What about a metal sub box. strong and thin. figure i get fit a normal size 12 behind each seat. make the side mdf but front ,back, top and bottom metal. should gain alot of space right? definetly have welding ability also a bend brake that can bend up to 16 gauge steel. for box volume i figured i could use the entire space up to the top of the seat and maybe but probably not need i could connect the two boxes together with some sort of tubing/ channel so its like 1 big box. any thoughts? i would actual be able to bend the metal around the wood sides and screw the box to the firewall.

You won't gain anything in mounting depth that way, and airspace gain will be minimal. The front panel would be about 24x18. If made of 1/2" MDF you'd be looking at 216 cubic inches consumed by it. That's a 1/8th of a cubic foot. The metal plate at 16 ga. would consume about 26 cubic inches of space so you'd only gain about 190 cubic inches of volume, less then 1/8th of a cubic foot. You might get back up to that 1/8th when you add in the extra air space from the top and bottom you mentioned making out of metal also. But! that will continue to be decreased because with the thinness of 16 ga. (0.06" thick) you will need to add dampening material to cut down on vibration and resonance. Dynamat (or orther similair product) I beleive is about a 1/16th to a 1/8th of a inch thick. Once you've subtracted it from you voulme aswell ( 27 cubic inches for 1/16th and 54 for 1/8th) you end up with even less gain of airspace (163 cubic inches of gain for 1/16th and 136 cubic inches for 1/8th). Basically your looking at gaining maybe 1/10th a cubic foot of airspace doing that and adding alot of expense.

Question though, why make the back out of metal as well? Why not just attach it to the metal that is already there behind the carpet?

Kinda like this.




Of course I cut out the lower second firewall to give me more mounting depth so I could make the boxes shallower, but then I'm over 6 foot tall.

[This message has been edited by Khw (edited 11-10-2010).]

What gauge? You are going to get a bunch of flex and the sub is going to be put through hell. Use mdf. Fill it with cotton.

quote Originally posted by 87antuzzi: What gauge? You are going to get a bunch of flex and the sub is going to be put through hell. Use mdf. Fill it with cotton.

He said 16 gauge in his post, which is only 0.06" thick, less then a 1/16th of a inch thick.

Use MDF. Don't bother with polyfill/cotton. And there's no need to try to connect the airspace between the enclosures. Keeping them separate will give you better sound.

Oh, and you also don't really need 12s in a Fiero. It'll be difficult to get enough air space in the enclosure for them to work at their best. With the airspace you're likely to get (without lots of cutting and extra work), smaller subs will give you better bass.

[This message has been edited by dobey (edited 11-10-2010).]

quote Originally posted by dobey: Use MDF. Don't bother with polyfill/cotton. And there's no need to try to connect the airspace between the enclosures. Keeping them separate will give you better sound.

It depends what the sub is rated at. If you are running a sub that needs lets say 1cf of air space and you only have .50cf then the polyfill will HELP the sub think its in a bigger box producing better sound. I did not read the 16 gauge part. That is going to flex like crazy and will kill the sound. And why are you going to use a 12?

quote Originally posted by 87antuzzi: I did not read the 16 gauge part. That is going to flex like crazy and will kill the sound.

Yes it is going to flex alot. He could reduce the flex with some internal bracing, but that is going to consume even more of the airspace he gains.

[This message has been edited by Khw (edited 11-10-2010).]

quote Originally posted by Khw: Yes it is going to flex alot. He could reduce the flex with some internal bracing, but that is going to consume even more of the airspace he gains.

Depending on the sub.....Best bet would be a shallow mount sub that requires minimum airspace. Pioneer makes a decent cheap shallow mount sub. The 13.5 inch square woofers will rock a fiero out of the body pannels. The JL w3 was the first sub i had in my fiero. And it sounded awesome!

quote Originally posted by 87antuzzi: It depends what the sub is rated at. If you are running a sub that needs lets say 1cf of air space and you only have .50cf then the polyfill will HELP the sub think its in a bigger box producing better sound. I did not read the 16 gauge part. That is going to flex like crazy and will kill the sound. And why are you going to use a 12?

Most any 12+ inch sub is going to want more than 0.5 cu ft of air volume. Making a vented box, instead of sealed, would be better here. With a shallow-mount sub, in a sealed box here, the volume is going to be about 0.4 cu ft. An 8 inch sub would work much better with that, than the 12. The polyfill doesn't giv you better sound. It gives you louder perceived volume. There's a difference. It reduces the volume of the box, but causes the sound inside the box to slow down slightly.

And most people want 12s because "they are bigger" and obviously bigger subs are better.

quote Originally posted by dobey: And most people want 12s because "they are bigger" and obviously bigger subs are better.

Back when I first got into stereos I bought two 10" Kicker C-10's. I loved them but thought 12's would be louder so when that system got stolen I bought two 12" Pyle W1240's. They really wern't louder as far as I could tell from listening but they did require a much larger box. As I grew more experienced, I found the biggest difference between a 10 and a 12 was frequency extension meaning the 12 would usually play to a lower frequency, say 20 hz vs, 25 hz for the 10" version. Most boxes, when ported, I found, were ported in the 30ish hz range, so a lower frequency was really kind of pointless, that and the reality that most people can't hear 20 hz. My sub of choice became 10's. I much prefer the less consuming volume for the enclosure.

I do agree, most people think bigger is better as I was victim of this idea early on also.

However... I must say the two 18" subs I helped my freind put in the bed of his Toyota 4X4 were most excellent to experience. To bad the enclosure took up his entire bed and popped the glass out of his camper shell when played.

quote Originally posted by Khw: I do agree, most people think bigger is better as I was victim of this idea early on also. However... I must say the two 18" subs I helped my freind put in the bed of his Toyota 4X4 were most excellent to experience. To bad the enclosure took up his entire bed and popped the glass out of his camper shell when played.

Right. The trick to building a good system is to get the right balance between the enclosure requirements for the sub, and the size of the cabin where the audio will actually be. In something like a Suburban, you've got a lot more cabin air volume to work with, so bigger subs will help fill the cabin better. But with a tiny cabin like in the Fiero, you don't really need big speakers to get amazing sound.

quote Originally posted by Khw: However... I must say the two 18" subs I helped my freind put in the bed of his Toyota 4X4 were most excellent to experience. To bad the enclosure took up his entire bed and popped the glass out of his camper shell when played.

Just to clarify. His camper shell was similair in style to the photo below and the window with the red arrow pointing at it is the window that popped out on his.