Restoring a set of AR LST

[Cube4Square]

Greetings AR fans. I am new to the site so still doing a lot of reading through the forum.

This past weekend, I became the new owner of what appear to be an original set of AR LST speakers. They seem to be in pretty good shape on the tweeters/mids. One woofer needs a new surround and the front controllers were removed and holes plugged some time ago, so going to be a slow process.

I have done some initial searches for LST's on the site and still have a couple of pages to review. If anyone has info on a good source for surrounds, I would appreciate any information. I'll post some pics when I get a chance.

[mocmoon]

Greetings AR fans. I am new to the site so still doing a lot of reading through the forum.

This past weekend, I became the new owner of what appear to be an original set of AR LST speakers. They seem to be in pretty good shape on the tweeters/mids. One woofer needs a new surround and the front controllers were removed and holes plugged some time ago, so going to be a slow process.

I have done some initial searches for LST's on the site and still have a couple of pages to review. If anyone has info on a good source for surrounds, I would appreciate any information. I'll post some pics when I get a chance.

I order from this ebay seller for my LST/9/3a foam surrounds:

http://cgi.ebay.com/AR-LST-Speaker-Foam-Re...=item45e00fb447

George and Allison are very nice. Make sure when you place an order to ask for the thinnest and most pliable possible. I've order from them many times (for me and for my AR friends) and found that the quality of the foam surrounds are not always the same.

[Cube4Square]

I actually already had those on my watch list and was hoping someone could offer a reference. After looking at the woofers again, it is obvious one of them was reconed at some point as they do not match exactly. However, they appear to be the same baskets. Although I will probably not recone them just yet, any sources for recone kits/services?

I am new to speaker restoring and have a long learning process ahead of me. And before anyone comments, I do not plan to learn on the LST's, I have a couple of other speakers to start my hands on experience. Probably still not enough, but have to get started somewhere. ;-)

There is no rush on my part, just gathering information/knowledge/contacts, etc. as I make plans.

Since they are missing the front controllers, I'll obviously have to find replacements from a parted out set, I assume these were unique to the LST models, but how about the drivers. In reviewing other posts/comments, I'm not clear if other AR model drivers are the same or not, it seems a slight majority say all of the LST drivers were unique and not used in other AR models. Any thoughts?

[JKent]

Welcome to CSP!

Most people here like Bill LeGall at Millersound for re-coning and any other advanced speaker repair (my own local tech recommends him too).

http://www.millersound.net/indexfl.htm

If you look on the HOME page here then go to LINKS there are resources listed. One is Carl, who is a frequent contributor here and is also recommended by the members for speaker repairs.

You'll will hear from LST owners regarding the controls. They may be available from ebay seller Vintage-AR. He is also listed under LINKS.

Good luck

Kent

[genek]

Since they are missing the front controllers, I'll obviously have to find replacements from a parted out set, I assume these were unique to the LST models, but how about the drivers. In reviewing other posts/comments, I'm not clear if other AR model drivers are the same or not, it seems a slight majority say all of the LST drivers were unique and not used in other AR models. Any thoughts?

The LST used the same drivers as the AR-3a. It was discontinued the year before the ADD models came out, so I think it's unlikely that drivers from that series were ever used in new units, though they may have been supplied as service replacements.

The controllers are multi-pole rotary switches. The LST schematic (have you found that? it's in an old forum post, not the library) shows a Mallory part number, but the odds are you're not going to find that particular switch still in production.

[Cube4Square]

I took some pictures today. From the few rear reference pics I have seen, it seems the set I have has been modified to move the front controller to the rear panel. There are two sets of switches there. Can anyone confirm?

For the drivers, they look to be all original, I think.

[mluong303]

Congratulations and welcome on board,

Your AR-LST may have been the very last production pair while AR is planning to utilize the AR-10Pi/AR-11 tweeres. You may have a unique pair of AR-LST with factory crossovers with 3 position switches replacing the front 6 position controller. If possible, could you email me high resolution pictures of both crossover boards while you have both woofers off for re-foam. Thanks.

