aural reference clap for setting delays between choir spot mics andmain stereo pair

[lewdslewrate]

Hopefully a quickie. I read somewhere that a clap or other sharp
sound can be used to set an aural reference to help setting delays
between spot mics and a main stereo pair...for example. Post said
stand under main pair and clap.......would it not be better to stand
in front of (choir) spot and clap?? or am i missing something?

cheers

[hank alrich]

lewdslewrate > wrote:

> Hopefully a quickie. I read somewhere that a clap or other sharp
> sound can be used to set an aural reference to help setting delays
> between spot mics and a main stereo pair...for example. Post said
> stand under main pair and clap.......would it not be better to stand
> in front of (choir) spot and clap?? or am i missing something?
>
> cheers

What you're after is the distance between the two pairs, measured by the
speed of sound from one pair to the next. Standing close to the main
pair reduces the amount of room spill into those and makes it easier to
align the waveforms in post.

Regardless of where you stand the distance, and therefore the delay
time, remains the same for the given ambient temperature and barometric
pressure. Proximity to the main pair puts the source of the impulse as
close as possible to both pairs, simplifying the postproduction
alignment process.

--
shut up and play your guitar * http://hankalrich.com/
http://armadillomusicproductions.com/who'slistening.html
http://www.sonicbids.com/HankandShaidriAlrichwithDougHarman

[Frank Stearns]

(hank alrich) writes:

>lewdslewrate > wrote:

>> Hopefully a quickie. I read somewhere that a clap or other sharp
>> sound can be used to set an aural reference to help setting delays
>> between spot mics and a main stereo pair...for example. Post said
>> stand under main pair and clap.......would it not be better to stand
>> in front of (choir) spot and clap?? or am i missing something?
>>
>> cheers

>What you're after is the distance between the two pairs, measured by the
>speed of sound from one pair to the next. Standing close to the main
>pair reduces the amount of room spill into those and makes it easier to
>align the waveforms in post.

>Regardless of where you stand the distance, and therefore the delay
>time, remains the same for the given ambient temperature and barometric
>pressure. Proximity to the main pair puts the source of the impulse as
>close as possible to both pairs, simplifying the postproduction
>alignment process.


Hank's correct in the first paragraph, but in the second paragraph it's not quite
that simple, unfortunately.

In your mind's eye, start setting a bunch of vectors (or "rays" they might have
called them in old-timey high-school geometry) from the various acoustic sources to
the main pair, and to other pairs or spots along the way that pick up the
same acoustic source. The vector difference is the starting point for the delay
you'll want to use.

As you move around to different points where acoustic sound originates in your
ensemble, the distance relationships change -- and thus so does the optimal delay
for alignment. Standing in one place -- standing the *wrong* place -- is going to
give you useless alignment marks.


There are some additional considerations to mitigate this:

(But first: Don't use hand claps -- really hard to see. Go to a pet store and get a
"dog clicker/trainer". They cost about US$1.50 and give a nice pair of visible HF
transients that are generally easy to distinguish from room reverb. Practice using
this little clicker until you get sharp, clean clicks and not thumps from pushing
too slow or keeping your thumb on the metal resonator. And, try to do the click
session when the room is quiet. A starter pistol firing blanks is great, too, but
might get you in trouble if people see you waving a gun around and firing it.)


- The level of the "earlier" pickup mic(s) to the main pair: The lower it is, the
less problematic it will be in the mix, even if not optimally delayed.

- If many acoustic sources enter both pickup points at nearly the same level, you'll
have different optimal delay times for each source. It can drive you crazy. The
solution is to push the delay a bit more than what might be arithmetically perfect.

This way you step around the worst comb-filter envelope. But don't get so far out
that you go beyond the Haas threshold (the point at which the human ear detects
distinct echos, approximately 40 mS)

- Don't forget "cross-bleed" between your spots. Use good mics with good patterns,
properly positioned.

