As good a time as any...

F

frank kayser

Junior
Jan 11, 2011
292
1
18
Maryland suburbs of DC
Good morning - welcome to a new day, and a new board!



I've searched all the posts here on SoundForumns.net and have not found an appropriate answer...
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Seriously...



I am looking for practices - in a SOS (one per each side of stage), at what point of ''misalignment to square'' do you start to delay the most forward speaker? 2', 4', 8'...



Would one use the same decision process whether one was running in mono or stereo?



Does that type of misalignment cause smearing/combing/ more with higher frequencies or lower - I'm guessing that width between the speakers and distance out of alignment would have an effect - and any combing would be frequency dependent as far as where one would find it.



thanks

frank
 
Re: As good a time as any...

Frank,



I am not really sure what delay you are referring to. I tend to think of three types of delay. The first type of delay is to match the various parts of a speaker system to each other. For a SOS show this only applies if you have separate subs. The second type of delay is if you have a system that has a delay ring (speakers further out in the crowd to extend the sound field). The third type of delay is to delay the entire FOH system to the backline.



In practice, when my SOS speakers are mounted on the subs, I have a precalcualted delay to aligh the subs and tops. If I have an extremely loud backline (which is rare in my current jobs) I could delay the entire FOH system to the backline which can help clean up the mud.



Satellite speakers can be problematic because the question becomes for what position do you delay them? In theory, the delay is the difference in distance between the FOH speakers to the listening position and the satellite speaker to the listening postion. Unfortunately, in a large area these distances can be different. What you end up with is some sort of average or ''can I make it better somewhere without making it totally suck elsewhere''. You also start to run into the same problems when the subs are not physically located with the tops.



I think a more basic place to start with a SOS rig is whether you want true stereo (all listening positions covered by two separated sources), pseudo stereo (some positions especially in the middle covered by two sources but fairly large areas only covered by one source), or dual mono (each listening position covered by one source even though you set up two sides because people expect to see that).



Personally, I tend to dual mono, and even in a narrow room prefer a single source. However, people seem to freak out if you don't set up speakers on both sides. There have actually been rooms where I set up both sides and never turned one on.
 
Re: As good a time as any...

I don't know what you mean my ''misalignment to square''.



Maybe you cold better explain.



Combfiltering happens-no way around that. The basic definition is two identical signals arriving at the same place at different times.



It is that time interval that determines what freq the combfiltering will start at.



I say start-because there is a freq at which it starts and goes higher in freq from there.



Here is a link that might help explain



http://www.dbasi.com/files/resource/loudspeaker_placement_rev041021.pdf
 
Re: As good a time as any...

frank kayser wrote on Tue said:
I'm guessing that width between the speakers and distance out of alignment would have an effect - and any combing would be frequency dependent as far as where one would find it.
Click to expand...



Correct! Adding delay to one of the speakers will just modify/compound the issue.



With that said, if for some reason one SOS is closer to me than another, I have added some compensation delay to that speaker to help adjust the image. I usually only do this if there is some flavor of interference where I'm positioned at FOH. Since the audience is located at various distances between the two speakers, the affect will/could be different for almost every audience member. Live sound is usually about finding the best compromises to get the job done well (and sometimes that's just a matter of making sure that I'm happy).
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Jeff
 
Re: As good a time as any...

I have done this in a bar where FoH is in a nasty spot with respect to bass coverage. I found it an educational thing to try, but as I was simply moving ''good'' and ''bad'' around the room instead of making the whole room any better, I decided it was not worth the effort for those gigs.
 
Re: As good a time as any...

Ivan Beaver wrote on Tue said:
I don't know what you mean my ''misalignment to square''.



Maybe you cold better explain.



Combfiltering happens-no way around that. The basic definition is two identical signals arriving at the same place at different times.



It is that time interval that determines what freq the combfiltering will start at.



I say start-because there is a freq at which it starts and goes higher in freq from there.



Here is a link that might help explain



http://www.dbasi.com/files/resource/loudspeaker_placement_rev041021.pdf
Click to expand...



I agree, Ivan - lousy problem explanation. Let me try again, with an example of a local club I hang at occasionally.



Setup:

Room: 20' wide, very deep.

Stage: 20' wide, nearly 20' deep. About 8'' off floor, 10-12' acoustic tile ceiling

Door opening (stage right) cuts a triangle off front of stage of about 8' at 45 degree angle.

