Restoration: Miller & Kreisel Sound (M&K) SV-200B tower loudspeakers

WOW! Never thought I'd see another pair of these-- I actually owned a pair of these back in the early 00's. Not as nice shape as yours though. Everyone who saw them commented on their shape/size-- they came to be known as the "obelisk" speakers in my circle of friends.
Do you have the grilles? When I got mine one of the grille frames was cracked, so I had a coworker's husband build all new grille frames for me. Not too difficult.
Great job restoring yours-- and yes they do sound terrific!

sb001 said:

WOW! Never thought I'd see another pair of these-- I actually owned a pair of these back in the early 00's. Not as nice shape as yours though. Everyone who saw them commented on their shape/size-- they came to be known as the "obelisk" speakers in my circle of friends.
Do you have the grilles? When I got mine one of the grille frames was cracked, so I had a coworker's husband build all new grille frames for me. Not too difficult.
Great job restoring yours-- and yes they do sound terrific!

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Thanks! Yeah, I have the grills...the frames were fine, just needed new cloth. I did the cloth soon after I rebuilt the plate amps. An AK member sent me a pair of badges for the grills too, which was icing on the cake. They look awesome now. I'll post some recent pics tomorrow.

I will vouch for how good these sound, and that is before this most recent work. I stopped at Sonance's place just a week or so ago and I was impressed with what I heard. Wish I had more time to listen.

Great threads Sonance. Guess what? I picked up a pair of the SV-200s too! They are in excellent cosmetic condition but both amps have the terrible 120 Hz buzz. It almost sounds like shortwave radio or old AM static. The sub volume control has no effect on the level or character of the hum.

Although I appreciate your impeccable documentation of your restoration I don't really see where your thoughts about what effect each step had on the performance of the speakers. For instance, did replacing the power supply electrolytic cap eliminate the hum? Right now I can't get ANY signal through the amps other than the hum so I don't even know if it is worth repairing the amps as you did or replace them as others have done.

I'm inclined to replace the tweeter XO caps as I too don't hear stellar high frequency reproduction right now.

I'd love to get those schematics if Ken K is OK with you distributing them to me.

-Psarah

psarahtonen said:

Great threads Sonance. Guess what? I picked up a pair of the SV-200s too! They are in excellent cosmetic condition but both amps have the terrible 120 Hz buzz. It almost sounds like shortwave radio or old AM static. The sub volume control has no effect on the level or character of the hum.

Although I appreciate your impeccable documentation of your restoration I don't really see where your thoughts about what effect each step had on the performance of the speakers. For instance, did replacing the power supply electrolytic cap eliminate the hum? Right now I can't get ANY signal through the amps other than the hum so I don't even know if it is worth repairing the amps as you did or replace them as others have done.

I'm inclined to replace the tweeter XO caps as I too don't hear stellar high frequency reproduction right now.

I'd love to get those schematics if Ken K is OK with you distributing them to me.

-Psarah

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That's great to hear! They certainly have the potential, given a little bit of TLC. Are yours walnut or oak? What condition is the foam on the 12" woofers? Most importantly, how loud is the buzz you're describing? If the gain knob has no effect on it AND you aren't getting audio signal to pass through, then you might have a short on each amp somewhere, as one of mine had.

With the pair I found, one of them actually worked, and could have probably gotten by with new woofer foam and some electrolytic caps. The other one, with the LOUD buzz and static, had corrosion on the electrolytic cap leads to the point where it ate through 1 leg of 1 cap. That was the main issue causing the crazy loud noise and keeping signal from passing. You may have a similar issue going on with your amps.

M&K did send out a service bulletin regarding the gain knobs of their woofers, which I'll attach...it basically just tells you how to use contact cleaner to clean the pot. It's worth a shot and would be the cheapest first course of action.

I'm not sure what you mean about the effects of step and my thoughts. Are you talking about the amps or the speakers in general as I restored them? My approach for the amps was to completely restore them with the best parts I could afford at the time, using much higher spec'd parts, hoping for longevity and better sound. I wasn't able to compare before and after with the Volkswoofers. They sound great now though!

