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Torque settings and driver for ATC drivers and baffle.

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  • Torque settings and driver for ATC drivers and baffle.

    I found some of the baffle bolts on my SCM50ASL classics to be slightly loose after a few years of operation and I just nipped them up, very lightly to avoid damage from over-tightening. See

    However, one of the threads I kept from the old ATC Forums was on specific torque settings that would not cause damage. I hope it may be useful to reproduce it here although I also hope this does not tread on anyone's toes. Apologies if so.

    Below is the first part of the thread with specific user names redacted (I am not sure if the original poster re-joined the new Forums; or under what name if so; or if he/she wanted their name acknowledged anyway. But I do have the original thread).



    Torque settings and driver for ATC drivers and baffle.

    ORIGINAL POSTER 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.'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 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 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
    <… three missing images …>

    <… thanks and some discussion snipped …>
    Last edited by jophill; 02-06-2022, 10:57 AM. Reason: URL added

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