View Full Version : What can make a speaker vibrate (buzz)?
The bass driver on one of my speakers is vibrating. Certain piano notes are the chief culprits. It does not happen all the time but certain frequencies or sounds result in a distinct buzz. The driver is 15inch and in a Goodmans Magister . I posted a thread a little while back on the repair of them when they were over driven at Christmas. I can't find the thread, but the repair involved sanding down the inside of the voice coil former which was scraping/jamming against the magnet. I thought the repair was successful but now this vibrating has started. When I push the cone there appears to be no scraping what so ever and it moves freely. Has anyone any ideas as to what could make the driver buzz?
It sounds like the voice coil rubbing, which is what the repair you did previously was attempting to correct. Over time gravity can make the cones sag which causes voice coil rubbing. You could try turning the unit so that what is now the bottom is at the top to see if this makes any difference. If you think about how long they will have been in their current position.......
I did that with a set of 12" ones and it solved the problem
Thanks for the replies Rob and Grant. Sorry, I should have said I've tried turning it upside down. The obvious thing is rubbing. Is it possible for this to happen but to feel no rubbing or scraping when you push in the cone?
usually you would feel something. doesnt have to be much. Drivers might just be old; happens with some really big uns. Geoff might be more help but is on hols at moment.
Thanks Grant. Seems to be totally free when I push on it. Very frustrating as I thought I'd sorted it out with the repair. I wrecked both of them at Christmas but only one is playing up. I don't really want to open them up again.
Likely (clearly) the Overdriving did More damage than a rubbing voice coil, which was just the most obvious manifestation.
Buzzing is often from a tear// possibly where the voice coil former attaches to the Cone.
Rubber cement can be a reasonable repair, in the interim at least. to test/see IF that Is the problem.
Beyond that... You get to buy a recone
Sherwood
30-04-2017, 20:02
The bass driver on one of my speakers is vibrating. Certain piano notes are the chief culprits. It does not happen all the time but certain frequencies or sounds result in a distinct buzz. The driver is 15inch and in a Goodmans Magister . I posted a thread a little while back on the repair of them when they were over driven at Christmas. I can't find the thread, but the repair involved sanding down the inside of the voice coil former which was scraping/jamming against the magnet. I thought the repair was successful but now this vibrating has started. When I push the cone there appears to be no scraping what so ever and it moves freely. Has anyone any ideas as to what could make the driver buzz?
Been playing any Rimsky-Korsakov lately?
:scratch:
walpurgis
30-04-2017, 20:32
Geoff might be more help but is on hols at moment.
Geoff has popped in briefly. I'll have a chat with you about this in a few days when I have more time Andrew. I reckon there may be a solution.
Thanks Danilo, Geoff and Geoff who kindly interrupted his holiday.
If there is no rubbing even when biasing the cone in all 360 degree directions, (displacing slightly its axis), I would suspect something has become detached.
There is also the slight possibility that something is being attracted to the magnet and being pulled against the cone by magnetic force, and rattling when the speaker is used. I have seen this on tweeters, in fact my new ATC 50s had it and I removed steel fragments carefully with a screwdriver with another magnet attached. WITH MUCH CARE.
It may be a few overheated turns of the voice coil, and they could possibly be re-fixed with a little superglue inserted into the detachment 'crack', removing all excess immediately. If the V/C is detaching from the cone araldite is suitable, this being used by ATC to attach V/C s to cones, in their case I believe 'quickset'. If the cone is plastic I would use superglue for this as well, but of course it is not much of a gap filler and better for fine crack breaks.
Bigman80
30-04-2017, 22:57
I had an issue like this on an old pair of speakers, certain frequencies (usually a C chord) made a horrendous vibrating sound. Turned out to be a brace in the speaker cab. Reglued using gorilla wood glue and all was well. They were Wharfdales IIRC
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Lawrence001
30-04-2017, 23:06
Are you sure its the bass speaker, piano would also affect the mid range put your ear close and listen. Sometimes it can be more obvious at lower volumes.
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It's definitely the woofer Lawrence. Speakers are actually very simple things in essence, so it is annoying I cannot get to the bottom of the problem. I can't live with it as it is though, so it looks like surgery is going to be the only option (again!). I'll wait to see what Geoff's idea is first before I start the butchery.
walpurgis
03-05-2017, 20:30
I'll wait to see what Geoff's idea is first before I start the butchery.