Minh Luong

mluong303@aol.com

[Carlspeak]

I tend to agree with Minh Luong's assessment of their vintage. The back wired mids and tweeters are an indication of late vintage components. It will be interesting to see the crossover pics.

[genek]

Your AR-LST may have been the very last production pair while AR is planning to utilize the AR-10Pi/AR-11 tweeres.

Or maybe he's acquired Ken's old speakers with all those free tweeters that AR gave him after he blew his out...

[Steve F]

Tom Tyson and I discussed the subject of ADD tweeters in the LST quite a while ago, off line. He said that while using ADD tweeters was contemplated for the LST (I think Victor Campos was head of eng/product development at the time), it was never done in production.

Therefore, I think these are probably one-off mods, perhaps due to the owner's inability to locate original hard-dome 3a tweeters. From the pics, it looks as if only the front tweeters (with the white ring on the faceplate) are the later ff-cooled tweeters; the side tweeter appears to be an LST/3a tweeter.

Steve F.

[frankmarsi]

I tend to agree with Minh Luong's assessment of their vintage. The back wired mids and tweeters are an indication of late vintage components. It will be interesting to see the crossover pics.

Here-E, Here-E, twelve o'clock and all is not so well!

Personally, I might possibly agree with Minh Luong's assessment of their vintage as well but, looking at the construction of the back panel on those LST's in question, it looks like this was a 'ham-fisted' re-do of these poor LST's. Looking at the finger busting room left for the terminals and toogle switches and the absence of the required fuses, it appears to be a later-on attempt at fixing these guys. I certainly could be wrong, but I don't think the AR corporation would have done such a 'patch-up' job on their 'flag-ship' model. If one would notice the white sealant putty being squeezed out from the back control panel, I'd say this is further proof. That compounded by the later addition of AR-9 and AR-11 tweeters, which I myself would be so lucky to have in mine, is more evidence.

Dear new-owner, consult with Minh (and others) as he's had more LST's than me, the 7+pair he had compared to my present ownership of 3 pair, could speak of more knowledge. As these speakers are so intoxicating to listen to, I actually wish I had more of them, believe it as greed is very common these days. In 'common-terms' they're like the old car you just know is rare and that you are willing to make almost any sacrifice for, or that beautiful woman whose gonna give you a hard-time, but you're just not gonna give-up, as the pleasure is too great to behold and never let-go of, talk to the stars, they'd know! I've been there and done that too many times. To quote the GREAT "James Cagney". "Top of the World Mamma"!

New LST owner, if your mind and back and biceps and fingers can carry the situation, do it, it'll be one of your best decisions made to hear music as it should be heard! Or think what "Little-Feat" said, "You'll know when your mind makes a promise that your body can't fill"! Go for it!

Good luck! Men are generally speaking, born stubborn, and when it comes to these speakers, speaking for myself, I've made many hard-faced decisions to keep mine alive at any cost!

FM

P.S. I'm so glad we've moved away from talking about AR-4ax's for a change, that was crazy.

P.S.2, would some one please tell me the accurate number of LST's produced? I've read there were either 1500 pairs, or even 3000 pairs, but never a true number, any idea out there?

P.S.3 I usually don't go higher than 90 to 95 db (as per P.E.'s entry level SPL meter) with my 'vinyl' listening, but I do go higher (of course) with my 'CD' listening, can any one describe their own listening habits with AR-LST's? I've been listening to speakers for a long, long time and believe in most 'real- listening' sessions, levels need to approximate 'live-levels', or music sounds simply 'recorded'- (dead and 'too-laid-back' with AR's, unless a 'parametric-equalizer' is used) and not 'real'. I hear and see that modern listening tastes have changed in the present world, AR's at this point need a 'boost' to be accepted in today's terms of listening trends. Oh, sorry that I'm being honest here and causing some slight disturbance about the topic of 'real-vs-live' but, some things do change whether I or we choose to admit it or not. It's amazing for the fact that my one set of four AR-LST's were actually used in a "Broadway" theatre from 1972 to 1986 before I owned them. These guys almost seem to want to continue doing the same they always did and continue to sound live. Long live AR-LST's! I'll go as far as to say; I bet no-one has AR-LST's that have actually been used in a 'real-theatre' to reproduce 'live-sound' as it was actually being made and people were paying good money to hear it.

