing a box size that works but it may not be ideal. It also may allow them to get a higher MAX WATTS rating since box size determines this.

I'll do some quick WinISD work and figure it out for you...brb
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

OOOHHHH K, that was weird. Win ISD is saying that you need a 33.12 cubic foot box per sub to get a perfect .707 Qtc. That's a weird number!

In the 1.5 cubic foot box they recommend, the Qtc is 1.25, REALLY, REALLY high. Very peaky, and the -3 dB cutoff is quick, like ~40hz (I'm guessing by a graph, I can get more specific later at home w/ the real program.)

In a 2.45 cubic foot box, the Qtc is 1.06, still high, but better.


This sub might be friendly in an infinite baffle setup, especially by the pair! Looks like it by the specs and by the recommendation on JBL's paper I d/l'd for the specs.
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

so the box im getting will sound better than jbl's specs? thanks for all your effort btw
 

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Re: DUAL 15" BOX HELP<<<<<<<<<<<<<<<<<<<

Ok, let me see if I can explain...

Now this is only one guy's opinion, so take it for that and seek others before moving forward:

The JBL sub you have there is an Infinite Baffle sub, really. That means that its design really can use an infinitely large box, and still sound good. The smaller box you put it in, the more power it can handle but the less low frequency extension it will have. Further, as you get a smaller box, it will have a more muddy, or perhaps I could word it as sloppy bass output. This is a unique sub, really built for IB work. JBL's specs match that, but also the JBL paper on the sub itself mentions IB as a possible route. Something I've learned is that if a sub doesn't mention being IB-capable in the specs and manual, then you really shouldn't attempt it. However, if a sub DOES mention it, it very well might the best thing for it. I think that's the situation here. The sub only has a few hundred watts power handling capability, and in an IB configuration the response plot looks like a wonderfully flat curve (this is from JBL, and confirmed w/ WinISD.)

IMO, give this sub as big a box as you can, and/or consider making your trunk the box! IB-style.



Any others have thoughts?
 
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