[Mxsmanic]

How do you prevent a feedback loop between a microphone and a speaker or
amplifier that is emitting the sound recorded by the mic? And if feedback
occurs, how do you stop it?

A musician told me that you must not cover the mic to stop the feedback, even
though that seems logical to me. Is he right or wrong?

Also, why is feedback sometimes called larsen (if I've spelled that right)?

[Scott Dorsey]

Mxsmanic wrote:
How do you prevent a feedback loop between a microphone and a speaker or
amplifier that is emitting the sound recorded by the mic? And if feedback
occurs, how do you stop it?

A good introduction to basic theory can be found in the Yamaha Sound
Reinforcement Handbook. I strongly recommend reading it.

A musician told me that you must not cover the mic to stop the feedback, even
though that seems logical to me. Is he right or wrong?

If you cover the mike you will change the pattern. Since cardioid microphones
have side vents and front vents, covering the front vent is apt to turn them
into an omni microphone which will cause more feedback because it will pick
up more sounds from the side.

Also, why is feedback sometimes called larsen (if I've spelled that right)?

That's one I've never heard.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ron Capik[_3_]]

On 3/25/2012 1:50 PM, Scott Dorsey wrote:
wrote:
...snip...

Also, why is feedback sometimes called larsen (if I've spelled that right)?

That's one I've never heard.
--scott

I thought that came up here once. Anyway, from wiki:

Audio feedback (also known as the Larsen effect
after the Danish scientist, Søren Absalon Larsen,
who first discovered its principles)
==

Later...
Ron Capik
--

[Mxsmanic]

Scott Dorsey writes:

A good introduction to basic theory can be found in the Yamaha Sound
Reinforcement Handbook. I strongly recommend reading it.

If it costs money, I can't afford it, but I'll keep it in mind.

If you cover the mike you will change the pattern. Since cardioid microphones
have side vents and front vents, covering the front vent is apt to turn them
into an omni microphone which will cause more feedback because it will pick
up more sounds from the side.

Interesting ... so what can you do? (Other than turning the mic off.)

That's one I've never heard.

I've discovered that Larsen was a Danish guy, but I'm not sure why he is
associated with feedback.

[hank alrich]

Ron Capik wrote:

On 3/25/2012 1:50 PM, Scott Dorsey wrote:
wrote:
...snip...

Also, why is feedback sometimes called larsen (if I've spelled that right)?

That's one I've never heard.
--scott

I thought that came up here once. Anyway, from wiki:

Audio feedback (also known as the Larsen effect
after the Danish scientist, Søren Absalon Larsen,
who first discovered its principles)

All wrong. It's called howlround. g

--
shut up and play your guitar * http://hankalrich.com/
http://www.youtube.com/walkinaymusic
http://www.sonicbids.com/HankandShaidri

[PStamler]

On Mar 25, 12:50*pm, (Scott Dorsey) wrote:
If you cover the mike you will change the pattern. *Since cardioid microphones
have side vents and front vents, covering the front vent is apt to turn them
into an omni microphone which will cause more feedback because it will pick
up more sounds from the side.

Also, if you cover the mic, you're creating a cavity resonance with
your hand, and the mic/speaker system will feed back worse.

How to stop it? Turn the mic's gain down in the PA system, move the
mic away from the speaker, use a mic with better off-axis rejection,
use a mic with flatter response (esp. off-axis), use a speaker with
flatter response.

And do read the Yamaha Sound Reinforcement Handbook. It doesn't cost
anything, if you get it from a public library. If your local library
doesn't have it, try interlibrary loan. It really does answer a lot of
basic questions.

Peace,
Paul

[Mike Rivers]

On 3/25/2012 1:06 PM, Mxsmanic wrote:

How do you prevent a feedback loop between a microphone and a speaker or
amplifier that is emitting the sound recorded by the mic?

Move the mic further away from the speaker or reduce the
gain of the system. If you're using a directional mic, take
advantage of its null and point that toward the speaker.
This is a performance technique that you learn by
experimenting.

And if feedback occurs, how do you stop it?

See above.

A musician told me that you must not cover the mic to stop the feedback, even
though that seems logical to me. Is he right or wrong?

