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T nuts n boltz

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teeth View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote teeth Quote  Post ReplyReply Direct Link To This Post Topic: T nuts n boltz
    Posted: 10 May 2022 at 7:18pm
What T nuts n bolts?

I'm gonna sort out my driver situation! I've got some fanes woodscrewed in to some HD15's... that's not right.

So looking to make the jump and get some T nuts and bolts...

I've got some 18's on the way that will need them too.

Obviously all speakers are different, but what are you using? Anything you'd recommend? Avoid?


Found these, M8 looks pretty big and 40mm quite deep!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2022 at 11:16am
I prefer threaded inserts to tee nuts. Little bit of PVA in the hole before inserting make them quite strong enough to hold a speaker. either way M8 is overkill and you might struggle to get the bolts through the speaker chassis - M6 is fine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2022 at 5:32pm
 Just to be controversial and only if the baffle is plywood , Why would it be wrong to "just" use  screws? The way I see it (feel free to disagree) is
Using T-nuts next to the edge of a baffle cutout is always problematic as the flange often protrudes over the cutout and securing them from not pushing out ( make the hole small enough to jam them in helps).T-nuts are good for some things but are only a traditional way of securing a speaker because it seems to be a more respectful way of treating an expensive component.
Threaded inserts are very nice ,but no good next to a baffle cutout.
Clamps are a very poor solution but do fascilitate moving the problem further away from the baffle cutout,
Fane and others have made wide flanges on speakers that solve all these issues (JBL are terrible for this)
There are so many "Hi-tech" fixings (with torx heads) available these days that I can only see  advantages in using threads directly into plywood . they  will also never rattle loose.


Edited by Tinnitus Rex - 11 May 2022 at 6:41pm
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2022 at 10:28pm
Remove your wood screws a few times and see how well they go back in.

T-nuts or threaded inserts are used because you apply tension to the load from both sides, and the baffle gasket doesn’t get torn up by a screw thread mating directly to it.

If they’re fitted properly - glue and/or small screws to prevent rotation - and the right type of stainless steel, then they should outlast the wood by a long margin.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2022 at 12:13am
I get it,it seems the right thing to do , but we all take the speaker door off everytime we change the speaker and Ive never encountered inserts , t nuts or problems with those.
I have used standard bolts directly into (decent) ply boxes to attach casters with no issues at all. I did a test years ago with a crow bar to try to pull them out  and there's no way they are coming out without rotation.


Edited by Tinnitus Rex - 12 May 2022 at 12:27am
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2022 at 10:35am
Every speaker in our warehouse has inserts or t-nuts for the access panels. That was the case even in the early days, with a mishmash of DIY subs, Martin Philishaves and JBL bi-radial horns.

If you have access panels held on by wood screws, I feel sorry for you. It isn’t the case these days, but the first time I saw that on a Funktion One product with a list price of £5K+ I was genuinely shocked. It just gives the impression of not taking pride in the work.

It probably doesn’t help that I was refurbishing them at the time, due to the wood screws corroding and the heads snapping off.

I don't see any valid reasoning here other than laziness. The price difference in the fixings is pennies on a product that's going to retail for several hundred or thousands of pounds. The time difference is next to none of its planned as part of the build.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2022 at 10:52am
The only down-side to using T nuts is when the threaded shaft of the nut works loose and spins endlessly, very annoying if you have no access to the rear of the nut to swap it out. (As happened to me on a couple of occasions).
Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2022 at 11:34am
I’ve had that once too. Invented a few new swear words that day 🙃

If you avoid the cheapest Chinese steel fixings and don’t use a drill on turbo torque to ram the bolts in, it should very very rarely happen though. The same way you try to avoid turning the head of a wood screw into jelly!

Unless you mean the entire nut shredding the wood or falling out? That’s far less likely if you glue the buggers in, and put a couple of tiny screws to stop them rotating.

A threaded insert is a lot easier to replace on an existing baffle than a t-nut, in my experience. Neither are particularly fun, but I know which I’d prefer. I'm surprised you don't see more threaded inserts used on the baffle in professionally built cabs.

Edited by toastyghost - 12 May 2022 at 11:36am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2022 at 12:37pm
Obviously gold plated oxygen free T-nuts are better.
In design for every problem you solve you create a new one (Dyson vacuum cleaners?)
Above all ...Avoid modes of failure ,Less components, less to fail and utalise materials atributes .
 A list of my favourite speaker fitting problems in no particular  order:
The head of the fixing bolt is too big and clashes with the cast speaker chassis edge.
The head of the fixing tears up the fabric of the edge support .
The fixing needs to be overtightened to stop it working loose under use,we use lock washers and they do nothing..
The wadding of the box gets "involved" with the bolt threads and we cry.
That last bolt we try to thread into the T-nut pushes the T-nut out and we cry.
We are locked out of the box because the t-nuts are spinning.
The allen bolt heads are trashed due to over tightning due to stopping them working loose.
The angle that the t-nut spikes lock into the grain of the ply means they cant penetrate and bend flat .
The T-nut hole was drilled too big  and does not give a good friction fit.
The start thread of the T-nut is damaged and will not start.
The bolt was not greased when fitted and has rusted and jammed in the thread.
The speaker mounting holes are mysteriously not a standard position!
The gasket is so foamy it distorts the chassis when compressed.
The (eminance) cardboard front gasket sticks to the baffle .
The JBL mouting holes are too close to the baffle cutout.
Some one thought it was "a thing" to make a slight rebate in the baffle  around the driver cutout!!!
Some speaker chassis wont fit "that" cutout .
JBL speaker edge supports touch the baffle cutout and tear if back mounted.
MDF baffles ?!?
  Please add to list....

 Tis Blasphemy (and I dont often do it) but a Greased,pilot holed, countersunk torxhead screw would solve most of these problems  and your not commited to any hole spacing.



Edited by Tinnitus Rex - 12 May 2022 at 2:10pm
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2022 at 1:30pm
 Shout at me if you want, but ever since owning my old Nexo SI system ( which used screws rather than t nuts and machine screws) i have used M6 screws, either pan or countersunk head as shown. Even with the heaviest drivers and the roughest treatment no loose or rusted in bolts, no issues whatsoever. I do use T nuts for wheels etc but for drivers, horn flares etc these every time.



Edited by csg - 13 May 2022 at 1:36pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2022 at 10:34pm
Ive always used fully threaded inserts. Not a fan of t nuts if you cant get to the back in the event of a failure. 

I also dont see why, done properly and with the right fixing, screws straight into the ply wouldnt be perfectly sufficient. If it works, it works. 
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