[django11]

On my (soon) upcoming n2s or n3s build I was wondering what the preferred material would be for the enclosure.  I can get 1" thick 15 ply Russian birch plywood locally.  Would this be a better choice than 3/4 inch material or better than 1" mdf?  Would it reduce cabinet resonance? 

[nickd]

15 ply birch sounds WAY better than mdf. Use it if you can get it.

[dBe]

15 ply birch sounds WAY better than mdf. Use it if you can get it.

+1 on the Baltic birch.

A couple of thoughts on enclosure materials.  Baltic birch is not available in some areas.  An alternative to standard MDF is a product that I have been using for a long time:  MEDEX -
 http://www.sierrapine.com/index.php?pid=68

It is denser and stiffer than MDF with a harder surface finish.  The big advantage is moisture resistance.  It does not exhibit the tendancy to telegraph butt joints (which most of us use) over a period of time due to humidity changes.  We've all built enclosures that look great and in a year glue creep has allowed the panels to move and you can see that ugly bump in the veneer or paint job.  Out here in the great soutwest our humidity will go from 6-8% in the winter to 60-80% during the summer monsoons.  Medex stays stable and pretty joints stay that way.

A killer enclosure material is laminated Baltic birch and Medex.   

Dave

[Peter J]

Sonically, I don't think either one could be considered superior. I do know something about the characteristics of both. One could use these both to advantage.

As far as density and weight for a given thickness, MDF is king. The way I understand it, density has a direct affect on resonance.  I don't know if this is universally true with materials other than those you mention.

On the other hand, Baltic Birch has an advantage when it comes to rigidity and stength, so it would be considered the stronger of the two, but lacking the sheer density of MDF.

One thing that's not considered in the above descriptions, but affects cabinet resonance, is bracing. A poorly braced cabinet built from the most dense material, will exhibit more resonance than a well braced cabinet built with something less dense.

To me, it seems like a design issue as much as material choice one.

One speaker I built was the Northcreek Rhythms, which used MDF for the exterior shell, with B Birch for internal bracing. Seems like that marries the best qualities of both.

[Danny Richie]

Peter pretty well nailed it.

Although, when adding braces I'd recommend braces that hit the sides, front, and back rather than long braces that hit side, top and bottom. The tall vertical braces often create an early surface reflection problem.

[django11]

Would solid wood be the same as birch plywood?  I just remembered that I happen to have a bunch of 1 1/8 thick birch boards hanging around.  I would have to plane them to an inch or so.  Would this be an acceptable material, lined with No Rez and sufficiently braced?

[dBe]

Peter pretty well nailed it.

Although, when adding braces I'd recommend braces that hit the sides, front, and back rather than long braces that hit side, top and bottom. The tall vertical braces often create an early surface reflection problem.

Yep,

I turned George Short on to Baltic birch back in the early 90's.  He had been using standard void free fir plywood up until then.  The long braces were ones that went from side to side with large holes in them for decompression.  His stuffing scheme works really well in controlling the reflections and the cabinets are unbelieveably dead.  I like George's speakers.  Very dynamic and very easy to listen to.  George is/was very good for audio.  I hated to see him close up shop for DIY guys.  I bought me first really good caps from him.  I was using PIO and mylar until he came along 20 years ago.  He makes/made the best inductors that I have ever used although the foils are very, very close and maybe a little better in the mids... maybe

Dave

[Danny Richie]

Would solid wood be the same as birch plywood?

 

Solid woods are much more resonant.

[django11]

 

Solid woods are much more resonant.

Crap, I was getting excited about using that...   It isn't  just about density then because birch is very similar to mdf.

 So, is the B birch ply acceptable or should I set my mind on using mdf?

[Peter J]

Yep,

I turned George Short on to Baltic birch back in the early 90's.  He had been using standard void free fir plywood up until then.  The long braces were ones that went from side to side with large holes in them for decompression.  His stuffing scheme works really well in controlling the reflections and the cabinets are unbelieveably dead.  I like George's speakers.  Very dynamic and very easy to listen to.  George is/was very good for audio.  I hated to see him close up shop for DIY guys. 

Dave

Dave, I was bummed to read that Northcreek DIY was shutting down too, but from the looks of his website, it' looks as if he's still selling kits.

[Peter J]

Crap, I was getting excited about using that...   It isn't  just about density then because birch is very similar to mdf.

 So, is the B birch ply acceptable or should I set my mind on using mdf?

On  a microscopic level, the structure of lumber vs MDF is very different. Solid wood looks like a sponge in comparison. MDF is way more dense and consistant in it's density, not to mention stability.

Why not use both? Shell in MDF, internals with B Birch, or a lamination of the two?

[Danny Richie]

A combination of MDF and Birch ply is ideal. Anytime there are layers of different densities and different resonance frequencies is a good thing.

Better still is a sand layer. See the pics to the sand box: http://www.audiocircle.com/index.php?topic=53675.0

[tg3]

Would solid wood be the same as birch plywood?  I just remembered that I happen to have a bunch of 1 1/8 thick birch boards hanging around.  I would have to plane them to an inch or so.  Would this be an acceptable material, lined with No Rez and sufficiently braced?

Solid wood also tends to move (shrink, expand, warp), and is not a good material for loudspeakers.

[nickd]

OK if you guys are going to get all fancy, then go multi ply birch 3/4" on the outer and  1/2 particle board on the inside as a liner. It makes the best sounding box I know of. MDF is the easiest to work with for sure and you get a nice finish but sound bounces off it and it does not "Sing" as well as Birch Ply or solid woods.

A box can sound a little too DEAD like a Wilson or be too resonant and boxy like the cheap warehouse brands (mostly Chinese in origin). Most musical instruments are tuned. loudspeakers should be too. The box should contribute to the music not sing along off beat with a different tune. sound bouncing around inside the box always comes out somewhere (through the cone, box walls or port) but never in tune or in correct time.  for the record. I'm using 15 ply baltic birch for my Super V build. And there is no box to cause problems

[dvenardos]

Okay, I think what Stephen is asking here is (considering the fact that the birch is already veneered) how would a N2S/N3S built to spec compare with the two options?

[django11]

OK if you guys are going to get all fancy,

Dvenardos has got it right.  I let this thread get away from my original intention.  I shouldn't have named this thread "preferred enclosure material"...  Especially not around here .  Actually, I don't want to go all fancy.  The doubled wall stuff and sand in between will make the enclosure much too big for where I want to put it. 

The reason I brought up the Baltic birch (besides the fact that Danny actually has plans here  for a BB enclosure)  was for the simplicity of the build as the BB would be the finished material.  Veneer on mdf would be overkill in my situation and a painted box does interest me.

  So what if I had named it "acceptable enclosure material"?