# feedback! help



## AlexD (Jul 23, 2009)

I am doing a small production with my school, they have asked me to put in some sound reinforcement, and I have. I have used two C 1000s on ether side of the stage, at floor level touching the stage almost. The speakers at the moment are on ether side of the stage right next to the stage and the mics. When the next brake comes we are going to move the two speakers in front of the stage so the mics will be behind the speakers. I can't turn up the mics enough to pick up the sound before the feedback comes. I have set the eq's on the mixer to very low bass and high treble. Will this sort out the feed back problem and is there anything else I can do to sort it out

I also have a Beta 57 in the middle of the stage to pick up some solo parts. We do have some wireless headsets but they are very bad... the model(s) we have are a pro8HE headset, ATW-T701 UHF transmitter and an ATW-R700 receiver. We have three sets of these. Do you think that these will be better to use than a Beta 57 at mid stage? Or do you not think that this is necessary? Keeping in mind these are 9-13 year olds.


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## epimetheus (Jul 23, 2009)

Move your C1000's away from the sides of the stage and get them away from the speakers. I'd place them about halfway between center stage and off stage on either side. You should also elevate the mics above the stage somewhat, a foot or so at least. Otherwise you'll pick up a lot of footsteps. That should help with your feedback. I'd use the headsets on the solo parts, even for 9-13 years olds, as long as it fits with the subject matter. I put lapel mics on that same age group for an Independence Day show at my church. It worked fine as long as your careful with the mutes. Kids say the darndest things...


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## AlexD (Jul 23, 2009)

Thank you, Ill try that when they finish.


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## AlexD (Jul 23, 2009)

I am going to be installing a permanent system soon and I was wondering what do you guys think about mounting condensers on the grid? Would it eliminate feedback if it was placed well and would it pick up the sound any differently? Do u recommend anything on that part?


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## epimetheus (Jul 23, 2009)

I wouldn't advise permanantly mounted mics, ever. I have flown mics in front of the proscenium before for a choir show. It was only for recording though, not amplification. And it was a $2000 set of mics.


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## AlexD (Jul 24, 2009)

we did a lot with the c 1000s and it wasn’t very good at all... it didn’t pick up anything from more than 1 and a half feet away from the mic... is this the type of mic or have i done something wrong with it? 

In the end we I did set up the wireless mic’s and got the sounding good with no feedback. But the director though it was going too far...? So we decided to rig a beta 58 on the grid about centre stage (where most of the singing was happening) and that worked quite well. I think with a more suited mic for sound reinforcement it would have worked better but this worked well for the mean time ( we had a day to rig all the sound and lighting and sort out the details... I would have made a better system if I had more time but I didn’t )


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## Anonymous067 (Jul 24, 2009)

If you ever get a chance, browse through Shure's (the brand) webpage, particularly the FAQ database. Many of the questions you continue to ask have answers there.

You will also notice something to this effect on their website quite frequently as a response to questions such as this one. "Will microphone X pick up source Y"
Answer: "There is no such thing as a magic microphone. It's simple physics, the closer the microphone is to the source, the better it will sound, and the more gain before feedback. PERIOD."

They also answer this questions a lot. "Which microphone is best?"
Answer: "If we answered that from a money point of view, our microphone X, at a price of 1200 dollars would be BEST". 

This may be their most expensive microphone in the world. You could go buy yourself a whole boatload of these microphones. If you don't have the ability, capability, and knowledge of how to position and condition this microphone, it isn't going to sound well! PERIOD.

Different microphones are made for different purposes, and they have to be used to the best of the condition they were designed for.

There is a reason that a wireless hairmounted microphone sounds the "best" (clear, sharp, no feedback issues, most gain before feedback), because the microphone is 6 inches from the mouth! If you put a 50,000 dollar mic 20 feet away from the mouth, and have a noisy room, is it going to sound good? NO!

