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I have a JBL D123 speaker which I use in a 5 watt tube guitar amp. This is not unusual as the D123 actually has a good reputation for use as a guitar speaker.
In any event, it has a very light buzz on certain notes. I'm not sure when this started, and it may have been there all along as I have had this speaker for a long time but only started using it more frequently of late. It's not terribly objectionable, but it's there. The speaker exhibits no rubbing when physically moving the cone, so I am wondering if someone can tell me what it might be or how to approach the problem. I'm pretty handy mechanically, and in fact recently fixed an 8" alnico speaker that had a blister in the voice coil which was rubbing. I took the horseshoe magnet off, glued the blister down, and put it back together and it works fine. Mind you, I know the D123 is certainly different, and worth more, so I might hesitate to perform surgery with the same recklessness. I cannot even see how the cover would come off. I would be very grateful for any thoughts or ideas.
Hi, didn't have time to check all replies, but first check for
a broken glue joint on dust cap...those can buzz at certain frequencies.
Well just remove it and check for buzz again. If buzz gone, re-glue cap
If buzz still present, you can inspect the cone/bobbin joint. Those are
known to come loose...use epoxy. Also look for any contact of
the bobbin on the pole piece while moving the cone. Check for
Next is the spider to cone glue joint. Those can come loose and buzz or click. Epoxy is best here.
Let me know results...
I tried holding the surround at virtually all points from underneath and above, but nothing changed the buzz. I also tried what I thought was a novel idea of using masking tape applied to the cone to pull on it in various ways while listening for a change in the buzz. Nothing changed it. Visually, everything looks dead mint, and no rub is remotely detectable. I also made a slim tool out of wire to press on the internal grill in case it was buzzing, to no avail.
With respect to removing the dustcap, I watched a youtube video of a tech sliding an exacto knife around the cap. Here's my question. Is there a flange or lip to these dust caps, or are they literally a section of a sphere with a sharp edge?
And I'm sure I'll catch heck for not disclosing the whole story, but I actually have two D123's, and they both exhibit the same buzz. Now I'm sure the first thing everyone will think is that it has to be something other than the speakers, and that's part of the reason why I didn't complicate things by mentioning it at the outset, but the speakers buzz with multiple amps and multiple guitars, and my other speakers, of which I have many, do not buzz with those same amps and guitars.
You just cut the cap at the very outer edge ...maybe 1mm
away from the crease. You don't need the lip to glue it back
on. Set it on the cone, then run the bead of glue around it.
I don't think it's a surround problem, but one of the three
The mystery deepens. I dug out an HP signal generator (yes, I realize I should have done this much earlier) and connected it to my amp and one of the speakers. No remote buzz anywhere in the audible spectrum, even at moderate power. However, very oddly, there is a resonance at 120 Hz. In other words, if I sweep just north or south of 120, I can hear beats, which increase in tempo as I sweep north or south. It's not at all like it manifests as buzz when playing, but I cannot account for it. And it's present in both speakers! Any thoughts?
Update: I just tried running the amplifier and the HP signal generator on a Oneac power conditioner I run my stereo through, and the resonance is still there.
Update #2: I just tried another speaker, a 12" alnico Marsland, and I can detect beats around 120 Hz, perhaps to a slightly lesser degree, but they're there.
Update #3: I just realized that it's plausible the 120 Hz (60) resonance is coming directly from the power supply of HP tone generator, which is at least 40 year old.
Yep, bad 40 yr. old filter caps in pwr. supply.
It's present on different guitars, so I've ruled out that possibility as well as cabinet as it's present with the speaker out of the cabinet.
To be certain the cabinet is not the problem.. Maybe listen to the speaker just laying flat on the floor? Sans cabinet?
(I think it is the cabinet..)
Also, maybe have someone hold the speaker, or speaker in cabinet at different angles. and see if it changes the noise?
Perhaps also listen to the speaker with SOME OTHER AMP? Maybe it is the amplifier???
I over looked the fact that you are using this as a guitar amp speaker.
Does this buzz happen when you are using it as a stereo speaker? If not than you are over driving the speaker.
Most of the earlier speakers were not built that rugged.
Hook it back up to a stereo and post your results.
I haven't tried it as a stereo speaker, but I'm pretty sure it's not an excessive power issue. The D123 is a well known and well regarded speaker for blues guitar (I do realize these drivers must not be over driven without undue risk) and I have only used it with 5 watt 1 x EL84 amps. Also, the buzz is audible at very modest levels (conversation level or less) even when using small amps. Still, I could probably hook it up to a stereo to try it with music. I am just about to spend a bit of time looking closely at the surround for any debris.
If you were using them for guitar then look around on the spider and basket for any cracking.
I know it's a three handed job but see if you can hold different parts to stop the buzz sound. If it's a positional change that stops the buzzing then it's in the voice coil mechanism/housing.
