Need Help Recapping AR-9

[Guest bobjan]

Hi. I'm a new mrmber here and am just getting back to using my old classic equpment all from 30 plus years ago. I have a pair of AR-9 speakers that I purchased new in th late 70's and just finished restoring them (except for the caps). They sound excellent, but I have been told by many people that the caps in the crossover should be replaced after over 30 years. I read a lot of the older threads on recapping but a few things remain unclear to me. I was hoping I might be able to get some help. Some of the caps I have from other projects are not exact matches but very close and was wondering how critical that is considering the originals probably had a 20% tolerance. I have some Clarity SA caps in the smaller vaues but they are 3.9 mF instead of 4 mF, 6.2 mF instead of 6 mF , 8.2 mF instead of 8 mF, 25 mF instead of 24 mF. I also have some Solen Fast caps that are 82 mF instead of 80 mF. I have some .1 mF 630v poly tin & foil caps i could parallel withthe 3.9 mF SA's to get to the 4 mF value if necessary. For the ones I don't have, I would probably just get Solens, as they cost a lot less. My other question is what to do about the 470 mF and 2500 mF in the low end section. These, as you know, are extremely large for their values, and I'm not sure if the smaller ones available today can handle the high current as well. Using polys for even the 470 would be very expensive and take up a lot of space. I can't find any computer grade bi-polar electrolytics. Has anyone replaced these and if so, could they share what they used and how it worked out? I appreciate and Thank You all for any help you can offer. Bob

[KlausDK]

I have some Clarity SA caps in the smaller vaues but they are 3.9 mF instead of 4 mF, 6.2 mF instead of 6 mF , 8.2 mF instead of 8 mF, 25 mF instead of 24 mF. I also have some Solen Fast caps that are 82 mF instead of 80 mF. I have some .1 mF 630v poly tin & foil caps i could parallel withthe 3.9 mF SA's to get to the 4 mF value if necessary.

Hi Bob

All the suggested replacements will work, and yes I would add the .1 mF 630v poly tin & foil cap to the 3.9 (and the 6.2uF as well), in my experience it improves the sound from the tweeter.

My other question is what to do about the 470 mF and 2500 mF in the low end section. These, as you know, are extremely large for their values, and I'm not sure if the smaller ones available today can handle the high current as well. Using polys for even the 470 would be very expensive and take up a lot of space. I can't find any computer grade bi-polar electrolytics. Has anyone replaced these and if so, could they share what they used and how it worked out?

Have a look here in these posts:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4582

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

BRgds Klaus

[Guest bobjan]

Hi Klaus. Thanks for such a quick reply. I checked out all of the previous posts I could find including those two listed (thanks for the links), but I can't seem to find those caps mentioned anywhere. With that post being from 2006, it's possible they are no longer available. Sound like they would have been a great replacement. I have quite a few of those .1 uF film & foil caps, so it would be no problem bypassing both the 4's & 6's. Do you think it would help any of the other vaues (maybe he 8's) or is that as far as you would go with the bypassing? It actually looks like the 24 uF is in a more importamt position in the upper mid xover than the 8 uF. I know that lots of companies make 470 mF, but their all very small, and I have a feeling the size might have to do with the amount of current going through these. I'm afraid that the smaller ones might not hold up. And the selection of bipolar types is fairly limited. I'm going to do some more searching for those two larger sizes.Thanks again, Bob

[Guest bobjan]

I checked out the Mundorf caps (M Lytic BiPolar BR63-Raw series) that someone in the older posts recommended, but I'm not sure those are OK. The original caps are rated at 60V for the 2500 uF and 50 V for the 470 uF. While the Mundorph says 63VDC, I checked the spec sheet and their only rated at 23V AC which is what speakers see.. Seems like that could be a problem over time. Any thoghts on this? They certainly have the values to make up the total capacitance, but that voltage thing worries me. Thanks, Bob

[roundhome]

I checked out the Mundorf caps (M Lytic BiPolar BR63-Raw series) that someone in the older posts recommended, but I'm not sure those are OK. The original caps are rated at 60V for the 2500 uF and 50 V for the 470 uF. While the Mundorph says 63VDC, I checked the spec sheet and their only rated at 23V AC which is what speakers see.. Seems like that could be a problem over time. Any thoghts on this? They certainly have the values to make up the total capacitance, but that voltage thing worries me. Thanks, Bob

