I got an Eminence CB15 speaker in a bass guitar enclosure for free.
The Eminence rattles at around 45hz, which I notice is near it's specified resonant frequency. When I gently move the cone in and out by hand, with it out of the enclosure, I can't feel or hear any cone rub. I can't see any tears in the cone. The cone is glued solidly around the outer lip.
Recently I was able to fix an old Peavey Black Widow 15" by unbolting the magnet and rotating it 1/3, which cured the cone rub. Very gratifying!
But this one doesn't seem to have bolts. Are these things glued together?
Given the cost of recone kits now, I guess it is a paper weight if I can't get in it without cutting the cone? The free enclosure is useful for the Peavey anyway, but is there anything to be done with this speaker? It looks new and sounds great in higher frequencies.
The Eminence rattles at around 45hz, which I notice is near it's specified resonant frequency. When I gently move the cone in and out by hand, with it out of the enclosure, I can't feel or hear any cone rub. I can't see any tears in the cone. The cone is glued solidly around the outer lip.
Recently I was able to fix an old Peavey Black Widow 15" by unbolting the magnet and rotating it 1/3, which cured the cone rub. Very gratifying!
But this one doesn't seem to have bolts. Are these things glued together?
Given the cost of recone kits now, I guess it is a paper weight if I can't get in it without cutting the cone? The free enclosure is useful for the Peavey anyway, but is there anything to be done with this speaker? It looks new and sounds great in higher frequencies.
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Perhaps a small piece of iron is in between magnet and coil. Depending on the position of the particle, it makes noise or not. Many years ago I found such a particle in the clarxon relay of my father's car (Ford Falcon 1980). The clarxon sometimes played, sometimes refused to sound.
Did you note which way the driver was mounted when it was removed? Remounting it 180 deg from that may over time correct a small about of cone sag that may have occurred, but if the magnet has shifted or the VC or former got damaged from over excursion there is no bringing it back without professional help.
Yes the magnet is glued on with these drivers, that is actually the most common method used, the bolt-on method PV used on the BW drivers is unique to them and maybe one other manufacturer.
Yes the magnet is glued on with these drivers, that is actually the most common method used, the bolt-on method PV used on the BW drivers is unique to them and maybe one other manufacturer.
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Perhaps there is something loose under the dust cap. Some models in the past have actually used mass plugs under the dust cap to lower fs and raise Qts and I have had these work loose and buzz. You do have to pull the dust cap to confirm and/or fix. If it’s something stuck in the gap causing it, you still have to pull the dust cap and vacuum it out. The only problem with pulling the dust cap and putting on another one is the high frequency response is usually altered for the worse. But better than just binning it.
That's interesting - because of the way this Peavey Black Widow was built, this specimen from the 80s is still doing service. But I guess that's a terrible business model for Peavey!
I will try hanging it 180 degrees from where it was - I got nothing to lose.
I like your thinking. I will google that and consider replacing the dust cap. The sound does have a sort of paper-scrapey note to it. If I can get it to not rattle too much at midranges, I might get some use out of it as a guitar speaker, a la Virboverb.
The Eminence CB15 has only 70 grams Mms, doubt there is any added mass (or cone sag) on a recent vintage 15" using a thin dustcap and light cone. For comparison, an Eminence LAB 15 Mms is 308 grams.
Irregularities in the dust cap glue joint are visible in the picture on the Eminence CB15 spec sheet, a dab of adhesive may have broken loose and cause rattling.
You could cut a dime-size hole in the dust cap, turn the speaker cone down and vibrate the particle (if that's the problem) through the hole by hand or with a swept tone.
You could then glue similar thickness paper stock or cone material over the small hole- easier to do than cutting out the entire dust cap joint without damaging the cone or leaving the glue joint.
Good luck, post back with a picture of what you find inside!
Art
That sounds like an excellent plan - thanks for that. I have in past had success patching rips in speaker cones with a piece of coffee filter and carpenter's glue, so same idea.
Dime-sized hole with an x-acto knife, and see if anything pops out. If so, patch it back up, if not, maybe go for broke with the dust cap and look at the coil. Nothing ventured, nothing gained. Somewhere on the sides, not at the center? Would a rectangular or circular hole / patch seal up better?
Mine looks like this: I can't see an opening in the seal, but it's certainly got blobs of glue..
I'd cut a round hole in the center, and use a round patch if you loose the rattle.
Well it was a good plan, appreciate it.
I even cut a square like a door flap so that I could have closed it back up and patched it, but unfortunately it wasn't a particle under the dust cap.
So I cut the dust cap off to have a look. When I move the cone up from the back, I can get it to a point where it rub, but it's well past the 5mm maximum excursion. So I don't think it's even that. Well within a range of 5mm, or playing a guitar through it at moderate volume, it still rattles like hell.
I tried to just 'work' the coil around the magnet core a little, and used a piece of newspaper to clear around the inside in case there was a particle in there, but I think this one is going to end up in the dumpster, which is a shame. Long live Peavey!
Put a vacuum cleaner hose up to the dust cap and suck away. There might be something down in the gap that won’t come out any other way.
Make sure it isn’t anything simple like tinsel leads slapping. Or part of the spider coming loose at the frame.
Make sure it isn’t anything simple like tinsel leads slapping. Or part of the spider coming loose at the frame.
Since we're at the point of trying almost anything and you already have the dust cap cut out, if you have a tone generator hook it to an amp with the speaker connected to the amp, hold the speaker upside down and feed it with
30hz or so sine wave and see if that shakes anything loose.
Peavey and McCauley are the first two I can think of that use a replaceable basket with a bolt on magnet.
Quite a magnets are still bolted to the frame but the bolt heads are under the spider!
30hz or so sine wave and see if that shakes anything loose.
Peavey and McCauley are the first two I can think of that use a replaceable basket with a bolt on magnet.
Quite a magnets are still bolted to the frame but the bolt heads are under the spider!
If those are iron filings I doubt a vacuum cleaner will get them out. That method assumes what’s in the gap doesn't stick to magnets.
I had to get a bunch of iron filings out of the gap of a ribbon tweeter before putting in the new one. It was an adventure. Those are some strong *** magnets.
I had to get a bunch of iron filings out of the gap of a ribbon tweeter before putting in the new one. It was an adventure. Those are some strong *** magnets.
Yeah I believe it. It looks like iron filings - chips off the magnet itself? In any case it's kind of gratifying to solve the mystery, if that's what it was.
I really thought it was tinsel leads slapping - it is a very paper scrapey kind of rattle, that happens at higher volume in some midrange frequency.
I don't know if this video makes sense, but when the speaker get to a certain point where the cone starts the travel back down, that's when it starts to rattle. Happens at a different level depending on frequency - here 45ish hz.
What I heard in the video sounds more like mechanical limit than like some thing in the gap rubbing.
Yeah it does. But it's making that rattle at much lower levels, when at higher fundamental frequencies. I can't figure out what's physically rubbing.
With the last video it sounds more like voice coil windings that are loose on the former, rubbing ect.
That said have you double checked the glue seams at the spider and the surround.
After that just cut the cone out and post a picture of the voice coil!!
That said have you double checked the glue seams at the spider and the surround.
After that just cut the cone out and post a picture of the voice coil!!
Sigh, it looked promising for a minute there, when some filings came up from the gap! I can't bring myself to go the last measure and slit the thing's throat, lol.
At least the cabinet was free and useful. The rest is just for the enjoyment of tinkering, which is I think what this forum is about.