Need help for AR-12 refurbish

[rumblestrip]

Picked up this pair of AR-12's the other day for a song. Almost passed them by because they have been painted brown over the original walnut veneer so that they looked like cheapies. Otherwise in excellent shape and complete except for the rotted-away foam surrounds and dispersion rings on the tweeters. Got them home only to find that one of the midranges is dead. Took them both out to measure the resistance on the one still working. It metered out at 3.6 ohms. Does this mean the midranges were originally 4 ohm speakers or could they be 6 or even 8? Does anyone have any experience with these so that they would know for sure? If so please let me know. There is very little about this model online. Also, is it worth having just the one recoiled, or should I do both?

[Anthropologo]

Picked up this pair of AR-12's the other day for a song. Almost passed them by because they have been painted brown over the original walnut veneer so that they looked like cheapies. Otherwise in excellent shape and complete except for the rotted-away foam surrounds and dispersion rings on the tweeters. Got them home only to find that one of the midranges is dead. Took them both out to measure the resistance on the one still working. It metered out at 3.6 ohms. Does this mean the midranges were originally 4 ohm speakers or could they be 6 or even 8? Does anyone have any experience with these so that they would know for sure? If so please let me know. There is very little about this model online. Also, is it worth having just the one recoiled, or should I do both?

I have a pair that I just picked up at an estate sale - thrown in with other stuff I bought cause the little old estate sale ladies didn't want to have to carry them out if they didn't sell - on these one of the tweeters is blown and I am not going to pay $129 for a used one from a known ebay vendor - that kind of pricing defeats the "do it yourself" ethos that makes this fun, the mid-range surrounds are shot but both drivers are good, woofers will need re-foamed...anyway, as to impedences using my meter: Tweeter 6.6, Mid-Range 6.5, Woofer 6.7 - so, I will keep surfing ebay in the hopes of finding a more reasonably priced spare tweeter or will look for a pair of replacement tweeters and roll the dice....when i refoam I always do both, regardless....cheers

[RoyC]

The AR-12 was marketed as an 8 ohm speaker. Dcr of the midrange is around 6 ohms.

The last time I checked, there was no replacment available for the midrange foam.

Roy

[docstocker]

I have a pair of AR12 that I bought very cheaply a few years ago. The midrange is an unusual unit that fits into a cylinder. the spear has a cloth? surround which in the case of my speakers, was broken and unrepairable. I toyed with the idea of cutting up one of my wife's silk scarves into a replacement and then rubberising it but the difficulty of cutting the circle out of the material (and the extended period I would find myself spending sleeping in the shed when my wife found out about her scarf) lead me to look on the internet where I found a small foam replacement that fitted extremely well.

I suspect that the measurable characteristics of the speaker have been significantly changed but the speakers now sound very good indeed. I am not sure that they are not my favourite in my collection.

I think that this midrange had some specific virtues or novelties. Even with my fix I am happy with the sound, never having heard the speaker when it was new and at full spec.

I am not sure that there are many pairs of these speakers around. I anyone is interested I will try and remember where I obtained these foams.

By the way, replacement mid range units I have seen on E bay have had foam replacements of the cloth originals

John

[RoyC]

I have a pair of AR12 that I bought very cheaply a few years ago. The midrange is an unusual unit that fits into a cylinder. the spear has a cloth? surround which in the case of my speakers, was broken and unrepairable. I toyed with the idea of cutting up one of my wife's silk scarves into a replacement and then rubberising it but the difficulty of cutting the circle out of the material (and the extended period I would find myself spending sleeping in the shed when my wife found out about her scarf) lead me to look on the internet where I found a small foam replacement that fitted extremely well.

I suspect that the measurable characteristics of the speaker have been significantly changed but the speakers now sound very good indeed. I am not sure that they are not my favourite in my collection.

I think that this midrange had some specific virtues or novelties. Even with my fix I am happy with the sound, never having heard the speaker when it was new and at full spec.

I am not sure that there are many pairs of these speakers around. I anyone is interested I will try and remember where I obtained these foams.

By the way, replacement mid range units I have seen on E bay have had foam replacements of the cloth originals

John

John,

I have only seen (deteriorated) foam surrounds on original AR-12 mids. If the surrounds were made of cloth there would be need to replace them. Your source for new foam would be of interest. The repaired AR-12 mids I've been seeing on Ebay these days have new foam surrounds which have been cut and pieced together to fit.

Roy

[docstocker]

Hi Roy

Thanks for all your useful info on this site. Have been reading it for several years but never felt I had anything useful to contribute.

I have looked again at the old photos I took when restoring the AR12s and although I clearly remember scraping away thick sticky material that I thought was fabric. Looking again today at the pictures I wonder if the material was in fact flat foam.

