Speaker voicing and capacitor types used

[ar_pro]

Thanks for the competent and reasonable reply, Ken...I would love to hear from someone who went to the time & expense of re-capping, re-choking, and re-wiring who *did not* believe that there was a dramatic improvement in air, a lifting of gossamer veils, and a more natural & fluid musicality as a result of their efforts.

It's almost as if the professional designers of these classic systems were working in some sort of Dark Age, when science and engineering hadn't yet benefited from the subjective concepts and design truisms now available to tinkerers, everywhere.

[Guest Bret]

>Pardon the interruption, but the AR90 bass crossover uses a 250uf cap, not a 2500uf cap. <

Ah, yes, but the 10pi uses a 2500uF cap.

Bret

[rrcrain]

Thanks,

I realized my error shortly after I typed it, but wasn't able to get back here fast enough to correst myself. I used a 200 and 150 Solen and had good results.

[Guest Bret]

>No 6uF is NOT 6uF. <

Hey, I have another dumb question.

Why aren't the ESR figures or even the manufacturer and part numbers given for these caps in the schematics?

Seems a heck of a thing to overlook or omit since they are important values used in the design of the crossover.

Bret

[Guest Bret]

I spent quite a while browsing around Vishay's website.

http://www.vishay.com

They have electrolytic capacitors they consider "low ESR" but without knowing what the original capacitors' ESRs were it's hard to tell if "low ESR" is what we are shooting-for to go back to OEM values.

Evidently, Vishay bought Sprague and Mallory and everyone else they could find.

Maybe Tom has some info in his valuable library of files that would help.

Bret

[tysontom]

>>No 6uF is NOT 6uF. <

>

>Hey, I have another dumb question.

>

>Why aren't the ESR figures or even the manufacturer and part

>numbers given for these caps in the schematics?

>

>Seems a heck of a thing to overlook or omit since they are

>important values used in the design of the crossover.

>

>Bret

Bret,

If you are referring to the AR crossover schematics, those details are not appropriate to list product details there. On the other hand, if you look at the crossover *drawings* and dimension drawings, and so forth, you will find excruciating detail and specifications, ad nauseam, right down to the smallest item, including screws and washers and so forth. Manufacturers also maintain detailed specifications for sourcing and so forth by each part number of each part they use in a product. It would probably be redundant to list all this details again in the schematic diagram.

--Tom Tyson

[johnieo]

Bret:

The ESR of non-polars will vary from 0.01-0.05 for small sizes to as high 0.1-0.25 for large, hundreds-of-uF.

It is impossible to cut through the hype when *lower* and *new and improved* are not defined. If a mfr reduces DF in a large cap from 0.25 to 0.2, it's indeed lower. However, if another mfr makes the same size with a DF of 0.15, then it is not the lowest! One has to keep hunting for the data; alternate web-links may contain different degrees of product detail. Perhaps try searching for that brand and check other links?

[Guest Bret]

>On the other hand, if you look at the crossover *drawings* and dimension drawings, and so forth, you will find excruciating detail and specifications, ad nauseam, right down to the smallest item<

Thanks Tom.

I don't know. . . I just seem to lack the vocabulary I need. I've looked at the blueprints (available on the site) and there are part numbers and specs and all sorts of good detail.

In fact, I used the info from the ones available for the 10pi to get the right thread count for a screw, so I've seen what I think you are talking about.

But I'm still flopping around like a boated mackeral.

Take the 10pi, for instance. It has a 2500mfd 60v Callins cap. Now, if memory serves, AR made a fairly big deal out of using "computer-grade non-polar capacitors." Lacking any other detail and getting no hits using any or any combination of numbers off the cap itself, I'm figuring "computer grade" may still mean approximately the same thing it did 25 years ago.

I have spent quite literally hours with Google searches trying to find a product data sheet on this Callins capacitor. I have searched wide and tunnel-visioned and have yet to hit what I need. I've learned a few things about capacitors in the process.

Do these cross-references exist? I don't know. I can't seem to get Digi-Key's X-reference to "hit" on anything.

