M&K find...gonna need some help with these

Sonance'84 · May 8, 2013

Well, I came across some rare M&K speakers, model SV-200B. Pretty dusty, but overall in great physical condition. The tags were clearly made for the SV-100B, but there's a 2 sharpied over the 1. I couldn't find a photo of the SV-100B's, so I'm not sure of the differences. I could only find very limited info on the SV-200, so I hope others might be able to chime in with more.

They're 40.5" tall and weigh roughly 50-60 lbs each. Each tower is made up of an S-2B satellite speaker (1" silk dome tweeter, 6.5" poly midbass) and a Volkswoofer 2-B (12" powered sub, 200 watts RMS).

So far, I've tested them and one woofer was blown upon plugging in the plate amp, even with no signal coming in and the bass level pot turned all the way down. It made a loud oscillating noise and blew the foam and dustcap open, even though it was only plugged in for about 2 seconds. The external fuse was fine still. The other amp/woofer seems okay, but the foam is shot. Both mid/tweeter sections work.

I'll have to pull the woofers and amps to get an idea of whats going on, but I'm no expert on powered subs or the M&K brand at all. If anyone has some ideas on what to look for, please offer them up. These should be a good project if there's a light at the end of the tunnel.

Here's a link to the restoration thread on these - https://www.audiokarma.org/forums/showthread.php?t=626741

janikphoto · May 8, 2013

They sure make pretty woofers...

budgetaudio6 · May 8, 2013

Those are really Quite rare me thinks!!! The oscillating woofer may be taken care of with changing out the surrounds...They oscillate when teh seal is lost...you done good . You will be rewarded with excellent bass .... Never seen those before!

wmgwizard · May 8, 2013

The picture of the amp plate shows a cap over where the crossover frequency adjustment knob would be.

Is this cap removable ?

Is there a pot behind the cap, or is there no adjustment for the crossover frequency ?

I'm asking be size I just got a Volkswoofer 2b that has a similar setup.

7.62 · May 8, 2013

I'm no help but saw them on the list and almost went after them myself, nice find and good luck on fixing them.

240sx4u · May 8, 2013

I'd suggest just changing those plate amps for newer ones, but M&K may have done something with the circuitry to EQ the sub end. Those are super cool speakers!

Sonance'84 · May 8, 2013

wmgwizard said:
The picture of the amp plate shows a cap over where the crossover frequency adjustment knob would be.

Is this cap removable ?

Is there a pot behind the cap, or is there no adjustment for the crossover frequency ?

I'm asking be size I just got a Volkswoofer 2b that has a similar setup.

I'm not too sure yet, haven't taken the woofer and amp out yet. The cap doesn't seem to be removable from the outside of the speaker. I'll bet they set that at the factory on these specific speakers.

7.62 said:
I'm no help but saw them on the list and almost went after them myself, nice find and good luck on fixing them.

Yeah, they were spelled wrong and had a crappy pic...I almost missed them.

240sx4u said:
I'd suggest just changing those plate amps for newer ones, but M&K may have done something with the circuitry to EQ the sub end. Those are super cool speakers!

I was reading up on that too; I know these are servo controlled woofers, so it might be a proprietary type of amp. Bunch of research to do yet!

Sonance'84 · May 8, 2013

budgetaudio6 said:
The oscillating woofer may be taken care of with changing out the surrounds...They oscillate when teh seal is lost...

I might have been describing the sound wrong, it had a 60Hz hum also that was super loud...made the woofer push out at least an inch or two and blew the foam, which was previously sealed. This was with no signal coming into the amp. I plugged it in for 2 second and immediately unplugged it. I have a feeling it's destroyed.

The other woofer had a nice tear in the foam, but oddly that one worked without trying to destroy itself like the above woofer. I got sound to come through at very low levels, but no oscillation or 60Hz noise.

