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Refoaming AR16 speakers - help needed


Jeff_C

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Hi all

Although I have been viewing this forum for a couple of years this is my first post. Two years ago I was intending to restore my AR16 speakers but misplaced the woofers which I had taken out of the cabinets. Luckily a few weeks ago I found them. I have owned the AR16 s from new in January 1977. In 1993 I stopped using them when the foam surrounds had perished too badly to continue using them and risking damage to the speakers. I have already received the replacement surrounds and glue from goodhifi.com in the Netherlands. They advised me that the new surrounds were about 5% stiffer than the original but the new material should last considerably longer. The web page reference is :-

http://www.speakerrepairshop.com/index.php?item=foam-ring-for-acoustic-research-ar16-_8-inch_-woofers&action=article&group_id=10000033&aid=1431〈=en

I have started removing the perished foams and glue. I watched the video to which I was referred by goodhifi but it was in the Dutch language and they were working on a plastic coned speaker. I am happy to continue working on the speaker frame to get rid of all remnants of foam and glue, but I am worried about what more is needed to clean the cone's edge. I do not want to damage it. I would welcome any tips and advice from anyone who has experience of refoaming. If all goes well I have attached an image of my speaker, so you can see what the edge of the cone looks like at the moment. There is still some black dust there.

So my main questions are :-

(1) What do I need to do to the cone's edge to prepare it for the new surround?

(2) How do I ensure that I do not pull the cone off centre or in or out when attaching the new surround?

When the surrounds are fitted I intend to replace the capacitors and whatever other parts are necessary in the crossovers. Again any help would be greatly appreciated.

Regards from Jeff

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The most important reason for cleaning the cone is to make sure that when you glue the new surround down it makes a proper seal. So it doesn't have to be perfectly clean, just good enough for a seal.

Personally I refoam by first, doing it by feel, then running a 30Hz tone at low volume through it. If the 30Hz tone sounds good, then I let it dry and move on to the next one. If not, I would then take the surround off and reposition it.

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Thanks for your suggestions canuckaudioguy. I had learned about feeling whether the cone was centred by carefully depressing it. Hopefully there should be no scraping sounds, but I like your idea of passing a 30Hz test tone through while there is still time to reposition the surround before the glue is fully set. I do not have any signal generator or anything like that, but with a bit of delving into how it is done I should be able to produce or get hold of a computer wav file which I can pass through my amp to the speaker.

It's the black dust remnants of the original foam surround that remain a concern. When these speakers were put away in 1993 with perished foam, the repair may have been a little different to now. The foam was merely perished foam. By 2013 the foam has degenerated into a black dust, which may thwart the action of the glue when the new surround is fitted.

As an aside I never realised back in 1993 that the foam surrounds could be replaced. My local hifi shop did not suggest such a repair. They contacted suppliers for me and said I could have replacement woofers for 150 GBP. I paid 105 GBP (usual price was 156) for these speakers when new in January 1977 and, for economic reasons, I thought the 150 GBP would be better spent towards a new pair of speakers.

Any other tips or words of warning from anyone? I have no experience in carrying out this sort of repair.

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Hi Jeff, and welcome to CSP.

I think you are on the right track already, but you are asking good questions. I do not personally know much about the AR-16 speaker, but I have re-foamed similar 8" AR woofers with the same textured paper cone. Also, all of my re-foams have involved dust cap removal or replacement with shimming, but many people do swear by the test tone method of centering the voice coil.

Just two thoughts here to offer. First, it's probably a good idea to at least test and check, if not replace, the capacitors. Not sure what this crossover has for components, but it could still be a smart yet modest investment to simply replace them, particular if they are NPE's. Secondly, the foam remnants remaining on the cone. Your woofer looks very similar to mine, and my approach was to remove, with fingers (but no chemicals or abrasives) all of the remaining foam glued to the cone. The glue appears to be the elastic type, much like rubber cement, and you may find that it peels off relatively easily in long pieces. My intent was to be able to glue the new surround's inner diameter directly to the paper cone, and not to deteriorating foam remnants.

Hope this helps, and also take a look at these posts:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7498

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=5104

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4351

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=1568

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Thank you for your input ra.ra. I think I will have to go along with the "feel" and test tone method for ensuring the cone is centralised. Removal of the dust cap without compromising the paper cone looks a delicate job in itself, and may be a job too far for my untested capabilities.

Thank you for the links to the topics on the AR16, I had already seen most of them but not all. So thanks for bringing those topics to my attention. There is one that you missed which shows pictures of the crossover before and after a restoration.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7530&page=1

It is my intention to replace capacitors, and whatever else may need replacing in the crossovers.

