HERE WE GO AGAIN.......

[ChrisCoaster]

Well, I've just started a new job in the hotel audio-visual industry
and, uh - ............Good morning madam! Newspapers? Right down
this hall to the gift shop, on the right.......and, I've already run
into my old gain quandary.

To keep this simple -........ no madam, that's the bathroom door, not
the gift shop - ....... err, uh, I'd like replies especially from
those who have worked hotel AV and other overhead house sound systems.

My new boss and I are at odds about where most of the signal should
come from: the mic-pre-input gains on the mixer, or the input knob and
master knob on the amp controlling the ballroom in question.
Basically, he's pro-amp end, and I'm pro-mixer end.......I'm sorry
sir, did you ask for the procrastinator's guild meeting?? It's on the
lower level, Salon B-SIMON, WATCH THE VACUUM CLEANER YOU'RE GOING TO -
VVVVVVVVVVVVVVVVVVVV-KRASHHHHHHHHHHHH!!!!!!! <crackle of walkie
static> AV to Security, Guest down in south Lobby, repeat Guest down
in south Lobby.......Ohhh, man...I think that vacuum sucked up his
loafer.....

He claims that running the mixer at unity and the closet amps low
results in rampant feed back, vs. running the mixer with no LED and
high amp settings.
Does this have to do with the speakers sprinkled overhead all over the
ceiling??

Thanks,

-ChrisCoaster.....Oh, you want to wear TWO lapel mikes?? Absolutely,
I'll roll another one in in two minutes.....!

(: o

[Richard Crowley]

"ChrisCoaster" wrote ...
> He claims that running the mixer at unity and the closet amps low
> results in rampant feed back, vs. running the mixer with no LED and
> high amp settings.
> Does this have to do with the speakers sprinkled overhead all over the
> ceiling??

Is he also the catering manager, or does he have any technical
background at all? :-) The question of where to run levels
("gain staging") is important to maintain optimal signal to noise
ratios, but has almost nothing to do with gain-before-feedback
issues.

Note that a more suitable newsgroup for sound reinforcement
questions is: news:alt.audio.pro.live-sound

[tim perry]

"ChrisCoaster" > wrote in message
om...
> Well, I've just started a new job in the hotel audio-visual industry
> and, uh - ............Good morning madam! Newspapers? Right down
> this hall to the gift shop, on the right.......and, I've already run
> into my old gain quandary.
>
> To keep this simple -........ no madam, that's the bathroom door, not
> the gift shop - ....... err, uh, I'd like replies especially from
> those who have worked hotel AV and other overhead house sound systems.
>
> My new boss and I are at odds about where most of the signal should
> come from: the mic-pre-input gains on the mixer, or the input knob and
> master knob on the amp controlling the ballroom in question.
> Basically, he's pro-amp end, and I'm pro-mixer end.......I'm sorry
> sir, did you ask for the procrastinator's guild meeting?? It's on the
> lower level, Salon B-SIMON, WATCH THE VACUUM CLEANER YOU'RE GOING TO -
> VVVVVVVVVVVVVVVVVVVV-KRASHHHHHHHHHHHH!!!!!!! <crackle of walkie
> static> AV to Security, Guest down in south Lobby, repeat Guest down
> in south Lobby.......Ohhh, man...I think that vacuum sucked up his
> loafer.....
>
> He claims that running the mixer at unity and the closet amps low
> results in rampant feed back, vs. running the mixer with no LED and
> high amp settings.

unity? you need 35 to 60 dB gain (depending on mic) to bring the signal up
to line level.

with the amps at max gain you have a better ability to create a situation
where you can induce feedback


> Does this have to do with the speakers sprinkled overhead all over the
> ceiling??

a distributed ceiling sound system can function with live mics but its
quit difficult (as you well know) to make it work as if it were a concert
PA.

the object in this type of system is to adjust levels until only one speaker
can be heard at any one point in the room. of cource as a practical matter
(assuming all speaker are set to the same power level and are spaces
eqidistantly) you are going to hear a combanation of the nearest, then the
next nearest (at a reduced SPL and slightly delayed) and so on.

the combination of this plus room accustics plus equipment charicteristics
plus gain and eq settings plus mic position and handeling all will determine
wheather you will get squeels or not.

try switching the mics to one with a hypercardioid pattern and/or add some
type of active feedback supression (i. e. sabine fbx ).