Fear not, my 'babys' are in great shape and not 'burnt' from being too old and worn.

A further testament to "AR's" belief in 'hand-made' speakers.

FM

[RoyC]

but, looking at the construction of the back panel on those LST's in question, it looks like this was a 'ham-fisted' re-do of these poor LST's. Looking at the finger busting room left for the terminals and toogle switches and the absence of the required fuses, it appears to be a later-on attempt at fixing these guys. I certainly could be wrong, but I don't think the AR corporation would have done such a 'patch-up' job on their 'flag-ship' model. If one would notice the white sealant putty being squeezed out from the back control panel, I'd say this is further proof.

I agree with Frank. Those terminal boards do look like transplants...maybe AR-11? The crossovers should prove interesting.

Roy

[Cube4Square]

OK LST fans, here are the crossovers.

From my newbie observation, they look to be the same. Is there any chance these were an older set upgraded near the end of LST's run to the last stage of components? The guy I bought them from was the 2nd owner who bought them around '80, I think, since he said they were only a couple of years old. What he meant was that he bought the set from the original owner who supposedly had them a couple of years. What I have determined is that the original owner did purchase the amp/preamp in '78 since I have the receipt.

The original owner bought a Phase Linear 400 amp and 4000 Preamp in '78 (with wood cases too!! But that's a different subject), so perhaps he had some work done on them around that time??

Below are the pics of both crossovers and the back panel of the other speaker:

[Mexicomike]

those pics don't look anything like the original Crossovers in my LSTs and the controls look like a much simpler design. Both look very Un-AR-like to me for that era but, as you noted, maybe they were an "end of production" change?

[mluong303]

I was hoping to see if these are the AR prototype which use the AR-10Pi/AR-11 tweeters version but the crossovers shown are too much of a home made and they don't look like a factory job even for prototype standard! Thank you for posting the Xover pictures.

Minh Luong

[Carlspeak]

WTF? Those crossover pics are a real mystery. The parts look like something AR could have cooked up but point to point wiring?

Can we we get Roy Allison involved to maybe make some sense out of this?

Tom T? Anybody? !!!

[Cube4Square]

Thanks so much for the feedback, so far. Any help to identify these models is appreciated. Although the crossover looks "newer" than the Mexico's set, the back panel connectors look to be authentic, but that is purely speculation on my part. The front panels did apparently have front mounted controllers at one point because there is still a metal label on one side with a 1 - 6 designation, but then they moved it to the back at a later date.

As mentioned initially, I'm in no rush here, I have some other speakers to start with that will be a good learning experience, but I'd like to figure out what I need to be on the lookout for.

Are the drivers in this set worthy of being in an LST? I think I read that they were solid versions, just want to confirm.

[genek]

A while back somebody mentioned a mod they'd like to do to the LST that would have eliminated the autotransformer. I don't see one in this pair. I also don't see a removable crossover panel, unless the pics just don't show it? Maybe someone working at AR found a pair of unused LST cabs in storage somewhere and decided to cobble together a pair using whatever parts were available.

It would generally be better if all the tweeters were of the same type to avoid unbalancing the sound on and off-axis, but not sure how big a difference it makes if they're distributed symmetrically.

[KlausDK]

Thanks so much for the feedback, so far. Any help to identify these models is appreciated. Although the crossover looks "newer" than the Mexico's set, the back panel connectors look to be authentic, but that is purely speculation on my part. The front panels did apparently have front mounted controllers at one point because there is still a metal label on one side with a 1 - 6 designation, but then they moved it to the back at a later date.

As mentioned initially, I'm in no rush here, I have some other speakers to start with that will be a good learning experience, but I'd like to figure out what I need to be on the lookout for.

Are the drivers in this set worthy of being in an LST? I think I read that they were solid versions, just want to confirm.

I think the crossovers look pretty authentic too.

