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Author Topic: Aligning subs to mains  (Read 5855 times)

ThomasA(lbenberger)

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Aligning subs to mains
« on: August 09, 2004, 05:47:00 am »

Hello everyone!

As Tako Tamas has proposed in the other thread on delaying subs, I think it's worth opening another one on how to align subs properly to the mains speakers.

Assuming a pretty standard configuration for small fan-shaped venues with flown L/R mains and a center- and ground-stacked pack of subwoofers, how would you properly align one to the other?

Of special interest to me is, where you would chose to measure - basically where the points in space are - to align the subs to the tops.

Thinking about a "piece of pie" - or a segment of a circle - one can align the mains and subs to each other, so that sound arrives at the perimeter of this segment at the same time.

From a theoretical point of view and assuming we want to have the perfect alignment for the largest part of the audience possible, it would be logical to measure at the last row of the audience, since the perimeter of the segment - and therefore the number of people on this line - would be the longest there.

Practically, wall-reflections and body absorption due to the punters will make measurements at the very back of the venue close to impossible, I imagine. Also, the difference in running-time between two sound sources that are spaced apart from each other will become more insignificant with added distance.

So, where would you choose to take the measurements and delay the mains and subs to each other - first row; first third of the audience area; FOH; ??

Your insight and help on this is very much appreciated! Maybe you could also explain in how far the situation changes with a rectangular venue shape or the incorporation of a center mains cluster. I wonder if, considering the Haas-effect, it could also be worth to conciously allowe eg. the center-mains cluster to arrive first, then the L/R and last the subs, to focus the audience's attention on the center of the stage and to the vocals (assuming that the center-cluster is mostly used for vocals)

I know these are many questions at a time, but even partial enlightment would be very helpful. Razz

Thanks for sharing!

Thomas
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Thomas Albenberger

Too Tall (Curtis H. List)

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Re: Aligning subs to mains
« Reply #1 on: August 09, 2004, 09:51:25 am »

ThomasA wrote on Mon, 09 August 2004 05:47

Hello everyone!

As Tako Tamas has proposed in the other thread on delaying subs, I think it's worth opening another one on how to align subs properly to the mains speakers.

Assuming a pretty standard configuration for small fan-shaped venues with flown L/R mains and a center- and ground-stacked pack of subwoofers, how would you properly align one to the other?

Of special interest to me is, where you would chose to measure - basically where the points in space are - to align the subs to the tops.

Thinking about a "piece of pie" - or a segment of a circle - one can align the mains and subs to each other, so that sound arrives at the perimeter of this segment at the same time.

From a theoretical point of view and assuming we want to have the perfect alignment for the largest part of the audience possible, it would be logical to measure at the last row of the audience, since the perimeter of the segment - and therefore the number of people on this line - would be the longest there.



Hi Thomas,
   As it happens I don't agree with the above, but beyond that I think you would do better with this question on the LAB Classic forum. In the thread you mentioned we discussed how to marry the sub to the tops as far as phase and timing. It seems your heading toward how to align a center cluster and L/R. And before anything else look through the study hall and do some searching in the archives.
Too Tall


ThomasA wrote on Mon, 09 August 2004 05:47


Practically, wall-reflections and body absorption due to the punters will make measurements at the very back of the venue close to impossible, I imagine. Also, the difference in running-time between two sound sources that are spaced apart from each other will become more insignificant with added distance.

So, where would you choose to take the measurements and delay the mains and subs to each other - first row; first third of the audience area; FOH; ??

Your insight and help on this is very much appreciated! Maybe you could also explain in how far the situation changes with a rectangular venue shape or the incorporation of a center mains cluster. I wonder if, considering the Haas-effect, it could also be worth to conciously allowe eg. the center-mains cluster to arrive first, then the L/R and last the subs, to focus the audience's attention on the center of the stage and to the vocals (assuming that the center-cluster is mostly used for vocals)

I know these are many questions at a time, but even partial enlightment would be very helpful. Razz

Thanks for sharing!

Thomas


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Too Tall
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Mac Kerr

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Re: Aligning subs to mains
« Reply #2 on: August 11, 2004, 03:41:26 pm »

ThomasA wrote on Mon, 09 August 2004 05:47

Hello everyone!

As Tako Tamas has proposed in the other thread on delaying subs, I think it's worth opening another one on how to align subs properly to the mains speakers.

snip

From a theoretical point of view and assuming we want to have the perfect alignment for the largest part of the audience possible, it would be logical to measure at the last row of the audience, since the perimeter of the segment - and therefore the number of people on this line - would be the longest there.

Practically, wall-reflections and body absorption due to the punters will make measurements at the very back of the venue close to impossible, I imagine. Also, the difference in running-time between two sound sources that are spaced apart from each other will become more insignificant with added distance.

So, where would you choose to take the measurements and delay the mains and subs to each other - first row; first third of the audience area; FOH; ??

snip

I know these are many questions at a time, but even partial enlightment would be very helpful. Razz

Thanks for sharing!

Thomas
"From a theoretical point of view and assuming we want to have the perfect alignment for the largest part of the audience possible," it is impossible to time align a center array of subs with side stacked or flown mains.  If by "perfect alignment" you mean something less than 5ms out of time with each other at the crossover frequency it can only be done for a small portion of the audience. For audience members roughly on the centerline between the subs and the mains there is little arrival offset due to location in the room. For people near the sides of the room there is much more offset in arrival time due to different distances between the mains and the subs. The only way to time align multiple sound sources for a majority of the audience is to have them physically close together. In the case of subs there are problems associated with separating them into 2 sources and putting them physically near the mains. Because of the long wavelengths involved the comb filtering creates large areas of very uneven coverage. This is the motivation for center arrays of subs. If venue lends itself to a center array of subs, the even coverage is probably a better trade off than time alignment.

Mac Kerr
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