Speaker noise

rgorke · Post by **rgorke** » Thu Dec 08, 2011 8:38 pm

I am having some annoying noise come out of my cabinet. I am pretty sure it is speaker related. Does this sound familiar to anyone? I don't think speaker wire is on the cone and I checked the bolts holding the speakers.

soundguruman · Post by **soundguruman** » Thu Dec 08, 2011 10:48 pm

The bias of your amp is out of adjustment, it's not the speakers.

rgorke · Post by **rgorke** » Fri Dec 09, 2011 9:55 am

soundguruman wrote:The bias of your amp is out of adjustment, it's not the speakers.

Thanks, I tried adjusting the bias and it is still there. It just started a week ago or so. I haven't changed the tubes or bias in months.

Coot Boy · Post by **Coot Boy** » Sun Dec 11, 2011 11:28 pm

Check that the spiders are glued down ALL the way around. If a section comes unglued you can get that kind of noise.

Post by **Scumback Speakers** » Mon Dec 12, 2011 1:30 am

Coot Boy wrote:Check that the spiders are glued down ALL the way around. If a section comes unglued you can get that kind of noise.

It could be the dust cap, spider, voice coil coming apart, or a loose magnet. You just have to systematically rule each one out.

BaronGreenback · Post by **BaronGreenback** » Mon Dec 12, 2011 3:34 pm

Scumback Speakers wrote:
Coot Boy wrote:Check that the spiders are glued down ALL the way around. If a section comes unglued you can get that kind of noise.
It could be the dust cap, spider, voice coil coming apart, or a loose magnet. You just have to systematically rule each one out.

out of interest what do you mean by a loose magnet jim?

i once had the displeasure of taking a celestion magnet apart. just because im curious how things are made. i had to use an impact driver to budge the big screws in the back, and then the strength of the magnet itself was insane, prizing the metal parts from the black ceramic part took some strength!

how would it rattle? and how would you check that was the fault?

Post by **Scumback Speakers** » Mon Dec 12, 2011 3:55 pm

BaronGreenback wrote:out of interest what do you mean by a loose magnet jim?

i once had the displeasure of taking a celestion magnet apart. just because im curious how things are made. i had to use an impact driver to budge the big screws in the back, and then the strength of the magnet itself was insane, prizing the metal parts from the black ceramic part took some strength!

how would it rattle? and how would you check that was the fault?

Magnets come loose due to the epoxy failing. It's supposed to happen rarely. Probably once every 500-100 speakers in my experience. However if the manufacturer uses poor epoxy that doesn't cure, or isn't cured, and improper or faulty build techniques that can happen much more often, as I've found out earlier this year, much to my chagrin.

Even the old Celestions with the rear magnet mounting plate screws can come loose, I have a couple here right now (Silver Vox Alnico and a pre rola G12H30) in fact. When the epoxy/glue fails, a bump can shift the magnet. That pinches the coil between the pole piece and magnet...and goodbye speaker tone.

While the magnet still holds it together, it doesn't keep it aligned, and neither do the screws.

If you check the glue on the spider/dust cap and it's not separated, then you know it's probably the voice coil or magnet (not much left, right?) alignment/centering that's gone south.

Lots of ways to tell...the two easiest are:

1) You can visually see of feel/measure that the back plate is not aligned properly to the ceramic/alnico magnet, with an overhang farther on one side than the other. I've got that going here with a Scumnico that was sent back to me to diagnose (made by my previous manufacturer) for why it sounded bad. The epoxy/glue just plain old came loose after 3 years. They should last way longer than that.

2) You rip the speaker apart to recone it and find the shims/jigs used to properly align/center the voice coil in the gap are tighter on one side than the other. Remember, this gap is small .005-.006 depending on the coil/speaker frame specs. That's about a thin business card in thickness. It doesn't take much to goof that up.

The bad part is that either way, it's almost always a recone/rebuild to fix it.

rgorke · Post by **rgorke** » Mon Dec 12, 2011 4:45 pm

Thanks everyone for your input. After taking each speaker out to figure our which one it was, I started replacing each speaker and then realized I still had the noise with the new speakers.

So it wasn't speaker related at all. In my elimination process, one of my new pedals was left on and wasn't working well with others and was causing that noise. I had never heard it before.

Anyway, in the process, my cabinet is all checked over. Each screw, wire, etc is tightened and checked.

Thanks again for everyone's help, it sure sounded like a speaker problem.

stef · Post by **stef** » Mon Dec 12, 2011 9:32 pm

Scumback Speakers wrote:
Speaker bolts 101 for old Celestion style speakers (and clones like the Scumback) with thin frames of stamped steel.

Make sure baffle board is perfectly flat.

Make sure speaker frame is flat and fits flush to baffleboard (before attaching with bolts). The gasket should meet the baffleboard, not the steel frame.

Put in bolts until the head meets the back of the speaker frame.

Tighten bolts no more than 3/4 to 1 full turn, using a screwdriver, not an electric drill/etc.

Tighten bolts in a cross pattern (X) 1/4 turn at a time until you get to 3/4 or 1 full turn...MAX!

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