[Kim S.]

A few weeks ago one of my RM-2's stopped playing.  I described the problem here and John Casler immediately diagnosed the problem.  I had burnt out the midrange L-pads by playing the speakers too loud. (I had been listening to the while in a suanna in another room)  He got me in touch with Brian for the replacement parts.

Sure enough the L-pads were burnt.  Replacement was straight forward,but access was awkward throught the woofer hole.  It was difficult to use both hands to desolder the old connections and solder in the new.  With patience and several breaks I succeeded.

The speakers are up and running and sound better than ever.  Apparently as I was burning up the L-pads the sound was being gradually degraded.  I had noticed something off, but thought it must be a tube  in my preamp was wearing out.


Its great to have the speakers back.  Thanks to John and Brian for all of their help

[Brax]

I think I have the same problem. The FST on one of my RM2 is not working. First I swapped speakers to check the amp channel and that wasn’t it. Then I swapped out the FST between the two speakers and that wasn’t it, so it looks like it’s down to the L-Pads.

Can I jumper between the terminals of the L-Pad to confirm that is the problem?

Since it looks like I will be replacing at least one L-Pad in this speaker, is there a better alternative to the standard L-Pads? I have seen step or ladder attenuator like this one. Would they work as a replacement?

http://cgi.ebay.com/500K-mono-ladder-type-volume-Attenuator-potentiomer-/300506224727?pt=Vintage_Electronics_R2&hash=item45f7911857

[John Casler]

A few weeks ago one of my RM-2's stopped playing.  I described the problem here and John Casler immediately diagnosed the problem.  I had burnt out the midrange L-pads by playing the speakers too loud. (I had been listening to the while in a suanna in another room)  He got me in touch with Brian for the replacement parts.

Sure enough the L-pads were burnt.  Replacement was straight forward,but access was awkward throught the woofer hole.  It was difficult to use both hands to desolder the old connections and solder in the new.  With patience and several breaks I succeeded.

The speakers are up and running and sound better than ever.  Apparently as I was burning up the L-pads the sound was being gradually degraded.  I had noticed something off, but thought it must be a tube  in my preamp was wearing out.


Its great to have the speakers back.  Thanks to John and Brian for all of their help

Hi Kim,

Glad that solved your problem, and it is far less expensive (although a bit more involved) to replace an L-Pad than a driver.

The L-Pad is a resistive device, and the the more you "open" it (turn it clockwise) the less resistance.  The more you close it (turn it counter-clockwise) the greater the resistance. 

It is also sensitive to clipping and if exposed to continuous clipping it will begin to heat up.  If it is exposed to these wave forms too long and especially if it is closed down (less than say 9:30 or so) it can cause a problem.

So while the RM2s can play quite loudly when you are in the room and particularly in the sweet spot (due to the soundfield focus), they don't do as well in extreme PA applications.

Maybe we should get you another pair of RM2's to place just outside of your Sauna   That would give you all the sound you want and only YOU would heat up

[John Casler]

I think I have the same problem. The FST on one of my RM2 is not working. First I swapped speakers to check the amp channel and that wasn’t it. Then I swapped out the FST between the two speakers and that wasn’t it, so it looks like it’s down to the L-Pads.

Can I jumper between the terminals of the L-Pad to confirm that is the problem?

Since it looks like I will be replacing at least one L-Pad in this speaker, is there a better alternative to the standard L-Pads? I have seen step or ladder attenuator like this one. Would they work as a replacement?

http://cgi.ebay.com/500K-mono-ladder-type-volume-Attenuator-potentiomer-/300506224727?pt=Vintage_Electronics_R2&hash=item45f7911857

First take a flashlight and examine the ribbon and see if it has any damage or tears.

If none are found, then while playing some music with high frequencies, turn the shaft on the L-Pad all the way from one stop to the other.

If you burn an L-Pad, it is generally in but a single spot (unless you have REALLY exposed it to some high clipping current for an extended period ) and turning it to another setting will create contact again and then complete the circuit.

Also be sensitive to how it "feels" when turning it.

