Speaker voice coil rub ?

[ASC67]

I have heard the term before but I'm not sure what it sounds like. What brings about this question is that I'm trying to track down a vibration sound in my amp. I have checked everything that I can touch and tighten down in the amp.

When I play with the bass up a bit and on the neck pickup there is this vibration sound in the background and it seems to be the speakers. Is this what voice coil rub sounds like are my speakers shot? They still sound good other than the annoying vibration sound.

The amp is a 1975 MM HD130 with the original 2x10" Alnico speakers.

 

[backline]

Typically not a vibration sound, more of a decay, like there is something wrong with the amp kind of sound. Maybe your speakers are loose at the baffle..??
At any rate, it is very easy to check for coil rub. Pull the speakers, lay them on their magnets with the cone facing you. Using both hands, judicially and carefully push down on the cone with even pressure, taking care not to shove your finger tips through the cone. You want the cone to move in and out as if it were active. If there is coil rub, it will be apparent. You will hear and feel it.
Good Luck

 

[ASC67]

Well, I pulled the speaker baffle and the sound is indeed coming from the speaker. I pulled back the dust cover on the back of the speaker and there is copper colored coil around the magnet that is vibrating on either the round magnet or the frame and causing the buzzing sound. Any way to fix this or am I looking at new speakers. I disconnected that speaker and it goes away except on certain high notes it still makes an audible noise.

 

[T Prior]

Basically the speakers are fried. I just replaced a pair of Jensen Alnico P10's where there was a very slight but noticiable harmonic distortion on the sustain of notes, mostly on the low strings. At first I thought it was tubes but it turned out to be the voice coils rubbing.

Hate to say it but this is no diffrerent than a blown speaker. Rebuild them or replace them . I replaced mine with Jensen MODS, 50 watt series.

t

 

[sultan59]

sometimes, especially on older speakers, all you need to do is rotate them 180 degrees. Apparently gravity can come into play over the years and cause something in there to sag and rub.
I've had this happen twice on different speakers, one JBL D130F and an EV15L.

 

[bingy]

sometimes, especially on older speakers, all you need to do is rotate them 180 degrees. Apparently gravity can come into play over the years and cause something in there to sag and rub.
I've had this happen twice on different speakers, one JBL D130F and an EV15L.

Rotation is a great idea.

 

[ASC67]

Rotation is a great idea.

When I had the baffle out I did flip it upside down it actually sounded about the same.

 

[ASC67]

Rotation

Good news !

I thought about it last night and this morning I took both speakers out flipped them one side for the other which put them 180 degrees from where they had been and put the baffle back in the amp. To my surprise this seems to have done the trick. When I first fired it up they were still rubbing a bit but the longer I played they seemed to settle in and the rub pretty much gone. I think I can live with it for awhile.

I'm a happy camper and thanks for the suggestion !!!

 

[sultan59]