But it looks as though Vishay DOES make what is PROBABLY suitable replacement "Compulytic" replacements. Of course, since I can't find a data sheet on the part I'm trying to replace, and since a reading from that part would do me no good since the values change with age, I may never know. . . grrrrrrrr.

Mouser.com doesn't have them.

I spent a couple of hours early this morning at my local electronic supply stores and they don't have them, either. I got irritated that the guys behind the counter seem to know less than *I* do about capacitors and *that* has to be a paranormal phenomenon.

So what did I do? I picked-up a $70 capacitance meter and $90 worth of NP electrolytics that I can "make-up" to within 5-10% of original spec.

When I asked for an ESR tester they looked at me like I had a rudely shaped antenna and/or was wearing a tutu.

My next step is going to be contacting the manufacturer to see who the @#$% they sell these "low ESR, Compulytics" to so I can try to buy some. (is my frustration showing?)

No, my next step is going to be to parallel a bunch of the caps I bought and stick 'em in a cabinet and see if there's any difference. $180 for a CapWizard ESR tester is kinda steep since I don't plan to do this for a living and until I find a suitable replacement cap it really doesn't matter if the ones I've got test bad.

Film at 11:00. No, make that NP electrolytic at 11.

Bret

[Guest Bret]

>The ESR of non-polars will vary from 0.01-0.05 for small sizes to as high 0.1-0.25 for large, hundreds-of-uF.<

Good grief.

I'm going thru all of this for max 1/4 ohm and very probably much, much less? And this 1/10th of an ohm was calculated and perhaps compensated for in a passive crossover? Yeah, right.

Holy cow.

You know, I have a friend who says that I'm often paralyzed because I over-analyze. Think he might have a point?

Bret

[tysontom]

>

>Take the 10pi, for instance. It has a 2500mfd 60v Callins

>cap. Now, if memory serves, AR made a fairly big deal out of

>using "computer-grade non-polar capacitors." Lacking any

>other detail and getting no hits using any or any combination

>of numbers off the cap itself, I'm figuring "computer grade"

>may still mean approximately the same thing it did 25 years

>ago.

>

>I have spent quite literally hours with Google searches trying

>to find a product data sheet on this Callins capacitor. I

>have searched wide and tunnel-visioned and have yet to hit

>what I need. I've learned a few things about capacitors in

>the process.

>

>Do these cross-references exist? I don't know. I can't seem

>to get Digi-Key's X-reference to "hit" on anything.

>

>But it looks as though Vishay DOES make what is PROBABLY

>suitable replacement "Compulytic" replacements. Of course,

>since I can't find a data sheet on the part I'm trying to

>replace, and since a reading from that part would do me no

>good since the values change with age, I may never know. . .

>grrrrrrrr.

>

>Mouser.com doesn't have them.

>

>I spent a couple of hours early this morning at my local

>electronic supply stores and they don't have them, either. I

>got irritated that the guys behind the counter seem to know

>less than *I* do about capacitors and *that* has to be a

>paranormal phenomenon.

>

>So what did I do? I picked-up a $70 capacitance meter and $90

>worth of NP electrolytics that I can "make-up" to within 5-10%

>of original spec.

>

>When I asked for an ESR tester they looked at me like I had a

>rudely shaped antenna and/or was wearing a tutu.

>

>My next step is going to be contacting the manufacturer to see

>who the @#$% they sell these "low ESR, Compulytics" to so I

>can try to buy some. (is my frustration showing?)

>

>No, my next step is going to be to parallel a bunch of the

>caps I bought and stick 'em in a cabinet and see if there's

>any difference. $180 for a CapWizard ESR tester is kinda

>steep since I don't plan to do this for a living and until I

>find a suitable replacement cap it really doesn't matter if

>the ones I've got test bad.

>

>Film at 11:00. No, make that NP electrolytic at 11.

