Diagnosing/Eliminating Speaker Rattle (or Buzz)

[overdrive]

While I realize there can be many sources & causes for this common problem/occurance, just thought I'd run it by in hopes of a 'quick fix'.
An acquaintance dropped a small enclosure off & asked me to have a look at it.

Problem: the speaker (a small 8" Weber Alnico 'Signature Series') in a small pine enclosure) tends to buzz/rattle at higher volume levels when the wound E/A string(s) are struck only at the 12th fret & nowhere else. While the speaker is rated at 15 watts, it never gets pushed past maybe 2 watts (the maximum output of the amplifier section). It is a separate enclosure & a small tube amp rests on top of it...there is no rattling coming from the chassis or tube sockets.

So far all I've done is tightened the speaker screws/nuts & I can still hear it.
The guitar regularly used with this set-up is 'buzz-free' (in terms of action/frets).

The symptom being only at the 12th + higher volume, could harmonics be playing a role in this peculiarity?

Unfortunately there was no reference/feedback as to whether this symptom had been occuring earlier...apparently it became noticeable at a later date when the amp was finally being cranked a bit.

[bajaman]

It is probably a loose coil winding
bajaman

[tubeswell]

Is the enclosure itself actually buzz-free? You say it's pine, but has it got any knots in it?, or is it pine ply with loose lams? or are the joints rattly? Is the baffle rattling against the rest of the cab? Does the rear panel(s) rattle? Is the baffle bad/poor grade ply which rattles?

has the speaker been tried in another enclosure? has another speaker been tried in that enclosure?

[overdrive]

Is the enclosure itself actually buzz-free? You say it's pine, but has it got any knots in it?, or is it pine ply with loose lams? or are the joints rattly? Is the baffle rattling against the rest of the cab? Does the rear panel(s) rattle? Is the baffle bad/poor grade ply which rattles?

has the speaker been tried in another enclosure? has another speaker been tried in that enclosure?

Good points...think I'll have this guy have someone else check it out *L*
Way too many variables for me to be spending/wasting my time on it.
The sides are of 3/4" knot-free, #1 pine, the baffle & rear sections of 1/2" plywood. No baffle/rear section rattling...haven't switched enclosures as I have no real intention of building one just for this particular excercise/experience.

BTW, should add that this symptom only occurs when the Stratocaster neck pickup is engaged...the lower frequency/tones seems to make it more noticeable (or something).

[gbono]

Check the following:

tinsel leads from voice coil are not rubbing on cone during maximum excursion

hopefully the speaker is properly vented so that trapped air in the motor assembly can escape?

do not over tightem mounting hardware - this can damage the driver

I'm assuming that the frame isn't bent and the voice coil is rubbing in the gap?

[trevorus]

I'm assuming that the frame isn't bent and the voice coil is rubbing in the gap?

I have had this happen on more than one occasion from unevenly torquing the speakers. It doesn't have to be measured exactly, but get them close, otherwise it can force the basket in odd ways and make it buzz or crackle.

[captntasty]

Not sure how this helps, but I have the same speaker with the same symptom as well as the ceramic version - same thing. I'm not beating down Weber, they are a pleasure to do business with and make quality products, but these are their economy line and perhaps QC is not up to their usual as on their upper end products - I'm not even sure they actually assemble this line in house, it might be subbed out to meet a price point. My diagnosis has been slight voice-coil rub... not sure.

edit: have you tried this speaker with another amp. The first diy amp (a champ/princeton sort) I built had a symptom that sounds like a buzz in the speaker, almost a blown speaker... the speakers are fine but the amp produces this artifact no matter the speakers used.

[J M Fahey]

1) Take the speaker out; put it face up on a table, the magnet on a book or a piece of thick cloth or leather,(we are avoiding all unrelated buzzes here.
with speaker disconnected, lightly tap the cone , rising your finger instantly to let it vibrate freely.
Do it in several points around the cone.
You want to hear a dull thump, at the cone's resonant frequency.
You do not want to hear a rasping sound accompanying it.
You can also grab the cone evenly across and move it slightly up and down, listening for raspy noises. This test detects scratch noise, either because bent frame, dirt in the gap or bubble in the voice coil adhesive.
2) Connect the speaker to a clean amp, SS preferred, hook an oscillator and drive the speaker with a 2 or 3 Volt signal on its terminals (a couple watts).
Sweep slowly from 60 to 300 or 400 Hz. Beware, at some frequencies you will hear more buzz than you asked for, but try to reproduce the one you get with your guitar. The reason for sweeping lies in that the speaker may vibrate at a harmonic of the original note.
When you hear it loud and clear, look at it carefully: are flexible wires beating something? Does it come from a poorly glued dustcap? Does applying your finger somewhere cdamp it? Bending the frame *slightly* with your fingers? etc.
If you get a buzzing sound and you find no visible reason for it, then your voice coil is shot somehow, or poorly glued or has loose wires ---> trash bin.
Good luck.
If