First familiarize yourself with what a non-damaged L-Pad feels like, by turning one of your good ones.  It will feel smooth from one stop to the other, and you will only feel the small "bumps" (windings) as it turns.

If it feels sticky, of rough and the sound cuts in and out, you have burnt it.

You can also open up the speaker by removing the woofer, and take a good look at the L-pad.  Normally it will show heat related discoloration on the outside (while I have only seen 3 of these, they all "looked" burnt.

If it feels normal and looks normal, remove all the fiberfill around the crossover parts and look for the same "heat related" discolorations on any XO parts.

Brian may be able to offer additional instructions and clarifications, since I am not a speaker builder, and don't have a lot of experience with repairing them since they seldom fail unless they meet some "extreme" conditions.

[John Casler]

Sure enough the L-pads were burnt.  Replacement was straight forward,but access was awkward throught the woofer hole.  It was difficult to use both hands to desolder the old connections and solder in the new.  With patience and several breaks I succeeded.

Hi Kim, and anyone else who may at some time need to replace the L-Pads.

Remove "both" the bottom woofer AND the Passive Radiator.  This allows you to get both hands inside more easily, and it gives you more light.

As a hint, I also suggest a fan blowing on you unless you like inhaling soldering fumes.

With both the Woofer and the PR removed, you can also even place a light right inside the cabinet for better visibility.

[Brax]

John,


The Ribbon is fine and as I said, I swapped out tweeters and the original one from the bad speaker plays fine in the other speaker.

I have elimintated these are potential problems
1) Amp Channel
2) FST tweeter
3) Jumpers on the binding posts

The L Pad seems to run smoothly when I adjust it but it makes no difference in the output of the tweeter. I would like to either eliminate the L Pad or identify it as the problem. I thought if I could jumper past it I could see if that is the problem of it is somewhere in the crossover. I actually hope it's the L Pad, I have a spare and it probably is the easiest thing to fix.




I assume if I jumper between terminal #3 (positive to tweeter) and terminal #1 (negitive from tweeter) you would bypass the L Pad. At that point if the tweeter was working, it would confirm the L Pad was bad.

[John Casler]

John,


The Ribbon is fine and as I said, I swapped out tweeters and the original one from the bad speaker plays fine in the other speaker.

I have elimintated these are potential problems
1) Amp Channel
2) FST tweeter
3) Jumpers on the binding posts

The L Pad seems to run smoothly when I adjust it but it makes no difference in the output of the tweeter. I would like to either eliminate the L Pad or identify it as the problem. I thought if I could jumper past it I could see if that is the problem of it is somewhere in the crossover. I actually hope it's the L Pad, I have a spare and it probably is the easiest thing to fix.




I assume if I jumper between terminal #3 (positive to tweeter) and terminal #1 (negitive from tweeter) you would bypass the L Pad. At that point if the tweeter was working, it would confirm the L Pad was bad.

Hi Brax,

I have never had a tweeter L-pad fail.

The only L-pad I have had fail were on the NeoPanel MR.

It is my understanding of your situation then, that moving/twisting the tweeter L-pad shaft when music is playing leads to NO tweeter output at any position?

If that is so, and it is not discolored and turns freely, it doesn't sound like an actual L-pad failure due to being over driven.

I know Brian received a bad batch of L-pads a few years ago that failed due to a manufacturing defect, but I don't know how extensive that was since I only heard of a couple failures in the field.

Sounds like "Big B", is the go to guy on this one.

[Brax]

Well I replaced the L Pad for the tweeter today and it did not fix the problem. The tweeter plays but very softly. I checked the wires to the tweeter to be sure I was changing the right L Pad. I looked over the crossover and the connections and everything looked good. Is there someway to check the crossover parts? Or should I just order new ones?

[Brian Cheney]

Sounds like an open tweeter cap to me.  What kind do you have?

[Brax]

I think these are the stock caps. On the tweeter There are two white, two orange and a black.

The tweeters are FSTs.

[Brian Cheney]

Email me your address and we'll send you a replacement treble cap.

[Brax]

I sent my address to the VMPS aol email.