AR Tweeter Repairs

[Tekker]

There's a NJ user on Ebay named "chris1this1" who can repair your AR3a tweeters, among others, for $40 apiece. That includes return shipping. I no longer see his ad there, but I'm assuming you can contact him there through his ebay name.

I sent him my 2 tweeters with blown voice coils and one dimpled cone and they came back yesterday, with nice round domes. They ohmed out OK, so I patched them into my speaker through the front terminals. Had to turn down the pot on the back. Don't ever remember getting that kind of volume before. Nice and clear so far. I'm regretting not changing out the caps now as I'm hearing frequencies I don't believe belong on them when I crank up the volume a little. I won't permanently install them until I at least get some new 6uF caps. I recently bought and installed some used original AR3a tweeters which sound good, but at very low volume. Does anyone know why this happens? I may pack them off the NJ when the time comes.

Anyway I highly recommend this guy's work. If you've got any old AR tweeters laying around you don't want, don't throw them away. I'll send you a postage paid, self addressed box for them.

Bill

[genek]

I recently bought and installed some used original AR3a tweeters which sound good, but at very low volume. Does anyone know why this happens?

That's the way they're designed to work.

[JKent]

FWIW Vintage AR (well known here) is also repairing AR tweeters

Kent

[Tekker]

That's the way they're designed to work.

I don't think so. I've read here numerous times that these speakers' ability to move air degrades over time, and I don't believe planned obsolescence was a design philosophy at that place and time. I have one I bought off of Ebay that ohms out OK and produces sound but would make a poor driver for a headphone. I just don't how or why they degrade. Maybe suspension material stiffens? Maybe voice coil bobbin warps or frays? Maybe corrosion? I don't know.

[Tekker]

FWIW Vintage AR (well known here) is also repairing AR tweeters

Kent

Last I heard Vintage AR was not rewinding voice coils. Has that changed?

[genek]

I don't think so. I've read here numerous times that these speakers' ability to move air degrades over time, and I don't believe planned obsolescence was a design philosophy at that place and time. I have one I bought off of Ebay that ohms out OK and produces sound but would make a poor driver for a headphone. I just don't how or why they degrade. Maybe suspension material stiffens? Maybe voice coil bobbin warps or frays? Maybe corrosion? I don't know.

Recent measurements of old AR drivers have strongly suggested that this is probably an incorrect assumption made by listeners who aren't prepared for the way these drivers sound. Even tweeters that have been confirmed by measurement to perform to the same levels as when new usually cannot be heard in normal operation without resorting to tools like stethoscopes or cardboard toilet paper tubes. You don't get strong output from these drivers because real music doesn't have much strong signal in the frequency ranges they're designed to work in, and most people who think there should be more are just accustomed to listening to speakers whose highs have been boosted to artificially high levels.

Most AR tweeters that check out ok for DCR are probably working normally, until their owners bypass the pots or otherwise mod the speakers to boost treble to desired levels that exceed the original specs. This causes the tweeters to produce more output for a time, then to produce no output at all and to not check out ok for DCR anymore, at which point the owners conclude that their performance degraded and then they died, when they were probably working just fine until they were killed off by being overloaded.

If you're convinced you want and should be getting more HF output from your ARs even though their tweeters measure ok for DCR, my advice would be to order up a pair of the HiVi replacement tweeters Roy has worked out and that Larry (Vintage AR) is selling and save your originals for some future owner to reinstall. Or just leave them be and turn up your treble control as AR originally advised. Rewinding tweeter voice coils or otherwise rebuilding them may produce tweeters with higher output that you like better, but whether that's "repairing" them to what they were designed to sound like or just modding them into something different from what they were designed to be is another matter.

[Tekker]

There's a NJ user on Ebay named "chris1this1" who can repair your AR3a tweeters, among others, for $40 apiece. That includes return shipping. I no longer see his ad there, but I'm assuming you can contact him there through his ebay name.

I sent him my 2 tweeters with blown voice coils and one dimpled cone and they came back yesterday, with nice round domes. They ohmed out OK, so I patched them into my speaker through the front terminals. Had to turn down the pot on the back. Don't ever remember getting that kind of volume before. Nice and clear so far. I'm regretting not changing out the caps now as I'm hearing frequencies I don't believe belong on them when I crank up the volume a little. I won't permanently install them until I at least get some new 6uF caps. I recently bought and installed some used original AR3a tweeters which sound good, but at very low volume. Does anyone know why this happens? I may pack them off the NJ when the time comes.

Anyway I highly recommend this guy's work. If you've got any old AR tweeters laying around you don't want, don't throw them away. I'll send you a postage paid, self addressed box for them.

