Enjoy the benefits of a premium membership!
Upgrade Account
-
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.
Does a backline bass rig cancel frequencies in the PA?
- Thread starter caballero59
- Start date
This is an interesting subject, no doubt, and is valid, but with my bit of pro audio system experience, being able to predict how and where problems like this will occur is a crapshoot at best. Cancellations like this happen, but not everywhere in a venue. Just certain areas where those signals meet.
With differing sub placements, bass amp placements and proximities to those subs, stage and room sizes, it's really difficult to predict a problem area (except with expensive prediction programs such as Ease) and then, what could one practically do about those problems, unless you have the option of moving speakers and/or some digital processing with the subs? And even then, the fix might cause other problems.
My advice, unless you are measuring PAs in auditoriums and arenas and dealing with crazy loud bass stage volumes, is to not worry about this situation too much. I'd worry about proper electricity, catering, stagehands, okay, not really, but you hopefully get the idea.
This is just one view from a pro audio guy that got kinda frustrated with the business and decided that it was much more fun to go back to playing bass....
(and I was right!)
My band is ampless, e-drums etc so virtually no sound from the stage. We will put a wedge or two facing away from us for a center fill to the audience. it may not be perfect but it takes care of exactly what you are talking about.
No. Frequency cancellation only happens when a wave encounters another wave that's exactly the same In frequency and amplitude but out of phase by 180°.
I think this is "the way of the future" and makes perfect sense.
Part of me will miss the cathartic feeling of standing in front of Motorhead, The Melvins or High on Fire and getting absolutely obliterated by their stage volume... but those days are behind me anyway for so many other reasons.
And yes, I am a proud owner of tinnitus.
JazznFunk
Supporting Member
Them more likely scenario is that the subs/house will drown out your amp due to backfill and other resonances - and a loud house volume - and render it useless - even if you keep your stage volume low. That's why I stopped using a rig on some stages. The situation is much improved if I can get my amp back behind me by several feet. If you're on top of your amp, you'll never hear it the way it's being heard out front, and you will turn it up to hear yourself better, causing FOH problems. More trouble than it was worth in many cases, on many stages.
Last edited:
D
If the amp overpower the PA then yes. There's a reason why FOH engineers get that evil look in their eyes when bands crank their amps too loud on stage. Keep your volume levels on stage under control and you will be fine. This is one of the reasons why Ampeg SVTs and 100w Marshall Plexis can be a poor choice when playing smaller venues. Of course these amps have volume controls but they won't really be at their best at low volumes and when bands have that kind of wattage available they tend to use it...
The answer is no.
FOH is about Sound Reinforcement. If you're causing issues with FOH, you're too loud.
And FOH will just pull you out of the PA and your sound disappears. Bass rigs are not meant to project or push that much air to the room. Your onstage amp is for your monitoring.
Also if your PA can't completely over power your bass rig, it's lacking.
Do the math, how much power is your amp?
FOH should be many times more powerful from actual power to number of speakers.
Ask FOH for their suggestions, since their ears are the ones that should know, and are hearing the whole room, and matter the most.
Good luck, communications are the best solution.
FOH is about Sound Reinforcement. If you're causing issues with FOH, you're too loud.
And FOH will just pull you out of the PA and your sound disappears. Bass rigs are not meant to project or push that much air to the room. Your onstage amp is for your monitoring.
Also if your PA can't completely over power your bass rig, it's lacking.
Do the math, how much power is your amp?
FOH should be many times more powerful from actual power to number of speakers.
Ask FOH for their suggestions, since their ears are the ones that should know, and are hearing the whole room, and matter the most.
Good luck, communications are the best solution.
Total cancellation, yes. But you get partial cancellation (volume is reduced but still audible) with different degrees of phase shift and different amplitudes. If the sources are 150° out of phase and one is a few dB louder than the other, you will hear the frequency but noticeably lower than other frequencies where the phase shift is smaller.
Your amp onstage should never be anywhere near loud enough to cause that issue. If it is, its not "just a monitor"
I'm having trouble with wrapping my head around the ampless approach. Doing the IEM's certainly makes sense in many ways, but I really love my amp. I'm all for keeping the stage volume down (tinnitus really does suck!!), but it took me a long time to get to where my sound quality, volume potential, and rig portability are all in a good place. I'm not in a hurry to abandon a "good thing".
Last weekend I went to a small place to see a 4-piece cover band and it turned out that these guys all used IEM's - very clean stage layout (no amps or wedges) and a nicely capable PA that included a pair of subs with mains on top. My band also plays at this same cozy joint and we use amps and wedge monitors on stage. I play without PA support for my sound, but we're trending toward trying to put everything through the PA (mostly to keep the levels of our guitars and lead singer balanced and under control).
I was at this show with my guitar pal from my band and we chatted these guys up after their first set. It apparently took them a long time (about a year I think) to eventually get to where they were comfortable with the IEM's and setting their own individual mixes using tablets. I know that it would take my band a loooong time to get to where we could use that sort of layout, but I was impressed with how their setup was nice and sparse. The bulk of their equipment was the drum kit and PA and not much else aside from instruments and mic stands.
