AR-9Lsi Project

[meta_noia_fot]

A pair of English-made AR-9Lsi’s came my way today. The previous owner had a terrible refoam job done on the midrange and 12” woofers (but forgot the 10” woofers). They also used a brittle glue so the foam is separating easily from the cone. 

Before I refoam these, does anyone know if this midrange cone is correct? There is a seam split on the cone which I’ve never seen on an AR. The owner said they had been reconed but I think he meant refoamed. 
 

edit to add: The driver appears to be correct but is the cone correct? Tonegen part no. 1-2100450B

[Aadams]

The answer is no split cone.  Check AR55s link from the library forum.  The 8inchers for the AR9, ls,lsi were specifically configured to be LMRs.  Read note 4 in the pdf on 8 inch drivers for that series. 

 

 

[meta_noia_fot]

I see the AR part no for the Lsi LMR is 200045. Would that be related to this driver, the 1-2100450B? I ask because all of the woofers in my pair are Tonegen-made and have the longer, alternate part no. Could the English factory have been using Tonegen drivers instead of regular AR parts?

[meta_noia_fot]

Here’s a couple more photos including the seam from the back. Unlike the foam surrounds, the seam seems competently done. Nothing about the spider seems disturbed either. 

[fedeleluigi]

7 hours ago, meta_noia_fot said:

Before I refoam these, does anyone know if this midrange cone is correct?

Yes, the cone is correct!

You can see other identical pictures of the Tonegen AR9LSI lower midrange on this thread (last images): 

https://community.classicspeakerpages.net/topic/10666-8-lmr-for-ar-9-and-ar-90-200027-availabilitysubstitutes/?do=findComment&comment=128245

 

[lance G]

4 hours ago, fedeleluigi said:

Yes, the cone is correct!

You can see other identical pictures of the Tonegen AR9LSI lower midrange on this thread (last images): 

https://community.classicspeakerpages.net/topic/10666-8-lmr-for-ar-9-and-ar-90-200027-availabilitysubstitutes/?do=findComment&comment=128245

 

Result, and within 7 hours the OP has the answer ! To top it all it's one he wants to hear.

Hats off to fedeleluigi !

[meta_noia_fot]

Yes, thank you @fedeleluigi! So to me it appears the 1-2100450B is the Tonegen version of AR 200045 and the Tonegen version has a factory seam split (I wonder why). 

[Aadams]

Yes. Good job!  I have an English pair of 98ls with original LMR that don't have the split. 

5 hours ago, fedeleluigi said:

Yes, the cone is correct!

[AR55]

Although AR changed the cone spec for the 8" LMR between the AR9 (200027) and the AR9LS (200045), the 200045 cone still was specified with no split.

I have had a number of AR98LS's in my possession over the years and all of them came with the American made AR 200045 LMR.  None of those cones had the split.

I presently own a pair of English made 98LSi's and a pair of American made 9LSi's.  Both of them came with the Tongen made 2100450B LMR and all of them have the split cone.

AR outsourced the manufacture of all their drivers to Tongen starting with the second generation of the Post Classic Series, which included the 9LSi & 98LSi.  Interestingly, I haven't found an instance where Tongen ever used a split cone with any other driver, but the 2100450B, 8" midrange.

[meta_noia_fot]

Great info. Thanks so much @AR55

[Kuja]

On 4/21/2024 at 1:41 AM, meta_noia_fot said:

There is a seam split on the cone which I’ve never seen on an AR.

For a couple of years I had a pair of English made AR98LS but with the original drivers made in USA, and they had that split on LMR drivers.

[AR55]

You got my curiosity up, so I rechecked the 8" LMR in the three 98LS' that I've owned.  My daughter has my original 98LS's that I purchased in January of 1983 and their 8" LMR's do not have a split seam.  The same is true of a pair that I restored and sold to a friend.  The 3rd pair, however, have US made 8" 200045 LMR's and their cones have a split seem.  

I also checked my AR-28B's.  Their 8" woofers (model 200050), have a split seam.  

So, it appears that at some point during the initial production run of the Post Classic Series, AR modified the spec for the 8" midrange and woofer cones to have a split seams.

[meta_noia_fot]

I’m in the process of refoaming the 6 woofers but I’ve run into a weird problem and could use some advice. 

I pulled one of the Tonegen 10” downfiring woofers, part no  1-2100330. The spider and cone were incorrectly assembled at the factory:

The spider and cone are fully attached, but at an angle (you can see the original glue filled in where the gap is smaller). Only about 1/3 of the spider is adhered in the proper location. 

Questions:

-Should I attempt a repair at all since the spider is fully attached? I can feel a “center” when moving the cone in and out, and I’m fairly certain I could put a foam on without VC rub.

If I do repair:

-What is the best way to separate the glue used here? I have a cement thinner on hand made of Toluene and Heptane.

-What is the best way to apply thinner in such a small space? I tried a cotton swab but the rounded tip was too large for this area. 

-What adhesive to you recommend using to reattach? I read on a different forum that Alenne’s would be fine for this application. 

-Anything else I should know before attempting this? I’ve never done any spider/cone work like this. 

Thanks in advance. 

[DavidR]

Toluene might do it but you might have better luck with lacquer thinner. Toluene was more commonly used as a carrier and not an adhesive diluent.

See if a small, thin tipped 'paint by numbers' paint brush would get in there.

