Mirror image line array

G

Greg Huber

Freshman
Jul 4, 2013
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Hi all -

I work at a club with an installed line array. The cabinets are non-symmetrical (6" MF on the left, HF in the middle, 12" LF on the right when viewed from the front.)

The install was flown so that the cabinets are flown the same - not as a mirror image. This put a 12" LF onstage on one side and a 6" MF onstage on the other side. The room is not symmetrical, and the two sides do not sound quite the same from FOH. Nothing is blown or out of phase. I think this hang is part of the reason.

The cabinets are designed to be flown both ways; the can definitely be inverted - the manufacturers logo appears on the grille top and bottom both ways, so you can still read one of the logos if it's flown "upside down".

I am concerned and almost convinced the install should have been flown with one side inverted. This would make a mic on center stage react to the same components equally because they are equidistant, and get me more MF onto the center floor or the room for better vocal intelligibility. It would also help my stereo imagining at FOH.

The array is dead hung, no motors, so it will be a good afternoons task. There are 8 cabinets per side, and I don't think cabling will be an issue.

What's the forum's consensus? I've talked to the manufacturer and they are looking into it. My friend who mixes at a theatre across the street has a 12 box per side rig of the same cabinet, and his ARE inverted...and the manufacturer did his install after mine!

Thanks,
Greg
 
Re: Mirror image line array

Milt Hathaway said:
I'll bet it's because the room is not symmetrical.
Click to expand...


Thanks for replying - I'm sure the symmetry is part of it, but the room is close to symmetrical. I'm really wondering what folks think about what I am referring to regarding the nearest components to a mic centerstage and how that relates to equalization...

i have not had a chance to futz with it, but I plan on ringing a mic centerstage with our main graphic/parametric (TC Electronic EQ Station) and seeing what happens with what frequencies relative to each side of the PA. I'm betting the side with the 12" LF onstage reacts differently than the side with the 6" MF.
 
Re: Mirror image line array

Greg Huber said:
Thanks for replying - I'm sure the symmetry is part of it, but the room is close to symmetrical. I'm really wondering what folks think about what I am referring to regarding the nearest components to a mic centerstage and how that relates to equalization...

i have not had a chance to futz with it, but I plan on ringing a mic centerstage with our main graphic/parametric (TC Electronic EQ Station) and seeing what happens with what frequencies relative to each side of the PA. I'm betting the side with the 12" LF onstage reacts differently than the side with the 6" MF.
Click to expand...

You need to not think about the speaker as individual components and think of it as a system. The designer of said product should have designed it with appropriate overlap between the 12" and the 6" drivers to provide the desired directivity down low. The 12" is going to become essentially omni down near the lower crossover point anyway, so you're mainly concerned with the upper part of the 12" driver's passband.

Again, what is the product, and what do the polars say?
 
Re: Mirror image line array

With an asymmetrical cabinet layout-the pattern is going to exhibit a different polar response (and freq response) on one side of the cabinet vs the other. No way around that.

Which one is "right? Hard to say. Because as you move in the horizontal it is going to be different. Choose a position-others will be different.

The first thing I would do is to take measurements of each line and see how much of an issue it is. So 3 of each line would be a good start- On axis and off to the left and right-within the listening area.

THEN determine if you should worry about it,. Right now you are asking opinions about a product we do not know what it is-which is installed in an unknown fashion in a venue that we have no idea the size of the audience area-where it is in relation to the speakers or have any idea what sort of processing is used.

So other than that-it should be pretty easy to get an exact answer-because there is so much to base the answer on-------------------------------------------

Just sayin'------------------------------------
 
Re: Mirror image line array

EV XLC, right?

I've mixed on that box in every orientation, and the room has always played more of a factor than the actual box. If you hear something funky at FOH, move to the left or right a few feet, I bet it completely changes. Probably a weird reflection off a wall or something. Figure out what it is, and try to get some acoustical treatment on it.



Evan
 
Re: Mirror image line array

Ivan Beaver said:
The first thing I would do is to take measurements of each line and see how much of an issue it is. So 3 of each line would be a good start- On axis and off to the left and right-within the listening area.

THEN determine if you should worry about it,. Right now you are asking opinions about a product we do not know what it is-which is installed in an unknown fashion in a venue that we have no idea the size of the audience area-where it is in relation to the speakers or have any idea what sort of processing is used.

