Hey all,
this might be the wrong forum for my question. Please excuse if this is the case, and I'd be happy if anybody could point me to a forum that would fit.
My old stero (Pioneer A337) "snapped" the other day, the volume was suddenly much lower and somewhat distorted. I brought the stereo and the speakers (Canton LE107) to a local repair shop that is also repairing electronics. That was a mistake - the guy in the shop said that he couldn't fix it so he "disconnected the bass" (he didn't speak much English and I couldn't find out more) so that I can "enjoy the rest of the speakers". Indeed there was no bass left at all when I got it back and it sounded horribly.
I am now trying to figure out which parts need replacement. Unfortunately I don't have access to a second set of speakers or stereo in my exile in London, so I can't directly test in which there is the problem. The sound and bass is fine in the headphone jack of the Pioneer, so I concluded that the speakers must be faulty (if that reasoning makes sense). But then it seems unlikely to me that both woofers in both of the speakers are broken.
I opened the speakers - all cones seemed fine, and while one cable to one of the woofers was loose, reconnecting it did not bring the bass back. Would anyone dare a guess where the friendly man in the shop "disconnected the bass" so that I could at least try to find out which of the woofers needs replacement?
Thanks for any help!
Jan
this might be the wrong forum for my question. Please excuse if this is the case, and I'd be happy if anybody could point me to a forum that would fit.
My old stero (Pioneer A337) "snapped" the other day, the volume was suddenly much lower and somewhat distorted. I brought the stereo and the speakers (Canton LE107) to a local repair shop that is also repairing electronics. That was a mistake - the guy in the shop said that he couldn't fix it so he "disconnected the bass" (he didn't speak much English and I couldn't find out more) so that I can "enjoy the rest of the speakers". Indeed there was no bass left at all when I got it back and it sounded horribly.
I am now trying to figure out which parts need replacement. Unfortunately I don't have access to a second set of speakers or stereo in my exile in London, so I can't directly test in which there is the problem. The sound and bass is fine in the headphone jack of the Pioneer, so I concluded that the speakers must be faulty (if that reasoning makes sense). But then it seems unlikely to me that both woofers in both of the speakers are broken.
I opened the speakers - all cones seemed fine, and while one cable to one of the woofers was loose, reconnecting it did not bring the bass back. Would anyone dare a guess where the friendly man in the shop "disconnected the bass" so that I could at least try to find out which of the woofers needs replacement?
Thanks for any help!
Jan
I tried to find some info on this speaker, but nothing in English.
It looks like an MTM but it could be a 2.5 way?
If he disconnected the woofers, there sure would be missing some bass
Thanks for your answer! Information on the speakers can be found here, LE 107 - CANTON German loudspeaker tradition (en) - it says "2½-way Bass reflex system".
I took a look at the crossover, as you recommended - the cables are however all connected. Is there any other element of the crossovers that I would need to check? Everything seems to be soldered to the circuit board, with the exception of the inductors (if that's what the things consisting of copper coil are) which seem to have some clip on mechanism.
Too bad that I don't even know if the problem is with the speakers or the stereo. If you think it is more likely the speakers then this is already valuable information though!
Well, I can't think of how he "took the bass out" without disconnecting it somewhere?
I don't see how it could be the amp or receiver, its just 1 set of wires to each speaker right?
Maybe there is some bass management on the amp that he could have defeated or turned down?
Is there any noise coming out of either woofer, or only the tweeter.
I don't see how it could be the amp or receiver, its just 1 set of wires to each speaker right?
Maybe there is some bass management on the amp that he could have defeated or turned down?
Is there any noise coming out of either woofer, or only the tweeter.
I think he said that it happened to both speakers at the same time.
That's weird huh?
And what did this repair man do?
Remove components on the board?
I don't think he would do that? (to take the bass out)
Jeez, this is painful to read. Sounds like a 2.5 way speaker to me. Bass, mid, treble.
You need to do some testing. First take out the drivers (having made a note of what wire goes where...) and see if you get any sound with a 1.5V battery and two paperclips...
If all well and good, look for a break on the crossover wiring. Nothing stopping you testing the amp with a bass unit and some improvised wiring either. Don't try that with a delicate crossoverless tweeter though.
Bit odd that both units failed at the same time. Whatever is going on?
Mending speakers: mending things: Kef Cresta speaker renovation
You need to do some testing. First take out the drivers (having made a note of what wire goes where...) and see if you get any sound with a 1.5V battery and two paperclips...
