Speaker sounds blown but looks fine.. Ideas?

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KTMKIV

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Hey guys, sorry if this has been posted before, I couldn't find any answers when I searched. I have a late 90's angled 4x12 recto cab I'm having issues with. I've been getting a nasty sounding vibration, particularly with notes in the lower register ( picture the noise a light saber makes when its turned on, but louder). For the life of me, I cant tell which speaker its coming from, and all four speakers appear to be intact and not blown. Ive tried ot through a couple of amps and its the same with both. Any ideas on what it might be? I'm pretty solidly stumped...
 
Just because a speaker looks okay, doesn't mean it isn't blown. "blown" doesn't necessarily mean it has a hole in it. You could have cone rub or excessive wear or dryness of the paper. Low notes have a long wavelength, so the speaker cone has travel farther. If the cone or paper can't handle that, it sounds awful.

My suggestion is to find which speaker or speakers is the culprit. One way is to buy one new speaker of matching impedance, and swap it for one speaker at a time, until you find the bad one. Another way is to rewire the cab as a 2x12. If the two working speakers sound good, you have narrowed the suspect down to the other two. From there it is a single swap to find the bad one.

These are pretty basic suggestions. I am sure there are more savvy and tech minded folks here who can add their ideas.
Good luck.
 
I will probably try swapping the speaker one by one since I do have a spare... But another issue complicating it is it seems to be intermittent. It can sometimes go days without making a peep. The input jack went on it a while back ( no sound whatsoever) so I'm wondering if it isnt some sort of shoddy rewiring by the shop I bought it at, judging by the amount of random excess glue i found on the inside of the panel...
 
Well, if sometimes it sounds just fine, then it snt a blown speaker. If it intermittent and sometimes the cabinet sounds just fine, then it is something else. All that leaves is the jack and the wiring in the cabinet, unless your guitar cable is bad or the speaker cable between the amp and the cabinet. Start by changing one thing in the signal chain until you find the source of the problem.
 
This may be super obvious, but it sounds like you've either got something loose in the cab or a speaker that's not securely screwed down.

That would definitely be my guess if

- the noise doesn't happen at very low levels
- but does happen even before you turn up really loud
- is a low frequency thing
- that sounds like rumbling, not farting or tearing
 
morgan138 said:
This may be super obvious, but it sounds like you've either got something loose in the cab or a speaker that's not securely screwed down.

That would definitely be my guess if

- the noise doesn't happen at very low levels
- but does happen even before you turn up really loud
- is a low frequency thing
- that sounds like rumbling, not farting or tearing
+1

Also, if there is excessive wire in the cab (sloppy wiring), wire could be touching the backside of the cone causing buzzing/farting.

Dom
 
Ill hit on this. For the first time in my 46 years of playing I had a cable that dropped signal, it didn't cut out, it dropped signal to like to 20% and kind of sputtered but never quit. Sounded kinda like a blown speaker. As I was trying to find the problem it would come back on. Then hours of playing no problem. You may try changing out cables. Do not forget the one that goes into the amp. I have my suspicions as to what the cable problem is/was but for me it was the one going into the amp. The cable tests fine so maybe the diameter of the plug? I have not checked it with a micrometer yet but I am going to. It sounded like a blown speaker but for me I knew it wasn't as I have two cabinets connected and they both did it.

I have now begun to spend the bucks and I'm buying those $40+ cables.
 
I'd first check for mechanical vibration on the cabinet (loose screw, hardware/corner bracket, lose board in cab (i.e. needs regluing).

If that is fine, then the problem could be caused by a voice coil rub. As a result of gravity, speaker cones may sag over time which causes them to go out of alignment and cause the coil to rub when the speaker moves in and out. You can either disconnect the speakers one at a time to find the offender. Or, you could also check for speaker rub by gently pushing the speaker in a short distance, a few times with your hand - push the cone straight in with even pressure, not the dust cap. You should feel no rubbing when doing this. If you do, you've found the problem. If one is rubbing, you can try rotating it 180 degrees, which may make the problem go away if you're lucky. If this fix doesn't work, then the speaker will most likely have to be reconed or replaced.
 
If the cab makes noise at certain frequencies, perhaps a G note in the lower registers, it could be a number of things, grill vibration, baffle board vibration (usually above the inner post on the top baffle), air leak on the side handle, vibrating back board.

Good suggestion about the loose speaker screws.

If it is not mechanical but sounds static like, it may be a bad solder joint or damaged wire.

A wooshing sound of jedi saber, could be loose speaker bolts or screws, to a broken seal in the cab.
 
Since I originally replied to this old thread, I've had what might be a similar issue. The problem was that low frequencies at medium-high volume would make the back panel rattle against the brace. It's easy to test for this: have someone play til the noise happens, then push against the back panel and see if that changes or stops the noise (you'll also feel it).

I seem to have fixed it by adding more padding on the panel where the brace hits it.
 

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