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Author Topic: Awkward Sub placement options  (Read 1952 times)

Ivan Beaver

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Re: Awkward Sub placement options
« Reply #10 on: January 01, 2020, 02:39:26 pm »

Power alley is not "dreaded" except by those who ran out of other legitimate concerns to occupy their time.  Is it ideal?  No, but neither are the alternatives.  ALL subwoofer placements are a compromise unless flown next to the PA, and there are still trade-offs.

My advice is "get over it" and go do the show, cash the cheque and move on.
EXACTLY

Very often people get "hung up" on one particular aspect, and completely ignore the other actual things that are happening.

But as long as they focus on what seems most important to them, they can try to justify the means.

This goes for much more than just subs and audio however.

It often amazes me how "hung up" people get on one little thing, when there are much bigger issues to be dealt with.
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Tim McCulloch

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Re: Awkward Sub placement options
« Reply #11 on: January 01, 2020, 04:49:28 pm »

I too have been thinking about the power alley issue.  I may just go with stacking two subs on each side of the stage, buy use aux fed subs to control them?  Would there be any advantage to point one sub from each stack a bit towards the center of the dance floor?

On another issue.  If using aux fed subs, I may place high pass and low pass filters on the mains and the subs.  Is there a need for this, is so, where should I set each of these?  I'm currently sending the kick, floor tom, keys, bass, tenor sax and trombone to the subs.

Am I missing anything?

Pointing subs?  Individual subs do not matter as they're largely omni-directional within their operating range.  What makes a difference is distance between subs (determines what freq power alley will center at) and distance from a sub to any solid boundary surface (reflections of 1/2 wave length will create a cancellation).  Example - if you have a sub 4ish ft from a wall, the reflection will create a cancellation around 80Hz.  Moving the sub further from the wall will lower the frequency of cancellation.  Peavey's now-retired clinician Marty McCann's rule of thumb was "less than 2 feet or more tham 7 feet) from a solid boundary.  You can do the math and see why... :)

Which instruments?  I'd drop the tenor sax (lowest note plays at Bb2, or 116Hz) and trombone for most players is an octave below that sax, or about 58Hz.  Whether or not you need the 'bone in the sub is a matter of program material and artistic decision making; I've only put bass trombone in the subs (symphony gig); typically I'm mixing Motown/Memphis style horn sections and "rumble" from the 'bone isn't desired and seldom does the horn have a part that low in the chart.
« Last Edit: January 01, 2020, 04:52:09 pm by Tim McCulloch »
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Luke Geis

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Re: Awkward Sub placement options
« Reply #12 on: January 01, 2020, 05:37:25 pm »

I guess I fall into one of those who are hung up on the power alley thing. I just prefer a more even sounding sub-content as I move around the venue. That is not to say I am stuck on stupid with it though. It is very situational for me and I will do whatever makes the most sense given the venue, my goals and client criteria.

With subs, there is truly no 1 correct way, as no matter how you set them up it will have some amount of compromise. Getting the best results with the least compromise is the goal. For me, broad coverage is less desirable than even/smooth coverage. So clustered subs or other clever arrays are usually what I will employ. For me, having good sub-content outside of my desired listening area goes against best practices. Most stereo deployed systems will have plenty of 360* low-end coverage well beyond where the speakers are pointed along with the power alley and other comb filtering. With a center cluster of subs, there is a small disconnect between the mains and the subs, but with careful tuning and a center fill, the PA can be tied back together acceptably and the coverage within the desired listening area is smoothed out and lower in level at regions that are beyond the desired space. To me, it is the lesser of two evils if and only if it makes sense to deploy it that way.

There are upsides to stereo deployed subs too though. One being broader coverage. Another would be integration with the main PA. Because it is closer to the mains, it will tune better and be more in line with what people expect from any given sound system. There is a point that this falls apart though. The areas of cancellations can be big enough that walking into them will leave you with NO SUB CONTENT AT ALL, and that is not a good thing. So it comes down to need, practicality and goals.

One of the home theater remedies for dealing with subs and comb filtering is to simply inundate the room with subs or placing them physically closer to the different listening positions. The concept is that while the phase issues will be there, the content is evident with enough impact to be of little issue. If you don't have enough sub content while sitting in the right outside seat, just put another sub next to it.
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Tim McCulloch

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Re: Awkward Sub placement options
« Reply #13 on: January 01, 2020, 07:16:51 pm »

I guess I fall into one of those who are hung up on the power alley thing. I just prefer a more even sounding sub-content as I move around the venue. That is not to say I am stuck on stupid with it though. It is very situational for me and I will do whatever makes the most sense given the venue, my goals and client criteria.