I shall do a 'walk through' of the technique using an old bass drive unit. Photos will be included, so what needs to be done is clear to understand. Too knackered to do it now, after travelling most of the day. Give me a day or two and I'll have this ready.
Much appreciated Geoff. I've now found the thread where I described my initial repair. http://theartofsound.net/forum/showthread.php?48625-Voice-coil-transplant&highlight=magister It will give you a bit of background.( and maybe a laugh!) I did manage to get both working initially and I've only just noticed the distortion now but it could have been a fault since the'repair' I suppose.
Just to add, and I hope this does not mess up anything Geoff may or may not have done yet, that when I next remove the driver I am going make a small change. The bass driver is fed a full frequency signal directly from the speaker inputs whereas the mid and tweeter signals go through the crossover. I wondered if I could eliminate the problem frequency by using an inductor and a zobel. It might work if the issue emanates from higher frequencies going to bass. It seems it is worth trying anyway and may have added benefits in that the driver would only be fed the lower frequency signals.
I'm sorry to say that I think it highly unlikely that your suggestion will be a cure.
It is more probable that the noise is a result of mechanical rubbing od some sort, and that sound will differ greatly and be very separate in nature from the output of the bass driver.
Even if you filter the input to the woofer, it will still produce a noise if the problem is caused by mechanical fouling.
Thanks for your input Dennis. I think you are probably right. It is only that the fact that the fault is 'excited' by certain frequencies that makes me a little optimistic. To be honest the filter idea is an itch I've been wanting to scratch for a while and if it sounds worse I'll just take it out.
walpurgis
05-05-2017, 20:55
As promised. I've described the technique I use for fixing rubbing coils.
I've put it in the Strokes of Genius section. Here: http://theartofsound.net/forum/showthread.php?51367-The-walpurgis-fix-for-buzzing-and-rubbing-speakers!&p=861169#post861169
Thanks for taking the time to do that Geoff. if I can find some time I'll have a go this weekend.
I've worked on a few old speakers, and once I had a sudden vibration, loud flapping sound, and come to find out a shim of cardboard had fallen into the bottom of the cabinet. Just laying in the bottom. Where it came from I have no idea, probably glued in a corner or something? But just a loose piece of cardboard. And I've also had to deal with speaker wire touching something, I tacked it with glue every foot or so to the inside corner, but it was vibrating at a certain frequency, so I had to run a bead of caulk over the entire wire to quiet it down. And a loose screw, an over tightened screw that would not tighten up well, vibrated at a fairly high frequency. It could be a very low tech problem.
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A couple of people have now mentioned other sources of vibration like loose braces, wires etc. Does the sound from these transfer to the driver? When I put my ear to the cone the sound definitely comes from there. Given the previous trouble I had and what Geoff, Dennis, Danilo, et al have suggested l have to think it is a cone/voice coil issue. Thanks everyone for their suggestions. AOS at its best.
anthonyTD
06-05-2017, 08:05
Sometimes the actual speechcoil wire can become loose on the former [Due to excesive heat, or just age] and it can cause the sound your refering to.
The glue, or resin holding the wire to the former can just deteriorate natuarly over time.
I have also had speakers where the speechcoil former has become partialy detached from the cone, again, where either the glue has broken down, cracked etc.
The glue holding the pig tails to the cone can also crack, and allow the pigtail wires to resonate at certain frequencies too.
These are all common faults I have seen over the years.
Of course, there may be nothing wrong with the speaker, and it could just be that the amplifier, and speaker combination are borderline stable, and at certain frequencies, they become unstable, causing a distortion.
Either way; Hope you get it sorted.:)
A...
A couple of people have now mentioned other sources of vibration like loose braces, wires etc. Does the sound from these transfer to the driver? When I put my ear to the cone the sound definitely comes from there. Given the previous trouble I had and what Geoff, Dennis, Danilo, et al have suggested l have to think it is a cone/voice coil issue. Thanks everyone for their suggestions. AOS at its best.
The short answer is yes. When that loose cardboard was in the cabinet, I could have sworn it was a bad driver. But removing the driver from the cabinet proved that it wasn't. The noise did not follow the driver, away from the cabinet. But it had me fooled until I did.
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