37 replies to this topic

[ben76]

Hi everybody,

My father recently got hold of a pair of AR2ax with woofers in need of re-foam. The mysterious thing is that although the drivers look original (at least to me) the cones look like they have a flat edge and not an angled one!

All the re-foaming kits I have seen for the AR 10" woofers seem to be targeted at angled cone edges, and I was told that AR never made woofers for the AR2ax with a flat edge!

Both woofers look identical in all respects: basket, magnet, cone material and
shape, and dust cap. The basket looks like stamped steel, and one of
them has a stamp on the magnet saying "Feb 3 1972". They both have
exactly the same paper cone with a 2-1/4" felt dust cap.

Did somebody re-cone both woofers with the wrong cones at some point? (a clue may be a sticker on both woofers reading: "Stuart Elec 1-5-88 UPS" - or maybe URS instead of UPS).

I attach pictures with the hope that somebody will be able to shed some light on this mystery.

Thanks in advance!
Ben


P.S.
I have been reading the posts on this forum for quite a while now, but this is my first post.
I am always amazed at the amount of great advice and knowledge on this forum - it is very educational!

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[ra.ra]

Hi, Ben, and welcome to this excellent forum.

I am currently working on a pair of very similar 2ax speakers with woofers dated Sep 12 and 13 of 1972. My two woofers look identical to yours - tape on alnico magnet, screen backing, four screw holes in basket rim - but your paper cone might have just a slight bit more texture than mine. I don't know anything about the Stuart sticker but still, everything looks fully original from my limited knowledge.

I would not concern myself with the flat profile you refer to. First, I think that after you've taken some time to carefully scrape away all remaining bits of foam, the upper edge of the cone may not appear to flatten out so much. Second, I will be using new foam surrounds obtained from M Sound (contact: John) which have an inner edge which actually extends down the slope of the cone just a smidgen, so that "flat" circumference may not even be the exact line of glue attachment.

Pic of my 2ax's (attached) on the day I brought them home from a yard sale a few months back (sorry about the sideway, don't know what happened). Whaddya think? - - - re-foam in order?

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[ben76]

Hi ra.ra,

My Father has been communicating with John from M Sound, and he said that indeed it is a flat edge, and would require a special foam surround, and not the ones he usually sells for the AR2ax. He also said that the flat edge is not original from AR.

However, I must say that the basket/magnet look very original to me. The fact that your drivers' basket and magnet look the same strengthen my diagnosis. Thanks!

Are your driver's cone edge also flat? or is it angled?

Thanks,
Ben

[ra.ra]

Hmmmm ...... now I'm more perplexed than ever. John is the expert - - let me state that I am by no means very experienced with woofer surround replacement - - but when I purchased my surrounds from John there was never any inquiry into "flat" or "sloped" upper cone edges. In fact, I simply followed the advice of the more experienced CSP members and ordered up a pair of foam surrounds with the "Boston fillet".

I still say you should perhaps clean up your woofers a bit more before making a final determination about the edge profile.

Let me just add that your posted pics are excellent, and I cannot say that I have ever seen a vibrant green spider before. Maybe that's where your woofers are unique!

Pic of rear of my 2ax woof attached. Keep us posted on this mystery.

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[ben76]

There is definitely a flat flare. It is also clearly visible from the back side peering through the basket.

I have read in another post on this forum that the cones of the AR2ax are very soft (relative to the Advent ones) and that this was done intentionally by AR to achieve certain acoustic goals. My cones feel pretty stiff.

I guess that the unusual green color of the spider, the flat edge, and the stiff cone material suggests some kind of a re-cone job in the past (probably by Stuart Elec in 1988).

So guys, please chime in with your conclusions.

Should my father simply replace the foam (with flat edge ones)?
Should he re-cone to a more suitable cone (softer, and angled), and if so, where can he get a re-cone kit?
Or should he look for original drivers?

[ben76]

By the way, I have just noticed that only one driver has a green spider - the other is mustard color.
The voice coils of the two drivers have slightly different DC resistance. The one with the mustard spider is 6 Ohm, and the other is 6.7 Ohm.

Apart from that both drivers and cones look identical.

[tysontom]

That green spider and stiff cone is unquestionably a re-cone assembly, not an original AR cone. it probably works okay, but there might be some differences when compared with the original, side-by-side. The stiff cone would likely exhibit some coloration or frequency-response irregularities at the higher-operating frequencies for the woofers in these speakers.

Original AR cones for the 10-inch (AR-2- and AR-5-series woofers) were definitely softer to allow less cone break-up at higher frequencies. With the first AR-2 and AR-2a woofers (11-inch 6-bolt cast-aluminum frame), the cone was more rigid, and AR used a foam damping ring to suppress the unwanted output at the higher frequencies, so when the changeover was made around 1970 to the 4-bolt 10-inch stamped-frame woofer, a new "high-loss" pulp-wool paper cone was used to give better response.

