Torque settings and driver for ATC drivers and baffle.

ATC & other manufacturers design parameters, technical queries etc
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Torque settings and driver for ATC drivers and baffle.

Postby studioman » Sat Oct 29, 2016 2:19 pm

Many of you will know that bolts holding drivers and baffles tend to 'relax' over time. This affects the performance of the loudspeaker, although over time it will tend to be less obvious.

It is very easy to tighten these TOO tight and there are numerous reports on various forums of the resultant sound not being 'quite right'. Of course over-tightening can also cause damage.

I therefore bought myself a generic ¼" torque wrench to tighten up bolts properly on my ATC speakers, with the added benefit that I could use it under the bonnet of my car.
I was very disappointed when it arrived and I discovered that the range of my torque wrench STARTED at 5Nm. That's WAY too high a setting.
I hadn't even considered that it wouldn't have a low enough range for ATC speakers. So....it's just for my car, I guess.

So what's available for torquing my ATC bolts?

ATC recommend for my SCM150 cabs (and I understand this applies to all ATC's bigger speakers from the SCM50 upwards) the following:
Tweeter bolts: 1Nm or 0.74lb/ft
Baffle bolts: 1.3Nm or 0.96lb/ft
Bass driver: 1.5Nm or 1.1lb/ft
Mid driver: 1.5Nm or 1.1lb/ft

Well, these two solutions offer some help....

FIRST ALTERNATIVE: Kamasa 56094
In the end, after the false start, and other than spending between £100 and £200 on an expensive low torque RS or Farnell sourced torque wrench, I found a hand held TORQUE SCREWDRIVER SET 56094 from Kamasa which goes from 1Nm to 8Nm. (widely available on a certain auction website, of course)
This would have a multitude of potential uses for me, for around £27, so I went for it.
If you feel like getting this aspect of your ATC speakers right, this is a good solution.
It works on the principle of a compressed spring ratchett, very much like your typical automotive torque wrench.
The torque adjustment is done using a tommy bar in the kit. The tommy bar fits into the end of the driver, and 4 rotations of the tommy bar changes the setting from 1Nm to 2Nm so it is pretty easy to approximate ATC's settings of 1Nm, 1.3Nm and 1.5Nm. I found it to tighten the bolts VERY consistently and effectively, except for the tweeter 1.1Nm torque. It wouldn't quite get down to that level easily, and it felt like I was going to strip some threads.....
There are a number of tips in the Kamasa kit....some Hex, some Star Torx....but you MAY have to buy the tip you need elsewhere... I had to buy a T30 Security tip for my bolts which are all Stainless M6 security bolts with a 'pip' in the centre....like on the SCM150ASLT Anniversary models. You need to check your bolts to get the correct tip, but they're just common 6mm hex tips which are readily available....
Oh, and it's built to last a lifetime.

SECOND ALTERNATIVE: Sealey STS103. Didn't buy it, but I found this one after I had gone for the the Kamasa, and I think it might be a better option if it's accurate...and it does claim +/-1% accuracy....
It's not quite as complete, as it doesn't seem to be a kit, just the handle, but this time its a digital torque screwdriver with a readout and + / - buttons on the end of the handle. This one goes from 0.01Nm to 5 Nm. Yes, you read that correctly, NOT 0.1Nm or 1Nm, but 0.01Nm.
It seems to work in a totally different way to the Kamasa....you dial in the required torque, then start using it. When you reach the correct torque, a light comes on, a buzzer sounds, and the handle vibrates. I presume, therefore, with all these micro-electronics, that it uses an internal strain gauge or something similar....but I'm not sure. Either way, it's up to you to stop turning as soon as it tells you to.
This COULD perhaps be useful even down to PCB bolts, tonearm bolts etc,....maybe even cartridge bolts too, I wonder at its very lowest settings? It's just the handle as far as I know, so you'll have to buy the tips separately, but the low range is fantastic. A little bit more expensive than the Kamasa at around £36, but possibly MUCH more useful.
It'll last as long as the electronics last, as long as you keep feeding it batteries.

