AR9 outboard crossover, how to best seal cabinet

[kkc]

I just received my AR9s. During transit however some of the heavier inductors and caps in the AR9 came loose and are now tangled up in the AR9. What a mess...!

I wasn't planning to recap and rewire but given the mess and dented 2500uF caps, I will have to take everything apart anyway. I don't like the idea of using dented high capacity caps.

To make life easier, I have decided to outboard the XO. Can anyone advise me on the best way to seal the cabinet at the exit point for all the driver wires 10 wires in total?

I intend to use thick multi-stranded OFC for the internal wiring. Any thoughts?

Any ideas where I can get replacements for the woofer caps.... big values...!!!

Final question: there will be a small increase in internal volume of air.... is this likely to mke a huge difference to sound? Can I just add extra padding to compensate?

Thanks, KKC.

[ar_pro]

I just received my AR9s. During transit however some of the heavier inductors and caps in the AR9 came loose and are now tangled up in the AR9. What a mess...!

I wasn't planning to recap and rewire but given the mess and dented 2500uF caps, I will have to take everything apart anyway. I don't like the idea of using dented high capacity caps.

To make life easier, I have decided to outboard the XO. Can anyone advise me on the best way to seal the cabinet at the exit point for all the driver wires 10 wires in total?

I intend to use thick multi-stranded OFC for the internal wiring. Any thoughts?

Any ideas where I can get replacements for the woofer caps.... big values...!!!

Final question: there will be a small increase in internal volume of air.... is this likely to mke a huge difference to sound? Can I just add extra padding to compensate?

Thanks, KKC.

Exact replacements for the big electrolytics are not available, anywhere - this subject has been pretty extensively covered, and no one seems completely happy with the options.

Are you removing the switch assembly board as well? It has 4 connections of its own.

[kkc]

No, I'll keep the switch assembly. Unfortunately the 2500uF and 30Uf caps are dented which is not good. Fortunately, the coils are fine - no lacquer seems to have rubbed off.

Is there a way to reliably test the caps. The ranges are way beyond the range of my multimeter.

[johnieo]

No, I'll keep the switch assembly. Unfortunately the 2500uF and 30Uf caps are dented which is not good. Fortunately, the coils are fine - no lacquer seems to have rubbed off.

Is there a way to reliably test the caps. The ranges are way beyond the range of my multimeter.

Please replace both 2500- and 470-uF capacitors. ESR and C measurements apparently do not tell the story, so not worth mesuring. New ones do sound different, and we are working on an explanation.

Jensen Electrolytic Capacitor

470 uF 63 VDC, bipolar

EAL-362 05250D470

Made in Denmark

Jensen Electrolytic Capacitor

2700 uF 63 VDC, bipolar

EAL 3G-27633566ri

Made in Denmark

I do not know the cost of these devices or suppler in Europe, but you should be able to find the manufacturer with Google. They are physically smaller than older units, so must use thinner aluminum foil and thinner electrolyte separator. Their ESR and C variation with frequency is extremely close to that of both used and NOS Sprague non-polar devices from 1971.

good luck

[Diamonds&Rust]

Any ideas where I can get replacements for the woofer caps.... big values...!!!

Final question: there will be a small increase in internal volume of air.... is this likely to mke a huge difference to sound? Can I just add extra padding to compensate?

I'm the only one who has tried the capacitors that John has suggested you get, in AR-9s. I am completely happy, downright thrilled, with them.

I have NO WAY OF KNOWING if they sound different than the original Callins capacitors. I know that they sound better, in every respect, in every possible, conceivable way, than 30 year old Callins capacitors.

The problems other people have reported with replacing those capacitors did not happen to me when I used the Jensens.

Conclusion? Use the Jensens. The 2700s are about $50 each and the 470s are much less expensive (maybe $10-15 each).

<note to those who would argue - these are not "magic" capacitors. They are not "special" capacitors. Jensen does not even consider them good enough to recommend them for the audio chain. This ain't boutique stuff. It is, however, AVAILABLE, which is better than unavailable, and it is NEW which is better than 30 years old for reasons that will one-day be apparent.>

The second-best solution would be to replace the 470uFs only and leave the 2500uF, but that's a DISTANT second best.