The reference impulse is really just a guide to "rough in" your alignment. For the
reasons cited above, you'll need to listen carefully. When setting delays, I first
identify which mic pair will be the reference (generally the pickup point that is
farthest away, the main pair). Next, one at a time, I bring up what I want to delay
to equal volume, even though it's unlikely it will be used in the mix that high.

Important side note! You of course want to record your "click session". Be sure to
shout out or make careful notes as to where you are as you do each click -- and
you'll want to click in the area covered by each close mic or mic pair. (I get as
close as I can to where the actual closer-mic'd acoustic source(s) will be during
the performance and click from there.) Get a few general area references as well,
such as "chorus top row left, center, and right".

In post, after fussing a bit with visual alignments, I start stepping through delay
amounts, *listening* for focus and sweetness. And do be aware that at 44.1K
sampling, you might find that in many cases there's a very narrow window, sometimes
on the order 1 to 3 samples(!), that get you to that optimum-sounding delay value.

(These days, I rarely bother with click sessions and just do it by approximate
physical distance, fine-tuned by ear.)

When you bring up multiple sources that have a lot of bleed, you need to finese a
bit more.


All this is a great argument AGAINST multi-mic'ing. And in a perfect world I'd
agree. But for a laundry list of practical reasons (bad rooms and iffy players being
#1 and #2), these spots can do wonders for the overall presentation and sound -- if
you use them properly.

Good luck with it,

Frank
Mobile Audio
--

[malachi[_4_]]

"Frank Stearns" > wrote in message
acquisition...
> (hank alrich) writes:
>
>>lewdslewrate > wrote:
>
>>> Hopefully a quickie. I read somewhere that a clap or other sharp
>>> sound can be used to set an aural reference to help setting delays
>>> between spot mics and a main stereo pair...for example. Post said
>>> stand under main pair and clap.......would it not be better to stand
>>> in front of (choir) spot and clap?? or am i missing something?
>>>
>>> cheers
>
Be sure to specify exactly what kind of clap you are requesting.

[Peter Larsen[_3_]]

malachi wrote:

> Be sure to specify exactly what kind of clap you are requesting.

Single hand has the lowest measurable distortion and excellent aural safety
but s/n tends to be poor.

kind regards

Peter Larsen

[Peter Larsen[_3_]]

lewdslewrate wrote:

> Hopefully a quickie. I read somewhere that a clap or other sharp
> sound can be used to set an aural reference to help setting delays
> between spot mics and a main stereo pair...for example. Post said
> stand under main pair and clap.......would it not be better to stand
> in front of (choir) spot and clap?? or am i missing something?

It is a good simple distance measurement that stays with the recorded
tracks. So go to each mic, clap and identify the mic. Some day you may be
glad you did just that. It does however not replace a drawing of the session
lay-out, it supplemenets it. It is also nice to have some photographs.

> cheers

Kind regards

Peter Larsen

[Arny Krueger]

"lewdslewrate" > wrote in message

> Hopefully a quickie. I read somewhere that a clap or
> other sharp sound can be used to set an aural reference
> to help setting delays between spot mics and a main
> stereo pair...for example. Post said stand under main
> pair and clap.......would it not be better to stand in
> front of (choir) spot and clap?? or am i missing
> something?

If you are following the 3:1 rule, setting delays is arguably futile. You
solved the problem a better way.

Going for milisecond timing when micing a choir ignores the whole purpose of
a choir, which is spreading the spectrum of the vocal music in frequency and
time.

[Scott Dorsey]

Arny Krueger > wrote:
>"lewdslewrate" > wrote in message

>> Hopefully a quickie. I read somewhere that a clap or
>> other sharp sound can be used to set an aural reference
>> to help setting delays between spot mics and a main
>> stereo pair...for example. Post said stand under main
>> pair and clap.......would it not be better to stand in
>> front of (choir) spot and clap?? or am i missing
>> something?
>
>If you are following the 3:1 rule, setting delays is arguably futile. You
>solved the problem a better way.

