• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

HELP!! Amp "farting"

#21
I have a PF-500 and have experienced this as well. In my case, it wasn't my cab at all, nor was it neccessarily the head. Do you use any pedals? I've found that gain structure is usually my culprit, even though the clip light isn't flashing much on the PF-500. Making some adjustments to the gain levels in pedals or turning the gain down on my head fixes the problem.

Initially, I noticed this playing at home, then started noticing it through different PA's on gigs, and I know I was no where near maxing out the PA's. That led me to mess with the gain on the pedals and/or head and...voilla!

Hope it helps...
 
#23
awilkie84 said:
So, realistically, my cab should be rated at DOUBLE my head's value!? That seems a bit ridiculous...and is really going to drive up the cost of my rig. Turning down below 1:00 means I'm not heard with the guitar/drums. I really hope it's more of a problem with the speakers/wiring than it is head/cab compatibility. :(
Click to expand...

What is ridiculous is BASS speaker cabs get rated at 1,000hz for power handling. Most of what you want for bass guitar is between 50Hz and 300 Hz. Those lower frequencies are where the speakers are worked really hard. The best speaker cab is MAYBE 5% efficient at converting electrical power (watts) into sound. Watts don't make sound, speakers do. When you trade an efficient cab at 8 ohms for an inefficient cab at 4 ohms you get more "power" from the amp and less sound from the cab. Hard lesson to learn? :)
 
#25
You may just need more speakers to get loud enough, though a typical 115+210 should be enough for a lot of things. Something is odd here. How are things set up in your practice room? Is your sound blowing by your knees while the guitar is hitting you in the ears?
 
#26
TwoRivers said:
I have a PF-500 and have experienced this as well. In my case, it wasn't my cab at all, nor was it neccessarily the head. Do you use any pedals? I've found that gain structure is usually my culprit, even though the clip light isn't flashing much on the PF-500. Making some adjustments to the gain levels in pedals or turning the gain down on my head fixes the problem.

Initially, I noticed this playing at home, then started noticing it through different PA's on gigs, and I know I was no where near maxing out the PA's. That led me to mess with the gain on the pedals and/or head and...voilla!

Hope it helps...
Click to expand...

My pedals are all true bypass, and it happens with them all turned off. I'll try removing them from the signal chain & see if that helps.

KeddyLee said:
You know you never mentioned pedals (at least I don't think so).

If you are using a DI box like the MXR M80, that would be sending a pre-amp to your pre-amp and will definitely cause farting.
Click to expand...

No DI. Korg PitchBlack -> EHX Bass Big Muff Pi -> Corona Chorus -> Amp

B-string said:
What is ridiculous is BASS speaker cabs get rated at 1,000hz for power handling. Most of what you want for bass guitar is between 50Hz and 300 Hz. Those lower frequencies are where the speakers are worked really hard. The best speaker cab is MAYBE 5% efficient at converting electrical power (watts) into sound. Watts don't make sound, speakers do. When you trade an efficient cab at 8 ohms for an inefficient cab at 4 ohms you get more "power" from the amp and less sound from the cab. Hard lesson to learn? :)
Click to expand...

Reading up on the 2 cabs, the frequency response on both cabs goes below 50Hz (30Hz on the Hartke and 40Hz on the Traynor). The Traynor has 3x the top end of the Hartke, too. Not that the top end really matters. So, I'm not seeing where efficiency comes into play here, unless the resistance dictates the efficiencies.

My Traynor Specs
Invalid Link Removed

BFunk said:
Yes, this is the unpleasant reality of bass sound reinforcement. One way to address this issue is to significantly reduce the amount of lows we send the cab. But this is often directly opposed to our sonic goals.
Click to expand...

I guess I'll have to give this a try. :S

will33 said:
You may just need more speakers to get loud enough, though a typical 115+210 should be enough for a lot of things. Something is odd here. How are things set up in your practice room? Is your sound blowing by your knees while the guitar is hitting you in the ears?
Click to expand...

The 2x10 portion of the cab is at my waist height & the 1x15 is around my shins. Are you suggesting I elevate the cab, or angle it to point up? It's not a small cab. lol
 
#27
Test the cab with a battery and see if all the speakers move and move all in the same direction.

