GK MB212 rattle and what to do about it...

[azureblue]

I have been playing mostly jazz in the 5 months I've had my MB212, so I have had no opportunity to turn it up. Yesterday, I did an outdoor "blues" gig and had all the knobs on about 12:00. And it rattled, a resonant rattle- that is, it would change pitch and volume with different notes. The noise was pretty loud, too, not a small buzz at all. And it still did it when it was lifted off of the ground. I know what a blown speaker sounds like, and this did not sound like that at all. It sounded like there was something loose somewhere. Bum. I did an outside inspection, looking for loose screws, etc., and found that the top of the speaker grill flexes in the middle, and rubs on the cabinet, making a squeaking sound. I am not 100% sure this is the source, but it seems like it to me.

So, being under warranty, I called GK and described the problem, and asked what I should do. They suggested I put some silicone there, but, if I did that, I would void the warranty. Uh, for a blob of silicone? Or I could send it back to GK or "an authorized repair station", then be without an amp that I need at least four times a week and wait for a hopefully non - rattling version to be exchanged for it, or mine fixed. That is unworkable for me.

So a few questions:
has anyone else here had that problem? If so, what did you do to fix it? My thoughts are that there should be a brace at that point to stop the flexing.
Am I just getting BS'd by the GK warranty / repair dept.?
Any advice / input on on how to best handle this?
Thanks

[jelwood]

Could try slipping a piece of paper in between the grill and whatever part of the cab it's rubbing up against, see if it changes anything. Won't void the warranty either

[azureblue]

Thanks. Shoulda thought of that.. Duh on me.... Low caffeine level, I think..

[greenboy]

Been more than a few threads I think that talk about it. Not being an owner I didn't keep track of them though.

[azureblue]

Thanks- I did a search, but most of the rattle complaints were about the MB210, unless I missed something.

[armybass]

I had the MB210 and found that the initial rattle was from loose screws. I titghtened them down and the problem seemed to go away then I started hearing what you have described and could not find the source of it.

[sevenyearsdown]

I had some bad vibration issues on an ashdown once. The logo that was riveted to the grill was the culprit. I cut some pieces of softer weather stripping and stuffed it under the vibrating parts. It took care of the problem.

Maybe you could try the same thing if there is room enough to stuff some in there?

[azureblue]

to stuff it, right now.. :-)
Got some foam sheet, cardboard, and paper, so I hope I'm right and one of these shuts it up, without incurring the wrath of the GK warranty gods..

Well, that didn't work. It's not the grill, for sure. It is a rattle but it sounds like it's coming out of both speakers. I'm going to see if there are some loose screws, but I think it's a manufacturer's defect, maybe a bad internal brace. Time for a return, I think, but it's an hour and a half to the service center......

Didn't get as far as the screwdriver. I fired up the amp, had somebody play some low notes, and put my hand on the back. It was flexing like rubber. When I pushed in on it, the buzzing sound changed, so I am guessing there is a problem with the back brace not being properly glued to the back. Grrr.. For want of a nail and glue....

[5port]

Time to remove one or both speakers and check to see if the speaker wires are interfering with a speaker cone (touching). Its more common than you may think.

[metallicafan18]

my NEO212 cab rattles as well, and I have never been able to fix it. It drives me crazy.

[jelwood]

You are right it is probably a factory defect as all of GK braces their cabs for maximum efficiency (least internal vibration of the enclosure). If you watch their factory video on youtube you will see that Bob smacks the prototype cabs with a mallet to check how their bracing design is coming out. My neo 412 developed a rattle because I left it in the car overnight, let me tell you it drove me crazy, I tightened all the screws, took the speakers out, looked for wires rubbing up against the speaker cones, looked for maybe a loose piece of wood in there, whatever, and nothing. Then I too applied pressure to certain parts of the cab while I was playing through it and I could get the rattle to stop that way which told me that the hot and cold temperature gradients in the car had gotten to her. So I went and bought some Elmer's carpenter's wood glue (I'm pretty sure even Wal Mart carries that stuff) and I flowed some glue into the bracing joints that I thought were the culprits. Nothing! So then I flowed glue into every single other joint I hadn't touched yet and...success! Probably not the best way to save on glue but hey.

[sevenyearsdown]

I'm not trashing GK, because they make some really nice stuff. However reading threads like this, and some other complaints I've read here about the new MB combos they've made steered me away from them and straight to Genz Benz. It sounds like GK has cut some corners to make these things affordable.

