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XTi Band Manager Gain structure


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#1 glenn0

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Posted 24 May 2011 - 07:46 AM

Running Mackie 24/4 Onyx board, 2 XTi4000 in bridge mode and 1 XTi6000 in Stereo.  Main cabinets are EAW LA128z (, xti4000 dual 18) and LA460 tops (xti6000).  Using Band Manager.

When trying to set up the gain structure, I has massive clipping of the input gain.  I cannot get my board faders anywhere near unity without horribly clipping the input gains with lots of distortion.  I compensate by keeping the board faders no greater than -20db then hitting the xover gains in bandmanager by 10db.  This is very undesirable but dont know what else to do!!!!

How do I balance the gains so that I can operate my board near unity without massively clipping the XTi's input gains????

#2 Kevin Heber

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Posted 24 May 2011 - 08:04 AM

Something in the setup seems wrong...the Mackie board's maximum output according to spec is +21dBu and the XTi's max input is +22dBu.

Can you measure the board output at 0dB (on the main out meter) on a sine wave test signal with a multimeter?  You can measure between pin 1 and 2, or pin 1 and 3 on the XLR.  You should get 0.7 to 0.8 Vrms.

#3 glenn0

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Posted 24 May 2011 - 08:11 AM

QUOTE(Kevin Heber @ May 24 2011, 09:04 AM) View Post
Something in the setup seems wrong...the Mackie board's maximum output according to spec is +21dBu and the XTi's max input is +22dBu.

Can you measure the board output at 0dB (on the main out meter) on a sine wave test signal with a multimeter?  You can measure between pin 1 and 2, or pin 1 and 3 on the XLR.  You should get 0.7 to 0.8 Vrms.



Hi Kevin, glad I got you.  I know, keep thinking I am doing something stupid, but I dont know what it is??  I dont have the ability to do this right now, no sine wave generator.  What I have done in the past to set gain structure is to run pink noise into a chanel, set the board channel gains until I am just cliping then adjust all of the gains in the signal chain until they were just clipping and thus have a more-or-less gain balanced system.  When I try to do this, I just red-line the input indicators on bandmanager, and presumably the amps (all of them).  

Could this be an inout sensitivity setting issue??

#4 Kevin Heber

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Posted 24 May 2011 - 09:13 AM

I would probably use something more aggressive than pink noise to set gains/clipping points, because you never want the board to clip, but I still don't think that's the problem.

Input sensitivity is set by the knobs on the front, which come after the meters.  

If you run pink noise through the board and set it so the MAIN MIX meters are at 0dB, this should equal +4dBu out of the board.  This is well below input clipping (approx -18dB).   At this level, with the input knobs all the way up, the output should be just clipping.  What happens when you try this on the input and output meters?

#5 glenn0

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Posted 24 May 2011 - 09:42 AM

QUOTE(Kevin Heber @ May 24 2011, 10:13 AM) View Post
I would probably use something more aggressive than pink noise to set gains/clipping points, because you never want the board to clip, but I still don't think that's the problem.

Input sensitivity is set by the knobs on the front, which come after the meters.  

If you run pink noise through the board and set it so the MAIN MIX meters are at 0dB, this should equal +4dBu out of the board.  This is well below input clipping (approx -18dB).   At this level, with the input knobs all the way up, the output should be just clipping.  What happens when you try this on the input and output meters?



OK I'll try that, but I am fairly sure that the input meters will be redlined, but I will run the experiment to be sure.  Will take me a few days as I have to get into the truck and dig this stuff out.  Is this forum the best way to continue the dialog with you??

#6 Kevin Heber

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Posted 24 May 2011 - 11:19 AM

OK, thanks.  Sounds good -- we can keep this on the forum if OK with you.  If you don't get a timely response feel free to ping me at kevin.heber@harman.com

#7 soundguygb

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Posted 24 May 2011 - 10:34 PM

QUOTE(glenn0 @ May 24 2011, 08:11 AM) View Post
QUOTE(Kevin Heber @ May 24 2011, 09:04 AM) View Post
Something in the setup seems wrong...the Mackie board's maximum output according to spec is +21dBu and the XTi's max input is +22dBu.

