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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Dave Batistig on July 11, 2018, 11:41:05 AM
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I have been considering a couple single 18" flown subs at the top of my array (RCF HDL20, 8 hang per side), specifically for a couple amphitheater style venues where the top of the venue has a significant reduction in low end due to the subs being at ground level.
Does anyone have experience with the flown subs in general, or the RCF HDL-18AS in particular?
Thanks in advance for your help!
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Depending of the space between the flown subs and ground stacked subs you can create vertical power alley and, using delay, steer the sub lobe up/down.
You will need roughly the same output levels (within 3 dB or so) in order to do this effectively but just putting a sub at the top of the array will 'raise' the sub coverage a bit.
Experiment with it, Dave, and let us know what you find... ;)
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Depending of the space between the flown subs and ground stacked subs you can create vertical power alley and, using delay, steer the sub lobe up/down.
You will need roughly the same output levels (within 3 dB or so) in order to do this effectively but just putting a sub at the top of the array will 'raise' the sub coverage a bit.
Experiment with it, Dave, and let us know what you find... ;)
The flown sub (one per side) would be approx 19 ft off the ground, with the rest of the subs deployed on the ground across the front of the stage.
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The biggest advantage to flying the subs is you get more even coverage from front to back.
The distance to the rear does not change, so that level will stay the same.
But the distance to the front changes a good bit (in terms of dB), so it is quieter than when they are on the ground
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The down sides to flown subs is floor bounce and a little loss of impact from the subs due to time of flight. The advantages have been pretty well explained. More even coverage and easier alignment to the mains are the two big advantages. I am not a fan of flown subs unless they are on a separate hang behind, or right next to the mains. If the subs are part of the same hang as the mains, it just doesn't have the same impact and effect to me.
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Don't use it as a sub, but more of a low end extension to your array.
I have been considering a couple single 18" flown subs at the top of my array (RCF HDL20, 8 hang per side), specifically for a couple amphitheater style venues where the top of the venue has a significant reduction in low end due to the subs being at ground level.
Does anyone have experience with the flown subs in general, or the RCF HDL-18AS in particular?
Thanks in advance for your help!
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The down sides to flown subs is floor bounce and a little loss of impact from the subs due to time of flight. The advantages have been pretty well explained. More even coverage and easier alignment to the mains are the two big advantages. I am not a fan of flown subs unless they are on a separate hang behind, or right next to the mains. If the subs are part of the same hang as the mains, it just doesn't have the same impact and effect to me.
If you're used to subs on the ground and the "up close and personal" experience for the front rows (some may like, some may not), then yes there is a perceptual difference. To deliver the same SPL in whole space loading requires more acoustic output from the subwoofer pass band so that's more weight in the air and in the truck but I think it's a deployment worthy of consideration (especially with some subs on the ground, too).
Time of flight? When hung as part of (in sufficient numbers), adjacent to, or behind the main vertical array the subs have nearly the same time of flight - give or take a few, alignable ms - as the mains, to most every seat. With subs exclusively on the ground the coincidence of arrival will be different at most every seat. This is one of the reasons Ivan likes to fly subs up with the mains whenever possible. :)
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I have been considering a couple single 18" flown subs at the top of my array (RCF HDL20, 8 hang per side), specifically for a couple amphitheater style venues where the top of the venue has a significant reduction in low end due to the subs being at ground level.
Does anyone have experience with the flown subs in general, or the RCF HDL-18AS in particular?
Thanks in advance for your help!
Dave, I found with 2 d&b Q Subs on top of 6 Q1's (as a comparison) that at low levels it really added to the system (B2's on the deck) but at higher levels, you couldn't hear them (blind test muting them). So my suggestion is consider what level your running the system at as the 2 Subs may do nothing for the system if run hard.
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Dave, I found with 2 d&b Q Subs on top of 6 Q1's (as a comparison) that at low levels it really added to the system (B2's on the deck) but at higher levels, you couldn't hear them (blind test muting them). So my suggestion is consider what level your running the system at as the 2 Subs may do nothing for the system if run hard.
A couple of subs in full space (at the top of the array) will not 'keep up' with an equal or greater number of subs on the ground. Basic physics.
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I don't think anyone has directly address the full space-ness of flown subs.
The same sub on the floor is half-space and 3db louder.
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I don't think anyone has directly address the full space-ness of flown subs.
The same sub on the floor is half-space and 3db louder.
Reply #6, first paragraph.
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By TOF I meant the distance of travel and the subsequent loss in SPL associated with that. Sufficient numbers is the KEY word. If you are going to hang subs, you will need a few more than if they were ground stacked. This is why I am not a fan of systems that include subs in the same hang as the mains. There is typically not enough and they just don't come together the same.
