AR-7 refoam questions

[Lucky Pierre]

Greetings,

I picked up a pair of AR-7 last week for short cash.  Sequential low s/n, real walnut veneer, foam surrounds, front wired tweeters.  Spent the weekend doing the cabinets.  I sanded down to bare veneer (up to 320 grit), applied 4 coats of Danish Oil (med. walnut) with 600 grit sanding in between.  The cabinets are gorgeous!

I have to refoam the woofers and have a couple of questions.  I have done this before to speakers I did not really care about.  Then, I used a 1.5 V battery to center the voice coils.  Is there any reason to not use this method on these speakers?  I would rather not cut the dust cap to shim the coil.

Is there a preferred vendor for woofer surrounds.

Would anyone happen to have a single AR-7 badge laying around?

Thanks!

Peter

[ra.ra]

Unless there are extenuating circumstances, I tend to re-foam using the shim method - - see AR-7 woofers re-foamed this past summer. Regarding foams, I've tended to follow Roy's recommendations as noted below. Apparently MSound is no longer conducting business, but these foams should be available from other vendors.

[Lucky Pierre]

Thanks ra.ra.

Does the vendor make a difference?  I see that Parts Express sells them.  I have to order a bunch of caps, too, so one  sales order would suit me.

Peter

[ra.ra]

I do believe the vendor might indeed make a difference, but others will be able to advise you with more current info than I can - - I re-foamed a number of AR 8" woofers fairly recently with Bose/JBL foams I had purchased a while ago (can't remember exactly where offhand, but will continue to look into it) and I can attest that they fit very well and perform just fine, too. I do like the "fillet" shape of the BA foams, but I've never personally used them in the 8" size, which I suppose can be more challenging due to the radius being tighter than the 10-inchers I have used. Hopefully, others will chime in with their positive recommendations. I totally understand the notion of trying to combine a parts order - -  most of the suppliers are fleecing us for S&H charges for a tiny package that weighs next to nothing.

My pair had the typical "ugly duckling" look once when you peeked under the hood (see pic), but I've got them looking pretty snazzy now. The woofers had that little ring of solid goo that bridged the cone-to-surround joint, and along with the crumbling foams, it peeled right off like a string of rubber cement. Couple other detail items of note: the original blue Sprague 6uF 50V caps in mine (s/n 0058XX) did not require replacement; and the wood veneer on these is most likely birch species stained to appear much like walnut.

Share some pics if you can - -  we all like to see the rescued speakers, before and after restoration. 

 

[JKent]

This is a good vendor

http://www.speakerworks.com/default.asp

Personally, I would not go with PE because I believe (I could be wrong) their surrounds are pretty generic. I'd follow Roy's advice and get the Boston filled fillet type or the JBL.

Nice find on the 7s! The real wood veneer is hard to find.

And use shims!

-Kent

[Lucky Pierre]

Thank you, Gentlemen!

I have bought surrounds from speakerworks before.  To them I will go again.  And I'll use shims

Forgive what may be a naive question, but can you test caps while they are in the circuit?  I was under the impression that they had to be fully isolated to test them.  I was going to replace them with Daytons since I had the cabinets open.

In my rush to start these, I didn't take before pics.  Here they are with the cabinets almost done.  And the ugly duckling baffle.

 

 

[Lucky Pierre]

I was under the impression that early 7s were walnut stained birch.  The grain on these is like no birch I have seen before.  Here are some pictures of the tops.   For some reason I can't upload the two pictures.  Got it.

If you look at the pictures of the tops, the grain on these is fairly open.  If you click the picture and enlarge to full size, you can see the grain well.  The s/n on these are 004837 and 004938

 

[ra.ra]

Those look really nice - - drivers, cabs, grilles, thanks for the pics. Yours are even a little earlier than mine (which have tweeters dated from Jan. 1973). A single badge for yours will turn up in due time. Also, if you have decided to use shims , try to preserve the original dust cap so that the woofers maintain their distinctive look. It's not that difficult - - the cardboard is pretty stiff but a fresh #11 X-acto blade makes a clean cut.  

The wood grain on yours is very similar to what I've seen, and I agree, if I hadn't learned from this forum (historian Tom T, of course) that this veneer was birch (in disguise) I never would have guessed it. Just a suggestion, but an extra hour of investment here and there to snazzle up the "naked" appearance is well worth it, IMO. "After" pic of same speaker shown earlier is attached. Also, always a good idea to rotate woofers 180 degrees from original position.

