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| Re: skywave's 3Pi subwoofer build [message #71620 is a reply to message #71617] |
Thu, 01 March 2012 15:02   |
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Wayne Parham
Messages: 18675
Registered: January 2001
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Illuminati (33rd Degree) |
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I like using T-nuts for the larger drivers, 10-32 size with button head or hex head screws. Wood screws are fine for dome tweeters and small cone speakers, but I do like something a bit more substantial for horns and larger prosound drivers. Some people prefer threaded inserts - and those are great too - but I've worked through all the problems you commonly run into with T-nuts so I'm good with them. The trick is to get good T-nuts (like from Midwest Fastener) and pull them into the wood before assembly.
Don't beat them in with a hammer, and don't pull them in place when you're putting the speaker together. Use a washer and a sacrificial screw (or three) to gradually pull the T-Nut in by tightening it down. Only use the screw to pull-in three or four T-nuts, then discard it and get a new one. I also recommend a drop of PL adhesive on each T-Nut to hold it firmly in place.
Don't skimp on this step. You are planning for the T-Nuts to last the life of the cabinet, and to provide you with trouble-free, serviceable access. If you install them as I've described, they'll be that for you. But if you don't, they can be a real pain. Every time I hear of someone complaining about T-Nuts, they're in one of these categories:
1. Tapped the T-Nuts in with a hammer - The tangs bent, and the T-Nut is loose, held only by the screw clamping force. So when you loosen the screw, the T-Nut spins. Makes it really hard to get the speaker out for service.
2. Didn't put a spot of epoxy on the T-Nut - Even if the tangs go in straight, a few knocks on the head of a partially loosened screw can make the T-Nuts come loose. They hold pretty well, but it's easy insurance to add a dab of PL adhesive during assembly. Just a dab though, don't get any on the threads.
3. Pulled the T-Nuts in with a screw, as described, but used the same screw over and over again, damaging the T-Nut threads - Sacrifice the screw, only use it to set two or three T-Nuts. You don't want them to have damaged threads, 'cause once they're installed, they're permanent.
Put 'em in right, and they'll last a lifetime, giving you trouble-free serviceable access. But put 'em in wrong, and you'll be frustrated to no end when it's time for a woofer to come out.
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| Re: skywave's 3Pi subwoofer build [message #71647 is a reply to message #71634] |
Sat, 03 March 2012 10:40 |
skywave-rider
Messages: 104
Registered: May 2009
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Viscount |
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| Psychoacoustic wrote on Thu, 01 March 2012 23:03 | Right, not the one on top- that won't interfere, but the hard laminated paper gasket below, which I queried with Wayne. Perhaps I misinterpreted his reply and its not meant to be there.
I used scrap MDF for the spacers- little bit rough, yes, but the cabs haven't been veneered either!
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I just got the woofer, thanks, Wayne.
I see the hard laminated paper gasket referred to by Psychoacoustic. Wayne, since the bottom of the woofer flange is perfectly flat, is there harm in not using the hard paper gasket there? I would use a weatherstrip type tape for a seal instead. The reason is to keep the woofer from protruding as much as is practical. I would leave the top gasket to mount the metal grill on top of so there is enough clearance between the surround roll and the grill.
Regarding the mounting holes in the woofer flange, do I need to worry about the edge of the surround which covers almost 50% of the hole?
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