If you take a look at the AR LST flyers in the Library, the latest flyer (usually referred to as number three) has the LST pictured with the AR 10Pi/11 tweeter , that you have in yours (200011-1, there is a sticker in the back of one of your cross over pictures). I remember Tom Tyson once mentioned that while they were never put in production with that tweeter, there were some made, and he mentioned that Julian Hirsch had a set of LST's with the new tweeters. However, looking at your pictures, the tweeters are of different age, and as Steve F notices, at least one of them is the original AR-3a/LST version tweeter.

The fact that the tweeters and midranges are backwired, shows that this is a late production LST, assuming that the woofers are original, you can see the production date of the drivers there (usually stamped on the magnet). I think you have a very unique set of LST's and would strongly recommend you to consult with Tom Tyson before you decide to make changes.

Congratulations on the find and BRgds Klaus

[kkantor]

OK LST fans, here are the crossovers.

From my newbie observation, they look to be the same. Is there any chance these were an older set upgraded near the end of LST's run to the last stage of components? The guy I bought them from was the 2nd owner who bought them around '80, I think, since he said they were only a couple of years old. What he meant was that he bought the set from the original owner who supposedly had them a couple of years. What I have determined is that the original owner did purchase the amp/preamp in '78 since I have the receipt.

The original owner bought a Phase Linear 400 amp and 4000 Preamp in '78 (with wood cases too!! But that's a different subject), so perhaps he had some work done on them around that time??

Below are the pics of both crossovers and the back panel of the other speaker:

Those crossovers are not from the factory. Not a chance. Here's my read:

Over the years, several LST owners have contacted me about the possibility of removing the autotransformer and replacing it with a garden variety crossover and a level switch. For whatever reason, they became convinced that the transformer was a problem. What you have is the result of one of these modification attempts.

-k

[mluong303]

If you will take the trouble to check and write down all the values of the resistors on two switches, the values of the three capacitors along with the single resistor on the Xover board and the part #s of three coils then I am sure someone will verify if they are indeed a cut apart AR-11 crossovers?

You have 7 soft dome (AR-11 + AR9 version) out of eight tweeters, maybe the cheapest way is to locate one soft dome AR9 tweeter to swap out the last paper dome tweeter.

Yes, Julian Hirsch's LST speakers did have 8 beige AR-10Pi tweeters with two 6 position switches on the front baffle. Maybe one use for the new tweeters and one kept for the original midranges and woofer. I was hoping someone in the CSP bought and own this special pair.

Minh Luong

[Rlowe]

As Minh has mentioned Julian Hirsch's LST speakers, I tried to find Tom Tyson's reference in the current Forum pages, to the Julian's LSTs, but I couldn't.

So I've included Tom Tyson's notes from the earlier version of the CSP - May2005, with a couple of pics.

AR_TT_on_JH_LSTs.pdf

[genek]

As Minh has mentioned Julian Hirsch's LST speakers, I tried to find Tom Tyson's reference in the current Forum pages, to the Julian's LSTs, but I couldn't.

So I've included Tom Tyson's notes from the earlier version of the CSP - May2005, with a couple of pics.

I think we can put aside any notion that the pair of LSTs in question here might have been Mr. Hirsch's custom reference pair.

[genek]

Those crossovers are not from the factory. Not a chance. Here's my read:

Over the years, several LST owners have contacted me about the possibility of removing the autotransformer and replacing it with a garden variety crossover and a level switch. For whatever reason, they became convinced that the transformer was a problem. What you have is the result of one of these modification attempts.

So what do you think the OP's best option is? Try to rebuild the original crossovers from schematic, or live with these the way they are? Was the autotransformer that appears to be missing from this pair an off-the-shelf part, or custom-built for AR?

[Mexicomike]

So what do you think the OP's best option is? Try to rebuild the original crossovers from schematic, or live with these the way they are?

Well, from what I'm reading, if I understand this correctly, the Xover is not from an LST, and the drivers are not those used in an LST so the only "LST" thing is the box. That doesn't mean the speakers don't sound good and if they do, I'd just use them as they are. If they don't sound so good, I'd part them out. Obviously, they can't be sold as "AR LSTs." Another option would be replacing everything with original stuff/new caps but that might cost more than it's worth. A lot of it depends on a personal view of this sort of thing...if you want speakers that say "AR LST" but it doesn't matter whether anything in the box is original, what the heck?