As John has said - the old ones are bad. Period. Get them out of there!

Bret

[kkc]

John

Thanks for that information. I was just reading the old post from Bret about recapping the woofer section.

Where did you get the info on the 2700uF - I can only find 2200uF caps on the jensen site - see https://audio.jensencapacitors.com/products...lyt/elytradscr/. This would mean that the 2200 would have to be paired with a 300uF to total 2500uF. The tolerance is not brilliant at -10% to +50% - unless I am reading this wrongly on their website.

Incidentally, has anyone tried pairing the woofer caps with smaller polyprop caps. I noticed that when I replaced the electrolytic caps with polyprops in my AR94si, the bass was much better - faster, detailed, more effortless.

Rgds, kkc.

[Diamonds&Rust]

John

Thanks for that information. I was just reading the old post from Bret about recapping the woofer section.

Where did you get the info on the 2700uF - I can only find 2200uF caps on the jensen site - see https://audio.jensencapacitors.com/products...lyt/elytradscr/. This would mean that the 2200 would have to be paired with a 300uF to total 2500uF. The tolerance is not brilliant at -10% to +50% - unless I am reading this wrongly on their website.

Incidentally, has anyone tried pairing the woofer caps with smaller polyprop caps. I noticed that when I replaced the electrolytic caps with polyprops in my AR94si, the bass was much better - faster, detailed, more effortless.

Rgds, kkc.

I'm not volunteering him, but I am answering your question:

Forum member Klaus sent me some he bought from Jensen in Denmark. I never saw caps on the website like the ones he sent me.

If you ask nicely....

North Creek Music had some 200uF "blemish" caps they were selling for $20 each. Two of those and a 68uF is probably a good idea.

BUT - I haven't tried it so I can't recommend it.

I think a lot of what you heard in your 94s was just getting the old Callins out of there. Replacing them with anything new will help. "By-passing" the old Callins (or Spragues) did not result in a satisfying sound.

Say something nice about Danish people and maybe Klaus will help you out, as he did me. It isn't an instant solution since shipping takes a while, but it's a workable solution.

Yeah, I know the specs aren't real "tight," but they work well. The 2700uF may even measure 3000uF, but it is still doing its job (which is supposed to be transparent and completely silent, anyhow). Would a new 2500uF cap be a preferrable solution (BTW - with the electrolytics you are only looking for NON-POLAR electrolytics - which is the problem)? Sure, if you find a source for some non-polar electrolytic 2500uF capacitors, please let us in on it.

Bret

[kkc]

I have now mapped out the ACTUAL circuits used in the cross over and for my specific AR9, there's an extra inductor in the UMR XO. See the image.

I also checked two of the smallest caps and what a difference.

The values for the caps in the tweeter XO were 4.4uF instead of 4uF and 9.38uF instead of 6uF. These are very big variations. It took a very long time for the multimeter to settle on the larger cap value - leading me to believe that the caps is not functioning at all well.

I'll have these double checked by another multimeter in a couple of days. It would go a way towards explaining the anemic performance of the tweeter...!

Has anyone seen the new inductor in the UMR XO before?

Rgds, KKC.

[KlausDK]

Where did you get the info on the 2700uF - I can only find 2200uF caps on the jensen site - see https://audio.jensencapacitors.com/products...lyt/elytradscr/. This would mean that the 2200 would have to be paired with a 300uF to total 2500uF. The tolerance is not brilliant at -10% to +50% - unless I am reading this wrongly on their website.

Hi kkc

Th ecaps you found is polarized I think, look at this thread, there is a data sheet on the caps John and Bret mentions:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=1932

BRgds Klaus

[kkc]

Bret, guess what.... I removed the stuffing before I read your response..... and yes, that's a lot of stuffing. Not sure how I will ever get it all back in...!!! Especially after a few braces have been added...!