I just removed perhaps 5 or 6 small pieces of particle board from the surround using tweezers, right down close to the frame, although I won't have time to test it until later. The largest was a good 3/32" across, so I'm hoping that was the problem. Will report back later.
That COULD do it - let's hope!!!
After one pass of removing debris, I was confident I heard an improvement, but could still detect some buzz. This was with the speaker out and sitting on its back for testing. I then did another pass of debris clearing and found perhaps another 6 smaller pieces, but again, right up near where the surround meets the frame. It's a very awkward place to get to and I needed a small flashlight, reading glasses, a toothpick, and tweezers to do the job.
I also tried a trick I thought of based on the comment by DJK, that the cone may have sagged over the long haul and could be rubbing at the voice coil. I put a piece of thread around the cone where it meets the spider and tied a large loop. I was then able to apply some gentle force by pulling the loop in the opposite direction to how the cone would have sagged *if* it had sagged. There was no effect, so it seems unlikely that internal rubbing is the problem.
I tried again after the second debris clearing pass and felt there was a substantial improvement, perhaps even no buzz, but I couldn't be positive because I was also suffering some aural fatigue from listening so critically for every little thing at volume higher than I normally listen at. I put the speaker back in the cabinet and was disappointed to hear obvious buzz. It's a 14 x 12 x 24" speaker cabinet with the tweeter hole boarded over, a bass port, and the back open.
I then started putting pressure on the cabinet sides, and other places while playing (using a looper pedal to generate signal for hands free testing) but when I pulled on the bass port, the buzz kicked up considerably, and could be controlled depending on how I applied pressure to it. So, it seems as though I had compound issues. Now I have to solve the cabinet. What's interesting and new to me is that the buzz from the debris in the surround (the speaker buzzed even when it was apart from the cabinet, so it was definitely a good part of the problem) is remarkably similar to the buzz now coming from the cabinet, to the point one could easily confuse them. My lesson learned is mechanical buzzes can manifest anywhere and sound similar regardless of where they come from. I'll report back once I've had a chance to address the cabinet with some glue, screws, or what have you.
I'm completely stumped. I thought I had solved it, but it's still there, even with the speaker out of the cabinet. I've tried moving the tinsel. I've tried different guitars and different amps. I've tried pressing on the surround on every inch, but nothing works. My new guess is something loose under the dust cap.
I'm sure I'm going to get warnings not to proceed this way, but how would one go about removing the dust caps? Is there a solvent to soften the glue joint? Any good books to recommend on speaker servicing?
Make no attempt to remove an alnico magnet, if you manage to succeed (and you won't on the JBL) the magnet will lose a lot of its magnetism.
Message received. Will heed advice. If I'm not lucky in finding some obvious hanging debris of some kind, is there such a thing as an unsolvable buzz? Could a good speaker tech solve this kind of problem without necessarily reconing?
A good speaker guy might be able to remove the dust-cap, clean and shim the gap, soften the spider with acetone, let it dry, test, and if OK put on a new dust-cap.
Thanks. I just tried shaking the speaker while holding it close to my ear, and I don't hear anything that could be loose or anything like particles inside. Mind you, that's not to say I would necessarily be able to hear something from shaking, but it seemed like an interesting thing to try. However, I did find some little balls of debris of some kind (maybe insulation from an old cabinet?) that stand proud on the surround on the back side. Later this evening I will get the tweezers out and remove anything I can see and try again. All advice appreciated.
Try rotating the drivers 180 degrees. Sometimes the VC starts rubbing.
I appreciate the replies. I pulled the speaker and tried it free of the cabinet, and tried it in various spacial orientations and it still buzzes, so at least that rules out cabinet and solution by rotating. I've also discovered it's actually present on virtually all notes of the guitar up to the third string. Very mechanical sounding. I'll try a closer inspection around the surround to see if something jumps out.
Are you sure the buzzing isnt coming from the input signal from the guitar? Try the guitar on another speaker and see if it is still there.
"so at least that rules out cabinet and solution by rotating"
So, it was in its original orientation for what, 40 years (and you rotated of 5 minutes)?
Carefully put some acetone on the spider and massage it back into alignment.
I appreciate the reply, but wouldn't a misalignment betray itself in some definitive way, such as when I am pushing the cone and listening/feeling for some rub? It just seems like a fairly invasive fix when I don't have a firm diagnosis yet. Does the acetone soften the spider?
It may be possible that the tinsel connecting the terminals to the VC are hitting the cone, so at some frequencies where they have a mechanical resonance, they vibrate enough to hit the cone. Dont rule out the cabinet being the culprit either. It seems some investigation is in order.
I tried holding the tinsel and manipulating while the buzz was active and detected no discernible change in the buzz, so I'm conjecturing it's something else.
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