2 pairs of AR MST (3 tweeter version) for renovation - need new foams and clean up.

[Stevie F]

Hi All,

 

I just finished restoring a pair of Naim SBL Speakers, big heavy monsters but lovely sounding.  My brother in law has now given me 2 pairs of AR MSTs (3 tweeter versions) to restore.  I can see that these are pretty rare speakers.

Firstly the cabinets are in reasonable condition, but could do with some work to remove scratches, only one needs a lot of work but if I do one I will do them all so they match up. First question is whether people think its worth doing this? I was planning  to do a very high grit sand and clear re-varnish (matt) so as not to lose the original colour.  The speakers covers are all in good condition with original labels, just need a clean up.  I understand them are made of woven wool so maybe just a light detergent hand clean?

I have not tried them hooked up to a amp yet, but on inspection over the weekend I can see that all of them need new foams.  I read la lot of posts and believe that they are 8" Woofers, I am based in the UK but can anyone recommend the best kits to get? I want to avoid any cheap replacements.  Watched many video's about how to replace them, as an engineer it feels like it should be a job I can handle myself, but has anyone had a big problem doing this themselves?

[JKent]

Welcome Frankie

Re-foaming is very easy. I use foams from SpeakerWorks here in the US but maybe a member on your side of the pond can suggest a supplier in the UK. Be sure to use white glue, not the solvent-based stuff.

I have not owned MSTs but it looks like the grilles are linen--not wool. Be very careful because it will shrink if you use water.

How bad are the worst parts of the cabinets? That one close-up doesn't look bad at all. I think I'd try Howard Restor-a-Finish and if it looks good then follow up with some wax. If you do decide to sand and varnish my own preference is for gloss (not matte) and, when totally dry, buffed by hand with a white Scotch Brite to to give it a soft sheen. Just personal preference.

Kent

[Stevie F]

Thanks for you input Kent.  The one I had in the photo was not the worst cabinet, one had a lot of scratches on the top which is a shame. I might try and pair up the best two and the worst two and decide how much restoration is required on each set.  There is not a big surface area to them so it won't be such a big job as the Naim's I did, (see picture).  I was going to use matt varnish as that appears to be what they are but maybe just dirty! Will give one a buff with some finishing wax and see how the good ones come up.

I'll check out SpeakerWorks to see what their pricing is like, from other posts it sounds like these are very good replacements.  But hopefully there is a local supplier I can use to avoid shipping and import tax.

Will post up progress.

Next I really need to give them a go on my system to make sure they work ok, ignoring the foam issue (so won't drive them hard).

Steve.

 

[genek]

The original finish on classic era ARs was a penetrating oil with a drying additive. If your speakers were made in the UK or elsewhere in Europe, then they might have been finished with conversion varnish or catalyzed lacquer which were more common finishes there. 

My experience has been that matte finish topcoats have a tendency to cloud grain, especially if multiple coats are applied. If you decide to varnish, use a gloss finish for the first coat/s and either apply only the last coat as matte, or just abrade the last glossy coat for a satin finish.

The grill cloth is flax linen, not wool. The currently favored replacement is called "lambswool," but it's not wool either. The manufacturer says "linen," which in the US can mean flax, cotton or some blend of the two. If you can't find it there, try looking for flax linen scrim.

[KlausDK]

Hi
I don't know of any source for surrounds in UK, I use audiofriends in Holland, excellent service and products:

https://www.audiofriends.eu/

Brgds Klaus

[Stevie F]

Thanks for the valuable info Genek.  As a test I prepared the base of one speaker using 120 to 320 GRIT sand paper, removed nearly all scratches.  Then used a Clear Matt Oil-Wax (Microporous) from Osmo , I have used on solid oak worktops before.  Its great at protecting\sealing and keeps the natural wood finish.  See the picture, it looks like a refreshed original now. Will give it a few coats and then see if its needs a light buff up.

Hi Klaus! Thanks for the weblink, I have already contacted them to confirm the correct part, hoping that the delivery is OK, they seemed worried about BREXIT delaying post but lets hope that's all settled down now.  Did you ever use the glue that they supply, or is there a better alternative? I saw White Glue mentioned on other posts.

[KlausDK]

White glue can come in many "colours", the important thing is, that it retains a bit of flexibility, after it dries up, white glue for wood, for instance, hardens when it dries up, and is not suitable. I use "bookbinderglue", it works fine for me, I have never bought glue from Fred at Audiofriends.

I used to buy from Speakerworks, but it got too expensive with TAX, VAT and handlingfee, so I switched to Fred.

BRgds Klaus

[Stevie F]

Quick update, I managed to hook them up to my Arcam system, good some lovely Spanish guitar playing.  All three see to be OK.  The good news is that I inspected all the foams, they are so perished I think the removal will be very easy.  Will go ahead and try to purchased some replacement foams.

Quick question, how do you ensure the foams are sitting square on the paper cones? By eye or some clever process?

[Stevie F]

Some good news and bad news.  Good news first, renovated the first set of cabinets and very pleased with the outcome.  They used nice thick veneer so was possible to get most of the scratches out, and this was the worst pair.  Used a clear oil\wax treatment so they retain the original colour.  Will do 4 coats and then maybe a good wax finish.  Was also able to remove the old foam, even came off nice from the paper cone. And final good news, managed to source a supplier for replacement foams, Good HiFi in Netherlands so got 4 on order.

The bad news, I decided to do a quick impedance check on all the tweeters, on inspection one of them looked like the fine wire from the connector to the winding was broken, and confirmed, open circuit.  Its one of the middle tweeters. After taking them out it seems they use two different part numbers 200014-1 and 200014-3, one measured 9 ohms and the other 4 ohms, (side tweeter). Checked 2 of the other 4 speakers and all OK, so will finish checking the last one tonight.  So my question is how easy is it to repair the tweeter, or do I need to try and find a replacement, (which I guess is going to be real hard).

[Stevie F]

On 1/26/2021 at 7:39 PM, KlausDK said:

White glue can come in many "colours", the important thing is, that it retains a bit of flexibility, after it dries up, white glue for wood, for instance, hardens when it dries up, and is not suitable. I use "bookbinderglue", it works fine for me, I have never bought glue from Fred at Audiofriends.

I used to buy from Speakerworks, but it got too expensive with TAX, VAT and handlingfee, so I switched to Fred.

BRgds Klaus

Hi Klaus, after a long delay I finally managed to re-foam the first set! Got the foams from Good HiFi in Netherlands, great service, came really quickly, I also bought some Arleenes Tacky Glue and was easy to work with. Really pleased with the results.

The first one went well, but the 2nd one must have moved a tiny bit before it hardened.  Was rubbing so had to remove the glue and do it again, this time I used pegs to help centre it.  No both sound superb.

Thanks for all your help, I now have my eye on a set of AR-19Bs on ebay, that only need re-foaming.  Unfortunately this set of MSTs will be sold even though I have become attached to them.