AR9 crossover question

[Guest henningsoilen]

Hello everyone and thanks for a great forum.

After a major repair of both my AR9's (replacing 1 tweeter, 2 UMR's and refoaming of 4 bases and 1 LMR. One of my daughters abusing them, probably even with some lousy crap music) I noticed that the UMR in 1 speaker delivered no sound. After checking the crossover filter I found that 1 capasitor in paralell with the UMR with value 8uf 100v bipolar had a short.

When replacing this I have a choice of selecting a polypropylen or something called a Mcap RXF (Radial Xtra Flat) or even somthing called a supreme version. The latter priced at $60, the first two in the range of $10 to $20.

What would be your choice?

Perhaps none of these and only the original capasitor from the AR9 crossover?

Would you replace with the same capasitor in the other speaker even if that one is OK?

Can I use the speaker in the meatime while waiting for the new capasitor? (low power of course)

Best regards

Henning

[Carlspeak]

I suggest you go with your latter, less expensive choice for the parallel cap and match it in the other speaker for consistency's sake.

Don't recommend playing the loudspeaker until you get them back in working order.

Do recommend locking up your stereo until YOU use it.

[Diamonds&Rust]

Would you replace with the same capasitor in the other speaker even if that one is OK?

Henning,

There are a lot of capacitors in the AR9, I know. Replace them ALL. You don't have to get fancy, you don't have to go expensive, but replace them ALL.

The drivers you may save will repay you for the expense. Running mine with bad caps screwed-up my upper midranges.

Do not play the speakers until you get them fixed. Fortunately, the AR9 crossover is pretty easy to work on through the woofer holes.

Replace the caps! All of them. Soon. Drivers are scarce and getting rare.

I don't have a specific capacitor suggestion for you. Find something affordable and replace them all. Inexpensive capacitor testers are useless, don't bother. They may tell you that a bad one is bad, but they are also likely to tell you a bad one is good. Just replace the capacitors.

Bret

[kkc]

I have AR94 speakers and recently upgraded all the caps inside. The sound difference was amazing. You need not buy expensive caps. The ones I used are Clarity SA caps - available on the net at places such as www.e-speakers. The Clarity SA are used in B&W speakers. A good balance between performance and price.

If you haven't done so already, then you should replace all old caps so that your signal path is clean. I also used thick OFC wiring and air-cored conductors. Check that resistance in each signal path is still consistent with pre-upgrade values or you might find you lose or gain power in one or more speakers.

[Guest henningsoilen]

Thank you guys for comments and suggestions.

At least for now, I ended up buying new polyprop caps (some brand made in france) for the tweeters and the UMR's. I am in the process of replacing them. The larger ones for the bases I am reluctant to replace. The LMR iones are on hold for now, that is, if you guys don't insist. I'll be back with some more comments after playing some music.

Henning

[kkc]

So you want great sound from the tweeters and umrs but not the woofers.....! If you intend to work on the XOs you may as well do all the caps and the wiring. The alternative is that you re-open the speakers again at a later stage - each time you touch the XOs you risk stressing solders, connections etc. Also as you replace with better quality caps, you may find that the new caps are physically much larger requiring you to re-think the layout on the board.

[Guest John Gisslen]

Hello everyone and thanks for a great forum.

After a major repair of both my AR9's (replacing 1 tweeter, 2 UMR's and refoaming of 4 bases and 1 LMR. One of my daughters abusing them, probably even with some lousy crap music) I noticed that the UMR in 1 speaker delivered no sound. After checking the crossover filter I found that 1 capasitor in paralell with the UMR with value 8uf 100v bipolar had a short.

When replacing this I have a choice of selecting a polypropylen or something called a Mcap RXF (Radial Xtra Flat) or even somthing called a supreme version. The latter priced at $60, the first two in the range of $10 to $20.

What would be your choice?

Perhaps none of these and only the original capasitor from the AR9 crossover?

Would you replace with the same capasitor in the other speaker even if that one is OK?

