Why NOT run bass through PA?

[cgrissom]

As is usually the case, there is some truth in what your band buddies are saying. Running your bass through the mains can cause the frequency range that the vocals and guitar operate in to be muddy or drop all together. However, this isn't caused by the amplitude of the frequency as they suggest. It is a power issue. If the amp powering the mains doesn't have the headroom to handle the power demands of the low frequencies when demanded the sacrifice is in the mid and high frequencies.

As a FOH engineer for 15+ years, the solution depends on the venue and equipment. I always run the bass through the FOH but how varies. In small to medium venues, I use full range speakers with lots of headroom on the amp and the bass amp provides the majority of the sound with the lows rolled out of the mains. In large venues or outside, I run subs that are amped seperately from the mains with the full range of the bass coming through the FOH system. In all cases, you have got to have enough power delivered correctly. Tell your band to get more juice!

[tony89merc]

thanks guys.....just reading the post anwsered ALL my ?.....peace brothers and sisters

[CrewsControl]

Originally Posted by fokof

That's a funny concept ; the speed of sound is slower for bass frequencies !!!!!
That's good one , should be "humour & joke" thread.

It's possible that the electrical path for low frequency signals is a different length than the path for high frequencies, due to crossovers and other signal processors in the signal path. This can result in the fundamentals coming out of the speaker in a unfavorable phase relationship to the harmonics.

"Low frequencies travel slower" is the layman's way of describing this phenomenon. Sonic enhancers or exciters are supposed to correct for it.

[TimmyP]

Originally Posted by CrewsControl

It's possible that the electrical path for low frequency signals is a different length than the path for high frequencies, due to crossovers and other signal processors in the signal path. This can result in the fundamentals coming out of the speaker in a unfavorable phase relationship to the harmonics.

"Low frequencies travel slower" is the layman's way of describing this phenomenon. Sonic enhancers or exciters are supposed to correct for it.

Pretty close! Look up "group delay'.

[ggunn]

Originally Posted by CrewsControl

It's possible that the electrical path for low frequency signals is a different length than the path for high frequencies, due to crossovers and other signal processors in the signal path. This can result in the fundamentals coming out of the speaker in a unfavorable phase relationship to the harmonics.

"Low frequencies travel slower" is the layman's way of describing this phenomenon. Sonic enhancers or exciters are supposed to correct for it.

I don't think so. Electrical impulses travel at virtually the speed of light; I cannot see any way that electrical path length differential is going to make an audible difference. However, many gain stages cause a signal polarity inversion between input and output*, so the number of gain stages the bass sound goes through in reaching the bass cab speakers vs. the number it goes through on the way to the mains could cause the sound from the mains to be polarity reversed ("out of phase") from the sound from the bass cab, in which case they could be in disagreement.

Upon further review... Crossovers produce phase shifting on the steep slopes near crossover points, which is sort of a frequency dependent delay effect; perhaps that is what you are thinking of.

*An illustration is the vibrato/reverb and normal channels on many Fender amps. The vibrato channel preamp has one more inverting gain stage than the normal channel one. If you "Y" into both inputs and turn them both up, the volume will be significantly less than either channel alone because of cancellation effects between the two preamps at the input of the power section.

[testing1two]

I think the OP's bandmates know there's something wrong with the FOH & Monitor mixes and it's related to the bass. Their explanation is obviously incorrect and I'm guessing their PA system is not very elaborate either.

One one hand, bass can be run through any PA system as long as you're willing to accept the system's limitations when you mix. For smaller systems that means rolling off much of the low end and being careful not to compete for the same sonic space as the vocals. But that's the responsibility of the engineer, not the bass player.

On the other hand, if the PA has limited low-end response and no one is capable of mixing the bass properly then it's probably better to take responsibility for your own low-end via your bass rig.

[LegoBass]

I don't know about anyone else, but I don't run through the board for several reasons. All of my bands gigs, I use my SVT-4 Pro and some arrangement of my three speaker cabinets to get the volume that I need. My band has our own PA that we take everywhere, so I know it well.
Reason 1. The band leader mixes sound before and between sets. The mix sounds great, but everything is over EQed, an extreme Smiley Face, the opposite of my tone.
Reason 2. I hate the sound of using a DI box and letting the PA amps do the work. I feel with this the sound in my head never ever comes out.
Reason 3. Effects. I like my effects, and running them through our house speakers just mudd-ifies everything. Running everything through my amp and speaker cabinets keeps everything cleaner and richer.


I also think I agree with the OP's friends a little bit about low frequencies moving slower. It is not the actual frequencies, as it is the speaker. A speaker creating frequencies around 50Hz and 4kHz causes a lot of strain. It has to move at two different speeds to create those frequencies. This is why a fEARful setup with a crossover is so widely used, it lets separate speakers share the work and not have to create such a wide spectrum of sound.

[Ric5]

Originally Posted by Buck Snelson

Their argument is something as follows: the bass going through the PA muddies up and kills the sound of the guitars and vocals in the house system because the bass frequencies are "slow" compared to the others and the PA speakers "can't keep up". They say the only time the bass should be run through the PA is if there is a dedicated sub in the PA system, with an appropriate crossover to keep the bass out of the mains and monitors. Is any of this true?

The best bet is to run everything through the pa. That being said you need a pa that can handle all of that. You need some big subs, big mains, and a power amp with lots of watts.

But if you only gig a few times per year then maybe a bigger bass amp is in order. Perhaps a 350 amp with a 4x10.

[lowfreq33]

There are some small rooms that I won't bother going into the PA, but there's a point at which my stage volume would overwhelm the rest of the band.

[spaz21387]

I would say well if you are willing to buy me the 8x10 and ampeg svt to power it Id gladly do that, but since you wont lets keep running it through the pa.

[JimiLL]

everything else aside... if the pa doesnt have subs... its not too bass guitar friendly

[ggunn]

Originally Posted by spaz21387

I would say well if you are willing to buy me the 8x10 and ampeg svt to power it Id gladly do that, but since you wont lets keep running it through the pa.

I, for one, wish I could always run my bass through the PA with someone out front mixing, but for most gigs I am not through the PA. Consequently, it is pretty hard to set my volume. With different rooms, different stages, outside sometimes, my correct stage volume relative to everything else is different, and from standing next to my rig I just don't know. All I can do is play at a good volume relative to the drums and hope for the best. I don't really know until I listen to the recording later (I record everything with mics out by the sound board), and of course by then it's too late. I love it when I'm in the PA with a good FOH guy running it and don't have to worry about it.