Bill

Received an email from Chris the voice coil fixer. He is taking a break from Ebay for a while, but advised me I could provide his personal email address to anyone in need of his assistance: reverbdmit@aol.com

Bill

[speaker dave]

Most AR tweeters that check out ok for DCR are probably working normally, until their owners bypass the pots or otherwise mod the speakers to boost treble to desired levels that exceed the original specs.

...and turn up your treble control as AR originally advised.

Why is turning up the (amplifier) treble control okay but bypassing the pots dangerous practice? It would seem that a bypassed pot and a pot set to max would send essentially the same level to the tweeter (slight shunt loading to the network aside). Amplifier treble boost could be as much as 12dB or 4 times the voltage.

I don't believe the tweeter sensitivity varies over time but I thought suspension stiffening and resonance increase was a common problem? The last pair of AR3 I worked on had a distinctive midrange/low treble absense from the mid suspension stiffening and unit resonance rising dramatically.

David

[genek]

Why is turning up the (amplifier) treble control okay but bypassing the pots dangerous practice? It would seem that a bypassed pot and a pot set to max would send essentially the same level to the tweeter (slight shunt loading to the network aside). Amplifier treble boost could be as much as 12dB or 4 times the voltage.

I don't believe the tweeter sensitivity varies over time but I thought suspension stiffening and resonance increase was a common problem? The last pair of AR3 I worked on had a distinctive midrange/low treble absense from the mid suspension stiffening and unit resonance rising dramatically.

My wild guess on that would be the different turnover points and slopes of the speaker crossovers and treble controls, but a guess is all it would be. Maybe it doesn't make a difference and it's just coincidence that I've been able to run AR tweeters at all tone and volume settings that my ears can stand for years and other people have bypassed tweeter pots and had tweeters die on them within months.

I'm sure that the materials in drivers do change over time, even the ones I have that are still working fine to my ears, and maybe the sound of my tweeters has changed so slowly over the years that I just haven't noticed, but I'd still put my money on most tweeters suffering sudden death rather than audibly fading away.

[Tekker]

My wild guess on that would be the different turnover points and slopes of the speaker crossovers and treble controls, but a guess is all it would be. Maybe it doesn't make a difference and it's just coincidence that I've been able to run AR tweeters at all tone and volume settings that my ears can stand for years and other people have bypassed tweeter pots and had tweeters die on them within months.

I'm sure that the materials in drivers do change over time, even the ones I have that are still working fine to my ears, and maybe the sound of my tweeters has changed so slowly over the years that I just haven't noticed, but I'd still put my money on most tweeters suffering sudden death rather than audibly fading away.

Well I bought my AR3a's back in 72. They were already a few years old and the pots were very scratch and occasionally intermittent. At that time I could definately distinguish the tweeter by putting my head close to the speaker grill over the tweeter. After several years they faded, and I had to remove the grill to be sure they were still functioning. Some time after that the pots got worse and I jumped out both pots putting a full 16 ohms across the mid and hi range speakers. Other than the intermittent problem, there was no improvement, but I could still definitely hear the speakers without any toilet paper devices. So it went until some time later when I drove them with a sheap home theatre amp that apparently clipped and took out the tweeter voice coils. Foolishness on my part. I bought a used tweeter on Ebay. Ohmed out at 2.7 ohms, but I had to hold it against my ear and wait for a cymbal crash to hear it at all. I had it patched in with a pair of 18" jumper leads, so I could hold it away from the other drivers. Bought another pair of used speakers which were somewhat better but still quieter than my originals. I just had the originals repaired with new voice coils and they are just a bit louder than they sounded back in '72, as I remember it. Maybe a tad louder as my ears have aged along with everything else.

[speaker dave]

The problem is that with the early three way models the tweeter level is quite low by design. Even when working well it is a little difficult to detect proper tweeter operation.

By AR's published curves an AR3a tweeter is a full 10dB below the mean woofer level. My curves of an AR2ax (with good replacement tweeters from about 1980) show about the same level, 10dB below the woofer with the pot at max. Both of these systems have a wide range mid and the tweeter is more a super tweeter to fill in and broaden directivity above 5kHz.

Luckily, there are a lot of high resolution curves of the individual drivers in AR's lit. We should be able to measure contemporary samples and see if they still compare to original measurements, either in relative sensitivity or bandwidth.