[azureblue]

is telling me that I should take it to a service center, which is an hour and a half (one way) trip, to see if the SC can fix the rattle. The SC says to drop it off and come back the next day, which I understand, but a heck of an inconvenience for me - a total of 6 hours travel time plus gas. And I have to play tonight - fortunately a jazz gig, so the amp won't be up loud enough to rattle, but still. If the SC says no, then I can send it to GK, THEN they will send me a replacement, with 5 to 7 days shipping time. I am unhappy that their warranty dept. is not stepping up and trying to work with me on this. When I called them, and tried to get an idea of the best and worst case scenario, well, let's just say they were terse. I need an amp four days a week for gigs. So I will be out the gas and travel time to the SC (twice) then the cost of packing and shipping the MB, then amp rental, which is gonna total about half the purchase price of the MB.

And I just discovered the cat peed inside the MB212 shipping box..... Murphy's law......

I can fix it, but I am concerned that there may be more wrong with the MB, and, if I fix it, I will, of course void the warranty and I am up the proverbial creek, if something else goes wrong.

If I fix it, I'll probably have to remove the center brace and replace it with something more stout. I probably could slip some shims into the gap between the back and the brace and glue the heck out of everything.

Not good. Certainly not for a 5 month old amp. A shame too, the MB is a really great amp, and I've owned & played on a lot of bass rigs. I'm not trashing GK, as if they started out to sell a flawed product - it 's easy to see that they subbed the cab builds out to a company who did bad work, but, still, in the name of good PR, they should do a mea culpa and make good.

[baileyboy]

From my experience, I think it is always best to hold off on embracing new amps, etc when it first hits the market. Once it has been in the market place for a couple years and only if it has an excellent track record, it is worthy of purchase. I did not jump on the MB212 express, nor the Ampeg Micro, for this reason. Besides, any gear not actually assembled in the USA I am highly wary of.

[96tbird]

Originally Posted by baileyboy

From my experience, I think it is always best to hold off on embracing new amps, etc when it first hits the market. Once it has been in the market place for a couple years and only if it has an excellent track record, it is worthy of purchase. I did not jump on the MB212 express, nor the Ampeg Micro, for this reason. Besides, any gear not actually assembled in the USA I am highly wary of.

Because USA assembly workers are as reliable as the warranty department and management of the company that are indifferent to the OP's problem?

A warranty is a warranty, no matter where they have their products assembled.

Dude, tell that warranty department that you will glue and screw that cab together yourself and they had better honour the warranty or you'll file a complaint with the BBB. That has made companies stand to attention for me before when I have mentioned that in cases where I have a problem, heck my dad had Ford Motor Co.'s attention before by doing just that, no kidding!

Oh and just in case the baffle is MDF and you pull the speakers, hit the screw holes with CA glue (krazy glue) to harden the theads so that doesn't become a problem

[Slackerprince]

Been there:

The GK MB210 RATTLE/BUZZ/VIBRATION Thread

The resolution is post #35.
I'm not digging the tone and find the amp boomy, so I'm moving to the Genz Streamliner 600 and probably an Avatar TB153, or if I can swing it, a Genz NeoX212.
Good luck with your problem.

S

[azureblue]

got me some info that the center brace is a piece of plywood that is edge nailed and glued into place. From my experience, braces should be solid wood, glued and screwed. Got to talk to the SC - Great guy, knows his stuff, took a bunch of time to talk with me about the problem, and he thinks it is the brace, too. I owe him a pizza for his time and advice. To GK - you know, you could have been as helpful he was, and saved some ruffled feathers...

Now, I must decide if I want to put in the two round trips to have him fix it, or DIY, and void the warranty..

If I was going to offer advice to GK, I'd say up the price of the MB series to pay for a reliable cabinet maker. These are great combos and cabs - they just need some good old QC. I'd buy another one.

Slacker- thanks for the thread link. Not much about the MB212, but I can see common problems and solutions I could use.

[96tbird]

Plywood is more dimensionally stable than solid wood and that's why it is used. All joins should be glued and either screwed or nailed. the screws and nails have little effect once the glue had cured, they are merely interim clamps for the glue. Carpenter's aliphatic glue is remarkably resilient and durable against vibration and stressing, the wood will fail before the glue will, as long as it is not filling a large gap.

[rpsands]

PL premium.

[96tbird]

Originally Posted by rpsands

PL premium.

sub floor adhesive, outstanding for new construction, doesn't flow well for a repair in a tight gap though.