September 27, 2020 at 10:45 am #524
Dear all SL users
My left M545 speaker (a couple of years old) started getting quieter yesterday and by the end of the day made no sound. I have switched around the speaker cable, amp posts, fuses and AC source and it is always the left speaker. What is most likely to go wrong in this young speaker? I sent an email to Roger West and am waiting to hear back but I thought I would reach out in case some of you had similar experiences. I have been playing music a lot these past few days (5 hours/day) via Pass Labs X250.5.
September 27, 2020 at 10:50 am #525yoshiParticipant
As an additional check, switch the backplates and see if stays with the channel or not. This will confirm a back plate problem.
If its a backplate issue, will likely require a send back to Roger for investigation.
September 27, 2020 at 11:23 am #526
Can you turn up the bias, and do your hear the crackles? If not, likely the bias circuit went and needs to be replaced.
Switching backplates is dead on for a suggestion. If it follows the backplate, you know what went wrong.
I have a pair of M645s that are coming up on two years old, and this concerns me every time I use the speakers.
Frustrating that a speaker company that is four decades old and charges this much has this problem.
I’ve heard this happen to other people.
I can buy a pair of MLS from Best Buy that last 10 years.
Two years for a backplate is pretty poor.
Please let us know what you find out.
September 27, 2020 at 11:49 am #527
Now I am really confused.I switched the backplates and the left speaker (now with right plates) played music quietly for a few seconds and then died. Now neither speakers are making any sound. Both speakers crackle with the bias turned up. I forgot to mention this, but yesterday the left speaker died first and then the right speaker died too. So, yesterday I thought it was the amp. So, this afternoon I turned on the system again and only the right speaker worked, so I thought it wasn’t the amp but the left speaker. Now I am thinking that it may be the amplifier with unstable output transistor or something like that. What do you think?
September 27, 2020 at 11:59 am #528
That is bizarre.
How old is the amp? Do you have a spare to try?
Preamplifier? I had a preamp do the same thing a year or so ago.
I would start from the speaker back. Try and get a spare amp to test. Maybe pick up a Crown from Amazon or Guitar Center to try. They are cheap, like 200-300. Might sound terrible, but will let you know the problem.
If it’s not the amp, work backwards.
Is the amp bias meter acting funny?
Do you have a tube preamp?? Could be bad tubes?
September 27, 2020 at 12:14 pm #529D10Participant
Your problem is amp – not speakers
September 27, 2020 at 12:21 pm #530
I have an old Pass Labs X250.5 that was refurbished by Pass Labs 4 years ago. Amp bias meter is acting funny. When I play Bach prelude cello sonata by Jonas Starks and on sustained low note the bias needle moves noticeably. Not anymore. What threw me off is that the two channels act differently from one day to another. I bet tomorrow, the right channel will work for a while and then die.
September 27, 2020 at 12:30 pm #531Loudspeaker7Participant
It would be very unusual and odd that both speakers failed at the same time. Probably something else unless a failure somewhere else took out the speakers.Your amp is quite powerful and capable of doing damage if out of control.
September 28, 2020 at 10:56 am #533NolafileParticipant
I doubt the amp would have any bearing on the bias supply’s. Which you should be able to dial up to where the panels are crackling. Even without a amp hooked up. I’m guessing by the mid point on the adjustment you should hear something. If you don’t hear anything then it sounds bias supply related. As to why both would checkout within a small window of time. I don’t have an explanation for that unless the panels have somehow lost connection or conduction. So what compound was used on these to make the film semiconductive? I’m assuming it is not graphite like my older model.
I’m assuming the bias supply’s are always energized. So do you monitor the a/c line voltage and or run a conditioner? Perhaps for some reason the voltage went high. It might be a good idea to comb thru the house wiring for suspect connections. An example being weird things start happening when a neutral connection goes high resistance.
September 28, 2020 at 11:00 am #534
I confirmed that biases on both speakers work. They both crackle when dialed up. I have a new Pass Labs X250.8 coming later this week. That should tell us whether it is the amp or not. Thanks to everyone for pitching in. I will post after testing with the new amp.
September 28, 2020 at 11:13 am #535NolafileParticipant
Sorry I missed you stating they are actually crackling.
In my case the input resistors had cooked which also cooked the surrounding connections. All of which increased the input Z causing reduced output. But if this were the case you would likely detect a burnt smell. So that’s doubtful.
Perhaps disconnect the amp and check for output voltages. Both a/c or dc. If you detect over 30mvdc or any a/c at idle send it to be serviced. Stats don’t like much dc offset. In fact as close to zero is always perfered.
If it passes that then ring out you speaker wiring to make sure they are faultless. Perhaps the amp is having issues with the automatic transistor biasing circuits. And is dialing down into limp mode.
October 5, 2020 at 1:11 pm #540
October 5, 2020 at 1:26 pm #541
Here is the update. I put in a new Pass Labs amplifier and still no sound, so I though it was SL. Then as I was walking by SL, I accidentally hit the speaker cable and sound came on from both speakers. What I think happened is this. Previously, I mistakenly connected the red terminal to -, rather than +.So I reversed it to correct this error and, in retrospect, problems started after that. I didn’t suspect this because they were on pretty tight. But after the switch, the spade-terminal contact must not have been very good-probably the angle of it was a bit off when I reversed them. Roger West thought it was the safe mechanism on the amp. I feel like an idiot, but it is a warning for those of us who now use these stiff python-like speaker cables. You think they are on tight because the bolt feels tight but you are not getting good contact.
October 5, 2020 at 2:07 pm #542John VParticipant
That’s great, glad to hear it!
Been there, done that.
I’d much rather feel like an idiot than:
1. Have a bad panel/supply that needed to be returned and repaired.
2. Return the panel/supply only to find out there was no problem
My rule of thumb, check the simplest most obvious items first
even though I think, “NAH, it can’t be that” ;))
Enjoy your system!
October 5, 2020 at 2:19 pm #543D10Participant
Great news! I knew that new SL are more reliable than new Pass electronics. 😜
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