I decided against the bitumen sheets - partially. I have a very very strong feeling that the AR9 depends on some resonance from the casing. That said, I will apply bracing. When you look inside the AR9 after the stuffing has been removed.... it looks like a cathedral.... there must be some nasty resonance at the midrange levels which probably shows up when the caps are replaced and especially if the tweeter is reproducing well.

One thing I did notice with my AR94s is that by using Clarity SA caps, the sound quality improved dramatically. The caps also exposed weaknesses in the tweeter (harshness) and some mid range boom at loud volumes. I replaced the tweeter with Daytons.... man, that was an excellent move. What a steal at $30 a pair...! If I have to do that to the AR9s ..... absolutely no hesitation...!

I believe I know how to fix the boom in the AR94, but I have to be careful. AR deliberately installed the woofer in the middle of the 3-driver AR94 stack I think for 2 reasons: (1) to use the flex that a center arrangement might give and (2) to keep it away from the ground. Those small cones can give out as much well defined bass as systems costing thousands - no exaggeration. And at the moment, dare I say it, they definitely sound better then the AR9 in all areas except that the AR9 just produces much more music - meaning its all around the listener.

My current thinking is to install a rod right behind the LMR box to the rear wall. That's a perfect place as the LMR box will help reinforce and the rod behind will also be as short as possible. No side to side rod - that way the woofers have the side panels to resonate a bit.

There is one more possibility to place either an X brace or side-to-side rod between the Tweeter and UMR. But at this stage, I am not sure about doing this. An LMR X brace may make the cabinet too tight for the woofers. On the other hand it could also clean up the lows just that much more.

I will also apply bitumen sheeting on the outside of the LMR enclosure so that there resonance is reduced as much as possible. What I want is to allow the AR9's to breath resonance at the woofers but not at the UMR or LMR. At the tweeter, it shouldn't matter. So I am deliberating whether I should place some bitumen at the top at the level of the tweeter and UMR.

Additionally all the baskets will have thin strips of bitumen applied to reduce ringing.

I will use Clarity SA caps - great cost to performance, I have used them before and like them and most importantly, I can obtain equal values - reducing cap bundling induced resonance. For instance I can buy Clarity SA at 20uF, 15uF and 12uF which takes care of the 40uF, 30uF and 24uF cap replacements very nicely. I wish I could get exact or equal values for the tweeter and UMR. Here resonance will show through.

The danger with using Clarity SA is that the drivers may start to show nasties. We'll see..... all part of the fun...!

One way to reduce some of the nasties is to use different guage wiring - solid core being 1st preference and multistranded next. This means as thick as I can get multistranded for the woofer down to 0.7mm dia for the tweeter.

For the woofer, I'll use NPEs. I wasn't able to get the Danish 2700uF but Mundorf do the following NPEs: 100uF smooth, 800uF rough, 470uF rough and 82uF smooth. These are reputed to go well with Clarity SA, so I hope that it works. I am aware of the bundling caps = problems debate. Fingers crossed. At least by outboarding the XO, it wil be easy to change the caps...! I'll hold onto the old 2500uF..!

So in summary, my only concern really is exposing driver weaknesses. Everything else I can tweak. Now all I am waiting for are the caps and away we go...!

My amp to drive this will be a 500wpc Class D. I tested the prototype on my AR94s and I was shocked into amazement....!

So there you are ... all my legless suppositions. Mostly based on gut feel. I am not an engineer, although I have the background. It's all an experiment.

kkc.

[Diamonds&Rust]

Bret, guess what.... I removed the stuffing before I read your response..... and yes, that's a lot of stuffing. Not sure how I will ever get it all back in...!!! Especially after a few braces have been added...!

I don't know either. But you've got to. Otherwise you're going to end-up with a big nasty.

So in summary, my only concern really is exposing driver weaknesses. Everything else I can tweak. Now all I am waiting for are the caps and away we go...!

Sounds like fun. I can't wait to hear what you think as you think it.

My amp to drive this will be a 500wpc Class D. I tested the prototype on my AR94s and I was shocked into amazement....!