Another line from Shure: Consider a talk show like Conan O'Brien or David Lettermen. They have essentially an unlimited budget and can buy the most expensive microphones in the world. However, they are still governed by the laws of physics and realize that in order to mic a person in the audience, the microphone MUST be close. You will notice they take a wired or wireless microphone into the audience so that it is within 1 foot of the persons mouth. 

Get my point yet?


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## Anonymous067 (Jul 24, 2009)

AlexD said:


> we did a lot with the c 1000s and it wasn’t very good at all... it didn’t pick up anything from more than 1 and a half feet away from the mic... is this the type of mic or have i done something wrong with it?
> 
> In the end we I did set up the wireless mic’s and got the sounding good with no feedback. But the director though it was going too far...? So we decided to rig a beta 58 on the grid about centre stage (where most of the singing was happening) and that worked quite well. I think with a more suited mic for sound reinforcement it would have worked better but this worked well for the mean time ( we had a day to rig all the sound and lighting and sort out the details... I would have made a better system if I had more time but I didn’t )



And BTW, a Beta58a is the big brother of one of THE most known, popular, and most used microphone in LIVE SOUND to this day, which is the SM58. These are both two microphones that are most commonly used in concerts and churchs alike. There's a reason.


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## Chris15 (Jul 26, 2009)

Blah067 said:


> There's a reason.



Because some years ago, someone decided they were the standard.

Folks there are far better vocal mics out there...


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## derekleffew (Jul 26, 2009)

Better in what sense? Price, availability, familiarity, rider-friendliness, durability? I specifically did not mention sound quality, but there are also many worse vocal mics than the ubiquitous SM-58.


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## Chris15 (Jul 26, 2009)

derekleffew said:


> Better in what sense? Price, availability, familiarity, rider-friendliness, durability? I specifically did not mention sound quality, but there are also many worse vocal mics than the ubiquitous SM-58.



And start that list of worse ones with the PG58 and follow with most things without a marked brand name.

How can you not consider sound quality?
Consider that at least in Australia it is cheaper to replace a 58 than replace the capsule if it goes.

I agree that durability wise they do have an advantage - we joked that the president uses 57s because the mic could be shot and would still keep going, albeit with the quality of a 57...

I'm not saying that it's necessarily a BAD mic, rather that just because it's the standard doesn't mean it's good...


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## AlexD (Jul 26, 2009)

Well I did some work in the national threat in London and they had two reinforcement mic’s placed 10 feet away form the stage on the sides of the stage and they picked up the stage very well. Of cores I want good sound quality that kind of comes as an unsaid rule really. I mean like the c1000 s will pick up sound well at 1 foot but go back 150mm and its like half as good go back to 2 feet and u hear nothing... what I was trying to ask is, is there a purposely designed line of mic’s for sound reinforcement for stage use?

What I’m going to do is mount the mic’s on the grid above the stage because that seems to work very well, the grid is about 1.7m above the stage. I was thinking of placing 2 beta 58s down stage on ever side and a condenser up stage in the middle. Would this work?
(I am getting some one in I’m just trying to learn here. Learn by doing)


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## Anonymous067 (Jul 26, 2009)

AlexD said:


> is there a purposely designed line of mic’s for sound reinforcement for stage use?



That's usually the purpose of MOST microphones...?
Except for specific recording-only mics...which isn't what you're asking for I assume?


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## Anonymous067 (Jul 26, 2009)

Chris15 said:


> And start that list of worse ones with the PG58 and follow with most things without a marked brand name.
> 
> How can you not consider sound quality?
> Consider that at least in Australia it is cheaper to replace a 58 than replace the capsule if it goes.
> ...



Ok ok. We all know the SM58 isn't the best mic around. But like you said, it's not a BAD mic, and you really shouldn't take shame in having it, just pride if you have better (IMHO).

I'd be happy to own a ton of Beta58's, I'd take those over the crappy AKG (bottom of line) "vocal" mics any day...

Not to mention, lots of hot names use SM58's for their lead as well as background vocalists...


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## derekleffew (Jul 26, 2009)

AlexD said:


> ... what I was trying to ask is, is there a purposely designed line of mic’s for sound reinforcement for stage use? ...