NEW VersaTronics 470uf 470 uf non polar 100v capacitor on the e slay # 160137539877

[Guest bobjan]

Hi. I checked out that aucton and it looks like that one could be OK. Again, it's so much smaller than the original. I'm always a little leary about buying electrlytic capacitors on ebay as their is no way of knowing how old they are. Is anyone familiar with Bennic Bi-Polar Electrolytics? They make a 500 uf 100v version. I could parallel 5 of these to make up the 2500 uF, Their very reasonably priced. It would run Approx. $65.00 for all 10 that I would need. I like the idea that they could all be equal vaue with similar characteristics. Thanks, Bob

[roundhome]

Hi. I checked out that aucton and it looks like that one could be OK. Again, it's so much smaller than the original. I'm always a little leary about buying electrlytic capacitors on ebay as their is no way of knowing how old they are. Is anyone familiar with Bennic Bi-Polar Electrolytics? They make a 500 uf 100v version. I could parallel 5 of these to make up the 2500 uF, Their very reasonably priced. It would run Approx. $65.00 for all 10 that I would need. I like the idea that they could all be equal vaue with similar characteristics. Thanks, Bob

Bennic has a 1000uf so two of them and one 500uf cap would work but never tried it yet. I have 4 AR 9's in the work of doing one set now and will compair them to a pair that have not been out of the box yet hope the foam is still good. just finished 4 AR 90's they sound great. so for less the 30 bucks you can make a 2500 uf with bennic's that is all we have ever came up with

Jim

[Guest bobjan]

Hi. Have you used the Bennics with good results? They seem to be about the best choice I could find. The main reason I thought I would use 5 - 500 uF in parallel is I was told by a local dealer that repairs speakers (and has designed a few of his own) that when ganging caps in parallel, I should keep them all of the same value if possible for the best results. He didn't explain why, but I figured he knew more than me, and it couldn.t hurt to take his advise as it doesn,t change the cost much.

[Guest bobjan]

Hi. Just wanted to let everyone know that I ordered the Bennics from Madisound. Someone else had used them sucessfully and recommended them. He said that most measured 3% to 5% below their rated vaue and he made up the difference with film caps. He said this worked very well for him . I'll measure them and do the same as I have a bunch of various films from different projects. When puting together bunches of caps in parallel in electronics, I usually just strap them together with tie downs. I would imagine that inside a speaker, you need to be concerned with them vibrating from the air movement. Is their a good glue to use to hold them down. I was thinking either epoxy ( the putty kind ) or silicone glue. I see that some have used a hot glue but I don't usually like the idea of applying heat to the body of electronic components. Any suggestions? I'll be out of town for a couple of weeks, but will do the recap as soon as I get back. Thanks, Bob

[RoyC]

I usually just strap them together with tie downs. I would imagine that inside a speaker, you need to be concerned with them vibrating from the air movement. Is their a good glue to use to hold them down. I was thinking either epoxy ( the putty kind ) or silicone glue. I see that some have used a hot glue but I don't usually like the idea of applying heat to the body of electronic components. Any suggestions? I'll be out of town for a couple of weeks, but will do the recap as soon as I get back. Thanks, Bob

Hi Bob,

You can screw tie down bases into the cabinet. I have never experienced any vibration issues with them...see attached pics. Most hardware stores sell them.

If you use glue, GOOP is probably the best. It dries fast and strong. It can be purchased at most department or hardware stores. Even Madisound sells GOOP for crossovers: http://www.madisound.com/catalog/product_i...products_id=342

Roy

[Guest bobjan]

Hi Roy. Thanks for the info Those tie dowms are similar to what I use in electronics, except I use the self stick instead of screw down. I was thinking more about the Bennic lytics possibly hitiing against each other as I'll be putting groups in parallel to get to the final values. I think I'll try some of that Goop stuff.