The Kamasa and the Sealey are very different, but both look like very useful pieces of kit, maybe to go on your Christmas list! (No, I know, you can't wait that long either....!)

Added Note: It's YOUR choice, so go with your intuition, but I have sent my Kamasa back, having tried a Sealey jobbie this morning. The Sealey is a far better proposition. It also comes with a calibration table which has been done at the factory and proves its accuracy. That is worth it's weight in gold. The Kamasa is built like a battleship but it doesn't have the range suitable for what we need. If you're a member of the Audiophile Modders & Fiddlers Society too, I would recommend the Sealey. It will do everything you want to do in audio and more. Just don't forget to buy a nice set of tips. We all like a nice set of tips.

The first 2 pics are the Kamasa kit. The last pic is the Sealey.

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Last edited by studioman on Tue Nov 01, 2016 8:23 pm, edited 5 times in total.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 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: Torque settings and driver for ATC drivers and baffle.

Postby darrenyeats » Sat Oct 29, 2016 4:00 pm

Thanks for the information.

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Re: Torque settings and driver for ATC drivers and baffle.

Postby studioman » Sat Oct 29, 2016 5:23 pm

It's a pleasure!
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 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: Torque settings and driver for ATC drivers and baffle.

Postby linger63 » Sun Oct 30, 2016 9:47 am

Great post Studioman!!!!

Thanks ;)

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Re: Torque settings and driver for ATC drivers and baffle.

Postby Lemen » Sun Oct 30, 2016 12:05 pm

studioman wrote:The Kamasa and the Sealey are very different, but both look like very useful pieces of kit, maybe to go on your Christmas list! (No, I know, you can't wait that long either....!)


No, you're right, I couldn't wait for Saint Nick, so I've just ordered the Sealey torque handle!

I'd also read about tightness of the driver bolts being critical to the sound of the speaker, so I've had it in mind to ask ATC for the torque settings etc, but, no need to do that now thanks to your terrific post with all the info I need.

I've obtained some titanium taper-head allen bolts for the SB-75-234-SL drive-unit fixings, which should look quite nice. I didn't particularly need titanium but I didn't want to use aluminium bolts, which seemed to be the only other alternative for this shape of head.

Well, I think I should be all kitted out now ready to do the work. Thanks again studioman :-)
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Re: Torque settings and driver for ATC drivers and baffle.

Postby studioman » Sun Oct 30, 2016 7:56 pm

I did wonder about using some titanium bolts that I'd found on 'the Bay' for my SCM150 build, but when I worked out the cost I changed my mind. I love titanium as a material...I use it a lot. it's special, but I knew that in this case it would not have any benefit that I could think of over stainless steel.

I wouldn't ever use aluminium bolts because:
a) they are very much weaker than mild, tempered, case hardened or plated steel, high tensile steel, stainless steel or titanium,
and
b) they can react (corrode) and find themselves locked in position in the steel inserts.

In either of the above cases, you have a BIG problem.

I found high tensile black steel allen (hex) socket bolts with a countersunk head, but fancied the 'special' look of the stainless steel Torx security bolts.
I eventually chose:
M6 x 40 countersunk stainless steel Torx Security bolts for the SM75-150S midrange Superdome,
M6 x 60 countersunk stainless steel Torx Security bolts for the baffle bolts, initially to go with countersunk steel washers as per the ones ATC themselves use, BUT see note* below....
M6 x 40 Cheese Head stainless steel Torx Security bolts for the ATC SB75-375SL bass driver,
M3.5 x 70 High Tensile black cheese head hex bolts for the ATC SH34-76 tweeters.

*I replaced the solid steel countersunk washers with some custom ones which I designed which were longer, sleeved units made of stainless steel. The reason? Because the original washers seem to have a propensity to damage the baffle when slightly overtightened. This is because the pressure on the edge of the baffle from inside the baffle bolt hole can cause the edge of the baffle to collapse inwards....see the pic at the end of this post....

ATC's countersunk washers:

Image

My custom machined versions:

Image

Image

And this is the kind of damage that the simple countersunk washers can cause to ATC speakers if the bolts are overtightened: (seen on M. Hennessy's website http://www.markhennessy.co.uk/atc )

Image
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 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: Torque settings and driver for ATC drivers and baffle.

