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Compliance of replacement foam surrounds


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#1 Rich W

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Posted 07 September 2006 - 04:44 PM

Just got a refoam kit consisting of four 8" surrounds from Parts Express.

One set has the correct angled attaches but are thick. The second set have flat attaches but are substantially thinner and more supple - they also have a lower profile (the roll doesn't stand out as much when viewed edge on). So the dilemma is the same as described by Carl - you can have your thin surround, but you'll have a heck of a time attaching them. Or choose a geometrically correct thicker surround with a corresponding higher fs.

Still waiting on a set from RSSOUND. Maybe we'll get lucky. If they are not angled and thin, I'm taking a stab at refoaming using the flat attach models from Parts Express.

Best to all,

Rich W

#2 RoyC

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Posted 07 September 2006 - 12:21 AM

Attached is a photo of the AR-3a surrounds described by Minh. The left one is the newer, preferred style. The right one is the older type.

Roy

http://www.classicsp..._files/1561.jpg

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#3 mluong303

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Posted 06 September 2006 - 04:39 AM

Hi, Robert_S,

Thank you for the good words. Actually, I don¡¯t do refoam woofers for a living or even doing it for part time. I first encountered AR-3a speakers back in 1972 and since then just crazy about AR and did buy and collect huge amount of AR speakers over the past two decades and did repaired and restored most of them myself. I do enjoy helping out the people I meet who feel their beloved AR, Allison or Cello speakers are all they care for and wish they could hold onto them for as long as they live! These are the kind of crazy people I can relate to¡­ I am getting busier in life and have many new things to deal with so I no longer do much of the refoam job anymore! I do have few pairs of the wide half roll AR 11¡±foam surrounds and the correct type of Allison 10¡± woofer surrounds on hands. Drop me a line for price and shipping cost if you need them.

Minh Luong
mluong303@aol.com

#4 Rich W

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Posted 05 September 2006 - 02:13 PM

Thanks, Pete.

Given their low cost, I'm going to give the RSSOUND surrounds a try.

Best Regards,

Rich W

#5 Rich W

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Posted 05 September 2006 - 02:10 PM

>The 8" foam-compliance issue (if you perceive this to be
>an issue), is not limited to the AR18 series; any of the (pre
>'84ish era in discussion here) AR loudspeakers that utilize
>8" drivers for the reproduction of the lowest of
>frequencies are potentially effected by the replacement of an
>original component, with something that (so obviously!)
>differs in its operating characteristics -- not everyone
>shares these concerns (witness the ready acceptance of the
>freely available 8" clearly-way-too-stiff foam) -- there
>is an alternative out there, somewhere!? . . . .
>
An interesting point - how many of those refoamed 8" AR drivers are really performing up to spec? Aside from obvious increase in fs, how is the lack of surround compliance affecting low frequency response in real world listening applications? I'd really like to know how much a bass rolloff exists, and what other anomolies exist in the mid-bass and midrange.

I plan on running some 1/3 band octave pink noise tests on enclosed stiff-foam and compliant-foam AR 200037 8" drivers using an AKG C414 TLII microphone (flat to below 20 hz) to see what the real differences are. I'll report my findings on this forum.

Many thanks to Carl for researching options for us AR18 fans.

In the meantime, I will join you Robert in the quest for a compliant 8" surround, and report any news on this forum.

Best Regards,

Rich W

#6 Pete B

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Posted 05 September 2006 - 04:14 AM

I've mentioned RSSOUND here as having very compliant surrounds. I've only done 2 AR 12" and 2 Advents but both had very low Fs. Here's the data for one AR 12", measured Fs = 15.3 Hz and it was a 200003 woofer:
http://www.classicsp...3&topic_id=7172

I've done about 6 other drivers with foam from one of the big suppliers and found the foam to generally be stiffer. Don't know
if there's any difference in life expectancy for these foams.

Also, never know if his or any other supplier might change.

