Again, I'm speaking from first hand knowledge. A vacuum on the top sheet 'penetrated' through 3 more sheets. That's only 14.7 psi, tops...probably less. So, it is porus. Now how much will it leak...can't say. I was just responding to your 'obsessivley sealed' comment. How long does putting a coat of varnish or resin on the inside take? How much does it cost? I can see not doing it on a trial box, but on the finished product, what can it hurt? Especially for someone as obsessed with perfection as you. I would expect more from you

Fortunately, you didn't actually use plywood, or that would open up a whole new issue. What you have in your picture is particle board. 30% seems high, but how much weight are we talking...an extra 3-5 lbs?

The PU dries fairly quickly...on par with RTV, and fumes are all but nonexistant.

And I again have to point out that you are wrong. Unless a long period of time is nearly instantly, and extreme air pressure is less than 14.7 psi.

Toby

 

Same thing that happened to powered EQ's...we got smarter.

Toby

 

You put forth the extra effort to solder all your connections...you're just counteracting yourself when you take shortcuts elsewhere.

There may be alot of little nit-picky things in car audio, but I can assure you when you put all those little things together, they add up in a big way. I've seen boxes made out of concrete.

 

I actually judged a car with a concrete box at Daytona, back about 91, or so. We all thought the guy was nuts, until we heard it. Box coloration is one of those things you can't put your finger on, until its just not there at all.

Toby

 

This is where I was going. You are a really smart guy, who knows lots more about car audio than many other people. I was just trying to throw out a couple more cheap, easy ideas, that can't hurt, and might actually help.

Toby

 

I must see this porus demonstration - but I think im confused as to the difference between plywood and particle board, im an engineer not a carpenter So is the porus comment towards particle board or plywood?

Am I wrong or did I just get the name of the wood wrong because I am certain that the wood I used in the above pics will hold well over 15psi with < 1% seepage. Can we destroy one of my old boxed at the meet and test it out?

 

I will try to demonstrate the porus experiment at the meet.

As for the wood...what you used is typically called particle board. It is basically glued together sawdust. Plywood is made up of several layers. If you look at the edge, you'll see them...looks like one of those crispy wafer cookies. It will also have a visable grain, and sometimes knots, etc. MDF is similar to partical board, except that it is made of much finer particles, or fibers, as the name, medium density fiberboard, suggests.

Plywood makes a crappy box because it is not as dense, and sometimes delaminates. Particle board is more dense, but not as dense as MDF.

My porus comment was aimed at MDF...I would think that particle board is similar, and plywood might be less porus. Not sure the seepage %, but it might be (probably is) minimal. I'll see if I can work up a couple of tests.

Again, all I was doing was offering another detail, to an obviously detail oriented person.

Toby

 

You really need some HDF.

 

a 24x48 board is like 18$ =/

 

it looks good to me way better than i could do.