Anyone have a similar response from an old Volkswoofer? :scratch2:

halo71 · May 9, 2013

Wow...those look awesome! I've never seen them before either.

tonebells · May 9, 2013

I will PM you Ken Kreisel's (K of M&K) email address. He was very helpful when I had a problem with a sub.

Sonance'84 · May 9, 2013

update

I pulled the woofer and part of the amp in the speaker that gave me trouble upon plugging it in. I left the transformer and power supply in place, screwed to the bottom of the speaker.

One thing I immediately noticed on the part of the amp I pulled out was some white powdery reside on the bolts that hold the two amp modules down and on the ground wire for the preamp inputs, corrosion on some capacitor leads, as well as some bulging caps. The internal fuse wasn't blown.

The woofer doesn't have a rubbing voice coil when giving it the push test, despite taking on the weird noise/power I heard when plugging it in. Hopefully I can just have the woofers re-foamed, as long as nothing else is wrong upon further inspection.

budgetaudio6 · May 9, 2013

Try some CRC contact cleaner and a horse hair brush on teh corrosion. Its cheaper tehn deoxit and you just my be able to blast off some of the corrosion. Dont worry about damaging any thing with it. Ive hosed down a circuit board with the stuff before. Just let it dry completely when done. It is fast drying, but can also pool up.

Sonance'84 · May 11, 2013

wmgwizard said:
The picture of the amp plate shows a cap over where the crossover frequency adjustment knob would be.

Is this cap removable ?

Is there a pot behind the cap, or is there no adjustment for the crossover frequency ?

I'm asking be size I just got a Volkswoofer 2b that has a similar setup.

I just remembered to check that cap today...and yes, it is removable with a tiny flathead. There is a small pot underneath it too, which was open all the way.

Once working, these things are gonna take some time to get dialed in just right. :yes:

jazzmans · May 11, 2013

Considering how 'musical' my little MX-70 and SBxx moniters are, I suspect once you figure this out, (those caps look done, btw) you're going to have an amazing pair of speakers.

Hopefully, in twenty years I can afford a used pair of Ken Kreisel speakers.
This man knows his stuff.

Right Now;

an amazing 2013 concert by Madness recorded by the BBC.
http://youtu.be/ZgAFaeUAcjw

tubed · May 11, 2013

I had a pair of SX-4s that would titilate the ears of the 6.5" 2-way crowd:yes:
The pair of pre Volkswoofer, "The Bottom End" subs were a different story. Hard to integrate successfully.
Best of luck to the OP:thmbsp:

wmgwizard · May 11, 2013

Thanks for the info on the cap and pot for the crossover, hopefully it will fix the only issue I have with how the sub integrates with my mains.

The white powdery gunk is corrosion. This speaker was probably used somewhere near salt water. I have seen this many times inside various units living by the NJ shore.

Your hum may actually be caused by a bad connection caused by the corrosion, especially on the RCA input connectors.

The little cap in the pictures looks suspect, probably fairly cheap and easy to find.

Once you get them back together you might not want to adjust the crossover pot. It was set to match with the other drivers in the enclosure. The midrange won't go very low so the woofer is allowed to play a little higher in the frequency range than you might think.

The crossover adjustment is different for a stand alone sub because it must integrate with a wide variety of other speakers with vastly different bass output.

Keep us updated on your progress

Sonance'84 · May 11, 2013

Well, I've got the schematics for sub amplifier...now, as long as the 2 power chips per amp aren't blown, these amps are probably gonna get fully restored.

Also, I measured the ohm on both voice coils of the suspect woofer and it turns out to be ok. The vc's were both 8.2 ohms. There's no vc rub either, so hopefully this woofer is good for a rebuild.

I want to keep these speakers original in design, but I plan on upgrading the parts in the crossovers & amp to higher quality specimen. While the electronics are out, the cabinets will be refinished. Might as well give them the full treatment inside and out, as I have high hopes for these guys.