#7 Robert_S

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Posted 05 September 2006 - 03:18 AM

> I think you AR18 guys are out of luck.

The 8" foam-compliance issue (if you perceive this to be an issue), is not limited to the AR18 series; any of the (pre '84ish era in discussion here) AR loudspeakers that utilize 8" drivers for the reproduction of the lowest of frequencies are potentially effected by the replacement of an original component, with something that (so obviously!) differs in its operating characteristics -- not everyone shares these concerns (witness the ready acceptance of the freely available 8" clearly-way-too-stiff foam) -- there is an alternative out there, somewhere!? . . . .

> what about all of us AR-3a woofer guys

Not my speciality, but the AR-3a surrounds seem easier to source, I re-foamed my AR-3a Improved last year and was impressed by the apparent close match.

Minh Luong was most informative on the subject (as are many threads on this site):

> There are only two kinds of 11" foam surrounds. The old type sold by Simply Speakers and other venders who still have a small left over from their old inventory or the New and more correct size sold by Larry of Vintage AR or Part Express. That is all your option for the 11" foam surrounds. I never keep track on where I bought things from since if I got something that is not up to my standard then I just throw them out. I do think Larry has the right 11" and 8" foam surround for AR woofers. Just ask him if they are not up to your standard will he refund the surrounds cost after you send him back the products.

> Regards,
> Minh

The 8" surround-foam that Larry had did not meet my requirements (though his 12" seems good), he is informed and friendly to trade with, a useful (re)source.

The better/newer type 12" foam surrounds are identifiable by the fine (moulding?) lines, as visible in Carl's pictures below, and in those supplied by Larry.

Rick at RS Sound has also proven to be a good source, with by far the lowest prices (for international shipment).

There appears to be a third type of AR 12" driver surround-foam used by European repair professionals, which is black, very supple and has a granular look to the surface.

Now back to the 8" driver surround-foam thread, and Rich's original:

> Question is, assuming surround thickness is significant factor in a restored woofers performance, where can I get the most compliant (thinnest) surrounds?

The question remains open!

Robert_S

#8 Carlspeak

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Posted 05 September 2006 - 02:35 AM

Well, I went and screwed up again. I uploaded the wrong report. It's the same "Williams" test I posted earlier.

HERE IS THE CORRECT ONE!!!



Remember, it's all about the music

Carl
Carl's Custom Loudspeakers

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IT'S ALL ABOUT THE MUSIC!

Carl
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#9 Carlspeak

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Posted 05 September 2006 - 02:29 AM

Sorry guys. I didn't upload the AR3a test report properly. I'm still getting used to Mark's system.
Here it is!



Remember, it's all about the music

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Carl's Custom Loudspeakers

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IT'S ALL ABOUT THE MUSIC!

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#10 Carlspeak

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Posted 05 September 2006 - 02:25 AM

>Carl, what about all of us AR-3a woofer guys in need of
>surrounds? I’d need a few high compliance, wider-roll
>surrounds myself! I have a few ne ones from different supplies
>sitting here wating for me to use the, but they;’re all
>different. Only one from P.E. almost looked like it was from
>1972, I ordered another ASAP and it was different. Now I’m
>hesitant to begin work until I find a near perfect match as
>I’ve got 8 re-foams to do immediately with 7 more to follow.
>Frank Marsi
>

I have AR3a surrounds that have worked very well for my customers whom I've done refoam jobs. Are they exactly what you want? - don't know.
Embeddand and attached is a picture of a recent AR3a refoam along with a separate test report. The report shows the free air resonance is slightly less than 18 Hz. I'd say that's pretty compliant. This should drop a Hz or two after break in. The pic also shows a pieced together gasket (due to non-standard 11" size) I add to help keep the surround in place.
I normally don't sell surrounds or surround kits. There are enough guys on e-bay and elsewhere who do that. My business is to actually do the refoam job. However, as a favor to the ardent AR fans who post here I'll make this exception.
I'll sell them for $8.95 ea. plus shipping. Anyone interested?