[52 Bill]

1) ...lightly tap the cone , rising your finger instantly to let it vibrate freely.
Do it in several points around the cone.
You want to hear a dull thump, at the cone's resonant frequency.
You do not want to hear a rasping sound accompanying it.

A trick my father taught me was to hold the speaker up to your ear and hit the back of the magnet/frame. It would cause the cone to move forward and back and you could detect the rasp of a voice coil rub.

[Enzo]

I use the same trick. Hold the speaker by the frame or grasp the magnet. Hold it up in front of your face pointing away. Whack the back of the magnet with your fist - or a rubber mallet - and listen. A good speaker makes a dull resonant "tum". If the voice coil rubs, there will be an added little flap sound.

[overdrive]

edit: have you tried this speaker with another amp. The first diy amp (a champ/princeton sort) I built had a symptom that sounds like a buzz in the speaker, almost a blown speaker... the speakers are fine but the amp produces this artifact no matter the speakers used.

Mystery solved...sort of. Ran two different tube amplifiers (an Emery Superbaby & a Gilmore Ardmore, both about 4-8 watts) into this speaker/enclosure & everythings sounds OK...pretty much par for what one might/should expect from a smaller, low-end Weber Alnico speaker.

Now I'm somewhat curious what might be the cause of this 'echo-like' buzz/hum emanating from the amplifier. Turns out it is slightly audible even at lower volume but more pronounced when the volume level is turned up.

Peculiar that it occurs only at a specific area of the guitar scale...the natural 'harmonic' areas.

Running this particular amp through several different enclosures pretty much solved/eliminated the first problem but left a new one in its wake.

[heavymod]

I Reg'd just to say thanks

1) Take the speaker out; put it face up on a table, the magnet on a book or a piece of thick cloth or leather,(we are avoiding all unrelated buzzes here.
with speaker disconnected, lightly tap the cone , rising your finger instantly to let it vibrate freely.
Do it in several points around the cone.
You want to hear a dull thump, at the cone's resonant frequency.
You do not want to hear a rasping sound accompanying it.
You can also grab the cone evenly across and move it slightly up and down, listening for raspy noises. This test detects scratch noise, either because bent frame, dirt in the gap or bubble in the voice coil adhesive.
2) Connect the speaker to a clean amp, SS preferred, hook an oscillator and drive the speaker with a 2 or 3 Volt signal on its terminals (a couple watts).
Sweep slowly from 60 to 300 or 400 Hz. Beware, at some frequencies you will hear more buzz than you asked for, but try to reproduce the one you get with your guitar. The reason for sweeping lies in that the speaker may vibrate at a harmonic of the original note.
When you hear it loud and clear, look at it carefully: are flexible wires beating something? Does it come from a poorly glued dustcap? Does applying your finger somewhere cdamp it? Bending the frame *slightly* with your fingers? etc.
If you get a buzzing sound and you find no visible reason for it, then your voice coil is shot somehow, or poorly glued or has loose wires ---> trash bin.
Good luck.
If

Thanks SO MUCH for a debug process I could follow. I was getting a strange vibration off a bass speaker, and it was driving me insane. Heavy as hell, in a heavy cab - I was worried it might be the cab, the room, the speaker - and eliminating each was driving me crazy. I followed your instructions and hooked up an function generator, and cycled through different frequencies... sure enough it localized around 1.5 khz-1.7 khz. I then tried muffling different areas to locate the problem. finally got lucky - I rested my finger under the speaker wire connects.. and it stopped. Turns out when I was changing cabinets, two washers stuck to the magnet. It was in a hard to find location - the magnet was powerful enough to hold them between the cone and the magnet.

Thanks so much. I was worried I had ruined a JBL D1430F

[1ampman]

What an odd find. I use the speaker magnets to hold chassis, reverb pan, etc screws. I'll have to be careful not to let one get by the spider, etc.... Good detective work!

[heavymod]

I didn't know that was called the spider, thanks!

[Enzo]

This describes the basic parts. I think they left out the surround, that is the flexible part around the edge of the cone.