I think it has been studied before ( and I can't remember by whom) that when it comes to subs and full space, it is of moot consideration. The problem is the locality of the listener in relation to the subs. The listener is always on a ground plane. A ground plane is an infinite baffle for all intents and purposes. This means any energy presented will load up on it. You can put subs 100' in the air and it won't matter. The sound will come down and you will hear the resultant effect of the direct and reflected sound off the ground. A small comb filter perhaps, but you will still have the effect of coupling from your vantage point. What you hear will always be 3db louder than what the actual source contributed.
I suppose if you were 100' in the air with the subs while listening to them, then you could more realistically factor the whole space sound of subs. When subs are hung they more evenly cover the area because the lobe is rounded off at the ends of the hang. This adds lots of energy in the center of the hang and it tapers off at the top and bottom. Since no one is typically above the subs, the front rows experience roughly the same output as those in the back rows who are in the direct plane of all the subs and experience the coupling of all that energy. The power alley and all the other lobing effects are still there, but with some clever beam steering and tuning, the nulls can be placed in aisles and the focus of energy can be very much directed where you want it most.
I am particular to ground stacked subs myself more because you get a little more mileage out of the subs ( don't need as many ) and you can play with arrays and deployments that can really make magic happen. I suppose the best deployment would be a combination flown sub array with some well placed and aligned ground stacked units as well. With subs there really is no magic bullet though. It is always a compromise. Ground stacked subs are just easier for the average sound provider to deal with. When you are doing large shows with real LA systems, flown subs is just the logical option.
Many LA / constant curvature systems have subs that are designed to be a part of the main hang. Just about all the vendors offer a system where subs can be integrated with the mains. These are the system types I am not fond of. It just doesn't work right to me.
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I think it has been studied before ( and I can't remember by whom) that when it comes to subs and full space, it is of moot consideration. The problem is the locality of the listener in relation to the subs. The listener is always on a ground plane. A ground plane is an infinite baffle for all intents and purposes. This means any energy presented will load up on it. You can put subs 100' in the air and it won't matter. The sound will come down and you will hear the resultant effect of the direct and reflected sound off the ground. A small comb filter perhaps, but you will still have the effect of .....
This one maybe?
https://www.fulcrum-acoustic.com/assets/pdf/whitepapers/comments-on-half-space.pdf
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Here are some screen grabs I got from Mapp XT. In the first the sub is on the floor and the mic is 20m away. In the second I moved the sub 6 meters into the air. The floor was set to be rigid and not free space.
Draw your own conclusions.
EDIT:
I added the frequency response graph of the two positions as well.
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Here are some screen grabs I got from Mapp XT. In the first the sub is on the floor and the mic is 20m away. In the second I moved the sub 6 meters into the air. The floor was set to be rigid and not free space.
Draw your own conclusions.
EDIT:
I added the frequency response graph of the two positions as well.
Can you confirm that Mapp is modeling more then just the direct sound? Most modeling programs only model just this direct sound, and for this discussion we need to include the first reflection.
Sent from my iPhone using Tapatalk Pro
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Here's a good thread from the past ... on ground vs flown
http://forums.prosoundweb.com/index.php/topic,158814.0.html
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Can you confirm that Mapp is modeling more then just the direct sound? Most modeling programs only model just this direct sound, and for this discussion we need to include the first reflection.
Sent from my iPhone using Tapatalk Pro
There is a difference in phase response and polar pattern with the boundary on and the boundary off so I am pretty sure it is compensating for the boundary in some way or another.
Someone can feel free to do some real world tests or link to such tests results if it's already been done to remove any doubt on the prediction but running into Mapp is significantly cheaper and less time consuming.
You can also very happily reproduce those results yourself, you can register for Mapp and check things out yourself.
The Mapp prediction does seem to support the theory that whether the sub half space doesn't matter unless both the listener and the speaker is in free field conditions.
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Did some more measurements in Mapp to check some stuff. Conditions this time the mic was tested 10 meters in the air and 70 meters from the sub, then place the mic on the floor and repeated. With the floor being a rigid boundary again.
Note:
The reason I am using such a long distance is to negate the effect of the inverse square law. It is obvious that the sound level between flow and on the ground will be very different 1 meter from the sub.
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More pics
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More pics
My application would be a single HDL-18AS flown at the top of the array, per side, in an attempt to deliver more low end to the top part of the amphitheater, with my full compliment of 8 SUB 8006 dual 18" subs deployed at ground level across the front of the stage. The biggest drawback I see is this would effectively lower the trim height of my top array box by the height of the sub. As it is now, my lifts are 21 ft max. The actual height of the top box is about 19.5 ft, which for this particular amphitheater works perfectly for delivering sound to the street level, where there is typically a large crowd gathered when the amphitheater itself is full.
Even being an RCF dealer, my cost on the HDL-18AS is still significant. I am not convinced that the ROI on this investment is worth it.
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Dave,
I would not find hanging a single sub in your application to be worth the effort or loss of trim. We have the inventory to hang 6/side subs and it absolutely makes a big difference in coverage when you can do it right. Typically directly behind the main array on its own rigging. And in combination with floor subs as well.