He's talking about mixing spot and ambient mikes for recording, not PA.

>Going for milisecond timing when micing a choir ignores the whole purpose of
>a choir, which is spreading the spectrum of the vocal music in frequency and
>time.

That is true, though. But remember, your spot mikes are getting everything,
including the orchestra. Proper timing can reduce their influence on the
rest of the ensemble. But it's something you can readily do by ear; when the
offset is right, it's pretty clear.
--scott

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

[Ron Capik[_3_]]

On 4/16/2011 4:31 AM, Peter Larsen wrote:
> malachi wrote:
>
>> Be sure to specify exactly what kind of clap you are requesting.
>
> Single hand has the lowest measurable distortion and excellent aural safety
> but s/n tends to be poor.
>
> kind regards
>
> Peter Larsen
>
Then there's always Steve Howe's Clap:
< http://www.youtube.com/watch?v=1KN2qvtosmM >

Later...
Ron Capik
--

[Carey Carlan]

lewdslewrate > wrote in news:d7b5fe5f-7ba9-4673-
:

> Hopefully a quickie. I read somewhere that a clap or other sharp
> sound can be used to set an aural reference to help setting delays
> between spot mics and a main stereo pair...for example. Post said
> stand under main pair and clap.......would it not be better to stand
> in front of (choir) spot and clap?? or am i missing something?
>
> cheers

Agree to all of the above with one caveat.

Any ambient microphones placed in the hall away from the group DO NOT get
synchronized. These "reverb" mics include the delay as part of their
content. You may, in fact, increase the delay to get a stronger, thicker
room sound.

[Arny Krueger]

"Scott Dorsey" > wrote in message

> Arny Krueger > wrote:
>> "lewdslewrate" > wrote in
>> message
>>
>>> Hopefully a quickie. I read somewhere that a clap or
>>> other sharp sound can be used to set an aural reference
>>> to help setting delays between spot mics and a main
>>> stereo pair...for example. Post said stand under main
>>> pair and clap.......would it not be better to stand in
>>> front of (choir) spot and clap?? or am i missing
>>> something?

>> If you are following the 3:1 rule, setting delays is
>> arguably futile. You solved the problem a better way.

> He's talking about mixing spot and ambient mikes for
> recording, not PA.

I was unaware that the 3:1 rule did not hold for recording. I'm pretty sure
that most authories say that it does. The underlying physics say that it
should. Fool that I am, I always try to honor it.

>> Going for milisecond timing when micing a choir ignores
>> the whole purpose of a choir, which is spreading the
> spectrum of the vocal music in frequency and time.

> That is true, though. But remember, your spot mikes are
> getting everything, including the orchestra.

One might look at an orchestra as an instrumental choir...

> Proper timing can reduce their influence on the rest of the
> ensemble. But it's something you can readily do by ear;
> when the offset is right, it's pretty clear. --scott

Again, that's one of those things for which really good unbiased evidence
does not exist. It would seem to me that time alignment would have a
benefit where you can't honor the 3:1 rule without it.

[Scott Dorsey]

Arny Krueger > wrote:
>"Scott Dorsey" > wrote in message
>> Arny Krueger > wrote:
>>> "lewdslewrate" > wrote in
>>> message
>>>
>>>> Hopefully a quickie. I read somewhere that a clap or
>>>> other sharp sound can be used to set an aural reference
>>>> to help setting delays between spot mics and a main
>>>> stereo pair...for example. Post said stand under main
>>>> pair and clap.......would it not be better to stand in
>>>> front of (choir) spot and clap?? or am i missing
>>>> something?
>
>>> If you are following the 3:1 rule, setting delays is
>>> arguably futile. You solved the problem a better way.
>
>> He's talking about mixing spot and ambient mikes for
>> recording, not PA.
>
>I was unaware that the 3:1 rule did not hold for recording. I'm pretty sure
>that most authories say that it does. The underlying physics say that it
>should. Fool that I am, I always try to honor it.

