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AR11 Woofers With Rubber Surrounds and Unusual Tweeters


kcbluesman

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I am considering a pair of of AR-11 speakers. The owner replaced the foam surrounds with a set of rubber surrounds (which he says were provided by SimplySpeakers).

The work appears to have been done well, but I am concerned about the effect this change will have had on the performance of these woofers. To my ears, they seem to have less low-end output and impact. I assume that this might be an effect of the rubber surrounds being stiffer, less compliant than the originals? What would be the expected effects of the switch to rubber surrounds?

If I end up getting these speakers, I will probably replace the rubber surrounds. Is there a best source for surrounds that are closest in performance to the originals? Also, I noted that there is a layer of some sort of masonite or similar material between the frame and the surround. I assume that this is original?

As regards the tweeters...they appear to be original, and they sound good to me, but the dome is a cream/off-white color. In all of the AR-11 pics I've found, it is black. Are these perhaps early versions, or could they potentially be aftermarket replacements?

Thanks for any advice/assistance.

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I am considering a pair of of AR-11 speakers. The owner replaced the foam surrounds with a set of rubber surrounds (which he says were provided by SimplySpeakers).

The work appears to have been done well, but I am concerned about the effect this change will have had on the performance of these woofers. To my ears, they seem to have less low-end output and impact. I assume that this might be an effect of the rubber surrounds being stiffer, less compliant than the originals? What would be the expected effects of the switch to rubber surrounds?

If I end up getting these speakers, I will probably replace the rubber surrounds. Is there a best source for surrounds that are closest in performance to the originals? Also, I noted that there is a layer of some sort of masonite or similar material between the frame and the surround. I assume that this is original?

As regards the tweeters...they appear to be original, and they sound good to me, but the dome is a cream/off-white color. In all of the AR-11 pics I've found, it is black. Are these perhaps early versions, or could they potentially be aftermarket replacements?

Thanks for any advice/assistance.

I have never seen a modern rubber surround replacement compliant enough for an AR, or any other classic acoustic suspension speaker...nor have I seen one that would fit the AR 12 inch woofer. Are you sure it is not foam? Perhaps post a photo...

Due to non-standard dimensions there are only two foam replacement surrounds available for the AR 12 inch woofer, and these are very specific to the woofer. The best one is more compliant and has a slightly larger roll than the other. It is also very dark grey in color.

The early AR-11 and 10pi used a tan dome tweeter. The later tweeter had a dark dome and ferro fluid in the voice coil gap.

Roy

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Thanks Roy.

Yes, they are definitely rubber...I examined them yesterday. I will post a pic if/when I get them. The price (at $150) doesn't seem too bad....but I will need to replace the surrounds, refinish the cabinets, and put on new grill cloth (the current owner built some very nice wood frames to replace the original foam grills, but then did a pretty bad job of installing the cloth). He also put a felt "doughnut ring" around the perimeter of the tweeters. Not sure what his thinking was on this....he says that there was originally a similarly situated foam ring...I assume as some sort of dispersion management?

Can you recommend a source for the best foam surround?

Regarding the tweeters....do these early versions also have ferro fluid? And if not, are they basically similar to those in the AR-3a as regards power handling...or somewhere in-between the AR3a tweets and later AR11 tweets?

Thanks again.

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Thanks Roy.

Yes, they are definitely rubber...I examined them yesterday. I will post a pic if/when I get them. The price (at $150) doesn't seem too bad....but I will need to replace the surrounds, refinish the cabinets, and put on new grill cloth (the current owner built some very nice wood frames to replace the original foam grills, but then did a pretty bad job of installing the cloth). He also put a felt "doughnut ring" around the perimeter of the tweeters. Not sure what his thinking was on this....he says that there was originally a similarly situated foam ring...I assume as some sort of dispersion management?

Can you recommend a source for the best foam surround?

Regarding the tweeters....do these early versions also have ferro fluid? And if not, are they basically similar to those in the AR-3a as regards power handling...or somewhere in-between the AR3a tweets and later AR11 tweets?

