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AR9LS/98LS/78LS dual dome drivers CAN be repaired!


Kuja

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Hello,

I thought that this information might deserve separate post, because it gives hope to owners of LS/LSI series of AR speakers... everywhere on the Internet I was told that those dual dome drivers are not repairable. Well, this is not true:

(I already posted this as a followup to my older thread regarding problems I had with my newly acquired AR98LSs:

http://www.classicspeakerpages.net/dc/dcbo..._id=5848&page=)

...those AR9LS/98LS/78LS dual dome midrange/tweeter drivers CAN be repaired!

I've found a guy that runs a speaker repair shop and also makes speakers under his own brand.

I told him that everyone I asked (including AB Tech) said that those drivers couldn't be repaired. His answer was that if human hands did assemble something, it can be repaired whatever the problem is! It is only the matter of cost effectiveness.

And he repaired them!

One unit had no ferrofluid at all! Due to excessive heat, some sort of blisters formed on the spool. He even managed to make a new spool...

I asked him to do his thing to all drivers (renew the ferrofluid, etc...). Then we refoamed again all woofers and lower midranges with softer top quality surrounds. Somebody who did prior refoaming, for some reason threw away masonite rings from 12" woofers.

"My" guy made new ones. He was/is authorized AR repairman for more than 20 years (I think) so he knows what he's doing.

Complete overhaul on all eight drivers was around 300 $.

They sound much better now. Right now, I'm in the process of rejuvenating the crossover with polypropylene capacitors, some van den hul, some silver litz wire... I'll upgrade them to the 98LSI schematics too.

I also found the source of hand made wool felt, so I'll even add the acoustic blanket that was missing on the originals

This guy's website is www.sinevoice.com ...

I hope this was useful info.

Aleksandar

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Guest bocoogto

Have you updated the crossover to the improved version for the AR9LS? Schematic of the old and improved is on the classicspeakers website.

This makes a tremendous difference in how these speakers sound.

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Guest Bret

You didn't say how certain you and he are about the performance of the repaired units.

I have no reason to doubt that they are perfect, but I was wondering if he individually lab-tested his handiwork. His website makes it look as though he may be that sort of man.

Bret

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  • 6 months later...

>everywhere on the Internet I was told that those

>dual dome drivers are not repairable. Well, this is not true:

>

>(I already posted this as a followup to my older thread

>regarding problems I had with my newly acquired AR98LSs:

>http://www.classicspeakerpages.net/dc/dcbo..._id=5848&page=)

>

>...those AR9LS/98LS/78LS dual dome midrange/tweeter drivers

>CAN be repaired!

>I've found a guy that runs a speaker repair shop and also

>makes speakers under his own brand.

>I told him that everyone I asked (including AB Tech) said that

>those drivers couldn't be repaired. His answer was that if

>human hands did assemble something, it can be repaired

>whatever the problem is! It is only the matter of cost

>effectiveness.

>

>And he repaired them!

I assume that this repairman had the original blueprints and technical specifications on the AR Lambda dual-dome tweeter, and that he could accurately reproduce its technical specifications in his lab. He would also probably be able to show the frequency-response and distortion measurements that corroborate his repair as being the same as the original.

No one is saying that it is *impossible* to reverse-engineer a voice coil and former and place it back in the magnetic assembly. The problem is being able to make a repaired tweeter that approximates the original; and without prints and technical specs, such a tweeter may or may not replicate the original speaker's response. It will no doubt play music and make sound -- and it might sound good -- but without that technical information there are doubts as to the repaired-unit's performance. Ask the repairman to test the tweeters and supply you (and us) with the curves so we can compare them to the original.

I'm not trying to be critical or "rain on your parade." I am just trying to be realistic when dealing with a subject such as this.

--Tom Tyson

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JWS, unfortunately this guy is not located in the USA :(

Tom,

All this happened back in June.

I didn't ask for any measurements, I was happy enough to have them working :)

When I took them back home, I did this:

I converted some music to mono using Cool Edit Pro and I burned it to a CD-R.

I also did cut off all the frequencies in Cool Edit's Pro EQ that would be reproduced by the woofers and/or the lower midranges.

This way, only the dual tweeters were playing.

I gently touched other drivers - no vibrations at all.

I also tried to listen selectively through a pipe and could not hear any music coming from them.

First, I placed speakers in a way that they were facing each other and I did put my head precisely centered between them - sort of huge headphones :)

I even switched sides - in case that I discover that my hearing is not equal on both ears :)

The sound was in dead center.

I also made some tracks on this CD, with the same piece of music only on the left or on the right channel. Again it was made from a mono source.

When I played those tracks, I did put speakers close together, and this time I turned them around so that they were facing in the same direction towards me.

I listened from a couple of meters.

Sound was coming from only one speaker at a time, first left than right, several times in a row.

There was no difference between the tweeter assemblies.

They sounded identical.

One was repaired and one was in its original state.

Later, I repeated this experiment with some friends of mine and everything was perfect again.

This was enough for me. I was very happy.

I don't know if some scientific measurement would show some difference.

My thinking was: If no one can hear the difference, it's good enough for me!

And Tom, you mentioned this dual tweeter assembly as "AR Lambda dual-dome tweeter", what Lambda stands for?

I would like to learn more on these fabulous speakers.

Unfortunately, there is almost no information on them on the Internet.

I would like to find some reviews too...

Thanks a lot!

Aleksandar

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>

>I don't know if some scientific measurement would show some

>difference.

>

>My thinking was: If no one can hear the difference, it's good

>enough for me!

>

>And Tom, you mentioned this dual tweeter assembly as "AR

>Lambda dual-dome tweeter", what Lambda stands for?

>I would like to learn more on these fabulous speakers.

>Unfortunately, there is almost no information on them on the

>Internet.

>I would like to find some reviews too...

>

>Thanks a lot!

>

Aleksandar,

I cannot find the AR document that mentions the "Lamdba" tweeter, so I'm caught out on that designation. Therefore, disregard my use of the term until I can find the document. Lamdba in general does refer to a small dimension, but has other totally non-related definitions. AR publicly referred to the two tweeters with a common magnet assembly as the "Dual-Dome," and that describes a lot in terms of locating the two driver's axes in close alignment, which does improve vertical dispersion issues.

Clearly, the AR-91Ls was an advance in AR speaker technology, and this speaker won various awards and received high critical acclaim. Test reports were extremely favorable. The bass-cavity woofer compensated for the boundary-interference problems associated with the single, front-firing 12-inch woofer and thus enabled this speaker to be placed farther out into in the room without bass-response aberrations. The two woofers produce very deep, low-distortion bass response.

In the end, if you are satisfied with the high-frequency response with the rebuilt tweeters, that is all that really matters. The point that I make -- and I adhere to it -- is that to rebuild tweeters with new voice coils and formers, etc., is much more difficult than it would seem, and usually requires detailed information and specifications on the original device. Therefore, what AB Tech and others are saying is that there is no *practical* repair for a tweeter like this to bring it back to its original performance.

--Tom Tyson

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