Are you sure you understand the point of the 3:1 rule? It is only a very,
very rough rule which applies to mixing spot-mikes on instruments, and only
to microphones with a particular pattern.

It does not apply at all once you start getting into the far field. It does
not apply once the pattern stops being an even cardioid. It does not apply
once you start talking about stereo pairs. It does not apply in situations
where comb filtering can be used to your advantage either.

>> Proper timing can reduce their influence on the rest of the
>> ensemble. But it's something you can readily do by ear;
>> when the offset is right, it's pretty clear.
>
>Again, that's one of those things for which really good unbiased evidence
>does not exist. It would seem to me that time alignment would have a
>benefit where you can't honor the 3:1 rule without it.

I'm not sure you understand the point of the 3:1 "rule."
--scott

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

[Peter Larsen[_3_]]

Ron Capik wrote:

> On 4/16/2011 4:31 AM, Peter Larsen wrote:

>> malachi wrote:

>>> Be sure to specify exactly what kind of clap you are requesting.

>> Single hand has the lowest measurable distortion and excellent aural
>> safety but s/n tends to be poor.

> Then there's always Steve Howe's Clap:
> < http://www.youtube.com/watch?v=1KN2qvtosmM >

Happy guitar, [like]

> Later...
> Ron Capik

Kind regards

Peter Larsen

[Arny Krueger]

"Scott Dorsey" > wrote in message

> Arny Krueger > wrote:

>> I was unaware that the 3:1 rule did not hold for
>> recording. I'm pretty sure that most authories say that
>> it does. The underlying physics say that it should. Fool
>> that I am, I always try to honor it.

> Are you sure you understand the point of the 3:1 rule?

Well, I understand it well enough to benefit from it from time to time.

> It is only a very, very rough rule which applies to
> mixing spot-mikes on instruments, and only to microphones
> with a particular pattern.

I was unware of those *restrictions*.

I know what the 3:1 rule tries to address and of course its a rough rule.
But I was unaware that it only applied to spot mics, and mics with a certain
patterns. It seems to me that the comb filtering it addresses may or may not
be a problem depending on pickup pattern but I can how you can end up with
comb filtering with a variety of mic patterns.


> It does not apply at all once you start getting into the
> far field.

I thought it was well known that far field is outside its realm of
applicability. Seems like common sense.

> It does not apply once the pattern stops
> being an even cardioid.

I don't see that. Please explain.

> It does not apply once you start talking about stereo pairs.

Within the pair or over all?

> It does not apply in
> situations where comb filtering can be used to your
> advantage either.

That seems obvious since the 3:1 rule is about avoiding comb filtering.

>>> Proper timing can reduce their influence on the rest
>>> of the ensemble. But it's something you can readily do
>>> by ear; when the offset is right, it's pretty clear.

>> Again, that's one of those things for which really good
>> unbiased evidence does not exist. It would seem to me
>> that time alignment would have a benefit where you can't
>> honor the 3:1 rule without it.

> I'm not sure you understand the point of the 3:1 "rule."

I'm not sure you managed to shed any light other than a mixture of obvious
and unexplained points.

Besides you made a general claim that the 3:1 rule does not hold for
recording and then added all these qualifications.

In the end you only supported the idea that the 3:1 doesn't always hold in
every case, which seems obvious.

[Scott Dorsey]

Arny Krueger > wrote:
>"Scott Dorsey" > wrote in message
>
>> It does not apply once the pattern stops
>> being an even cardioid.
>
>I don't see that. Please explain.

If the microphone is an omni, it will pick up more external sound, and
correspondingly will need to be closer to the source in order to have the
same ratio of direct to diffuse sound. Likewise if it is a hypercardioid,
it can be farther.

The 3:1 rule isn't _just_ about time delay, it's also about amplitude.

>> It does not apply once you start talking about stereo pairs.
>
>Within the pair or over all?

