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Subwoofer in Fireplace Hearth

post #1 of 11
Thread Starter 

I would like to "hide" one or two subs in a new fireplace hearth under construction. The hearth is 16" x 16" x 108" long finished. The sub(s) must open out the sides of the hearth. It will be made of 3/4" plywood with a 2" stone top and faced with 2" stone on the front face, so I only have about 13 inches to work with for the opening. I have read DYI sub sites and the calculations are too complex for me, so I am asking for help / suggestions. Should I buy pre made subs and put them In the openings or buy the sub parts and install on each end? I could get bigger ones if i build it myself. Either way, I need specific part info or model numbers.

My only other options are to cut into a wall (which will get me in big trouble) or hide one in plain site somehow.

I normally use a regular receiver to drive the surround system. Thanks in advance for you help.

post #2 of 11
Can you post a picture because I'm having a hard time visualizing this.
post #3 of 11
Thread Starter 
Attached are three pics. One is the floor plan, one is a view of the fireplace. The hearth is at the bottom of the image and the subs would be located inside one or both sides. The last pic is of the right side wall where I am considering a drop down screen as an alternate to having the tv above the fireplace. Either way, the subs can not be in the cabinets of the window seat.


living room - fireplace wall.pdf 485.3154296875k . file


living room layout 1.pdf 421.6044921875k . file


tv screen wall.pdf 387.8056640625k . file
post #4 of 11
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.
post #5 of 11
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.
post #6 of 11
Oh and if you can fit 15" woofers, you could go sealed with dual Dayton RSS390HF. That would be my first choice.
post #7 of 11
Thread Starter 
Sorry for not being clear. I will try again. This is being built as we speak so there are no photos of the actual fireplace. Attached is a new drawing from the side view. It is a plywood box 13.25x13.25x102 inches. Since I know you need to calculate volumes, you would have to take into account that there is a void under the 13 in box where the gypcrete (concrete) did not flow between the 2x4 studs. I had planned to use speaker fabric to cover the speaker on the ends, but I have only the 13.25 inches to insert a speaker. I could put one on each end of the box, or just on one side and leave the other side open or closed, whatever you think is best. Hopefully this helps. Thanks for the input. This is a fun project.
post #8 of 11
Thread Starter 
Here is the attachment. It did not upload in last post.


Hearth.pdf 163.001953125k . file
post #9 of 11
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.
post #10 of 11
Thread Starter 
I was thinking of using Martin Logan EFX speakers, with Martin Logan EM-C2 center, and two ceiling recesses surrounds (5.1). I was planning on getting a new receiver, +/- $600 to switch my PS3, Dish Network, Computer to the TV monitor located in a recess above the fireplace. So the sub project could be in the price range described by coctostan above. Thanks.

Are the subs powered so that I can drive the two subs off on the one receiver or will I need a separate amp for the subs? Just trying to keep it simple.
post #11 of 11
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,
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