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AR-9 Restoration - Pete Basel

Pete B

By Pete B
in Acoustic Research

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Pete B Enthusiast

Pete B

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I just purchased a pair of AR-9s from the original owner who contacted me some time ago to take a look at them. She said she had not used them in 15 or 20 years but had babied them when she was using them. They'd been in storage all that time and are in fairly rough shape now.

I don't think they've ever been worked on before - she said that she never had a driver failure unlike her JBLs where she blew the tweeters several times, however one UMD looks bad - she probably didn't notice.

She powered them with a Soundcraftsmen 250W/ch A5002 amp that she still has - nice and beefy!

It was 20 deg in her garage and it was almost dark when I looked at them. One UMD mid did not look right (stuck out, probably overexcursion) but the rest of the drivers more or less looked okay so I took them.

Veneer is scratched and chipped in several places. There is a .5" by 2" section toward the back that is lifting - it sure is thin. I plan to very lightly sand them, then use Howards restore a finish or perhaps Watco oil on them. Am I on the right track here, or other/better suggestions? There is a section of veneer .2" by about 3" that is cracked off and missing. Any links to good writeups on how best to fix the veneer? Most of the worst damage is toward the back so probably just matching the color to start will make them look good enough from a distance.

The fronts look decent and the felt pads are there and in good shape.

Serial numbers start with AR9K were they all Ks, or does the K have some meaning?

Woofers are all round magnet with 30th week of 1978 date of manufacture.

I am very curious to measure the woofers in system driven directly to determine the Fc and Qtc of the system, and then to also measure the complex woofer crossover transfer function as loaded by the woofers. Also curious about the LMD in system Fc and Qtc.

I've not refoamed a big AR woofer in a while, what is the best foam for them these days? Kent I know you will suggest M-Sound and I will consider them - any others? Links to past discussion here?

I really do not need another long term restoration project so I will probably do a quick fix on the veneer for now, hopefully without causing more damage than is already there.

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RoyC Proficient

RoyC

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I've not refoamed a big AR woofer in a while, what is the best foam for them these days? Kent I know you will suggest M-Sound and I will consider them - any others? Links to past discussion here?

Hi Pete,

There are two versions of the big AR woofer foam being sold, and essentially one wholesaler (regardless of the chosen retailer). They both work satisfactorily, but one is better than the other.

The best version has a slightly larger roll, is dark grey in color, and is made of a higher quality, thinner foam.. The lower quality version is thicker, a lighter grey in color, has a smaller roll, and a wider outer glue lip. I've measured this version to provide Fs 2 to 3 hz higher than the better version. See attached photo...the surround on the left is the one you want.

The wholesaler began selling the less desirable foam awhile back because it was less expensive, but I urged Larry Lagace/"Vintage AR" (who I have been doing lots of woofer work for) to bug them until they consented to sell the better version again. As an aside, the wider glue lip of the "lesser" version fits the cloth surround woofer basket much better if it becomes necessary to replace one of those.

Msound msound@shentel.net is a good retailer because he is willing to sell the foam separately for less than the typical "kit" price. He also knows the difference between the two versions. Make sure to request the better version. Larry is also a very good source for the proper surrounds, but will be more expensive.

...looking forward to hearing of your experience with the AR-9.

Roy

post-101150-0-79882800-1387086705_thumb.

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JKent Proficient

JKent

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ditto MSound. He specializes in very complete kits but if you just want foams or foams & caps or foams & caps & glue ( l like his white "WD" glue) he will work with you and give you a very fair price. Tell him you are a CSP member.

For chipped veneer I have found tinted epoxy works well, especially if it's in an area you may not notice. I have used 2-part epoxy tinted with Mixol #22 (JB Wood Weld is a good epoxy to use). Roy and others have used the Mohawk "tootsie roll" sticks that come already tinted. You just cut off a piece, knead it in your hand and press into place. When it's cured file and sand.

There are instructional videos on the Mohawk site that show how to make a convincing wood grain with their graining pens but I have not tried that.

Good luck!
Kent

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ligs Rookie

ligs

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Pete B,

I am glad you got a pair of AR9s. Hopefully you will be able to examine AR9s as throughly you did with the Advent Loudspeaker.

In AR9's literature it clearly shows the significant rolloff of the 2 AR woofers connected directly to the amplifer vs the woofers connected to the network involving the 2500uf capacitor. Is that for real?

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Pete B Enthusiast

Pete B

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Ligs, do you have a link to the exact document that you're referring to? I do remember reading

the AR literature about the bass section but it has been quite some time.

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Mach3 Newbie

Mach3

Posted
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Pete,

Couple of things;

On my AR-9 I have the 'square' magnet on the woofer.

In regards the woofer crossover - I cut loose the 2500 uF cap and coil. My analysis indicated that this part of the crossover was only there to provide impedance to protect the typical amplifier (receiver) of the era. Without these two devices the two woofers in parallel would represent about a 1.7 ohm impedance at its lowest point - which would pop most amps in the late '70s.

I am not sure what the plot put up by Terry Holl was attempting to say - but when I cut loose those parts I got a lot more bass - tigher (lower Q), deeper and higher volume.

In re the walnut - send me a PM and I can send you pieces of real walnut that you can glue in where there are chunks missing from your veneer. Glue it down, sand it, oil it and you won't be able to see the repair. I will need your dimensions and you will have to "square up" the ding.

recap, rewire and check the woofer can (air suspension chamber) for the 8" - these are always loose from the baffle (glued on OEM).

Great speaker. Good luck,

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  • 3 years later...
Pete B Enthusiast

Pete B

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I'm having trouble getting foam at a good price, MWA doesn't want to sell direct to me

anymore since I've not bought much in the last 5 years or so.  These are not a high

priority since I have a lot of other projects.

I also want the filled fillet foam for the 8", assuming that will work fine, but am not sure where

to get that or what part number to use.

And while I'm at it here, I'm looking for 10" filled fillet foam for several other speakers.

I should not have taken these speakers, the lady really pushed me suggesting that they'd be 

in good hands with me, but they are not in the best condition.  The price was fair but not the

best.

By the way, on mid is popped out and I think the VC hung on the pole piece, any suggestions

to pop it back in?

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Pete B Enthusiast

Pete B

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There is really nothing to see, the mid is at full forward excursion but with one

side a bit more forward than the other.  I have not tried pulling the dome off

of the magnet structure.

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  • 3 weeks later...

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