That can change the directivity pattern of the mic. If there
was a null in the pickup pattern that's pointed toward the
speaker, chances are it won't be there if you cup your hand
over the front of the mic or cover the back of the mic if
it's one ported at the rear. If the null kept the gain down
far enough so that the system didn't feed back and the null
goes away so it's not rejecting the sound of the speakers,
then there could be enough gain for feedback.

Also, why is feedback sometimes called larsen (if I've spelled that right)?

I've never heard it called anything but feedback or howling.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Peter Larsen[_3_]]

Mxsmanic wrote:

How do you prevent a feedback loop between a microphone and a speaker
or amplifier that is emitting the sound recorded by the mic? And if
feedback occurs, how do you stop it?

2 parameters influence this: gain and frequency response of loudspeaker as
heard by the microphone. Note: this means that off axis response gets quite
important, and it also means that beautified frequency response curves are
meaningless, such usually smooth out narrow peaks and narrow peaks often are
the very issue that matters most.

A musician told me that you must not cover the mic to stop the
feedback, even though that seems logical to me. Is he right or wrong?

He is - generally speaking - right because covering or partly covering a
directional microphone turns it into an omnidirectional.

Also, why is feedback sometimes called larsen (if I've spelled that
right)?

It is not called larsen, it is called "the larsen effect" because some
larsen some time described it in some paper.

Kind regards

Peter Larsen

[cedricl[_2_]]

On Sunday, March 25, 2012 10:06:51 AM UTC-7, Mxsmanic wrote:
How do you prevent a feedback loop between a microphone and a speaker or
amplifier that is emitting the sound recorded by the mic? And if feedback
occurs, how do you stop it?


Immediately? Turn the mic down. In the future? Make sure the speakers are farther forward of the mics and/or put a graphic EQ on the system. Find the offending frequencies and pull them down on the EQ. (you can do this on the mic channel EQ too). If you find you're taking too many frequencies out, you don't have the right system for the room. If you're pushing the sound level so loud that it's feeding back it might mean you need to redistribute the speakers. Put another set of delay speakers (on a separate level control) farther out into the room so you're not trying to reach the back of the room with your front main speakers. Don't just try to blast the room. Put speakers where the audience is.

[Scott Dorsey]

Mxsmanic wrote:
Scott Dorsey writes:

A good introduction to basic theory can be found in the Yamaha Sound
Reinforcement Handbook. I strongly recommend reading it.

If it costs money, I can't afford it, but I'll keep it in mind.

Try a library.

If you cover the mike you will change the pattern. Since cardioid microphones
have side vents and front vents, covering the front vent is apt to turn them
into an omni microphone which will cause more feedback because it will pick
up more sounds from the side.

Interesting ... so what can you do? (Other than turning the mic off.)

You can turn the whole system gain down. You can turn down the gain on
that one mike. You can go to a graphic equalizer and pull down the slider
corresponding to the note the system is feeding back at. (This is a very
fast operation, and it's why PA people use graphic equalizers in spite of
their lack of control and wacky response). Or, you can use a narrowband
notch filter and slide it into place. Or you can yell at the performer
through his monitors and tell him to stop cupping the damn mike.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mxsmanic]

Scott Dorsey writes:

Try a library.

No English-language libraries near me, unfortunately.

You can turn the whole system gain down. You can turn down the gain on
that one mike. You can go to a graphic equalizer and pull down the slider
corresponding to the note the system is feeding back at. (This is a very
fast operation, and it's why PA people use graphic equalizers in spite of
their lack of control and wacky response). Or, you can use a narrowband
notch filter and slide it into place. Or you can yell at the performer
through his monitors and tell him to stop cupping the damn mike.

If you're the performer with the mic in your hand, and there's no way to turn
it off, is there anything you can do physically to stop the feedback (since
shielding the mic with the hand apparently only makes it worse)?

[Mike Rivers]

On 3/27/2012 6:53 AM, Mxsmanic wrote:

If you're the performer with the mic in your hand, and there's no way to turn
it off, is there anything you can do physically to stop the feedback (since
shielding the mic with the hand apparently only makes it worse)?

Move around until the feedback stops. That's assuming that
there's some place where the mic can be where there's no
feedback. If this is a chronic problem for you, you might
look at one of the "feedback eliminators" that can go in
line somewhere in the sound system. Some have a mic level
input so you can put it directly in line with the problem mic.

