[mikeeastman]

I'm building a new sub for my bedroom system, It is a sealed sub and will sit on the bottom shelf of  my build in entertainment center, 20" off of floor. With my old sub I covered the shelf  opening with speaker cloth. I was thinking of covering the opening with a solid baffle, with a hole for the sub to fire through, would this be better  acoustically? or will it not make any difference.. Here is pic of entertainment center.

[mcgsxr]

I would think that a grill cloth cover would sound better, as it would help prevent resonance inside that closed off area vs a solid baffle.

I built a large 2x12 subwoofer into the wall in my basement, and covered the opening with grill cloth.  Excellent movie sub.

[JLM]

Look for subwoofer kits/plans that you can adapt (that someone else has built/listened to) to avoid mistakes.  What you're describing seems like a non-standard design (that some have done very well with, thinking TBI).

Any time someone wants a built-in sub like this I think of infinite baffle subwoofers.  Here's a good link:  http://ibsubwoofers.proboards.com/index.cgi

[mikeeastman]

JLM, You misunderstood what I'm doing. I'm building sealed sub and just sitting it on the shelf. I thought that if I put a solid front on the shelf and fired the sub through a hole with the sub sealed against the back with a gasket maybe? My thought is that with the solid front ( rather than just grill cloth ) that all the sound would go into the room and not wrap around the box and into the shelf space. Would this be acoustically better?

As far as my design goes, Danny at GR calculated my box volume. The cabinet is 3/4" MDF  inside box with 3/4" birch ply outside, the inside will be lined with 3/4" man made stone used for counter tops with no-rez over that. The driver will be mount to a baffle that is sandwiched between an inner and outer baffle with 3 layers of damping material between them. The edges of the driver baffle also has  layers of damping materials between them and the box. I hope this will isolate the drive from the rest of the box.

  Mike

[nickd]

Mike,

Use speaker grill cloth on a frame to cover it. 

The solid baffle (with a hole) may introduce a bit of cavity resonance. If you go that way, you might consider packing acoustic dampening material around the sub to fill any empty space between the sub and the walls of the shelf. Your ears will tell you if you have a resonance or not.

[mikeeastman]

Nick, thanks. If there is no resonance problem would there be any advantage to the solid front?

  Mike

[Letitroll98]

No, this is not a good idea.  You are creating a 4th order bandpass subwoofer with uncontrolled design characteristics.   If you wish to build a bandpass subwoofer in that space, you could model one very nicely and there are some advantages to this design, but sticking an existing sub behind a panel with a port drilled in it wouldn't be wise.   

[mikeeastman]

Sorry I didn't make it clearer, there is no port ( don't like ported subs ) the hole is directly over the driver. So basically I'm creating a front baffle the size of the wall.

[mcgsxr]

I understand what you are talking about.  A flush (or nearly flush) baffle with the woofer firing through a hole the same size as the driver.

More work than it is worth in my mind, and also still prone to box vibrations building up in that cavity behind the baffle. 

I am happy with the grill I built into my wall in the basement. 

[JLM]

Sorry I didn't make it clearer, there is no port ( don't like ported subs ) the hole is directly over the driver. So basically I'm creating a front baffle the size of the wall.

If the solid front is tight against the subwoofer baffle and the hole is the same size/position as the woofer, then the acoustical effect should be minimal, but:

1. Unless you use a class D amp, heat build-up from the amp could be a concern;
2. To keep the solid front tight against the sub they should be secured together to avoid rattling/shifting (but that could induce vibrations to the house's structure);
3. This proposal doubles the material of the sub baffle (which many speaker builders do to reduce vibrations, but this would be of no sonic advantage;
4. Again back to me previous post, you'd have all the disadvantages but none of the sonic advantages of an infinite baffle design (which would be just a giant sealed sub);
5. And obviously maintenance, cable changes, taking it to your next place, etc. is more difficult with a built-in sub.

Like L98 mentioned, not having the solid front tight against the sub creates a whole new design with unforeseen acoustic consequences.  (A bandwidth sub is sometimes used to ameliorate room resonances at specific frequencies.)

[mikeeastman]

Thank you guys for the info, very much appreciated. seams that the grill cloth will be the easiest and most workable.       

I will be using a Dodd built classD amp to power the sub and  the entertainment center is vented.

[Letitroll98]

And thanks for the clarification Mike, "I see, said the blind man as he fell in the ditch".  And therefore I agree with your final assessment and everyone elses, very little sonic benefit, some possible drawbacks with installations and servicing, and the grill cloth idea is so much easier.  You might also think about making the grill cloth on a detachable frame for servicing the sub with cable changes or maintenance, or buying a new sub.  Maybe those magnetic frame inserts from Parts Express and others might be kewl.