In-floor sub-woofer

[RomfordNavy]

Due to limited space I am now looking at the possibility of through-floor mounting (floorboards) but have a few questions on this:

• Would it matter much if it were covered by carpet as I am reluctant to cut holes in an expensive bit of 35' long carpet? I hope that wouldn't absorb much in the way of very low frequencies would it.
• Might even need to have some thermal insulation like a sheet of foam rubber covering it to keep the cold out during the winter, is there anything which has good thermal insulating properties but allows low frequency sound to pass through?
• Apart from the small resistance to air-flow from the carpet, thermal insulation and possibly floor joist would this effectively be like an infinite-baffle?
• Cone could be facing upwards or downwards depending on exactly how I implement this and may be in a shallow box sitting on top of the carpet with a hole in the floorboards beneath.
• Would it help to have a very large right-angle box or tube on top so as to direct the output towards the listener or is that irrelevent with sub-bass?

 

[DVDdoug]

I wouldn't expect too much sound reduction from the carpet at subwoofer frequencies. You might have to take care that the carpet doesn't vibrate/rattle.

is there anything which has good thermal insulating properties but allows low frequency sound to pass through?

MAYBE regular fiberglass insulation?

Cone could be facing upwards or downwards depending on exactly how I implement this and may be in a shallow box sitting on top of the carpet with a hole in the floorboards beneath.

Either way is fine. If you put it "backwards" you'll need to reverse the polarity of the connections to keep it in-phase with the main speakers.

Would it help to have a very large right-angle box or tube on top so as to direct the output towards the listener or is that irrelevent with sub-bass?

Long wavelengths are non-directional. (100Hz has a wavelength of about 10 feet.)

 

[LTig]

I agree with @DVDdoug. Be aware that you need a speaker which is designed for an open baffle (no box).

 

[Audionaut]

Be carefull

 

[voodooless]

I agree with @DVDdoug. Be aware that you need a speaker which is designed for an open baffle (no box).

That very much depends on what is on the other side. If the volume is large, you want to find a woofer that is suited for an infinite baffle: strong motor, Qts higher than .45, high VAS, low fs. and much excursion as you can afford. If you do not have a lot of volume to waste, a more conventional subwoofer driver will be fine.

I’m not sure the carpet and insulation won’t have a major effect. Even if the sound travels though the carpet, it will add mechanical damping to the driver, compression, etc.

 

[JohnnyNG]

If you have space, you might consider a manifold with opposing drivers. A driver in IB is essentially operating in free air so is somewhat prone to overexcursion.

IB subwoofer picture gallery page 1

 

[Andysu]

in-floor sub bass array with a specific difference