Help diagnose a cabinet issue of mine (video content)

naturalkinds · #1 08-09-2010, 09:17 PM

Friends, allies, foes:

I have a bit of a cabinet issue here that I am hoping some of you might be able to diagnose. The cabinet is question is an 8 ohm Glockenklang Take Five 410 cabinet loaded with Volt drivers.

Purchased it from a friend and valued TB member, Dee-Man, a few months ago. When he had it, it worked fine. No issues. It arrived with excellent packaging in-tact, and, when I pulled it out, the cabinet was in near-mint condition. So far so good.

But one of the drivers started buzzing -- or it seemed to buzz -- no matter which amp I plugged into it. I swapped power cords, speaker cables and instrument cables and kept getting the issue. Tried it with three different amplifiers, and the problem still arose.

I took it to a tech in Savannah, who, if you read my last post, demonstrates his absolute incompetence when he charged me a $45 diagnostic fee and essentially said he had no idea what was wrong with it. (Yeah, I know...) He said it MAY or MAY NOT BE a busted driver. He also said that he had never heard of 32 ohm drivers, so I didn't really take him too seriously after that.

Anyway, the buzzing seems to have attenuated after he reinstalled the driver after testing it, but now I am experiencing what appear to be odd phasing issues. Notes that SOUND a bit out of tune to me, or carry a different character elsewhere in the room. It works fine enough for my reasonably loud rock rehearsals -- honestly, it does -- but the issues are still there.

I do not think that the driver is blown. But I might be wrong. I tried the 'press test', and couldn't feel the voice coil rattling under the dust cap when I played and pressed lightly. But I didn't try the 9v battery test to see whether it's dead or not... partly because I don't really understand how to do that test.

: )

Clip one: the day I got the cabinet. Lots of obvious buzzing here.

http://www.flickr.com/photos/naturalkinds/4877936348/

Clip two: after I brought it back from the tech. Obviously improved, but still with distortion you can hear, and some weird psychoacoustic note-wobbles that don't really translate in video.

http://www.flickr.com/photos/naturalkinds/4877940344/

Thanks for your patience, advice and expertise. I really do appreciate it.

Munjibunga · #2 08-09-2010, 09:28 PM

Make sure the screws/bolts holding the speakers are all tight. I had a similar problem with some PA cabs, and tightening the bolts solved the problem.

JimmyM · #3 08-09-2010, 09:28 PM

i listened with good headphones and it sounds fine to me. but go around and check and tighten up all your screws. i think he fixed the issue you had but it may just have a rattle elsewhere. or maybe you're hearing a rattle from something else in the room. they tend to sound like they're coming from the speaker sometimes.

**bass4worship** · #4 08-09-2010, 10:15 PM

I don't like that buzzing sound, It sound like the speakers not getting a clean source of power. it do sound like there a blow driver in there. Since each speaker is 32 ohm they are all in parallel. I would disconnect one at a time to fine the bad one.

**bass4worship** · #5 08-09-2010, 10:16 PM

You can use a ohm meter to check if the coil are shorted too. Check that speaker cable too..

JimmyM · #6 08-09-2010, 10:28 PM

wow, am i deaf? that's about as far apart as it gets

well maybe i just like that sound and i'm attuned to it.

rpsands · #7 08-09-2010, 10:35 PM

Ugh, that sounds like it could be the speaker wires rattling on the cone potentially -- easy fix, if that's it.

Get a cardboard tube and listen through it to find out the direction it's coming from - also make sure there's no air escaping from the cabinet anywhere but the port.

naturalkinds · #8 08-10-2010, 07:20 AM

Quote:

Originally Posted by rpsands

Ugh, that sounds like it could be the speaker wires rattling on the cone potentially -- easy fix, if that's it.

Get a cardboard tube and listen through it to find out the direction it's coming from - also make sure there's no air escaping from the cabinet anywhere but the port.

Thanks for the tip. Is the tube to help me hear I am selecting the buzzing as coming from the correct driver?

I do have a feeling it might be wire-related. When I took out the driver to have a quick peak, I noticed they seemed to be relatively long. I guess I should try to pin them back or something? I am also guessing that the weird note issues I'm hearing might be a consequence of sympathetic vibrations caused by the rattling of the wire... on the assumption that that's the problem.

At any rate, thanks to everyone for the advice, and thanks to Jimmy for not making me feel crazy by retracting his comment that everything sounded normal.