I used a class D amp on a pair of 14s and a pair of 10pis set to 8 Ohms (2pi). The 14s sang. The 10pis laid there and sounded... thin and dimensionless. If you're using one of the Wyred or PS Audio amplifiers I would be very, very interested in your feelings about them driving the 9s when compared to one of the big old tank amplifiers that heats a room and could be used for battleship ballast.

It's been explained somewhere on this forum (I think) why the AR 12" woofer is so hungry for current compared to the 10" and other vintage drivers, but I couldn't tell you where to begin to look for the explanation.

Just know that if you find the 9s won't shake the house with that much power, the first most likely culprit would be that the woofers have been resurrounded with considerable offset error (not "zeroed" up and down in the motor - constraining throw in one direction - this you can check with a ruler. The 3a restoration guide may help with that, the drivers being just about the same), if not offset error, then maybe a refoam problem. I am talking about pipe organ pedal tones and bass drum (concert, big ones) hits, and... well, the very, very bottom of things, not "bass" in the conventional sense. If you hear any of that conventional "flapping around" noise, something isn't right.

The bass should be completely, absolutely effortless. No bloat, no "boom," no sign of distress, just a NOTE where most speakers play a "noise" or don't even bother trying to go.

If you confirm the woofers are in good working order, and yet you aren't getting that "Is-that-all-you've-got?" seismic feeling from them (given the right source material), then I would encourage you to try one of those diesel locomotive look-alike amplifiers from days past. They say they've worked-out the lack of current available from Class D outputs, but until you tell me so, I'll remain skeptical.

My **extremely limited** experience, which I have described in its entirety, tells me that maybe **my** Class D amp wasn't up to making an AR woofer move like god intended.

So there you are ... all my legless suppositions. Mostly based on gut feel. I am not an engineer, although I have the background. It's all an experiment.

You're giving me an opportunity to re-live an experience vicariously, and adding to it by doing some of what might have been fun, but I didn't do.

People who have never heard and felt the low distortion thunder of a properly driven pair of AR9s can't understand the enthusiasm. They think we'd be impressed with a big subwoofer. They might think we're talking rock and roll PA-type bass. Or maybe they've never been in a church with a big pipe organ with someone standing on a low pedal... It's an amazing experience.

You know what's fun? I don't know what kind of music you like, but find a track with some bottom that you know a visitor knows like the back of their hand. Put them in the sweet spot. Turn it on; not too loud, but loud enough... And watch *them.*

Enjoy.

Oh - fleeting thought... I wouldn't be worried too much about tweeter or midrange resonances to begin with. There's precious little you can do about it in the first place, and in the second place the cabinet is so massive, and third the woofers probably shake the entire enclosure more than the tweeter's throw at times, and fourth... the width of the cabinet and distance of the tweeter from the midrange is probably going to swamp any resonance problems you encounter. It'd be like worrying about filling a tire with exactly the right pressure of 100% nitrogen for the BEST performance, while not noticing a big sidewall bulge.

[kkc]

Just know that if you find the 9s won't shake the house with that much power, the first most likely culprit would be that the woofers have been resurrounded with considerable offset error (not "zeroed" up and down in the motor - constraining throw in one direction - this you can check with a ruler. The 3a restoration guide may help with that, the drivers being just about the same), if not offset error, then maybe a refoam problem. I am talking about pipe organ pedal tones and bass drum (concert, big ones) hits, and... well, the very, very bottom of things, not "bass" in the conventional sense. If you hear any of that conventional "flapping around" noise, something isn't right.

Bret, thanks for your very helpful comments. Can you explain how precisely one can measure the offset error, if any? I had a look at the PDF on the AR3a Restore and was unable to find anything.

Thanks very much, Kunjan.

[Diamonds&Rust]

Bret, thanks for your very helpful comments. Can you explain how precisely one can measure the offset error, if any?

No.

I always sent mine away to be "fixed" (it didn't always work-out that they were fixed, though) so I never had to do that - but I certainly noticed when a couple of my woofers were refoamed with a sagging spider.

There's a reasonable way to tell.

If the spider is good and flat when you get the foam replaced, chances are they are pretty close to right.

Bret