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AR7 advice please.


Elsdon
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Hi! I saved this pair of AR7s from the bin. In thier original box with instructions. Looks like they've been refoamed before with some glue residue, some of which has pealed off. 

Thoughts? Can I get these bad boys sounding good again? 

Thanks!  

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Great find, as RickB already said, the speakers are easily restorable: correct new foam, check value of the condenser (if Sprague should be in place), cleaning of the teak veneer, subsequent treatment with Linseed oil (or other favorites) and you will have a magnificent pair of AR7s.

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On 9/3/2021 at 6:05 AM, Giorgio AR said:

Great find, as RickB already said, the speakers are easily restorable: correct new foam, check value of the condenser (if Sprague should be in place), cleaning of the teak veneer, subsequent treatment with Linseed oil (or other favorites) and you will have a magnificent pair of AR7s.

Condenser? Sprague? Help! 

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A condenser is a capacitor. Sprague is the manufacturer of the original. Picture below. It's probably still good. Value is 6.2uF (microfarads) but a 6uF film replacement will be fine if needed. The capacitors are kind of old but Spragues were high quality.

Most were "wood grain" vinyl. Yuk. Yours say "Teak." I've never heard of that. I had a pair that were stained birch. Maybe yours are European. Does it say where they were built? The teak must be rare! You can clean them up with some Howard Restor-a-Finish, Natural if needed. I don't think Boiled Linseed Oil is the best choice. There is a product called Teak oil but even that may not be needed. They look like they're pretty clean.

Have you played them? How do they sound? Doing a re-foam yourself is not difficult or you can send the woofers to Millersound in PA for an excellent refoam job. But "if it ain't broke, don't fix it." You may not need to do a thing to these speakers.

AR7 xo.jpg

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I agree with Kent. Wherever they were manufactured these appear to be late production specimens, which will probably work fine without worrying about capacitors/condensers. You can always learn more about such things after having the woofers taken care of and giving them a listen.

Roy

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8 hours ago, genek said:

"Teak oil" is an absurdly expensive product originally formulated to weatherproof teak boat decks. There's no need to use it for any indoor applications.

Ok. So what do you recommend for teak veneer speakers?

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Assuming that refinishing is needed, my current go-to for an oiled finish is Tung oil cut with a citrus solvent. For a coating finish, wipe-on varnishes or "danish oils" don't vary a lot by brand.

But if the side faces of these are in the same condition as the front edges, they probably don't need anything more than some cleaner/polish.

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16 hours ago, JKent said:

A condenser is a capacitor. Sprague is the manufacturer of the original. Picture below. It's probably still good. Value is 6.2uF (microfarads) but a 6uF film replacement will be fine if needed. The capacitors are kind of old but Spragues were high quality.

Most were "wood grain" vinyl. Yuk. Yours say "Teak." I've never heard of that. I had a pair that were stained birch. Maybe yours are European. Does it say where they were built? The teak must be rare! You can clean them up with some Howard Restor-a-Finish, Natural if needed. I don't think Boiled Linseed Oil is the best choice. There is a product called Teak oil but even that may not be needed. They look like they're pretty clean.

Have you played them? How do they sound? Doing a re-foam yourself is not difficult or you can send the woofers to Millersound in PA for an excellent refoam job. But "if it ain't broke, don't fix it." You may not need to do a thing to these speakers.

AR7 xo.jpg

Thanks! It doesn't say the place of manufacture, just the UK company address on the card. 

They are quite clean, a few marks here and there but very nice. 

I haven't played them yet as there's no foam on the woofers at all,  didn't think it would be a good idea. If anyone has any guidance on refoaming it would be much appreciated as I'm a rookie! I'm also in the UK so Millersound would be a stretch 😁 

Thanks again.

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Beautiful! So if they were sold in the UK and the veneer isn't what was used here my guess is they were built in the UK. And is that where you are? Sorry--somehow I totally missed the missing foam part but you're right: Don't play them until fixed. Where you get the foam depends on which side of the pond

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I re-foamed and re-capped my speakers which had 8 inch woofers several years ago. If you are reasonably handy at DIY stuff, and take reasonable care in preparation, you should be able to do the repair yourself. I am in Birmingham UK so had limited access to replacement foam surrounds like yourself. The grain on your speakers resembles mine which are also in teak veneer. Here's  an extract from  my thread asking for help.

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 basket 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 basket to get a good seal until the glue dried.

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

I suggest you watch some YouTube videos of similar repairs. Try and find repairs of similar paper coned units because although the process is the same I imagine polypropylene cones are  different to scrape glue from.

Here is a link to the full thread, where you may pick up other tips and avoid pitfalls, but I am sure there are many other threads to guide you through this repair. Good luck with your repair.

Refoaming AR16 speakers - help needed - Acoustic Research - The Classic Speaker Pages Discussion Forums

There is a shop in the Netherlands which can provide surrounds and glue for your AR-7

Foam surround to repair Acoustic Research AR7 woofer (speakerrepairshop.nl)

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Elsdon,

Jeff gives some good advice. The only things I would add are:

  1. A better way to center the voice coil and avoid the buzzing Jeff found is to use shims instead of the test tone. However, many people report success with the test tone method.
  2. The glue can make a world of difference. There are 2 types: solvent-based and water-based. The solvent based glue is used for plastic cones and many suppliers sell it for use on paper cones as well. It's smelly, messy, unforgiving stuff similar to contact cement. For a first-timer especially it should be avoided. Mistakes are very difficult to correct. The water-based glue is white PVA glue. Here in the US we can buy Aleene's Tacky Glue, which is identical to the PVA glue sold with speaker surrounds. Elmer's glue and carpenter's glue are similar. The white glue can be spread with your finger, any squeeze-out can be cleaned up with water and it takes a while to dry so mis-alignments can be pulled apart and re-done. I can't say this strongly enough: Only use white PVA glue for your re-foam project.