Can I use the speaker in the meatime while waiting for the new capasitor? (low power of course)

Best regards

Henning

I have 2 pair of ar-9's, i replaced all internal wiring with 12 gauge wire....huge difference! Also, i suggest drawing a diagram when doing this, and replacing the binding posts. (they are mounted on the back panel, and if you don't use the bi-wire, 4 terminal configuration, just install 2) I used Neutrik Speakon connectors, which you can find at any pro audio shop, or online. CRITICAL NOTE ! ! ! ...... Notice how the binding posts are on a recessed part of the back of the cabinet that is only 3/16ths of an inch thick!!!! I don't know anyone who would build a speaker cabinet with that thin of a material. To fix this, just find some 3/4 inch, maybe it's 7/16 inch particle board, and cut out 3X5" or whatever the size of the recess is and glue them in. I used liquid nails subfloor adhesive. I did this while replacing the binding posts. Also, keep in mind a speaker cabinet is a finely tuned instrument which is highly dependent on the cubic volume of air inside. Be careful when replacing capacitors, because if they are not identical size, you will be changing the volume of air inside the cabinet. These are AWESOME SPEAKERS, and are worth the time it takes to modify them, Acoustic Research did a great job except for 3 major F#%* Ups. #1: Too small of gauge interior wiring. #2: The thin material used where the binding posts mount. #3: The cheap attenuation switches on the front panel. I've described how i fixed the first two, the third fix is as follows: Pull a woofer, reach up and pull the 4 wires off the switch board inside the cabinet. note where the wires go, and bypass the swiches. I did this mod when i replaced the interior wiring. If you decide to leave the switches in place (I did) Remove the 3 black metal trim rings around each switch on the exterior of the cabinet. Note how those 3 switches are countersunk. This is the other part of the cabinet that is weak(too thin of material). I just filled each of the 3 recesses with JB weld, and pushed the trim rings back in place.

This took me about 25 hours per speaker. I got the 12 gauge wire from radio shack for $5.00 per spool.

I used one red and one black spool per speaker. Those 3 switches on the front of the cabinet are not neccessary, buy a high quality pro audio equalizer if you want to customize your equalization slope. (I have a 31 band 2 channel top of the line DBX equalizer) Feel free to email me with any ?'s johngisslen@yahoo.com Sincerely, John Gisslen

[kkc]

John, I take your point about disturbing the internal volume through the use of physically larger caps. Are you then suggesting that not replacing electrolytic caps with audiophile caps (i.e. volume is preserved) will have a great impact then using audiophile caps?

In which areas would volume reduction affect the playback?

BTW, how have you setup your four speakers - surround? Or will you sell one pair....

Thanks, kkc.

[Guest John Gisslen]

John, I take your point about disturbing the internal volume through the use of physically larger caps. Are you then suggesting that not replacing electrolytic caps with audiophile caps (i.e. volume is preserved) will have a great impact then using audiophile caps?

In which areas would volume reduction affect the playback?

BTW, how have you setup your four speakers - surround? Or will you sell one pair....

Thanks, kkc.

Thanks for your interest. I am not an engineer, but i have built speakers in the past, and i know that the cabinet needs to be "built around" the drivers. There is a formula for this, and what i did to build my bass cabinets, was to contact electro voice, and they actually sent me detailed plans to build a tuned enclosure for their EV180B 18 inch woofer. The AR-9 is the best sounding consumer audio speaker i have ever heard,(i actually have three pair....still working on the third), and i'm sorry to say that i will continue buying them and can't see myself ever selling a pair. When i rewired the internal wiring with larger diameter wire, i actually shaved some of the wooden cross member support off to compensate for the slightly reduced air volume caused by the larger wire. I just know that if you change the volume of air, you change the tuning of the cabinet....I'm not sure in what areas, but performance will be changed. I love the way these babies sound, so i just try to keep them as original as possible. I haven't upgraded the caps in my crossovers, but i do recommend it if you can afford the money and the time. I plan on doing it, and when i do, i will calculate the cubic volume of the old caps, and the new ones, and try to compensate by adding or subtracting internal mass. I am using 5 ar9's (front, rear, center) and a 2700 watt sunfire subwoofer. iam pumping 2300 watts into my 9's. I know larry at vintage_ar (an ebay store) will be selling a fully restored set of 9's for about $1600.00 soon. His email is LJLAGACE@aol.com Have fun and keep rockin'........John

[kkc]

John, there is another solution that occurs to me. Keep the old XO inside the enclosure but disconnected and build the new XO outside the AR9 - that way you don't have to shave anything off potentially weakening the rigidity.

