plywood/mdf/etc...
One important point to keep in mind is that the stiffness goes up with the square of the thickness, so, 3/4" is more than twice as good as 1/2" (and 1" is 4x as good as 1/2", and so on...). Also, using layers of dis-similar materials tends to reduce resonance.
The closer a side of a speaker is to facing you, the more important it is to damp/stiffen it (somewhat) so I tend to add an extra layer to the front.
The stiffer your box is, the more bass you'll get. But, even a super stiff box made out of say, steel, will ring like a bell if it isn't well damped (so it will sound like crap).
Try playing sin sweeps and see if you can feel any parts of your cabinet that are resonating particularly and those are problem areas you should address - either by making the wall thicker, adding a brace, or some kind of damping.
One of the best things you can do is add internal braces to your cabinet design. The advantages from stiffening your cabinet almost alwasy outway the lost cabinet volume.
One important point to keep in mind is that the stiffness goes up with the square of the thickness, so, 3/4" is more than twice as good as 1/2" (and 1" is 4x as good as 1/2", and so on...). Also, using layers of dis-similar materials tends to reduce resonance.
The closer a side of a speaker is to facing you, the more important it is to damp/stiffen it (somewhat) so I tend to add an extra layer to the front.
The stiffer your box is, the more bass you'll get. But, even a super stiff box made out of say, steel, will ring like a bell if it isn't well damped (so it will sound like crap).
Try playing sin sweeps and see if you can feel any parts of your cabinet that are resonating particularly and those are problem areas you should address - either by making the wall thicker, adding a brace, or some kind of damping.
One of the best things you can do is add internal braces to your cabinet design. The advantages from stiffening your cabinet almost alwasy outway the lost cabinet volume.
Considering all this talk about cabinet resonance, what thickness do you guys think is best for the 871: 1/2", 3/4", or 5/8"?
Another question: if you discover that the cabinet strongly resonates at a particular frequency, is there any way you can tame it at that frequency?
Thanks for all the replies and for not minding me asking too much.
Another question: if you discover that the cabinet strongly resonates at a particular frequency, is there any way you can tame it at that frequency?
Thanks for all the replies and for not minding me asking too much.
If you all must say plywood, what kind should I buy? Birch? Maple?
If I choose to use veneered ply, external fasteners (i.e. screws) should not be used at all; I don't want to ruin the finish. A good option then is to use dovetail joints (which are held together by glue alone) instead of the common butt and miter joints. Is this feasible for larger cabinets?
If I choose to use veneered ply, external fasteners (i.e. screws) should not be used at all; I don't want to ruin the finish. A good option then is to use dovetail joints (which are held together by glue alone) instead of the common butt and miter joints. Is this feasible for larger cabinets?
coolkhoa said:
You can still use external fasteners if you use a plug cutter to cut matching plugs from matching plywood to cover the screws, and drill recesses for the screws beforehand.
As for dovetails (wow!) or even finger joints, I think you can only reasonably expect to use such techniques for 4 sides, and then some other technique for front and rear. I can't imagine the effort and patience it would take to do all 6 sides in dovetails!
Re: Re: plywood/mdf/etc...
Stiffness goes up with the square of the thickness, so the frequency will be increased.
While it's true that because the Young's Modulus of MDF is about 1/3 of typical plywood, it will resonate a lower frequency, it's Q is also much lower (in plain English: more "acousticly dead") so it is harder to excite the resonance and the resonance dies off quickly. The sound engergy transfered into the MDF is more quickly dissipated than with a plywood enclosure (it's converted to heat).
Hardwoods have a much higher Q, so while they are stronger/stiffer, they also resonate more so they are more suited to acoustic instruments where you WANT resonance, than to speaker cabinets.
Your best bet for reducing cabinet resonances is to layer materials with substantially different Young's Modulus, perhaps making a sandwich with a visco-elastic damping material in the middle. Bitumen is my favorite, but there are a variety of damping materials you can buy, usually with double-sided adhesive, or, the material itself is adhesive. Presently, I no longer have a source for rolls of bitumen sheet.
planet10 said:
Stiffness goes up with the square of the thickness, so the frequency will be increased.
While it's true that because the Young's Modulus of MDF is about 1/3 of typical plywood, it will resonate a lower frequency, it's Q is also much lower (in plain English: more "acousticly dead") so it is harder to excite the resonance and the resonance dies off quickly. The sound engergy transfered into the MDF is more quickly dissipated than with a plywood enclosure (it's converted to heat).
Hardwoods have a much higher Q, so while they are stronger/stiffer, they also resonate more so they are more suited to acoustic instruments where you WANT resonance, than to speaker cabinets.
Your best bet for reducing cabinet resonances is to layer materials with substantially different Young's Modulus, perhaps making a sandwich with a visco-elastic damping material in the middle. Bitumen is my favorite, but there are a variety of damping materials you can buy, usually with double-sided adhesive, or, the material itself is adhesive. Presently, I no longer have a source for rolls of bitumen sheet.
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