SL2 bolt tightness

I have seen that the main ‘Allen key’ driver bolts need to be tightened to 3.6
Nm, i.e. Newton metres.

So AFAIK the bolts on SL2s that hold the rectangular tweeter surrounding plate and the 4 larger bolts that hold the bass drivers need to be tightened to 3.6Nm?

And the 4 tiny tweeter bolts (within the tweeter circle) need to be tightened to 0.8Nm?

Would someone please confirm whether this is correct?

And what size of torque wrench do I need to buy to hold what size of hex bits?

I have seen that the tweeter bolts hex bit needs to be 3/32ths of an inch.

The 3 closest-sized bits to fit the 3 sizes of bolts on the front of the drivers that I have to hand are shown below?

But the smallest one isn’t even a proper hexagon.

Are these ok or do I need other bits?

And what size wrench will these fit into?

1 Like

I’ve left my SL2s as I have no temptation to do anything as they sound great. Problem once you start it can almost end up like the episode from Father Ted “think fast” car raffle that ends in disaster

1 Like

You want something really high precision like this from RS Components - not cheap.
Pic from the web:

1 Like

The past thread “ Crumbs” should give some responses Jim.

You need a torque driver of the type Stephen posted, not a wrench.

Leave the tweeter bolts alone. The four screws holding the tweeter plate don’t really matter - they are more decorative than anything else.

It’s the four bolts on the bass units, and the three bolts in each of the interface plates (top of the bottom box, bottom of the top box) that should be tightened to 3.6Nm.


I have one that looks very similar, it’s a a Gedore 1-6 Nm, part number 547-379

Richard informed me the surrounding tweeter plate is torqued to 1.2 Nm and the “New” tweeter” bolts to .8 Nm. So what ever you do don’t touch the tweeters unless you are replacing. If they sound good they are good don’t let your OCD take control. If you do over torque them you may end up warping the tweeter diaphragm plus cracking the plastic mounting plate.

I was informed by a reputable naim dealer that the tweeter bolts can be finger tight plus a bit, just do it evenly, as far as I can tell they are just held in by the Hylomar Blue and lightly tighten bolts.

Finding a tool that can torque to .8Nm accurately maybe rather pricey.

I now have a good quality torque driver - top of its torque range happens to be 3.6Nm.

@Richard.Dane and others - Any thoughts on how to approach checking the tightness welcomed!

e.g. - should one loosen the bass driver bolts half a turn first with a standard screwdriver, and then re-tighten them with the torque driver up to 3.6Nm?

I realise that the bolts are likely to be looser as they will tend to loosen over time from vibrations.

But the previous owner might have over-tightened them, so one first has to establish whether they need tightening or loosening.

If you’re worried that they may have been overtightened then for sure, do slacken off slightly before you go ahead and torque them up.

Don’t forget to check the interface plate bolts. I would not slacken these off first though…

1 Like

When i did my Credo drivers i done each bolt in a opposite diagonal sequence. Worked a treat. Also i never touched the tweeters, i doubted they needed any attention.

1 Like

See photos below.
The data on this calibration sheet tells me that when the tester did 5 attempts at screwing something at 3.6Nm the mean torque of those 5 attempts measured at 3.653Nm.

That equates to 1.45% over the aimed for 3.6Nm.

Does that look like a correct interpretation?

If correct, that is well within the reasonable range.

So I’ll first test the driver to see how it clicks or stops at different torques.

Then set it to 3.6Nm and tighten the bolt to that setting, as discussed above.

Yep that seems reasonable enough, should be fine Jim. Don’t forget the set the driver back to it’s lowest setting once the work has been carried out, this will help preserve it’s calibration.


Bass drivers tightened.


They needed less than a quarter turn each.

Any (imagined) improvement is SQ is almost certainly due to the joy of knowing they are sorted.

1 Like

In case anyone is interested the above Laser Tools torque driver can currently be bought online new for a little over half the RRP.

Can the interface plates move below the loudspeakers lower wooden construction (the wooden frame which surrounds it) by time? Don t know, if I have expressed it precisely enough though?

Seems the top wooden part of the SL2 touches the wood of the lower speaker, so there is no gapp between those anymore. The spacers are applied.

Has anyone the same problem?

The top cabinet of SL2s is designed to sit on 3 tiny spacers.

The spacers have a right and wrong way up.

You need to replace your spacers regularly to be sure they are not flattened/squashed.

When the top cab sits on these spacers there is a precise gap between the 2 boxes that allows frequencies of soundwaves to travel as intended.

See, e.g., various mentions of spacers in this thread:

As I understand it, there are no more spacers, so if they are squashed that’s it. I rather doubt anyone would hear the difference between new and old ones though.

You can buy new spacers from Tom Tom. I did recently.

The pins are also available.


Seven days this thread has been running. I’m surprised nobody’s pointed out that the use of the word bolt is actually incorrect, leading to the possibility of an actual bolt (very fast runner) being tightened to 3.6Nm causing life changing injuries. :innocent:

That sounds like a problem. The wooden cabinets should not touch. Have the interface bolts been over tightened?

Not that i know Richard. I only used a wrench with 3,6 Nm.
I use now 2 spacers on top of each others. The Sl2 sounds as great as always.

Could this be solved in another way though?