Blah067 said:


> That's usually the purpose of MOST microphones...? ...


Blah067, I think what AlexD is looking for is a shotgun mic, or perhaps a boundary mic.


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## AlexD (Jul 26, 2009)

I was thinking about shotgun mics but will they have enough range to pick up a stage well enough? If not you will need a more than two right? And they do cost quite a bit.

Also I looked at some boundary mics and don’t quit get what they are for... It said in a description that they can b used for recording but I can’t see them being any good for that. Are they the mics that are placed on the front of the stage on the floor? I keep seeing them being used but I never ask what they are.


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## Anonymous067 (Jul 26, 2009)

derekleffew said:


> Blah067, I think what AlexD is looking for is a shotgun mic, or perhaps a boundary mic.



That's fine and dandy, but I still don't think Alex understands that shotgun and boundary mics are not magical. In a semi-noisy room, a shotgun microphone won't sound half as good as a well positioned lav mic (probably wireless).

Even "choir" mics require great cooperation from the choir, and the mics must be relatively close. Choirs aren't exactly quiet either. If you have a loud room, with a timid 8 year old center stage, a shotgun from 50 feet away isn't going to do you much good!


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## Anonymous067 (Jul 26, 2009)

Again, from Shure's FAQ section...

Shotgun microphones are useful for camera or recording work when the microphone has to be about 3-4 feet away from the talkers and a PA system is not involved.

Shotgun microphones should not be used for public address applications. The rear polar response of a shotgun microphone is not consistent and has many lobes that are unpredictable. A shotgun mic is not an "audio zoom lens".

Also read this, since my word isn't "good enough"
Find an Answer.

Getting my point yet?


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## Anonymous067 (Jul 26, 2009)

AlexD said:


> I was thinking about shotgun mics but will they have enough range to pick up a stage well enough? If not you will need a more than two right? And they do cost quite a bit.
> 
> Also I looked at some boundary mics and don’t quit get what they are for... It said in a description that they can b used for recording but I can’t see them being any good for that. Are they the mics that are placed on the front of the stage on the floor? I keep seeing them being used but I never ask what they are.



Perhaps you can't see them being used in recording because you haven't had any experience with them before. I didn't use boundary microphones until a recent musical. When I decided, I don't need to mic the taps live...but I listened to the recording and decided, yep, I need to record the taps. 
Sometimes engineers use mics for different applications, and you shouldn't assume that every microphone you see is being used for what YOU hear. 

Another example to this is ambiance microphones. I recently did a gig with IEM (In ear monitor, look it up...), and had two mics placed downstage LR, and were used ONLY to pickup the audience. People frequently asked "why are you putting these mics into your speakers?". The truth is however, they weren't being used in the mains (or floor monitors), only in my ears. Don't ever assume...(if you ever do any REAL troubleshooting, you'll learn this quick).

Generally, microphone companies (well known ones anyhow...) are smart people. If they say it's primary use is for recording, that's probably what it's best at. No offense Alex, but any reputable microphone company is much smarter than you, or myself for that matter. I reiterate the fact that if they say something is for X, it probably is. Is that all it can be used for...no! Is it what it was DESIGNED for? Yes.


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## AlexD (Jul 27, 2009)

I know that a well placed mic can make it work much better. I was just asking was it feasible to use shotgun mics. I’m so use to close mic recordings it instantly went into my head when I saw recording on the boundary mic I starting thinking how would you use that in a dry room? I completely forgot about recording on stages. btw, I havent red up on boundry mics yet that's what i was going to do today. 

Also what I am trying to ask is that do condenser mics vary in the distance that they can pick up the sound and dose the pre amp make any different?


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## AlexD (Jul 27, 2009)

I have just read that link you gave me and sorry sometimes I don’t quite understand what I’m reading but I understood that so thank you for that link. From reading that wouldn’t mounting mics on the grid above the stage so that they pick up the whole stage evenly work much better than badly placed overheads?


