Wood type and thickness for building speaker cab

Apparently MDF is the best from a sound quality perspective because of its density , it doesn't resonate like ply. MDF is one and a half to two times heavier than ply though . So an MDF cab will weigh a tonne.
Plywood is the strongest and most durable. Thickness would be about 17 or 18mm. CD grade plywood would be fine. If you want a really flash cab a sheet of hoop pine plywood would be nice, it's very nice to work with , takes fastenings really easily , no knots and has a smoother surface. Hoop pine ply is at least double the price of CD structural ply . Depends on how much you want to spend eg 18mm CD - $65 a sheet or 17mm hoop pine $160 a sheet.
Chipboard would be the cheapest way to build a cab.MDF is similar in price to chipboard.
Either Mister plywood at Hornsby or Bryunzeel plywood at Brookvale have the best ranges of products.

 

MDF is commonly used for speakers, but it turns to mush if it gets wet.

FWIW, Avatar uses 3/4" void-free plywood for its enclosures.

The carpet covering you refer to is called Ozite, and it's not heavy at all. Nor is it real carpet, as in the stuff you'd put on the floor.

Check out http://www.partsexpress.com for supplies and info. They've got pretty much anything you'd ever want.

 

MDF does not turn to mush if it gets wet. Particle board turns to mush when wet. There is a huge difference (price and weight) between the two. I've left MDF outside in the California winter (rain) for a couple of seasons without it turning to mush.

MDF weighs 49 pounds per cubic foot. A 4x8 x 3/4" (19mm) sheet is 2 cubic feet or 98 pounds. Baltic Birch void-free ply and Apple Ply weigh less, typically 32 pounds per cubic foot.

MDF is less resonant than void free plywood, and much less resonant than construction grade. Large cabs or high performance drivers are better suited in MDF, despite the weight. X-Y-Z plane bracing will help in all but the smallest of cabinets.

 

Another suggestion is to use a double thickness of wood for the front panel (glued and clamped or screwed together). The extra stiffness will improve the sound, but also increases the weight.

jd

 

For bass amp cabs, I'd use 3/4" plywood with some nice, light, internal bracing.

For hi-fi speakers, concrete works well. j/k I'd use 3/4" or 1" MDF, double-thick on the front. Using a thick front like that also lets you round the edges and counter-sink drivers more, helping with diffraction issues. Not so much an issue IMO with bass cabs.

 

look at high end cabinets. and even high end combo's. most of them are made from sheet birch, fi you can get it its great

 

Even though Geshel was probably only joking about using concrete, it serves as a reminder that we will always have to deal with a trade off between weight and sound when choosing timber. Personally I'm not fit or strong enough to make my cabs out of MDF. I vote for plywood.

Thickness depends on wether or not the speaker is dealing with low frequencies. I used 20mm on my 2x10, but it does nothing under 75Hz. I used 25mm on my 15 and that's probably as thin as you would ever go.

 

I'm planning to build speaker cabs for some full range Fostex.

The original design calls for 18mm thick ply.

The hardware store only stocks 12mm ply.
I assume I would have to recalculate all the dimensions in this case,
and then still be a bit off because the machine removes 3mm between cuts.

Would you double everything and use 9mm ply glued together?
or use 18mm solid for 5x the price?
...or keep looking at other hardware stores?

 

I just recently built a BFM design 212 cabinet, all 12mm baltic birch plywood. It has internal bracing also made from 12mm baltic. It sounds great, doesn't have any cabinet mechanical resonances, and weighs less than fifty pounds.
Simplexx 212 build - BillFitzmaurice.info
Simplexx 212 - BillFitzmaurice.info