 

[DavidR]

7 hours ago, Lucky Pierre said:

Thanks ra.ra.

Does the vendor make a difference?  I see that Parts Express sells them.  I have to order a bunch of caps, too, so one  sales order would suit me.

Peter

I've ordered surrounds from Simply Speakers and P.E. Both were very thick and less compliant than the better ones that are available. I sent them back.

[ra.ra]

10 minutes ago, DavidR said:

than the better ones that are available

Specific recommended source(s)?

[DavidR]

Rick Cobb aka looneytune2001 on ebay; but make sure you ask if its the darker, more compliant version he has in stock

vintage-ar on ebay; but make sure you ask if its the darker, more compliant version he has in stock

Springfield Speaker

SpeakerWorks.com (per Roy. I have not used yet)

[ra.ra]

Thx, David. The two foams you show appear nearly identical regarding dimensions (inner/outer lip, roll radius, etc.), so I suppose it is simply the chemistry of the darker foam that creates the more flexible performance. 

[Lucky Pierre]

ra.ra, great tip on rotating the woofers.

What did you do to tidy up the baffles?  Just scrape and paint with flat black?  That looks really nice.

[ra.ra]

Yeah, basically that's most of it. I have done this to my entire modest stable of Classic AR's and it is all simple. With most everything first removed from the cabinet, I'll clean 'em up with a little bit of scraping, sanding, and filling to prepare the baffle for very flat black latex "blackboard" paint. I also seal the particle board recess where the driver frame sits - - sometimes I use duct seal (not this pair, tho') and duct seal can sometimes create such a strong bond that it damages the particle board upon driver removal. At the same time I try to apply a dab of epoxy to the t-nut flanges inside the cab to prevent them from breaking loose in the future.

In the prior pics showing woofer prep, you can see that after cleaning the frame but before applying foam, I partially paint the woofer frame where the foam will attach, but also like to leave the very thin most outer perimeter edge show as raw metal. On this pair, I also touched-up the tweeter cone glue and paint on face plate, and re-applied new electrical tape after soldering. Lastly, I have become fond of using a very thin stainless steel washer under the driver screw heads - - it adds an elegant detail and protects the foam edge as you tighten the woofer screws. One more thing - - on this pair I made new driver gaskets from a sheet of black craft foam, some good circle templates, and a sharp knife blade.      

 

[michiganpat]

2 hours ago, ra.ra said:

Thx, David. The two foams you show appear nearly identical regarding dimensions (inner/outer lip, roll radius, etc.), so I suppose it is simply the chemistry of the darker foam that creates the more flexible performance. 

if you look closely, the one on the left has a larger roll (I'd wager ~5/8" vs. 1/2"), and is most likely the JBL replacement surround often used in AR "kits"

[ra.ra]

 

46 minutes ago, michiganpat said:

the one on the left has a larger roll

Your eyes may be better than mine 'cuz I simply couldn't tell, and if so, that bit of extra excursion certainly could account for the stated preference, but David mentioned only foam thickness regarding dimensions.

[RoyC]

16 hours ago, DavidR said:

Rick Cobb aka looneytune2001 on ebay; but make sure you ask if its the darker, more compliant version he has in stock

vintage-ar on ebay; but make sure you ask if its the darker, more compliant version he has in stock

Springfield Speaker

SpeakerWorks.com (per Roy. I have not used yet)

The photo posted by David shows two versions of foam replacements for the AR 12 inch woofer. The one on the right is thicker, with a slightly smaller and less uniform roll. These are not relevant to the 8 inch foam discussion, as there are no replacements available specific to an AR 8 inch woofer.

Unfortunately, the once favored Bose/JBL replacement being sold now is not as compliant as it used to be. The Boston surround is easily the most compliant replacement, but is a bit wider, and can be harder to install on some AR cones. Just about every 8 inch replacement will fit an AR woofer, but they all fit somewhat differently.

This is my favorite retailer at the moment, as they seem to carry replacements others do not..  http://www.speakerworks.com/default.asp

Roy

 

[Robthomp]

On 2/28/2017 at 3:47 PM, RoyC said:

The photo posted by David shows two versions of foam replacements for the AR 12 inch woofer. The one on the right is thicker, with a slightly smaller and less uniform roll. These are not relevant to the 8 inch foam discussion, as there are no replacements available specific to an AR 8 inch woofer.

