AR-LST Project

[meta_noia_fot]

I’ve been watching the price of a pair of LST’s drop precipitously in New England the past few weeks. This week they dropped in my price range. Today I spent 7 hours in the car but came home with serial nos. 442 and 475. Here they are in a too small room.

They are missing badges, the original grill cloth has been replaced (competently though with acoustic cloth), and the woofers have been refoamed (although with a splice in the surround). To my shock, all 18 drivers are original and working. And they sound pretty terrific, easily beating the Twelves they’re currently resting on. The sound is so good I’m wondering if they’ve been recapped or perhaps have nice Sprague caps in them. I’ll open them up in the next couple of days and have a peek. 

Big, exciting day over here. 

[Aadams]

I am glad they are in the hands of an AR enthusiast.  There were only around 1500 pair made.  You will do them justice. 

[DavidR]

FANTASTIC SCORE.

Give us your impressions once you've had a good chance to audition them.

Bonus to get them with all drivers working.

[meta_noia_fot]

3 hours ago, Aadams said:

I am glad they are in the hands of an AR enthusiast.  There were only around 1500 pair made.  You will do them justice. 

I’d never seen a pair come up for sale within a day’s drive. I only found out how rare they are yesterday when I read a thread on CSP that Tom Tyson chimed in on. I’m very excited to get these performing their best.

3 hours ago, DavidR said:

FANTASTIC SCORE.

Give us your impressions once you've had a good chance to audition them.

Bonus to get them with all drivers working.

Huge score! I can’t believe that 18/18 drivers are working. I should buy a lottery ticket.

—— 

Earlier I tested the LST’s with the center grill on since I didn’t have enough time to take off the spectral balance knob. Now that I’ve taken the grill off, I can see the good and the bad. 

The good is that all the mids and tweeters look totally undisturbed. The bad is that the refoam job is bad beyond just having a splice. Lots of adhesive, and the splices are particularly bad. There is so much glue that the surround is totally stiff at the splice. I have no doubt this is affecting performance of the woofer. I’ll add a refoam to the to-do list  

I know we all love photos. Here’s some more, including a pretty bad foam splice. The top veneer shown is the worst of the two.

[Aadams]

They are in a really good, restorable state.  Don't forget to replace the FNM 2 fuses with new ones.  Old fuses can cause quirky behavior in LSTs and make you question your restoration work.  Seeing the back panel, I am going on record saying they have Spragues inside.  

Every piece of info you will need is spread over the twenty years of posts in this forum and the library. 

 

 

[RickB]

My favorite speakers of all time!

[xmas111]

How ironic, when I bought my LST's just over 10 years ago I had about a 7 hour drive too (Plymouth MA to somewhere in Maine, don't remember exactly where any longer) and they also had black grills. Unfortunately I can't find the picture of them with the black grills. Have it somewhere just can't find it.

Good find and good luck with them. They are great speakers!

[meta_noia_fot]

On 9/21/2024 at 8:52 AM, Aadams said:

Seeing the back panel, I am going on record saying they have Spragues inside.  

Mostly right. There are two wax capacitors in each speaker. One is the 6mfd for the tweeters and the other is a double capacitor, 4mfd and 6mfd, wired in parallel to make up 10mfd of the 40mfd midrange cap. All other caps are Sprague. I plan on replacing the wax caps with Dayton polys and leaving all Spragues in place. I’m surprised the tweeter circuits were working well. Every wax cap I’ve ever heard before these was audibly malfunctioning. 

Oddly my crossovers are unlike both versions of schematics on this thread:

Mine has 2 x 5000mfd caps wired in series to make 2500mfd. That is similar to the later version schematic but without a resistor or any other capacitors in that section. 

[DavidR]

On 9/22/2024 at 10:38 PM, meta_noia_fot said:

I plan on replacing the wax caps with Dayton polys

You might find that they will sound right/better with a good NPE.

