AR-3a refurbishing

[Guest mdavis]

I have a pair of AR-3a (and AR-4ax's) that I purchased new in 1969. The 3a's have lost all but the woofers (which are still wonderfully tight and clean) due, I suspect, to corroded pots. The speakers have never been over-driven (used mostly for classical music).

Never having torn these down, I am very reluctant to mess them up. I would like to try replacing just the pots for a first attempt to bring them back to life. How practical is that, or is it better to replace the whole crossover? When the speakers were last capable of mid-high range sound, you could occasionally get them to function properly by rotating the pots back and forth and then finding a "good" spot. For that reason, I don't suspect the high and mid range cones to be bad.

Any suggestions on how to proceed and what to look for? I am not eager to tear into these. I have read the overhaul instructions elsewhere on the site which are a bit intimidating.

[RoyC]

Unfortunately there is no easy way to get to the pots. The glued on grilles have to be removed, the woofers pryed out of their hardened putty gaskets, and the rather nasty fiberglass removed from the cabinets before getting to those corroded little buggers.

The good news is that it is likely that your only problem is the pots. Your 1969 vintage AR-3a system has cloth surround woofers, so there is no deteriorated foam to replace. The crossover does not need to be replaced, though the tweeter capacitor is a very simple item to replace and would give you some "insurance" to do so. The very large woofer and midrange dual capacitor should be checked out, but it won't be the end of the world if you don't.

Much information regarding the pots has already been posted. If you need some assistance, feel free to email me through the forum.

Roy

[Guest tgw]

I basically did the procedure that Roy mentioned on my AR-3's that I obtained from a friend a few years ago. I replaced the grill cloth so I did not have to worry about saving it. Prying the woofers off the face of the cabinet took some effort, but they finally broke free. About 30 minutes with contact cleaner and WD-40 (some will tell you to use Craig, but I did not have any back then) and the pots worked fine. I used an ohm meter to monitor the effectiveness of the cleaning process. Connect across the leads that give a low reading when turned in one direction and a high reading when rotated in the opposite direction. As you clean the contacts you will see the resistance begin to smoothly change as you rotate the control.

For a little effort you will wind up with fully functional speakers with beautiful sound. I sell reproduction emblems on eBay (AR) historically correct and AR-3 and AR-3a emblems (not historically correct, but better than nothing or badly discolored originals).

[Guest mdavis]

I assume that the fiberglas packing goes back in, or is it replaced with something else?

Also, assuming I don't need the crossover replaced, can someone come up with a recommendation for the cap(s) that can be easily obtained. I don't need anything exotic, just decent functionality.

Thank you both for the help!

[Carlspeak]

You can get inexpensive electrolytic capacitors in 50 uF and 150 uF each as well as a decent PP (Solen) 6 uF cap from Parts Express.

Those are what I typically use for AR3a upgrades.

You'll also need to go thru the woofer hold to get at the rheostats in order to clean them. If they are badly corroded with green fuzz, you'll have to replace them. I put a post about a month back which explained what new, rheostats to get that are of better quallty and also rated at 15 ohms. These are hard to find.

Good luck with your upgrade.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[RoyC]

When removing the fiberglass put the contents of each cabinet in separate large plastic bags, as the amount used in each cabinet is important. (Your era cabinets have around 30 oz of fiberglass in each.) Make sure to do this work outdoors using a dust mask and gloves. The fiberglass from that vintage AR-3a produces a great deal of dust.

The primary advantage of using new material is ease of use and safety, though fiberglass will still have the performance edge with that era woofer. The use of polyester fill or Acousta Stuf will require approximately 50% less by weight.

Roy

[frankmarsi]

Hi, so you're the fellow who sells emblems? Have you thought about reproducing the AR-LST emblem? I need four of them, but perhaps others would need them also?

Please let me know.

Thanks, Frank Marsi

[johnieo]

>I assume that the fiberglas packing goes back in, or is it

>replaced with something else?

Roy and I have been studying this off-line, and concur with Ken Kantor's comment that one cannot use polyester or Acousta-Stuf as a drop-in replacement for fiberglass in speakers designed to use fiberglass. If one does change stuffing, one compromises the low frequency speaker performance.

It is suggested that one either return the original amount of fiberglass to each cabinet, or if extremely dusty (decomposed resin) replace it with the idential weight of new fiberglass. Matters not yellow or pink, but do remove any paper or aluminum foil backing. The early AR-3a with Alnico-magnet woofers used 28-to-30 oz of fiberglass per cabinet.