>

>Bret

Wow! Good grief! Well, you are probably right -- finding those exact replacement electrolytics seems to be difficult. I also did a search on the very ones you mentioned, the 2500 mfd. 60 V AR-10Pi caps, and I could not find them anywhere on internet searches. Perhaps some place such as Newark Electronics might have something like it, but you'd probably need their big catalog to find it.

--Tom Tyson

[r_laski]

This 10pi discussion really belongs in a separate thread.

>…I don't plan to do this for a living and until I find a suitable replacement cap it really doesn't matter if the ones I've got test bad.<

Bret,

Let me start by saying that all the anguish and frustration you are writing about I went through over a year ago. For about a six month period I did what you are now doing before I finally decided on a course of action to repair/restore four AR-11s, a pair of AR-LSTs and the pair of AR-90s. I also hit the same brick wall you did trying to find a replacement for the Chicago Industrial 2500uF cap in the AR-LSTs. It ended up I did not have to replace these capacitors in the LSTs.

I can’t find a crossover schematic for the 10pi nor a technical explanation for that large cap being in the 10pi crossover. However, I do know why the same capacitor is in the LST. Quoting from the AR-LST manual, “A large capacitor in series with the autotransformer prevents excessive amplifier loading at subaudible frequencies where the transformer’s inductive reactance decreases.”

Since there is an autotransformer in the 10pi, I can only deduce that the 2500uF cap is there for the same reason. What this tells me is this capacitor, working at “subaudible frequencies” (below 20Hz), has THE LEAST (little or no) impact on the “voice” of the speaker. Its there to protect your amp from dangerously low impedances (inductive reactance).

I welcome anyone with access to AR-10pi technical documentation or an AR 10-pi, who can examine the crossover, to correct any of my technical inaccuracies.

I recommend before you go ripping your crossover apart, you carefully desolder everything off at least one of the 2500uF cap terminals (create an open circuit), connect your cap tester to it and take a reading. If it measures within 2500 +/- 250uF – LEAVE IT ALONE and stop looking for replacements. Concentrate your efforts on any degraded, out-of-spec, over-voltage damaged, or significantly mismatched capacitors in the crossover that have a direct impact on its sonic performance (voicing) and balance between the two speakers. Remove and replace any and all capacitors that you decide are necessary to repair/restore your AR-10pi’s.

While you are at it, take a good look at the resistors. Look for evidence of darkened / burned away hot melt glue around the resistor. It is a know FACT that gluing resistors to the crossover board is a bad idea. Resistors heat up during use and as they heat up their resistance value changes. Having them in contact with the crossover board or other components creates hot spots and can lead to degradation / failure of the resistor. (Source: North Creek’s Speaker Wiring Guide, written by George Short III, former AR engineer)

Because of this, you will notice, starting with the vertical series, AR changed the way they mounted resistors, suspending them above the crossover board and away from other components.

>>I have spent quite literally hours with Google searches trying to find a product data sheet on this Callins capacitor. I have searched wide and tunnel-visioned and have yet to hit what I need. I've learned a few things about capacitors in the process.<<

Callins is long ago out of business. Try Callins/IEI, but I think it’s a dead end as well. On the Callins capacitor does it have something like 23-85CES as one of the alpha numerics?

Rich

[ninohernes]

Honestly, I have never come across a bad original AR capacitor. The ones in my 1959 AR-2's sound great, I use them with 125 watts per channel, and there is no problem. This may be due to the fact that these speakers have never been out of service. They have been used for their entire lives, and have never sat un-used. I have found that the original Chicago Industrial capacitors seem to age very well.

[Guest Bret]

>On the Callins capacitor does it have something like 23-85CES as one of the alpha numerics?<

That's the one.

I bought a pair of caps from a forum member on eBay. One was a Callins, the other was a Sprague (both 2500uF 60v). The Callins read 2740+. The Sprague "Compulytic" read 2501.

Now, the reason I didn't abandon this thread when I started talking 10pi is because the issue of "capacitor replacement" is really the same.