Thanks for the contact details.

Rgds, kkc.

[Diamonds&Rust]

John, there is another solution that occurs to me. Keep the old XO inside the enclosure but disconnected and build the new XO outside the AR9 - that way you don't have to shave anything off potentially weakening the rigidity.

Thanks for the contact details.

Rgds, kkc.

The best solution is to realize that a few cubic inches out of a 13,000 (rounding) cubic inch enclosure will make no difference and that the brace that was shaved down was probably not compensated for with a slightly larger box.

Neither will increasing the internal wiring to 12 gauge or 8 gauge to the tweeters improve anything.

Do NOT disable the switches, buy new ones. Do NOT use expensive audiophile capacitors as they are a waste of your money. DO use new polypropylene capacitors, but which ones don't much matter. If you find them too bright, add 1/10th to 3/10ths Ohm of resistance just before the capacitor. Don't "improve" on the design, it wasn't needed then and isn't now. Do NOT spend a fortune restoring those. Do NOT replace the inductors.

The only place where "space" is going to be an issue is if you try to replace the woofer capacitors with poly caps. If you do that, you'll need another room for the crossover. It's too expensive. You could buy some new B&Von SwitzerWs cheaper than all those poly capacitors.

Do enjoy them. Properly fixed they can do some amazing things. "Properly" isn't necessarily expensive.

Bret

[johnieo]

In which areas would volume reduction affect the playback?

In no areas.

This business of capacitors altering cabinet volume in a measurable way is nonsense. Consider the AR-3a. Its internal volume is 42,000 cc. The original dual capacitor (150, 50 uF) was 5"x3"x2" or 500 cc. AR replaced that with two NP electrolytic caps of 80 cc each. Did they alter the cabinet volume to account for this 340 cc (0.81%) increase in internal volume? No! AR also added some extra internal bracing for a couple of their famous live/recorded sessions - again within stock cabinets.

Same for wire size. If a larger wire size were needed, AR would have used it. Ditto for CDA-101 (formerly OFHC) copper wire. Its resistance differences for lengths used inside the cabinet is infinitesimal. This could lead to a discussion of $15,000 cables. Let's not go there :-)

Cheers,

[Diamonds&Rust]

I haven't upgraded the caps in my crossovers, but i do recommend it if you can afford the money and the time. I plan on doing it, and when i do, i will calculate the cubic volume of the old caps, and the new ones, and try to compensate by adding or subtracting internal mass.

John -

You know... this is a hobby and so maybe one day you will (or already have) found some audio nirvana that I'll never experience. Far be it from me (or anyone here) to "tell you what to do." If I come across that way, we'll have to get-together for a beer or a Valium or whatever suits you and it'll be easier to hear my whole "tone" is really more "plaintiff" than "lecturer" sounding.

I'm skipping a lot of "how we got here" and "bottom-lining" not out of conceit, but for lack of time. All the ugly details are in very old postings to this forum.

Everyone (to my knowledge) here who has done an AR9 or AR90 restoration has found at least one, more usually two, "destroyed" capacitors in the upper cabinet. If you search hard enough, you'll even find photos of some of the black with red end-cap Callins capacitors sitting in mountains of old hot glue, which may be part of the problem. I'm not talking about "Gee, this capacitor could be better," but "Gee, this 8uF cap is reading 24uF," meaning that it isn't doing its job, at all. What has been almost universally found to be true is that one or the other of the midrange units is playing too loudly and the other isn't playing much at all.

This isn't anything you can "just hear." You need a reference. Once you do the recapping on one speaker, suddenly it all becomes clearer and you think, "Wow!" and then you hurry and do the next one. Then you listen to a pair and think, "Ohmygosh... I can't believe I thought they sounded good the other way." Then you get back on the internet and order the caps for the other ones. Only after you have done that can you really assess if your drivers are all still good.

If money is an object, I will tell you from experience that even new inexpensive NPEs (which I don't like) will improve things dramatically by just making the crossover work the way it should - sending the right signals to the right drivers in the right proportions.