[Guest tgw]

I don't know what type of emblem the LST used, but I purchased a quantity of one inch square .020 brass plates and to them adhere the AR logo I reproduced on vinyl. These emblems are the exact size and style AR used on the 1,2,2x,3,4,4x models. You can attach these directly to the grill cloth with double faced tape, or to the original steel emblems.

[loudbuff]

I second that. Could use two AR-LST emblems.

>Hi, so you're the fellow who sells emblems? Have you thought

>about reproducing the AR-LST emblem? I need four of them, but

>perhaps others would need them also?

>Please let me know.

>Thanks, Frank Marsi

[Guest tgw]

The AR emblems I have fabricated are different than what is used on the LST.

[stan461]

>>I assume that the fiberglas packing goes back in, or is

>it

>>replaced with something else?

>

>Roy and I have been studying this off-line, and concur with

>Ken Kantor's comment that one cannot use polyester or

>Acousta-Stuf as a drop-in replacement for fiberglass in

>speakers designed to use fiberglass. If one does change

>stuffing, one compromises the low frequency speaker

>performance.

>

>It is suggested that one either return the original amount of

>fiberglass to each cabinet, or if extremely dusty (decomposed

>resin) replace it with the idential weight of new fiberglass.

>Matters not yellow or pink, but do remove any paper or

>aluminum foil backing. The early AR-3a with Alnico-magnet

>woofers used 28-to-30 oz of fiberglass per cabinet.

With all due respect, what scientific method have you used to determine that Acousta Stuf is not up to par. I am not being sarcastic or defensive. I am really curious and would like to know.

To disregard Acousta Stuf without any facts to back up your claim comes under the heading of free speech but has about as much value as stuffing an AR3a willy nilly with whatever.

I have 2 sets of AR3as. One set has Acousta Stuf. I have swapped them out many times and frankly I would have to open up a cabinet to know which is which.

[johnieo]

Greetings:

My experimental data is not with Acousta-Stuf but with trilobe polyester similar to that used by AR. I was not able to shift the fc peak to as low a frequency with this fiber as with fiberglass in either the AR-3a or AR-4x. Off hand, I don't remember the difference in fc for the two fibers in the AR-3a--it has been some time, but recently I did the same experiment with the AR-4x and found the fc was 60 Hz for polyester versus 55 for fiberglass.

When I explained my results to Ken Kantor, he indicated he had not been able to find any drop-in replacement for fiberglass in old speakers designed for fiberglass, except for one that was close, but it was not Acousta-Stuf.

Perhaps Ken may choose to elaborate on that comment.

[RoyC]

I have software capable of measuring woofer parameters in and out of the cabinet, and have used it to measure AR-3a response using a combination of damping materials and 3a woofer versions. Without exception, utilizing the same 3a woofer, fiberglass produces lower fc.

While I agree that the difference between the fc with Acousta Stuf at 41hz and that of fiberglass at 38hz is not likely to be heard with most recorded material, other parameters are also important. Different damping materials (and amounts) absorb higher frequencies differently. This could be a sonic factor with a speaker like the 3a where the large woofer contributes significantly to the midrange response.

Using fiberglass in the original amount in the AR-3a contributes to maintaining the original tonal character primarily because it was "voiced" when fiberglass was the damping material of choice. AR has already done the work for us, so we know the optimal amount of that material to use.

Acousta Stuf in the *proper amount* is probably an acceptable alternative for those who prefer not to handle fiberglass. I have experienced no other reason to use it however, and disagree with advertising claiming it to be "superior" to fiberglass (especially at $10 per lb!). It IS handy for those of us who will be back into our speaker cabinets again and again for various reasons:-).

Roy

[dynaco_dan]

Excellent information John and Roy, thank you.

[Guest Bret]

>Acousta Stuf in the *proper amount* is probably an acceptable alternative for those who prefer not to handle fiberglass.<

And that seems to be something more than the 12 ounces Acousta-Stuf would ordinarily spec for a cabinet of that size.

[RoyC]

>And that seems to be something more than the 12 ounces

>Acousta-Stuf would ordinarily spec for a cabinet of that

>size.

Hey Bret,

Using the measurements of the original fiberglass quantities as a basis of comparison, it appears that the optimal amount of Acousta Stuf is 12oz to 14oz. Deep bass measures about the same, but differences can be heard in the upper bass and lower midrange as more is added.

Roy