The only issue I have with Alenne's is: Can it be softened for removal? I haven't tried (yet) messing with some popular adhesive solvents et al.

Lastly, if you REALLY think you can center it without rub then that might be your easiest way out.

Good Luck and wear nitrile gloves when handling toluene and lacquer thinner. Toluene will pull fat from your body right thru your skin.

[meta_noia_fot]

Thanks @DavidR. I’m leaning towards attempting a repair. I think it will always bug me in the back of my head knowing the problem is there. 

According to the Alenne’s website, citrus-based cleaner will unbond it. 

I think I’ll try the thinner I have, and if it isn’t effective I’ll search out some lacquer thinner. 

[DavidR]

1 hour ago, meta_noia_fot said:

I think it will always bug me in the back of my head knowing the problem is there. 

I know the feeling.

Thanks for the tip on the Aleenes

[meta_noia_fot]

Is there any trick to getting through the adhesive connecting the spider and cone? I’m struggling with this. 

I tried the toluene cement thinner without any luck. I bought lacquer thinner yesterday and haven’t had any luck with that either. I used a small paintbrush and I can tell I’m getting thinner applied (I can see it soaking into the spider and cone). I applied several paintbrush tips worth of thinner to a small area, then scraped at the adhesive with a small pick. No luck. At this point I’m nervous about getting too much thinner soaked into the fabric of the cone and spider. I’m beginning to wonder if I should just attempt to put a foam surround on and try centering without repairing this. 

Any help would be appreciated. 
 

[DavidR]

I'm surprised the Lacquer Thinner didn't work. I thought that was what I used on an 8" mid that needs a new voice coil installed.

The only other common solvent used for adhesives would be MEK (methyl ethyl ketone).

[AR surround]

Lacquer thinner or MEK should have worked.  But since it didn't, try 91% alcohol or denatured alcohol.   If that doesn't work, try acetone.

[meta_noia_fot]

Thanks for the suggestions @DavidR and @AR surround. Last night I tried MEK and it seemed to have no effect. I’ll try denatured alcohol and acetone tonight  

Let me ask a very basic question. What should I be looking for when applying? Should the old adhesive gum up? Dissolve? Through my applications of the three previous chemicals there’s been no change, but I’ve also been fairly conservative with how much I apply. Again, I’m worried about the fabric of the cone and spider. 

[AR55]

The AR woofer assembly drawings call for the woofer cone to be attached to the spider with epoxy.  Alcohol should soften the epoxy. 

[DavidR]

Odd, I was able to remove a spider from an 8 inch AR mid with lacquer thinner (rather easily).

However, I don't think the adhesive was epoxy.

[AR55]

I went through all of the woofer/midrange assembly drawings in the AR archives, and they all call for the epoxy (part # 601021) to adhere the spider to the cone.  This is true for all of the 6-1/2", 8", 10" & 12" woofers/midranges that I found in the archives. 

The drawings call for "Adhesive Air-Flex 400", "Adhesive Hapco 400" or simply "Adhesive" (part # 601020) to adhere the spider to the frame. 

[meta_noia_fot]

3 hours ago, AR55 said:

to adhere the spider to the frame

Thanks for the insight @AR55. I’ve just spent 20 minutes or so applying brush tips worth of denatured alcohol to where the spider meets the cone and it’s still not softening. You said above that the epoxy was used to adhere the spider to the frame…was the same adhesive used to adhere the spider to the cone? They are different colors on mine (the brown adhesive pictured above connects the spider to the cone and a white adhesive connects the spider to the frame).

I don’t have any acetone in the house. Last night I glued the inner lip of a foam to the cone. With that installed I’m now about 95% certain I can center the voice coil using the tone generator method without rub occurring. I’m hesitant to keep trying to soften the epoxy at this point having soaked the cone and spider in 4 different strong solvents. 

[meta_noia_fot]

I decided to install the foam on the first 10” woofer as is. 

While slowly refoaming the woofers one-by-one, I’ve been working on the crossovers. I wanted to recap them but had read about how difficult removing the circuit boards is without breaking them. I decided to ditch the boards altogether and build new crossovers.

I have one crossover completed so far. I used an 18”x9” piece of Masonite, which is several inches larger than the original board and about as big a board will fit in the cabinet. I reused the coils and resistors and installed new caps. Primarily Dayton Audio poly caps except for the 470mfd caps where I used npe’s, and the original paralleled 8mfd caps were replaced with a single 16mfd Solen. 

I secured all the parts to the board using zip ties attached to 1”x1” tie-down squares. I worried about the longevity of the pre-installed foam adhesive backing on those squares, so I scraped off all the foam and secured them to the Masonite using E6000. 

It’s certainly not as neat as the original or as some new boards I’ve seen on here and AK. But I tested using all the drivers outside the cabinet and it’s fully functional. 

Later this week I’ll build the second crossover. Cabinet work will hopefully get done this week too. The cabinets are in overall good condition but do need some touching up. There are some water rings, a few scuffs, and some tape residue (possibly from when these were transported overseas). I think I’m going the Restor-a-Finish route on these. Last thing to be done before reassembly is installing the foam for the resonance chamber, for which I purchased 1” foam from Parts Express. 

I have a decent amount of free time this week to put into these. Fingers crossed I’ll be A/B’ing these against my -9’s this weekend.