Identification of stuffing type

[bitbandit]

I am restoring a pair of ar-2ax's from 1973 and the stuffing is as shown in the photo.

Can anyone identify what it is? It looks like the stuff they used to make carpet underlay out of, and doesn't feel at all like fibreglass or mineral wool- it is quite soft.

Is it original, or should it be replaced with fibreglass? It seems in good condition.

Thanks

[Guest rbrumett]

I am restoring a pair of ar-2ax's from 1973 and the stuffing is as shown in the photo.

Can anyone identify what it is? It looks like the stuff they used to make carpet underlay out of, and doesn't feel at all like fibreglass or mineral wool- it is quite soft.

Is it original, or should it be replaced with fibreglass? It seems in good condition.

Thanks

The surrounds look original and the stuffing looks like polyester. I believe that AR did use that in the latter days of AR2ax production. I am sure others will pipe in.

Thanks,

Rick Brumett

[Guest Bradders]

Hi,

I inherited a pair of AR-7's from my dad. He bought them new in 1975 and has never opened them.

I opened them last night in the process of overhauling them. They are filled with what looks like exactly the same filling as yours.

I can only imagine then that it is the fibre glass people are talking about since it is original.

Hope this helps.

Bradders

[Carlspeak]

Your 2ax sturffing looks to me like a blend of wool and cotton like that used to make thick compressed felt pads for industrial use. You can keep it or replace with FG. Suggest you use about 20 oz of Owens Corning pink fiberglass. You might notice a slight improvement as FG seems to be the best stuffing for these old AR's.

Do us a favor and weigh, if you can, the stuffing you have now if you do decide to replace it and post here what you got for the weight.

Thanks,

[Robert_S]

I am restoring a pair of ar-2ax's from 1973 and the stuffing is as shown in the photo.

Can anyone identify what it is? It looks like the stuff they used to make carpet underlay out of, and doesn't feel at all like fibreglass or mineral wool- it is quite soft.

Is it original, or should it be replaced with fibreglass? It seems in good condition.

Thanks

Hello,

From looking at your picture, in particular the design of the narrow front cabinet moulding, I'd guess that your AR-2ax were assembled in Europe, where the introduction of polyester fiber wadding seems to have taken place at an earlier date, than has been observed with USA assembled models. Amongst my AR speakers, I've some AR-3a Improved, from 1974, with a similar looking wadding (they produce superbly deep bass), and some AR-7: my USA flavour have fiberglass and my European have polyester, they both sound very good.

The picture below shows detail of the multi-coloured polyester from my AR-3a Improved (note thin strips of metal foil!):

If you were pleased with the quality of sound produced by your speakers, prior to restoration, I'd leave them as is.

Robert_S

[bitbandit]

Many thanks for all the speedy replies!

Based on your answers I think I will keep the original stuffing unless it all falls apart when I dig my way in to clean the pots.

If it all has to come out I will indeed weigh it and post the result here.

I forgot to mention that for those interested they are European manufactured.

Thanks again for your help.

Dave

[genek]

Based on your answers I think I will keep the original stuffing unless it all falls apart when I dig my way in to clean the pots.

If it all has to come out I will indeed weigh it and post the result here.

I forgot to mention that for those interested they are European manufactured.

If you do that, see if you can read any markings off the capacitors, coils, etc., in the crossover. It would be interesting to see if AR made any crossover changes to go along with the stuffing used.

[kimberley]

Hello from London, England.

The AR-2axs which I overhauled recently (thanks for all the advice on this board!) were U.K. assembled & had the same type of stuffing as illustrated. (In passing, Bang & Olufsen used very similar, probably identical, damping in their small 'speakers, C40s & C75s at much the same period).

I found that the potentiometers in my pair had little corrosion & that the stuffing was easy to handle, so I re-used it. I regret that I did not weigh it.

I disconnected the old capacitor block & substituted medium-priced polypropylene capacitors of the same values, having found this worthwhile when renovating IMFs, greatly improving their response, probably back to factory settings. (The IMF crossover is much more complex, however.)

When I thought I had finished, I took out the midrange units (curiosity got the better of me) & found that they had a resistor pack & a capacitor soldered across the terminals, which delayed my pleasure in listening as I then had to obtain more capacitors!