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## museav (Jul 27, 2009)

Alex, just to address one issue, a mic being a condenser mic refers to how it operates (condenser, dynamic, ribbon, etc.) and not to the pattern or other characteristics. A condenser mic typically has a much higher signal level output than a dynamic and because the diaphragm can be lighter, often have a more 'open' sound, but both condensers and dynamics can be cardioid, supercardioid, hypercardioid, figure eight, etc. patterns.

Area micing for reinforcement gets tricky as it involves several factors and especially coordination with the sound system. I recently had someone recount a story where they walked into a situation that had flown choir mics and all sorts of gain before feedback problems. They ended up removing some of the mics and aiming those left not right at the choir but rather so that the nulls or minimums in the patterns were pointed at the speakers. So you can't look at just the mics, you have to look at the sound system as an integrated system and that what you do for one thing may affect other areas of the system.

Boundary mics can be very useful but keep in mind that to work effectively they need to be placed against a boundary with some area. I often use boundary mics for ambient mics for recording, in-ear/personal monitoring systems, ALS systems, etc. And they can be effective as footlight mics for picking up general stage audio, just remember that they will pick up all audio.

Probably the primary thing to keep in mind is that as the mic gets further from the source, the level hitting the mic drops off. The level hitting a mic 10' away is roughly 20dB down compared to one 1' away and thus the one 10' away has to be turned up 20dB to have the same level. At the same time, the room and speakers are going to interact much more with a sound traveling 10' than with one traveling 1', thus not only affecting what is picked up but if part of the live sound reinforcement, also affecting gain before feedback for that system. So minimizing the distance from source to mic and selecting mics that minimize the interaction with the environment and sound system for that specific application are usually the keys.


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## AlexD (Jul 27, 2009)

Yes as an A level music tec student I really should know about cardioid, supercardioid, hypercardioid ect patterns but I can never remember them... and as to the condenser isn’t that what you generally use for sound reinforcement? Or even on that overheads.
So what you’re saying is that you have to place the mic’s in consideration to the speakers, where the actors talk/sing and what eels?


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## gpforet (Jul 27, 2009)

Condenser mics respond to physics principles just like any other mic, energy drops off with the square of the distance.

The bottom line is you're asking for the impossible. It is simply not reasonable to think you can mic someone from a distance for sound reenforcement and expect to acheive anything more than a few db gain before feedback. Since 3 db is really the smallest change in volume percieveable by the human ear, distance micing for PA use results in quite possibly no noticable increase in volume before feedback occurs.

No matter how you ask the question, the answer is always the same. There is no way to effective mic a source from more than a few feed away and use that signal for sound reenforcement without feedback occuring before any noticable increase in volume.


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## AlexD (Jul 27, 2009)

I have just realized something… the reason I have been asking this question is to get a better understanding of cores and I “though” I had seen it been done but I just remembered that they did use wireless mic’s. And also I have just realized that most theaters have the grids really high up and the theater I’m in doesn’t its about 1.5m high and the set up I did could be refined so that the mic’s mounted on the grid could be turned up more without feedback. At least you guys cleared some stuff up I didn’t get so thanks for the info guys.


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## Anonymous067 (Jul 27, 2009)

As I've said 1000+ times in this thread...
The closer the microphone is to the source, the better it will sound. period.


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## AlexD (Jul 27, 2009)

Yes I know, I have read your replies what I wanted to know that can different mics pick up sound from fever away. But I know now that they don’t.


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## brubart (Aug 1, 2009)

Another way to improve gain-before-feedback is to place the speakers closer to the audience (on stands or hanging) and farther from the mics. 

The SPL or loudness of a conventional speaker's direct sound increases about 6 dB whenever you halve the distance from the speaker to the listener. That's 6 dB of free gain without any increase in feedback. Plus, the increase in direct/reverb sound ratio at the listeners' ears helps intelligibility. Close speakers sound more clear than distant speakers.