They work by automatically setting notch filters at the
feedback frequencies. They work pretty well on speech, so-so
on singing, and can be fooled by instruments that sound like
feedback. A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Mxsmanic]

Mike Rivers writes:

A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)? I've always had the impression that it occurred
semi-randomly, since a person seated in front of a mic might experience
feedback or might not.

I also think I've seen people tap the mic to stop feedback. Does that work,
and if so, why? Or am I just imagining that?

[geoff]

Mxsmanic wrote:
Scott Dorsey writes:

A good introduction to basic theory can be found in the Yamaha Sound
Reinforcement Handbook. I strongly recommend reading it.

If it costs money, I can't afford it, but I'll keep it in mind.

If you cover the mike you will change the pattern. Since cardioid
microphones have side vents and front vents, covering the front vent
is apt to turn them into an omni microphone which will cause more
feedback because it will pick up more sounds from the side.

Interesting ... so what can you do? (Other than turning the mic off.)

- Move the speakers (or performer) so that thespeakers are in front of the
mic(s).
- Reduce reflectiveness of surfaces behind the mics, and in general..

geoff

[geoff]

Mxsmanic wrote:
Mike Rivers writes:

A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)? I've always had the impression that it
occurred semi-randomly, since a person seated in front of a mic might
experience feedback or might not.

No.


I also think I've seen people tap the mic to stop feedback. Does that
work, and if so, why? Or am I just imagining that?

Yes.

geoff

[geoff]

Peter Larsen wrote:

It is not called larsen, it is called "the larsen effect" because some
larsen some time described it in some paper.


Was he Danish ;-)

geoff

[Mike Rivers]

On 3/27/2012 11:04 PM, Mxsmanic wrote:

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)?

Yes, if the gain of the system (which includes the
microphone, the speakers, and the air between them) is
greater than unity, the system will feed back at a
frequencies where what's going into the mic is in phase with
what's coming out of the speaker. These are both functions
of the distance between the mic and speaker. Get them far
enough from each other for a given system gain, and you
won't have feedback.

I've always had the impression that it occurred
semi-randomly, since a person seated in front of a mic might experience
feedback or might not.

No, it's not random, but things that affect the in-phase
signal that gets back to the microphone might appear to be
random since a small movement can cause a reflection to come
close enough into phase so as to allow feedback.

I also think I've seen people tap the mic to stop feedback. Does that work,
and if so, why? Or am I just imagining that?

It works if it gets the attention of the sound system
operator who makes an appropriate adjustment. And don't
judge feedback by what you see and hear on TV when someone
steps up to a mic and the first thing you hear before a word
comes out of his mouth is a little feedback. It isn't
supposed to work that way, but it's becaome a (TV) cue that
someone is about to speak.



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Mxsmanic]

Mike Rivers writes:

Yes, if the gain of the system (which includes the
microphone, the speakers, and the air between them) is
greater than unity, the system will feed back at a
frequencies where what's going into the mic is in phase with
what's coming out of the speaker. These are both functions
of the distance between the mic and speaker. Get them far
enough from each other for a given system gain, and you
won't have feedback.

So why is it that a speaker on a platform might be able to talk normally for
quite some time, and then suddenly feedback develops? What changes to cause
the feedback? Is it the speaker's movements, or the loudness of his voice, or
maybe some specific frequency in his speech?

No, it's not random, but things that affect the in-phase
signal that gets back to the microphone might appear to be
random since a small movement can cause a reflection to come
close enough into phase so as to allow feedback.

OK. And I suppose there's no easy way for the speaker himself to know what to
avoid in order to create a situation where feedback might abruptly start?

Yes, a sound engineer might be able to compensate, but often there isn't any
sound engineer, just a PA system or something without an attendant.

It works if it gets the attention of the sound system
operator who makes an appropriate adjustment. And don't
judge feedback by what you see and hear on TV when someone
steps up to a mic and the first thing you hear before a word
comes out of his mouth is a little feedback. It isn't
supposed to work that way, but it's becaome a (TV) cue that
someone is about to speak.

So it's a sound effect, rather than a reflection of reality?

Now that you mention it, it's true that I see that often in movies and on TV,
but I don't recall ever hearing feedback appear out of nowhere if nobody is
speaking, in real life.

[Scott Dorsey]

Mxsmanic wrote:

If you're the performer with the mic in your hand, and there's no way to turn
it off, is there anything you can do physically to stop the feedback (since
shielding the mic with the hand apparently only makes it worse)?