I also think you're putting too much faith in speaker specs and amp knob position settings. All that stuff is either very inaccurate or a moving target.
 
#28
awilkie84 said:
Reading up on the 2 cabs, the frequency response on both cabs goes below 50Hz (30Hz on the Hartke and 40Hz on the Traynor). The Traynor has 3x the top end of the Hartke, too. Not that the top end really matters. So, I'm not seeing where efficiency comes into play here, unless the resistance dictates the efficiencies.
[/URL]
Click to expand...

It sounds like you're confusing frequency response with efficiency. A more efficient cab will give more volume for the same power.
 
#29
flip it over and see if the "farting" is more or less noticeable. If less, the tens are the culprit, if more, the 15. Is this cab used? Could it be partially blown. Speakers are rated rms = which is root mean square. The mathematical limit based on theil small parameters. Program which is it's "practical" mechanical limit. Usually max is whatever they want. The better brands post what the max wattage over 8 hours of program material. In my experience in pro audio, when I blow speakers they pop a few times first. Thats the mechanical limit, the bobbin that the voice coil is wrapped around slapping the magnet. That is because of too much wattage, or clipping. Usually If I pop it loud enough I've distorted the bobbin bad enough that the speaker will still work fine and sound good till I hit moderate volume, then (I assume) because it's distorted, it begins to distort the cone, thus distorting the frequencies it's reproducing.



EDIT: Dreamsinger reminded me; when the dust cap starts to unglue (a hot day in a car can do it) it'll sound just like farting. It's like adding a port in the middle of the speaker, and throws the cab out of tune.
 
#31
I'm interested in the comment you made about not hearing the 10's when you play. If you can hear sound easily coming from that ankle height 15, but you don't noticeably have roughly the same volume from those10's you've got speaker problems.

Also, those 'specs' are pretty empty as listed on the manufacturers' website. They're basically ad/sales copy without them adding real information.
 
#33
This important spec is missing from the Traynor:Sensitivity: 98 dB @ 1 W/1 M listed on the Hartke. That spec is how well electrical power to converted to sound level. If one cab is measured at 95 db @ 1 watt/1 meter it will need twice the power to match the output of a cab at 98 db @ 1 watt/1 meter. Average 410 cabs run around 101 db @ 1 watt/1 meter. Higher number in db is better.
Not slamming the Traynor at all, just saying the important info to compare the output of the cabs is not there. The frequency response is only a small part of the story.
An 8 ohm cab with 101 db sensitivity will be louder than a 4 ohm cab with 96 db even with a SS amp all other things being equal (total cone displacement: size of actual piston area and the amount they can travel).

Manufacturers capitalize on the fact that most do not understand the variables. Most think "power is sound" and that is just not true.
 
#37
awilkie84 said:
But I'm getting the opposite. Have to crank up the volume another 2 notches to match outputs from the Hartke to the Traynor.
Click to expand...

Don't confuse impedance (ohms) and frequency response with how well sound is produced by each watt of input (sensitivity). They are three different things.
Your statement would indicate the Hartke was better at turning wattage into sound and you made a move backwards in sound output by trying to "get all the watts" from the amp. Sorry.
 
#38
The simple battery test will confirm if all the speakers are wired up correctly and working without having to take anything apart, other than pulling off the grillcloth frame if it has one. You just need to be able to see them.
 
#39
B-string said:
Don't confuse impedance (ohms) and frequency response with how well sound is produced by each watt of input (sensitivity). They are three different things.
Your statement would indicate the Hartke was better at turning wattage into sound and you made a move backwards in sound output by trying to "get all the watts" from the amp. Sorry.
Click to expand...

Thanks for reinforcing what I was trying to get across to the OP. He seems to have discounted all that I said! <sigh>
 
#40
BurningSkies said:
You've found the limit that your cabs can take.

You can probably figure out which one has reached its excursion limits if you try to reproduce what its doing (try putting the 15 on top of the 210 and see if that makes it more obvious which one is running out of gas).

With those cabs, your best bets to avoid over excursion are:
-Turn your volume down.
-Reduce the amount of bass from your EQ.
Click to expand...

I vote for this as best answer. A cab can only get so loud before it distorts. It sounds like you need more/better speakers.
 

Latest posts

Top Bottom
Back