AR-LST/2... Finally got them out of the closet

[TomK]

Keep in mind, I last played these 35 years ago, as my AR-2X's are keeping me entertained, I wanted to break the LST/2's out of the basement closet to see if they worked.

A little history about these.      In high school I purchased a Marantz 2235B and Sansui LM-330 (I think) speakers.    I purchased them at my cousin's husband's brand new Appliance and Stereo store.    I was quite happy with this combo, but I did look at the higher-end AR speakers, but they were way beyond my budget.

Unfortunately, his store eventually failed (I think it was something like J&M or J&B Stereo and appliance in Pottsville Pa).  I was really bummed about that.   

Anyway, the brother of my cousin operated a small TV/Stereo fixit shop, and I went over one day and I noticed a pair of AR-LST/2's in the corner, brand new.  I asked him about them, and he said he got them from his brother in law, and he'd sell me the pair for $300, but the tweeters were blown.   If I gave him cash, he'd get me all new tweeters (all 6).   He lived up to his word, and I took them home to my tiny bedroom where these things were just massively too big, but I loved them.  

There's more to this story, but I'll stop and talk about he present day.   I didn't take the speaker grill off, just replaced one of my AR-2X's, fired up Steely Dan Aja album and listened to all the drivers .   All the drivers were making sound, the mid-range and tweeter had that amazing sound that I remembered last time I listened to them.   I noticed however, the bass was noticeably lower than the 2x, so I took off the center grill to see what was happening with the woofer.

Enough typing, now some pictures.

[TomK]

Here's the other speaker.  It's in roughly the same condition, although the wood is a little rougher, but easily fixable.  And yes, the grills need to be replaced.

[TomK]

Unfortunately, on the "other" speaker, I must have rounded out the hex set screw, so I could only peek inside by prying the grills back, but the woofer is in exactly the same condition.

So obviously I need to refoam the woofers, but I've never done anything like this before.    I saw a refoam kit for both speakers on ebay for $28 (roughly) plus handling, but I'm not sure that's what I should be using, so I'm asking the experts here a couple of things:

1) I watched a youtube video on refoaming speakers, and it didn't look hard, just like a fussy arts-and-crafts project.   Do i have that right?

2) What kit should I use?

Any other advice would be terrific.   I think I can make the cabinets look good enough for my purpose (I plan to listen to them, not sell them), my goal is to make them play like a new speaker.

Thanks again.

--Tom

P.S.  I forgot how heavy these things are.

[ra.ra]

Hi TomK, that's a great story....except for the part about these speakers spending 35 years in a basement closet.  Those speakers appear to be in fully restorable condition, but right now your biggest challenge is to conquer that buggered-up set screw in order to remove that center grille on "other".

[TomK]

3 minutes ago, ra.ra said:

Hi TomK, that's a great story....except for the part about these speakers spending 35 years in a basement closet.  Those speakers appear to be in fully restorable condition, but right now your biggest challenge is to conquer that buggered-up set screw in order to remove that center grille on "other".

Actually, getting the set-screw out will just be some patience.   I'm good at that.

The refoaming... what do you think?  I'm watching "How to refoam a woofer - the basics" by Jordan Pier and he seems pretty common sense about it.

[ra.ra]

Re-foaming that 10-inch woofer is not all that difficult and that driver is relatively forgiving. Everyone's anticipation of their first re-foam feels like it will be a nail-biting summit of Mt. Everest, but you are correct that it is actually no more than a fussy arts-n-craft project. Once you have the proper foam surround and a slow-setting glue, the process is mostly a focused meditation, and successful results can be very satisfying. 

Other members will chime in about their favorite source for surrounds, and with the LST-2, you should seek the highest quality foams if they fall within your budget.

[JKent]

Welcome Tom

Beautiful speakers!

Here's my 2 cents: A lot of restorers really like Rick Cobb for foam surrounds. His ebay store is looneytune2001

I have been happy with speakerworks.com

Whatever seller you go with, I STRONGLY recommend you get the white glue. It's similar to Elmer's Glue or Aleene's Tacky Glue and is water-soluble and very forgiving. The solvent-based glue is a PITA.