Mounting the speakers close to the audience also places the speakers farther from the mics, reducing the feedback loop gain. And it tends to place the speakers toward the 
backside of the directional mics, so you get some attenuation of the speakers' sound by the microphones.

Moving speakers closer to the audience requires that you re-think the number of speakers and their dispersion patterns in order to cover the audience evenly. You also may need to delay the signal going to the speakers so that the listener localizes the sound on stage, rather than at the nearest speaker.

Hope this helps,
Bruce Bartlett
Bartlett Microphones in Elkhart, Indiana - home page


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## AlexD (Aug 2, 2009)

To I have thought of doing this for the permanent install that will be happening but with the delay, the speakers will only be able to be moved like 2 or 3 meters in front of the stage and on the grid about one. Will this still need a delay?


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## museav (Aug 2, 2009)

brubart said:


> The SPL or loudness of a conventional speaker's direct sound increases about 6 dB whenever you halve the distance from the speaker to the listener. That's 6 dB of free gain without any increase in feedback. Plus, the increase in direct/reverb sound ratio at the listeners' ears helps intelligibility. Close speakers sound more clear than distant speakers.


This seems worth perhaps a bit more explanation. Because most indoor venues are not anechoic, while the difference in direct level when you double or halve the distance to the speaker is 6dB, the difference in overall level is usually less than 6dB as the actual level at the listener is a factor of both the direct and indirect sound paths and any reflections and other indirect sound paths add to the overall level received at the listener, thus reducing the actual loss in level obtained.

One result is that decreasing the distance from speaker to listener tends to not only result in greater direct level, but also a lower indirect sound component and thus a higher direct/indirect energy ratio, which does help with intelligibility. In fact, get a sufficient distance from the speaker and there is a point where the indirect sound level may equal the direct level and beyond that distance the level no longer changes with distance as it is dominated by the indirect sound, this is the reverberant field.

The second issue is that reducing the talker to microphone distance can typically be more effective in increasing potential system gain before feedback than trying to reduce the speaker to listener distance. Not only is it often easier to move the microphone closer to the person talking than to move the listeners closer to the speaker, but halving the talker to microphone distance will also typically provide a 6dB increase in gain before feedback while halving the speaker to listener distance will usually provide something less than that since there are likely indirect sound paths involved.


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## jkowtko (Aug 5, 2009)

Blah067 said:


> As I've said 1000+ times in this thread...
> The closer the microphone is to the source, the better it will sound. period.



Any that's why on Broadway nowadays they almost exclusively use body mics for reinforcing the actors' voices. Unfortunately it tends to me more expensive, especially when the cast is large, but currently it's the winning strategy.


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## jkowtko (Aug 5, 2009)

brubart said:


> Another way to improve gain-before-feedback is to place the speakers closer to the audience (on stands or hanging) and farther from the mics.



Alex, from the photos you posted it looks like your theater arrangement is similar to ours, i.e. curved seating area, thrust stage, no pit, etc. Since there is no separation of stage from audience (i.e. an orchestra pit) the balance between audience coverage and feedback into actor's mics will be delicate.

In our theater we are fortunate to have highly raked seating (rises 8 feet from to back with 10 rows of seating) so the grid-height placement of our L, C and R speakers works out okay.

Similar to what was mentioned already, for performances involving body mcis you might consider placing small downfills on stands in front of the stage to take some of the burden off the mains and get the vocals out to the audience more easily. Professional houses make heavy use of small fill speakers for this purpose, and in my experience (watching shows) it works great 

-- John


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## AlexD (Aug 9, 2009)

I haven’t posted any photos of the threat I am in but it sounds the save just not a curved stage. I have seen those fill speakers and they do look like they work might try and see if we can get some, because they will be at the front of the stage wouldn’t you have to place some further up the audience to make sure people at the back can hear well?


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## gpforet (Aug 10, 2009)

AlexD said:


> To I have thought of doing this for the permanent install that will be happening but with the delay, the speakers will only be able to be moved like 2 or 3 meters in front of the stage and on the grid about one. Will this still need a delay?