Unplug the mike. Get away from the speakers. Turn the mike back so that
it's not pointed at the monitors anymore. Hire a competent soundman.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Mxsmanic wrote:
Mike Rivers writes:

A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)? I've always had the impression that it occurred
semi-randomly, since a person seated in front of a mic might experience
feedback or might not.

No, it is entirely predictable. A competent PA operator will have a good
sense of where the feedback point of the system is and how much additional
gain he can add before the system feeds back. He should also have a good
notion of where the sound on stage is going, and therefore what locations and
angles are going to lead to feedback.

Usually as the system gain is increased, the system rings long, long before
it starts to feed back. The PA operator should hear the system ringing and
have a good idea what to do long before it breaks out into feedback.

Sometimes people will operate systems on the ragged edge where they are
constantly ringing. This is a sign the system is poorly designed for the
room and application. There is a major difference between high grade
speakers and microphones with tight pattern control and the crap that they
sell at the music store in terms of keeping sound where it belongs.

I also think I've seen people tap the mic to stop feedback. Does that work,
and if so, why? Or am I just imagining that?

No, it does nothing.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

It's been a long time since I've posted anything like the following, but it
needs to be said.

UseNet groups do not generally exist to tutor people, at length, in the
basics of the subject matter of that particular group.

I rarely ask questions before I've done research. And my questions are
usually (but not always) advanced questions. It is /unconscionable/ to
expect people to waste time writing little essays on "Feedback -- Its Causes
and Cures", when such material is covered in books, and (probably) multiple
Websites.

Inquiries such as "I've been studying XYZ, and don't really get (some aspect
of XYZ)" are fine. "I don't know anything about XYZ; please explain
everything about it" ARE NOT.

Don't expect other people to expend energy assisting you, when you have made
little or no effort on your own.

Is my point clear?

[Mike Rivers]

On 3/28/2012 9:53 AM, Mxsmanic wrote:

So why is it that a speaker on a platform might be able to talk normally for
quite some time, and then suddenly feedback develops? What changes to cause
the feedback? Is it the speaker's movements, or the loudness of his voice, or
maybe some specific frequency in his speech?

Could be any of those, or a change in the temperature or
humidity in the room, which affects the velocity of sound,
which affects the phase relationship around the feedback
path. Or it could be that some listeners who were absorbing
sound leave and there's now a reflection getting to the mic
that wasn't there before. But mostly it's because the system
wasn't set up right to begin with and it's operating too
close to the feedback threshold.

OK. And I suppose there's no easy way for the speaker himself to know what to
avoid in order to create a situation where feedback might abruptly start?

Of course there is. He needs to learn where not to stand,
and to speak close to the mic if he's not using a lavaliere
or some other pin-on mic. Singers who dance around on stage
and hand-hold the mic (Mick Jagger is a good example) learn
about where the pickup nulls of the mic are and make sure,
when he's squatting down right next to a monitor speaker,
that he has a null pointed at the speaker.

Yes, a sound engineer might be able to compensate, but often there isn't any
sound engineer, just a PA system or something without an attendant.

That's an invitation for problems, but when you work on the
cheap or ignorant, sometimes things aren't perfect. It's
possible for a system to work perfectly unattended but it
needs to be set up properly so that things can't go far
enough wrong to get feedback. This means placing the
speakers where the talker can't get in front of them,
telling him where to stand, and checking his voice to give
him enough gain to be heard but not so much that he has to
back away from the mic to avoid being too loud, which is
something else that contributes to feedback.



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Ron Capik[_3_]]

On 3/28/2012 10:09 AM, Scott Dorsey wrote:

Usually as the system gain is increased, the system rings long, long before
it starts to feed back. The PA operator should hear the system ringing and
have a good idea what to do long before it breaks out into feedback.

Sometimes people will operate systems on the ragged edge where they are
constantly ringing. This is a sign the system is poorly designed for the
room and application. There is a major difference between high grade
speakers and microphones with tight pattern control and the crap that they
sell at the music store in terms of keeping sound where it belongs.

--scott

I've noticed that this on the edge stuff seems to
happen way too frequently at political events.
I often wonder if they're clueless, cheap, or both.
Maybe it's an ego; if it's not on the edge it's not
loud enough...
==

Later...
Ron Capik
--

[Richard Webb[_3_]]

On Wed 2012-Mar-28 09:16, William Sommerwerck writes:
UseNet groups do not generally exist to tutor people, at length, in
the basics of the subject matter of that particular group.

