[Popms]

I've got two projects going at one time Ellis 1801 speakers and Sonic Craft Scc 300 sub I want to make the sub with 1.5 mdf but can only locate .75 mdf is there any problem glueing 2 together to make 1.5?

[Brian Bunge]

Gluing 3/4" MDF together will work fine.  I've done it several times.  I prefer to build the inner box, glue oversized panels on and then trim them down to size with my router.

[PSP]

OK, let me be totally clear that I'm not a speaker-builder expert, so this is opinion only... but it seems to me that gluing two 3/4" sheets together will give a much stronger structure than a single 1.5 inch sheet.  I also think that you have the opportunity to select a glue that will increase the damping between sheets... so use a glue that sets up with just a little  remaining flexibility rather than one that sets up rock hard?  Just a thought.

Peter

[nathanm]

Maybe you could contact cement a sheet of 1/8" thick foam rubber barrier of the various kinds on the market between the MDF boards?

[shokunin]

1.5" MDF will typically be available via special order.  Even at cabinet shops where 1" MDF can be found, anything thicker is special order unless you go direct to a distributor.  Glueing together multiple .75" pieces are fine.  I don't think you'll want to single-handedly handle/lift a 1.5" MDF 4x8' sheet, it'll be about 150lbs!!  

As for glue, people have used anything from white elmer's craft glue, titebond I and II, G2 flexible epoxy and even Alex Plus caulk sealant.  Either way there will be sooo much glue surface area that almost anything will create a strong bond.