Although some will argue that you cannot hear the difference in various capacitors, except maybe by type, I don't believe that's true. I say, "believe," because I can't prove that I hear differences in them, of course. But I absolutely can tell you that without doing fussbudget-like A/B quick comparisons -> that is, if I were just to walk into a room with speakers playing <- there's no way that I could tell you what capacitor is in the speakers I'm listening to. No way. None. Can't be done. Therefore, I concluded, that spending mega-bucks on audiophile capacitors was a waste of money if the *goal* was to have the speakers "just sound right" and be able to enjoy them.

I have hundreds of dollars worth of capacitors in my AR9s. I was thinking the whole, "If these are better, I'll use them to have the best sound I can get," progression. Wrong. Ultimately it doesn't matter. Spending Mega-Bucks feeding a modern Mega-Buck tweeter *may* have some validity, I don't know, but spending Mega-Bucks feeding the 30 year old drivers in an AR9 is not helping. Feeding them properly (the right signal) *is* worth doing and the results are great.

I was listening to fried upper midrange drivers and didn't know it - that's *with* the mega-dollar capacitors in the cabinet. How does something like that happen? Simple: With no frame of reference you don't *know* what you are missing, it sounds better so you conclude that it sounds "good". Well, not-necessarily.

How did my upper midrange drivers get fried? (O.k., they weren't "fried" but they weren't good, either) Many years of high volume play (500w/channel amp; 95db levels) with two bad capacitors on each of them, sending them signals that belonged in the lower midrange driver. (not obvious until a cap change) I suspect I just cooked the ferrofluid right out of them. With that Sunfire amp (I was using a Sunfire on mine for a while, too) you may be doing the same thing and just not know it.

If I feel like that about capacitors, why not use currently available NPEs then? Because they aren't very good and they, too, will age and need to be replaced in another 7-10 years. Using poly caps, as far as we know, it won't ever have to be done again. Termites will eat the cabinets first. Poly 80uF and 470uF and 2500uF capacitors are going to be really, really expensive to "build-up." From research done, and more than one person's practical experience, you *may* leave these three big aluminum cans alone. If you do that and use poly caps elsewhere you probably *will* need to put 1/10th to 3/10th Ohm resistors on the poly caps.

I say probably because that's a solution pointed-to by a composite of experiences people here have had. Nobody has actually done it in a pair of 9s (to my knowledge). It's a guess. I've wanted to get my hands on a cheap pair of 9s to use as a test-bed, but none have come my way, yet, and I can't keep my 9s torn apart, nor would I pull the expensive caps out and replace them with cheap caps. The thought of "wasting" that much money just... well, you know.

So... try recapping them inexpensively and either adding resistors or not. You'll like some combination a lot more than leaving even one bad capacitor in the speakers. All of the little black capacitors with the red end-caps are to be considered suspect and I would lay a fair bet that several of them are bad. Very bad. Not "non-audiophile" bad, but the kind of bad that a flat tire is bad or an air conditioner without refrigerant is bad or a television with a burned-out picture tube is bad.

The reason you might not want to by-pass all those switches in the attenuators is simple: Every time I almost did it, something stopped me. Eventually I discovered a problem with my room and speaker placement which meant I needed to use them. I was very happy to have them. Whatever improvement I could have made by removing the attenuators was far less of a problem than not being able to adjust them to the room would have been.

Your mileage may vary, but I seriously doubt it. (but I've seriously doubted things before, and was wrong)

Keep us up-to-date with what you've done, what you think about it, and how it's all coming. You're adding to the global knowledge base and we appreciate it.

[kkc]

Can anyone explain what sort of impact the 80uF, 470uF and 2500uF capacitors are going to exert on an amplifier at various frequencies? I am not at all up to speed on crossover circuits, but these are seriously large caps. Here's a private e-mail I had with someone who makes a living fixing speakers:

"The AR9 as standard have a pair of 11" x 4 ohm woofers in parallel and combined with the awful crossover design they present a very low impedance to the amp at low bass frequencies. The crossovers use high resistance inductor coils which waste a lot of power thus making the speaker insensitive.

To eliminate the problems I connected the bass drivers in series and totally redesigned the crossovers and fitted better new mid/high F drivers.

You'd be far better off making your own speakers with modern drivers, all of which are far better than anything originally fitted to AR9."

Any comments anyone...

