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View Full Version : Mdf vs bb vs pb question



bldozier
10-21-2016, 03:58 PM
In my next incarnation, the 4344, id love to keep away from mdf, its just not fun and to demanding. Pb is not with in
Reason, from my understanding, being the least dense,
1" pb was used in early cabinets at this size, so would a 3/4" mdf or bb equate to 1" pb. I have not seen or read other then maybe once or twice it it being used in place of 1" material.

I have to face glue my pieces my local wood distribution center has been closed. I can do 1/2(9ply)2 or 3/4(13)+1/4(5) or 1/2+1/4 or 3/8(7ply)+1/2

Can anyone explain the density of pb vs bb vs mdf, and could I use a 3/4 mdf combination for the 4344.

loach71
10-21-2016, 05:44 PM
My favorite laminate for speaker construction is:

1/2" Baltic birch plywood laminated to 3/4" MDF laminated to another sheet of 1/2" Baltic birch plywood. I use this for the tops and sides of the enclosure.

for the front baffle of the enclosure I use 1/2" Baltic birch plywood laminated to 3/4" MDF laminated to another sheet of 3/4" Baltic birch plywood. The 3/4" Baltic birch plywood is on the inside of the baffle -- it gives strength and stability as a substrate from which you can attach TEE-nuts.

The back baffle is the same as the front baffle. You choose which Baltic birch plywood plywood faces outward.

Your cabinets will be acoustically dead -- but very heavy. Apply panel buttresses as you see fit. You can test for their necessity by the "knuckle rap" procedure on the box when it is finished.

Some may say this is excessive, but when building your own cabinets, excessive is "just good enough."

bldozier
10-22-2016, 02:40 AM
Ok I will try it on both my jbl projects
Brian

loach71
10-22-2016, 01:26 PM
Ok I will try it on both my jbl projects
Brian
Brian:

The MDF acts as MASS to help move the resonant frequency of the panel out of the audio passband.
The plywood adds dimensional stability and acts a nice substrate from which you can add veneers.
Make sure to apply yellow woodworkers glue to the panels with a paint roller to get 100% coverage.
I lay the panel on the floor and shoot drywall screws into them every foot or so to make sure the panels clamp
down on each other tightly during the lamination process. After a day or so of glue dry, you can remove them.
Laaving the drywall screws in the laminated panels will cause sawing to be a great hassle.

Like I said, the resultant laminated panels will be HEAVY -- but they will be acoustically DEAD.

Good luck with your construction project!

bldozier
10-22-2016, 03:28 PM
Thanks laoch711,
Found some 1/4 & 3/8 for the 4315 project, the 3/8 will go in while the 1/4 out. 3/4 mdf is being used. ��
The same seller also has 1/2 bb, which I will purchase later for the 4344 cabinets.
Brian
Im using a dado joint, fwiw.
Im going to fix the edges with wood putty before gluing not just fill gaps, also saved some shavings from the Stanley 45 to help the gaps, on tops and bottoms. I will use pl premium upon completing that.
More later.
74170

Lee in Montreal
10-22-2016, 03:45 PM
To keep these flat panels from vibrating, just brace them on at least on two axis.
Proper bracing + 3/4" MDF + 1/4" finishing plywood will make you happy.

As for the MDF, it is... Medium Density Fiberboards. You can also have High Density Fiberboards for extra $. Much heavier and denser.

http://www.ohio.edu/people/schneidw/audio/images/rbr/rbr-damping_wallsml.jpg

http://1.bp.blogspot.com/_W1x0C8rk2XA/TBJKkRWbXoI/AAAAAAAAAFs/5R2w5AApS4E/s1600/Response-bracing.jpg

http://i241.photobucket.com/albums/ff260/Antikythera/bracing-1.jpg

Ed Zeppeli
10-24-2016, 09:45 PM
The Ace of Brace!