The Speaker Fart

Check the batteries on the bass?

 

perhaps add eq at the amp instead of before it?

 

Either your bass signal is too hot (too much bass boost ) for the preamp or you are running out of headroom due to too much bass. Rolling off some bass will cure it. Try boosting the low-mids if you want more body without taxing the amp too much at loud volumes. I feel that the bass knob on most amps should be left flat and only cut/boosted to compensate for room accoustics.

 

I had sorta the same issues with that cab, XB-2 w/GBE750. I think like me, you like to boost the bass some, I set the LF knob on my 750 at about 2:00 cause I like that tone. And I bet your Bongo is sending a pretty hot signal too. At a couple big room gigs it would fart out some and I was lighting the clip lite quite abit, no bueno. Started using less lows and more mids and it helped but I still try to sneak up that LF knob up now and then. I also added a EBS multicomp and that seemed to help with the clip issue alot.

But I recently traded in the XB-2 for a NV610 and I used my new Peavey Cirrus 5er at a gig last week. Even with the compressor on Im back to clippin the amp with this new cab and bass. It was fairly loud but the amp settings were all pretty flat, again cept for the LF knob at 1:00. Maybe the 18 volt pre in the Cirrus is sending too hot a signal to the amp. Just got the PV and now gonna try out the NV215 instead of the 610 this weekend so I need to learn some new settings I guess. I'll try backing off the bass' preamp settings and see how that works out but Im still wanting to try to get back some more lows for my taste.

 

is it possible that you accidently touch the pick-up with the string?

 

Hi Ernie-
I'm definitely curious as to the results of running the GBE1200 through the NV215 cab. I have had issues with the clip light on the GBE1200 coming on with the amp EQ section set flat, no global EQ shaping, Active OR passive bass with the 'Active' switch engaged, and what I feel to be moderate volume, through either a Whappo Jr cab, or an Epi ul-410.
I have spoken to Hasbeen and Agedhorse about this issue, along with Genz Benz support. Great guys. I was told by one of te Genz Benz techs that the clip light should come on at 6dB before clipping, which, in my understanding, when the clip light first comes on, you wopuld have to double your volume twice before the amp actually clips, thereabouts. My gut feeling is that, even though this 'premature' clipping issue is rare among owners of this amp, I have heard about it before, maybe a few of the units that went out had a sensitivity issue with the clip light, where it comes on prematurely? Not sure if that's the case. I hear no distortion, but seeing that clip light on as often as I see it on gets me nervous.
I absolutely love the amp, by the way. This has just been one of those nagging issues since I started playing it. I bought it brand new.
Let us know how it goes!
Scott C

 

Wow so your clipping the 1200 fairly easily huh? And that was the amp I was thinking of upgrading to to avoid my clip issues. But yes, I've read a few threads here where the genz guys say there is still more headroom left even after the light comes on. But Im like you and dont like to see it flash that regularly. I do better with my passive Jazz 5 but I still keep in on active mode with that bass. So I guess if they say its cool then I'll go with that.

Now I do like to set my LF shape knob at about 1:00 or 2:00, the rest of shape, EQ master/gain knobs stay right at noon, limiter button is in, active button in, it gives me the tone I prefer. But when I dig in I see that lite start to flash well I begin turning down knobs on amp & bass. I do use my bass EQ quite abit too, so maybe I ought to do the amp more and leave bass flat or vice versa, but I just use my ears and I know what I like to hear. Of course Ive not had the speakers farting out with my settings but it might get a little muddy as band gets louder thru the nite, so I do need to be cool at that point. But that was mainly using the XB-2 cab alone. When I use 2 cabs the clip really seems to calm down. But for now Im trying these Berg cabs stand alone to see what they can do. Well here's to tweaking the heads and hoping we dont blow a cab. I figure at some point I'll get it right. Peace, ernie.