It's not gonna happen very quickly though because these really were a "find", right in the middle of me being broke. I'll be researching and getting all my ducks in a row for when the time comes to actually get them worked on, which will probably be in July. I'll definitely keep this thread updated with any progress.

Sonance'84 · May 12, 2013

mid/tweet crossover

Looks like some tight quarters on this crossover! There's virtually no room for quality film caps. There's probably enough room to swap a film for that blue cap, but the silver caps are gonna pose somewhat of a challenge in finding replacements that will fit.

Anybody know of tiny quality film caps in these sizes: 8, 16, 18 and 32 uF @ 50V? Also, what are the best electrolytics out there for crossovers? Nichicon Muse ES closest values are 10 and 33 uF, which might be okay to use, since the originals are +/- 20%. But, that would still leave the 16 and 18 uF to find if I stay with electrolytics. I'd really like to go film though if possible.

ZeroG · Jul 17, 2013

Thread's gittin' a little old thar, but...

You should be able to just run leads from the larger film caps to the connections. As long as you glue them down somewhere with hot melt glue they shouldn't rattle, which would be bad for sound as well as connection longevity.

If you have a schema of the XO, then try just replacing the caps to the tweeter with film for now. The larger 32 Uf cap will be expensive and large, and it's probably just used to shunt the highs away from the woofer. So another electrolytic there would probably suffice. The ones to the tweeter will probably show the most dramatic effect if you upgrade to film.

I'm not a XO designer, so hopefully some other AK'ers will chime in.

Oh - and that knob that appears to be lacking was probably designed that way. My V2B sub / sb-1 satellites are the same way - the sub is designed to be integrated with a full range satellite.

Sonance'84 · Jul 17, 2013

ZeroG said:
Thread's gittin' a little old thar, but...

You should be able to just run leads from the larger film caps to the connections. As long as you glue them down somewhere with hot melt glue they shouldn't rattle, which would be bad for sound as well as connection longevity.

If you have a schema of the XO, then try just replacing the caps to the tweeter with film for now. The larger 32 Uf cap will be expensive and large, and it's probably just used to shunt the highs away from the woofer. So another electrolytic there would probably suffice. The ones to the tweeter will probably show the most dramatic effect if you upgrade to film.

I'm not a XO designer, so hopefully some other AK'ers will chime in.

Oh - and that knob that appears to be lacking was probably designed that way. My V2B sub / sb-1 satellites are the same way - the sub is designed to be integrated with a full range satellite.

Yeah, this project got pushed back a little bit...thinking mid-late August is when I'll be getting to them, for real this time.

Update: I'm gonna wait on the crossovers until I get the plate amps rebuilt, I wanna hear them and make sure I like what I hear before I sink more money into them with nice caps. I've actually disassembled both Volkswoofer amps completely (except for the film caps and 1% resistors) and have cleaned the pcbs, heat sinks and plates. I have my parts list made for them with ALL new electrolytics, 1% resistors (to replace the 5%), diodes, rectifiers and gain pots. The amps will be virtually new once completed. The woofer will get new foam from a local expert, which was a referral by another AK member.

------------------------

As for the crossovers though, what was said in the quote above is basically what I ended up thinking of as well. Most of the new film caps will not fit on the board, so I decided to mount them on a piece of bread-board (I like to use RTV instead of hot glue, but same concept), which will then be mounted inside the cabinet with super velcro and solid core wire will run from the cap leads to the x-over pcb. I want to keep the extra cap wire length down, so I'll mount the bread board as close as possible to the pcb.

M&K find...gonna need some help with these

moe.ron

Lunatic Member

Addicted Member

Addicted Member

Infinity nutcase.

Lunatic Member

moe.ron

moe.ron

AK Subscriber

AK Subscriber

moe.ron

Addicted Member

moe.ron

Super Member

Lunatic Member

Addicted Member

moe.ron

moe.ron

Super Member

moe.ron