I'll be at Home Depot so I'll check to see if they have it. Thanks again, Bob

[Guest bobjan]

Hi. I'm still away and won't get back home until the 24th or 25th. All the Bennic caps should arrive by then, so I can't wait to get this recap finished. I had a quick question. It looks like the most important of the resistors is the 6 ohm 22 watt. The others are part of the switches to reduce output, and since I've never used them, I'll probably bypass them anyway. I was going to get some replacements for the 6 ohm but the closest I could find is to put 2 - Mill's 12 watt 12.5 Ohm (from P.E.) in parallel to get a 24 watt 6.25 ohm. I'm mot sure how critical the value is in a crossover. Would the 6.25 ohm be close enough to 6? I'm going to build up the 2-larger caps on thin (1/4') wooden boards that fit in the space of the old cap. This way I can do most of the work outside of the cabinets. Then I'll remove the large can and glue the board with the caps in it's place. Thanks, Bob

[r_laski]

" I had a quick question. It looks like the most important of the resistors is the 6 ohm 22 watt. The others are part of the switches to reduce output, and since I've never used them, I'll probably bypass them anyway. I was going to get some replacements for the 6 ohm but the closest I could find is to put 2 - Mill's 12 watt 12.5 Ohm (from P.E.) in parallel to get a 24 watt 6.25 ohm. I'm mot sure how critical the value is in a crossover. Would the 6.25 ohm be close enough to 6?"

IMHO -

I'd measure the 6 Ohm resistor. If it measures OK - don't replace it. The sand cast resistors AR used are very rugged and don't usually require replacement unless the speakers have been overdriven and the resistors overheated.

If you have to replace it, consider the 25 watt sand cast resistors from Madisound. A 2.7 Ohm and 3.3 Ohm in SERIES (not parallel) will get you the 6 Ohms you are looking for.

If you do replace the 6 Ohm resistor, I recommend you elevated the resistor(s) above the board by bending the leads. This allows cooling space between the resistor and the board reducing the risk of overheating the resistor.

I'm very interested in how your project turns out and results of any subjective listening tests you do between stock/recapped AR-9s.

Rich

[Guest bobjan]

Hi Rich. Thanks for the info. I'll check out the values before replacing those resisters. I'll read all (caps, resistors, inductors)l original values just to know where things were at when I started. It won'be until the end of the month that I'll be back, but I'll certainly post progress and some photos when I'm done.

I was listening to them pretty much every day for about 3 weeks until I left, and the sound was pretty good already, so I'm anxious to see if a recap with film caps will make a difference. I have enough films to do all except the two big ones (2500 & 470) and will use the Bennic for those. A friend has been staying at my house to watch the pets, and he happens to be a computer tech, so I had him read the Bennic caps (they came yesterday). A previous poster said his read 3-5% below value, but all of the ones I got are 2-7% above value, so I won't need to add any film's to those. I'll take some before and after photos and will hopefully be able to figure out how to post them here. Thanks, Bob

[rrcrain]

You mentioned you would probably bypass the switch assembly because you've never used them. A word of wisdom based on personal experience. Don't bypass or remove the switches. The new caps will bring your tweeter and upper mid range to life to such an extent you may well want them there.

[Guest bobjan]

Hi everyone. I'm back home now and ready to start the recap process. I've been reading over all the old posts on recapping AR-9's before I start and their are so many different opinions on the large woofer caps. Some say that built up banks will not sound good. I've already put the banks together on thin wooden boards I can glue in place. All of my Bennics were slightly higher in value than indicated. I used 3 - 150 uF for the 470's and the totals came to 496 uF and 498 uF so I didn't add any films. I used 2 - 1000 uF and 1 - 500 uF for the 2500 and the totals read 2682 uF and 2687 uF. So again, no film caps. All the other caps were made up of films I had on hand and are within 1-3 % of tolerance. I always thought that banks of caps improved many of the qualities of caps so I hope the woofer banks are going to be OK. I don't really want to have to keep switching back and forth to figure it out. The only thing I would try is with and without the switches. I see that a few people say that bypassng them is a great improvemant. I wouldn't think this would make such a big difference, but you never know. I have a couple of questions regarding those switches. Their on a board with the switches mounted so I can't see them. The wires are attached on the bottom. If I want to clean them, can I just squirt some DeOxit through the switch slots without removing anything? If I leave them, I figure they should be cleaned (even though I tried them all and didn't hear any noise or scratiness) If I want to bypass them, how do I hook up the 4 wires going to the board (from front of speaker L to R -- purple-orange-white-yellow) Does anyone have a diagram of how to hook them up to bypass the switches? They have lugs on them and I don't want to cut them (so I can easily re-attach them) Sorry for all the questions, but this is my first speaker recap, and I want to be sure of what I'm doing before I start. Thanks, Bob