Remember, it's all about the music

Carl
Carl's Custom Loudspeakers

http://www.classicsp..._files/1550.jpg


http://www.classicsp..._files/1551.jpg
IT'S ALL ABOUT THE MUSIC!

Carl
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#11 Carlspeak

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Posted 05 September 2006 - 01:44 AM

>Hi Carl,
>
>The attaches on the AR18 woofer are angled, same angle as the
>woofer cone.
>
>Many thanks for researching this for us!
>
>Best Regards,
>
>Rich

I also have another surround with about the same dimensions that is an angle attach model. However, It is a bit thicker and feels a bit stiffer.
I think you AR18 guys are out of luck.

Remember, it's all about the music

Carl
Carl's Custom Loudspeakers
IT'S ALL ABOUT THE MUSIC!

Carl
Carl's Custom Loudspeakers

#12 Robert_S

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Posted 05 September 2006 - 01:41 AM

Hello Carl,

> The surrounds I have are flat attach. Trying to make them attach at an angle is difficult but doable.
> Edge inner = 138
> Roll inner = 147
> Roll outer = 181
> Edge outer = 194

It can be done, as I'm sure you know, by exploiting the property of foam-fatigue; by pre-stressing the inner edge and/or by a regular series of very small incisions, but obviously this approach is a last resort.

Nevertheless, I'd certainly be interested in seeing these for comparison/evaluation.

(When pre-stressing, the surrounds expand by a few mills, so the fact that the critical inner-roll measurement is slightly too small could be advantageous.)

I can contact you through your web site, for cost and shipping details . . . .

Thanks again for your time and concern.

Robert_S

#13 frankmarsi

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Posted 05 September 2006 - 01:36 AM

Carl, what about all of us AR-3a woofer guys in need of surrounds? I’d need a few high compliance, wider-roll surrounds myself! I have a few ne ones from different supplies sitting here wating for me to use the, but they;’re all different. Only one from P.E. almost looked like it was from 1972, I ordered another ASAP and it was different. Now I’m hesitant to begin work until I find a near perfect match as I’ve got 8 re-foams to do immediately with 7 more to follow.
Frank Marsi

#14 Rich W

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Posted 05 September 2006 - 01:20 AM

Hi Carl,

The attaches on the AR18 woofer are angled, same angle as the woofer cone.

Many thanks for researching this for us!

Best Regards,

Rich

#15 Carlspeak

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Posted 05 September 2006 - 12:21 AM

>> What are the exact dimensions of the AR18 surround? ID,
>OD and roll width?
>
>Having just measured eight of the AR18s original woofer
>surrounds (#200037), the (averaged) dimensions, in
>millimeters, are thus:
>
>Edge Inner: 141
>Roll Inner: 149
>Roll Outer: 177
>Edge Outer: 188
>
>Roll Width: 14
>
>To the best of my knowledge, the 8" "Universal"
>woofer (#200001) also shares the same foam-surround
>dimensions.
>
>(Later Tonegen drivers can be seen with a narrower inner and
>wider outer, plus a slightly wider roll of 15mm.)
>
>Thanks for any help you may be able to offer . . . it would be
>wonderful to find the real thing.
>
>Robert_S

I may have something that will work.
Edge inner = 138
Roll inner = 147
Roll outer = 181
Edge outer = 194
These measurements were taken on raw surround which, obviously, is quite flexible and 'squirmy'. This surround is thin. The tad wider roll will help compliance as well.
The last important detail is the attach. Does the AR18 have a flat attach or angle attach? In other words, is the outer edge of the cone flat for a bit or does it angle up all the way to the outer edge?
The surrounds I have are flat attach. Trying to make them attach at an angle is difficult but doable.

Remember, it's all about the music

Carl
Carl's Custom Loudspeakers
IT'S ALL ABOUT THE MUSIC!