[roundhome]

Can anyone explain what sort of impact the 80uF, 470uF and 2500uF capacitors are going to exert on an amplifier at various frequencies? I am not at all up to speed on crossover circuits, but these are seriously large caps. Here's a private e-mail I had with someone who makes a living fixing speakers:

"The AR9 as standard have a pair of 11" x 4 ohm woofers in parallel and combined with the awful crossover design they present a very low impedance to the amp at low bass frequencies. The crossovers use high resistance inductor coils which waste a lot of power thus making the speaker insensitive.

To eliminate the problems I connected the bass drivers in series and totally redesigned the crossovers and fitted better new mid/high F drivers.

You'd be far better off making your own speakers with modern drivers, all of which are far better than anything originally fitted to AR9."

Any comments anyone...

Ya tell him to get a better amp

[RoyC]

Ya tell him to get a better amp

I agree with roundhome.

He should stick to "fixing" speakers...His comment regarding inductor resistance (which is something that is calculated into a design) implies that he is rather clueless in the realm of speaker design. Further, whatever he ended up with is no longer an AR-9, so there is no point in discussing it in this forum.

Roy

[Diamonds&Rust]

Any comments anyone...

Yeah. He got enough totally wrong that discussing the merits of what he got right isn't worth doing.

About being better off building your own? That's going to depend on your skills and budget. The place to start that endeavor would not be with an AR9 cabinet. You can't just "shove better drivers and a new crossover" into those holes and expect to end-up with anything good.

[rrcrain]

Can anyone explain what sort of impact the 80uF, 470uF and 2500uF capacitors are going to exert on an amplifier at various frequencies? I am not at all up to speed on crossover circuits, but these are seriously large caps. Here's a private e-mail I had with someone who makes a living fixing speakers:

"The AR9 as standard have a pair of 11" x 4 ohm woofers in parallel and combined with the awful crossover design they present a very low impedance to the amp at low bass frequencies. The crossovers use high resistance inductor coils which waste a lot of power thus making the speaker insensitive.

To eliminate the problems I connected the bass drivers in series and totally redesigned the crossovers and fitted better new mid/high F drivers.

You'd be far better off making your own speakers with modern drivers, all of which are far better than anything originally fitted to AR9."

Any comments anyone...

I have comments, but none good, or repeatable in the forum.

Being polite, it's obvious this person doesn't understand speaker design, the differences in efficiency between acoustic suspension and ... whats the other...vented cabint?

He/she doesn't have a decent amp capable of driving an AR9 properly. Probably has a toy Realistic amp.

If this person understood crossover design, they wouldn't be asking "what's this cap for?" but instead, would be explaining how this or that cap, if bad or altered can effect the circuit. As for the inductors in the AR9/90, they aren't "perfect lay" or "Litz" but they are excellent quality of a good gauge for the current involved.

In a nutshell, be polite, nod on occasion, and then remember all of their advise as bad.

[Guest John Gisslen]

John -

Thank you for your wisdom, time, and patience. I will do this mod on my 3rd pair of 9's, and let you know the results of the comparative sound test. As far as the switches go...... the quality was questionable, so after much hemming and hawing, i decided to bypass them, and bought the best pro audio equalizer i could afford. I thought that it would be in my signal's best interests. I also have much more control of the whole frequency range. Thanks again, (I am restoring a pair of 9LS's, and will also report on my side by side sound comparison to 9's). John

You know... this is a hobby and so maybe one day you will (or already have) found some audio nirvana that I'll never experience. Far be it from me (or anyone here) to "tell you what to do." If I come across that way, we'll have to get-together for a beer or a Valium or whatever suits you and it'll be easier to hear my whole "tone" is really more "plaintiff" than "lecturer" sounding.

I'm skipping a lot of "how we got here" and "bottom-lining" not out of conceit, but for lack of time. All the ugly details are in very old postings to this forum.

Everyone (to my knowledge) here who has done an AR9 or AR90 restoration has found at least one, more usually two, "destroyed" capacitors in the upper cabinet. If you search hard enough, you'll even find photos of some of the black with red end-cap Callins capacitors sitting in mountains of old hot glue, which may be part of the problem. I'm not talking about "Gee, this capacitor could be better," but "Gee, this 8uF cap is reading 24uF," meaning that it isn't doing its job, at all. What has been almost universally found to be true is that one or the other of the midrange units is playing too loudly and the other isn't playing much at all.

