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Author Topic: Do marching bands have comb filtering?  (Read 11103 times)

Tim McCulloch

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Re: Do marching bands have comb filtering?
« Reply #10 on: October 23, 2014, 02:25:34 PM »

So what about "marching bands" that use electronic amplification and speaker systems?

Ban the amps... anything that needs electricity should not be on the field.  /crusty curmudgeoness
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Len Zenith Jr

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Re: Do marching bands have comb filtering?
« Reply #11 on: October 23, 2014, 03:53:52 PM »

I guess this is as good a topic as any then to ask; does a 50 foot line of say bagpipes have any line array properties? IE, narrowing of dispersion in front and behind, and carrying further to the sides?  I don't think I have ever failed to hear a scottish wedding in town.
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Jamin Lynch

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Re: Do marching bands have comb filtering?
« Reply #12 on: October 23, 2014, 03:59:26 PM »

If you have a line of accordions with some pulling and some pushing on the same note are they out of phase?  :o
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g'bye, Dick Rees

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Re: Do marching bands have comb filtering?
« Reply #13 on: October 23, 2014, 04:12:43 PM »

does a 50 foot line of say bagpipes have any line array properties?

No, but it makes a hell of a leaf blower...
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Jonathan Johnson

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Re: Do marching bands have comb filtering?
« Reply #14 on: October 24, 2014, 01:37:39 AM »

I can think of two possibilities:
  • Each instrument has a slightly different timbre, resulting in incoherency that prevents comb filtering.
  • Each instrument "tunes in" to each other via sympathetic vibration, kind of like how several metronomes on a movable platform will eventually achieve synchronicity. The instruments are wholly constructive.

This past spring I attended a choral concert by the Concordia College Choir. (Not Concordia University; Concordia College is in Moorehead, Minnesota.) During one piece, the a capella choir achieved a powerful, deep bass note that was below the normal range of the human voice. It sounded more like a bottom note of a pipe organ, but it truly was only the human voice at work, and it seemed to complement the music. I don't know if everyone in the room experienced it or if I happened to be in a "sweet spot." I suspect that it was at least partly a product of that particular room.
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Mark Cadwallader

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Re: Do marching bands have comb filtering?
« Reply #15 on: October 24, 2014, 02:12:52 AM »

I guess this is as good a topic as any then to ask; does a 50 foot line of say bagpipes have any line array properties? IE, narrowing of dispersion in front and behind, and carrying further to the sides?  I don't think I have ever failed to hear a scottish wedding in town.

In case you are serious, I suspect the answer is "no". I don't think the pipers would be standing close enough together in a line (rank) to have that effect; certainly not when lined up in a file.  The typical static formation for a pipe band playing (as in a competition) is in a circle.  Mark C.
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Frederik Rosenkjær

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Re: Do marching bands have comb filtering?
« Reply #16 on: October 24, 2014, 02:48:29 AM »

But wouldn't you have some comb filtering if you have ten trombones playing the same note? Which is often the case in a marching band. Plus all those trombones are moving across the field.

Seems like that would be the same as walking across the horn pattern of 10 speaker cabs.

As has been mentioned, they'd have to sync up in a way that's not gonna happen.

However, you will get some of the same artifacts/effects as comb filtering in brief glimpses coming and going, and that is what we commonly know as the difference in sound between a solo trombone and an ensemble. So the ensemble sound is kind of a flurry of momentary comb filtering, if you like, but the persistant static comb filtering that is usually talked about as a problem only happens with two or more coherent sources.
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Erik Jerde

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Re: Do marching bands have comb filtering?
« Reply #17 on: October 25, 2014, 01:26:31 AM »

No, like others have said.

Expanding to our field, you also won't get comb filtering if say you DI the bass left and mic it right.  Same reason, the signals are different.  They may have the same source but the DI is going to result in a different signal than the head/cab/mic combo. 

If you are running measurement and use a different noise generator for each speaker you also shouldn't get comb filtering because each signal is different from the next. 

Comb filtering is wholly an artifact of sound reproduction whereby an identical signal arrives at the same place at two different times.  This should be impossible in nature - just like you can't get comb filtering from a single driver system.

There's lots more knowledgeable people on this.  I got most of my learning on it from Dave Rat, but if I've remembered something wrong please let me know!
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Steve M Smith

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Re: Do marching bands have comb filtering?
« Reply #18 on: October 25, 2014, 04:57:22 AM »

So what about "marching bands" that use electronic amplification and speaker systems?

Why would they need it?  And how would it work if they are marching?

is this something marching bands actually do?


I got most of my learning on it from Dave Rat

I think I have learned moe in a year from watching Dave's videos than I have in thirty years of trial and error - and I'm a big fan of trial and error as you learn what doesn't work as well as what does.

Although I'm sure there's a fair amount of trial and error involved in his techniques.


Steve.
« Last Edit: October 25, 2014, 05:00:08 AM by Steve M Smith »
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Mark McFarlane

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Re: Do marching bands have comb filtering?
« Reply #19 on: October 25, 2014, 05:30:54 AM »

I guess this is as good a topic as any then to ask; does a 50 foot line of say bagpipes have any line array properties? IE, narrowing of dispersion in front and behind, and carrying further to the sides?  I don't think I have ever failed to hear a scottish wedding in town.

Yes, and no...

Up close it would be like a line array if everyone was playing the same thing exactly in sync, but it would be so loud that your ears would bleed and it wouldn't matter.  You'd have to be at least 100 meters away for a reasonable listening level, at which point the far field behavior would act more like a point source. :)
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Mark McFarlane

ProSoundWeb Community

Re: Do marching bands have comb filtering?
« Reply #19 on: October 25, 2014, 05:30:54 AM »


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