[meta_noia_fot]

17 hours ago, DavidR said:

You might find that they will sound right/better with a good NPE.

I’m not sure I can hear the difference between caps. “Right” in this case might be new wax capacitors since that’s what I’m replacing. But since that isn’t an option, I’m going with polys for their longevity. Hopefully the Spragues have plenty of life left in them, so fingers crossed the only maintenance I would need to do as long as I have them is replacing the foam surrounds when they need it. 

It depends on the speaker model for me. If I think I’ve picked up something special and I want to put some extra money into the restoration, I’ll do poly caps. I’ve done that for the my -3a’s, and the upper circuits of my -9’s and -9LSi’s. The woofer circuits in those tower speakers are NPE because doing those in poly would be outlandishly expensive. 

There are other considerations of course, but I’m not trying to start the next cap debate. Longevity of life I suppose is my ultimate consideration for capacitors. Doing maintenance on those tower speakers, and even the -3a, is a chore. I’m approaching middle age and I’m trying to do my future 60-year-old person’s back a favor with long-lasting parts. “I can leave those crossovers in place,” I’ll say, “I used polys!” My daughter rolls her eyes. 

But also, I have no historic reference for the sound of these speakers. The -3a came out about 20 years before I was born. I don’t have contemporary memories of fresh from Cambridge -3a’s. Since I don’t have a reference, I’m satisfied that the speakers sound good to me and are “close enough” to right, or original. 

[jnolan5784]

Congratulations, you will be amazed at the capability of these speakers. I would recommend the following:

1. Fuses - cheap, easy

2. Refoam - I would send them off (RoyC or someone else here on this forum). They will use the correct foam and also reallign the coil

3. Rebuild the tweeters - these were probably made between 1971-1973, so the foam in these will be degraded. They may function, but you aren't getting everything out of them. Several on this forum are good (ChrisC, RoyC). I did this on my 3a's that I thought sounded good and it made a huge difference. It will be pricey with 8, but worth it if you plan on 30 more years of using them

4. Caps - I haven't done this, but if there is wax replace. Mine are later models - 2700's.

5. Aesthetics - your preference on grills, badges, etc

Now to the issue of power, don't be afraid of it. These need a minimum of 250-300 WPC. Many on this forum go as high as 700 WPC. These units really inefficient, and come alive over 300 WPC. Use your judgement, but a well driven speaker always sounds better than an under driven speaker. My opinion is around 450 WPC is the sweet spot for LST's. Room placement is also key - against a wall on these. LST's that are restored, well driven, and properly placed will absolutely amaze. 

Have Fun

[meta_noia_fot]

Thanks @jnolan5784. That is a good summation of what I’ve found going through the CSP archives looking for LST info. 

I’m trying to do as much of the work myself as possible which is part of the fun for me. Surrounds will be done by myself. I ordered mine from Rick Cobb and his always seem to work well on AR’s. I’ve done about 20 woofers or so in my time in this hobby. I don’t shim; I use a tone generator. It may be a more amateur way, but it gets the job done and I’ve never had voice coil rub on any of my repaired woofers. 

Caps came in today. New fuses and badges came yesterday. Surrounds are on their way but may be delayed due to the hurricane. I may have the tweeters rebuilt in the future, but right now they’re all functioning quite well (better than my -3a tweeters which I’m convinced need to be rebuilt). I really dread unsoldering and resoldering all 8 of those tweeters, but I’ll do it when I have the money, time, and inclination. 

As for aesthetics, I’m going to change the grill cloth from black to Guilford of Maine Wheat acoustic fabric. I’ve used it on several vintage speaker projects at this point and I like its look. White fabrics are too much for me on vintage speakers. I like the wheat color because it looks clean and new with just a touch of brown that reads as age and character to me. 