These 'loaded' midranges have been mentioned in this forum before & appear to be factory original & perfectly functional: I mention them as they are worth checking if one is replacing - or even measuring - the other capacitors.

I am listening to the 2axs as I type this & they remain a delight. So much so that I have recently bought a pair of AR-5s as a winter project!

Adam Kimberley.

[johnieo]

I am restoring a pair of ar-2ax's from 1973 and the stuffing is as shown in the photo.

Can anyone identify what it is? It looks like the stuff they used to make carpet underlay out of, and doesn't feel at all like fibreglass or mineral wool- it is quite soft.

Is it original, or should it be replaced with fibreglass? It seems in good condition.

Thanks

The fiber to which you refer was indeed used first in Europe. The sample I analyzed in the SEM consisted of a mixture of 17-um-diameter (red) and 34-um-diameter (gray) trilobal polyester fibers. Were these speakers mine, I would not change the stuffing, as likely it is original AR. However, the weights of these polyester stuffings were not the same as that of the fiberglass they replaced, so a measurement and reporting of their weights would be a valuable addition to the already large AR database.

Cheers,

John

[bitbandit]

The fiber to which you refer was indeed used first in Europe. The sample I analyzed in the SEM consisted of a mixture of 17-um-diameter (red) and 34-um-diameter (gray) trilobal polyester fibers. Were these speakers mine, I would not change the stuffing, as likely it is original AR. However, the weights of these polyester stuffings were not the same as that of the fiberglass they replaced, so a measurement and reporting of their weights would be a valuable addition to the already large AR database.

Cheers,

John

In response to requests for info, each of the speakers contained 510g or 18oz in old money, of stuffing.

These are by no means the first AR's I have restored but this pair that recently came into my possession are the first AR-2ax's I have done.

I replaced the woofer foams and being a believer in not changing things for change sake, I tried them out. Yeuch. Mid was dreadful and top worse. A bit of judicious measuring revealed the reason was that one 4uF cap was now 6uF and the 6uF was 9uF. I suppose 35 years of drying out has taken it's toll. The other speaker was in a similar state but worse, at 8uF instead of 4uF and 12uF instead of 6uF. I replaced all the caps with NPE types. I could have spent a lot of money on some capacitors that had been hand rolled with gold foil dielectric under a blue moon by virgins, but what are the chances of finding gold foil in the midlands? ;-) I doubt that there would be an audible difference. Anyway, fired them up again and they sound lovely. Very accurate.

One mid range is a bit bright but can be brought down by reducing the pot to about a 3rd back from the top. Both mid ranges have the 3 ohm ballast on the back.

The tweeters are not so hot. One was very croaky and a bit scratchy sounding but with use it seems to have freed up. I think it's a mechanical problem with the suspension. Which leads me to the other tweeter.. It is a bit of a sad case, although the voice coil and wires are intact and measure the right resistance (about 5.5) there is hardly any sound at all. It must be a mechanical problem, and although I have dismantled tweeters before, I haven't opened one of these chaps up. I suspect the suspension has collapsed and the coil is fouling something so badly it can't move. Are there any pictures of one being opened? I saw a thread about dissecting a tweeter but it seems to only be dissecting it in terms of specs, not physically. I am aware of the tiny wires. I think it's a case of nothing to lose by trying really. What looks like the membrane feels quite sticky so I guess that if it was doing the job of suspension after the 3 blobs failed, and they are very fragile, then it too has given up the ghost.

As an aside, I read the discussions about tweeter replacements and I have a couple of Vifa D26TF-05's hanging about so I tried one out. They are 6ohm and I tweaked the crossover freq up a bit to around 5.5k. It sounds ok at best (and better for being crossed over a bit higher). It's a 1" soft dome and with the original still in the other speaker and now performing reasonably, it is very obviously not a patch on the original. The level is ok but it doesn't sound as clear. If you are listening to speech, all the sibilance comes from the old tweeter. There is nothing actually *wrong* with the vifa, but it isn't as good by a long way. Just thought I'd mention it in case it helps anyone else.

Of course I still have the cabinets and grills to deal with at some point, but that's another day's work for when I have the drivers all sorted.

Hope this info may help someone else.