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Author Topic: When do I need to start delaying signal  (Read 737 times)

Scott Olewiler

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When do I need to start delaying signal
« on: December 11, 2013, 06:35:45 am »

I just started a small production company that so far has been doing small venues where my FOH speakers are fairly close together and the stages are just big enough to fit the band. I understand from reading the forum that there are times I should delay signal to some of my speakers so it all arrives at the listener at the same time. I'm currently using 2 (amp powered) tops over 2 active  direct fired subs.

Are there basic rules of thumb as to when I need to start delaying my signals, like size of venue, distance of  stage drums to subs, minimum mis-alignment between top drivers and subs; things like that?

Also I'm not sure what type of delay to buy since I need to delay the entire signal going to a speaker. Are there delays/processors made especially for this?  Since I'm new at this is there a simple tool I can buy to help measure the delay needed or is it best just to use my ears to "tune" in the correct amount of delay?
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Jay Barracato

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Re: When do I need to start delaying signal
« Reply #1 on: December 11, 2013, 09:40:22 am »

I just started a small production company that so far has been doing small venues where my FOH speakers are fairly close together and the stages are just big enough to fit the band. I understand from reading the forum that there are times I should delay signal to some of my speakers so it all arrives at the listener at the same time. I'm currently using 2 (amp powered) tops over 2 active  direct fired subs.

Are there basic rules of thumb as to when I need to start delaying my signals, like size of venue, distance of  stage drums to subs, minimum mis-alignment between top drivers and subs; things like that?

Also I'm not sure what type of delay to buy since I need to delay the entire signal going to a speaker. Are there delays/processors made especially for this?  Since I'm new at this is there a simple tool I can buy to help measure the delay needed or is it best just to use my ears to "tune" in the correct amount of delay?

It sounds like you are talking about 2 different uses of delay.

The first is delaying earlier arriving signals from one part of a speaker system to another part of the system, like when you have tops and subs.

This is part of system optimization and has had entire books written on the topic.

The second is delaying the entire FOH to the back line. This can be useful when the FOH system is drastically in front of the back line including the drums. I tend to look at about 30 feet before I start to get concerned about the difference in arrival times. In other words if the mains are 30 feet in front of the back line AND the back line is loud enough to significantly contribute to the FOH sound (less than 6db difference), then it may be worth delaying the mains.

It should be noted that adding the delay may make sound out front better but it may cause additional problems at frequencies with little pattern control by making the bleed back from the mains even further out of time with the sound from the back line on stage.



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Jay Barracato

Scott Olewiler

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Re: When do I need to start delaying signal
« Reply #2 on: December 11, 2013, 11:31:20 am »

It sounds like you are talking about 2 different uses of delay.

The first is delaying earlier arriving signals from one part of a speaker system to another part of the system, like when you have tops and subs.

This is part of system optimization and has had entire books written on the topic.

The second is delaying the entire FOH to the back line. This can be useful when the FOH system is drastically in front of the back line including the drums. I tend to look at about 30 feet before I start to get concerned about the difference in arrival times. In other words if the mains are 30 feet in front of the back line AND the back line is loud enough to significantly contribute to the FOH sound (less than 6db difference), then it may be worth delaying the mains.

It should be noted that adding the delay may make sound out front better but it may cause additional problems at frequencies with little pattern control by making the bleed back from the mains even further out of time with the sound from the back line on stage.



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OK Thanks, you've answered one of my questions.  Since I normally have my tops over my subs, I haven't been worrying about the system optimizing but I guess there's no guarantee they are in sync as is.  So how do I measure that and what type of delay do I buy to delay which ever send (tops or mids) I need to delay.
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Scott Olewiler

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Re: When do I need to start delaying signal
« Reply #3 on: December 11, 2013, 11:32:19 am »

OK Thanks, you've answered one of my questions.  Since I normally have my tops over my subs, I haven't been worrying about the system optimizing but I guess there's no guarantee they are in sync as is.  So how do I measure that and what type of delay do I buy to delay which ever send (tops or mids) I need to delay.