Thanks again.

Msound (John Mcpeak) used to sell the appropriate foam, but I would ask him before ordering. msound@shentel.net.

"Vintage AR" definitely sells it. Last I checked, Simply Speakers does not sell the preferred version.

The earlier tweeters do not have ferro fluid, are favored by many, and are hard to come by. Not having old ferro fluid to potentially gum up the vc gap is probably an advantage these days.

There was originally foam on the faceplate of the AR-11 type tweeter, which has decomposed by now. Felt diffraction rings are often used to replace it.

Roy

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I appreciate the information, and it's good to get contact info for Msound....I could not track him down the last time I was looking for some AR3a surrounds.

The owner of the AR11s has let me "borrow" them for a few weeks so that I can get sense of how they sound with my gear and in my room....they won't be at their best, due to the surrounds, but it should give me a good sense of how they compare to the AR3a's and AR2a's....one set of which will have to give up its spot if I keep the AR11s.

Thanks again for all the good information.

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>The earlier tweeters do not have ferro fluid, are favored by many, and are hard to come by. Not having old ferro fluid to potentially gum up the vc gap is probably an advantage these days. There was originally foam on the faceplate of the AR-11 type tweeter, which has decomposed by now. Felt diffraction rings are often used to replace it.

>Roy

The first series of the AR-10/AR-11 tweeter was yellowish-orange in appearance, and it did not have Ferrofluid in the voice-coil gap or the adhesive-back foam piece on the front of it. It was plain. The performance of these tweeters should be unchanged over the years, as there is no urethane-foam suspension (as in the AR-3a tweeter), and there is no Ferrofluid that can dry out over time. This first series of the AR "Advanced Development Division" (a name taken after Lockheed Aircraft's original "Advanced Development Programs," later known as the "Skunk Works"), introduced in 1975, included the AR-10π, the AR-11 and the AR-MST. In 1977, these speakers were updated to the "B" series with new models added and changes to the logo and the addition of the Ferrofluid-cooled drivers. These tweeters were characterized by the black domes -- original versions were plain -- and around 1978 a foam pad was attached to the front of these tweeters.

The AR-11-type tweeter is a excellent driver with excellent overall performance. It is more efficient by several dB than the AR-3a hard-dome tweeter, but it does not have quite as good dispersion as the 3a tweeter. Therefore, the on-axis output of an AR-10 or AR-11 tweeter is greater in the high frequencies than the AR-3a, and the spectral balance is slightly brighter in the high frequencies, but the AR-3a has slightly more extended acoustic-power output due to its better dispersion.

—Tom Tyson

AR-3a-vs-AR-11_Tweeter_ARHPG_001.pdf

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It's interesting that the very early ADD 3/4" tweeters were not FF-cooled, because the lit is vague about the ADD tweeter characteristics. The 10 Pi lit says the new tweeter is more efficient and the improved efficiency can be used in the new system without putting the tweeter in increased thermal danger, brining the HF energy into line with the lower frequencies In other words, the 10 Pi lit says, "Yes, we know the Classics were dull, but these new ADDs aren't. The new tweeter is better, but we're not going to really explain exactly how."

Really? How can it not be in increased thermal danger if it's not FF-cooled? Ok, maybe just by virtue of its new contruction techniques or some other unspecified miraculous goodness.

In any event, the ADDs--especially the 10 Pi, 11 and 12--were really terrific speakers and a set in good operating condition is a nice find. I owned 11s and I loved them.

Steve F.

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It's interesting that the very early ADD 3/4" tweeters were not FF-cooled, because the lit is vague about the ADD tweeter characteristics. The 10 Pi lit says the new tweeter is more efficient and the improved efficiency can be used in the new system without putting the tweeter in increased thermal danger, brining the HF energy into line with the lower frequencies In other words, the 10 Pi lit says, "Yes, we know the Classics were dull, but these new ADDs aren't. The new tweeter is better, but we're not going to really explain exactly how."