(yeah i know hotels seldom have the budget for real equipment) a beringer
shark dsp 110 might be in the price range




>
> Thanks,
>
> -ChrisCoaster.....Oh, you want to wear TWO lapel mikes?? Absolutely,
> I'll roll another one in in two minutes.....!
>
> (: o

[Scott Dorsey]

ChrisCoaster > wrote:
>
>He claims that running the mixer at unity and the closet amps low
>results in rampant feed back, vs. running the mixer with no LED and
>high amp settings.
>Does this have to do with the speakers sprinkled overhead all over the
>ceiling??

Feedback has nothing to do with gain structure, only with the total amount
of gain in the system.

Cleaning up the gain structure might allow you to get lower noise floors
and you might be able to turn things up more before it clips, but it should
not have anything to do with feedback unless you're also changing the total
system gain in the process.

Hotel AV is really a thankless job. I've never done it, but I have had to
work a lot of events in hotels and it is amazing the huge variation in hotel
AV staff quality out there. Some really great folks, and some real bozos
and you'll have to work with both kinds a lot.
--scott

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

[ScotFraser]

Your boss is just plain wrong. It has nothing to do with feedback, you can
obtain that with either approach, but his notion is erroneous. You get your
gain up front in the signal chain. Your boss's way is no more or less prone to
feedback, but it is assuredly noisier.

Scott Fraser

[Bryson]

Unless the mixer's level pots affect the bandwidth.........a lot.

ScotFraser wrote:
> Your boss is just plain wrong. It has nothing to do with feedback, you can
> obtain that with either approach, but his notion is erroneous. You get your
> gain up front in the signal chain. Your boss's way is no more or less prone to
> feedback, but it is assuredly noisier.
>
> Scott Fraser

[Mike Dobony]

"ChrisCoaster" > wrote in message
om...
> Well, I've just started a new job in the hotel audio-visual industry
> and, uh - ............Good morning madam! Newspapers? Right down
> this hall to the gift shop, on the right.......and, I've already run
> into my old gain quandary.
>
> To keep this simple -........ no madam, that's the bathroom door, not
> the gift shop - ....... err, uh, I'd like replies especially from
> those who have worked hotel AV and other overhead house sound systems.
>
> My new boss and I are at odds about where most of the signal should
> come from: the mic-pre-input gains on the mixer, or the input knob and
> master knob on the amp controlling the ballroom in question.
> Basically, he's pro-amp end, and I'm pro-mixer end.......I'm sorry
> sir, did you ask for the procrastinator's guild meeting?? It's on the
> lower level, Salon B-SIMON, WATCH THE VACUUM CLEANER YOU'RE GOING TO -
> VVVVVVVVVVVVVVVVVVVV-KRASHHHHHHHHHHHH!!!!!!! <crackle of walkie
> static> AV to Security, Guest down in south Lobby, repeat Guest down
> in south Lobby.......Ohhh, man...I think that vacuum sucked up his
> loafer.....
>
> He claims that running the mixer at unity and the closet amps low
> results in rampant feed back, vs. running the mixer with no LED and
> high amp settings.
> Does this have to do with the speakers sprinkled overhead all over the
> ceiling??
>
> Thanks,
>
> -ChrisCoaster.....Oh, you want to wear TWO lapel mikes?? Absolutely,
> I'll roll another one in in two minutes.....!
>
> (: o


Start with channel gain. Assuming you have a decent mixer, there should be
a button called Solo, PFL, or some other designation where you can check the
channel gain setting on the meter and ONLY that channel. "normal" peaks
when speaking or performing should be about -6 to 0 or Unity. The more
inputs you have the lower this gets (log10 (number of channels) * -10).
When speaking or singing the channel should stay above -20 or the input will
start blending into the floor noise.

The channel sliders should remain between about -5 and +5. There are
exceptions, such as changing speakers or singers. The main output also
needs to normally run between -5 and +5db.

