Still tightening my cabinet bolts.....

ATC & other manufacturers design parameters, technical queries etc
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Still tightening my cabinet bolts.....

Postby studioman » Tue Jul 18, 2017 11:05 pm

Tightening my cabinet bolts again.....
I did them around February time on my SCM150ASLT cabs, and have played my system quite loud (well you would, wouldn't you!)
I checked them today and MOST bolts needed ¼ turn or ½ turn. That's the baffle bolts, the bass and mid bolts...
My tweeter bolts however I keep 'just tight enough'. Sweeter that way, it seems to me, although I have had different experiences with other speakers.
Anyone else have any thoughts on mid and tweeter tightness? Linn used to say 'tight as poss...', ATC has some torque settings on record, Naim also seem to say 'tight as you can' but I have also heard that tweeters and mids should be 'nipped up'
Any thoughts on the theory?
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 63...oh shit, it's 64 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Still tightening my cabinet bolts.....

Postby audio_guy » Wed Jul 19, 2017 2:14 am

Very intriguing!

I would've automatically said as tight as possible, just to assure that you don't get any unwanted rattles, but when you put a snare drum in a stand you don't tighten the stand around the hoop of the drum too much so as to avoid putting stress on anything that might alter the sound of the drum.

I wonder if there might be any similar implications here.

Would you say you hear a very noticeable difference with different tensions?

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Re: Still tightening my cabinet bolts.....

Postby MattSPL » Wed Jul 19, 2017 7:40 pm

I've always gone for nicely tight without overdoing it.
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Re: Still tightening my cabinet bolts.....

Postby Brad Lunde » Thu Jul 20, 2017 3:59 am

I would say I too have noticed that bolts can unscrew themselves with vibration, but I also know about ATC warning me about over tightening, and thereby ruining the cabinet. Be careful! This is not one of those times you tighten tighten tighten as tight as possible. The cabinet material can compress over time.

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Re: Still tightening my cabinet bolts.....

Postby studioman » Thu Jul 20, 2017 9:20 pm

As a woodworker in a previous career, I know that MDF compresses very easily if the bolt is within a short distance from the edge of the board. It's because it is a weaker material under compressive loads near the edge.

So I am sure that this fact will be the reason that overtightening near the edge is not desirable, but also, as far as I can tell, it doesn't matter how much a bolt is tightened up, if its near the edge, it will be creating a compressive force and it is likely to need retightening slightly again and again.

As regards the sonic benefits, there is NO DOUBT at all to my ears thatbass is clearer, more defined, and faster.

Mid also gets clearer and more focused, but it is not as major a difference as the bass bolts make.

And then there is the treble.
I'll tell you a secret. My two ATC HF drivers are of course baffle mounted, but there is a specially built inner container behind the baffle. So even with the tweeter removed, the cabinet remains sealed. These bolts are not securely tightened. There are 2 rubber O-rings, threaded on the 3 fixing bolts, one on each surface (front and back) of the tweeter. ie the bolt head does not touch the tweeter faceplate, as a rubber ring separates them. Likewise the rear of the faceplate is separated from the recess of the baffle by the second set of O-rings. This partial decoupling of the tweeter from the baffle may or not be a good idea, which is why I asking for your opinions.

Some other companies do similar things, and Naim's tweeters in some designs are not even mounted on the baffle. They are securely mounted on metal frames which poke through the cabinet and through a hole IN the front baffle, without actually touching it. The principle is to decouple the tweeter from damaging vibrations of the baffle.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 63...oh shit, it's 64 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Still tightening my cabinet bolts.....

Postby Lemen » Thu Jul 20, 2017 11:21 pm

studioman wrote:As a woodworker in a previous career, I know that MDF compresses very easily if the bolt is within a short distance from the edge of the board. It's because it is a weaker material under compressive loads near the edge.


With your specially designed sleeves for the baffle bolts, perhaps you're able to tighten the bolts a little more than their specified torque setting without too much fear?

Very interesting to hear about your experiments regarding driver and baffle bolt tightness and how it effects sound quality.
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Re: Still tightening my cabinet bolts.....

Postby studioman » Mon Jul 24, 2017 7:06 am

Lemen wrote:
studioman wrote:As a woodworker in a previous career, I know that MDF compresses very easily if the bolt is within a short distance from the edge of the board. It's because it is a weaker material under compressive loads near the edge.


With your specially designed sleeves for the baffle bolts, perhaps you're able to tighten the bolts a little more than their specified torque setting without too much fear?

Very interesting to hear about your experiments regarding driver and baffle bolt tightness and how it effects sound quality.



Hi Lemen.

You're correct about the sleeves being a help. That's why I designed them the way I did, although I don't torque them up MORE than ATC's reccomendation.

I did a material Science course once which taught some very simple rules...
Materials crush under load, and likewise when a holding device (such as a bolt) is subject to forces, it will respond in the OPPOSITE way by microscopically lengthening. (the softer the material, the more this will happen, and conversely, the more high tensile the bolt, the less this will happen)

Just about ANY product will have bolts looser than when manufactured, especially if it's been sitting around for a long time, OR has been subject to vibration.
Examples:
1. My new AEG dishwasher...which I installed yesterday.... Before I installed it, I went round it tightening moderately every visible self-tapper and bolt, with torx wrenches and a Phillips screwdriver tip. I would say around 80% needed a 'nip up'.
2. My 2011 Mercedes....every so often I double check the front suspension strut bolts under the bonnet, and all visible bolt heads on panels under the bonnet, on the door catches doors, boot hinges, etc. There's usually a few of the bolts holding the radiator grille, headlamp pods, fairings, etc, that have loosened slightly. Nipping them up with a torque wrench prevents vibration and noise.

In the same way, whenever I buy a used amp or cd player etc., I remove the lid, and after checking for cleanliness (carefully using a can of compressed air to remove dust), I go round it tightening up chassis, socket and circuit board bolts, cable tying or separating cables, sometimes applying self-adhesive but easily removable damping material to side and top panels, and nowadays applying a small piece of EMI filtering grid to the top of any ICs to help reduce stray fields, sometimes applying a strip of Poron (insulating and vibration reducing material) between the edge of a circuit board and the bottom chassis panel.....and a few more things. In all, this all makes any piece of electronic equipment less susceptible to inner vibration and to external influences.

VERY worthwhile, it all makes a BIG difference.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 63...oh shit, it's 64 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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