With subs, there is truly no 1 correct way, as no matter how you set them up it will have some amount of compromise. Getting the best results with the least compromise is the goal. For me, broad coverage is less desirable than even/smooth coverage. So clustered subs or other clever arrays are usually what I will employ. For me, having good sub-content outside of my desired listening area goes against best practices. Most stereo deployed systems will have plenty of 360* low-end coverage well beyond where the speakers are pointed along with the power alley and other comb filtering. With a center cluster of subs, there is a small disconnect between the mains and the subs, but with careful tuning and a center fill, the PA can be tied back together acceptably and the coverage within the desired listening area is smoothed out and lower in level at regions that are beyond the desired space. To me, it is the lesser of two evils if and only if it makes sense to deploy it that way.

There are upsides to stereo deployed subs too though. One being broader coverage. Another would be integration with the main PA. Because it is closer to the mains, it will tune better and be more in line with what people expect from any given sound system. There is a point that this falls apart though. The areas of cancellations can be big enough that walking into them will leave you with NO SUB CONTENT AT ALL, and that is not a good thing. So it comes down to need, practicality and goals.

One of the home theater remedies for dealing with subs and comb filtering is to simply inundate the room with subs or placing them physically closer to the different listening positions. The concept is that while the phase issues will be there, the content is evident with enough impact to be of little issue. If you don't have enough sub content while sitting in the right outside seat, just put another sub next to it.

Get therapy, Luke!   ;D

Sub placement is typically a collection of compromises.  The lovely Round Mound of Sound that is one of our venues presents a number of challenges to *promoter* needs, and a delay-arc array across the front of the stage, while sounding even and avoiding side spill, pushes barricade almost 9 ft into the crowd, compared to placing subs under the PA and going off-stage as more are deployed.  Optimum?  No, but the promoter would be justifiably unhappy if I took 250 pax off his gross potential because I took the space off the floor plan.  Every stakeholder is affected if capacity is lowered:  venue, merch sales, concessions/food & beverage, valet parking, promoter, bands, caterers... And it would dump a fair bit of sub energy directly onto or under the stage.  In that room, L/R deployment makes the most "average" sense.

I've done several different sub deployments in a variety of venues, and for different reasons... and for the most part none of them were selected because *I* wanted it done the way it was done.  It's a service biz, and if the Brother at the piano is getting his ass shaken by the subs we're gonna fix that no matter what it does to PA/sub alignment, or the Stomach Steinway guy who really, really doesn't like to feel any additional low end on stage, anywhere.  We can, and should, discuss subwoofer deployment - and hopefully those playing along at home will do some physical/audible exercises and experiments to verify what we say - because the more tools at our disposal, the more useful we become.

Alignment between physically separated pass bands is pretty much a "who's our lucky winner?" question since we can align for only one place.  Moving in any direction changes the distance between pass bands and listener.  For the lucky winner with the seat in that spot, it's probably awesome but everyone else cannot and will not get an identical experience; so how much time and effort goes into working with sub/top alignment for the Sacred Spot, when more beneficial might be better front fill and side hang alignment?





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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mark Norgren

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Re: Awkward Sub placement options
« Reply #14 on: January 02, 2020, 08:37:14 am »

I really appreciate this discussion.  I own four KW181's.  Usually I will stack two subs on each side and stick a KW153 on top of the two subs.  In smaller rooms I usually bring only two subs and don't have a real problem.  I have a gig coming up and there are a few places that are larger rooms when I bring all four subs.  I have tried the cardioid setup and that really didn't seem to make a big difference.  The more I listen, I think I will just go back to aux fed, two on each side?  The 153's have 15's in them and will fill in a bit to a point.  I have to get real and know this is not the Super Bowl Halftime show!  Most people will not even care or notice any difference unless there is another issue with just the general mix of instruments.  Just Relax Grasshopper!
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John L Nobile

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Re: Awkward Sub placement options
« Reply #15 on: January 02, 2020, 10:32:37 am »

I've tried a few different things over the years and I always go back to L/R subs. No one ever complains and they get the job done.

My preference is center, understage endfire or side by side subs. But the latter kills the people out front and I've had complaints from the bands on both. Too much bass on stage.

