Getting some "farting"

[Jazzman23]

Hey all,

I have a Hartke HA3500 350 watt amp. I also have an Ampeg 2x10 250 watt cab at 8ohms. Last night me and my band played in my house for a few people, and I had my amp turned up to about 7 out of 10 volume, but I had a little compression on, and the preamps were turned down to about 3 and 4 each. EQ settings were all around the middle.

At times, i was getting a lot of overload, or "farting", whatever you want to call it. Why is this? Shouldnt I be able to keep up with a hard rock band with this kind of equipment without sacrificing my tone?

What if I added an Ampeg 1x15 250 watt cab to the mix? Am I correct in thinking that this would drop both 8ohm cabs down to 4ohms, which would be louder? 4ohms is louder than 8ohms, right?

Thanks for any help.

 

[BassIan]

Hey all,

I have a Hartke HA3500 350 watt amp. I also have an Ampeg 2x10 250 watt cab at 8ohms. Last night me and my band played in my house for a few people, and I had my amp turned up to about 7 out of 10 volume, but I had a little compression on, and the preamps were turned down to about 3 and 4 each. EQ settings were all around the middle.

At times, i was getting a lot of overload, or "farting", whatever you want to call it. Why is this? Shouldnt I be able to keep up with a hard rock band with this kind of equipment without sacrificing my tone?

What if I added an Ampeg 1x15 250 watt cab to the mix? Am I correct in thinking that this would drop both 8ohm cabs down to 4ohms, which would be louder? 4ohms is louder than 8ohms, right?

Thanks for any help.

IT sounds likely that you were reaching the limits of the power you have on tap. That farting is distortion from either the power amp in your head, or your speakers. So, maybe you should be able to keep up with a hard rock band, but that depends on how loud you play. For most bassists, a 2x10 will not cut it for hard rock. I found a 4x10 with three times the amplifier power you have did not quite cut it either in my hard rock band. There are many changes you can make to your equalizer settings that will help you get more from your rig, but there's only so much you can do with a 2x10.

I'll warn you also that if you use your rig for extended periods of time while it's clipping as it was, you could damage your speakers.

Adding speakers will help, and yes two 8 ohm cabinets in parallel makes a 4 ohm load. Ohms are not a measure of how loud speakers are, however you will get a bit more power from your head by using it with a 4 ohm load rather than an 8 ohm load. The 350 watt rating for your amp is probably for a 4 ohm load, and your amplifier will produce less power into 8 ohms.

Adding a 1x15 or any other speakers will help your volume issue. Some TalkBass users have been getting 2x12s to go with 2x10s and that seems to work out well. Check out http://www.avatarspeakers.com for some well-priced cabinets that do the job well.

Hopefully this helps a bit.

 

[MacGroove]

In using the term 'farting', it means then that you're spkr cones are getting too much cone excurstion (movement) which is usually caused by underpowering your spkr's.
Play through them a watch to see how much the cones are moving, they should have some movement, but for farting, it'd be a lot of movement.

 

[AGCurry]

Adding more speakers is generally the best way to be louder. It doesn't have as much to do with power or impedance as it does physics - cone area.

I don't care how much power your amp makes, or how much power your speakers will tolerate; two 10" aren't gonna be loud enough for some applications.

 

[Bob Lee (QSC)]

In using the term 'farting', it means then that you're spkr cones are getting too much cone excurstion (movement) which is usually caused by underpowering your spkr's.
Play through them a watch to see how much the cones are moving, they should have some movement, but for farting, it'd be a lot of movement.

It's the other way around: too much power at too low a frequency causes overexcursion.

To the OP: do you use an active bass?

 

[MacGroove]

It's the other way around: too much power at too low a frequency causes overexcursion.

To the OP: do you use an active bass?

My bad then Bob.
Because about 14 yrs ago I had a 600 watt EV cab w/2-12's @ 4 ohms and plugged in a SWR SM400 amp rated @ 600 watts into 4 ohms and the spkr cones farted, way too much cone excursion. I plugged in my Crown MT1200 w/Alembic pre and no problem. I was told that the spkr's were being under driven.

 

[billfitzmaurice]

I was told that the spkr's were being under driven.

That's akin to a car going faster with the engine at 500 RPM than at 5,000 RPM. It can't happen. The excursion of the driver is directly proportional to the power driving it. Less power, less excursion.

But a 600 watt amp is easily capable of farting out a 600 watt speaker. The wattage rating of a driver has no bearing on how much power it will take before exceeding its excursion limits. For instance, EVM 12Ls in a typical bass reflex alignment will only take at best 80 watts below 100 Hz before reaching xmax. I'd imagine the difference in your scenario was related to the different EQs of the pre's, perhaps there was enough bass boost with the SWR to drive either the speakers or the power amp or both beyond their limits.

 

[Luke73]

My bad then Bob.
Because about 14 yrs ago I had a 600 watt EV cab w/2-12's @ 4 ohms and plugged in a SWR SM400 amp rated @ 600 watts into 4 ohms and the spkr cones farted, way too much cone excursion. I plugged in my Crown MT1200 w/Alembic pre and no problem. I was told that the spkr's were being under driven.

I think you might be a little confused here.

Underpowering a cab will never cause it to fart. It just can't happen.

What you may be referring to is using a head that is underpowered and as a result, driving it too hard and sending it into constant clipping, which of course will result in nasty noises.

That's not underpowering your cabs, it's using an underpowered head and clipping it.

The two scenarios are quite different.