VMPS RM V-60 Mystery

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OldScott

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VMPS RM V-60 Mystery
« on: 7 Dec 2020, 09:15 pm »
In the past I have always used an Ambrosia preamp in my system. With my RM V-60 speakers it was necessary to set the balance control at two increments of gain for the left Chanel. Not much and no big deal - right? Some time back I had to send the preamp to Wyerd4Sound for repair and in the interim began to drive my speakers directly from my Cary DMS-600 DAC. As good as the Ambrosia is I found connection to the DAC gave slightly better sound quality, however now I had no control over balance and the sound field seemed to be centered a foot or so to the left of center. Nothing terrible but very annoying none the less. So for help I turned to my good friend Dave Housteau, who along with myself owns one  the first two RM V-60's. With Dave's help to trouble shoot I found to my aghast that that the left tweeter was totally dead. On ordering a replacement I found they were on a three week back order!  Finally upon arrival when I installed it I still had no sound. So back to Dave. We next  checked for poor connections, interconnects, speaker cables, banana plugs, jumper cables, and about everything under the sun to no avail. Dave spent hours texting what ohm meter readings to check for on various connection points. This led to the discovery of different readings on the two crossover boxes. Then Dave suggested I switch the outboard crossovers. Lo and behold, now the off balance of the sound field shifted to the other side. At this point we had no choice but to look inside the crossover box. The culprit was a broken internal connection of a jumper wire to a L-pad. Easy fix. I soldered it back on, closed everything up, and powered up my system. BUT still no sound from the tweeter.  Assuming I had a bad L-pad I wired around it, taking it out of the system. That ended up being an exercise in futility as I STILL had no sound from the tweeter. So again I go back to Dave who after staying up half the night looking at filters, crossover plans, generic crossover schematics, etc,  came to the conclusion that the L-pad provided a needed resistance to the circut. He suggested I return the crossover to its origanal state while he figured a functional method of taking it out of the circut until we could get a replacement. This I did and returned the crossover to my system so I could at least play my system sans one tweeter. To my absolute astonishment now both tweeters played. The only conclusion I can come to is that I must not have gotten a good solder job  done when I first attached the broken wire or that Dave's earlier suggestion to rotate the shaft of the L-pad numerous times to potentially clear any accumulation of corrosion was what did the truck. A final thought is that that wire may have become disconnected in shipping several years ago and by adjusting the balance control on the preamp I just never detected it. Anyway all is now well and the lesson learned is:  If at first you don"t succeed , don't give up --  JUST CALL DAVE!
           

John Casler

Re: VMPS RM V-60 Mystery
« Reply #1 on: 7 Dec 2020, 09:23 pm »
Hi Paul,

As long as that history was, it still didn't include the other X-over we were trying to sort out.

Next time we need to call Columbo. . .  :lol:  In this case Dave is Columbo

Was just thinking (not a good thing) did you adjust or move the L-Pad knob?

It is always possible the in moments of high SPL episodes that the wiper actually got burned and moving it to a position of contact will do the trick too.

OldScott

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Re: VMPS RM V-60 Mystery
« Reply #2 on: 7 Dec 2020, 11:41 pm »
Hay John,  I think both crossovers were working when you visited. My best hunch is that there was a dual issue. I think the wire got broken when we moved about a year after you were here and I think there may have been corrosion on the L-pad which got rectified after I rotated it 50 or 60 times as Dave suggested.  Or maybe just maverick electrons and/or gremlins -- who knows?

GeorgeAb

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Re: VMPS RM V-60 Mystery
« Reply #3 on: 8 Dec 2020, 06:10 am »
Congrats on getting it sorted!




Stimpy

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Re: VMPS RM V-60 Mystery
« Reply #4 on: 8 Dec 2020, 02:40 pm »
Well, at least you knew you were hearing an issue.  Too funny, how we'll listen around anomalies, instead of tracking down the root cause.  Regardless, I'm glad that Dave helped sort out those 60s.  Too good to waste.

Also, this just highlights the fact that I wish we had better VMPS documentation here at AC.  Wiring diagrams, schematics, or even pictures of wiring and crossovers would help.  Any thing to support Brian's creations, for future owners.

shauk786

Re: VMPS RM V-60 Mystery
« Reply #5 on: 8 Dec 2020, 02:49 pm »
Glad that everything is sorted out.

I am also in the process of reassembling my V60s. Let's see what happens at the end. But thank to god, there is Dave, Ken and George.

Cheers.

OldScott

  • Jr. Member
  • Posts: 66
Re: VMPS RM V-60 Mystery
« Reply #6 on: 9 Dec 2020, 06:00 am »
Stimpy I also wish there were better documentations here. With most speakers the hookup is self evident, even tri-amped ones typically only have three inputs - treble, mid and bass. But not the RM V-60's for with them you almost need an EE degree. As a case in point: each V-60's pedestal  with it's  outboard crossover has 7 sets of 2 binding posts, 3 sets of twisted two wire cables terminated with circular lugs, two sets of jumpers with circular lugs, and one set of jumpers with banana plugs. Hardly seems enough! Of these, in my set up at least, one set of binding posts, two twisted two wire cables, and one set of jumpers are not used at all. On receipt of the speakers many of my binding post labels were missing providing me an added challenge. For all I knew my refrigerator was supposed to plug in there somewhere. Fortunately I was able then to call Brian, but sadly no more. Additionally there are slightly different ways to hook things up, for example Dave and I have connections that physically differ but are electrically identical. Also Dave and I initially had some communication difficulty in working on my problem. Not all of our hook up wires were with same color. I could ask him about a blue wires hookup only to  find his was green. To finally resolve my problem I had to open up both outboard crossovers and also Dave emailed me a picture of the insides of one of his. I was aghast to find that none of the three were physically identical
however they were (once mine was finally restored) functionally identical.  Bryan was so innovative that he was able change things around and yet end up accomplishing what he wanted. So again I agree it would be nice to have some repository of technical details on his work

All of this has brought back a lot of fond memories of this incredible man.There is one incident i shall never forget. I think it was the first time Dave and had volunteered to help him and others with setting up. It was at the Alexis Park, we were just finishing setting up a large room, and Brian was powering up his equipment. As he did so he looked across the room to where someone lad left a very large glass vase against the far wall. With a soundtrack playing he said "Get that glass thing out of there" I don't remember who, it was Dave or John who did so only to hear Brian say "Wait put it back". And then, "No, move it three feet to the right",  to be followed by"Now halfway back to where it was"  Admittedly, everything's location in room has some effect on sound, but a vase on a far wall! John Casler could have come in carrying a refrigerator (which I think he could under one arm) and placed it down there and I wouldn't have been able to detect a change in sound! Brian had to have one of the best sets of ears in the world.