Bottom line is that I don't have time to move subs during soundcheck and I wasted time lining things up. Go with what you know will work.
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Luke Geis

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Re: Awkward Sub placement options
« Reply #16 on: January 02, 2020, 03:29:35 pm »

Cardioid sub deployment has a couple of requirements in order to work well. With two subs it technically should have higher degrees of cancellation, but that cancellation occurs at a 45* angle from the face of the stack. The direction of that cancellation is dependent upon which side the rear-facing sub is placed. While doing a stacked cardioid sub-array would seem to solve that problem, it does not. Keep in mind that if you have the 45* cancellation going upwards, the primary amount of energy will bounce off the floor rendering your hard work useless. To make a vertically stacked cardioid array work well with only two subs, you have to have the 45* angle of cancellation point down from the back of your stack. This reduces the floor bounce ( to the degree that it can ) and shoots the energy more upwards towards the listeners. As with all sub-arrays, there is nothing without compromise.
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Tim McCulloch

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Re: Awkward Sub placement options
« Reply #17 on: January 02, 2020, 04:02:51 pm »

Cardioid sub deployment has a couple of requirements in order to work well. With two subs it technically should have higher degrees of cancellation, but that cancellation occurs at a 45* angle from the face of the stack. The direction of that cancellation is dependent upon which side the rear-facing sub is placed. While doing a stacked cardioid sub-array would seem to solve that problem, it does not. Keep in mind that if you have the 45* cancellation going upwards, the primary amount of energy will bounce off the floor rendering your hard work useless. To make a vertically stacked cardioid array work well with only two subs, you have to have the 45* angle of cancellation point down from the back of your stack. This reduces the floor bounce ( to the degree that it can ) and shoots the energy more upwards towards the listeners. As with all sub-arrays, there is nothing without compromise.

After the first source, every additional source of sound can simultaneously help a little in one place and make it worse somewhere else.  It's picking where those 2 things occur.  I've put some really crappy sound in the middle of a aisle and the folks seated on either side got good audio, but you wouldn't think so as you went to your seat.

As for reversed box, polarity flipped and delayed cardioid deployments, I vastly prefer my subs standing on end, block of 3, with the center box reversed.  You get identical floor bounce and boundary mirroring that way.  If I have to go horizontal, I want the bottom box be the reversed sub.  Depending on how it sounds I may shade down the reversed sub a bit (not over -3dB) and take a little less cancellation at center tuning.  This issue is the way the forward facing subs couple, and the time of flight difference.  I think Merlijn Van Veen has some really great articles and a couple of videos about this.

Edit PS:  I went looking for the Merlijn article and can't find it, perhaps it was Timo Beckman?
« Last Edit: January 02, 2020, 04:16:14 pm by Tim McCulloch »
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Ivan Beaver

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Re: Awkward Sub placement options
« Reply #18 on: January 02, 2020, 07:15:10 pm »

I guess I fall into one of those who are hung up on the power alley thing. I just prefer a more even sounding sub-content as I move around the venue.
The problem is that unless you are in a VERY LARGE room, the ROOM will be the dominating factor.  It is called room modes, which are based on the physical dimensions of the room.

Try this little test sometime.  Just use a single sub for best effect.

Put a pure tone in, say 60Hz.  Not loud, but enough to be heard.  Now walk around the room.  You will find places that are much louder and quieter than others.  Make a not of those spots, specifically the dead ones.

Now choose another freq, that does not have a easy submultiple of the first tone.  Say 49Hz. or 79 Hz.

Now walk around again, and you will see that the hot spots and quiet spots have moved around.

So what are you going to do to get "even sub coverage".  Don't EVEN think about touching an EQ.

Short of tearing down the walls and ceiling, not much you can do.  The closest thing you can do is to put the sub in a corner so that you will excite more room modes.  But usually a corner is not near the front of the stage, so there is that to consider.

But let's go outside, while subs in the center may not have the cancellations of L/R subs, there are more issues to consider.  First of all is all of the energy on the stage.  Next it depends on what you call "even coverage".  The people in the center will be much louder than those off to the sides.  that is not "even" if you ask me.  You may not have the finger lobes, but you do have very different SPL levels, and the same SPL is what I call "even coverage"
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Luke Geis

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Re: Awkward Sub placement options
« Reply #19 on: January 02, 2020, 08:52:04 pm »

So in short, it's a lose lose deal. Fingering ( comb filtering ) is not even, and SPL that is slightly off is not even, so neither wins. Front fills can be used to reduce disparity in SPL in the middle in either situation, so none is the leader there either. And because the zone of highest coupling occurs in the center with stereo deployed subs ( ala power alley ) you have again uneven SPL if no front fills are used for the near field listeners.

It's 6 to one 12 the other with subs. Which deployment has the least compromise given the situation is the one to go with. I am agnostic to deployment type, I just don't settle on stereo deployment as being what is a standard.
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Re: Awkward Sub placement options
« Reply #19 on: January 02, 2020, 08:52:04 pm »


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