I just got home (5:00am) from doing an experiment on a 90. The other one will get done tomorrow. But my experience with these old capacitors seems to be paralleling yours to a greater or lesser degree.

The 350uF cap was very slightly high and was left alone. The 80uF read over 100uF and was replaced. The biggie was the 30uF that read over 50uF. The 24uF was okay, but I replaced it anyway (long story having to do with physical realities and not electronics). The 4uF was 4, the 8uF was 8, so I didn't even check the 6uF or the 2uF(because I was in a hurry to hear what I'd done "thus-far" and that last 6uF is a bear to reach).

Now, keep in mind I got my caps from a peg-board. They were NP electrolytics. Nothing "audiophile" about these. I changed no wiring, no new resistors (didn't even check 'em), didn't take the attentuators out of the loop, nothing. I didn't even do a solder job I'm proud of.

This was just a crude experiment.

So how putting a "net" two capacitors back in spec change the sound of the speaker?

I think the difference is STRIKING. The obvious thing that changed is that the upper midrange quit trying to produce lower midrange sound, the lower midrange had more output (in other words it sounds like the crossover point between these two drivers got moved "up" a bit). Looking at the schematic, I don't really see how this could be true, but that's what seems to have happened.

Subjectively, this translated into MUCH improved "transparency" and the elimination of a nasal (or honky) quality.

Without an ESR meter, I don't know if I changed that spec much, but putting the uF measures back in spec really, really, really improved the sound.

As I said, this was a crude experiment. It was done fairly hastily and pretty primitively and resulted in a large difference.

The conclusion I *think* I have come to (I'm awfully tired right now) is that I want to check a lot of capacitors.

Bret

[Guest Bret]

>I can’t find a crossover schematic for the 10pi nor a technical explanation for that large cap being in the 10pi crossover. <

Are you capable of drawing a schematic . . . like with whatever the "modern" version of AutoCAD is?

Bret

[Guest Bret]

>If you then go and change your 6uF cap to a "better" one with a different ESR, the response of the crossover will change in ways you might not expect. The tweeters might get louder. There might be an underdamped bump just before the woofer rolloff, etc. <

Yes, I can see that what you say is inarguably true.

If you found a 30uF cap that read over 50uF, wouldn't that have a nasty effect? Would you be more concerned with the possible drop in ESR of a new cap(and not replace it) or would you be more concerned with a doubling of the capacitance(and replace)?

Yea or nay: Wouldn't the change in capacitance change the crossover frequency in large ways?

Crude experiment of last night: In an AR-90, the 80uF was at 100+uF and the 30uF was at 50+uF. In changing these two out with new NPE caps of no particular merit, the upper-mids in some 90s seemed to begin producing only "higher" sounds and *a smaller proportion* of "all sound."

Will you take just a fleeting moment of your limited and valuable time to look at the AR-90 schematic available in the Forum library and predict the *major* expected changes of increasing the 80uF to a 105uF and the 30uF to a 54uF?

Thank you in advance for the benefit of your invaluable experience and insight.

Bret

[r_laski]

>>Are you capable of drawing a schematic . . . like with whatever the "modern" version of AutoCAD is?

Look at your AR-10pi crossover and see if one terminal of the 2500uF cap is connected to the transformer and the other terminal connected to the (-) binding post terminal. If a schematic was available, this part of the circuit would look very much like the LST crossover schematic available in the LST manual on the Classic Speaker Pages, but the cap is 2500uF not 5000uF).

Rich

[r_laski]

>>I just got home (5:00am) from doing an experiment on a 90. The other one will get done tomorrow. But my experience with these old capacitors seems to be paralleling yours to a greater or lesser degree... The 80uF read over 100uF and was replaced. The biggie was the 30uF that read over 50uF. <<

Bret,

Yes, this is very much like what I found on the pair of AR-90s I worked on. Your readings are even worse than those of the caps I pulled out.

