[WmAx]

People here have covered very well the practical reason for MDF(cost, consistency and easy to paint).

Personally, I despise MDF because of the horrid dust and it's weak structure and high weight that gains you nothing in itself that is substantial. I use MDF only when I am painting a surface now.

The high grade 13 ply birch is stronger/stiffer and weighs less and it lacks the horrid MDF dust. You can more easily achieve a specific stiffness per area using less bracing, and with far less weight, than a MDF cabinet.

If you want a true very low resonance cabinet, you have to do more than just use a good base material and moderate bracing, anyway. Standard construction method for cabinets used by most DIYers and Hi-Fi manufacturers will not give you a low resonance cabinet; you will have to go to more extreme methods to effect a low output cabinet. I can state this with high confidence based on my own research and experiments/measurements. I find it takes a surprising amount of effort to substantially reduce cabinet talk; at least surprising to most people compared to what they presume will effect low cabinet talk.

-Chris

 

[WmAx]

Thus when you DIY you can add a lot of internal window braces. No more than 6" span without an internal brace. The resulting resonance of the sidewalls is raised in frequency to the point that they do not get activated. Going to this type of extreme is rarely done for a commercial product -- but DIYers can obsess. :hyper: :sweat:

This is still going to leave the resonant points within the passband unless you are talking about only a woofer cabinet section. A 6" span matrix brace on all axises on 3/4" MDF would place the first resonant panel mode in the 400-550 Hz range, I expect. The typical window braced enclosure with braces every 8-10" typically has it's first resonant panel vibration roughly in the 180-300Hz range.

On top of the resonance, even more troublesome, regular cabinets will have a wide band of high vibration through the entire audible bandwidth. One needs to not only address the huge resonant spikes, but also the high over all vibration level of the cabinet panels.

Of course, I presume the point is a no-hold-barred reference grade speaker. For a HT speaker, or a speaker for less than critical listening, I don't suppose cabinet talk needs to taken as a very high priority.

-Chris

 

[WmAx]

Plywood will vibrate more than MDF and allow more midrange energy to bleed out of the cabinet through the walls, which is bad for the sound of the speakers. Hence the suggestion to use more bracing and dampening materials.

Not going to argue with anyone else out there, this is just somethign I came across..
I guess I'm just playing Devil's Advocate. :devil:

I think one needs to qualify the statement you quoted. Sure, regular AC grade softwood ply is not a great choice. But we are talking about 13 ply void free hardwood birch plywood in this thread; a different animal.

-Chris