Rational Acoustics



Dr. J
October 22nd, 2014, 11:24 PM
What are some consequences of delaying FOH to Backline or even to monitors?

Is there a range depending on the size of the stage where you would simply just leave it alone? I can hear changes but cannot decide if I like it better...


Thanks!

Josh Voyles
November 20th, 2014, 06:07 PM
I can't really give you a scientific answer, but I try to delay my FOH when possible.

There's a lot of situations very the stage volume can get very loud and negatively contribute to your FOH mix.

All that being said, I could see there being some challenges for different rooms/different PAs.

In one spot the different between the mains and drum wedge could be 20ms and different in another. It also starts getting more complicated when you add fill speakers.

Maybe one day I'll be an expert. But in the mean time, I just usually try to minimize phase issues as much as possible. Hopefully the more I measure, the more I'll be able to visualize what my speakers are doing in a given space and I'll make better decisions before the PA even enters the room.

Dr. J
November 22nd, 2014, 01:08 PM
Thanks for the input Josh. Every time I do this - someone on stage has trouble hearing.... Out front - I'm happy but apparently it doesn't mean the band will be. what the heck is going on?

However, I have noticed that by aligning to Front row monitors seems to make the most band members happy..

I am in horrific acoustic environments most of the time and that is most likely why these things backfire. That is ok... Most of what I have learned has been by trying and comparing...

Josh Voyles
November 22nd, 2014, 07:03 PM
Thanks for the input Josh. Every time I do this - someone on stage has trouble hearing.... Out front - I'm happy but apparently it doesn't mean the band will be. what the heck is going on?

However, I have noticed that by aligning to Front row monitors seems to make the most band members happy..

I am in horrific acoustic environments most of the time and that is most likely why these things backfire. That is ok... Most of what I have learned has been by trying and comparing...


If the said member is hearing his amp and PA firing at the same time, he's not going to hear the difference in phase he might be used to hearing. The amp and speaker or going to sound more like "one." (At least this is the way I understand it.)

Can you share more about your setup and maybe even post a picture?

I took a video last night of my rig that I'll post soon. I actually didn't delay FOH. Between the soloists coming up front and the two front wedges, I just let it go. But I think pushing it back to the horns might have improved things.

Josh Voyles
November 22nd, 2014, 07:32 PM
Here's the video I was mentioning.

http://youtu.be/yrnvMcjJqxc

Dr. J
November 28th, 2014, 10:58 AM
Sorry for the delay Josh.... I must not be getting email notifications that a reply has been made. I go through this on this site every so often.

I don't have any screen shots of the alignment from this but really all I do is use the delay locator of the FOH, then delay locate for monitor (either front row or drum wedge if used) and then slow the FOH down to match.... All using delay find.

If I get a chance to do this again soon - I will post a screenshot.

Thanks man!

PrestonSoper
November 28th, 2014, 11:45 PM
Here is a thread link with some good insight into this topic:
http://forums.prosoundweb.com/index.php/topic,116236.0.html

PrestonSoper
November 28th, 2014, 11:54 PM
And another more recent one:
http://forums.prosoundweb.com/index.php/topic,152474.0.html

gluis
February 24th, 2015, 12:36 PM
The process is basically to align the PA to the loudest source in your stage; snare drum, horn section, drum fill... what this will do is to present to the front rows of your patrons a more coherent wavefront and better image as the sound will closely appear to be originating from the stage as opposed that from the PA.

Your comments about musicians not being happy about it is interesting to analyze: Whichever delay you use on your PA to align it to the stage sources, will add to the mismatch between backline and PA at the stage. Remember, if you are on the stage, your closest source is obviously the stage, so the PA is already delayed by musician's perspective. Adding delay to the PA is going to increase the time between instruments hitting the musician's ears and the PA getting to them. So as you align the PA to your stage from the audience perspective, you are doing the opposite from the musician's perspective.

To be honest I never encountered a musician complaining about delay mismatch on the PA in reference to stage, even if it is not in so many words. I do this kind of alignments before the artist comes to the stage, so for them it would be as it is. In any case the distance, and hence, the delay from the PA back wave to the stage is different in every venue, and there's nothing you or them can do about it.

I hope this helps.

GS

Dr. J
February 24th, 2015, 07:54 PM
Is there a distance rule of some sort for this kind of thing? For example... Under 10 feet - don't bother? What I failed to say in that earlier post is the fact that I also placed all my subs in the center of the stage which apparently loaded the stage with low end. That would certainly make things harder to hear.

Once I figured out the cardioid configuration for the subs - the staged cleared out a great deal...

I may be trying to get too fancy with these small clubs...

Dr. J
February 24th, 2015, 07:57 PM
Thanks for the article links Preston! It goes right along with my initial thoughts.

Harry Brill Jr.
May 1st, 2015, 01:56 AM
Here's the video I was mentioning.

http://youtu.be/yrnvMcjJqxc

Dead link

Harry Brill Jr.
May 1st, 2015, 02:06 AM
My take on this is if the stage and mains are of similar levels and the mains are physically closer than the loud item on the stage that is of similar volume, then you might benefit from delaying the PA. In most of my shows this is not the case. The PA is way way louder than the stage and adding even more time than all the latency that is already building up in the system through the various digital devices is unwarranted. I also find the system to be the most stable and listenable when the feedback threads hold is reached at low latency and it's rung out. One thing to keep in mind is that this is a moving target. It depends on where you are listening. When is the timing correct? Also it makes more sense to align low frequency and not worry too much about the rest. Aligning to the bass rig or drum fills makes the most sense to me. Like I said, most of the time my musicians are on IEMs and this isn't even an issue. Not using IEMs these days is almost inexcusable. the difference to the audience is huge. It's as if the musicians simply don't care about the final product. It's not always practical though. If you are playing rooms that barely have vocal reinforcement systems then you need your amps but in that case we don't need to delay the pa to the back line.

gluis
May 9th, 2015, 11:22 AM
I understand it is a moving target, but is fair to say that every person that listen to, let's say, the snare crack from the PA, then from the actual snare, the image will be shifted (Haas effect), unless the level difference is big enough to ignore the first one. So even if it is a moving target, if you are judicious using delay (of course taking into account all latencies accumulated), you can enhance the image for your first rows using delay on the system.

BTW, stage/FOH SPL depends on many variables. There had been many cases I had to align to a Horns section for example. IEM's will not make a huge difference in those instances. In any case, I rarely do it anymore because the band I'm currently working with is on IEM's, I barely have time to tune the system as it is, and it is not a priority. It is more like a luxury to be able to do it in my current situation. Last time I did it I was hired to tune the system and mix a live TV awards show, and it definitely made a difference from the audience standpoint. In most TV shows you can't afford to have a loud PA, so stage volume was a real contributor to what the audience heard.