Sorry I meant tops or subs
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Tim McCulloch

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Re: When do I need to start delaying signal
« Reply #4 on: December 11, 2013, 12:22:41 pm »

OK Thanks, you've answered one of my questions.  Since I normally have my tops over my subs, I haven't been worrying about the system optimizing but I guess there's no guarantee they are in sync as is.  So how do I measure that and what type of delay do I buy to delay which ever send (tops or mids) I need to delay.

The classic audio answer applies:  "It Depends...." ;)

A "system controller" or "system DSP" is typically used for this.  Examples include the dbx DriveRack series, BSS OmniDrives... I think Behringer still has one, also.  There are a significant number of choices that didn't exist 10 years ago.  They all pretty much do the same things (input EQ, compression and delay, output EQ, delay and limiting) although some are better or more user-friendly than others.

If you're using the same brand of tops and subs I'd expect the manufacturer to provide you with information about any needed delay of tops or subs relative to one another when using the manufacturer's recommended crossover parameters.  Note that while we often hear folks talk about delaying their subs, more often the tops actually need a bit of delay.  Why?  Because the high-pass filter (at the lower end of the sub's range) that helps protect the speaker also introduces some time delay as it does it's job.  The lower the frequency and steeper the filter (more db/octave), the greater the delay.

In the world of system optimization, you do the above alignment first.  Make the tops and subs work together as best they can.  THEN you can apply full system delay (at the system controller inputs) in the manner Jay talks about.  Whether or not delaying the mains to the band's stage sound will help you depends on how close the PA's SPL is to the band's stage SPL.  Jay mentions 6dB and I think that's the right place.  Also important is how much of the venue is covered by BOTH sources within that 6dB window.  For most weekend bar gigs I'd skip trying to delay the PA to the back line instruments, but you can experiment once you have a way to do the delay.  A good estimate (for starting purposes) is 0.9ms per foot of distance between the PA speakers and the loudest thing on stage that is in the PA (and in a small room, EVERYTHING probably is picked up by the vocal mics, which presents other time issues that will complicate our discussion :( )  If you stand equally between the PA speakers and match the level of PA to band stage SPL, lengthen the delay time in small increments until you hear the sound image come together.... meaning you don't perceive the PA and stage as being separate sources.

That said, your delay alignment is only valid for the spot you stood in.  The delay time needed will change based on where the listener is relative to the stage and the PA speaker covering their spot.  You can only optimize delay settings for ONE SEAT IN THE HOUSE.  Everywhere else is a compromise, and whether or not that compromise is worth the effort depends on the political value of whoever is in the sweet spot.

Have fun, good luck.

Tim Mc
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Jay Barracato

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Re: When do I need to start delaying signal
« Reply #5 on: December 11, 2013, 01:22:55 pm »

OK Thanks, you've answered one of my questions.  Since I normally have my tops over my subs, I haven't been worrying about the system optimizing but I guess there's no guarantee they are in sync as is.  So how do I measure that and what type of delay do I buy to delay which ever send (tops or mids) I need to delay.

As Tim said, you have lots of choices for system optimization. I personally use a Sabine navigator which I choose because I preferred the software interface. I also like Xilica.

I find the lower level Drive racks to be less than flexible if you have anything other than a standard 2 or 3 way system.

It would help if you could tell use about your speakers and amps.

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Jay Barracato

James A. Griffin

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Re: When do I need to start delaying signal
« Reply #6 on: December 13, 2013, 10:23:13 am »

It would be helpful to know what speakers you're using.   

Many (most??) speaker systems that contain both tops and subs have time alignment built in to the physical mounting mechanism.   For instance, if you have JBL VRX tops and subs, when the tops are mounted on the sub via their poles, the two are properly aligned.

If your system is powered, there is often some alignment in the subs DSP that allows you to delay them.
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