: )

I'll also make sure to tighten all screws, as per Munji's suggestion.

rpsands · #9 08-10-2010, 09:07 AM

Twistie/zip tie the cables and then use hot glue to hold them a reasonable distance away from the drivers (against a cabinet wall). S'how I roll

Listening through a cardboard tube seems to make the location of the buzz more clear. So if it was in fact a buzz of air spitting out through a handle or something that'd be another way to tell.

You might also want to feel around various weak points of the cabinet (speaker gaskets, handles, jack plate) and look for escaping air as you play.

A sine wave generator on a laptop might help; I've used that to diagnose these in the past. Set up a sine around 50hz and play it at moderate volume through the cabinet and you should get a pretty good amount of air going.

christw · #10 08-10-2010, 09:15 AM

To make sure all speakers are in phase... plug in a speaker cable and touch the leads of a 9v to the cable. + to the tip and - to the sleeve. All speakers should move outward in unison.

I'm in class and can't give a listen yet.

DWBass · #11 08-11-2010, 01:36 PM

Don't know if it's been asked already but have you changed the battery in your bass? That's the sound I get when my battery gets low or close to dead.

naturalkinds · #12 08-11-2010, 01:38 PM

It's a passive P. And this is the only driver that seems to be making the sound. Thanks for the note, though.

christw · #13 08-11-2010, 01:44 PM

It might be a mechanical buzzing, actually. The voice coil might be warped or damaged and hitting/rubbing inside. That's what my guess is. Does the buzz's frequency change with the note's frequency? Example... does it sound different from an E to a G?

DWBass · #14 08-11-2010, 01:45 PM

Quote:

Originally Posted by naturalkinds

It's a passive P. And this is the only driver that seems to be making the sound. Thanks for the note, though.

10-4! I say the driver is toast then!

naturalkinds · #15 08-11-2010, 02:03 PM

Quote:

Originally Posted by christw

It might be a mechanical buzzing, actually. The voice coil might be warped or damaged and hitting/rubbing inside. That's what my guess is. Does the buzz's frequency change with the note's frequency? Example... does it sound different from an E to a G?

Just tested it. Yes. The buzzing frequency changes from E to A to D to G.

**bass4worship** · #16 08-11-2010, 02:12 PM

Bad speaker..

Wes Whitmore · #17 08-11-2010, 02:13 PM

Take the driver out and look at the tinsel leads connecting the voicecoil to the speaker terminals. Make sure that they are not resting against the cone. If they are, bend them so they are not. Also, you can lightly move the suspension in/out with your hand and see if there is rubbing of the coil in the gap, while it is out of the cab. It really shouldn't rub or make a noise. You don't need to move it much. You could swap a driver from the opposite corner of the cabinet and see if the sound moves or stays in that location as well, but it sounds like all of those drivers should be identical and should be in parallel with one another. I assume that they all play at the same volume. Just investigate that driver outside of the cabinet a little and let us know what you find.

rpsands · #18 08-11-2010, 02:14 PM

If you took the speaker out and it's still buzzing it's probably the cabinet, or speaker wire inside the cabinet. Make sure the wires are all secured, then start feeling for air leaks on the cabinet. Use a tone generator on a laptop or similar to generate the buzz, then start tracking it down.

If it's an air leak you'll feel a breeze coming out from the edge of a speaker or a jack plate or something. Get your hand wet and it'll exaggerate it.

johnk_10 · #19 08-11-2010, 02:17 PM

it sounds like the voice coil is rubbing to me, so it's time fro a recone on that one.

christw · #20 08-11-2010, 02:19 PM

Quote:

Originally Posted by naturalkinds

Just tested it. Yes. The buzzing frequency changes from E to A to D to G.

I'm with johnk. I'd bet the voice coil is rubbing. That's why it changes pitch with the frequency of the note (and the subsequent movement of the cone).

Quote:

Originally Posted by rpsands

If you took the speaker out and it's still buzzing it's probably the cabinet, or speaker wire inside the cabinet. Make sure the wires are all secured, then start feeling for air leaks on the cabinet. Use a tone generator on a laptop or similar to generate the buzz, then start tracking it down.

If it's an air leak you'll feel a breeze coming out from the edge of a speaker or a jack plate or something. Get your hand wet and it'll exaggerate it.

I think you misunderstood. The speaker is buzzing.