Basic speaker building questions.

[evan]

I'm about to start my first DIY home audio project with the sealed floor standing version of Krutke's BAMTM. I've already got most of the parts but I'm a little fuzzy on some of the basic speaker building details.

I will be using some mat dampening material on the inside walls with some acousti-stuf in the bottom half as well. How do you attach your dampening materials to the inside of the enclosure and at what point of the build do you attach it?

The guy I'm building them for wants a high gloss black finish so I'll be doing some wetsanding and I'm not planning on using a removable baffle. Does that go against the norm? Should I cut the speaker/terminal cup openings before the finishing stage to make sure they're right before I invest time in the finishing, or should I do all the finishing before I cut the holes and hope I don't mess them up?

[---k---]

Hot glue or or spray adhesive will hold the dampening material on well. I assume by dampening material, your thinking insulation or foam. You can attach it whenever. It is probably easiest to attach before you glue the baffle on.

Most people don't build with removable baffles. Removable baffles just makes future new designs easier. I glue mine on last.

I would do all the cutting before you begin the finishing process. Get the speakers up and running and make sure you're happy with them before you go through the finishing process. Then remove the drivers and do the finish.

[evan]

Thanks for the reply. Yes, I was going to use some Sonic Barrier or similar over each inside wall and then some Acousti-stuf for the bottom.

Here's the order I'm thinking of. Let me know if I'm off line with anything.

-Assemble enclosures except for front baffle
-Cut openings for speakers/terminal cups
-Assemble crossovers and test in enclosures
-Remove speakers from baffle
-Round over inside of driver holes
-Install crossovers and sound dampening
-Glue on front baffle
-Paint
-Install drivers and terminal cups

[CarlsonCustoms]

I personally cut all holes in the boards before I glue ANYTHING just incase I mess up a cut. If I do I could just cut a new board out and redo it. I also clamp the whole box together before glueing just to make sure I dont run into any suprises when glue is drying.

Just a question, you are doing your first box as a contract for someone? That's brave, I wouldnt sell my first box since all my subsequent boxes are much better.

Good luck and post pics when done.

Zack

[Q45]

We purchased the dampening material from parts express along with the acuosti-stuf. 1 thing thing we noticed is that the adhesive on the back of the dampening material held great in some areas but not so good in others. Probably due to saw dust residue. So we just used a staple gun at the corners of the cut pieces, just so it didn't come off years from now perhaps when the bass was really moving some air. The we sprayed a light layer of 3M spray adhesive around the inside of the cabinets to kinda hold the acousti-stuff in place.

[evan]

Thanks for the input guys. These are for a friend of mine who is just paying for the material costs, but I'm sure he'll have no trouble telling me exactly what he thinks of them and getting me to redo something if he thinks it's necessary.

Can Acousti-Stuf be placed directly against crossovers, or do they get hot enough do damage to it?

[---k---]

I agree with above that I would cut everything first, dry fit, etc.

I've always fully assembled the box before moving on to the crossovers, but it doesn't matter much. You just will need to clamp the baffle on.

I would keep the fill away from the crossovers. I don't think it will catch on fire, but its a mess. Just keep it away.

Another tip, you can slightly oversize some pieces (will depend on how you glue up) and then trim with a router and a flush trim bit. I like to have the baffle fit over top of the bottom and sides, then I trim it exactly, then round the edges.

Also, make sure your crossovers are removable through the woofer hole. Use velcro and zip-tips to tie them down to the bracing.

[evan]

Attaching the crossover to the bracing sounds like a good idea.

Is it the size of the speakers that determines whether or not a double front baffle is required? I'll be using two 7" woofers that will be flush mounted into the 3/4" MDF. It will also be fairly tall (relative to a bookshelf speaker) at 44".

[Q45]

The paperwork that came with the acousti-stuf said it can go right up against the X-over. The material is not conductive. I just held it off a bit in mine, but I'm sure it's touching a little.

As far as the recessing a 7" woofer down into 3/4" MDF.... Think if you need to recess down possibly as much as 3/8" (depending on the woofer), how much meat are you going to have left to screw into? That driver has the most amount of movement and/or vibration.

[---k---]

We're all about overkill here. The thicker the baffle, the less it will vibrate. 3/4" thick is probably just adequate for your project. Like mentioned above, once you flush mount the woofer, that only leaves 3/8 behind the it. That should be enough to secure the woofer down. You get less in retail speakers. I can't see the woofer vibrating so hard that it would fail the wood; however, you may get some flexing that would produce distortion.

But DIY is about building better than retail for less money. Thicker is better. The standard PE box has a 1" front baffle. This sounds very reasonable to me. If it won't put you out much, double the thickness to 1.5" - just make sure you chamfer the backside so you get enough breathing room behind the drivers.