[r_laski]

>> If I want to bypass them, how do I hook up the 4 wires going to the board (from front of speaker L to R -- purple-orange-white-yellow) Does anyone have a diagram of how to hook them up to bypass the switches? They have lugs on them and I don't want to cut them (so I can easily re-attach them) Sorry for all the questions, but this is my first speaker recap, and I want to be sure of what I'm doing before I start. <<

Bob,

Regarding bypassing the switch board -

1. The long white wire is connected from the UPPER red binding post to the switch board. You can disconnect this wire at the binding post or remove this wire to bypass the switch board. You can also disconnect the other three wires at the switch board (easy) or desolder them where they attach to the original capacitors (a little more difficult).

2. You must then run wires from the upper red binding post to the capacitors of the lower midrange, upper midrange, and high range crossovers.

A. Run a Yellow wire from the upper red binding post to where the yellow wire that comes from the switch board attaches to the 4uF capacitor of the high range (tweeter) circuit. Or, since you are replacing the capacitors, attach one lead of the 4uF capacitor directly to the upper red binding post.

B. Run an Orange wire from the upper red binding post to where the orange wire that comes from the switch board attaches to the 24uF capacitor of the upper midrange circuit. Or, since you are replacing the capacitors, attach one lead of the 24uF capacitor directly to the upper red binding post.

C. Run a Violet wire from the upper red binding post to where the violet wire that comes from the switch board attaches to the 80uF capacitor of the lower midrange circuit. Since this capacitor is on the bottom board, you will have to run a wire from the upper red binding post to the 80uF capacitor.

3. You should be able to figure out a way to do this that is reversible so you can put the switch board back into the crossover circuit.

I recommend you recap and bypass only one speaker and test it against your other speaker before you make any modifications to it. You can then compare an "original" AR-9 with a "recapped/bypassed" AR-9. If you don't like it bypassed, reconnect the switches and compare your "original" AR-9 with a "recapped only" AR-9. As Richard mentioned, you may find the switches necessary with the new caps.

Rich

[Guest bobjan]

Hi Rich. Thanks for all the info. I want to be sure the process is easy to reverse so I can try it both ways. My original plan is to recap only one speaker at first to see how much of a difference their is. I read all of the original caps in the one speaker I started with, and they all read within spec as far as capacitance is concerned. I don't have an ESR meter so that was as far as I could test. The 6 ohm resister and all the inductors are well within spec, so I'll leave them all alone. I saved all the old caps just in case. I'll probably leave the switches at first to just hear the difference of the recap alone. If I want to clean the switches, can I just squirt in some DeOxit through the slot from the front without removing anything? I didn't want to remove the board their mounted on and can't see anything with it in the way. I've been taking some photos and will post them when I'm all done (I need to figure out how to post photos) Thanks again to everone for all your help.

Bob

[r_laski]

>> My original plan is to recap only one speaker at first to see how much of a difference there is. ... I'll probably leave the switches at first to just hear the difference of the recap alone. <<

Leaving the switches in after recapping is probably a better way to go. I could have written my recommendation either way. If you find you don't ever use them after an adequate period of listening you can always go back in and remove the switch board wires and connect wires/capacitors as I described for bypassing the switches.

>>If I want to clean the switches, can I just squirt in some DeOxit through the slot from the front without removing anything? I didn't want to remove the board their mounted on and can't see anything with it in the way.<<

I think that will NOT work. A few years ago, I took apart a similar switch (AR-11). They are well sealed. All you will be cleaning is the ball at the end of the toggle handle, not the inner workings of the switch. If anything, you want to spray the contacts where the switch is soldered to the switch board.