Regarding the drivers aging, here are the mechanisms I am aware of:

Alnico magnets can be demagnitized by a sufficient kick to the voice coil, but this is usually only a woofer phenomenon. I can't imagine a tweeter surviving such an electrical jolt. Assuming the coil is intact (a DCR test will suffice) and coil centering hasn't changed then sensitivity is determined by mass. Can the materials abosorb enough moisture to impact their mass? Not likely. Beyond this I can't think of a mechanism for tweeter sensitivty to fade.

Glue bonds can weaken but this would either cause noises or distinctly change the high end. Ferrofluid drivers (in later models) can "sludge up" over time where the metal particles compact and effective suspension stiffness is driven up. This is at least partly reversible with some low frequency excercising.

My biggest concern would be with the dome suspensions going solid. The three centering dots (I understand) can stiffen and that would raise resonance considerably. If the tweeter turns on at 10kHz rather than the intended 5kHz, I would guess that would make the tweeter very hard to hear.

Can anybody measure some "aged" or low sensitivity drivers?

David

[genek]

Can anybody measure some "aged" or low sensitivity drivers?

Can't help you there. The original tweeters of my 1975 2ax's are still going strong. The tweeters of the 3a's I restored last year had both suffered instant death, and the replacement units I installed are also producing full output as far as I can hear. I put my old garage-sale Microstatics on top of both, mostly because my wife likes the way they look, and they actually produce less HF output than the AR domes.

[Tekker]

Turns out my aforementioned ebay dud tweeter is not revelant here. That particular speaker should have the 3 red suspension dabs, but it doesn't. It appears somebody has been unsuccessfully attempting surgery on it.

Bill

[JKent]

Bill, I am not fortunate enough to have a pair of 3a's but if I were in your position I would definitely use RoyC's HiVi tweeter replacement. Roy has researched the replacement tweeter issue extensively and came up with this replacement after much experimentation. See this thread:

http://www.classicspeakerpages.net/IP.Boar...hl=hivi+tweeter

Interesting reading. I think Roy addressed the problem with your tweeters when he wrote:

After a dozen or so dissections, I am convinced that many, if not most, of the original AR 3/4" tweeters out there do not sound the same as they once did, and today are inconsistent at best. Replacing them with used originals can be an expensive crapshoot...so here we are. Consequently, the problem remains that, out of necessity, we may be talking "mod" as much as we are "restoration".

The HiVi is a good modern tweeter that will not have the aging suspension of the original AR. They're pretty inexpensive. Why not give 'em a try? Be sure to add the inductor Roy describes.

Good luck.

Kent

[Tekker]

Bill, I am not fortunate enough to have a pair of 3a's but if I were in your position I would definitely use RoyC's HiVi tweeter replacement. Roy has researched the replacement tweeter issue extensively and came up with this replacement after much experimentation. See this thread:

http://www.classicspeakerpages.net/IP.Boar...hl=hivi+tweeter

Interesting reading. I think Roy addressed the problem with your tweeters when he wrote:

After a dozen or so dissections, I am convinced that many, if not most, of the original AR 3/4" tweeters out there do not sound the same as they once did, and today are inconsistent at best. Replacing them with used originals can be an expensive crapshoot...so here we are. Consequently, the problem remains that, out of necessity, we may be talking "mod" as much as we are "restoration".

The HiVi is a good modern tweeter that will not have the aging suspension of the original AR. They're pretty inexpensive. Why not give 'em a try? Be sure to add the inductor Roy describes.

Good luck.

Kent

Thanks Kent,

I've already read that thread, but thanks for the link. It deserves another read. Roy has already been very helpful with advice and sources. I was just about to score those hi-vi speakers as per his advice when I found a fairly good used set of original AR3a speakers which I'm currently using. I was lucky enough to roll craps on only that one dud. I also got my originals repaired, but won't mount them until I take another look at my crossover caps.

Bill

[Zilch]

Can anybody measure some "aged" or low sensitivity drivers?

Yes.

I have promised to look at them more comprehensively when I do the Hi-Vi swap.

I may have more, also; I'll check the AR4x tweeter inventory at the same time....

[lakecat]

Anyone know of this? He states he has done it in the past.  

http://www.ebay.com/itm/Ar-Lst-Lst-2-Ar3-Ar2Ax-Tweeter-Repair-Service-For-Acoustic-Research-Tweeters-/191998143690?hash=item2cb3fb2cca:g:1SYAAOSw8w1YA-O2

[owlsplace]

Interesting ... someone needs to dive in and report back.