The bass player had no effects and he just plugged his bass into a Tech 21 BDDI to send a signal to the mix. What was curious for me was that his sound coming through the PA was okay... but just okay. I don't know whether his tone sounded different for him in his own IEM's - maybe they tricked him out a little bit - but the bass could have used a little tweaking to sound a little less vague in the PA - perhaps a little less of the lows and a little more low mids (next time I'll say something if it still needs dialing in).
When I play that room with my amp, folks love my sound and that includes my band mates. Our rhythm guitarist and drummer very much want to hear me. I'm not blasting them with enormous volume, but my best sound is warm and full. Reducing my stage volume and running more of my sound through the PA might actually be counterproductive if my pals have trouble hearing me the way they want to. Sorting this out will take some time and effort...
Yes, if two signals are exactly 180 degrees out of phase and the same volume at the listening location, total cancelllation of that frequency does occur. That's not what is being discussed here.
Since basses don't output sine waves at a single frequency, comb filtering (as mentioned earlier) is what happens. Each harmonic of each note is a different frequency, so the amount of cancellation varies based on the note played, placement of the speakers, harmonic content, etc. Then add in the room resonances and it gets complicated very quickly.
With no stage wash, yes holes in the PA coverage become obvious. I think the answer is to change the PA layout. Move speakers closer together, point them more toward the center, use smaller fill speakers. Turning up the stage amps may fill the gap with sound but odds of it being good sound and mixing well with the PA as you move through the room are low.
Bass sound through a bass amp is often very different than bass sound through a PA and the sound in the IEM may be different than either. It takes some time and attention to figure out what will work. But having no stage wash gives complete control to the FOH tech to dial in a PA sound that is good. Well, aside from room acoustic issues.
This is an interesting subject, no doubt, and is valid, but with my bit of pro audio system experience, being able to predict how and where problems like this will occur is a crapshoot at best. Cancellations like this happen, but not everywhere in a venue. Just certain areas where those signals meet.
With differing sub placements, bass amp placements and proximities to those subs, stage and room sizes, it's really difficult to predict a problem area (except with expensive prediction programs such as Ease) and then, what could one practically do about those problems, unless you have the option of moving speakers and/or some digital processing with the subs? And even then, the fix might cause other problems.
My advice, unless you are measuring PAs in auditoriums and arenas and dealing with crazy loud bass stage volumes, is to not worry about this situation too much. I'd worry about proper electricity, catering, stagehands, okay, not really, but you hopefully get the idea.
This is just one view from a pro audio guy that got kinda frustrated with the business and decided that it was much more fun to go back to playing bass....
I agree you shouldn't worry about it too much. But it should not be disregarded IMHO. If you will play for pay, the priority should be to give the audience the best possible experience. Often that means the bass player can't turn up as much as he/she wants.
That's not how it works.
The cancellation increases as the phase angle between the two signals approaches 180 degrees. Likewise mutual summing increases as the phase angle approaches 0 degrees.
Cancellation and summing is reduced when the signal levels are not equal, but they do not stop completely.
I have an anecdote and a question for @Wasnex and anyone else with experience to answer.
There's a live music room in Denver that makes a great exhibit for this discussion. The place is called Herb's Bar; the room is deep and narrow like a lot of bars are in older buildings. This one may be narrower than most, I bet 20 feet wide.
The stage is in the back and it fires crossways across the narrow dimension, and the opposing wall has floor to ceiling mirrors. There is a house PA in there and the whole situation gets painfully loud. Miserable acoustics.
My anecdote is that I've played in that room in all sorts of situations, ranging from one with a guitarist who had a Vox tube amp and needed to crank it to ear-splitting levels to get "his tone" - all the way to an all-IEM, no stage volume approach.
For sure, the IEM approach is a revelation in that room. I leave the gigs without my head spinning and clearly it sounds better to the audience in there. In fact my comparison experience between IEM and stage volume in that particular room is what won me over to IEMs overall.
My question - several times when I've played that room with amps, I'm sure I've noticed a certain distortion of pitch in the room. There have been nights where I or one of the other guys have sounded just a little out of tune in there, despite objective proof to the contrary.
In excessive stage volume + FOH situations where the acoustics are especially compromising, it is possible to experience some pitch movement in a room?
There's a live music room in Denver that makes a great exhibit for this discussion. The place is called Herb's Bar; the room is deep and narrow like a lot of bars are in older buildings. This one may be narrower than most, I bet 20 feet wide.
The stage is in the back and it fires crossways across the narrow dimension, and the opposing wall has floor to ceiling mirrors. There is a house PA in there and the whole situation gets painfully loud. Miserable acoustics.
My anecdote is that I've played in that room in all sorts of situations, ranging from one with a guitarist who had a Vox tube amp and needed to crank it to ear-splitting levels to get "his tone" - all the way to an all-IEM, no stage volume approach.
For sure, the IEM approach is a revelation in that room. I leave the gigs without my head spinning and clearly it sounds better to the audience in there. In fact my comparison experience between IEM and stage volume in that particular room is what won me over to IEMs overall.
My question - several times when I've played that room with amps, I'm sure I've noticed a certain distortion of pitch in the room. There have been nights where I or one of the other guys have sounded just a little out of tune in there, despite objective proof to the contrary.
In excessive stage volume + FOH situations where the acoustics are especially compromising, it is possible to experience some pitch movement in a room?
Last edited:
