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Guest vinjah

Design questions and impedance on AR 94sx

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Guest vinjah

Apologies in advance as I know this forum is for classic speakers, which I do not believe the 94sx qualify for, but I'm having a hard time finding knowledgeable folks.

Earlier I had posted on a rebuild project where I had the two (x2) drivers' foam surround redone, and then set off on an ambitious crossover refurb. I took a design from the net where a model 94 was rebuilt, however the xover on that model is quite a bit different than my SX revision.

My basic questions are on specs (as I simulate the crossover circuits):

1. Does anyone know what the impedance of these speakers are (the whole cabinet)?

1b. Is there a simple way to determine impedance of the individual drivers?

2. As each cabinet has two 8" drivers, one being a woof, one a mid-woof, are these designs typically sending the same freq ranges to each drivers with different cutoffs, or generally a tuned signal to each driver?

Any thoughts are appreciated. I know 17 years isn't too old for speakers on this list (!), but hopefully it's food for discussion.

Thanks in advance- Vijoy

San Francisco, CA, USA

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>Earlier I had posted on a rebuild project where I had the two

>(x2) drivers' foam surround redone, and then set off on an

>ambitious crossover refurb. I took a design from the net

>where a model 94 was rebuilt, however the xover on that model

>is quite a bit different than my SX revision.

>

>My basic questions are on specs (as I simulate the crossover

>circuits):

Vijoy, why are you rebuilding the xovers in your 94sx's?

It's highly likely the original xovers are performing well. Further, when re-building, most folks replace the caps. The coils really don't wear out.

In answer to one of your questions, AR would often design their xovers to do more than just frequency separation. They would use the networks to “shape” frequencies to compensate for non-liner drivers (raw speakers are anything but linear) and cabinets.

Hope this helps...

Jerry

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Guest vinjah

>Vijoy, why are you rebuilding the xovers in your 94sx's?

>

>It's highly likely the original xovers are performing well.

>Further, when re-building, most folks replace the caps. The

>coils really don't wear out.

>

>In answer to one of your questions, AR would often design

>their xovers to do more than just frequency separation. They

>would use the networks to “shape” frequencies to compensate

>for non-liner drivers (raw speakers are anything but linear)

>and cabinets.

>

>Hope this helps...

>

>Jerry

My understanding is that 18 years (purchased summer 1988) is long enough for caps to drift from their original spec. I'm only replacing cap and resistors, keeping the inductor coil.

Your comment makes me lean toward keeping the original design, though since I have new and old design (with new components) each connected to one speaker, I have the luxury of doing some listening tests.

Thanks for your comments, and thanks Rlowe for the specs! Still impressed with AR even that late in their corporate lifetime.

regards,

vijoy

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Guest Bret

>My understanding is that 18 years (purchased summer 1988) is long enough for caps to drift from their original spec. I'm only replacing cap and resistors, keeping the inductor coil.<

It's almost certain that the caps are "drifted" and you will do well to replace them. There are some specs from the original caps that you will almost certainly not be able to match exactly and the effect on the crossover will be more subtle than the deteriorated cap.

Resistors . . . well, it depends. I've had some crumble on me when I touched them. That's not good. So I've taken to replacing them with non-inductive type resistors, but it's probably not really necessary.

Don't spend a ton on caps, but DO spend some money on the tweeter cap. I've had very good results (not on your model) "by-passing" (putting a small value cap in parallel with a much larger cap).

That, too, creates possible problems - but it eliminates others. . . Fact is, we can't go back exactly. Replacing the caps can only help and replacing the resistors can't hurt.

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Guest vinjah

Thanks for your reply Bret. In fact, I'm using quite a bit of that by-passing technique based on the work I found here:

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

The accuracy of the speaker has noticably gone up with the new crossover though the lower-mid are reduced (the surrounds were re-foamed and tweeters replaced as well). These speakers are heavy on the bass, which can be both good and bad.

If anybody's interested in seeing the new design circuit diagram/photo I'd be happy to share.

-vijoy

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Guest Sanjeev

Hi,

I may know few details, as I recently acquired AR 94 Sx. But one of them need some work. Yet to figure out.

The impedance is 4 ohms nominal.

Thank you.

Sanjeev

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Guest hilltroll67

>Hi,

>

>I may know few details, as I recently acquired AR 94 Sx. But

>one of them need some work. Yet to figure out.

>

There is an article (by me) on this subject in the current (December) issue of Affordable$$Audio e-magazine which may be of some interest to you, if of no practical use. It is downloadable (free) in pdf format from:

www.affordableaudio.org.

Note: Further testing has determined that the Dayton tweeter mentioned in passing in the article is *not* a good sonic replacement for the stock tweeter.

Bob

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Like Vijoy, I'm considering rebuilding xovers on my 94sx's. Looks like there is some disagreement between Vinjah and what I see from article at tnt-audio -- see the To Do section in www.tnt-audio.com/clinica/ar94rebuild_e.html

The article in on a rebuild of the AR94 and NOT the "sx" so I'm looking for some help in picking hardware for the sx's and my vocational training in electricity/electronics in high school 40 years ago leads me to lean toward replacing/updating the caps and wires on the original xover board I have here. These posts are pretty old but I'm hoping someone will provide specs from their successful rebuild of the 94sx.

Thanks guys,

MikeF

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Like Vijoy, I'm considering rebuilding xovers on my 94sx's. Looks like there is some disagreement between Vinjah and what I see from article at tnt-audio -- see the To Do section in www.tnt-audio.com/clinica/ar94rebuild_e.html

The article in on a rebuild of the AR94 and NOT the "sx" so I'm looking for some help in picking hardware for the sx's and my vocational training in electricity/electronics in high school 40 years ago leads me to lean toward replacing/updating the caps and wires on the original xover board I have here. These posts are pretty old but I'm hoping someone will provide specs from their successful rebuild of the 94sx.

Thanks guys,

MikeF

Hi Mike, I know this is an old post but I have two AR94Sx that are going to need their caps replaced. Did you ever replace yours and with what and what sound results? Thanks, -Joseph

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>Hi,

>

>I may know few details, as I recently acquired AR 94 Sx. But

>one of them need some work. Yet to figure out.

>

There is an article (by me) on this subject in the current (December) issue of Affordable$$Audio e-magazine which may be of some interest to you, if of no practical use. It is downloadable (free) in pdf format from:

www.affordableaudio.org.

Note: Further testing has determined that the Dayton tweeter mentioned in passing in the article is *not* a good sonic replacement for the stock tweeter.

Bob

I know this is an old post but I have two AR94Sx and I did do the replacement of the two stock/working tweeters with two Daytons (the earlier tweeter version to the one mentioned in your article) and I think with good results at all sound volumes...livened it up, I think. The old stock tweeters were harsh as some have said and it was the first time I experienced ear fatigue. Would you elaborate on what you meant by "not" a good sonic replacement re the Dayton tweeters? If there's an even better choice then I'll start saving dough if I know what model to pursue. Thanks, -Joseph

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