And although there are different schools of thought, I recommend getting dust caps and shims to be sure the voice coil is properly centered (and to make positioning the cone during gluing much easier).

Here's a YouTube 

 

or here's a step-by-step with still photos: https://www.instructables.com/id/How-to-Refoam-your-Woofer/

Kent

[xmas111]

Sold my LST-2's a few years ago.  (Kind of wish I didn't but I still have the LST'S)

Kent's advice is excellent as usual, listen to him!

Take your time and you should be fine.

The LST-2's are fine speakers and should give you many more years of service.

As for those "Spectral Balance" knobs, I'm pretty sure there's TWO set screws in each of them.

Good luck with them.

John

[TomK]

Kent,

That's a great video.    I now see the purpose of the shims, and that would appear to be the easy way to center the voice coil.   I checked out the ebay contact, and he isn't currently selling foam for my speakers, so I sent him a note.

 

Xmas111,

Yes, I am excited to get them working again and having my setup.    The 2x's I refurbed a couple weeks ago are very credible speakers and they're the best working speakers I have  but I've been looking forward to getting my old speakers working.

As for the set screws, at least my two LST/2's have just one.  What you see on them is not corrosion, it's just crud that will clean off very easily.   

[JKent]

Tom,

I'm sure Rick will get back to you. i "think" what he sells as "Acoustic Research AR2 AR2a AR2ax Foam Surround Speaker Repair Kit -Best Filleted" is probably right for the LST-2 but I don't know for sure. One thing I don't like about his kit--he includes a CD with a test tone for centering the VC. I much prefer shims and a new dust cap.

Here is the "kit" from SpeakerWorks: http://www.speakerworks.com/10-Inch-Angled-Speaker-Repair-Kit-p/swk10a.htm  be sure to get the latex glue--not nitrile.

Note that it is for just 1 woofer so you need 2 kits. You'll also need to measure your dust cap and order 2 more that are just a wee bit larger. Look at yours to see if they are solid paper or slightly porous cloth and then select either paper or screen for the new ones. You'll also need a set of "assorted speaker repair shims". You can phone or email them. They're very helpful.

[ra.ra]

26 minutes ago, JKent said:

I much prefer shims and a new dust cap.

I totally agree about the use of shims, and the water-based glue, but when the dust cap is a unique part of the visual identity of the woofer, my preference is to hinge and re-use the original cap. The flat caps AR used on some 8 and 10-inch woofers are a perfect example, and it is fairly easy to retain the original "look".  Shown is AR-7 woofer with flat cap.

 

[JKent]

Ra.ra has used the "hinge" method successfully. Sometimes it works for me and sometimes it doesn't. Worth a try though. And for the record, SpeakerWorks does have flat dust caps so if the hinge doesn't work out . . .

[TomK]

Now that I've seen the shim method and how it simplifies the entire process, I think things will go pretty well.   I'll continue to take pictures and post them.

Just curious though.... on the 2x's, the main thing I had to do was  replace the capacitor and tweeter level control.    Is there anything similar that needs to be done in the LST/2 crossover?

[ra.ra]

14 minutes ago, TomK said:

Is there anything similar that needs to be done in the LST/2 crossover?

I believe that many LST/2 crossovers used the colorful Sprague Compulytic can-type caps, and those are known to often retain their value quite well. However, the small tweeter cap may be the type in the wax box - - if so, this should probably be replaced. You'll have to take a look inside and report back.

And maybe this will be helpful: I found the pic of my 10-inch 2ax woofer where I used the "filled fillet" type foam surround and also preserved the original cap after shimming. If you do try this method to preserve original cap, be sure to use a fresh #11 blade on your X-acto knife when cutting the cap.  

[lARrybody]

I vote on using filled fillet type surrounds for your woofers.Rick Cobb has them and you can reach him outside of ebay at rcobb@tampabay.rr.com. I have cut new flat dust caps out of a organic egg carton (the old fashioned paper kind) with a Martha Stewart circle cutter from Michaels. You can get some Aleene's Tacky glue there too.

[DavidR]

23 hours ago, TomK said:

rounded out the hex set screw

Try to find an EZ-out extractor. They screw-in in reverse and once they bite it will turn the screw out.