I calculate any required delays based on the distance between my acoustic source, and the FOH line. Anything less than 15 to 20 ft I don't even both with. I also don't bother if it's just spoken word or dialog since my experience is that once I mic an actor, they quit projecting and the acoustic component is minimal. Beyond that, the rule of thumb is 1ms per foot. Again, this is measured from the plane of the sound source relative to the plane of the FOH line.


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## museav (Aug 10, 2009)

epimetheus said:


> You should also elevate the mics above the stage somewhat, a foot or so at least. Otherwise you'll pick up a lot of footsteps.


The problem is that by raising the mic off the stage you can then encounter reflections off the stage causing combfiltering at the mic. It is usually best to either keep the mic as close the boundary surface as possible, the concept behind boundary mics, some distance away from the boundary or to have a boundary that is absorptive at the frequencies involved.


AlexD said:


> I haven’t posted any photos of the threat I am in but it sounds the save just not a curved stage. I have seen those fill speakers and they do look like they work might try and see if we can get some, because they will be at the front of the stage wouldn’t you have to place some further up the audience to make sure people at the back can hear well?


The main body of the audience should be covered by the main speakers, front fills are usually to add just what is needed for those seated in the first few of rows due to their being out of the main coverage of the main speakers (a result of locating, aiming and selecting the main speakers to reduce the levels on stage and increase gain before feedback) at some frequencies. Thus fills are usually fairly low level and primarily higher frequencies since the mains are likely less directional at lower frequencies. Front fills are often delayed to the natural sound on stage.


gpforet said:


> I calculate any required delays based on the distance between my acoustic source, and the FOH line. Anything less than 15 to 20 ft I don't even both with. I also don't bother if it's just spoken word or dialog since my experience is that once I mic an actor, they quit projecting and the acoustic component is minimal. Beyond that, the rule of thumb is 1ms per foot. Again, this is measured from the plane of the sound source relative to the plane of the FOH line.


Delays can be important for spoken word since it can affect intelligibility. How much delay is appropriate, and whether it is needed at all, depends on the situation. For one thing, any delay is relative to the distances from the natural source to the listener as compared to the distance from the speaker to the listener. Most theatres have more than one listener which means that these relationships vary for different listeners. If you do have just one listener, then delay time for the speakers is probably well down the list of things to be worried about.

A related factor in setting any delay is that not only do you have a listener area rather than a finite point, but you also often have a source area rather than a finite point. Now the speaker locations become the only fixed reference with a range of natural source and listener locations. This makes determining and setting any delays a sort of "best fit" exercise, what helps overall without negatively impacting specific locations to much. With a band performance some people will delay to the drums since that is often the source of the most impulsive, and fairly high level, natural sounds and thus the ones that may most readily show any differences in timing.

Another factor is that you have to think in three dimensions. If the speakers are overhead then they have some delay from the vertical distance to the listeners, in fact you can readily get to where you have to worry about having too much delay if the speakers are too high. For many applications with speakers mounted over a proscenium, that alone may provide sufficient delay to make the sound appear to come from where the actors are on stage.

Then there's precedence or Haas Effect, where you intentionally delay a secondary source such as a fill speaker by an additional time, typically 10-20ms, relative to the natural sound or primary source so that the natural or primary source takes precedence in establishing localization or the location of the source. This works even when the secondary source level is 10dB or more greater than the natural or primary source level.

The point is that while a simple two dimensional estimate may get you started in assessing potential delay times for speakers, the actual settings for speaker delays are usually something that has to be verified and tweaked in the field.


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## derekleffew (Aug 10, 2009)

museav said:


> ...If you do have just one listener, then delay time for the speakers is probably well down the list of things to be worried about. ...


Charlie Babbit made a joke. See everyone, I told you Brad had a sense of humor.


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## museav (Aug 11, 2009)

derekleffew said:


> Charlie Babbit made a joke. See everyone, I told you Brad had a sense of humor.


So you're comparing me to Tom Cruise? Guess there's both good and bad in that.


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