Sub at back of stage ......... feedback???

[Pirellithecat]

Hi, 
Tricky stage on Saturday next, but there is space at the back, to the side of the Drums, for the Sub ......... but it might be a risky experiment as I have used it "out front" previously but this involves convoluted wiring and reduced space for the "performers". 

So ... convenient, but am I going to run the risk of feedback via Drum mics and Drum Vocals/monitor?   The vocal mics should be OK as they are High Pass Filtered at above the sub frequency (or thereabouts).   Basically only the Drums go through the Sub (maybe a bit of bass should the need arise.) And yep, I know bass is omnidirectional, so it doesn't theoretically matter but I guarantee the drummer will hear more kick drum via the sub if he's sitting next to it (as will I!).  So i guess his mics will too ....... 

If anyone has practical experience of doing this and would like to share that would be really helpful.    
Cheers. 

[Bill Fitzmaurice]

Subs at the back of the stage won't feed back any worse than at the front as the output of subs is omnidirectional. Placing subs at the front, and for that matter more than a half meter from the wall, costs output and low frequency extension, so that should be avoided anyway. What matters in this case is the distance from the subs to the mics. But since subs cannot be directionally localized you can move them well over to one side or the other and the audience will never know the difference.

[Pirellithecat]

Will just need to persuade he guitarist that it's not too risky/complicated/tempting fate.   That's Rock and Roll for you!😅

[Chienmortbb]

The absolute worst placement for subs is either side of the stage under the tops. You should be OK at the rear of the stage.

[Phil Starr]

You've pretty much worked it out. You'll soon hear bass feedback though, it isn't subtle and I'd treat the kick mic with some respect and maybe start with it a touch lower than usual. Not because it is behind as Bill has already said but because it might be closer to the mics.

 

If you're using just one sub I quite like mine under one of the tops. It's makes at least one of the tops more audience proof. One tip is to put a cardboard pyramid on top of tha sub, it stops people putting their drinks on it

 

 

[Al Krow]

We had a really boomy first half of a gig with the sub at back of the stage adjacent to the drum kit. Concluded must have been getting getting more bleed into the kick drum mics. 

Edited February 23 by Al Krow

[Phil Starr]

1 hour ago, Al Krow said:

We had a really boomy first half of a gig with the sub at back of the stage adjacent to the drum kit. Concluded must have been getting getting more bleed into the kick drum mics. 

That could have just been boundary reinforcement. Placing a sub back against a wall means the sound is all going forwards reinforcing the sound levels, in fact all the surrounding surfaces will have the same effect so if it is in a corner you have the side wall floor and rear wall all reflecting and increasing the sound levels from the sub. You need to turn the sub right down in this situation. Of course it would also be closer to the drummer (obvs) and to you if you were standing next to them.

Edited February 23 by Phil Starr

[Bill Fitzmaurice]

37 minutes ago, Phil Starr said:

That could have just been boundary reinforcement. Placing a sub back against a wall means the sound is all going forwards reinforcing the sound levels.

+1. Against the wall is the equivalent of doubling the sub count, in a corner the equivalent of quadrupling it, compared to well out. It also eliminates boundary cancellations that occur when not tight to a wall or corner. But 'adjacent to the drum kit' is a no go. Not only will you have low frequency feedback into the drum mics but you'll also have acoustical coupling of the sub and drums that creates another feedback loop.

[warwickhunt]

13 minutes ago, Bill Fitzmaurice said:

+1. Against the wall is the equivalent of doubling the sub count, in a corner the equivalent of quadrupling it, compared to well out. It also eliminates boundary cancellations that occur when not tight to a wall or corner. But 'adjacent to the drum kit' is a no go. Not only will you have low frequency feedback into the drum mics but you'll also have acoustical coupling of the sub and drums that creates another feedback loop.

 

How close is adjacent?  We sometimes have to set up in fairly tight spaces (inc long skinny rooms) and I've only just convinced our PA owner/operator/guitarist, to move the sub(s) from directly under the FOH main speakers... just to the rear and side of the drummer is sometimes the only position available that is near a rear wall or corner.  

[Bill Fitzmaurice]

If it's too close you'll know, by the feedback.  Max Weinberg and his band were in town a while back, he had a sub set up maybe six feet to one side. When he played there was a constant droning feedback that drowned out the entire band. I mentioned it to the guy in the booth, he was too busy playing games on his phone to care. That's when I left.