INdeed, but then somebody steered him to the Yamaha sound
reinforcement handbook, which he says he can't afford, and
there's no public library nearby. Huh? NEw York City
doesn't have a library?

Inquiries such as "I've been studying XYZ, and don't really get
(some aspect of XYZ)" are fine. "I don't know anything about XYZ;
please explain everything about it" ARE NOT.

Agreed again. This is why I post occasionally pointers to
the newsgroup faq. This is also why I no longer keep the
op's posts on the bbs, but still see them when i access this group via another method. Mxsmanic needs to crack a book or two on the subject.

Don't expect other people to expend energy assisting you, when you
have made little or no effort on your own.

Is my point clear?

IT should be. YOu and I have both made the same point, as
has mIke Rivers and others.



Regards,
Richard
--
| Remove .my.foot for email
| via Waldo's Place USA Fidonet-Internet Gateway Site
| Standard disclaimer: The views of this user are strictly his own.

[Les Cargill[_4_]]

Jeff Henig wrote:
Ron wrote:

I've noticed that this on the edge stuff seems to
happen way too frequently at political events.
I often wonder if they're clueless, cheap, or both.
Maybe it's an ego; if it's not on the edge it's not
loud enough...
==

Later...
Ron Capik
--

Or maybe that's what they mean by a "ringing endorsement."

Thank me. (:^)


Gibbs me a break...

--
Les Cargill

[Mike Rivers]

On 3/28/2012 12:13 PM, Ron Capik wrote:

I've noticed that this on the edge stuff seems to
happen way too frequently at political events.
I often wonder if they're clueless, cheap, or both.

Most of them are very noisy so they need to get it really
loud, at least until the crowd quiets down. And then there's
no engineer to drop the gain to a sensible level so the
speaker has to back off from the mic.

Also, it doesn't look very good for a political figure to
hand-hold a mic an inch from his lips while giving his
speech. Then you couldn't see his lips move, so you
wouldn't know that he was lying. g


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Richard Webb[_3_]]

On Wed 2012-Mar-28 11:13, Ron Capik writes:
Sometimes people will operate systems on the ragged edge where they are
constantly ringing. This is a sign the system is poorly designed for the
room and application. There is a major difference between high grade
speakers and microphones with tight pattern control and the crap that they
sell at the music store in terms of keeping sound where it belongs.

I've noticed that this on the edge stuff seems to
happen way too frequently at political events.
I often wonder if they're clueless, cheap, or both.
Maybe it's an ego; if it's not on the edge it's not
loud enough...

Maybe, but usually cheap gets one clueless. REmember,
although these folks seem to deal with insane amounts of
money it doesn't go to the services they hire, they usually
cadge those for free if possible or pay minimally.

Might be some ego involved, but that usually comes with
clueless and cheap. System tuning and the tools to do it
probably aren't anywhere nearby, or aren't understood well
enough to be used appropriately.

OUr buddy George in Syracuse gets some of those, but then he knows what he's doing, and unless he just dry hires the gear I'm sure those he contracts for are well done. A lot of
these if not done for freebies by a "believer" in the cause
are dry hires quite often I'm sure.



Regards,
Richard
--
| Remove .my.foot for email
| via Waldo's Place USA Fidonet-Internet Gateway Site
| Standard disclaimer: The views of this user are strictly his own.

[Ron Capik[_3_]]

On 3/28/2012 6:53 PM, Mike Rivers wrote:
On 3/28/2012 12:13 PM, Ron Capik wrote:

I've noticed that this on the edge stuff seems to
happen way too frequently at political events.
I often wonder if they're clueless, cheap, or both.

Most of them are very noisy so they need to get it really loud, at least
until the crowd quiets down. And then there's no engineer to drop the
gain to a sensible level so the speaker has to back off from the mic.

A recent one that came to mind was one of the primary "debates"
on network TV. Took place in a quiet auditorium and there was ringing
all night. They must have had a live sound engineer or two there.

