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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I have a BeoLab 8000's (Mark I), having functioned properly for quite a while.
Since recently the overall sound has changed. The speaker produces s shrill sound. It sounds like it's missing the low/bass. The other speaker still sounds normal, so I can clearly hear the difference.
What I have checked:
Does anyone have a suggestion for what the cause can be, and what to do for solving this issue?
Do the woofers on the shrill speaker put out any sound at all? Or do they and it's just a lot lower in output?
Jeff
I'm afraid I'm recovering from the BeoVirus.
Thnx for responding Jeff!
The woofers both do produce sound. Volume is good but sound is shrill.
By the way, I found a lot of old foam sticking to the amp’s pcb. I cleaned that all using isopropyl. Unfortunately that made no difference. Any suggestions?
From what I've read here the foam can cause corrosion of the PCB traces and shorting or open circuits. Usually that causes the amp to just stop working, but I'm sure it can also cause other issues. I worry about this on my late 90's BL8000s but they so far work and I haven't gotten around to replacing the foam. Probably tempting fate.
Is the tweeter level right? That is, is the tweeter output on the shrill speaker about the same as on the good one? I usually test this by putting on pink noise, or tuning the FM tuner to inbetween a station with the muting turned off so you get the hiss. Easier to tell than with music. Also a good way to listen to the woofers on each speaker for tonal differences, that show up pretty well with the hiss of noise
I'm betting you'll need a service from someone who knows the amps, but it'd be good to diagnose it. Hopefully Dillen or one of our other experienced members will weigh in.
How old are your 8000s? Are the old enough that the two woofers are not hooked up the same, or the slightly later thru modern ones where both woofers output the same freq range? Could be damage to the electronic crossover, or even one woofer not working. Wish I could help more.
Thnx again Jeff!
I did exchange the upper woofer speaker (mid tone speaker) for a different one, but that did not make a difference.
Hmmm. If I recall, wasn't one woofer run with a capacitor inline on the amp output? Could that have failed? Do you get sound out of both woofers? I could see it sounding shrill if one woofer that produced only bass was missing in action. Is it shrill as in a problem with frequency response, or is there distortion in the mix as well?
Interesting problem. You are getting sound out of the bass only woofer? Also, I believe that the 8000 is like the other Beolabs in that when you change a driver you need to readjust the output level to the speaker with the little trim adjustments. To make up for differences in the efficiency of different drivers. Could this be something relating to this?
Thanks again for sharing your suggestions Jeff.
I will look for the capacitor on the amp output connected to one of the woofers.And also I will look for the little trim adjustments.Concerning freq response and distortion, my response is based on the definition used by SoundGuys (https://soundguys.com/frequency-response-explained-16507/). What I notice is that both woofer speakers produce sound. In the Mark I series of the BeoLab 8000, the lowest positioned speaker is the bass speaker, and the speaker right above (which is physically the same as the lowest positioned speaker) is used for mid-tone.What I think I hear is a non-flat freq. response, in which the 'low' seems not be amplified.
Does this info help you?
That could be either the amp, the ABL system, the driver itself, any of a number of issues. I guess if you swapped the drivers, temporarily, you could eliminate the actual driver. Say, from the upper to the lower one, or from one speaker to another. Try and remember where each one was originally or you'll need to rebalance the whole system. The service manuals are online here at Beoworld for silver or gold members. The manual should have instructions for setting levels for each speaker driver, I know the manual for the BL6000 I have does.
Kind of a head scratcher, I have been hoping one of our more hands on technical guys here like Martin or such would see this and chime in.
Another thought, have you switched the powerlink cables around so that the bad speaker is hooked up in place of the other channel? Swap L for R and all to make sure it's not a problem with the source unit, whatever that is (I use a BS9000).
Thnx for your thinking and suggestions again Jef, very much appreciated!
Drivers:
I believe we can conclude that the problem is not in the drivers.
L & R channel switch:
I changed the Left channel to Right and vice versa, several times. And trying this with different kinds of music with bass. Result; it is very clear that in all situations, the same BeoLab unit keeps producing shrill sound.
Next
I am now going to check the capacitor (on the amp output connected to the lower woofer).
I doubt it'll be the cap, but doesn't hurt to check. And, even though using the switch should be enough to tell, I'd also make sure to plug the speaker into a completely different Powerlink output socket on whatever you're using as a music system for them. Even try a different system if possible. I doubt that's it, but I've been fooled before with such things.
I'm the kind of person who will take a unit that won't power on apart to fix it before I check to see if it's even plugged into a working outlet.
Jeff:I'm the kind of person who will take a unit that won't power on apart to fix it before I check to see if it's even plugged into a working outlet.
That's so "all of us" here!