Carl
Carl's Custom Loudspeakers

#16 Robert_S

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Posted 04 September 2006 - 09:11 PM

> What are the exact dimensions of the AR18 surround? ID, OD and roll width?

Having just measured eight of the AR18s original woofer surrounds (#200037), the (averaged) dimensions, in millimeters, are thus:

Edge Inner: 141
Roll Inner: 149
Roll Outer: 177
Edge Outer: 188

Roll Width: 14

To the best of my knowledge, the 8" "Universal" woofer (#200001) also shares the same foam-surround dimensions.

(Later Tonegen drivers can be seen with a narrower inner and wider outer, plus a slightly wider roll of 15mm.)

Thanks for any help you may be able to offer . . . it would be wonderful to find the real thing.

Robert_S

#17 Carlspeak

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Posted 04 September 2006 - 05:56 PM

>Hello fellow AR enthusiasts,
>
>To date, I've restored several pairs of "Truth in
>Listening" series AR-17 and AR-18 speakers, which of
>course in every case includes the task of replacing the
>deteriorated foam surrounds.
>
>I now have the opportunity (or good fortune at $5 a pair!) to
>restore yet another pair of AR-18's. What I've noticed,
>however, is that the thickness of the replacement surrounds
>can vary from supplier to supplier. The effect is most
>evident when you give the installed woofer the
>"push" test to check for a good cabinet seal. The
>thinner surrounds are obviously more compliant and allow the
>woofer much more throw, which in my mind translates to a lower
>free air resonant frequency - probably closer to what the
>orginal designers had intended. Said another way, I find that
>the thicker surrounds seem to be restricting the movement of
>the woofer, where as with the thinner surrounds, the cushion
>of air in the cabinet seems to be doing more of its intended
>job of restoring the woofer to it resting position.
>
>From a subjective standpoint, a feel that the thicker surround
>has resulted a "woolier" sound, with an increase in
>output in the 80 to 120 hz region.
>
>Question is, assuming surround thickness is significant factor
>in a restored woofers performance, where can I get the most
>compliant (thinnest) surrounds?


What are the exact dimensions of the AR18 surround? ID, OD and roll width?
I have access to a commercial, wholesale supplier where I get my surrounds for my business and maybe, can get something that's thin and meets your needs and the apparent needs of others who have posted here.
Another option you may want to consider is having a professtional like myself do the refoam. When you contact them, ask if they provide a test report with the finished job. If they are in the refoaming/reconing buiness they SHOULD have woofer testing apparatus.
As a courtesey to my customers, I provide a report with all my woofer jobs. As an example, attached is a scan of an AR-9 10" refoam job I did for a customer earlier this year.


Remember, it's all about the music

Carl
Carl's Custom Loudspeakers

http://www.classicsp..._files/1546.jpg
IT'S ALL ABOUT THE MUSIC!

Carl
Carl's Custom Loudspeakers

#18 Rich W

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Posted 04 September 2006 - 05:56 PM

Got the posts mixed up! My response was directed you Robert.

Rich W

#19 Rich W

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Posted 04 September 2006 - 05:54 PM

Hi Stephen,

FYI, the first set of surrounds I ordered and installed two years back were very thin and compliant. I subsequently ordered another set from the same supplier and they were excessively stiff. I'm taking a chance on a set of Partsexpress surrounds and will report back what I've found.

It's great to hear that the AR18's have such a following among the Brits. I've gone on record in this forum stating that they sound superior to the highly venerated Larger Advent and KLH 5, especially in the critical upper midrange where I feel the others are somewhat harsh. Of course, they'll never reproduce that lower octave of bass, but I have a powered subwoofer for that purpose. In addition, there are very few dome designs that can match the smoothness of that 1 1/4" pressure cone tweeter.