I think you may be on to something about these two specific capacitors having a tendency to degrade and get way out of spec and really make the AR-90 sound like cr@p. There is a very audible difference between an AR-90 with these caps degraded, and one with new caps of correct values irrespective of the type of replacement cap used. Except, I found almost no improvement when I replaced these two caps with Dayton caps (paralleled 40uFs to get 80uF and single 30uF).

Let us know what you find with the other AR-90.

Rich

[Guest Bret]

>Let us know what you find with the other AR-90.<

I didn't find it, but the owner, Don, did. Same thing as in the other cabinet. The 80 was over 100, the 30 was over 50, and there was one more badly out of spec.

We might get to listen again Tuesday night.

As we've both said, we don't know if the improvement is "right" or not, but I think it is safe to say that it is "righter."

Bret

[Guest Bret]

>Let us know what you find with the other AR-90. <

Rich, I just spent a couple of hours listening to the pair of AR-90s Don and I have been experimenting on.

Unbelievable. It's simply unbelievable. It makes perfect sense that aging capacitors would be ruining the sound of our speakers, but I would never, ever, ever have guessed the extent of the problem.

I said, early-on, that I didn't want to be startled. Well, I'm startled, and startled sounds terrific.

Bret

[roundhome]

>>>Are you capable of drawing a schematic . . . like

>with whatever the "modern" version of AutoCAD

>is?<<

>

>No AutoCAD and no AR-10pi.

>

>Only a blank piece of paper, a ruler, and a yellow number two

>pencil.

>

>Look at your AR-10pi crossover and see if one terminal of the

>2500uF cap is connected to the transformer and the other

>terminal connected to the (-) binding post terminal. If a

>schematic was available, this part of the circuit would look

>very much like the LST crossover schematic available in the

>LST manual on the Classic Speaker Pages, but the cap is 2500uF

>not 5000uF).

>

>Rich

Rich i'm back to this all caps replaced in my LST's but the 2500 uf.

if we take a close look at the LST schematic you will see that the 5000uf is four 5000uf polorized caps with two conected at the negs and the two sets in parallel to get the 5000uf. now why can't we take two 5000uf caps and do the same to make the 2500uf?

Jim

[KlausDK]

Hi Jim

My LST's has two bipolar 5000 myF in series, each 60 Volt, resulting in a 2500 myF capacitor of 120 volt.

BR Klaus

[roundhome]

>Hi Jim

>

>My LST's has two bipolar 5000 myF in series, each 60 Volt,

>resulting in a 2500 myF capacitor of 120 volt.

>

>BR Klaus

Hello Klaus

Is this the way they came from AR or did you do it?

do you have any pictures you can post?

Thank you

Jim

[KlausDK]

Hi Jim

Mine were 100 % untouched original in the Cross-over before I started upgrading with new capacitors, the picture taken before upgrade. One of the two 5000 myF are mounted outside the crossover plate, as you can see, connected with very long twisted wire's of low diameter. I have shortened the wire and mounted a thicker OFC type. I have put a 1 myF Jensen Oilpaper/Alu foil capacitor across the two giant caps, to get a lower ESR at higher frequencies.

I have thought af trying the 10 Ohm resistor across the caps as well, as used in 10Pi, and as reported by some, also used in later versions of the LST, but I havent tried it yet. By the way, when restoring my 10Pi I changed the original resistor with a handmade Duelund expensive (25 $/pcs) type 10 Ohm, and it really changed sound in midrange/treble (for the better). I think the influence from resistors are grossly underestimated in restoring/designing loudspeakers.

Hope this is of help

BR Klaus

[genek]

The important take-away here is the crossover difference, and for a long time I doubted this, but SteveF, a higly knowlegeable AR historian on this forum, has several letters from AR clearly stating the change in the crossover frequency of both the AR-3a and the AR-5 that occurred in the second-generation AR-3as.

Bump.

I happened across this while researching AR3 series crossovers. Do we know for a fact that the 3a change from 575 Hz to 525 Hz was a deliberate design decision, or is it possible that they changed capacitor types and suppliers due to nontechnical reasons, discovered the new caps had lowered the 575 to 525, did some testing and just decided they could live with it...?