Can you measure the board output at 0dB (on the main out meter) on a sine wave test signal with a multimeter?  You can measure between pin 1 and 2, or pin 1 and 3 on the XLR.  You should get 0.7 to 0.8 Vrms.



Hi Kevin, glad I got you.  I know, keep thinking I am doing something stupid, but I dont know what it is??  I dont have the ability to do this right now, no sine wave generator.  What I have done in the past to set gain structure is to run pink noise into a chanel, set the board channel gains until I am just cliping then adjust all of the gains in the signal chain until they were just clipping and thus have a more-or-less gain balanced system.  When I try to do this, I just red-line the input indicators on bandmanager, and presumably the amps (all of them).  

Could this be an inout sensitivity setting issue??


Setting all of your channel gains to just below clip is why you can't push your master to unity without clipping. Try setting the channel gains to were they just start to flicker the +3 light on the meter. You should be able to run at unity with no issues. You'll probably find that your mix will sound better as well.

#8 glenn0

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Posted 25 May 2011 - 06:27 AM

QUOTE(soundguygb @ May 24 2011, 11:34 PM) View Post
QUOTE(glenn0 @ May 24 2011, 08:11 AM) View Post
QUOTE(Kevin Heber @ May 24 2011, 09:04 AM) View Post
Something in the setup seems wrong...the Mackie board's maximum output according to spec is +21dBu and the XTi's max input is +22dBu.

Can you measure the board output at 0dB (on the main out meter) on a sine wave test signal with a multimeter?  You can measure between pin 1 and 2, or pin 1 and 3 on the XLR.  You should get 0.7 to 0.8 Vrms.



Hi Kevin, glad I got you.  I know, keep thinking I am doing something stupid, but I dont know what it is??  I dont have the ability to do this right now, no sine wave generator.  What I have done in the past to set gain structure is to run pink noise into a chanel, set the board channel gains until I am just cliping then adjust all of the gains in the signal chain until they were just clipping and thus have a more-or-less gain balanced system.  When I try to do this, I just red-line the input indicators on bandmanager, and presumably the amps (all of them).  

Could this be an inout sensitivity setting issue??


Setting all of your channel gains to just below clip is why you can't push your master to unity without clipping. Try setting the channel gains to were they just start to flicker the +3 light on the meter. You should be able to run at unity with no issues. You'll probably find that your mix will sound better as well.


Only setting the gains just below clip for calibration.  During performance we are well below clipping any of the channels/components, except for the input gains on the amps, very odd.  Still think I am doing something stupid and havent realized it yet!!!


#9 glenn0

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Posted 21 June 2011 - 08:20 PM

Hey Kevin, had a bunch of gigs using a house pa, finally got back to your suggestions.  You know I used to think I knew what I was doing but man I am not so sure anymore, hope you can help.

Recall  I am using the following
1 Xti 6000 in stereo into 2 EAW LA640's
2 Xti4000's bridged one each into 2 EAW LA 118z's (i think, 2 18's/cabinet anyway)
Bandmanager
Mackie 24x4 onyx board

1.  I am assuming that I want the input and output meters in BandManager to somewhat match on all 3 amps with pink noise.  Meaning that when the input is 2 bars into the yellow, so should the output bars.
2.  As you suggested I ran pink noise into my board and made sure the output meters read 0 db.  Bandmanager input meters on all three amps was about 2 bars into the red.
3.  Under these conditions, XTI 6000 output meters in BandManager (amp knobs on full) reads 2-3 yellow bars while the XTI 4000 output meters in BandManager (amp knobs on full) reads very low, only 2 bars in green.  Have to boost crossover gains (set at 20 and 85 hz)  12 db to get output and inputs to somewhat match (2 bars into yellow, like the Xti6000).  Is this because I am using pink noise as my source or is this OK??  Twelve db boost seems just crazy.

I feel humbled, I thought I knew what I was doing but obviously there are some things here I do not understand, I would greatly appreciate any help in how I balance this system so I protect and get the maximum performance out of my equipment.