Overall, because you're dealing with the far field at that point. You don't
stick stereo pairs up into instruments.

>Besides you made a general claim that the 3:1 rule does not hold for
>recording and then added all these qualifications.

I didn't, someone else said it didn't hold for recording. Since the
example was of far-field recording, I would agree that it certainly doesn't
apply there.

>In the end you only supported the idea that the 3:1 doesn't always hold in
>every case, which seems obvious.

It holds in only very few cases, which is not to say that it's not a good
general rule in those cases. But it can be very misleading.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Scott Dorsey" > wrote in message

> Arny Krueger > wrote:
>> "Scott Dorsey" > wrote in message
>>
>>> It does not apply once the pattern stops
>>> being an even cardioid.
>>
>> I don't see that. Please explain.
>
> If the microphone is an omni, it will pick up more
> external sound, and correspondingly will need to be
> closer to the source in order to have the same ratio of
> direct to diffuse sound. Likewise if it is a
> hypercardioid, it can be farther.

Well yes, but saying that you can vary the target ratio based on microphone
directivity and orientation is not the same as trashing the basic idea.

I checked about a dozen renditions of the meaning of the 3:1 rule and *none*
restricted it to a certain pickup patten.

> The 3:1 rule isn't _just_ about time delay, it's also
> about amplitude.

Yes, its about the ratio of the two. One source pointed out that it
presumes that the sources have equal loudness and are mixed to equal
loudness. Seems true.

>>> It does not apply once you start talking about stereo
>>> pairs.

>> Within the pair or over all?

> Overall, because you're dealing with the far field at
> that point. You don't stick stereo pairs up into
> instruments.

Check.

>> Besides you made a general claim that the 3:1 rule does
>> not hold for recording and then added all these
>> qualifications.

> I didn't, someone else said it didn't hold for recording.
> Since the example was of far-field recording, I would
> agree that it certainly doesn't apply there.

So you believe in adding time delays to mics in the far field?

>> In the end you only supported the idea that the 3:1
>> doesn't always hold in every case, which seems obvious.

> It holds in only very few cases, which is not to say that
> it's not a good general rule in those cases. But it can
> be very misleading. --scott

Lets be clear - its a rule of thumb, not a scientific law.

[Scott Dorsey]

Arny Krueger > wrote:
>"Scott Dorsey" > wrote in message
>> Arny Krueger > wrote:
>>> "Scott Dorsey" > wrote in message
>>>
>>>> It does not apply once the pattern stops
>>>> being an even cardioid.
>>>
>>> I don't see that. Please explain.
>>
>> If the microphone is an omni, it will pick up more
>> external sound, and correspondingly will need to be
>> closer to the source in order to have the same ratio of
>> direct to diffuse sound. Likewise if it is a
>> hypercardioid, it can be farther.
>
>Well yes, but saying that you can vary the target ratio based on microphone
>directivity and orientation is not the same as trashing the basic idea.

It is a rule that has so many exceptions that it's hardly a rule at all.

>I checked about a dozen renditions of the meaning of the 3:1 rule and *none*
>restricted it to a certain pickup patten.

I know, this is much of the problem. You'll see it stated in a whole bunch
of ways all over the place and nobody ever BEGINS to list the limitations.

>> The 3:1 rule isn't _just_ about time delay, it's also
>> about amplitude.
>
>Yes, its about the ratio of the two. One source pointed out that it
>presumes that the sources have equal loudness and are mixed to equal
>loudness. Seems true.

That's true also.

>> I didn't, someone else said it didn't hold for recording.
>> Since the example was of far-field recording, I would
>> agree that it certainly doesn't apply there.
>
>So you believe in adding time delays to mics in the far field?

When it sounds good. Not when it doesn't sound good. But that is a
different problem altogether and not related to the 3:1 rule.

More likely, though, you need to _advance_ microphones in the far field to
make them line up with spots.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."