If all well and good, look for a break on the crossover wiring. Nothing stopping you testing the amp with a bass unit and some improvised wiring either. Don't try that with a delicate crossoverless tweeter though.
Bit odd that both units failed at the same time. Whatever is going on?
Mending speakers: mending things: Kef Cresta speaker renovation
Attachments
I didn't find any foil, and the capacitors seem fine to me. Thanks for the tip though, Rudolf!
Good, that will be interesting. I will try and report when coming home tonight. Thanks Steve!
Yes, good idea. Here are some (somewhat blurry) first pictures of the crossover board that I took this morning before leaving the house. I will post better pictures tonight!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I'm still trying to determine from your first post if the 'repairman' did something to the speakers or the stereo itself. It sounds like you took both.
It is possible there is nothing wrong with the speakers. Seriously, if I was in your place I would search out another pair of speakers to connect to the stereo to try to determine if the problem is with your speakers or your stereo. The speakers don't need to be quality at all - they could be cheapo thrift shop specials, bought simply to see if any bass is coming out of the stereo.
The thing that sticks in my mind is that the bass quit in both speakers at once. A power supply problem in the amp would do that. If your stereo has a bass tone control all one would have to do is wire appropriately at the back of the control to effectively eliminate the bass - though why anyone would think of that as a repair is beyond me.
My two cents.
It is possible there is nothing wrong with the speakers. Seriously, if I was in your place I would search out another pair of speakers to connect to the stereo to try to determine if the problem is with your speakers or your stereo. The speakers don't need to be quality at all - they could be cheapo thrift shop specials, bought simply to see if any bass is coming out of the stereo.
The thing that sticks in my mind is that the bass quit in both speakers at once. A power supply problem in the amp would do that. If your stereo has a bass tone control all one would have to do is wire appropriately at the back of the control to effectively eliminate the bass - though why anyone would think of that as a repair is beyond me.
My two cents.
I'm trying to wrap my brain around this. Could you elaborate a bit? For the life of me, I can't think of a power supply problem in an amplifier that would make the woofer driver in a speaker system stop functioning but leave the rest operational.
It's just a theory, of course, but a transistor amp is current driven. Let's say say something happened to the output power supply so that when current was demanded it simply ran out of gas. Perhaps losing just part of a bridge rectifier might do it, or a defective pass transistor in a linear regulator - or any number of other reasons.
So, in a quiescent state the power supply may be able to put out proper voltages. Most of the energy in music is in the bass, so I think it is possible that a power supply with this problem may put out a watt or so, enough to carry the higher frequencies, but the instant bass was attempted would not only not power the bass, but as a result would sound distorted as well as the voltage regulation collapses. The headphone output is most likely tapped off before the amp output, so would not be affected.
Like I said, just a theory, but I think determining just where the problem lay first with certainty would be prudent...
Last edited:
Ah, now that I could understand, if the problem occurred on a varying scale while raising the volume.
I'm a fan of the simplest test though, pull out one of the woofers and see if it'll move with a AA battery.
I'm certainly not against that test. I suppose I'm just the type to not mess with something I might mess up - having me with a screwdriver in my hand near a speaker cone I highly value always makes me nervous!
Perhaps with some coaching we can get jstlondon to describe the symptoms in more detail - he doesn't seem to have done a lot of troubleshooting.
I ported a woofer once with a cordless drill, haha. Now I always use short hand screwdrivers that I can get almost entirely in my hand.I'm certainly not against that test. I suppose I'm just the type to not mess with something I might mess up - having me with a screwdriver in my hand near a speaker cone I highly value always makes me nervous!
Yeah.
Sounds like something I should get!
But, just as you say, the battery test will tell if the woofers are working, at least.
This is my guess as to what the repair guy did, just pull one of the wires from the woofer in case it was blown and presented a short to the amplifier. Headphone jacks, AFAIK, are usually driven by a small OP amp that's fed from the gain stage of the amplifier, so if a shorted woofer welded something inside the amplifier, the headphone output would be unaffected.
www.LJclub.net
It's not one of those blob ICs, but who knows. If something in the amplifier "snapped" (was there a smell or some smoke?) it's most likely dead, or mostly dead.
He's already had the woofer out to reconnect it (reverse what the repair guy did), so it shouldn't be too difficult to test it.
Oh, also for lafeEric, these are great.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.