The replacements were bought from USA via Ebay.

I have only ever bought surrounds from two sources so it must have been either Geoaliwili or speaker works.com

I notice that there is a London UK based seller on Ebay 'onlydiesel0' advertising an AR12 kit.

The surrounds are ridged foam not flat and were not specifically advertised for AR speakers.

The difficulty I had in fitting the foams was from the cone which sits in fluid and can be pulled out or pushed in but needs to be halfway when the foam is attached and no signal applied. It was this added difficulty that made my efforts to cut and fit replacement flat foam surrounds, cut down from larger surrounds, impossible. (for my skill set)

I will try and attach some photos including measurements.

John

[RoyC]

Hey John,

I'm sure they were only manufactured with foam surrounds. There are certainly no flat surrounds available, so any replacement will have a roll.

The use of shims in the voice coil gap will provide friction, and allow the cone to be set at the correct height when replacing any surround..

Roy

[Anthropologo]

As noted earlier in this thread, several months ago I found a McIntosh 1700, ELAC Miracord 50H, and AR-12s. Early morning estate sale lines here in Austin are always a cultural experience and its a good excuse for breakfast tacos.

More often than not, its a bust but in this case the little cotton-top estate sale lady cared nothing for electronics; we exchanged $65 and contact info for whenever else she might run into these "heavy and messy electronic things with their cords" and I was out the door....

Receiver and turntable work fine - speakers are a mess -

• both woofers need refoaming
  
• both mids need refoaming
  
• only one tweeter works - and is an 8 ohm tweeter version - #200011-2 (other tweets from this line are 4 ohm - #200011-1)
  

However,

• cabinets are in beautiful shape
  
• foam covers are intact
  
• both badges are there
  
• I am a sucker for AR....
  

Anyway, am slogging through getting these back to functional and finally got time to post refoaming of AR-12 mids since is a bit out of the ordinary...

Foam was purchased at: http://www.speakerwo...com/default.asp

I purchased 2 of item number SWK3 with a 2 15/16 OD and 2" ID - is a good fit

First thing is to scrape off remains of the nasty black, semi-fuzzy residue adhering to the outer frame

Once that's complete you can better see the rotted surround

Next is to remove all of that rotted surround, the interface between the surround and the cone had become somewhat vague over the years, so cautious scraping and the leaving of a slightly less than pristine surface became the process and yielded the following

Time to place surround - the four tick marks provide the boundaries for best shot at centering

I use a flexible disk (this one cut from thin plastic container lid, for larger diameters I find posterboard works well) to hold down the inner surface over the cone. After glue is applied, the disk is put in place with a weight on top. I have found that the flexibility of the the disk exerts an even horizontal and somewhat downward force onto the cone that results in a tight, uniform seal.

Then I did outer rim-I do it in quarters (seems to work best for centering) and cut an arc from cardboard that matches the surround arc, apply glue, give the cone a good three finger push or two to center, place the cardboard arc over the surround and weight it down until glue cures. No pictures here.

Disk removed and outer rim sealed as well, mid ready to be put back in cabinet.

When I played them, there was sound: with the working tweeter, and a bad woofer the uppers and mids were clear and distinct. However, with the ferrofluid wrinkle and ridge in the new foam, who knows how close I am to what was original sound.

Nonetheless, if you need to refoam a pair of these and don't want to cut apart, custom fit, and then rebond a larger foam (some methods I have seen used on items sold on ebay) then this is one way to go.

Finally, a question, is there any advantage/danger in using the 4 ohm tweeters rather than a pair of new 8 ohm with close to same efficiency dome replacements from parts express? I don't hold any hopes for finding an AR-12 tweeter anytime soon and these seem to be my best options. Any helpful advice appreciated.....

[speaker dave]

That looks like a very clean and professional repair ot me.

I wouldn't worry about having a half roll where the previous surround was flat. Considering the alternative (dead speakers) it seems like a good choice. Clearly AR knew that the excursion required was nil and so gave it a flat surround, but foam surounds are fairly light and I'd bet the response is little changed.

David S.

[david]

On 05/06/2012 at 4:57 AM, RoyC said:

The AR-12 was marketed as an 8 ohm speaker. Dcr of the midrange is around 6 ohms.

The last time I checked, there was no replacment available for the midrange foam.

Roy

Hi Roy, I don't think there is a direct replacement. Springfield or SimplySpeakers supplied to me an equivalent which with a bit of adapting fitted OK. However. It is the actual process of fitting that is difficult due to the small size and angles on the surfaces. My problem was holding the cone in position to allow the adhesive to set - as the cone has a tendency to sink deep into the assembly ruining any seal and pulling off the new foam.