So other than that-it should be pretty easy to get an exact answer-because there is so much to base the answer on
Click to expand...

Hi again all...

1600 capacity, EV XLC127DVX - 8 per side over 6 EV XSubs per side. IrisNet software and EV TG-7 and TG-5 amps. FOH is dead center on the dance floor, 35 to 40 feet from the arrays. It's a good sounding Loud room and we do mainly national acts. I have been mixing in and out of this room since 1977.

I am not a measurements guy, I am a use my ears and a mic and maybe some program guy. I strongly believe in symmetry, especially in this room and in relation to equalization and components-to air-to mic.

I can clearly hear the arrays/cabinets sounding different (and so can my associate and touring engineers!) from behind my trusty H3000. My question is, the cabinets are designed to fly normal AND inverted, so why should I NOT invert them? I can understand why I wouldn't with a non-symmetrical cabinet like a Martin W8LC - they are not designed to fly inverted, and the software for the W8LC does take this into account (or so my buddies with a W8LC rig say)

Thanks!
 
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Re: Mirror image line array

Greg Huber said:
Hi again all...

1600 capacity, EV XLC127DVX - 8 per side over 6 EV XSubs per side. FOH is dead center on the dance floor, 35 to 40 feet from the arrays. It's a loud room and we do mainly national acts. I have been mixing in and out of this room since 1979.

I am not a measurements guy, I am a use my ears and a mic and maybe some program guy. I strongly believe in symmetry, especially in this room and in relation to equalization and components-to air-to mic.

I can clearly hear the cabinets sounding different (and so can my associate and touring engineers!) from behind my trusty H3000. My question is, the cabinets are designed to fly normal AND inverted, so why should I NOT invert them? I can understand why I wouldn't with a non-symmetrical cabinet like a Martin WL8 - they are not designed to fly inverted, and the software for the WL8 does take this into account (or so my buddies with a WL8 rig say)

Thanks!
Click to expand...

Ok so here are my simple minded set of questions:
1) They sound different how? Volume? Frequency? Is there a mode or resonance when you run just the left array? How about when you run just the right array?
2)Are you sure the gain structures and DSP are the same for each side?
3)Is there a bad driver or maybe a cabinet that is not working?

If it is not a room problem and it is a drastic difference at 40 feet I am inclined to believe there is a mechanical or electrical problem somewhere unless the horizontal angle is really enough off to matter.
 
Re: Mirror image line array

Greg Huber said:
Hi again all...

1600 capacity, EV XLC127DVX - 8 per side over 6 EV XSubs per side. FOH is dead center on the dance floor, 35 to 40 feet from the arrays. It's a loud room and we do mainly national acts. I have been mixing in and out of this room since 1979.

I am not a measurements guy, I am a use my ears and a mic and maybe some program guy. I strongly believe in symmetry, especially in this room and in relation to equalization and components-to air-to mic.

I can clearly hear the cabinets sounding different (and so can my associate and touring engineers!) from behind my trusty H3000. My question is, the cabinets are designed to fly normal AND inverted, so why should I NOT invert them? I can understand why I wouldn't with a non-symmetrical cabinet like a Martin WL8 - they are not designed to fly inverted, and the software for the WL8 does take this into account (or so my buddies with a WL8 rig say)

Thanks!
Click to expand...

Are the lines equidistant to the walls of the room or is one hung a little further/closer to the side wall? On axis, do they sound the same auditioned individually?

You mention that you're not a measurement guy, but I think you need one to help out. It's very likely not an amplitude/frequency issue but the way one side (or both) are interacting with the room AND each other. Measuring each side on-axis and at a distance ~3x the array length and then comparing the magnitude & phase responses should reveal any polarity issues or non-functional transducers. If the magnitude looks similar and the phase response has the same basic shape, it's time to look at off-axis measurements and see if/how left & right look different *at the mix position*. Again, take the measurement of each hang individually and overlay them on the screen. The side with the most deviation in the phase trace is the one to examine in detail with the impulse response tool. It should be possible to figure out where the reflections are coming from once you know how far away they are (which can be determined by the times of impulse arrival).

It is *possible* that the non-mirrored installation contributes to such a problem, but it's likely not the cause of the problem.