--Tom Tyson

[ben76]

Thanks Tom for clarifying things!

So, I guess that in order to get the famous Ar2ax sound my father should either re-cone to a proper cone type (is that possible? does anybody carry correct re-cone kits?), or try to find original drivers with original cones, right?

By the way, I read once that AR provided an adapter ring to allow one to fit the newer 4-bolt 10-inch stamped-frame drivers in pre-1970 cabinets that were built for the 6-bolt cast-aluminum frame drivers. If so, I guess that doing the reverse, i.e., fitting a 6-bolt old driver in a new cabinet built for the 4-bolt drivers, would not work since the hole in the cabinet is too small, or am I wrong?

[JKent]

Hi Ben and welcome
The cast aluminum drivers will not fit.
MSound sells recone kits, so that is a possibility. I think someone wrote up a recone job here recently. A bit trickier than a refoam.
If it were me, I'd send both woofers to either MSound or to Millersound in PA and have them reconed by a pro. The downside to buying another pair of AR drivers is you'll spend a lot for old drivers so they'll be a sort of pig-in-a-poke. Having yours rebuilt professionally should yield good results.
Just my 2 cents.
Kent

PS: Here's the recone story, with photos. Start with Post #83 on the 3rd page
http://www.classicsp...hl=recone&st=80

Edited by JKent, 15 April 2012 - 01:35 PM.

[xmas111]

Hi Ben,

I agree with Kent, reconing is probably your best bet.

Contact John at M_Sound and he'll be more than happy to help you out with reconing kits.

I just finished reconing the woofers in my LST's. Very happy with the results.

If you really take your time and follow the instructions John supplies with the reconing kits you should be able to do it yourself.
Or as Kent suggested send them to John to have them done.

John at M_Sound is a real class guy. He'll give you all the help you need.

Either way good luck.

John

[ben76]

I did not know that John at M_Sound has re-cone kits - I could not see any on his website or eBay store.
My Father's impression from communicating with John was indeed very good.

The current cones are fine, and John has a surround that will fit their flat edge, so the only reason to re-cone would be if it will give the original sound without the coloration that Tom said the current cones would probably give.

I have re-coned a few speakers in the past, so that is no problem.

In short (and assuming John indeed has a re-cone kit) would re-coning give the original drivers' sound, or is an original driver with original cones the only way to achieve that?

Ben

P.S.
Should I start a new topic regarding this re-cone or not re-cone question?

[JKent]

Hey Ben
This has not strayed off topic so I think we can continue here.
My only reason for suggesting the reconing is apparently your woofers do not match perfectly. Will it be audible Probably not. The other issue is the fact that apparently the cones are different, so one woofer should have one kind of surround and a different kind on the other. John will certainly make up a mis-matched pair as long as you let him know exactly what you need. Maybe your father should ask John for his advice re reconing. Be sure tend your photos.
I know Roy was instrumental in getting MSound to supply the filled filet surrounds. Let's see if he has an opinion on your plight.
Kent

[ben76]

Hi,

Sorry for the confusion. Both my Father's drivers are identical except for the color of the spider and the slight difference in voice-coil resistance. They both have the stiff flat edge cone.

Ben

[ra.ra]

The Mystery of the Green Spider.

I have looked again at my 2ax woofers (which have been thoroughly cleaned and awaiting re-foaming) and there is definitely no flattened portion at the top of the cone - it is sloped right to the edge. My earlier thought was that maybe yours required a more thorough cleaning for full certainty, but now it seems there is agreement that these cones are non-original. I had mild suspicions about the (visual) cone texture, and while the terms "stiff" and "soft" are relative, I can confirm that my 2ax cones are indeed less stiff than the paper cones of two other 10" woofer speakers in my home which have a heavier gauge of paper cone.

So, if you are convinced that the cones should be replaced, it is most beneficial that you have experience with this procedure - - you should then be able to use the highly regarded "Boston fillet" surrounds from M Sound. But what about the spiders? Tom T has confirmed that the green one is definitely not an AR part, but what about the "mustard" one? The color of the spiders I've seen in AR woofers ranges from a pinky-persimmon to almost a light red wine hue. Leave "as-is" or replace?

[RoyC]

I know Roy was instrumental in getting MSound to supply the filled filet surrounds. Let's see if he has an opinion on your plight.
Kent

Hi guys,

Actually John contacted me a couple of days ago regarding Ben's drivers, and requested confirmation that AR did not use flat edged cones.

My advice is to try to acquire a pair of original AR 10 inchers and re-foam them. Unlike the AR 12 inch big brother, there are many 10 incher's still available at reasonable cost. They seldom go for more than the cost of a re-cone kit.