- OR -

If you have an allen wrench you don't are about and if it fits in the hole you can epoxy it with JB Weld Epoxy and turn it out once given plenty of time to cure.

[TomK]

1 hour ago, DavidR said:

If you have an allen wrench you don't are about and if it fits in the hole you can epoxy it with JB Weld Epoxy and turn it out once given plenty of time to cure.

That was one method that I'm considering; I have a set of ez-outs, but the hole is really tiny; I'll test whether any would be small enough to fit without destroying the knob.   And I will have to get another hex set screw that would fit.   

I'm going to let things sit as is until the surrounds come in.  I do need to finish the speaker cloths for the 2x's to put that project to bed.   Once that's done, I'll work on the set screw, take the woofers out and determine if the crossover has caps that need to be upgraded.   I'll probably test any capacitors  in the box to see if they still meet spec.

[JKent]

PB Blaster https://www.amazon.com/Blaster-Chemical-Penetrating-Catalyst-18-oz/dp/B07HMLLDXS/ref=sr_1_3?keywords=pb+blaster&qid=1566444499&s=electronics&sr=1-3

[TomK]

8 hours ago, JKent said:

PB Blaster https://www.amazon.com/Blaster-Chemical-Penetrating-Catalyst-18-oz/dp/B07HMLLDXS/ref=sr_1_3?keywords=pb+blaster&qid=1566444499&s=electronics&sr=1-3

I use it quite a bit working on my cars; pretty effective if you're prepared to wait.    Maybe I'll put a drop in there and let it sit overnight.     

These are SAE sized hex screws, I'm hoping I can get a metric hex key in there that's a bit over-snug, tap it in with a hammer and unscrew it.   Any idea of the diameter and thread pitch of the screw?  I'll be looking for a replacement.    

[RTally]

I am firmly in the camp of using a tone to magnetically center the voice coil. The advantage is you do not have to mess with the dust cap - no cutting out the dust cap, no gluing it back in.

For the tone method, use a tone generator (I have an app on my phone) and play a 30 to 40 Hz Hz tone through the driver. Play the tone only loud enough that you can feel the cone move.

I glue the inside of the surround to the cone and let it dry. Then I attach the leads from my stereo to the driver and get ready to play the tone. I glue the outer edge of the surround to the basket and then play the tone as I press the surround edge in place.

Using Aleene's glue, I have a couple minutes to mess around with the cone and surround to ensure all is well. Before the glue sets, I turn off the tone and then play with the cone. Push it in evenly and see if you can hear or feel any scratching. Press on each side and see what you notice. I do this so that I can learn what happens when the cone is not centered.

I then play the tone again to ensure the VC is centered while going around the edge of the surround to ensure it is seated and the glue is starting to cure. When I am satisfied, I turn off the tone and let the glue cure. Sometimes I clamp the surround to the basket to hold it in place. Other times I just keep pressing around the surround until the glue dries. Aleene's sets up in about 5 minutes.

After the glue is cured, press the cone evenly around the VC to ensure there is no rubbing. I've done dozens this way and have never had a problem. You are done. 

[TomK]

After a crazy week at work, I had a fruitful weekend working on my speakers.

I first put renewed cloth on the AR-2x speakers I'd been working on.   I realized that although it was advertised as "replica AR material" that I bought about 8 weeks ago, it's not.   I didn't do an artful job, but it's a good enough job that my wife finally said "they look really nice!". 

Anyway, my first task on the LST2's was to re-foam one of the woofers.  Removing the hardened foam from the paper cone was easy, but the glue they used on the surrounds was a hardened version of an industrial adhesive that resisted any attempts at removal with a chisel or knife (which explains the scratches).  As you can see, I eventually got all of it off....

[TomK]

it resisted goof-off, but mineral spirits softened it enough that I could eventually  work it loose through a combination of pulling at it and rubbing it with cloth.   It took about an hour to get that adhesive off.   The second woofer didn't end up as scratched (not that it matters, you can't see it) because I didn't attempt to use a chisel or knife.

This was the first time I'd tried to re-foam a speaker, and  the only thing difficult on these particular speakers was the screen that prevented me from pressing the edge of the cone into the foam.    But I like how that white glue tacks up in about 3 minutes making it easier.