Really? How can it not be in increased thermal danger if it's not FF-cooled? Ok, maybe just by virtue of its new contruction techniques or some other unspecified miraculous goodness.

In any event, the ADDs--especially the 10 Pi, 11 and 12--were really terrific speakers and a set in good operating condition is a nice find. I owned 11s and I loved them.

Steve F.

Steve,

I would be guessing more efficient translated into less heat generated at the same SPL -- not too many variables there, dome, suspension, coil and magnet -- ferrofluid also if it is present.

Still interested in the compliance of the butyl rubber surrounds here. The ADS L-980's rubber is pretty compliant but maybe the AR design called for a longer throw. I doubt anyone is interested in testing the differences at this point beyond a simple A/B comparison.

I seem to remember you had some issues with the baffle arrangement on these.

Roger

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Steve,

I would be guessing more efficient translated into less heat generated at the same SPL -- not too many variables there, dome, suspension, coil and magnet -- ferrofluid also if it is present.

Still interested in the compliance of the butyl rubber surrounds here. The ADS L-980's rubber is pretty compliant but maybe the AR design called for a longer throw. I doubt anyone is interested in testing the differences at this point beyond a simple A/B comparison.

Roger

The unfiltered response differences between the AR-3a type tweeter and the AR-11 type tweeter are essentially the same as they are between the 3a tweeter and any modern dome tweeter. It has more to do with the very unique construction of the 3a type tweeter than anything else. AR manufactured the 3a type tweeter to have a very limited excursion, which mechanically, naturally, and relatively steeply, rolled off the response into lower frequencies beginning at very high frequencies, with a simple series capacitor crossover. This approach also affected the overall sensitivity of the 3a type tweeter....and pushing it hard would often result in burning it out.

The later AR-11 type tweeter, like most modern dome tweeters, has a much more compliant suspension and much greater excursion. In spite of a similar size magnet to the 3a tweeter, the unfiltered overall output is significantly greater than the 3a tweeter. This "modern" construction, however, results in increased output into lower frequencies...so in order to cross the AR-11 type tweeter over at around the same (quite high) frequency as the AR-3a, a parallel inductor was used in the AR-11/10pi (and later models) to more steeply roll it off into lower frequencies.

Regardless of the use of ferro fluid, the unfiltered mechnical characterisitics of these tweeters must be taken into consideration. It is often overlooked, especially when trying to find suitable modern replacement drivers, and in many crossover discussions.

Roger...There were some great woofers with rubber surrounds used in acoustic suspension speakers, but they were MUCH more compliant than today's rubber replacement surrounds. Unfortunately, all of the replacement rubber surrounds I have seen being sold today are too thick and not compliant enough (by alot) to use with old AR speakers. They are meant for ported, typically automotive, speakers and "subwoofers". It would ruin a perfectly good AR woofer to glue one of these things to it. Otoh, I have adapted some excellent old Avid woofers with very compliant rubber surrounds to AR speakers in the past. (AR was foam crazy on many levels, imo...but that is a discussion for another time. :))

Roy

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...

Regardless of the use of ferro fluid, the unfiltered mechnical characterisitics of these tweeters must be taken into consideration. It is often overlooked, especially when trying to find suitable modern replacement drivers, and in many crossover discussions.

Roger...There were some great woofers with rubber surrounds used in acoustic suspension speakers, but they were MUCH more compliant than today's rubber replacement surrounds. Unfortunately, all of the replacement rubber surrounds I have seen being sold today are too thick and not compliant enough (by alot) to use with old AR speakers. ...

Roy

Thanks, Roy, that explains quite a bit.

Roger

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  • 2 years later...

Quite likely it is a result of forum software upgrades. I'm guessing the file is actually somewhere
on the forum but not where the link points. That's a shame; I've seen 8 and 10 year old threads
that were trashed, but this is from 2014 and suggests institutional memory here has advanced
Alzheimer's.

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  • 1 year later...

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