Edited February 23 by Bill Fitzmaurice

[Phil Starr]

14 hours ago, warwickhunt said:

 

How close is adjacent?  We sometimes have to set up in fairly tight spaces (inc long skinny rooms) and I've only just convinced our PA owner/operator/guitarist, to move the sub(s) from directly under the FOH main speakers... just to the rear and side of the drummer is sometimes the only position available that is near a rear wall or corner.  

As Bill has said close to the drummer is a complete no-no. Close to the wall is not a major issue but you have to realise you've effectively added an 'extra' sub and turn down. Your ears should be your guide but expecting the problem means you start up expecting more bass in this situation. It can be a positive too. If you think your sub won't be enough for a big venue pushing it into a corner or against the wall gives you a free boost.

 

In the end Sub placement has to be a bit of a compromise for a gigging band doing their own PA. If you are gigging a regular venue or settint up a permanent installation you'd do better but with an hour to set up there have to be compromises and no sub or accepting lower bass levels from it is sometimes the answer.

 

 

Long narrow rooms are always tricky and a bane of the UK's often ancient pubs. Down in the West Country skittle alleys are widespread and frequently the place they put the band. The close side walls and ceilings are frequently too close and for the bass wavelenght dimensions so you have lots of resonances, multiple pathways and phase cancelling. I usually end up with an HPF filtering out a lot of the lower frequencies as the best way of dealing with this.

[warwickhunt]

Cheers @Bill Fitzmaurice & @Phil Starr.  I've been doing onstage mixing for small/medium venues for 40 years and I know a lot of the nuances of a fair few venues (shared dimensions).  I've rarely used bass bins in the past but then again I generally ran my bass through backline and in 50% of venues didn't use it through the PA; more frequently I'm going ampless and 100% through PA (to monitor or IEM), with a bass bin (or 2) being supplied by another band member.  For the last year I've tried to convince the band that 2 bass bins directly under the tops (15" RCF) isn't the best place but I'm battling 3 other opinions with all of their ingrained habits and it isn't easy.  The worst situations are the 300-400 seater 'clubs' where subs with poles and tops are placed 7-10m apart at the front of the stage area.  I'm trying to show that placing them together off to one side near a wall will improve matters but I don't want to scupper my best informed ideas by making things worse, hence the question re. how close is too close! 

  

[Pirellithecat]

15 hours ago, Bill Fitzmaurice said:

+1. Against the wall is the equivalent of doubling the sub count, in a corner the equivalent of quadrupling it, compared to well out. It also eliminates boundary cancellations that occur when not tight to a wall or corner. But 'adjacent to the drum kit' is a no go. Not only will you have low frequency feedback into the drum mics but you'll also have acoustical coupling of the sub and drums that creates another feedback loop.

Phew!   The available location would have been adjacent to the Drummer, in the rear corner - primarily resulting in grief for the sound-man and bass player (me!).   So THANK YOU!!! 
I shall revert to Plan A.  or maybe make a carboard cone and sit the sub adjacent to the front of the stage, beside the wall.    

[Bill Fitzmaurice]

2 hours ago, warwickhunt said:

  For the last year I've tried to convince the band that 2 bass bins directly under the tops (15" RCF) isn't the best place but I'm battling 3 other opinions with all of their ingrained habits and it isn't easy.  

  

Ask them what the speed of sound is. Every acoustical engineer, pro or amateur, knows that number as well as they know their own name, as it's the prime factor in calculating wavelengths. If they don't know that number and don't know what the importance of wavelengths is they don't get to offer an opinion. They may have one, but they should keep it to themselves.

 

 

[warwickhunt]

8 minutes ago, Bill Fitzmaurice said:

Ask them what the speed of sound is. Every acoustical engineer, pro or amateur, knows that number as well as they know their own name, as it's the prime factor in calculating wavelengths. If they don't know that number and don't know what the importance of wavelengths is they don't get to offer an opinion. They may have one, but they should keep it to themselves.

 

 

 

Indeed but it is essentially 3 other musicians who are preprogramed to think that the only place for bass bins is in 'that' wrong place!    

[Dan Dare]

 

3 hours ago, warwickhunt said:

For the last year I've tried to convince the band that 2 bass bins directly under the tops (15" RCF) isn't the best place but I'm battling 3 other opinions with all of their ingrained habits and it isn't easy.