Another thought - at 40' from the array the mix position is VERY close, and it could be that there is a problem in only 1 box on 1 side. A measurement session should spot something like this very quickly.

Here's the deal: if both sides, when measured on axis, individually, have fundamentally similar responses the issue is a matter of what reflections are arriving at FOH and coloring the perception of the direct sound.
 
Re: Mirror image line array

Tim McCulloch said:
Are the lines equidistant to the walls of the room or is one hung a little further/closer to the side wall? On axis, do they sound the same auditioned individually?

You mention that you're not a measurement guy, but I think you need one to help out. It's very likely not an amplitude/frequency issue but the way one side (or both) are interacting with the room AND each other. Measuring each side on-axis and at a distance ~3x the array length and then comparing the magnitude & phase responses should reveal any polarity issues or non-functional transducers. If the magnitude looks similar and the phase response has the same basic shape, it's time to look at off-axis measurements and see if/how left & right look different *at the mix position*. Again, take the measurement of each hang individually and overlay them on the screen. The side with the most deviation in the phase trace is the one to examine in detail with the impulse response tool. It should be possible to figure out where the reflections are coming from once you know how far away they are (which can be determined by the times of impulse arrival).

It is *possible* that the non-mirrored installation contributes to such a problem, but it's likely not the cause of the problem.

Another thought - at 40' from the array the mix position is VERY close, and it could be that there is a problem in only 1 box on 1 side. A measurement session should spot something like this very quickly.

Here's the deal: if both sides, when measured on axis, individually, have fundamentally similar responses the issue is a matter of what reflections are arriving at FOH and coloring the perception of the direct sound.
Click to expand...

Hi again all -

The way we have been describing what we are hearing is "it seems like there are more highs house left". It can be heard when listening to both sides at the same time, or A/B-ing quickly.

I'll look at the distance to the walls later today. It's close on the second floor, and definitely not the same on the first floor. There are differences in the room per side, such as two dissimilar staircases to access the second floor. The staircase house left is my biggest suspect for reflections - the 6" MF are about 3 or 4 feet from it and that's one of the main reasons I want to flip the cabinets - to get them away from those stairs (painted steel). There is a lot of painted steel in the club, and these are W I D E cabinets...

I'm liking the suggestion of possibly using some acoustic treatment on the house left stairs to change/help the problem...

Hardware is fine; cabinets/install is a little over a year old. DSP is not the issue; we still hear the difference with touring consoles - right into the IrisNet. The analog lines to the DSP at the amp rack are fine, but I will quadruple check them for phase, impedence, and connection. In fact, I can substitute lines...I think I have done that...

I agree measurement can probably show us what we are hearing, but I'm liking the advice of a trusted colleague best so far..."Flip the ******* and see what it sounds like" - that's my style, too.

I've restacked a few PAs in my day - I remember fondly the first time I worked for Peter Yarrow. It was around 1979, I was a very young MON guy, and my boss didn't get the LF "crunchers", metal MF JBL horns with 2441/2482, and 2402 HF up high enough to begin with. I worked with Peter many more times over the years, and when the artist comes in and tells you your PA is stacked wrong, you get to restack it. Peter pays attention to those things, and he is always right.

(Art, if you're reading this - that wasn't you - it was Willie! Heeheehee!!)

Thanks - more to follow!
 
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Re: Mirror image line array

Evan Kirkendall said:
EV XLC, right?

I've mixed on that box in every orientation, and the room has always played more of a factor than the actual box. If you hear something funky at FOH, move to the left or right a few feet, I bet it completely changes. Probably a weird reflection off a wall or something. Figure out what it is, and try to get some acoustical treatment on it.



Evan
Click to expand...

HI Evan,

Do you generally see one array inverted when you use these boxes?

Thanks
 
Re: Mirror image line array

Greg, Flip one hang 180 degrees and see what it sounds like. If the box is designed to hang either way, give it a whirl. What's to lose. I doubt it's what you are hearing - much more likely acoustical interaction with the room as has been suggested, but taking a day and flipping one side of the PA is going to be cheaper and easier than acoustic treatment in the room, so I would certainly rule the PA hang out as a cause just for my own peace of mind. Why not?
PS - If it sounds worse, you can take another day and flip it back and be 100% where you were to start with. Nothing's changed except now you know a little more about your PA.
 