You'll need to focus on one portion of these speakers at a time. Get the woofers & amps running first, then move on to the XO caps if you'd like. At the very least, I'd suggest replacing ALL of the electrolytic caps on the amp boards and power supply. Replacing the amps would be a last resort for me. Good luck, I hope you get these working again!

Clean the bass level control with DeoxIT D5 before you go to far. They are known to be an issue.

The obelisks are walnut finish and probably just need a little oil. The top dispersion damping foam is in great shape but there is NO lower foam damping that I see in other photos. A pretty easy fix though.

The foam surround rings seem to have been restored before I got the pair and are all in great condition and pliable. All of the speakers are working fine. I'll try the DeoxIt first but I really don't see any of the corrosion documented in your photos.

The reason I asked about what effect each of your replacements may have made is because I'm not as confident with a de-solder/re-solder job as your are. The fewer opportunities for me to make a fatal mistake, the better. I haven't even figured out how to get the board off of the plate yet.

So I really must solve the buzz issue first which is in both speakers and quite loud... about the loudness of a male conversational voice. It starts loud and then slightly decreases after 6 or so seconds. The buzz is not a consistent 120 Hz buzz. It is dirty and sparkling at random outbreaks. I don't want to keep it plugged in too long for fear of a short that might damage everything. But I would like to see if the years of dust could burn out of the pots.

Thanks!!! I can post photos if that is helpful.

-Psarah

Very cool, I prefer the walnut finish. Mine came out great a few applications of Watco Rejuvenating oil. That's a good sign that the 12" woofer foam is newer, should be good for a while. Finding foam for the front baffle shouldn't be tough.

Don't worry about taking the board from the plate yet, that's actually the hardest part of all the work. They're held together at the speaker input connections, which are pretty hefty holes filled with solder. Unless you have a decent solder sucker (air pump or spring loaded), I'd steer clear of taking them apart for now. If it's not the old gain pots, I'd try replacing the power supply caps next, which is pretty easy, they're screw-on types.

BTW, the buzz from the one bad woofer amp I had was at least a male shouting voice , super loud. It was a pretty bad short though!

Thanks! I'm praying it's the pots. But I need to replace the 2 power caps per amp. They look like they are good shape but I don't think my multi=meter can measure their performance.

HEY... here is another VERY STRANGE coincidence. The model number(s) on mine are also hand corrected with a black Sharpie! If there were multiple generations then I'm guessing these are 1st Gen.

Since you're the only one that seems to know anything about these speakers... do that amps have any "auto On/Off" capability or are they always on? I don't see anything like a FET that would switch it on/off. And if it is in an always on state then I need to look at different power caps or find a 3rd party plate amplifier instead.

They're always on, but when not passing signal, they take up very little energy. At least that's what the owner's manual says. I'll PM you the manuals and schematics here shortly.

I leave mine on 24/7, plugged into and RPGC 400 Pro. They stay warm at idle, but get hot when playing music at louder levels.

A quick update... I noticed on one amp the buzz quiets somewhat after about 30 seconds. I think that leads to dry power caps. So I took out all of them and the same thing was true on both amps... One cap had some capacitance value (I don't think I'm using a cap meter properly to know how far off) but the other cap barely had continuity. I'm not sure how that can happen since they appear to be wired in series.

I'm going to go ahead and get replacements for 4 of those. I might use your 8000uF solution since they fit the board better than the 7200uF I found so far. I'm hoping that will solve all of the obnoxious buzz.

But I started thinking that *IF* it doesn't solve the buzz to see what a bi-amp solution would sound like. I bypassed the Volkswoofer amp to a 120w x 2 amp and let Audyssey establish the crossover point which was quite high at 110Hz. but they sounded very good.

HOWEVER, they are definitely missing something from around 14kHz and up. That could very well be the old XO capacitors but could also very easily be the limitation of the tweeters.

Did you notice a lower extension and higher extended range after your XO mod? If so I'm going to buy all of the caps (electro and film) together and save the shipping costs, especially if I order from Parts Connexion.