 

Very true and Bill's right. Manufacturers don't help by installing those tempting threaded mounts in the tops of subs so you can mount top boxes on them easily. More often than not, I use only one sub. I'll usually reduce sub level by 2-3db, too. Two is usually overkill in moderate sized venues.

Edited February 24 by Dan Dare

[Bill Fitzmaurice]

1 hour ago, warwickhunt said:

 

Indeed but it is essentially 3 other musicians who are preprogramed to think that the only place for bass bins is in 'that' wrong place!    

There are only two reasons for them thinking that. One is 'That's how everyone does it'. The other is 'It's the only way we know how to do it'. Neither is a valid reason to keep doing it. That's why one person should be in charge of PA, that being the person who is the most knowledgeable.

[TheRev]

On 24/02/2024 at 10:03, Phil Starr said:

 

Long narrow rooms are always tricky and a bane of the UK's often ancient pubs. Down in the West Country skittle alleys are widespread and frequently the place they put the band. The close side walls and ceilings are frequently too close and for the bass wavelenght dimensions so you have lots of resonances, multiple pathways and phase cancelling. I usually end up with an HPF filtering out a lot of the lower frequencies as the best way of dealing with this.

Ugh. Skittle alleys...

There's a pub in Dorchester that I dread playing or doing sound in their skittle alley- low frequencies are mush, high frequencies are cacophonous. 

 

Edited February 25 by TheRev

[Phil Starr]

19 hours ago, TheRev said:

Ugh. Skittle alleys...

There's a pub in Dorchester that I dread playing or doing sound in their skittle alley- low frequencies are mush, high frequencies are cacophonous. 

 

And the added hazard that the acoustics change throughout the evening as the room fills and people stand up to dance. Do you use the upright? That's gotta be even more difficult in a skittle alley.

[mep]

On 24/02/2024 at 10:22, warwickhunt said:

Cheers @Bill Fitzmaurice & @Phil Starr.  I'm trying to show that placing them together off to one side near a wall will improve matters but I don't want to scupper my best informed ideas by making things worse

  

Years ago in a tribute band we had a Peavey PA with 2 x subs & tops. A sound guy we used suggested placing the subs together and yes it does work.

[Pirellithecat]

Thanks everyone - disaster averted!! Thanks for the advice.!  
Sub out of corner and away from drum mics -  so front edge of stage to the right against wall  - and a great gig was had by all.    Still need to work on a way to get the drum vocals working without feedback from monitor and bleed/feedback from kick drum/Snare Mics.  SM57 on Snare (rim) - wonder whether an overhead might work better ???? But kick drum .... no clue!  Current solution is to turn off drummers vocal mic!! 
Hey Ho - upwards and onwards! 

[Bill Fitzmaurice]

They key to minimizing feedback from drum mics is to place them as close as possible, ideally with rim mounts. Of course that means using more of them. Overheads are for picking up cymbals.

[Chienmortbb]

On 25/02/2024 at 11:57, TheRev said:

There's a pub in Dorchester that I dread playing or doing sound in their skittle alley- low frequencies are mush, high frequencies are cacophonous. 

There is live music in Dorchester

[Phil Starr]

If turning off the vocal mic cures the feedback problem then that’s what is giving you the problem. Unsurprisingly as his voice is a lot quieter than the drums so that mic will have more gain. 
 

If you have a digital desk then you should apply a gate to his vocal mic. It switches the mic off when he isn’t using it. Find out what pattern of mic he is using. If it’s a cardioid like the SM57 then the dead spot for the mic is at the back end which should be pointed at the monitor. If it’s a super cardioid then the dead spot is at the side. Your drummer needs to get as close to the mic as possible to get his volume up so the gain can be reduced ie he needs to ‘eat the mic’.

 

 

[warwickhunt]

3 minutes ago, Phil Starr said:

If turning off the vocal mic cures the feedback problem then that’s what is giving you the problem. Unsurprisingly as his voice is a lot quieter than the drums so that mic will have more gain. 
 

If you have a digital desk then you should apply a gate to his vocal mic. It switches the mic off when he isn’t using it. Find out what pattern of mic he is using. If it’s a cardioid like the SM57 then the dead spot for the mic is at the back end which should be pointed at the monitor. If it’s a super cardioid then the dead spot is at the side. Your drummer needs to get as close to the mic as possible to get his volume up so the gain can be reduced ie he needs to ‘eat the mic’.

 

 

Could he use one of those sensor optogate type devices that turns off the mic unless he is in range of the sensor?