3015 buzz on C# only?

steamthief · #1 03-08-2011, 12:28 PM

I installed a brand new 3015 into a cab a couple of weeks ago, and during the last couple of days it's developed a definite buzzing when playing C# on the A string.

I've determined that the speaker wire isn't touching the cone, and the driver is screwed in as tight as I can get it.

Anybody have any suggestions of what may be wrong? May I have gotten a dud driver?

BurningSkies · #2 03-08-2011, 12:33 PM

Check the tightness of your handles, of the jackplate and any internal bracing. My springloaded side handles on several of my cabs can rattle or buzz if not situated quite correctly.

lbwdog · #3 03-08-2011, 12:34 PM

A buzz can drive you crazy! Any number of things could be the cause.
I had to remove and reinstall almost every component (some twice) on my LS1503 to quieten it.

kayakbass · #4 03-08-2011, 12:38 PM

Your CABINET may have a rattle. Some cabs develope noises from age/use/vibration...fluttering sounds, buzzes, rattles... If there's any hardware on the cab ( handles, corner covers, castors ) check those and tighten them down.
Of course it COULD be the driver...

steamthief · #5 03-08-2011, 12:43 PM

I tightened everything, hardware-wise, when I damped the cab, but I'll go over it again. The cab is an OBC115, which is built like a tank, and it never emitted any buzz with the factory Delta driver.

The driver I bought from new from Amazon looked to be repackaged, based on the loose masking tape on the box, and it didn't come with any paperwork regarding specs, warranty, etc. from Eminence. Is that standard practice? I've never bought a raw driver before.

lbwdog · #6 03-08-2011, 12:47 PM

I didn't get any paperwork in my 3015LF box. Make sure you tighten the driver screws evenly in a star pattern.
And...DON"T OVERTIGHTEN

steamthief · #7 03-08-2011, 01:17 PM

Well, I went over all the hardware again, tightened two corner protector screws a hair. Pulled the driver, re-checked that no wire was close to the cone, and put the driver back in.

I listened to the cab at ear level this time, the buzz has moved from C# to C, and now E-F# on the E string sounds buzzy as a bonus.

I hand tightened the screws in a star pattern until they were really tight. I'll try backing them out and re-tightening them a little looser to see if there's any difference.

billfitzmaurice · #8 03-08-2011, 01:18 PM

Quote:

Originally Posted by steamthief

May I have gotten a dud driver?

Not likely. Drivers that are bad are usually bad on every note. You have something in your cab vibrating. It might even be a loose bolt or nut caught up in the driver.

Quote:

The driver I bought from new from Amazon looked to be repackaged, based on the loose masking tape on the box, and it didn't come with any paperwork regarding specs, warranty, etc. from Eminence. Is that standard practice?

It is not. If you bought it from a gray market source you probably have no warranty.

rpsands · #9 03-08-2011, 01:18 PM

Feel around all the handles and such for air leaks. Get your hand wet beforehand, will make it easier to feel

Remember, the Factory driver is going to be capable of a lot less displacement, so the 3015 will be louder lower, especially down below E. With the increase in displacement is an increase in air flow out of the ports, and air flow against any poorly sealed connectors.

Long story short, increase in displacement can result in exaggeration of any leaks or buzzes due to increased air flow and increased volume.

If it's only C# on the A string, but not at the octave of C#, then it's likely an air flow issue - either port area too small, tuning too high, or a leak.

If it vibrates with any C#, chances are it's a vibration of some kind.

Make sure the gasketing tape is there around any handles/cups/etc, and also make sure the woofer has enough gasketing around the rim. Sometimes stock drivers come with poor gasketing.

greenboy · #10 03-08-2011, 01:21 PM

Under-braced cabs or cabs where a brace glue line has broken a little can make it all the more maddening. So can plywood voids. Higher-force drivers can really reveal faults. Sometimes too, you'd swear something is coming from a cab when it's actually something else in the room - even when your ear is real close to the thing.

One reason it's nice to have a frequency generator to troubleshoot with.

steamthief · #11 03-08-2011, 02:05 PM

Thanks for all the help thus far, guys. I took the cab into a different room to see if that was the issue, but the buzz remained. There was definitely airflow coming out of the two RCA jacks, so I put in a couple of earplugs, which helped somewhat, but the buzz is still there.