Re: Mirror image line array

Move closer to the array and have a listen, if it sounds okay there it's probably reflections causing this.

One installasion here in Oslo exhibits a somewhat similar behavior. If you're standing on the ch1 on the console, you lose hf left and it's the same on the right side of the console. First time I heard that I thought we'd lost one HF but moving closer confirmed that there was an reflection causing this from the balcony since it sounded normal up closer. There are symmertical balconies on both sides close to the main arrays, they have tried some acoustic treatment but it improved things marginally.

What solved this was replacing the old mx8750 with a ux8800 and move to a focused preset, improved dispersion control and fever side lobes made this almost inaudible.
 
Re: Mirror image line array

Greg Huber said:
I've talked to the manufacturer and they are looking into it. My friend who mixes at a theatre across the street has a 12 box per side rig of the same cabinet, and his ARE inverted...and the manufacturer did his install after mine!
Click to expand...
It would be unusual for the manufacturer to do the actual install so you might want to find out who provided the physical install and ask them why they are installed the way they are. Maybe they'll have an explanation or maybe they'll offer to come flip it.
 
Re: Mirror image line array

Greg Huber said:
The way we have been describing what we are hearing is "it seems like there are more highs house left". It can be heard when listening to both sides at the same time, or A/B-ing quickly.
Click to expand...

"Highs"? The high crossover point is 1600Hz. Everything I would consider "highs" is coming from a single vertical slot at the center of the cabinet. Flipping the array over might have some effect between 800Hz and 3.2KHz, but not above that.

There may be a problem with the highs in that array, but it's not orientation.

(Of course 800 to 3.2 is a pretty damn important area when it comes to vocals, so maybe that's the issue.)
 
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Re: Mirror image line array

Greg Huber said:
HI Evan,

Do you generally see one array inverted when you use these boxes?

Thanks
Click to expand...


Sounds like the venue is First Ave in Minneapolis... Am I hot or cold? :)

I hardly pay attention to the orentation of the boxes honestly. The room plays so much larger of a roll. I couldn't tell you what I see more of. If this is First Ave, I remember having a very good show there last time I was through. No noticeable differences between L & R PA. If you're hearing a noticeable difference, it may be time to check all the components in the arrays...



Evan
 
Re: Mirror image line array

Evan Kirkendall said:
Sounds like the venue is First Ave in Minneapolis... Am I hot or cold? :)

I hardly pay attention to the orentation of the boxes honestly. The room plays so much larger of a roll. I couldn't tell you what I see more of. If this is First Ave, I remember having a very good show there last time I was through. No noticeable differences between L & R PA. If you're hearing a noticeable difference, it may be time to check all the components in the arrays...



Evan
Click to expand...

Hi Evan

You've guessed correctly! A hoodie for you next time you're back or pm me an email and I'll pop it in the mail!

We've thoroughly check components, EV was in yesterday and loosened the tolerances on the rig because it's been stretched a bit with ~500 acts over the last year...

The PA sounds great, I am just looking for ways to make it sound even better. I think we will be flipping it soon, and I'll report back. Also, I picked up some new toys for FOH, so don't bother bringing a console or processing!

Thanks!
 

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Re: Mirror image line array

Greg Huber said:
Hi Evan

You've guessed correctly! A hoodie for you next time you're back or pm me an email and I'll pop it in the mail!

We've thoroughly check components, EV was in yesterday and loosened the tolerances on the rig because it's been stretched a bit with ~500 acts over the last year...

The PA sounds great, I am just looking for ways to make it sound even better. I think we will be flipping it soon, and I'll report back. Also, I picked up some new toys for FOH, so don't bother bringing a console or processing!

Thanks!
Click to expand...
The view out my office window. It used to be that there was grass growing on your building and not on the Target center, now it's the reverse.

1st ave.jpg
 
Re: Mirror image line array

Hi Greg-

I'll skip the "luddite" part of my speech simply to say that in less than 2 hours someone with measurement chops and Smaart, Systune or SIM could evaluate your entire rig, one box at a time, then one hang at a time, and then in stereo... and you'd KNOW what was happening.

You're applying guesswork and physical labor. Your choice, but in the end there is no objective means of evaluation.
 
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