A7 replica cabinet material

**edharbur** · March 20th, 2010, 02:25 PM

After reading Panomaniac's thread on tweaking his A7s, I got to wondering if, rather than going to great lengths to stiffen my cabinets, it might be easier to just start fresh.

My company makes both custom cabinetry and carbon fiber race car components, so I have access to a lot of technology, and the A7 cabinets just aren't all that big a deal.

What material would be best? There are lots of options - very thick MDF - I can buy or laminate any thickness I want, the speakers would be VERY heavy. How about 2 layers of 1/2" MDF or plywood laminated to a 1" foam core? Very stiff panel, reasonable weight, and, I guess, pretty acoustically dead. Thick plywood? Again, I can buy or laminate any thickness I want; weight becomes an issue, and I'd guess that it wouldn't be as acoustically dead as the ply-foam-ply laminated panel.

Any thoughts?

Ed

**oface1** · March 20th, 2010, 03:57 PM

My vote is carbon fiber, bubinga, and Madagascan ebony...... ;^)

-chris

**Panomaniac** · March 20th, 2010, 05:06 PM

Well you can get all fancy, but my vote would be for bamboo plywood. It's expensive, but very stiff, very dense. Seems to have rather good acoustic properties.

If you can't find it or don't like it, use the densest, best marine ply you can get. And brace it.

There is fancier stuff to build from, but I doubt you'll do better. Sand filled plywood walls would be the ultimate. Kinda hard to do on an A7, but if you are up for a challenge....

**Audio_by_Goodwill** · March 20th, 2010, 05:30 PM

Originally Posted by edharbur

After reading Panomaniac's thread on tweaking his A7s, I got to wondering if, rather than going to great lengths to stiffen my cabinets, it might be easier to just start fresh......

Maybe, but I'd think no matter what material you'd use, you would want to have bracing.

Skip the MDF. It's cheap, but flexible. If I were going light weight, I'd think some sort of honey comb core would do well, but I really don't know how it would compare to other materials.

**Altec Best** · March 20th, 2010, 05:45 PM

Are these cabs for your work enviroment still, if so just use birch plywood, they would be cheap enough.If you want to build for your home could always get Baltic Birch and it comes in differant thicknesses 1" well braced would do very well.

**edharbur** · March 20th, 2010, 06:29 PM

Well, I've thought about carbon/aluminum honeycomb core, but fragile and expensive. Bamboo ply is unstable - I've got left over material from a job 2 years ago that spontaneously splits while sitting in the rack. Baltic birch is easy and cheap, but is it the best I can do? If I'm going to brace, I might as well just modify what I have. If I brace, the braces will effect the air movement inside the cabinet. Does it matter? I don't care about the weight - within reason. If a 3/4" plywood speaker weighs 175 lb (which I've read, but don't believe) then a 2" MDF speaker would be 4-500 lbs. Yikes. These speakers would definitely be for the shop, and I definitely love the industrial look. That being said, my fiance has asked if I can get a pair for her very fancy living room, which is where the original cabinets would go if I opted to build myself a set of killer cabinets. Whoa!!!

**Todd W. White** · March 20th, 2010, 06:44 PM

I'd build Magnificent's for the living room if it were me...

**bfish** · March 20th, 2010, 07:45 PM

continued from "ooops... wrong thread...

Hi Ed,
Welcome! You're ahead of the curve, having experience and confidence in materials and construction. There are a couple of schools for boxes; brace/make rigid at intervals that ~remove resonance in the passband, or absorb the energy with constrained layers (like your "Oreo"/foam idea). I prefer the former... rather not waste the HE drivers on wiggling a box.

Unless you have a fetish for vintage plywood, tweak whatcha got for a "feel" of it. Bracing/filling the flares yeilds the best return, then the vent. If cosmetics aren't a concern, thru-&-thru 3/4" dowels/all-thread are easy and effective bracing in the reflex area.

**valhallax** · March 20th, 2010, 10:09 PM

13 ply 19mm russian white birch and brace accordingly. if i ever move out of the 210 in the living room stage it would be 820's in their stead. loaded with 515b's and supplmented by subs

**Mustang Marvin** · March 21st, 2010, 09:57 AM

Bracing?
I hear so much about the need for bracing, and just as many suggestions regarding the method. Vertically on the inside or outside? Horizontally inside? bracing the horn (many methods here).

And how about the volume of air inside the cabinet after bracing. Does the diminished air volume inside the cabinet affect the sound? I have seen pictures of so much cabinet bracing inside the box and thought to myself, surly that must affect the sound. My A7's need bracing, but I am confused as to how much and where.

My A7's are constructed with the flimsy 5/8 inch plywood. And a poor grade of plywood at that. I wonder if I should brace them to the max, or start over with a more ridged 3/4 inch plywood. As I consider more costly drivers I wonder if i'm wasting my time and money with a poor cabinet. Are there any links regarding bracing in A7's?

Your thoughts and advice are appreciated...