I’m not doing anything to the cabinets. That would require removing all the drivers too. Plus my veneer work on my finished projects ranges from “bad” to “okay” right now. I’ve certainly been saved from some poor results by members of this board. Maybe whenever I decide to have the tweeters rebuilt I’ll refinish the veneer. More long-term. 

———

Since you brought up room placement and power, let me ask about those. 

I have one room these LSTs could possibly sound good in. Old house; small rooms. It’s our living room. It’s wide but shallow. The room measures about 11’ deep (or about 8’ from the front baffle of my LSi’s to listener’s ear) by 22’ wide.

How much power would be enough for these to sound good at a reasonable volume in that small of a space? 

Additional difficulty: Our only TV will be mounted between them because this is the living room after all.^ Which means I need an A/V receiver.* A/V separates seem to get really expensive really quickly, so there’s the issue of how much power I can afford. 

I have experience running 4 ohm speakers on a modern, 50w/ch into 8 ohms Marantz NR1510. There’s a 4 ohm setting and the LSi’s sound fine. Not as good as when they were upstairs running off my 170w/ch stereo amp, but they can get loud enough for the space and I don’t feel the drivers are in danger. But I wouldn’t use the 1510 with the LST’s.~

Stereo equipment is not new to me but A\V equipment is. Anyone have any recommendations for how to power these with these guidelines? 

^I don’t watch much tv but I do listen to a fair amount of music in here with my kid. She’ll be an expert in operating my XA soon. Can you imagine how good the Frozen soundtrack is going to sound on the LST’s?

*I did propose to my spouse having the LSi’s be on the floor and have the LST’s mounted above them with the LST’s powered by a stereo amp. She thought that placement would be “oppressive.” I put my AR-2’s on top of the LSi’s, and—yeah I can see how that much equipment in that shallow of a room could be off-putting, especially to guests sitting on the couch. So the guidelines for this room are that the tv must produce sound and only one pair of oversized speakers. 

~Running LST’s off an A/V receiver might be blasphemy to some on here. I hesitate to bring it up but I need advice. 

[JKent]

Great find! Regarding the AV receiver, I’m very happy with my Onkyo. A lot of bang for the buck. Its rated for 6 ohm speakers but their tech support people told me my 4 ohm Cizek front speakers would be no problem and they seem to work fine BUT the receiver also has preamp out jacks for the front speakers so you can use any separate power amp for just the front stereo pair. 

[Aadams]

1 hour ago, meta_noia_fot said:

I hesitate to bring it up but I need advice. 

Given your limitations for space I think Roy Allison would recommend that you try the placement in this photo.  You can do this because they are LSTs.  The KLHs are just the right height for LST stands. 

Rebuilt tweeters from either of the recommended sources are a huge improvement, no matter how well you think they sound now.  It appears, there is nothing wrong with the cabinets that Howard's restore a finish won't adequately fix. 

[meta_noia_fot]

29 minutes ago, JKent said:

the receiver also has preamp out jacks for the front speakers so you can use any separate power amp for just the front stereo pair

Kent! I bought the bottom of the line Marantz A/V receiver and didn’t even think to check for pre outs. Turns out mine has preouts for the front speakers and subs only. I only plan to use this as a 2.0 setup so that works fine for me. I guess all I need is a stereo power amp. That makes this much easier and affordable. 

[jnolan5784]

The separate stereo power amp will make a tremendous difference. Try SkyFi Audio for amps. High quality used equipment that has been thoroughly checked out and restored. High current, class AB solid states would be my rec. Also if you go for a high current amp, pay attention to cables - you can build them yourself, plenty of YouTube vids on this. 

[meta_noia_fot]

17 minutes ago, Aadams said:

Given your limitations for space I think Roy Allison would recommend that you try the placement in this photo.  You can do this because they are LSTs

Could you explain this @Aadams? I’ve heard of the Allison effect but don’t know what it means. 