As for the remnants on the cone edge, I had already removed the rubbery beads of glue which separated from the cone reasonably easily in long threads. I am now carefully removing what is left with my fingers as you suggest, but some of what is left is extremely stubborn. If I dig away gently with my nails it is difficult to be certain that I am digging away at the remnants of foam and glue or too much of the fibre of the paper cone, but I am happier now with the look of the cone edge than it was previously. I will continue to take it steady for the rest of this task..

Thank you for your advice, and if anyone else has any snippets to offer I would be most grateful.

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  • 3 weeks later...

I could do with some more help with my AR16 restoration. My woofers have been out of their cabinets for 20 years, and I have been pondering over the re-installation concerning the polarity of the woofers. On each woofer there is a largish black dot which looks like it has been made with a black permanent ink marker on the woofer basket next to one of the wiring terminals. Now is this something that AR would have done during manufacture/assembly, or is it something I have done when I removed the woofers from the cabinets? If I made the marks I do not remember whether I made a black mark next to the negative terminal, or the positive terminal. If I made the marks it I probably only had a black marker pen to hand at the time.

I understand that it it is important to get both woofers in phase, but how crucial is it to get the woofers the same polarity as the mid/tweeter?

For those that may be wandering how the re-foam is going, I have now watched many videos on YouTube, but am still concerned about centreing the voice coil. Without any surround to support the cone it is difficult for me to exercise the cone without feeling and hearing scratching sounds. Is this normal? Once in a while the cone will complete an excursion without scrathing so I suppose it will be possible to centre it up when the surround is in place.

I have decided I will do the re-foam tomorrow. The replacement capacitors should arrive today, so I will have an incentive to bite the bullet and get the job done. I very much appreciate all help offered.

Jeff.

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Hi Jeff

The easy way to check polarity is this: Use a battery (any kind of 1.5v will do, even a used one). Touch one end of the battery to one speaker terminal, the other end to the other. If the cone moves outward, the terminal connected to the positive end of the battery is positive.

Kent

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Success. I did the re-capping on 3 December and the re-foaming on 4 December. I have now re-assembled them into the cabinets. They sound wonderful. I must have maintained an acoustic seal (with speaker gasket foam) because there is plenty of bass, although the cones do return fairly instantaneously when gently pushed in.

I thought I would put a short note about my experiences refoaming these speakers in the hope that it may help other novices undertaking this task.

I thoroughly cleaned the speaker basket of foam and glue with a box cutter work-knife and sandpaper.

I removed most of the foam and glue from the paper cone by carefully pulling it away with fingers.

I removed the stubborn remnants of glue from the cone's edge by gently digging away and pulling at it with my thumb nail, while supporting the underside of the cone with my index finger.

I decided to glue the new surround to the cone edge first. I brushed the glue onto both the cone edge and the back of the foam surround where they would make contact. While the glue was curing/setting, I tried to get the surround nice and concentric, and kept pressing the new surround to the cone edge to ensure a good seal as the glue set.

I then got the computer and amplifier set up so all would be ready to deliver a 30Hz test tone to the speaker.

I then brushed a layer of glue to the speaker basket and the back of the foam surround where they would make contact. I pressed the foam surround into place while trying to keep it nice and concentric.

Within ten minutes of doing this I connected the speaker up to the amplifier. I set the computer software to play the 30Hz test tone repeatedly.

I started with the volume fairly low but turned it up until I could see the cone vibrating and could hear the bass tone.

(On the first woofer I tackled) I heard a sort of low frequency buzzing / flapping sound. I was able to gently manoevre the foam surround until the flapping sound stopped. There was no need to completely remove the new surround and the manipulation was very minimal.

I stopped the test tone and gently pressed on the surround edge and speaker basker to get a good seal as the glue dried.

I played the test tone again to ensure that I was still getting a clean tone with no flapping.

I stopped the test tone and gently pressed on the surround edge and speaker basker to get a good seal until the glue dried.

With the second woofer there was a clean test tone at the outset.

Here are some pictures of my (British made) AR16 s in teak veneer finish. Note how similar the grain is to the AR16 of "audiochat" in another thread

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7530&hl=

I hope I've remembered how to attach photos. I custom made the replacement grills after the original foam grills crumbled to dust. The heavy steel stands were made for me by a friend of a friend

I would like to say a big thank you to this forum. I stumbled upon it two and a half years ago, and it was then that I first realised that my speakers could be restored. I am thrilled that they are restored and sounding wonderful. I would also like to thank the individuals in this thread who gave me the tips and advice to allow me to complete this repair with success.

Best wishes to all from Jeff

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