How to mount a driver in a subwoofer

[SpeakerBob]

I can't see the problem with t-nuts and mdf..😕

Just use a bit of contact adhesive before you hammer them, make sure your holes are in the right place and theres no problem...

I've got about 50-60 bolts into t-nuts on mdf sitting in my room, no probs..


If you're that worried glue a plywood 'washer' before drilling, so that the t-nuts got something more than mdf to grip.

Cheers

Rob

 

[johninCR]

Simon,

I don't know what you mean by "chamfered" and I don't know about bits, I'm talking about 5x5cm pieces of plywood or something. If the edges are rounded or something on the inside, just use a bigger piece glued to the baffle for strength.

I could foresee your problem with my maelstrom, so when I was building it I glued a piece of 3"x3"x2" behind each screw hole and used 3" screws.

Those T-nuts have given me pains in the past when the nut part comes loose before it's all the way tightened. Then you have to figure out a way to cut it off without damaging the driver.

Now that I'm using open baffles, those kind of problems don't exist. You can change something in a crossover in seconds....get to the back of a driver to change wiring config...etc. It makes tuning stuff by ear fun and easy.

 

[SimontY]

I can't see the problem with t-nuts and mdf..😕

I don't know what you mean by "chamfered" and I don't know about bits, I'm talking about 5x5cm pieces of plywood or something. If the edges are rounded or something on the inside, just use a bigger piece glued to the baffle for strength.

Sorry guys, I obviously didn't explain myself very clearly there. Chamfered means rounded off, probably a woodworking term I remember from GCSE design and technology! The inner edge of the driver cutout is rounded, done with a router, the way the outer edges of the front baffle are often done.

The roundedness means the inner-most part of the cutout has very little MDF thickness, and because it is rounded, and especially as the speakers are totally built, it would be nigh on impossible to fix t-nuts into it. T-nuts IME require hammering in, so that they cannot slip when the bolt is tightened. There is too little room to slip a hammer in and hit things - they are 13L enclosures.

My other problem is how close the original holes are, and necessarily the new holes will be to the edge of the baffle ie. where it meets the next cabinet join. There is barely enough room to slip in a piece of wood behind there. My other concern is that the bolts may not be long enough to go through the MDF *and* another piece of wood. The MDF baffle is 22mm thick already 🙁 😕 😕 😕

 

[johninCR]

Just get longer bolts and glue thicker wood where the six free holes are. On the 2 sides close to the joints just glue the pieces of wood to the sides as well as the baffle. The pieces of wood can extend into your circle some without getting in the way of the basket to ensure a large enough wood area for the Tnut to have good strength in front of it. The space caused by the rounded corners will be unimportant. Use wood glue and clamps. If you don't foresee taking the driver out to make changes, just use 3 inch screws and it will still be stronger than the original MDF even with tnuts. Be sure to drill tap holes so you don't split the wood if you use screws.

 

[SimontY]

Sound advice John, thanks!

I think I will stick some bits of wood in there as you suggest, or at least try! Wilmslow Audio (www.wilmslowaudio.co.uk) sell m4 t-nuts and 40mm long bolts, which should be enough to go through both pieces. I really wanted allen bolts, but the ones they have are only 30mm long, not enough 🙁

Screwfix don't sell 'em either, http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=82224&id=16785 -that's the kind of thing I'd like to see, but only very short ones seem to exist.

 

[BAM]

If you suck up your dust cap into the vacuum, you can get replacements from Parts Express.