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Author Topic: Horrible combing at a gig  (Read 1205 times)

George Reiswig

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Re: Horrible combing at a gig
« Reply #10 on: June 13, 2024, 11:45:52 AM »

In this case, might it be better to place both subs on one side of the stage, so they arenít obstructing the performers?
« Last Edit: June 13, 2024, 07:47:09 PM by George Reiswig »
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Tim McCulloch

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Re: Horrible combing at a gig
« Reply #11 on: June 13, 2024, 12:39:50 PM »

Frank, kudos with recognizing mistakes!  It makes it easier to see possible solutions.

The K10 speakers side by side were the cause of the comb-filtering.  QSC shows the K10 as an 90deg. axisymetric cabinet, which more than likely added to the heavy comb-filtering problem.  Adding more point-source speakers to FOH (to produce more volume) will cause more issues.  Adding point-source speakers to FOH should really only be for providing additional coverage.  With a proper splay of the speakers, coverage can be greatly improved (along with a reduction in comb-filtering), but do not expect an increase in FOH volume.  You mentioned you had a slight splay in your setup; a larger splay (~45deg with the K10s) would probably be a good place to start; maybe toe-in the inside speakers to cover more at the front of the stage.

The subs being spaced 35ft. apart produced a lot of power-ally, while at the same time, probably produced very minimal (and none in some areas) of bass for half of the audience coverage.  Keeping the subs spread apart with the top cabinets does not do well.  Placing the subs in the center (even in front of the band), may not look good, but the results (in my opinion) far out weigh the image of the sound system setup.  I always place subs in the center.  It provides much better coverage (the entire audience area will hear and feel the bass), and eliminates the power-ally.  Don't worry too much how it looks... the results are worth it.

For your setup, if you need a louder a FOH PA, you will need to use either more efficient speakers, or more powerful speakers, or use line-array modules and add cabinets as needed.  The use of trap boxes does not (most of the time) indicate those speakers can be splayed side by side (based on their physical design).  Many trap boxes still need to be splayed correctly (most of the time, based on the coverage of the horn).

In your "Coming up:" comments, I would recommend the use of a center-fill (assuming the 35ft. stage width).  The center-fill just needs to cover the first few rows; it does not need to be as loud as the main PA; it can actually be a lot lower in volume; this will have minimal impact on the main FOH PA.

"Fixing" power alley with center clustering of subs creates other problems.  The trade offs may be worth it, or not.  IMNSHO, subwoofer power alley is the least of various coverage issues presented by most venue architecture and/or sound system deployments but a surprising (to me, anyway) mixerpersons think this is the hill to die on; perhaps they work for a performer for whom power alley is a fetish, and they're just trying to make the boss happy.  I'd worry more about having a mix that uniformly covers all audience areas in the "money" range of 100-12(ish) kHz.  I'd worry more about presenting a mix where all the players can be heard, where the vocals are intelligible, and where the folks in the middle of coverage of 2 loudspeakers are not subjected to appalling combing.
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Helge A Bentsen

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Re: Horrible combing at a gig
« Reply #12 on: June 13, 2024, 02:56:03 PM »

"Fixing" power alley with center clustering of subs creates other problems.  The trade offs may be worth it, or not.  IMNSHO, subwoofer power alley is the least of various coverage issues presented by most venue architecture and/or sound system deployments but a surprising (to me, anyway) mixerpersons think this is the hill to die on; perhaps they work for a performer for whom power alley is a fetish, and they're just trying to make the boss happy.  I'd worry more about having a mix that uniformly covers all audience areas in the "money" range of 100-12(ish) kHz.  I'd worry more about presenting a mix where all the players can be heard, where the vocals are intelligible, and where the folks in the middle of coverage of 2 loudspeakers are not subjected to appalling combing.

I made a power alley today, because it was the best solution for a festival.
Audience areas starts 2m from stage, far end is 45m away and 9m above on top of a hill. I could have done a line of subs in front of the stage, but the variation in low end between the closest and most distant listener would have been terrible.
So I flew the subs L/R outside of the PA and the low end turned out pretty good.
I had A LOT more issues with the mesh in front of the PA.......
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Kevin Maxwell

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Re: Horrible combing at a gig
« Reply #13 on: June 13, 2024, 03:33:19 PM »

Frank - Have you ever heard of the Dual PA Method?

The dual PA method for you would be to put 2 speakers on each side of the stage and flat front them. Feed one on each side only the instruments and the other one on each side only the vocals. This can work great if all you need is the maximum horizontal coverage that you get with one speaker a side.

The first time I did a dual PA setup I was expected to use 2 speakers aside in a room that was capable of being covered with one a side because the dispersion was wide enough. And the room was only about 900 seats with a balcony but no under balcony. My solution was to do the dual PA trick and I loved it.
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duane massey

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Re: Horrible combing at a gig
« Reply #14 on: June 13, 2024, 05:40:17 PM »

This thread reminded me of where we were in the 70's and 80's vs where we are now. Damn, I'm old......
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Duane Massey
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Martin Morris

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Re: Horrible combing at a gig
« Reply #15 on: June 13, 2024, 08:25:40 PM »

Frank - Have you ever heard of the Dual PA Method?

The dual PA method for you would be to put 2 speakers on each side of the stage and flat front them. Feed one on each side only the instruments and the other one on each side only the vocals. This can work great if all you need is the maximum horizontal coverage that you get with one speaker a side.

The first time I did a dual PA setup I was expected to use 2 speakers aside in a room that was capable of being covered with one a side because the dispersion was wide enough. And the room was only about 900 seats with a balcony but no under balcony. My solution was to do the dual PA trick and I loved it.


While this will  sound better and be louder, another option is one speaker a side facing forward and splayed infill with the 2nd speaker- the infills can be feed independently from a separate send, but they are 6 dB ish down in level. If extra amps and sends aren't an option, make a NL4 lead thats looped out of the main box but the lead PADS the signal down. Physically moving the infill speaker back (in time) if there's space to do this. Same as below, pink noise and walk the area while somebody moves the speaker. An analyser is revealing for the area of overlap and sure there are compromises.

The best option is uncorrelated signals sent to both speakers ... separate send but slightly different mix to each.

With the separate send option for the infills, a millisecond or two of delay on the infill will help. Pink noise and walk the overlap area. The delay will move the combing effect - adjust the delay to migrate the combing away from worst effected response  - level attenuation is you friend here too!



Dual PA is the winner.

Dave Rat - uncorrelated pink noise - its a great watch.

https://youtu.be/VHjdh-Vka-g?si=umTQuTwVT56tzjWA

Cheers
Martin
« Last Edit: June 13, 2024, 09:29:11 PM by Martin Morris »
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Re: Horrible combing at a gig
¬ę Reply #15 on: June 13, 2024, 08:25:40 PM ¬Ľ


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