AR94's - to refoam or to replace, tis the question

[Guest westarch]

Hey guys,

I've got a pair of Acoustic Research 94 loudspeakers that I've had since college. A few weeks ago, I noticed that the bass out of one was scratchy, as though it had been blown. I didn't think that was possible at moderate levels, so I pulled up the cloth surround to check it out. Turns out the foam had disintegrated on the mid-range and the tweeter was dented. The woofer doesn't sound like it's blown (no scratches when gently pushed) but I'm sure the foam surround isn't as good as it used to be.

Thinking a fix would be too much effort and newer speakers would be better, I thought I should sell the speakers. I turned to the web, and this is the first site that popped up on Google. Since then I've been reading various opinions on the AR portion of the site and learning about the history of these speakers. Not only has the information here made me realize I shouldn't sell the speakers, but now I'm convinced I can easily fix them up with your collective help. Mark, thanks for creating this site and keeping an archive of all the discussions!

So my question is this - it seems like all three drivers need work. What will sound better - to repair and re-foam or to replace? Let's take cost out of the equation since either option is less than a set of new loudspeakers. What do I do to make these speakers sound as good as I can get?

I look forward to your advice.

-Doug West

[Carlspeak]

Doug, I've worked on many of the loudspeaker brands and models listed in this site's discussion area. Visit my web site to learn more about my services. Contact me directly if you need further information and a formal quote.

http://www.classicloudspeakerservices.com

e-mail ..... carlspeak@aol.com

Carl

Carl's Custom Loudspeakers

[Guest Bret]

>What will sound better - to repair and re-foam or to replace?<

If the foam is the only problem, refoam and either do it with an eye-out for everything else that could possibly be wrong or get someone who will check to see that everything else is right to do it for you. I opt for letting someone else do it, but I'm not convinced that "my way" is the only way. Choose your refoamer with care if you let someone else do it. They don't all do the same quality job.

If you liked the way the speaker sounded, which is the way the designer intended and you used to enjoy, refoaming is infinitely preferable to replacing the drivers. Everything from the size of the cabinet to the amount of stuffing in the box to the values in the crossover components work together with the original specs of the drivers to produce that nice sound. Goof around with the drivers and you goof-up multiple functional parameters of the design. Oh, sure, you could compensate by redesigning the crossover and adjusting this, that, or the other thing. . . but you'd probably be better-off starting from scratch and just building an entirely new speaker.

You need to check the caps - heck, you need to replace the caps. They are old. They are probably in some stage of going-bad, or already bad. This is easy and can be relatively cheap.

You need to replace the resistors, if there are any. Well, you probably don't really need to, but while you're doing the rest of it, splurge on $1.40-worth (or whatever) of resistors, just in case.

Don't change the inductors unless they are damaged.

You need to replace everything with brand-new exact replacements for what comes out of them. The bad news? You can't. Why?

The caps aren't made anymore, and we don't have a data sheet on them. If you will look through the AR section you will find a *lot* of discussion about capacitors beginning with the very oldest message available. There are as many different opinions as their are possibilities and I suggest you pick one and "go with it." If someone has the perfect solution, thus-far they haven't told the rest of us.

In the library section of the forum is a tale of refurbishing AR-94s. You might agree or disagree with some of what was done, but you should probably read it to see what someone else's experience was. Personally, I'd have had a big problem with the surround change they did.

http://www.classicspeakerpages.net/ar/ar-9/ar-94/AR94.htm

Good luck, keep us up-to-date, and as long as you are doing a refurbish instead of a tweak, mod, or "upgrade" you will probably get better responses in the AR section of the forum.

Bret

[Guest westarch]

Bret,

Thanks for your honest and useful advice. I was starting to feel overwhelmed thinking about all the options for driver replacement instead of re-foaming. And Dejan's page is both helpful and compelling. I am determined to have the drivers re-foamed.

The world of crossovers seems very confusing, however. Any suggestions for how to best wade through it? I've found some crossover discussions on the AR pages, but they're mostly for the AR-9 or older models.

Also, based on some of the miscellaneous pictures I've seen of other AR-9_ owners, my speakers seem to be constructed with newer, perhaps less expensive components. The connectors on the bottom, for example, are the inexpensive basic spring-loaded clip type. And there are no stickers on the bottom of the speakers with a model number and manufacturer information. But all the parts are stamped AR... Was this a cost-savings method employed in the early 80's that isn't well-documented?

Once I've gotten the drivers fixed, I'll upgrade the crossovers, as you suggested. I'll keep researching the crossover options... Any advice is appreciated!

-Doug.

[Guest Bret]

>I've found some crossover discussions on the AR pages, but they're mostly for the AR-9 or older models.<

The entire "9" series is close-enough in vintage that the principles applied to restoring one would be valid for them all.

The only part of the crossover that's likely bad (or going bad) are the capacitors. All you can really do is "pick your poison" and replace them while the drivers are being refoamed.

The positions various people have taken on capacitors is:

1) Don't replace them, even if they are "iffy"

2) Test them all and only replace the ones that are out-of-spec

3) Replace them with "like-kind" caps (low ESR NPEs)

4) Replace them with a combination of poly, NPE, film and foil

5) Replace them with inexpensive polys for good signal and stability

6) Replace them with expensive polys for a "cleaner signal"

Some say it's all in my and others' imaginations, but I tend to like #6 best, although I freely admit I haven't tried #2 and #4 and I'm curious about #4 as outlined in the article you've already read. The only one I tried and clearly disagree with is #1.

Every idea has some technical merit; and every idea has a rationale; and every idea has shortcomings.

Can you be real specific about what it is in the crossover that is giving you a concern?

Bret

[Guest Bret]

Before you do anything about the crossover you should read:

http://www.classicspeakerpages.net/dc/dcbo...3&topic_id=4059

You'll see my frustration, others' comments about my frustration, get the best advice from an AR engineer, a technically astute AR fan, and a couple of "commoners" like me just looking for "the answer." It's only been recently that I've understood the magnetude of the problem. It hasn't helped me solve the problem, though.

The sad thing is that we continue to chase our tails. I'm working-on resolving that, but it isn't going to happen today.

Bret

[Guest westarch]

Bret,

You keep sending me great links. Thanks!

-Doug.

[Guest David in MA]

>Before you do anything about the crossover you should read:

>

>http://www.classicspeakerpages.net/dc/dcbo...3&topic_id=4059

>

Thanks for the link to this topic. I'm in the process of digesting materials on crossover circuits.

>You'll see my frustration, others' comments about my

>frustration, get the best advice from an AR engineer, a

>technically astute AR fan, and a couple of "commoners" like me

>just looking for "the answer." It's only been recently that

>I've understood the magnetude of the problem. It hasn't

>helped me solve the problem, though.

I see what you mean. Reading that topic made things more confusing. I'm an electrical engineer by trade (radar signal processing) and I thought a cap is a cap is a cap. Obviousely this is not true. I'll need to read more on this topic.

>The sad thing is that we continue to chase our tails. I'm

>working-on resolving that, but it isn't going to happen

>today.

Yep...it gives us something to do with our life, heh?

Later,

[Guest Bret]

Read more on this topic? Hey, we gotcha covered right here.

http://www.classicspeakerpages.net/dc/dcbo...e=&topic_page=1

It's more than a little embarrassing to have your educational process open for all the world to see, but then. . .

everybody's got something to hide, except for me and my monkey.

Bret