Also, it doesn't look very good for a political figure to hand-hold a
mic an inch from his lips while giving his speech. Then you couldn't see
his lips move, so you wouldn't know that he was lying. g

OK, no contest here. G
==

Later...
Ron C
--

[Arny Krueger[_4_]]

"Mxsmanic" wrote in message
...
Mike Rivers writes:

Yes, if the gain of the system (which includes the
microphone, the speakers, and the air between them) is
greater than unity, the system will feed back at a
frequencies where what's going into the mic is in phase with
what's coming out of the speaker. These are both functions
of the distance between the mic and speaker. Get them far
enough from each other for a given system gain, and you
won't have feedback.

So why is it that a speaker on a platform might be able to talk normally
for
quite some time, and then suddenly feedback develops? What changes to
cause
the feedback?



Is it the speaker's movements,

Could be.

Think about it. A good tool for taming feedback is a more directional mic.
Change the orientation of the mic and feedback comes and goes.

or the loudness of his voice, or

Probably not, but I've seen it happen.

maybe some specific frequency in his speech?

...and its duration.

My first bet. But small changes in the location of the source or other
things on stage or even in the house can matter.

OK. And I suppose there's no easy way for the speaker himself to know what
to
avoid in order to create a situation where feedback might abruptly start?

Some perforners can figure this out on the fly.

Yes, a sound engineer might be able to compensate, but often there isn't
any
sound engineer, just a PA system or something without an attendant.

Or the operator lacks the tools.

[Arny Krueger[_4_]]

"Scott Dorsey" wrote in message
...
Mxsmanic wrote:
Mike Rivers writes:

A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)? I've always had the impression that it
occurred
semi-randomly, since a person seated in front of a mic might experience
feedback or might not.

No, it is entirely predictable.

Predictable in the sense that feedback is determnistic. Recreate the
scenario exactly, and it happens. Whether anybody in particular knows the
exact recipie for a given mode of feedback is always in question.

Problem is, there are so many potentially relevant variables, in a system
that is near the edge.

A competent PA operator will have a good
sense of where the feedback point of the system is and how much additional
gain he can add before the system feeds back.

One can hear what the stability margins are during the show. Learning how to
detect incipient feedback is a useful skill.

He should also have a good
notion of where the sound on stage is going, and therefore what locations
and
angles are going to lead to feedback.

Could and should, but not always possible.

[Scott Dorsey]

Arny Krueger wrote:
"Scott Dorsey" wrote in message
Mxsmanic wrote:
Mike Rivers writes:

A better solution is to check for feedback when
you're setting up the system and don't let anyone fiddle
with the controls who doesn't know what he's doing.

Will feedback always occur under specific circumstances (mic position,
frequencies of sound, etc.)? I've always had the impression that it
occurred
semi-randomly, since a person seated in front of a mic might experience
feedback or might not.

No, it is entirely predictable.

Predictable in the sense that feedback is determnistic. Recreate the
scenario exactly, and it happens. Whether anybody in particular knows the
exact recipie for a given mode of feedback is always in question.

A competent PA operator will have checked the system out beforehand to find
out specifically where the stability issues are. It's his job. He'll have
had someone walk around stage with a microphone and found out where the
issues are, and at what frequencies, and to what degree.

Stagecraft is almost entirely about being able to predict what will happen
so that the show goes off exactly the way it's expected to. That goes for
lighting, sound, costuming, everything.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[John Williamson]

Scott Dorsey wrote:
Stagecraft is almost entirely about being able to predict what will happen
so that the show goes off exactly the way it's expected to. That goes for
lighting, sound, costuming, everything.


Or, to put it another way, the more you prepare and the harder you work
at it, the easier it looks.

--
Tciao for Now!

John.

[Mxsmanic]

William Sommerwerck writes:

It's been a long time since I've posted anything like the following, but it
needs to be said.

No, it doesn't. It just wastes bandwidth, ironically while complaining about
wasting bandwidth.

UseNet groups do not generally exist to tutor people, at length, in the
basics of the subject matter of that particular group.

Usenet exists for many purposes.

I rarely ask questions before I've done research.

You seem to be far less circumspect about criticizing others.

It is /unconscionable/ to expect people to waste time writing little
essays on "Feedback -- Its Causes and Cures", when such material is
covered in books, and (probably) multiple Websites.

Some people like to teach, others don't. Some people are different from you.

I routinely write very substantial posts in reply to questions posed by
others, even when the information I communicate can probably be found in books
somewhere. I like to explain, rather than complain.