It makes your wife look like a Nasa engineer by just saying "did you only check the batteries"? (unless she's actually a Nasa Engineer…)
matador43: Jeff:I'm the kind of person who will take a unit that won't power on apart to fix it before I check to see if it's even plugged into a working outlet. That's so "all of us" here! It makes your wife look like a Nasa engineer by just saying "did you only check the batteries"? (unless she's actually a Nasa Engineer…)
Heh. And I'm a retired aerospace engineer! Believe me, we might be even more inclined to assume it's something complex and dig in rather than check basics first.
Its because WE WANT to open that damn thing and see by ourself what dark magic moves that 50.000$ loudspeaker!
Thnx Jeff!
Good suggestion to plug the speaker into a different system. I did. I checked:
All of these checks resulted in the same: shrill sound.
Two questions:
I meant your using the L/R switch on the speaker. That should be enough, but it's always a good idea to actually swap cables just in case.
I don't think the cap will be a problem, but who knows. If the drivers work when swapped, I'm thinking it has to be a problem with the frequency response or distortion in the amplifier, which means pulling and repairing it. The fact that the foam was an issue makes me suspect damage from the foam, but from what I read here usually the damage is more severe, killing the amp outright.
As I have a later pair of BL8000s of course I'm quite interested in how this turns out and what the diagnosis turns out to be.
Thnx Jeff.
I'll know about the cap pretty soon.
The drivers have been checked thoroughly, including the channel and music source swapping. No issues there.
If it is a frequency response/distortion issue on the amplifier, where would you suggest to start?
Well, if it were a normal amp I'd put it in the bench, hook it up to a 8 ohm power resister as a load, put sine waves of verious frequencies into it and see if the response was flat by measuring voltage across the resistor. For this, I'd probably put a meter across the speaker terminals for the woofer (you'd probably have to do each and compare to the speakers in the one that works), and put sine waves into the RCA input on the speaker. For distortion, since I don't have a distortion analyzer, I'd put a scope across the terminals and look at the waveform to see how fuzzy it looks. I have been using a little app for my iPhone called "AudioTools" for a lot of this kind of stuff. It will generate sine waves, pink or white noise, and output it via the headphone jack. I use a mini-plug to RCA adaptor. It also uses the microphone of the iPhone and has an SPL meter and a spectrum analyzer. Granted the mic is not calibrated or linear, but one approach would be to feed pink noise into the good speaker and the bad speaker, hold the phone at the same place relative to each speaker, one at a time, say a meter away on axis at the woofer/tweeter level, and see if they looked different. If you use say a digital multimeter be aware most are not linear either, they roll off as freqency goes up unless they are a good, usually more expensive, one. Now, what to do with what this shows, depends. Amp problem? Crossover problem? ABL problem? Most likely amp I think unless the active crossover is dropping the level of the woofers or such.
I need help of a friend to make this kind of checks.I hope to do that over the next two weeks.
Will come back to this thread to share the results.
Jeff, here's some more input what I found out.
As said before I tried to change the woofer drivers. But this did not make any difference.Also I changed the tweeter driver for another one. But this also made no difference.
Now I noticed something strange. If I take out the tweeter driver, without replacing it with another tweeter driver, the normal bass sound is back and the shrill sound is gone.And as soon as I connect the tweeter driver, the bass sound is gone again and the shrill sound is back.What do you make of this???
The only thing that pops into my mind is that the tweeter level is way off or it's got some distortion. Since you've swapped tweeters it'd have to be in the crossover or amp. I'd shove something like a 5 KHz or such signal into the speakers, something up in the tweeter range, a sine wave, and measure the voltage across the tweeter on the good speaker and the bad one to see if they were different. If they're the same, something really weird is going on in the electronics I can't fathom.
You do seem to have the most interesting problems!
Thnx Jeff! I'm not sure if I like to have the most interesting problems ... but hey, let's call it a challenge. ;-)The BeoLab just is a too beautiful product to put it aside.
Thanks also for your new suggestions Jeff. I will try to put a 5Khz signal into to speakers.
I must say, I'm a bit dazzled by the fact that the bass is back in the 2 lower speakers and the shrill sound is gone, when I take the tweeter driver out.But that the bass is gone and the shrill sound back when the tweeter driver is connected again.
Sounds like the physical tweeter driver connection is triggering both the bass to disappear and the shrill sound to appear.
???
I suspect something is going on in the electronics that's not easily to diagnose without pulling the whole electronics package and putting it on the bench. I think, sadly, you've about exhausted what you can look at yourself and perhaps it's time to throw it at a repair tech.
The best you can do I think is, since you have one working speaker, is to measure and test as many things as you can where you can compre one speaker to the other, and hope for luck in finding something different that you can trace to a fault. Not always easy though.
And yes, they are too beautiful and iconic to abandon. I listen to mine every day.
Did you manage to fix your speakers? Would be curious to know what the issue was?