My primary concern is re-coning may not get Ben back to the "original" sound, as there are often differences between modern replacement parts and the original components...most notably stiffer cones. Getting the spider and voice coil with precisely the "right" specs can also be a bit of a crapshoot. There is even a response difference between AR's mid-70's ceramic magnet version, and the earlier alnico magnet version. (3 ohms was added to the resisitance of the AR-2ax midrange to compensate for this difference.) I'm fairly certain Ben's re-coned woofers do not match the response of the original woofers, but they may be acceptable until he can acquire originals. They could also provide some re-foaming practice. :-)

As an aside, I've ordered a couple of John's/Msound's AR 12 inch woofer kits. They will be installed in original basket assemblies owned by Larry Lagace (Ebay's "Vintage AR") for measurements and comparison to original woofers from the 70's, 80's, and Tonegen replacements of the late 80's/early 90's.

Roy

[xmas111]

As an aside, I've ordered a couple of John's/Msound's AR 12 inch woofer kits. They will be installed in original basket assemblies owned by Larry Lagace (Ebay's "Vintage AR") for measurements and comparison to original woofers from the 70's, 80's, and Tonegen replacements of the late 80's/early 90's.

Roy

I'll be very interested in your results since I just finished reconing both woofers in my LST's using the kits from John.

So far I'm very happy with the results but have to admit I didn't have a lot of listening time with the original woofers as a comparison.

John

[KlausDK]

There is even a response difference between AR's mid-70's ceramic magnet version, and the earlier alnico magnet version. (3 ohms was added to the resisitance of the AR-2ax midrange to compensate for this difference.)

Hi Roy

Was there a similar correction of the X-over in the AR-5? As far as I remember, not. How come the difference?

The X-over in the AR-6 was changed big time, with the introduction of the new ceramic 8" woofer.

As an aside, I've ordered a couple of John's/Msound's AR 12 inch woofer kits. They will be installed in original basket assemblies owned by Larry Lagace (Ebay's "Vintage AR") for measurements and comparison to original woofers from the 70's, 80's, and Tonegen replacements of the late 80's/early 90's.

It will be very interesting to see the outcome of such a test, l will look forward to the result.

Brgds Klaus

[RoyC]

Hi Roy

Was there a similar correction of the X-over in the AR-5? As far as I remember, not. How come the difference?

The X-over in the AR-6 was changed big time, with the introduction of the new ceramic 8" woofer.



It will be very interesting to see the outcome of such a test, l will look forward to the result.

Brgds Klaus

Hi Klaus!

There was a change to a larger woofer crossover inductor from #11 (2.3 mh) to #10 (3.8 mh) in the AR-5. It isn't clear what motivated the changeover, but I don't think it was the later ceramic magnet woofer. The ceramic magnet woofer is more sensitive with more midrange output, and the 2ax woofer crossover is a simple series inductor. In the AR-5 it is cut off much sooner with a larger inductor, and the woofer has a large parallel cap to make the cut-off steeper. The ceramic magnet woofer would therefore be less likely to change the midrange response characteristics as much in the 5 than in the 2ax. AR-5's are not as available for study, and as more woofers are switched out and replaced, it is getting harder to figure out the sequence of the changes. For example, the earliest alnico AR-5 woofer was different than any of the woofers it later shared with the 2ax....

The AR-2ax midrange first had a 3 ohm resistor glued to the back when used with the later ceramic woofer. The resistor was later eliminated, and the 2ax mid's voice coil dcr was increased to 9 ohms from the original 6 ohms. No such changes were made to the AR-5 midrange driver, but some AR-5's have been found with mid leads crossed on the front of the cabinet (reversed polarity). Again, the reasons are not clear.

John at Msound seems fairly confident the cone, spider, and voice coil characteristics of his AR 12 inch woofer kit are close enough to original specs to be an acceptable alternative to an original woofer. I'll run some measurements, and post the results.

Roy

[xmas111]

Hi Roy,

As I mentioned I'm looking forward to your test results too.

The things I notice different with Johns kits and the original parts was as follows:

The voice coil former is about 3/16" longer.

The winding on the voice coil is about 1/16 to 3/32' (maybe 1/8") longer.

The cone itself seemed firmer, maybe the original has become a little more flexible through years of usage.

The polarity of the voice coil is opposite. (+ on the basket is now - and vise versa)

The wires from the cone to the terminal strip on the basket was much heavier duty.

Stupid me never though to measure the voice coil DC resistance.....

Don't know if any of the above should have any effect on the tonal qualities of the reconing kit, but those are things I noticed different.

Was going to post these pictures on my LST thread but didn't think anyone would care to see them.....

basket all clean up, spider mounted on the voice coil former, spider/voice coil assembly mounted in the basket...

John

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[ben76]

Hi,

Thanks everybody for the analysis and advice. I guess my father will follow Roy's suggestions :-)

I understand from Kent that the old 6-hole aluminum driver will not fit in a later AR2ax enclosure designed for the 4-hole steel driver. Are there electrical differences between the two models, or is it only mechanical, and some work with a router can fix that?

Is it advisable to do so if I find it easier to get the old aluminum drivers?

Ben