If your sliders are set around -20 or so you will have a difficult time
getting control over sound levels as a very small change in slider position
makes tremendous changes in sound level. Zero or unity give you good
control over your sound levels.

Now comes the tricky part. You should run your amps at least at a half or
there abouts and never above about 75%. If you have the gain structure done
properly on the mixer and you need to run above 75% then you will be putting
quite a load on the amp and you will increase distortion. If you do need to
run above 75% then you better think seriously about either getting a bigger
amp or additional cooling. If you are running the amp much below half then
you have too big of an amp.

You can compensate a little by fudging the mixer settings a little lower or
higher all the way across the mixer, from gains to channel sliders to main
output sliders. I would not center my "normal" range any lower than -10 or
+5. Minus 10 is probably pushing it a little, but it should work okay.

It is not uncommon for pros to run amps rated at twice the capacity of the
speakers because they want the amps to be running in their sweet spot,
usually between 50 and 75%.

We are running our mains at about 50% and our monitors at about 30%. We
really should think about replacing the monitor amps with a lower capacity
unit, but we also expect to need more monitors in the near future so we will
probably keep what we have.

I would strongly suggest you download the Mackie manual for one of their
SR24*4 VLZ Pro at http://mackie.com/support/downloads/manuals.html. It will
give you the details and evidence to set it up properly.

--
Mike D.

www.stopassaultnow.org

Remove .spamnot to respond by email

[George]

> Now comes the tricky part. You should run your amps at least at a half or
> there abouts and never above about 75%. If you have the gain structure done
> properly on the mixer and you need to run above 75% then you will be putting
> quite a load on the amp and you will increase distortion. If you do need to
> run above 75% then you better think seriously about either getting a bigger
> amp or additional cooling. If you are running the amp much below half then
> you have too big of an amp.
>

I am not sure what all this means as amps are fixed gain devices
they will give the same output regardless of the position of the input
attenuator
that is why it is called a input attenuator reducing reduces the signal
going INTO the amp it does
nothing to the amplification portion of the amp

By reducing the input sensitivity(the amps volume knob) one can run a
hotter sigal off the desk, improving the signal to noise ratio of the
system
but it will in no way restrict the potential of the amp
it just requires a hotter signal at the input to achive the amps rated
output

If this is what you meant to say then you are correct

if you meant that turning down the amps volume control will inhibit the
amp from reaching its rated output that would be incorrect
george

[[email protected]]

On 2003-10-21 (ScottDorsey) said:
>Hotel AV is really a thankless job. I've never done it, but I have
>had to work a lot of events in hotels and it is amazing the huge
>variation in hotel AV staff quality out there. Some really great
>folks, and some real bozos and you'll have to work with both kinds
>a lot.

DItto here. Did sound for plenty of conventions over the years and
hear some real crappy hotel house systems for these ballrooms that
break up into meeting rooms.

I built myself a mult box which took +4 down to mic level and balanced
a signal. That was so I could bring in my own mixer as we wanted more
microphones than the hotels could provide.

Last fall I was at the Hyatt near the Superdome here in NEw Orleans
for the national hurricane conference, i was there in my capacity as a
volunteer communicator. i noted that the system they had for the
meeting rooms had too little gain, and when presenters had to step
away to use an easel for presentations or run their computerized
presentations that there was no mic for them.

Have fun. Be prepared for lots of weirdness.

Get that gain on the front end as others have said. Also remember
that you'll have to interface outside equipment now and then. IN my
case not just did I need to do sound reinforcement but I also had to
record the entire proceeding so the recording secretary could do a
transcript later.

regards,



Richard Webb
Electric Spider Productions
REplace anything before the @ symbol with elspider for real email

--

[ChrisCoaster]

"Mike Dobony" > wrote in message >...