Unfortunately, the once favored Bose/JBL replacement being sold now is not as compliant as it used to be. The Boston surround is easily the most compliant replacement, but is a bit wider, and can be harder to install on some AR cones. Just about every 8 inch replacement will fit an AR woofer, but they all fit somewhat differently.

This is my favorite retailer at the moment, as they seem to carry replacements others do not..  http://www.speakerworks.com/default.asp

Roy

 

Roy and all,

I'll be refoaming a pair of 10" woofers as part of my first AR restore - a pair of AR-2ax 's circa 1970.  I found this thread searching for best foam surround product to use.  I have a question - this vendor and others that sell the Boston 10-inch FF surround in a kit, don't seem to include dust caps or shims.  I get that I can reuse the dust cap by carefully separating it from the cone, leaving a "hinge", and then gluing it back, but what do I use for shims, since they're not included?

Thanks,

Rob T.

 

[JKent]

you can usually use strips of business card, 3x5 card, etc depending on the thickness. Or maybe contact the vendor and ask

-Kent

[ra.ra]

Thx....... to Roy for clarifying the pic of foams we were discussing.

The whole idea of a "kit" is to provide all of the necessary components to complete the job for a first-timer, so the vendor's listing is possibly misleading or confusing - - always best to clarify with a phone call prior to order. But Kent's comment is still valid - - strips of very thin, stiff materials make very good shims. Got any 8.5" x 11" acetate covers from some useless corporate report headed for the recycling bin? BTW, those Boston 10" surrounds fit very well on the 2ax woofer.   

[RoyC]

27 minutes ago, Robthomp said:

Roy and all,

I'll be refoaming a pair of 10" woofers as part of my first AR restore - a pair of AR-2ax 's circa 1970.  I found this thread searching for best foam surround product to use.  I have a question - this vendor and others that sell the Boston 10-inch FF surround in a kit, don't seem to include dust caps or shims.  I get that I can reuse the dust cap by carefully separating it from the cone, leaving a "hinge", and then gluing it back, but what do I use for shims, since they're not included?

Thanks,

Rob T.

 

Rob,

It is unfortunate that many sellers do not include shims. PM me with your mailing address and I'll send some to you. I always use the "hinge" method with AR's flat dust caps. It's very easy to do using an exacto knife.

AR woofers (and most woofers of any brand) can be re-foamed using shims of .01 or .007 inch. Only the AR 12 inch woofer requires the larger size.

Roy

[Robthomp]

Thank you all, this forum is deeply informative.  There are a lot of vendors selling refoam kits, labeled for AR speakers. Without this forum I wouldn't have had any way of knowing that the Boston 10-inch FF  was a good choice for the AR-2ax.

Rob

 

[Lucky Pierre]

On 2/27/2017 at 8:44 PM, ra.ra said:

 

The wood grain on yours is very similar to what I've seen, and I agree, if I hadn't learned from this forum (historian Tom T, of course) that this veneer was birch (in disguise) I never would have guessed it. Just a suggestion, but an extra hour of investment here and there to snazzle up the "naked" appearance is well worth it, IMO. "After" pic of same speaker shown earlier is attached. Also, always a good idea to rotate woofers 180 degrees from original position.

 

I refoamed the woofers with surrounds from speakerworks.  Cutting the dust cover was a bit nerve racking.  Recapped them last weekend.  I haven't had a chance to listen to them yet. 

I have confirmed that the veneer on these is mahogany.  Did AR offer different veneers from the factory?

 

P

[ra.ra]

Good to hear about the progress, and of course, we'd love to see pics of your results and hear impressions of the listening experience. Am curious to know why you felt the need to re-cap? Did these have the original blue 6uF Sprague Compulytic? Also, about the veneer species, I would agree that the fine grain figure of the wood graining does bear a strong resemblance to mahogany (both yours and mine), but again, I was simply re-stating comments about the birch that had previously been aired in this forum. There appears to be no AR literature suggesting mahogany as an offered finish for the AR-7, so what means did you use for confirmation? Most domestic AR-7's were clad in faux-walnut vinyl, but the predominance of Euro versions seem to sport real walnut or teak veneer.