So I'd rebuild the XO caps (leaving the inductors as they stock) and the 2 power caps but leave the amp board cap rebuild for later.

Thanks again! You've given me hope that I can do this.
PsT

Yeah, those power supply caps are old, best to swap them out. I think I used 8200uF caps.

As far as the tweeter, it's the famous Peerless K010DT (810665), and should have no problem playing up to 20kHz, if not higher. M&K specs the SV-200's to 22kHz on the top end and mine have no issues playing that high. They can get really bright, depending on how you have the knobs on the back set. They sounded great before the recap, but even better after. I love this tweeter.

The Peerless tweeter uses ferrofluid, which may have dried up and needs to be cleaned and replaced. With the caps being complete toast in your pair, it's starting to sound like the speakers just sat there for many years without being used. Hard to say if it's gonna be XO caps or ferrofluid that bring them back to life.

hmmm... ferrofluid. Hadn't thought of that. My Showco S-200 speakers have 2 Philips tweeters each that are ferrofluid. I guess I need to learn how to do that too.

As I was ordering parts today I noticed that one of the amp pots had "MOUSER" engraved on it. So I'm guessing that one has been changed already.

Hey Sonance... when you upgraded the power cable did you ground it? And if so, where did you ground it to?

psarahtonen said:

Hey Sonance... when you upgraded the power cable did you ground it? And if so, where did you ground it to?

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No, I used polarized 2-prong, 12 AWG. No ground needed, I kept it like the original cable.

A most impressive project! I wish I had the electrical knowledge to rebuild amp boards like that!
You should be damn proud of your work, you certainly earned bragging rights!
Cheers!
Glenn

GD70 said:

A most impressive project! I wish I had the electrical knowledge to rebuild amp boards like that!
You should be damn proud of your work, you certainly earned bragging rights!
Cheers!
Glenn

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Thank you very much Glenn! These speakers were well worth the effort put into them, they keep me smiling.

Thank you for the inspiration on the crossovers Sonance. These are out of my S1-B's, I went a bit crazy..I am new to the audio word and still trying to learn. This is my first time working on a crossover and doing this much soldering work. I only ended up replacing the resistors on the mids for the L pad as I seem to like the tweeter bright (number 6 setting) which is bypassed. I used nylon standoffs/screws and acrylic to create the second level, All of the capacitors were then glued down.

I only have one done but from what I can tell there seems to be a better separation of instruments and better detail. Now to start on the other.. hopefully it wont take as long as I have the layout figured out now. After that its onto re foaming a V3b I picked up last night for $16. I enjoyed reading about your experience redoing your Volksfoofers. hopefully mine blends well with the satellites.

Sonance'84 said:

Restoration: Miller & Kreisel Sound (M&K) SV-200B tower loudspeakers, cont'd

> Part 2 - monitor crossover rebuild <


Now, for the past 2 days I've been working on swapping in those new parts from the previous post into these crossovers. It was quite a challenge, as you can see there is virtually no room on the board for larger film caps. I went with Mundorf E-Cap "plain", which are slightly larger than their "raw" version of this NP electrolytic cap. While the "plain" are much larger than the original T.I. caps, they're still much smaller than most film caps of any significance, allowing me to fit them in with a little creativity. Two of the caps had to be paralleled to meet the required values. All caps were then bypassed with Vishay MKP 1837 film caps of 0.01uF. The Mundorf MOX resistors fit better than the original sand cast ones, so that helped a little. I did have to wire a pair in series to get a required value, which was a first for me, but no biggie. Also, the rotary knobs got a good cleaning with DeoxIt while I was in there. Oh, and RTV was used to secure caps together and to the board, so they don't vibrate around.

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I'm definitely curious too about any sound quality improvements, after the amp recap and rebuild, and the main crossover rebuild? I have a M&K V3B sub that needs rebuilding too (hum). Plus, I'm looking at using Mundorf E-Cap's for a crossover rebuild, so if you can comment, that'd be great! That's the reason for my curiosity, as I need to do the same work.

Thanks!