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Speaker "farting"

L

LZBass

Jul 24, 2009
28
0
Illinois
#1
OK... I read a lot about speaker "farting." I've even heard "farting" from my SWR LA15. My question is: What causes a speaker to "fart?" -- And be nice !! --

Is it clipping, over driving, mismatched parameters, damaged speaker, ...something else?

Thanks for helping a newbie out!
 
#2
Farting is caused by driving the speaker beyond it's mechanical limits.

The cone can only travel so far, so feeding the speaker either too much power or too much low end EQ'ing will cause the cone to reach the limit of it's travel and make a distorted "farting" sound.

Too much of this will cause mechanical damage to the speaker in the form of cone creasing, cone or spider ripping/seperation, or coil damage.
 
#3
It can be several things but I believe a common one is you are asking your amp to provide more then it has to give. If you turn up the bass or low knob on the amp as you play louder andlouder turning the volume knob up you might find at some point the speaker might start to fart. it could be the amp is being pushed to far if its a low power amp or the speaker is pushed beyond it ability to reproduce the very low frequencies that you are sending.
 
#5
I agree that over-driving a speaker is the typical source of the distorted tone called "farting," but a speaker can accurately reproduce a distorted tone originating from one (or more) sources besides the speaker itself. These include the instrument electronics, onboard preamps, effects, main pre, and power amp.

Furthermore, I recall once when a speaker in my goliath II 410 stopped working and all the others started farting at low volume. I was pretty sure I had fried the drivers, but it was a loose speaker wire in the cabinet, and much easier to fix than diagnose. :D
 
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#8
Well, for me, my carvin cabs needed a lot of power to run enough volume for me to get above the guitar and drums. But since I could only biamp because of the ohms ratings of the cabs, I was only getting 225 watts out of a 600 watt head so I was trying to compensate for less volume by boosting the lows, which caused it to fart out, what I should have done was cut some of the lows and boosted some mids, I just didn't have enough headroom from the amp...
 
#10
Rick Auricchio said:
Jim, with one driver dead, the others probably were overworking to take up the slack, which is why they farted out.
Click to expand...
It was the dead driver acting as a passive radiator, which raised the tuning frequency of the cab and unloaded the remaining drivers.

I had a small combo that had a 10" in a sealed box. I upgraded the speaker and it started farting-out. I ported the back of the box and got relief!
Click to expand...
Which shows to go ya' that you can't just drop any driver into any box and have it work. They have to be matched. In the above example with one dead driver the remaining three and the cab were no longer in synch, and he's lucky he didn't end up damaging them as a result.
 
#11
Bass_Pounder said:
Farting is caused by driving the speaker beyond it's mechanical limits.

The cone can only travel so far, so feeding the speaker either too much power or too much low end EQ'ing will cause the cone to reach the limit of it's travel and make a distorted "farting" sound.

Too much of this will cause mechanical damage to the speaker in the form of cone creasing, cone or spider ripping/seperation, or coil damage.
Click to expand...

This ^^^.

While "farting" is a mechanical phenomenon, clipping is entirely electronic nature, and can be observed even at low decibel levels. If you turn down the master volume on your amp to bedroom level and crank the amp's preamp (or an external preamp), you can hear the gritty, distorted sound of the power amp's input circuit clipping. Some people like this effect (especially with a tube amp... with most ss amps it's pretty nasty)... but nobody likes the sound of a speaker farting, to my knowledge!
 
#12
Farting is partly an electrical phenomenon too, not just mechanical. Farting occurs when the voice coil exits the magnet gap, where it can no longer control the cone. This can occur before maximum mechanical excursion, so mechanical damage is not necessarily occurring when you hear farting.
 
#15
archtop2 said:
Bought a used Eminence Basslite S2012 and tried it connected to my brand new Mrkbass LM250.

Volume at 12 o'clock I get the speaker farting at 0:28 video below



Does it miss a cab or the speaker has a problem?
Click to expand...

It needs to be in a cab for anything other than low volume testing.

After 0:28 you can see the cone flapping about, not good. Get it in a suitable cab and then try it again.
 
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#18
archtop2 said:
Bought a used Eminence Basslite S2012 and tried it connected to my brand new Mrkbass LM250.

Volume at 12 o'clock I get the speaker farting at 0:28 video below



Does it miss a cab or the speaker has a problem?
Click to expand...


Even Eminence tests in a box:



Sometimes I don't think it's a good idea to sell raw drivers on the consumer market. No cabinet, or a badly designed cabinet can help destroy the driver and the manufacturers reputation. I, for one am glad the do, but there's some I'd like to get my hands on that the manufacturer will not sell direct to consumers maybe for this reason.
 
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#20
Gosh!
Never caught such information before, used to deal with guitar amp speakers I never had such phenomenon. Read a lot of amp design questions, I'm AX84 generation, guitar focused eh, not a newbie but I missed this.
For my cab design I'm in Eminence S2012 datasheet with 3 cab shape and didn't get this.
I hope other diyers will read this imperious warning about our bass speakers, an explicit warning from the manufacturers would be welcome also.
That's perhaps why I love this forum, thank you mates. :)
 

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