Speakers: Yamaha Club, 2xSW118V subs, 2xS215V tops, 2xSM15V Monitors



Stage left speakers are stacked on front of stage.

Stage right speakers are also stacked on front of stage, but 8' behind due to the doorway.

Monitors are in front of the stage right speaker stack.

Lead performers for the most part are 3' from front of stage, behind stage left stack, and in front of stage right stack.

Front line / drums are behind both speaker stacks.



I honestly do not know if they are running dual mono, true stereo, or pseudo-stereo.



So the line across the front of the speaker cabs is not perpendicular to the side wall, nor parallel with the back wall.



The sound is never clean nor consistent - room shape acoustics, the fact FOH is unmanned for much of the time I'm sure are factors. I believe the speaker placement is also a problem. So my question is basically the fact the stage right speaker is 8' behind the stage left speaker. Would it be of any use to delay the stage left stack? I'd also like to try centering the subs...



Ivan - I hope this gives you a bit more meat for you to chew on...



Jay - your idea of a ''show-only'' unused stack gives me the idea to unplug the stage right stack, running with just the stage left - ah, but it is neither my gig or my rig.



thanks

frank



 
Re: As good a time as any...

It sounds like the stage right are in the rear, that means the stage left would have to be delayed by the difference between them. 8 feet for both the sub and the top would be a good start.



It sounds like both stacks cover the whole room, so the difference between them could be a potential problem.



If you would like to tell me in private where, odds are at some point I could stop in and give you my opinion (for all that is really worth).
 
Re: As good a time as any...

I don't think the physical placement and delaying them would help. Maybe for localization (pulled to the sound that arrives at your location first), but not for sound quality.



I would think that lies in the overall system alignment but not having a soundguy doesn't help any. Of course having a bad soundguy doens't help any.
 
Re: As good a time as any...

Ivan,



I was thinking that folks mid room that were hearing both speakers would be experiencing some type of ''echo'' effect as in stage left would hit their ears, and then some milliseconds later, stage right would arrive. I would think it would take any crispness out of the sound - smeared - the same way reverb takes the edge off a sound.



Personally, I don't leave the desk during a set, as I'm always trying to improve what's coming out. I suspect you and many others are tied to the desk, as well. I do not want to label anyone a ''bad sound guy'' for merely leaving the desk at times. Of course, it is really hard to adjust and optimize when the controls are out of reach.



frank



 
Re: As good a time as any...

Frank, I don't like to see a board on autopilot for much of the night as you mentioned, but it is hard to walk the room and stay behind the wheel. You have to walk the room sometime.
 
Re: As good a time as any...

Stuart Pendleton wrote on Tue said:
Frank, I don't like to see a board on autopilot for much of the night as you mentioned, but it is hard to walk the room and stay behind the wheel. You have to walk the room sometime.
Click to expand...

Precisely, Stuart. While the absence was worth noting, I do not wish to be too quick to judge, or imply there is no reason to leave the controls.

 
Re: As good a time as any...

frank kayser wrote on Tue said:
Personally, I don't leave the desk during a set, as I'm always trying to improve what's coming out.
Click to expand...

If I am happy with the FoH position, I might also stay at the desk the whole time the band is playing. On the other hand, if FoH is not in the best spot and most of the audience is getting a different sound than me, I make it a point to walk the room a lot to make sure I'm mixing for the audience, not for me.



Even if FoH is in a good place, in bar settings, I make it a point to walk around a bit after the first song in each set, as I notice my muso's make the most dramatic adjustments to their stage volume between the first and second song of every set.
 
Re: As good a time as any...

frank kayser wrote on Tue said:
Ivan,



I was thinking that folks mid room that were hearing both speakers would be experiencing some type of ''echo'' effect as in stage left would hit their ears, and then some milliseconds later, stage right would arrive. I would think it would take any crispness out of the sound - smeared - the same way reverb takes the edge off a sound.



Personally, I don't leave the desk during a set, as I'm always trying to improve what's coming out. I suspect you and many others are tied to the desk, as well. I do not want to label anyone a ''bad sound guy'' for merely leaving the desk at times. Of course, it is really hard to adjust and optimize when the controls are out of reach.



frank
Click to expand...