Inquiries such as "I've been studying XYZ, and don't really get (some aspect
of XYZ)" are fine. "I don't know anything about XYZ; please explain
everything about it" ARE NOT.

You're entitled to your opinion.

Don't expect other people to expend energy assisting you, when you have made
little or no effort on your own.

Other people will probably do as they see fit, without checking their actions
against your list of conscionable activities first.

Is my point clear?

Yes, but it is unimportant.

[Mxsmanic]

Richard Webb writes:

I would agree, and this is one of the tasks that is always
required when I set up a system. iF, for a conference or
convention there will be microphones placed anywhere than a
"stage" or front area known locations that will be problems
are found as well, and either avoided, or the problem freqs
notched with eq if we must. IT's part of the job.

This is all well and good but I'm thinking about churches, schools, clubs,
etc., that cannot afford full-time or even part-time sound engineers and may
or may not have systems that were originally designed by competent pros.

[Scott Dorsey]

Mxsmanic wrote:
Richard Webb writes:

I would agree, and this is one of the tasks that is always
required when I set up a system. iF, for a conference or
convention there will be microphones placed anywhere than a
"stage" or front area known locations that will be problems
are found as well, and either avoided, or the problem freqs
notched with eq if we must. IT's part of the job.

This is all well and good but I'm thinking about churches, schools, clubs,
etc., that cannot afford full-time or even part-time sound engineers and may
or may not have systems that were originally designed by competent pros.

Then they get what they pay for.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Richard Webb[_3_]]

On Thu 2012-Mar-29 08:40, Scott Dorsey writes:
snip

Predictable in the sense that feedback is determnistic. Recreate the
scenario exactly, and it happens. Whether anybody in particular knows the
exact recipie for a given mode of feedback is always in question.

A competent PA operator will have checked the system out beforehand
to find out specifically where the stability issues are. It's his
job. He'll have had someone walk around stage with a microphone and
found out where the issues are, and at what frequencies, and to
what degree.


I would agree, and this is one of the tasks that is always
required when I set up a system. iF, for a conference or
convention there will be microphones placed anywhere than a
"stage" or front area known locations that will be problems
are found as well, and either avoided, or the problem freqs
notched with eq if we must. IT's part of the job.

Stagecraft is almost entirely about being able to predict what will
happen so that the show goes off exactly the way it's expected to.
That goes for lighting, sound, costuming, everything.

Again agreed. IF I have to do it 'quick and dirty" I might
not have been able to determine all this adequately, and
then we just have to roll with it, do a quick ring out and
go.

Regards,
Richard
--
| Remove .my.foot for email
| via Waldo's Place USA Fidonet-Internet Gateway Site
| Standard disclaimer: The views of this user are strictly his own.

[Mike Rivers]

On 3/29/2012 4:45 PM, Mxsmanic wrote:

This is all well and good but I'm thinking about churches, schools, clubs,
etc., that cannot afford full-time or even part-time sound engineers and may
or may not have systems that were originally designed by competent pros.

In that case, why should they even think that they can
expect or achieve professional results? This IS rocket
science and needs a rocket scientist to operate it properly.
Sound reinforcement is not like turning on the TV set.

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Mxsmanic]

Mike Rivers writes:

In that case, why should they even think that they can
expect or achieve professional results?

What's professional about simply avoiding feedback?

[Scott Dorsey]

Mike Rivers wrote:
On 3/29/2012 4:45 PM, Mxsmanic wrote:

This is all well and good but I'm thinking about churches, schools, clubs,
etc., that cannot afford full-time or even part-time sound engineers and may
or may not have systems that were originally designed by competent pros.

In that case, why should they even think that they can
expect or achieve professional results? This IS rocket
science and needs a rocket scientist to operate it properly.
Sound reinforcement is not like turning on the TV set.

You wouldn't expect your church to hire a preacher whose only knowledge of
the job is that he once read about Jesus in a magazine, would you? But
thousands of churches bring on sound guys who have similar qualifications
regarding audio....
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mxsmanic]

Scott Dorsey writes:

You wouldn't expect your church to hire a preacher whose only knowledge of
the job is that he once read about Jesus in a magazine, would you? But
thousands of churches bring on sound guys who have similar qualifications
regarding audio....

That's because churches place their priorities on religion, not sound.

Are there many sound engineering firms that hire cardinals to give them
spiritual advice?