>
> Start with channel gain. Assuming you have a decent mixer, there should be
> a button called Solo, PFL, or some other designation where you can check the
> channel gain setting on the meter and ONLY that channel. "normal" peaks
> when speaking or performing should be about -6 to 0 or Unity. The more
> inputs you have the lower this gets (log10 (number of channels) * -10).
> When speaking or singing the channel should stay above -20 or the input will
> start blending into the floor noise.
>
> The channel sliders should remain between about -5 and +5. There are
> exceptions, such as changing speakers or singers. The main output also
> needs to normally run between -5 and +5db.
>
> If your sliders are set around -20 or so you will have a difficult time
> getting control over sound levels as a very small change in slider position
> makes tremendous changes in sound level. Zero or unity give you good
> control over your sound levels.
>
> Now comes the tricky part. You should run your amps at least at a half or
> there abouts and never above about 75%. If you have the gain structure done
> properly on the mixer and you need to run above 75% then you will be putting
> quite a load on the amp and you will increase distortion. If you do need to
> run above 75% then you better think seriously about either getting a bigger
> amp or additional cooling. If you are running the amp much below half then
> you have too big of an amp.
>
> You can compensate a little by fudging the mixer settings a little lower or
> higher all the way across the mixer, from gains to channel sliders to main
> output sliders. I would not center my "normal" range any lower than -10 or
> +5. Minus 10 is probably pushing it a little, but it should work okay.
>
> It is not uncommon for pros to run amps rated at twice the capacity of the
> speakers because they want the amps to be running in their sweet spot,
> usually between 50 and 75%.
>
> We are running our mains at about 50% and our monitors at about 30%. We
> really should think about replacing the monitor amps with a lower capacity
> unit, but we also expect to need more monitors in the near future so we will
> probably keep what we have.
>
> I would strongly suggest you download the Mackie manual for one of their
> SR24*4 VLZ Pro at http://mackie.com/support/downloads/manuals.html. It will
> give you the details and evidence to set it up properly.
_________________________________

Our Hotel uses 1202s and 1402VLZs - decent IMO. Respective to each
model, all channel knobs and faders are set to "U" as a matter of
course, and EQ is flat.
So I trim each input between -5 and 0, as specified before.

Output settings on the backs of these mixers have been using the "Mic"
position. If I set it to "+4", the output from the mixer will be so
hot that the "Input" and "Master" knobs on the houses cannot be set
above 9 o'clock or the feedback will be blaring.

To overcome that issue, the techs here set the house Master for the
specific room to 12, and the house input at 10 o'clock, and set the
Mackies' trims to barely light the LEDs. That results in okay house
sound, but means that if a tape deck is recording that mixer, it's rec
level must be set to 10 to record at a peak of -8dB!

Believe me, I know of better ways to do it, but I'm new at this
location and don't want to bristle the boss, knowhadImean??

-CC

[ChrisCoaster]

Bryson > wrote in message et>...
> Unless the mixer's level pots affect the bandwidth.........a lot.
>
_________________________________
Well, we uses boards from Mackie, not Milton-Bradley. : P
So bandwith is nonissue.

-CC

[S O'Neill]

ChrisCoaster wrote:

> Output settings on the backs of these mixers have been using the "Mic"
> position. If I set it to "+4", the output from the mixer will be so
> hot that the "Input" and "Master" knobs on the houses cannot be set
> above 9 o'clock or the feedback will be blaring.
>
> To overcome that issue, the techs here set the house Master for the

What issue? My control room power amp (600-watt Carver) is set at about 9:00;
that gives me 85 dBA SPL in the CR at 0 VU (+4 dBm). There's nothing wrong with
having the PA set _very_ low, to whatever it needs to be. This brings all the
other faders up to about unity, typically.

> specific room to 12, and the house input at 10 o'clock, and set the
> Mackies' trims to barely light the LEDs. That results in okay house
> sound, but means that if a tape deck is recording that mixer, it's rec
> level must be set to 10 to record at a peak of -8dB!

THIS is the issue: the symptom of turning the power amp up too high.

If you have to live with this setup you might be able to find a different output
you can turn to 11 for the tape. It'll be noisy, though.

> Believe me, I know of better ways to do it, but I'm new at this
> location and don't want to bristle the boss, knowhadImean??

I meant, THIS is the issue. :) Sounds like you have all the right suspicions,
just politix to deal with from here on.

