[azryan]

-T-nuts should be used to grip into the MDF versus using wood screws to hold the drivers.

Are you saying 'always' use T-nuts then? If so I disagree esp. when the subject is small woofers and near weightless neo panels.

It's a proven fact that you don't need T-nuts for small drivers.

You don't even really 'need' 'em on large drivers either but in the case of large subwoofer drivers I say 'might as well, just in case' -'esp. in downfiring subs like mine 'cuz that's simply a LOT of weight to put on to 8 screws into MDF.

Really though.... I know for a FACT that I took ALL the bolts out of my two downfiring 15" Adire Tempest subs (Very heavy drivers I think you can agree?) and the drivers didn't fall out. They didn't even move at all!

They were bonded to the MDF with the double sided foam tape I put around the woofer frames as a sealer.

I REALLY had to work my ass off to get the woofers out to re-wire them.

When I took out the 7" drivers in my Newform 645's all 4 were bonded to the cabinet simply with paint. I almost ruind the drivers working so hard to get them free.

So obviously not only did I not need T-nut's/bolts in the extreme subwoofer case or in the lighter 7" woofers...

Clearly didn't need any bolts or screws at all! hehe

 
If screws don't work in general... wouldn't we see the failure of the screws used in the bazillion speakers out there that have screws attaching drivers to MDF?

It seems like this should a 'case closed' by now since everyone seems to agree that MDF works great and plywood can be used but with no advantage like less resonance of weight reduction -which was the original thread question.

[bubba966]

...or are you suggesting to drill right through the baffle and mount the T-nuts on the inside of the baffle?

Yes, that's how T-nuts are supposed to be used. I've never heard of or seen anyone ever use them on the outside...

[azryan]

-I read elsewhere that T-nuts don't grab into MDF very well and I have come across a number of comments from people that used ply for the 'outer' box for this very reason. Are you guys suggesting that this is unnecessary? ...or are you suggesting to drill right through the baffle and mount the T-nuts on the inside of the baffle?

I'm not sure you get how a T-nut works.

To answer your question... Yes, using plywood for the outter layer would be totally pointless if you use T-Nuts.

T-nuts are where you have a bolt that goes through the cabinet (doesn't make a diff what the cabinet's made out of 'cuz it's not really being held much by the cabient.

The actual 'T-nut' goes on the inside of the cabinet. It's simply a 'nut' that has a frame around it with some spikes that dig into the MDF or whatever you use so the nut can't move.

Some people do complain that the MDF can chip when you hammer the T-nuts into it but I've used a LOT of T-nuts in MDF and there's nothing to worry about. If anything you can add a little Liquid nails around the nut so make double sure it won't ever move.

Some people use plywood on the 'inside' layer 'cuz it will grip the T-nuts better but in this case you only need a REALLY thin layer of plywood and can be any cheap crap.

That's overboard IMO though. A waste of time and money for no benefit.

Hurricane nuts are very similar to T-nuts but the frame doesn't have any spikes to dig in, the nut section has the gripping part. Hard to explain though. Look at PArts Express if you want to see what they look like.

I never used 'em but you can see that they're a good idea. A clever reworking of the T-nut idea and great for MDF.

T-nuts are still cheaper though and work great so I'd jsut stick with those... but like I said... it's all overkill for most any speaker drivers. Certainly no need for all the trouble it'd take on a pair of Alphas.

I wouldn't worry about having to get the woofers out if you use screws. At most you'd have to do it one, maybe two times but probably not ever at all and the screws will hold fine through all that.

You can add a little wood glue or other tricks to make sure the screws hold if you have to take drivers out over and over again -but why would you right

[DSK]

Yes, that's how T-nuts are supposed to be used. I've never heard of or seen anyone ever use them on the outside...

I did, on the bottom of a cabinet when fitting adjustable feet with threaded legs. It meant that nothing had to break through the visible internal surface.

Will tightening M3 bolts (obviously without the driver fitted yet) be sufficient to pull the T-nuts fully into the back of the baffle (and seal the hole) without resorting to hammering them into the inside of the baffle? Due to internal bracing I can't access the inside of the baffle with a hammer from the back (amp hole).

[bubba966]

It's very hard (usually impossible) to pull a T-nut into place by using the screw. I'm not terribly familiar with metric screws, so I don't recall how big an M3 screw is.

If you can't get acess to the nut with a hammer (or can't install the nut before assembly) use something like this.



This is one of those Hurricane Nuts that azryan was mentioning. Those type of nuts can be pulled into place using the screw. Still might not be easy though...

[shokunin]

Are you saying 'always' use T-nuts then? If so I disagree esp. when the subject is small woofers and near weightless neo panels.

I said, one "should", like a recommendation, defintely not "always".  Of course you don't HAVE to use t-nuts.   T-nuts are recommended if you expect you'll be constantly removing and reinserting drivers (regardless of size) or if need that much extra tightening pressure.  If not, no worries, use screws.

I use t-nuts all the time when I make my woodworking jigs, you never want to take the risk of something getting loose or ripping out of MDF when you're near a running blade.  For speakers, screws are plenty tough, given you won't be taking them in and out 50 times.

DSK,  You can use threaded inserts but they'll probably be no stronger than simply using a coarse screw.  I've never tried using a threaded insert into MDF, but in real wood, it's a tough to do right, I use my drill press and slowly rotate it straight down into the wood.

[DSK]

You can use threaded inserts but they'll probably be no stronger than simply using a coarse screw

That's true, but as others had suggested that strength was not important to hold the driver/amp in place, I figured that the bolts would be far easier to insert (than wood screws) without slipping and sending the screw driver throught the sub driver  

[Christof]

DSK,

I'm a serious fan of Huricane nuts.  They have completely replaced t-nuts in our shop.  They are very easy to insert without banging on the piece and they stay put.

Christof