 

Based on the size of the amp the speaker is the likely weak link. A speaker with adequate output and frequency response to meet your needs wouldn't need the bass EQ full up.

 

Check the quality of your speaker cables and make sure they are all seated properly out of the amp and into the cabinet..
I starting getting farts and clipping and went crazy until I notice the cable wasn't all the way into the input of my cabinet and once pushed all the way in she was perfect..

 

Double your power twice. Double your volume twice would be 20db.

 

Ok, I'm an idiot, I had that completely wrong.

 

+1 I was getting some speaker farts when I played hard. It took me a while to figure out where they were coming from. My floating thumb was pressing the low string into the pick-up magnet.

Do you have exposed pick-up magnets?

 

I had this same problem with my Genz Benz 410 XB2...I bought that cabinet thinking surely it would rock the house...they just look like they can handle anything you throw at them...hooked it up to my Peavey TMAX...FART FART FART FART every time I hit my B-string..I tried every thing I knew to fix the problem, even tried several other heads... no luck.. i was sick over it...(I have a GB 15" cabinet too that sounds great though), so I hauled it off on Ebay...and bought a Peavey 412 TVX... total balls!! Sounds incredible with the TMAX...I have been incredibly happy ever since...and I don't have to use the 15" cab anymore either. But I guess I didnt learn my lesson cause later on down the road I picked up a used GB 210 XB to put with the GB 15" cab...and guess what....Fart-o-rama...its in the corner collecting dust now.

 

Withe the output limiter switched ON, you have 6dB of limiter compliance. This limiter emulates the compression and harmonic increase that a tube power amp exhibits when it overloads.

6dBv is 4x the power between the point the clip/limit LED turns on and the power amp actually clips. This is true when the output limiter is switched ON. With the limiter switched off, the clip LED turns on a couple dB before actual amp clipping occurs.

The reason for 6dB = 4x the power is due to the Vsquared term in the power equation.

APPROX. double the "VOLUME" would be ~10dB power BUT this is a very rough estimate as the ear is not very linear so it depends on the frequency spectrum as well as the power level. 2 (major) variables affect our perception of volume.

 

Regarding farting speakers, I have seen quite a few speakers by ALL maufacturers that show mechanical damage from being driven with too much power generally at frequencies below the cutoff of the cabinet. When a speaker is driven below the cutoff of a cabinet, the driver no longer operates as a linear element and the power handling decreases quite rapidly. I know several of us, including Bill, have discussed this in detail. This is a good reason to know how a speaker was used if buying used, as once the "spring" is stretched out and the mechanical damage is done, the only solution is to recone or replace the drivers.

Headroom is ok as long as it remains headroom. Unfortunately, this is rarely the case in the real world.

 

would it be safe then to un-do the limiter button to get the lows/more overhead Im wanting with these cab(s)? I've always left the limiter button in and even the active button in with passive basses. This so that I dont chance going beyond the clip warning light and into nasty, dirty, dangerous clipped speakers where damage can occur. I know of course damage can occur before that, but Im trying to take precautions not to get to that point. I asked this question in another thread but maybe did not pose it correctly considering the replies I got.

I've used the GBE750 with 2 4 ohm cabs and have avoided clipping the amp and getting good lows,375 watts into 2 4ohms cabs, as opposed to 625 watts into 1 4 ohm cab. And I know about the more speaker area offering that benefit with more cabs and all. But I expected the quality of the cabs Im using, GB and Berg NV's, to offer me more in terms of stand alone cab use without getting into the danger zone so readily.

Am I doomed to hauling 2 cabs to my gigs? A little tounge n cheek here but you know what I mean. Am I not using this head correctly to let it be all it can be, no knobs can go much past noon or 2:00 and there is so much knob area there before I even approach eleven, (11 LOL) do I need use only passive basses? I really like the tone with my 2 212T cabs but I thought I could find or get close to that with one of the Berg cabs as a stand alone. Thanks all for any input. e.