[ScotFraser]

<< To overcome that issue, the techs here set the house Master for the
specific room to 12, and the house input at 10 o'clock, and set the
Mackies' trims to barely light the LEDs. That results in okay house
sound, but means that if a tape deck is recording that mixer, it's rec
level must be set to 10 to record at a peak of -8dB!>>

Right, so you're not getting the best signal out of the Mackie like this.
Whatever the mixer is plugged into, probably a Bogen paging system, needs to
have its input turned down so you can get a useable amount of gain through your
mixer. If the house guys refuse to do this, you can always get your signal to
the tape deck from an aux send that's cranked.

Scott Fraser

[Scott Dorsey]

In article >,
ScotFraser > wrote:
><< To overcome that issue, the techs here set the house Master for the
>specific room to 12, and the house input at 10 o'clock, and set the
>Mackies' trims to barely light the LEDs. That results in okay house
>sound, but means that if a tape deck is recording that mixer, it's rec
>level must be set to 10 to record at a peak of -8dB!>>
>
>Right, so you're not getting the best signal out of the Mackie like this.
>Whatever the mixer is plugged into, probably a Bogen paging system, needs to
>have its input turned down so you can get a useable amount of gain through your
>mixer. If the house guys refuse to do this, you can always get your signal to
>the tape deck from an aux send that's cranked.

This is why I always carry a bag of those Shure adjustable pads around with
me. They come in handy for ALL kinds of things.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[George Gleason]

> _________________________________
> Well, we uses boards from Mackie, not Milton-Bradley. : P

Is there a diffrence?
george

[Yuri T.]

Having worked more corporate AV gigs then I care to think about over
the past
> decade, I think you should bear in mind that your new boss is your new
> boss......Do it his way to start. When you get a chance to experiment at the
> end of the day, see if you can measure gain before feedback of the system using
> his method compared to your method. It's possible he may be right in the case
> of the system he is familiar with.....
>
>
> Ken Feldman
> Stranded on the Island Manhattan
> hear my songs FREE @ www.MP3.com/KenFeldman
> (did I mention that was FREE?)

And if you're really luck yyou might see if you can get some 1/3
octave EQs or feedback eliminators inserted into those
ballrooms.........hah......right.

I was lucky enough to be able to design a conference system at work.
It's a beaut. zone speaker controls with a graphic on each send.
etc...

[Mike Rivers]

In article > writes:

> What issue? My control room power amp (600-watt Carver) is set at about 9:00;
> that gives me 85 dBA SPL in the CR at 0 VU (+4 dBm). There's nothing wrong
> with
> having the PA set _very_ low, to whatever it needs to be.

Some people who don't know any better perceive this as throwing away
power.

When I do a setup with arbitrary (uncalibrated) levels, I play a CD
into the mixer, set it so that the music peaks at 0 VU on the mixer's
meter (assuming it's reading the output level, which most do), then
turn up the power amplifier's input gain (or attenuation) control so
that the music is as loud as I think I want it, then turn it up just a
little more. That gives me some headroom on the mixer for ample volume
in the room.

Any reasonable input should be able to produce the nominal output
level of the mixer (0 VU) so it all works out. This way, you get all
the voltage gain you need from the mixer where it should be, and don't
amplify the mixer's noise with the power amplifier any more than
necessary.




--
I'm really Mike Rivers - )

[George Gleason]

"Mike Rivers" > wrote in message
news:znr1066850647k@trad...
>
> In article > writes:
>
> > What issue? My control room power amp (600-watt Carver) is set at about
9:00;
> > that gives me 85 dBA SPL in the CR at 0 VU (+4 dBm). There's nothing
wrong
> > with
> > having the PA set _very_ low, to whatever it needs to be.
>
> Some people who don't know any better perceive this as throwing away
> power.
>
> When I do a setup with arbitrary (uncalibrated) levels, I play a CD
> into the mixer, set it so that the music peaks at 0 VU on the mixer's
> meter (assuming it's reading the output level, which most do), then
> turn up the power amplifier's input gain (or attenuation) control so
> that the music is as loud as I think I want it, then turn it up just a
> little more. That gives me some headroom on the mixer for ample volume
> in the room.
>
> Any reasonable input should be able to produce the nominal output
> level of the mixer (0 VU) so it all works out. This way, you get all
> the voltage gain you need from the mixer where it should be, and don't
> amplify the mixer's noise with the power amplifier any more than
> necessary.
>
This is basically what I do as well
George