Glenn

#10 Kevin Heber

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Posted 22 June 2011 - 03:59 PM

I would calibrate the gains on the DSP OFF preset first, then apply crossovers / bridge mode.  If you are getting level differences after that, it's because of the crossover and that's OK.  Boosting the bandpass gain will also boost noise, so that's not always a good idea.

Input meters can run a little under the output meters.  Since you never want to clip the input, you can leave a buffer there.

As long as your mixer is running consistently close to 0dB and the amps do not clip too often or at all, your gain staging is fine.





#11 fantom

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Posted 11 March 2012 - 01:01 PM

Hi. I had a similar problem with my xtis not too long ago. We ended figuring out it was a power issue. Ac clipping is reflected on the input meters and your output meters will not show you the performance your looking for in other words you output meters say you got way more to go before clipping yet your input meters are clipping like crazy.

So make sure you have adequate power especially for the bridge mono amps. I try to keep each pair of my xti 4000 on one 30 amp breaker. Now the breaker will not limit power if it's smaller than 30 amp it will just jump if you exceed what ever the rating is. So the interesting and probably more important part is how you cable the amps to ac power.

If your using extension cords make sure you got atleast 12awg cable this is where lots of power can be lost. I would only put 2 amps on one 12awg cable. If your going long distances make sure you compensate for that with thicker cable.

Becareful if you plug more than 2 amps to one extension cord. Remember most 120v receptacles are rated at 20 amps max and some are 15 amp. So if you plug in several amps to maybe a 4 way splitter and then have a decently thick extension cord (say 10awg) when you connect that cord to your power distro or the wall you still plugging into (1) 120v plug that's only rated for 20 amps. Remember your xtis draw about 10 amps each (xti 6000 slightly more) at 1/8th power pink noise.

I was helped by a member of crown's staff here on the forum and the real test was plugging the amps straight to the distro. With 1 amp per plug. It made the world of difference. Now inputs are not peaking with ac peaks.

Of coarse we can't always have our amps by the distro so when the need comes to have the power amps far from the distro lots of thought has to go into how you get the ac power flowing to your amps. ie thicker cables, more cables and be careful how much you load on each receptacle in all parts of the ac power chain.

#12 dakos

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Posted 16 March 2012 - 04:24 AM

QUOTE(fantom @ Mar 11 2012, 01:01 PM) View Post
Hi. I had a similar problem with my xtis not too long ago. We ended figuring out it was a power issue. Ac clipping is reflected on the input meters and your output meters will not show you the performance your looking for in other words you output meters say you got way more to go before clipping yet your input meters are clipping like crazy.

So make sure you have adequate power especially for the bridge mono amps. I try to keep each pair of my xti 4000 on one 30 amp breaker. Now the breaker will not limit power if it's smaller than 30 amp it will just jump if you exceed what ever the rating is. So the interesting and probably more important part is how you cable the amps to ac power.

If your using extension cords make sure you got atleast 12awg cable this is where lots of power can be lost. I would only put 2 amps on one 12awg cable. If your going long distances make sure you compensate for that with thicker cable.

Becareful if you plug more than 2 amps to one extension cord. Remember most 120v receptacles are rated at 20 amps max and some are 15 amp. So if you plug in several amps to maybe a 4 way splitter and then have a decently thick extension cord (say 10awg) when you connect that cord to your power distro or the wall you still plugging into (1) 120v plug that's only rated for 20 amps. Remember your xtis draw about 10 amps each (xti 6000 slightly more) at 1/8th power pink noise.

I was helped by a member of crown's staff here on the forum and the real test was plugging the amps straight to the distro. With 1 amp per plug. It made the world of difference. Now inputs are not peaking with ac peaks.

Of coarse we can't always have our amps by the distro so when the need comes to have the power amps far from the distro lots of thought has to go into how you get the ac power flowing to your amps. ie thicker cables, more cables and be careful how much you load on each receptacle in all parts of the ac power chain.

Extremely valuable knowledge,
Thank you