By the way, I buy surrounds from https://www.speakerworks.com/Default.asp  I don't know if they ship to the UK but they have the right foams and glue and they are very helpful. Just note they sell them per each so you need to buy 2. 

Good luck.

Kent

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On 9/7/2021 at 2:22 AM, JKent said:

Beautiful! So if they were sold in the UK and the veneer isn't what was used here my guess is they were built in the UK. And is that where you are? Sorry--somehow I totally missed the missing foam part but you're right: Don't play them until fixed. Where you get the foam depends on which side of the pond

I am in the UK yes. EBay has a lot of foams that come from China and take quite a while. 

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On 9/7/2021 at 1:18 PM, Jeff_C said:

I re-foamed and re-capped my speakers which had 8 inch woofers several years ago. If you are reasonably handy at DIY stuff, and take reasonable care in preparation, you should be able to do the repair yourself. I am in Birmingham UK so had limited access to replacement foam surrounds like yourself. The grain on your speakers resembles mine which are also in teak veneer. Here's  an extract from  my thread asking for help.

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 basket 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 basket to get a good seal until the glue dried.

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

I suggest you watch some YouTube videos of similar repairs. Try and find repairs of similar paper coned units because although the process is the same I imagine polypropylene cones are  different to scrape glue from.

Here is a link to the full thread, where you may pick up other tips and avoid pitfalls, but I am sure there are many other threads to guide you through this repair. Good luck with your repair.

Refoaming AR16 speakers - help needed - Acoustic Research - The Classic Speaker Pages Discussion Forums

There is a shop in the Netherlands which can provide surrounds and glue for your AR-7

Foam surround to repair Acoustic Research AR7 woofer (speakerrepairshop.nl)

Brilliant, thanks! I'll keep you posted! 

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On 9/7/2021 at 1:51 PM, JKent said:

Elsdon,

Jeff gives some good advice. The only things I would add are:

  1. A better way to center the voice coil and avoid the buzzing Jeff found is to use shims instead of the test tone. However, many people report success with the test tone method.
  2. The glue can make a world of difference. There are 2 types: solvent-based and water-based. The solvent based glue is used for plastic cones and many suppliers sell it for use on paper cones as well. It's smelly, messy, unforgiving stuff similar to contact cement. For a first-timer especially it should be avoided. Mistakes are very difficult to correct. The water-based glue is white PVA glue. Here in the US we can buy Aleene's Tacky Glue, which is identical to the PVA glue sold with speaker surrounds. Elmer's glue and carpenter's glue are similar. The white glue can be spread with your finger, any squeeze-out can be cleaned up with water and it takes a while to dry so mis-alignments can be pulled apart and re-done. I can't say this strongly enough: Only use white PVA glue for your re-foam project.

By the way, I buy surrounds from https://www.speakerworks.com/Default.asp  I don't know if they ship to the UK but they have the right foams and glue and they are very helpful. Just note they sell them per each so you need to buy 2. 

Good luck.

Kent

Thank you! I'll let you know how it goes! 

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Might be a good idea to take the woofers out (take a picture of the speaker connections before disconnecting the wires) and do a quick 1.5volt battery check (battery attached to jumper leads and a momentary touch with jumper leads) across the speaker terminals. If the cones move or make a noise then the voice coils are good and surround replacement should commence. If they don't move or make a noise you'll probably need to start looking for a replacement woofer. Of course you could measure the resistance of the coils with an ohm meter as well.

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9 hours ago, DavidR said:

The glue on the woofer surrounds appears (to me) like it might be silicone rubber.

Let us know if it is. It will have to be fully removed before a 'proper' glue can be used successfully.

I have re-checked Elsdon's photo' of the woofer cone. The "silicone" appears to me to be a bead surrounding the cone applied during manufacture by AR. (on mine it was a double bead). The bead(s) peels away fairly easily in long threads if you ease it away carefully. It is elastic, and nowhere near as stubborn as the glue remnants I had to deal with on the cone's edge.  (For info' I think those bead(s) were applied at the factory to reduce sound wave diffractions at the cone's edge - others may may know more about this). It is a thing that will be almost impossible to replace with a DIY repair. 

If Elsdon decides to buy foam surrounds from the Netherlands I can reassure him that the glue that they can also provide is the proper white milky rubber glue which turns transparent when set.

As for one of Kent's other main points about "shimming", that is probably the better way to go, but for us novices it is rather daunting cutting away the dust cover such that it can be reused afterwards. Also I would say that shimming would be much more important way to go about a repair on larger 10 inch and 12 inch woofers. Elsdon will have to decide which way he wants to do it.

 

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10 hours ago, Jeff_C said:

I have re-checked Elsdon's photo' of the woofer cone. The "silicone" appears to me to be a bead surrounding the cone applied during manufacture by AR. (on mine it was a double bead). The bead(s) peels away fairly easily in long threads if you ease it away carefully. ...........................................................................................

If Elsdon decides to buy foam surrounds from the Netherlands I can reassure him that the glue that they can also provide is the proper white milky rubber glue which turns transparent when set.

The outer surround edge to the woofer frame/basket not the bead on the outer edge of the cone.

The bead AR would put on some of the woofer cone outer edge was, I believe, rubber cement which is quite different than silicone rubber. Silicone is the issue.

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Your comments are noted @DavidR. It is a good thing for Elsdon to have as much information from members as is available.

Another tip I can offer is to have some of those wooden metal sprung clothes pegs available to clamp the surround to the speaker basket to keep the surround in place as the glue sets. He has probably seen the pegs in videos that he may have watched but I thought it would be a good idea to mention it again here.

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