Subwoofer in Fireplace Hearth

Can you post a picture because I'm having a hard time visualizing this.

I'm still not sure about Where exactly you want to put the subs. Is this fireplace not built yet? If anything take a real picture if possible and outline the area or just outline the area in your computer image that you made. Without knowing that and only knowing that you have a 16x16x108 area you could possibly do something like 4x - 10" subs. I say 10" because I thought I saw that the opening will only be 13". You might be able to get away with 12's if they fit but 3/4 ply is going to make the interior dimensions 1.5 smaller leaving you with 11.5". You could power them with pro amps which will save you some room. Honestly I can figure out the correct box size for you but I have never done any in-wall installs of a subwoofer and 4 10's or 12's...possibly more could give you the bass your looking for with no problem. I think it's a very interesting idea though and will help any way I can.

So you basically have a 16"x16"x108" boxed section that you want to play a driver on each end. Are those external dimensions? Let's assume internally you have 13"x13"x100" to work with. That gives you about 9.5cu ft to work with.

You could put a 12" subwoofer on each end with a slot port below the driver on each end.

You aren't likely going to get extension below 20hz, but you should be able to get very good clean output from 20hz up.

If you give me a budget for drivers and amp, I can model some stuff. I'd say you could do this for somewhere between $300 and $800.

Oh and if you can fit 15" woofers, you could go sealed with dual Dayton RSS390HF. That would be my first choice.

I would use the plywood structure for the box. You will need to brace it and make sure it is sealed off. You can fit a 12" driver (Dayton RSS315HF) on each end and use that bottom section between the 2x4's for a slot port. Does that make sense?

With that setup and about 400w with a highpass filter at ~20hz you can get about 115db in room. Those are very high quality subs at a very good price.

You want to hide the sub in the footer of the fire place, under the hearthstone that's shown a little off the floor in the first post? You'd build a plywood box, then have the builders enclose it with stone?

13.5x13.5 limits you to 12" woofers. Look for sealed sonotube projects to see how folks deal with the inevitable pipe resonance that results when a driver's at one end of a closed pipe. Dual opposed would be good, but only if the combo needs the entire 9 cu ft volume.

Nice looking place, by the way....

Have fun,
Frank