Postby studioman » Tue Nov 01, 2016 8:25 pm

See my added note above (in blue) to explain why I sent the Kamasa torque screwdriver back after I had tried the Sealey version.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 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: Torque settings and driver for ATC drivers and baffle.

Postby Lemen » Tue Nov 01, 2016 11:26 pm

As you say, the calibration table included with the Sealey was a big incentive for me. I'm sure it will have superior precision over the Kamasa, which did look a bit crude for the intended use. The Sealey should be a pleasure to use, whereas I don't think the Kamasa would be?

Ahh yes, we do indeed like a nice set of tips . . . as long as they're PG?

Regarding your own designed baffle bolt sleeves; I'd imagine that ATC would be very interested in your design and could perhaps implement such a modification in future production? Of course, cost will always come into play, but I wouldn't have thought that the sleeve would be too much more expensive to produce in large numbers over the washer.
Maybe you'd better get a patent in pronto!
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Re: Torque settings and driver for ATC drivers and baffle.

Postby studioman » Wed Nov 02, 2016 2:59 pm

Lemen wrote:As you say, the calibration table included with the Sealey was a big incentive for me. I'm sure it will have superior precision over the Kamasa, which did look a bit crude for the intended use. The Sealey should be a pleasure to use, whereas I don't think the Kamasa would be?

Ahh yes, we do indeed like a nice set of tips . . . as long as they're PG?

Regarding your own designed baffle bolt sleeves; I'd imagine that ATC would be very interested in your design and could perhaps implement such a modification in future production? Of course, cost will always come into play, but I wouldn't have thought that the sleeve would be too much more expensive to produce in large numbers over the washer.
Maybe you'd better get a patent in pronto!



I am VERY pleased with the Sealey. It's a bit fiddly for my older eyes trying to see a tiny 'seventies style digital watch' type screen, but it works well and I have 100% confidence in the torque that it produces.

I had wondered about the baffle bolt sleeves......
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now, ...How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

Posts: 33
Joined: Tue Jun 07, 2016 2:11 pm
Location: England

Re: Torque settings and driver for ATC drivers and baffle.

Postby Lemen » Wed Nov 02, 2016 11:16 pm

studioman wrote:I am VERY pleased with the Sealey. It's a bit fiddly for my older eyes trying to see a tiny 'seventies style digital watch' type screen, but it works well and I have 100% confidence in the torque that it produces.

I had wondered about the baffle bolt sleeves......


I received my Sealey today and am also very pleased with it. Testing on the baffle bolts I found that most of them could be tightened aprox ¼ turn.
As you say in your first post, this is proof (if it were needed) that bolts tend to relax over time.
The torque screwdriver works very well indeed. The only (very minor) thing is the setting of the peak value; it not being possible to decrease the value, you can only increase it. So if you do unintentionally go over the desired value, you have to reset to zero and then increase to the desired value again. Not really a problem as once you know, you know don't you. Likewise, I also find the display a bit tiny for my 52 year old eyes, but again, it's a simple display and once you know what the various indicators are, you don't really need to be able to read them.
Last edited by Lemen on Sat Nov 05, 2016 7:35 pm, edited 1 time in total.
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Re: Torque settings and driver for ATC drivers and baffle.

Postby studioman » Thu Nov 03, 2016 9:00 am

I totally agree with you about all aspects of the Sealey torque screwdriver. And try 62yr old eyes! It's even harder!

Glad I was able to suggest something that has helped you in the Sealey tool.!
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now, ...How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Joined: Tue Jun 07, 2016 2:11 pm
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Re: Torque settings and driver for ATC drivers and baffle.

Postby Lemen » Sat Nov 05, 2016 7:34 pm

studioman wrote:And try 62yr old eyes! It's even harder!

Haha - well it's not going to get any easier for us eh.

studioman wrote:Glad I was able to suggest something that has helped you in the Sealey tool.!

A big THANK YOU to you for finding this tool and for all the excellent info. It will be of great assistance to me.
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