I'll pull the driver again a look for anything loose - is there anything I should NOT touch regarding the speaker innards? I'm in uncharted waters here. I'll also pull a bit of the damping closest to the port.

Since there is no airflow coming from the handles, is it necessary to check the gaskets? Also, should the gasket on a new 3015 be good to go? Finally, even though the driver has space for eight screws to attach to the baffle, the cab has only four screws to keep it in place. Could this be the crux of the biscuit?

rpsands · #12 03-08-2011, 02:14 PM

If there's no air flow from the handles, leave'em. The gasketing on a new 3015 should be fine, but if it's a repackaged one or something I'd double check it. Some people swear by peeling off the stock gasketing tape and putting their own on, but I have never had an issue with the Kappalites.

I don't know how much of an issue it is but I would *definitely* use 8 screws. Leland @ SpeakerHardware has Recex screws which are excellent for this application.

BassmanPaul · #13 03-08-2011, 02:22 PM

Quote:

Originally Posted by rpsands

I would *definitely* use 8 screws. Leland @ SpeakerHardware has Recex screws which are excellent for this application.

I agree - there is a reason for having eight holes in the frame.

BurningSkies · #14 03-08-2011, 02:52 PM

I agree. With a speaker that can produce high SPL, use all 8 of those mounting holes. I also don't agree that you shouldn't tighten the speaker down well...just do it evenly.

steamthief · #15 03-08-2011, 03:34 PM

I've got it figured out - based on the improvement in the buzz based on plugging the RCA jacks, I figured airflow, or lack thereof, was the culprit. I had a eight-inch-long piece of 1" foam covering the handle cup in close proximity to the cabinet port. I yanked it, put the driver back in, and the buzz disappeared.

It's amazing that a little strip of foam taking up mere square inches can have such a negative impact on a cabinet! Another tidbit I found interesting is the difference those little foam earplugs have on the cab's tone. Without them it was wooly, but when I put them back in, the low end just tightened up dramatically.

I will be getting the parts needed to attach four more screws, pronto!

Thanks again to everybody for your suggestions!

steamthief · #16 03-09-2011, 06:53 PM

All was good for about two hours of playing, but the C# buzz came back on both the E and A strings, so it looks like a vibration issue.

I need to get the four additional screws to secure the driver tonight. The four existing screws have threaded inserts in the baffle - are the Recex screw a better choice?

I also noticed a couple things that may be causing vibration. On the jackplate, the screws that secure one of the Speakon jacks to the plate barely catch the thread on the plate itself. Could this be a cause? I applied Loctite to those screws to secure them.

Another oddity I found is that one of the screws that attaches the jackplate to the cab is longer than the other three. If the longer screw was used in one hole, then when reattaching the jackplate used in another hole, could a void in the plywood have been created? If so, what should I use to fill the potential void?

Interceptor · #17 03-09-2011, 07:46 PM

The best approach to filling a screw hole is to glue in some toothpicks.

I like threaded inserts (t-nuts.) They are also easy to find at a hardware store.

DukeLeJeune · #18 03-09-2011, 11:03 PM

If the buzz persists, you might try taking the speaker out of the cab and playing it at greatly reduced volume, carefully turning the volume up to see if the buzzing sets in. This may help you home in on the source of the problem.

Note which part of the box the input terminals are facing when you take the driver out. If the driver doesn't buzz in free air, when you put it back in, rotate the driver so that the input terminals face in the opposite direction. It is possible that a combination of factors is giving you some voice coil rub on those notes, and if a minor suspension system asymmetry is part of it, rotating the driver may help.

I was getting some buzz on some notes on one of my prototypes, and had to relocate my ports to fix it. Hopefully that's not the case for you.

steamthief · #19 03-10-2011, 10:59 AM

I'm pretty sure I've located the source this time - one of the braces in the port lost its adhesion to the outer wall of the cab. I'm hoping that my application of Liquid Nails, and use of my OBC410 sitting on top of the fifteen in lieu of a clamp, will solidify the bond of brace to cab.

I've been rotating the driver each time I checked for buzz, but I think the port brace is the culprit. I'll be getting four t-nuts today, and hopefully this will be the fix so I can just play my darn bass.

rpsands · #20 03-10-2011, 11:29 AM

PL Premium from Lowes.