I purchased two re-foam kits, one from vintage-ar and the other from looneytune2001.   I figured I'd screw them up once, but it turns out I didn't.    I used the looneytune2001 kit which uses a 30hz wave on CD to center the cone rather than using shims.   Thought I'd give it a try and if it went horribly wrong, I'd use the foam from the other kit.   In my two speaker experience, one centered the voice coil all by itself, the other, I had to play with a bit, but it didn't take me more than 15 seconds to center it by hand.

 

On the set screw, I first have to apologize to xmas111. There are indeed two set screws.  I got the stuck set-screw out by using a different hex key (which was the same size, but apparently a hair bigger), and that got it right off.  In fact, I had to use pliers to pull it out of the set screw.

So had AR not used that weird paste on the metal frame, the re-foam would have been quick and easy.

I've been listening all night to the newly fixed speaker.   They're every bit as good as I remembered.   Love the sound of these things.  I feel like the bass isn't as loud as the 2x, but it sounds better controlled (maybe the new foam surround versus the cloth surround?), and the addition of a real tweeter really opens up the high-end.   I still like the 2x, but the LST2 is just plain better.

I'll have to see if the library has the original owner's guide to the LST2.  I'm curious about AR's recommendation on placement (if they had them).

 

[GD70]

Terrific, and somewhat rare speakers. You've received excellent advice. Keep going!

I cut my dust caps as ra ra's pics illustrated. The open can lid approach insured perfect alignment when reglued later.

Mine were in pretty rough shape when I found them on a CL listing. They required a complete re-veneer, gluing all six grill frames back together, and replacing the grill cloth, woofer refoam, and replacement of 6 blown tweeters. Roy C. recommended the HiVi tweeters with a minor crossover tweak and resistor addition. 

Your cabs are not bad at all. A light block sanding, and wipe on several applications of Watcos oil will make them look new!

Cheers, Glenn

[TomK]

I decided to try the 30hz tone method just because, as I said, if it all went south, I would just redo the foam surrounds.  But it seemed to work.  The first speaker I had to gently shift the surround, but the second speaker centered itself just playing the tone.   They really do seem fine.

As to refinishing....

I've already block sanded the more scratched up cabinet, and it turned out pretty well (I'll post pictures after the weekend).  I basically followed the advice I got here which is to finish with boiled linseed oil cut with two parts mineral spirits.    They look really good; in fact, when I finish the LST-2's I'm going to go back to my AR-2x project and do a quick sand and oil (those are basically perfect, except they just need a refresh, so I'll start with a 240 sandpaper just to get past the top surface; I don't want to take too much of the veneer away).

The part that irritated me was I didn't realize that some of the veneer was already pretty badly damaged in a 2" by 1/8" section on the left angled side of the front;  I used some tricks I found online with walnut colored wood filler and a little artistry with slightly darker stain and toothpick to to make it invisible from more than two feet away.   The right thing to do would be to replace that section of veneer, but I don't know where to find something that would match in color, grain, and age, so that is not going to get done unless I discover something that matches perfectly.

The sound has been pretty much as I remember in the late 70's since I did the re-foam.     Once I refinish the second cabinet, I'll work on replacing the cloth grills with the recommended replacement.  At that point, I'll probably tinker a bit; I still haven't checked the crossovers yet to see if they're still in spec. 

I'm also considering having my Marantz 2285B professionally refurbished so I can enjoy it another couple decades.   That will have to wait because that's pretty pricey.

[TomK]

Well, the speakers are now in a visually presentable condition.

This is the left speaker that was so scraped up on top is now on my workbench after being sanded:

.

 

You can tell because it has that weird crescent moon "mark" in the wood.  I'll say that the mark was there since they were new, it's kind of like a birthmark.   You can see the view from the top:

So not to drag out the suspense, but despite this one looking like the far more damaged cabinet, actually this one wasn't bad at all.    I used boiled linseed oil mixed with two parts mineral spirits.  I had never tried linseed oil before, but in the next post, you can see the results

Just an FYI, the two front posts on the speaker are not veneer, they are solid walnut