Rich

[Guest bobjan]

It seems like if you pulled all four wires off the switches, you would basically be connecting them all together to bypass the switches. So if I take a piece of solid copper wire and crimp and solder on 4 flat lugs to match the size of the slip on connectors already on the wires, and bend them up at a 90 degree angle to the wire, i could make a connection that would allow me to use the existing wires as is and just move them back and forth to A/B with and without the switches. I could mount this to a small piece of wood to create my own terminal strip. Does that sound right to you? Thanks, Bob

[r_laski]

>> It seems like if you pulled all four wires off the switches, you would basically be connecting them all together to bypass the switches. So if I take a piece of solid copper wire and crimp and solder on 4 flat lugs to match the size of the slip on connectors already on the wires, and bend them up at a 90 degree angle to the wire, i could make a connection that would allow me to use the existing wires as is and just move them back and forth to A/B with and without the switches. I could mount this to a small piece of wood to create my own terminal strip. Does that sound right to you? Thanks, Bob <<

A homemade terminal strip. That would work.

Rich

[rrcrain]

Morning,

I recapped my AR90s a few years back and removed the switches like your now considering. Sadly, I there have been times I wish I'd left them.

In a nutshell. the capacitance of the caps I removed from my speakers also measured in spec. They had a high leakage but that's relatively common for old electrolytics. I rebuilt one speaker first and performed an A/B test against the original speaker and the change was nearly impossible to describe. The speaker was incredibly forward, amazingly bright and very detailed. What i soon discovered by careful comparison of the original speaker versus the now rebuilt speaker was the tweaters had been effectively dead - no signal was being passed to them due to the old caps. The upper mid's were mostly dead as well. The lower mids were trying to reproduce almost everything except the bottom octave.

I rebuilt the second speaker identical to the first and it was then I discovered I had a dead upper midrange driver. Prior to the crossover rebuild, you couldn't hear the dead driver.

The upper midrange and tweaters in the AR9 and 90 are very capable of being "sharp or harsh" in the wrong room and those switches may well be wanted at a future point. I wish I'd left mine in place.

[Guest bobjan]

Hi everyone. I appreciate all the help. I'm going to finish up the recap of one AR-9 on Friday (with the switches left intact), and can't wait to compare the two speakers afterwards. Just had a tooth removed, and I wan't to wait one day, until I'm off the painkillers, before I start soldering. I'll post on Friday, and let you know what I think. If all sounds OK, I think I'll just leave the switches alone for now. I'll probably listen for a day or two to let the recapped one burn in before doing the 2nd one. If all still sounds OK by Sunday, I'll finsh up and hopefully they will match. I guess I'll have to let the 2nd one burn in also. Thanks again for the continued help. It makes this much less scarey when others who have succeded give support. I've worked on amps and preamps (and compuuters) before but this is my first attempt at speakers. Bob.

[Guest bobjan]

GUESS WHAT. The excitement to get one finished was TOO GREAT, so I didn't take the pain pills. I finished the one speaker this morning and have been listening for about one hour. The one that I did first, had a bit of a problem with the bass compared to the other one before the recap (it was about half to 2/3 as loud)-checked polarity originally and that wasn't it-polarity was OK. I thoght it might be the drivers as I had to replace the surrounds on all four woofers.The bass on the recapped one sounds great now. So, one of those big caps must have had a problem. Overall, outside of the bass, The difference is very subtle. Their is a touch more clarity and smoothness in the recapped one but it's not overly bright as some indicated it might be. The instruments seem to separate a touch better in complex passages and it seems a touch less noisy. Again, it's not a major difference, but definitely worth the recap. It might be that my room is fairly dead, as it's a living room with lots of big furniture. No room for a separate listening room in our house. Like I said when I started, outside of the bass in the one speaker, they allready sounded very good. And I could clearly hear all drivers playing before the recap. So I was only expecting a small change. But that change is definitely for the better and will protect my hard to replace drivers, so I'll listen today, and finish the 2nd one tomorrow. I think I'll leave the switches alone for now. We have another house for when we retire, and I'll have a listening room then. I might need them then,,and they appear to work perfectly, without any noise. I can always remove them in the future. Once I finish the 2nd one, I'll post some after photos. I might be asking for some help with posting photos, as I've never done that on a forum before. Like what size should they be and how do you actually get them into the post. Thanks again, Bob

[Guest bobjan]

I have some photos of the x-over boards from the finished speaker, but I'm not sure how to post them It asks for a URL, but I don't know where to send them so they can be found. Are their places to store the photos that would have the URL addresses I need. I'm hoping to finish the other one tomorrow. I have the woofers out, and all the caps are glued onto boards with the groups pre-assembled and soldered.

Thanks, Bob