My improvised solution! I held the cone in place with several toothpicks and worked around the edge gluing the new foam in two or three stages. I would wait for one part on the edge to dry and then work round to another section. After gluing a couple of sections like this the cone was fairly well held up to the required position. 

The two important aspects to keep checking while you do this and double check at the end is 1. cone moves in and out smoothly no rubbing 2. the new foam is a perfect seal all the way round

Finally - and Larry at vintage_ar is quite right about this - why go through all that time and trouble only to ruin the job by reusing the old gasket seal on the driver to cabinet which has to be air tight to get the "AR sound"? Use a new gasket or buy sealing tape (or compound) to get that air tight seal when replacing all the drivers.

Cheers David

[lakecat]

SpeakerWorks that was mentioned above has the exact size foam needed. Has the slight roll and not flat but my mids sound fantastic. 

[RoyC]

4 hours ago, lakecat said:

SpeakerWorks that was mentioned above has the exact size foam needed. Has the slight roll and not flat but my mids sound fantastic. 

Agreed, Jeff. Subsequent to my 2012 post I found SpeakerWorks.com to have a good AR-12 replacement, as well as other hard to find items...excellent retailer. http://www.speakerworks.com/speaker_repair_kits_s/65.htm

Roy

[GD70]

I also got the mid surrounds from Speakerworks.

Excellent sounding speakers that were a one year only model.

I have a thread showing the restoration if you're interested.

Nice work on your mids. It brought back memories!

Glenn

[Keno]

How about replacement tweeters for these model?

[GD70]

The originals are specific to the 12 as well as the mids. 

[AR55]

If you plan to refinish your AR-12's, note that the veneer used by AR is fairly thick and can be easily sanded if you are careful.  I picked a pair of AR-15's on eBay that had been painted black and they turned out to have a beautiful veneer under the paint.  Why anybody would have painted them in the first place is beyond me.  The attached photo shows one speaker still painted black with the other refinished.

There have been a number of refinish options discussed in the forum.  I used Watco Danish Oil.  Wet sanding the first coat and adding 3 additional coats.

[david]

Keno, I believe the AR12 tweeters are totally unique to just that speaker model. So if you ever see any up for sale jump on them. I am not sure about the mids - they were a gel cooled design and might also be used in other models in that line. Even so, drivers for the AR12 hardly ever come up for sale. You can try ar_vintage on Ebay. com (might be vintage_ar) he carries a good inventory of used parts and NOS and will advise. 

Cheers David

[fedeleluigi]

On 9/16/2018 at 8:30 PM, Keno said:

How about replacement tweeters for these model?

Keno, you could use not original tweeters but you have to adapt the driver flange to the cabinet hole and modify the crossover network. If you want to do a good job you should use a speaker simulation software and in the end carry out some measurements.

Imho, If you don't want to do all this and wish to keep the AR 12 originality as far as possible,  today the best option is to use the  replacement tweeters supplied by Midwest Speaker Repair. The 8 Ohm version is the correct one for the AR 12.  It's a drop in replacement tweeter and If you use the 8 Ohm version you do not have to modify anything.

 Some members of this forum have already used these replacement tweeters (the 4 Ohm version) for some restoration of 4 Ohm AR speakers. 

Luigi

- https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/

- https://www.ebay.com/itm/AR-Acoustic-Research-Replacement-8-ohm-Tweeter-for-AR-2ax-AR5-LST-2-MT-4121-8/162689351715?hash=item25e10a8023:g:k~kAAOSwc8lZzEo4

[david]

Always replace as a pair, otherwise your Left Right will be thrown out of balance. I replaced an AR92 tweeter with NOS driver and it sounded very slightly forward more brighter than the original in the other box. Just laziness and getting time to replace the other one and seems a shame!!! 

Ideally pairs it is!

[scottie munoz]

On 6/11/2012 at 10:35 AM, RoyC said:

John,

I have only seen (deteriorated) foam surrounds on original AR-12 mids. If the surrounds were made of cloth there would be need to replace them. Your source for new foam would be of interest. The repaired AR-12 mids I've been seeing on Ebay these days have new foam surrounds which have been cut and pieced together to fit.

Roy

Very interested your source for mid foam..5 year's layer, haha.

Scottie

[GD70]

On 8/10/2022 at 12:36 AM, scottie munoz said:

Very interested your source for mid foam..5 year's layer, haha.

Scottie

Mid surrounds from Speakerworks. Worked out well on mine.

[scottie munoz]

Thank you, Glen.

[GD70]

15 hours ago, scottie munoz said:

Thank you, Glen.

Here’s the link to my resto thread. May have some useful info.

Cheers, Glenn