[Chris1this1]

 Ladies and gentlemen, this is Christian (Chris1this1),  I have  re-established my 3/4" tweeter  repair operation.  This time around, I am able to precisely match the winding techniques used originally by AR. I am very satisfied with the run I did for my AR LST-2, needing all 6 tweeters rebuilt.  I have done comparisons with fully operational original tweeters and the sound is indistinguishable between the original and the rebuilt.  Unfortunately, I had to raise the price a bit due to the amount of time it takes on each tweeter but I feel you are guaranteed to get a great sounding tweeter  with the proper output still for a lot less than well preserved  examples of original tweeters.  Plus, there's no guilt when driving these rebuilt tweeters hard, since i've always felt like I didn't want to damage original ones so always took it easy on them.  I'm only listing two at a time, to make it feel like less of a job but more of an expression for my passion of these vintage acoustic research speakers.  Feel free to check out my eBay auction for two available rebuilding services. Cheers!

[owlsplace]

2 hours ago, Chris1this1 said:

 Ladies and gentlemen, this is Christian (Chris1this1),  I have  re-established my 3/4" tweeter  repair operation.  This time around, I am able to precisely match the winding techniques used originally by AR. I am very satisfied with the run I did for my AR LST-2, needing all 6 tweeters rebuilt.  I have done comparisons with fully operational original tweeters and the sound is indistinguishable between the original and the rebuilt.  Unfortunately, I had to raise the price a bit due to the amount of time it takes on each tweeter but I feel you are guaranteed to get a great sounding tweeter  with the proper output still for a lot less than well preserved  examples of original tweeters.  Plus, there's no guilt when driving these rebuilt tweeters hard, since i've always felt like I didn't want to damage original ones so always took it easy on them.  I'm only listing two at a time, to make it feel like less of a job but more of an expression for my passion of these vintage acoustic research speakers.  Feel free to check out my eBay auction for two available rebuilding services. Cheers!

If you plan on operating for a while I'll eventually get some AR-5 tweeters off to you

Roger

[RoyC]

4 hours ago, Chris1this1 said:

 Ladies and gentlemen, this is Christian (Chris1this1),  I have  re-established my 3/4" tweeter  repair operation.  This time around, I am able to precisely match the winding techniques used originally by AR. I am very satisfied with the run I did for my AR LST-2, needing all 6 tweeters rebuilt.  I have done comparisons with fully operational original tweeters and the sound is indistinguishable between the original and the rebuilt.  Unfortunately, I had to raise the price a bit due to the amount of time it takes on each tweeter but I feel you are guaranteed to get a great sounding tweeter  with the proper output still for a lot less than well preserved  examples of original tweeters.  Plus, there's no guilt when driving these rebuilt tweeters hard, since i've always felt like I didn't want to damage original ones so always took it easy on them.  I'm only listing two at a time, to make it feel like less of a job but more of an expression for my passion of these vintage acoustic research speakers.  Feel free to check out my eBay auction for two available rebuilding services. Cheers!

Christian,

Are you replacing the voice coil? What is the DCR of your rebuild?

Roy

[Chris1this1]

Roy, 

Yes the voice coil is replaced. Typically the 2ax style measure 6.3 ohms on my Fluke 87V, and the AR3a around 3.1 ohms. 

[Chris1this1]

That would be me, feel free to ask any questions!

[owlsplace]

Picked up on the old thread. Glad someone has taken on this job ...

Roger

[GlennW]

Last year I received a set of AR3a speakers.  A good friend is a woodworker - and a neighbor gave him the speakers because they did not work and thought they would be a nice source of wood. 

I went though the Restoration manual.  Comparison with the crossover photos and driver photos place the speakers as vintage 1969.  My speakers have good woofers, surrounds were fine.  The original owners had them serviced in their lives.  On first play, the woofers were all that were heard.  I rebuilt the crossovers, replacing the capacitors with new film types, the 150 microF unit with composite of NP and film.  All the pots were open circuit to the wipers.  I did not try to repair or replace the pots.  Instead I used fixed resistors matching the "white dot" values for the pot settings.  The midrange and tweeters all passed the resistance measurement tests. 

I have never had AR speakers before.  Firing them up was my first exposure to the AR sound.  My first impression was they are more laid back than I like.  Tweeter output was there but subdued.  Bass and mid performance is very nice.  Over the course of several months use the sound got worse.  It seems tweeter output is now almost nonexistent.  Time to get tools back out.

I hooked up a signal generator directly to the tweeter leads.  A 3000 Hz signal was rewarded with output, but as frequency was raised output quickly fell.  The units had no audible output at 10,000 Hz.  I removed the tweeters and retested with same result.  To test my signal generator, I repeated the tests on a known good tweeter (Vifa D19TD).  The old Heathkit signal generator is fine.

My experience is that the tweeters definitely degrade.  My own repair plan is to replace mine with Vifa D19TD tweeters that I have on hand.