It is not just a matter of time-but also level. Maximum combfiltering is when both signals are the same level. With one being closer-the level would be higher.



Also the ear perceives different time arrivals as different things. 8ms or so is not long enough to be considered ''echo''. It is more a time smear-as you say.



However there are also other things that add to the smear effect-other reflections in the room and so forth.



Acoustics can be a very complicated set of parameters and you have to look at all the factors involved, not just a single parameter-such as loudspeaker distance.
 
Re: As good a time as any...

To throw a little more wood on the Fire at what point would the Haas effect come into play if say you are closer in proximity to the stack that's further back?



Would one not have to power shade to keep both boxes aligned and again would that not only account for 1 listening position?
 
Re: As good a time as any...

Ron Kreiger wrote on Tue said:
To throw a little more wood on the Fire at what point would the Haas effect come into play if say you are closer in proximity to the stack that's further back?



Would one not have to power shade to keep both boxes aligned and again would that not only account for 1 listening position?
Click to expand...

It is easy to get a single listening position correct. But getting it right for multiple positions is a lot harder.



So you have to choose a position and live with it, or do some sort of average around the room.



The Haas effect simply says that you will localize to the sound that arrives at your ears first, unless the secondary sound is 10dB louder than the earlier sound.



Now how you would compensate for this is a highly debated topic, and in my opinion it varies from room to room and situation to situation.



Sometimes I add additional delay-sometimes I don't and sometimes I even cut the delay time DOWN-because the overall effect in the room is better for it. It depends on the situation and the particular problems/issues with that particular job.



Sometimes you have to make one thing worse-to make another thing much better.
 
Re: As good a time as any...

A lot of good insight - As much as I thought I knew, I was sure that stacks being that far out of line would absolutely require some type of time alignment between the stacks. I should have been suspect of my use of absolutely. As pointed out, there is nothing absolute about this situation. Proved yet again, ''A little knowledge is a dangerous thing''.



The good news is that I did get my original question answered - and a lot to chew on, to boot. My controllable situations are fine.



I would, however, like a crack at my example setup to try a number of things - single-stack, centered subs, but only after I've had a shot at the board - the entire ''problem'' may be there - though I'd rather look into and rule out setup and equipment problems before I ''badmouth'' another operator - especially when I don't know whether I could do as well in that situation. - I'd sure like a shot, though...



And finally, Jeff and Stewart's point that one does need to leave the console to accurately gauge one's work is well taken - and practiced, honestly. MBWA (management by walking around) Maybe I should do more.



Thanks

frank
 
Re: As good a time as any...

Consider that at some positions in the room you WILL be equal distance between the different loudspeakers. So those spots will be correct as far as time arrivals. and the other spots will be ''wrong''.



OF course if you go to the ''wrong'' spots and make them ''right'' then the previous ''right'' spots will now be ''wrong''
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You can't win.
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This is one of the overwhelming reasons for a center cluster.



But in many rooms that is simply not possible, and people often think of a ''mono'' cluster as not being ''cool'', but what they think of ''cool'' doesn't work well and has all kinds of problems.
 
Re: As good a time as any...

Ivan Beaver wrote on Wed said:
Consider that at some positions in the room you WILL be equal distance between the different loudspeakers. So those spots will be correct as far as time arrivals. and the other spots will be ''wrong''.
Click to expand...



If I am picturing this room correctly, the problem I am now seeing is that many of the seats, especially right in front of the stage, will be closer to but extremely off axis to the nearer stack.
 
Re: As good a time as any...

Jay Barracato wrote on Wed said:
Ivan Beaver wrote on Wed said:
Consider that at some positions in the room you WILL be equal distance between the different loudspeakers. So those spots will be correct as far as time arrivals. and the other spots will be ''wrong''.
Click to expand...



If I am picturing this room correctly, the problem I am now seeing is that many of the seats, especially right in front of the stage, will be closer to but extremely off axis to the nearer stack.
Click to expand...



The way I picture it (this is where drawings REALLY help) is that you are correct. Descriptions can often be ''seen'' as being very different than reality.



HOWEVER I ''picture'' it as most of the people are off to the side of the stage-so they would be more equidistance from both loudspeakers-but I could be wrong.



So what is more ''right'' the people in front of the stage or where most of the people are?
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Decisions-decisions
 


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