Best Regards,

Rich W

#20 Robert_S

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Posted 04 September 2006 - 05:25 PM

For sometime now, I've been on an mini-epic search to find the correct *supple and thin* foam for the AR 8" woofer (AR Part 200037). Someone somewhere makes it; one company in london use it when re-foaming AR-18's, but alas they will not sell the surrounds separately (due to a lack of confidence in the DIY'ers ability to do a good job of the repair).

Incidentally, an earlier 8" woofer (AR Part 10708-1), as used in the AR-7, also presents a challenge to the conciencous re-foamer, as it had a smaller-diameter half-round surround. I've found a very close match (though with a flat, rather than the correct angled edge, but this can be gently re-worked/stretched and made 'correct'), available from an Australian supplier (at a cost!).

A section of previous dialogue on the (#200037) subject:

-------------------- -------------------- --------------------

Robert wrote:

Hello Stephen,

I read with some interest your post concerning the difficulty in finding the correct foam for use on the AR-18s woofer (200037).

Did you have any success in locating a source for the correct foam surrounds? I have purchased foam from around ten sources, and it all seems to be incorrect, as in not compliant enough. (Also, the half roll is often too narrow, and this may have a bearing on the woofer excursion range?)

It's been a while since you posted your message (quoted below), but like your self, I do not wish to compromise the sound by the use of incorrect replacement parts, hence my ongoing search . . . .

Any information you are able to furnish me with would be most appreciated.

Kind regards,

Robert


Quote:

#6. "RE: broken ar18s"

Careful!

Simply Speaker foam is WAY TOO STIFF for this series of 8" woofer. Free air resonance frequency measures at over 40Hz with a "restored" woofer.

NEWFOAM is WAY TOO PERMEABLE to use...any "Acoustic Seal" is destroyed.

I have one original 2000037 woofer with intact and pliable original foam. It is VERY thin and non permeable. Free air resonance is about 29Hz.

I am beginning to wonder if the home diyer CAN restore these woofers to  anywhere near original spec. As they were used with no crossover components the high end frequency response is also critical, and this is strongly dependent on the surround. Was this the function of the thick ring of glue(?)at the edge of the half roll? Is there anywhere  where we can get hold of the correct type of foam?

By the way...a view from Britain. AR, through to the mid-eighties, were one of the very few non-British loudspeaker manufacturers which could compete with the homegrown companies- KEF, Rogers, Mission etc. The cabinets were built over here but the drivers were imported from the USA. The UK speakers looked different in small ways. I remember finding any excuse to babysit at a neighbours house so as to listen to his his hi-fi- the speakers were largish AR from the "classic" series. Not 3's- too small- but way larger than the 7 etc. I'd love to know what they were now. They sounded fantastic. As soon as I could afford a "proper" hi-fi I got the 18s which were huge sellers over here. They, again, sounded fantastic and suited our generally smaller rooms beautifully. I have never heard any speakers as good as these 2 pairs. I have heard more "impressive", perhaps more detailed etc. speakers, but none have  ever have had the emotional impact and, perhaps paradoxically, the fun factor. AR 18s still have a large following in the UK and will sell for about £100 on ebay, even with deteriorating surrounds. Other AR speakers of any vintage do not achieve anything like this price. AR UK reintroduced the 18s as the Redbox 2 in the late eighties.

-------------------- -------------------- --------------------

Stephen wrote:

No! I've given up. I am convinced there is more to this than putting a new foam on. For example, at the perimeter of the cone before the half roll is always a ring of glue-like material. This would have damped the  cone. What was it? I have no doubt that it was a vital part of the construction of the woofer and would have shaped the response at the top end. Details like this are not attended to on any of the sites I visited or any of the kits I bought. I still have four of these woofers and wait hopefully for the day when someone comes up with the "perfect" kit. I am not going to ruin any more. If you believe, like me, that the AR18 was a truly amazing and FUN speaker, let's hope that someone does.

-------------------- -------------------- --------------------


Hopefully this thread will help us find the elusive soft & supple 8" foam!

Robert_S




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