Also, to be clear, the room in that photo is my music room, not the living room. I had assumed the dimensions of the music room were far too narrow for LSTs to sound good there. Are you saying there’s a way to angle those speakers to make them work in that size space? I don’t understand the arrows on your photos. 

[DavidR]

https://www.audioasylum.com/messages/speakers/294574/allison-effect

https://db.audioasylum.com/mhtml/m.html?forum=speakers&n=338619&highlight=klipsch+drivers&search_url=%2Fcgi%2Fsearch.mpl%3Fsearchtext%3DTechnics%2BSL-1210M5G%2Bcartridge%26b%3DAND%26topics_only%3DN%26author%3D%26forum%3Dvinyl

 

 

[Aadams]

9 minutes ago, meta_noia_fot said:

Could you explain this

The arrows are pointing to the opposing walls on the left and right.  The LSTs would be flat against the walls.  LSTs and Allison speakers were all about reflected sound being dominant over direct sound. When listening to the LST, there is no practical listening position that permits direct sound to predominate.  If you read the Allison brochures some of the recommended placements for floor standing Allison 3 ways were opposing walls.  The "Allison effect" is about ways to use room gain and speaker placement to optimize bass in full range box speakers. Your LSTs incorporate Allison's work in their cabinet design, which makes the wall become an extension of the speaker baffle if you place them correctly. 

[meta_noia_fot]

19 minutes ago, Aadams said:

Your LSTs incorporate Allison's work in their cabinet design, which makes the wall become an extension of the speaker baffle if you place them correctly. 

Cool! Thanks for the explanation. 

33 minutes ago, jnolan5784 said:

High quality used equipment that has been thoroughly checked out and restored.

My taste in amplification leans towards chunky 80s equipment…hi-fi from when I was a kid but too young to appreciate it. I have a Perreaux PMF 1850 that needs maintenance. Something like that is probably what I’d go for. 

[jnolan5784]

You can usually find good Adcom's (555) or NAD equipment there, but they do have Krell, Crown, or Levinson stuff as well. If you get the arrangement on opposing walls worked out post pictures - It is a really interesting idea. 

[JeffS]

14 hours ago, meta_noia_fot said:

I have a Perreaux PMF 1850 that needs maintenance. Something like that is probably what I’d go for. 

Your Perreaux amp has excellent build quality and is probably easy to service as long as replacement parts are available. If the specs I see online are correct (180W/ch at 8 ohms and 330W/ch at 4 ohms), and if it's rated as conservatively as it's bigger relative (the 2150B), it should drive your LST's nicely.

[JKent]

15 hours ago, jnolan5784 said:

Try SkyFi Audio for amps. High quality used equipment that has been thoroughly checked out and restored. High current, class AB solid states would be my rec. 

I have been to SkyFi Audio in Glen Rock NJ. One of our members, Ben (forgot his screen name) works there. Very nice gear but quite high end ($$$)

[meta_noia_fot]

@JeffSI acquired the Perreaux a few months ago but haven’t used it much. It’s matching pre-amp is in the shop. I had intended these for my -9’s. It does look like it will be a terrific piece of equipment once it’s recapped and serviced. 

@jnolan5784 I checked out SkyFi’s website. Agree with @JKent, that’s some major $$$. Beautiful equipment though. 

Edited yesterday at 07:35 PM by meta_noia_fot
Corrected tags

[meta_noia_fot]

Is this what you had in mind @Aadams? 

You can see from this other angle that I’m in an attic dormer. It’s a small room with angled ceilings. 

——

My surrounds are going to take extra time because of the hurricane. But I have a great friend visiting this week who’s also into hi-fi. I wanted to have these ready for his visit, so I temporarily transferred the woofers from my -3a’s into the LST’s. One is a -3a era and one is a -9 era. It’s close enough that I can play them and start figuring out placement. Yesterday I replaced the wax caps and fuses. 

Listening to some test tracks now…hopefully I’ll be able to listen for a few hours this weekend and form an opinion about how they sound in this room.