But if hanging on the same point as the mains, the loss of trim, and for us, the decrease in the number of line array boxes we can use with the subs makes the trade off not worth it.
In your case if you can put up three or four subs per side on separate lifts behind the array, great. If not, it isn't worth the hassle.
Jason
My application would be a single HDL-18AS flown at the top of the array, per side, in an attempt to deliver more low end to the top part of the amphitheater, with my full compliment of 8 SUB 8006 dual 18" subs deployed at ground level across the front of the stage. The biggest drawback I see is this would effectively lower the trim height of my top array box by the height of the sub. As it is now, my lifts are 21 ft max. The actual height of the top box is about 19.5 ft, which for this particular amphitheater works perfectly for delivering sound to the street level, where there is typically a large crowd gathered when the amphitheater itself is full.
Even being an RCF dealer, my cost on the HDL-18AS is still significant. I am not convinced that the ROI on this investment is worth it.
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Dave,
I would not find hanging a single sub in your application to be worth the effort or loss of trim. We have the inventory to hang 6/side subs and it absolutely makes a big difference in coverage when you can do it right. Typically directly behind the main array on its own rigging. And in combination with floor subs as well.
But if hanging on the same point as the mains, the loss of trim, and for us, the decrease in the number of line array boxes we can use with the subs makes the trade off not worth it.
In your case if you can put up three or four subs per side on separate lifts behind the array, great. If not, it isn't worth the hassle.
Jason
Agreed with what Jason said.
We have added a couple of subs to the top of the main hang on occasion, but it was in arena situations where we didn't have to sacrifice trim height. I once tried it in a similar situation where we had limited trim height and deemed it counter productive at best.
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Agreed as well. For you application adding 1 sub to the array is not going to give you much benefit.
I posted the additional information because this is a forum and people will hopefully search before posting and then find the information.
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Agreed with what Jason said.
We have added a couple of subs to the top of the main hang on occasion, but it was in arena situations where we didn't have to sacrifice trim height. I once tried it in a similar situation where we had limited trim height and deemed it counter productive at best.
I added the flown sub to my Ease Focus model I already had for this venue and while on paper in indicates there would be somewhat of a boost in low end coverage in the upper part of the venue, the drawbacks greatly outweigh any potential small benefit. Not going to be making this investment!
I really appreciate all the helpful feedback to this post!
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Don't let some people on the internet put you off of trying something that might be a learning experience either.
If the prediction says it will be an improvement and you can do it without needing to shade the bottom of your array too much(as you know amplitude shading can cause weird phase anomalies if done aggressively) then I say go for it. If you need extra boxes to do that maybe rent as a 1 time thing to test it and if you like it then make the investment.
I didn't think adding 1 sub to the array would actually make a difference though.
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Another option if your PA is up to the task, is running the PA full-range and put the subs on an aux.
Had a system like that last night, it was a really sweet-sounding Meyer Mica system outdoors with a good systech.
Sounded really good and easy to mix on.
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I added the flown sub to my Ease Focus model I already had for this venue and while on paper in indicates there would be somewhat of a boost in low end coverage in the upper part of the venue, the drawbacks greatly outweigh any potential small benefit. Not going to be making this investment!
I really appreciate all the helpful feedback to this post!
Dave, I think you're making the correct choice. I recently dialed in a small theater with a d&b q install with 6 Q1/side and 1 Q-sub/side at the top (a q-sub is a single 18"). Also, 1 B2 (band pass double 18) per side on the floor under the stage. There is a small balcony in this venue. The Q-subs did nothing perceptible for the balcony. What they did do was was blur the power alley from the B2's on the floor. Without the q-subs, the power alley was more prominent, and the low end was clearer. With the Q-subs on, the power alley was less prominent and the low end was blurrier in general. Neither was clearly superior and I wouldn't fault an engineer from wanting it either way. But if your objective is a longer "throw" for sub, I don't think augmenting ground subs with a single 18 box at the top of the array will get you there.
I didn't catch your configuration for your ground stacked subs, but another thing to think about is: the shallower your sub stack is vertically, the higher it will cover vertically. I've measured this in large theater's double balconies before and it is perceivable. A single high sub stack (i.e. 24" high box) covers the balconies better than double high (i.e. 48" high). Of course you are covering the ceiling better too. If you stack 3 high, the top sub is pretty much just for the floor.
-xandy
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I always thought this was a good take on flown subs, especially dealing with venues that have seating above ground level:
https://www.ratsound.com/cblog/archives/334-Figuring-and-Flying.html (https://www.ratsound.com/cblog/archives/334-Figuring-and-Flying.html)
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I always thought this was a good take on flown subs, especially dealing with venues that have seating above ground level:
https://www.ratsound.com/cblog/archives/334-Figuring-and-Flying.html (https://www.ratsound.com/cblog/archives/334-Figuring-and-Flying.html)
For sure. His blogs are an awesome sharing IMO.