Subwoofer and a suspended floor over a pool

[Tooldaddy103]

Odd title for an odd situation. Have searched and not found much info. My home has a large addition that is built over an in-ground swimming pool. A previous homeowner decided that having a pool in Wyoming didn't make much sense. Thus he enclosed the space and built a trussed wood floor over the pool. This addition is 35 x 55 (feet). The wood subfloor is carpeted. Ceilings are 10 ft. All drywall. I am subdividing this into a master bedroom suite, exercise room and a home theater. The HT will be approx 15 ft wide x 22 ft long. So room volume will be about 3300 CF.

Dolby atmos 5.x.4 setup. The 'x' is either 1 or 2 Monoprice 15 THX subs. My AVR is a Denon 6700H and the LCR are JBL HDI-3800s. 80% movies, 20% music.

Before I invest in a serious sub(s), I'm wondering what this flooring construction will do to low frequency audio. I know carpet will help with dampening. But the wood subfloor suspended over a pool? It's a concrete in-ground pool that could be filled with water today if I wanted a pool. I'm thinking (guessing) the carpeting will dominate over the below floor echo chamber. This carpeting is the thick plush stuff you find in better hotels.

Any thoughts? Trial & error it? I really would appreciate help.

 

[Koloth]

Sounds to me like you've got all the prerequisites for a monstrous folded horn subwoofer right under your homr theater

 

[DVDdoug]

The floor may vibrate and you might feel it but otherwise it won't have much effect on the acoustic sound. And, by the time the sound leaks through the floor, and then back (attenuated twice) I don't expect any audible effects of the pool. The original-direct sound should dominate and drown-out any of that.

And carpeting doesn't have much effect on bass since the wavelengths are long relative to the carpet thickness. I would tempted to use the pool-space as in "infinite baffle" for subwoofers.

 

[Tooldaddy103]

Sounds to me like you've got all the prerequisites for a monstrous folded horn subwoofer right under your homr theater

That would be the new Klipsch Mjölnir !! Guaranteed to only need one. Powered by Tesla.

 

[FeddyLost]

Most probably your bass experience will differ from one that you'd have in typical home cinema at ground floor or in the cellar.
If your walls and ceiling are not dense and massive (like concrete slab) you'll have much less bass issues than usually just due to significant LF leakage into everywhere.
Typical subwoofer is equalized to flat FR on ground plane, while your situation is like "hanging with the sub at 6' from the ground".
So, while AVR DRC will manage equalization at LP, you'll need MORE power to get bass as designed.
Any assumptions regarding how exactly will your flooring respond to LFE is useless just because it'supported somehow and somewhere and it can't be modelled as simple membrane.
If your floor as a plane is not very heavy (comparable to drywall), you can measure depth and use it as distance from the floor in REW Room Sim, but if ALL the wall and ceiling are light, you'll have small "standing waves artifacts", resulting in fast and dry bass like open-air concert.
I think, the result is that you shall not to rely on any type of room gain and calculate your SPL and subwoofer requirements as it's free field. 2x15" Monoliths is a good idea.

 

[sarumbear]

You have a perfect opportunity to use your floor as an open baffle by mounting a few woofer drivers to the floor. You will need proper EQ, like a DSP and many very large Xmax drivers but you will still spend less than an equivalent subwoofer.

In my old house my HT was built over a big cellar. I used 4x 15” JBL drivers mounted on the floor, each pair powered by a big Crown amplifier and all driven by a miniDSP. All drivers were clustered closely, hence I only used one DSP channel. It was awesome, flat to 20Hz, in other words f3 was below 20Hz.

If you have the knowledge or the time to educate yourself I urge you to try it. No subwoofer on the market can compete with an enclosure the size of a swimming pool!

 

[DWPress]

Only issue I potentially see is that exercise room and bedroom might get a little extra bass as well, especially if used as a sub enclosure.

 

[sarumbear]

Only issue I potentially see is that exercise room and bedroom might get a little extra bass as well, especially if used as a sub enclosure.

The partition walls cannot stop low bass anyway. The bass leak through the floor will not be an issue by itself.

 

[DWPress]

The partition walls cannot stop low bass anyway. The bass leak through the floor will not be an issue by itself.

But if you mount drivers in the floor, as has been suggested, the whole pool area will thump.

 

[sarumbear]

But if you mount drivers in the floor, as has been suggested, the whole pool area will thump.

As I read it, he is building the HT over the swimming pool. There’s a subfloor over the pool. The pool volume is empty. It will be the speaker enclosure.

 

[DWPress]

So there's no sound pressure in an enclosure? The enclosed pool area will have 3 partitioned spaces sharing that enclosure.

 

[sarumbear]

So there's no sound pressure in an enclosure? The enclosed pool area will have 3 partitioned spaces sharing that enclosure.

If I read it correctly, the swimming pool volume is empty. There’s no one in it. The rooms are over the swimming pool, which is covered by a sub floor. He said ceiling is 10’ how many indoor pools do you know that has such depth?

 

[DWPress]

I give up....

 

[Tooldaddy103]

Thanks all for your "deep" (no pun >> pool) thoughts & responses. I'll need to read up a bit more and likely trial & error. Never imagined hone audio could get so complex.

 

[sarumbear]

Never imagined hone audio could get so complex.

It is not complex at all if you use off-the-shelf subwoofers, etc. I was simply suggesting an alternative DIY subwoofer approach that I had successfully implemented in the past.

 

[Tooldaddy103]

It is not complex at all if you use off-the-shelf subwoofers, etc. I was simply suggesting an alternative DIY subwoofer approach that I had successfully implemented in the past.

Color me impressed.