This isn't anything you can "just hear." You need a reference. Once you do the recapping on one speaker, suddenly it all becomes clearer and you think, "Wow!" and then you hurry and do the next one. Then you listen to a pair and think, "Ohmygosh... I can't believe I thought they sounded good the other way." Then you get back on the internet and order the caps for the other ones. Only after you have done that can you really assess if your drivers are all still good.

If money is an object, I will tell you from experience that even new inexpensive NPEs (which I don't like) will improve things dramatically by just making the crossover work the way it should - sending the right signals to the right drivers in the right proportions.

Although some will argue that you cannot hear the difference in various capacitors, except maybe by type, I don't believe that's true. I say, "believe," because I can't prove that I hear differences in them, of course. But I absolutely can tell you that without doing fussbudget-like A/B quick comparisons -> that is, if I were just to walk into a room with speakers playing <- there's no way that I could tell you what capacitor is in the speakers I'm listening to. No way. None. Can't be done. Therefore, I concluded, that spending mega-bucks on audiophile capacitors was a waste of money if the *goal* was to have the speakers "just sound right" and be able to enjoy them.

I have hundreds of dollars worth of capacitors in my AR9s. I was thinking the whole, "If these are better, I'll use them to have the best sound I can get," progression. Wrong. Ultimately it doesn't matter. Spending Mega-Bucks feeding a modern Mega-Buck tweeter *may* have some validity, I don't know, but spending Mega-Bucks feeding the 30 year old drivers in an AR9 is not helping. Feeding them properly (the right signal) *is* worth doing and the results are great.

I was listening to fried upper midrange drivers and didn't know it - that's *with* the mega-dollar capacitors in the cabinet. How does something like that happen? Simple: With no frame of reference you don't *know* what you are missing, it sounds better so you conclude that it sounds "good". Well, not-necessarily.

How did my upper midrange drivers get fried? (O.k., they weren't "fried" but they weren't good, either) Many years of high volume play (500w/channel amp; 95db levels) with two bad capacitors on each of them, sending them signals that belonged in the lower midrange driver. (not obvious until a cap change) I suspect I just cooked the ferrofluid right out of them. With that Sunfire amp (I was using a Sunfire on mine for a while, too) you may be doing the same thing and just not know it.

If I feel like that about capacitors, why not use currently available NPEs then? Because they aren't very good and they, too, will age and need to be replaced in another 7-10 years. Using poly caps, as far as we know, it won't ever have to be done again. Termites will eat the cabinets first. Poly 80uF and 470uF and 2500uF capacitors are going to be really, really expensive to "build-up." From research done, and more than one person's practical experience, you *may* leave these three big aluminum cans alone. If you do that and use poly caps elsewhere you probably *will* need to put 1/10th to 3/10th Ohm resistors on the poly caps.

I say probably because that's a solution pointed-to by a composite of experiences people here have had. Nobody has actually done it in a pair of 9s (to my knowledge). It's a guess. I've wanted to get my hands on a cheap pair of 9s to use as a test-bed, but none have come my way, yet, and I can't keep my 9s torn apart, nor would I pull the expensive caps out and replace them with cheap caps. The thought of "wasting" that much money just... well, you know.

So... try recapping them inexpensively and either adding resistors or not. You'll like some combination a lot more than leaving even one bad capacitor in the speakers. All of the little black capacitors with the red end-caps are to be considered suspect and I would lay a fair bet that several of them are bad. Very bad. Not "non-audiophile" bad, but the kind of bad that a flat tire is bad or an air conditioner without refrigerant is bad or a television with a burned-out picture tube is bad.

The reason you might not want to by-pass all those switches in the attenuators is simple: Every time I almost did it, something stopped me. Eventually I discovered a problem with my room and speaker placement which meant I needed to use them. I was very happy to have them. Whatever improvement I could have made by removing the attenuators was far less of a problem than not being able to adjust them to the room would have been.

Your mileage may vary, but I seriously doubt it. (but I've seriously doubted things before, and was wrong)

Keep us up-to-date with what you've done, what you think about it, and how it's all coming. You're adding to the global knowledge base and we appreciate it.