I’ve had my Ovator S-400s for about 14 years and never even removed the grilles but looking at other threads on here (eg “Ovator S400 - optimize performance?” ) I decided to check and if necessary torque the various spikes and bolts.
The floor spikes: these had come loose for sure so a while ago I carefully levelled, ensuring no rocking, and tightened the spikes.
Plinth fasteners - Naim tech support advised on torque setting for the plinth fasteners - both front and back. This meant lying the ‘speaker on its side and removing the crossover but was pretty straightforward - there was easily enough spare cable to get the crossovers out of the way. Some of the bolts were definitely a loose and they all were below spec. So far so good….
Bass units: again Naim advised on the torque settings: two drive units, 6 bolts each. Interesting some of these were definitely loose and I mean not even finger tight so I felt this was very worthwhile.
I had a listen and straight away noticed better bass performance - more weight and rhythm to bass lines so was well pleased with this. I spun a fair bit of vinyl last night with great results.
Now on to the BMR units: here I am a bit stuck. The guidelines Naim sent me were for the S-600 but the S-400 BMR mounting is quite different. I removed all the 6 visible bolts and lifted the unit out: the BMR drive unit remained attached to the ‘elastomeric’ mounting plate though I could see a further 6 nuts behind once I’d lifted the assembly away from the cabinet (photo). Out of ‘an abundance of caution’ and with no further guidance I did no more except replace the assembly and torqued the six outer bolts without touching those nuts. Maybe this is all there is to do? Anyone know if there’s more to it than this? Is the elastomeric ring (the bit I’m holding) supposed to detach from the BMR driver itself? Or do those nuts get torqued from the back? I SO don’t want to mess this up!!
Yes thanks for reminding me!! I’ve been very careful so far and all good. I don’t want to take any unnecessary risks! If I am not sure I will leave well alone having already done the floor spikes, plinth and bass drivers. They are sounding wonderful at the moment.
OK thanks Richard. I am in touch with them and I will check back again to see if they have anything specific on the S-400s BMR. But yes I will leave alone unless 100% sure there is a proper procedure I can follow. It may be I have done all I need to do. They certainly sound better than ever at the moment.
The elastomeric part is sandwiched between the silver ring & the front plate - it is an integral part of the BMR unit. The studs are pressed into the front plate & the nuts fitted/torqued from the rear. These are serrated flanged nuts, so shouldn’t have become loose (in theory).
I am going to be doing the same on my S600 soon, and maybe even replace a BMR.
Did you find that there was enough cable for you to freely move the BMR around? I’m wondering whether there will be enough space to easily solder the new one. What about the bass drivers? Did you take any one out?
Also, what is that hair-like material inside the chassis? Probably acoustic treatment?
I was going to report back … the re-torque has been a sensation. The Ovator S-400s now produce much better deeper tuneful bass. Everyone should check this. I did the bass drivers (two per cabinet) and the plinth bolts that connect the plinth to the cabinets. Mine had not been touched since I bought them new around 2011 and several of the bolts were either loose or not tight. So I am not surprised the speakers were not working as Naim intended! And after NeilS’s reply above I basically left the BMRs alone apart from tightening the bolts holding the surround to the cabinet.
I had advice via email from Naim Support. In fact the procedure they sent me for re-torquing was for S-600s so I’d suggest you contact them. In any case the S-400s BMRs seem to be mounted quite differently to those in the ‘600s’ : I have no leaf springs for example.
For the bass drivers - I didn’t remove them, just slightly loosened and re-torqued the bolts one by one. This was really simple and quick. Doing the plinth bolts (connecting the plinth to the cabinet via the leave spring) meant lying the speakers down and pulling the crossovers away to make room for the torque wrench - they are held by 4 bolts under the speakers and there was plenty of cable to ease them away far enough.
Good luck and let us know how you get on. I am seriously gobsmacked by the improvement and happy I can hopefully enjoy these lovely speakers for many years to come.
Ah, I’m glad you’re enjoying such an improvement. Never heard the S400s, but I assume they must be great speakers too. With their “lower” price nowadays, have you considered getting a second pair for spares?
My S600s have not been touched too, probably in 15 years. I know for a fact that there are loose bolts at the plinth, since one of the cabinets can be slightly moved while the plinth sits still. So I definitely expect improvements.
I’m very hesitant to lay them down because of their massive weight though. I don’t want to put too much stress on two spikes (or any joint) while turning them over. Need to find a foolproof way to do that. And I still didn’t get a torque wrench. What did you use?
Best to request the data / procedure by contacting Naim Support and get a decent torque wrench (and of course the Hex heads of the correct sizes) that cover the range. The torques are a bit lower than I’m used to from dealing with bicycles! And Naim will also advise on the transit bolts too - I gather that with the S-600 you need to fit these if you are going to lay the speaker down to get to the plinth bolts. (S-400s don’t have transit bolts)
I felt the biggest gain for me was in doing the bass units and you can do these very easily without even moving the speakers so that might be where I’d start tbh.
A torque wrench - or in this case, a torque driver - is a useful tool for taking the guesswork out of screw tightening. They do, though, only provide an approximation of the force applied by the screw you tighten. So it’s a complete waste of money buying a fancy expensive one.
Mine is a Sealey digital one which cost about £45 a couple of years ago, chosen mainly because it covers a useful range form almost zero up to 5Nm.
I used a Park Tools FW-5.2 I had in my bike toolkit. I just looked it up and I’d forgotten how expensive they are.. fool and his money ! Anyway it’s a nice little tool. I’ve used it a fair bit and had long since forgotten the price I paid for it.
The most accurate torque driver won’t give very precise results. Most are sold with a +/-6% accuracy rating.
The purpose of a screw is to apply a clamping force to join materials together. The rotational force applied by the driver is, at best, an approximation of that clamping force, and is subject to variables such as variation in materials, variation in surface friction, temperature, and user error.
If you really want to apply a clamping force accurately it would be possible in some situations by using, for example, a calibrated hydraulic jack to tension a bolt, but in many cases (including screwing a speaker cone to an MDF cabinet, of course) this is impractical. Applying a torque setting is of course plenty good enough in this case, but it is still an approximation.
Some torque wrenches can be recalibrated to ensure a consistent accurate torque is applied, but that doesn’t address the issue of ensuring that the screw is applying the correct clamping force that joins the two parts together because it cannot eliminate the other variables.
My point was really just that a cheap torque driver should be good enough for such a non-critical use, and in any case, a relatively expensive torque driver is unlikely to give better results
