Tell me how feasible this idea is (1 Viewer)

[Brett_A]

I am toying around with the idea of my next sub. Currently have a dual Shiva Sono and am very happy but as always there is never enough good bass.
After seeing the "closet" sub on M. Knapps site I had a few ideas. My HT is set into an alcove in my family room. THe size is 6' wide and 2.25' deep. My equipment and TV take up about half the height and leave a big empty space above. I was thinking of either doing an infinite baffle panel above with several subs or framing a sealed enclosure into that space and making it stealth either way. If it was selaed I could drop down about 2.5 feet giving me ~33 ft^3 of space.
What would be the advantages of both and how feasible are these ideas, be honest and critical as I want all opinions.

 

[Bill Fagal]

I give mad props to anyone considering an architecturally integrated sub! Now here comes the big HOWEVER...

You're gonna have to think very carefully about how this system will handle structural vibration--that'll be the real potential spoiler.

1. Your soffit/enclosure will need proper bracing to keep the long spans of panel from vibrating.

2. As the baffle will be directly coupled to your house, newtonian forces from the drivers have the potential to set up some really noisy rattles. I would suggest using a pair (or pairs) of drivers mounted on opposite sides of a small manifold, thus canceling the net force transmitted into your structure.

Go for it, and Godspeed! This kind of Vb gives you mucho bass potential. And just think: it may be the clincher when you sell your home. What red-blooded American male wouldn't be hooked on purchasing a home with extreme bass included?

Bill

 

[Brett_A]

Anyone else want to weigh in?

 

[Mark Seaton]

Absolutely I'll weigh in.
Do some homework, do lots of modeling with lspcad from Adire, or other things, and plan on using some EQ/correction. While Bill's concerns are valid, they are easily overcome, and there are benefits which offset some of these issues.
The mechanical coupling and "shake" factor is easiy overcome by mounting the drivers face to face like in many IB installations. With the drivers firing together the forces of each driver cancel eachother out. If you are using 4 drivers, as I would suggest, then the driver motion will be greatly reduced, and simply using a large flat baffle of braced Baltic Birch plywood (not MDF) would make for a very rigid structure. I would be much less concerned with using MDF if the drivers were mounted face to face. While the face to face mounting does sacrifice some volume, you are already in a large space, so the difference as a % will be rather small. Likewise, this allows smaller openings which need to be kept open. This allows for more creativity in the frontal appearance as opposed to just covering the entire thing in fabric. You could segment the 6' section with 2 openings. You could probably power the whole thing with a Hypex A1500 or similar power and just add an EQ in front of it. Many options depending on your goals, flexibility, and budget.
The other benefit with such a large enclosure is the relative decrease in internal box pressures. With such a large enclosure, producing the same levels requires a very small percentage volume displacement relative to the box size. This means that pressures exerted on walls will be much less significant. that said, I would still preffer to cover the drywall with something more rigid to low frequencies, ideally a void free ply of some sort or MDF, but this does not need to be very thick if budget limits options, as the drywall will add further stiffness. While much less critical with such a large enclosure, you will want to do what you can with weatherstripping and cauking to attempt to eliminate any leaks through the opening.
This is my only hesitation with just sealing off the chamber as without seeing your system, I am guessing it might be difficult to seal off the area. You will certainly get good output even with some leaks, but you will gain some by proper sealing.
Now the question is what you need/want from the subwoofer, how much you can justify in expense, and deciding on components for implementation. To consider this properly, you should post your speakers, power available to them, room dimensions, seating distance, and any planned, future upgrades you want to take into account. Also, what are in the adjoining spaces to this alcove? (behind, sides, above/below) Careful design and planning will gain you more than any "upgrade" in components. Also, with a system like this, remember the use of more drivers is not so much for getting louder, but for getting LOWER, and cleaner!
Regards,