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Delays for Dummies |
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Tom66 
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 Topic: Delays for DummiesPosted: 06 May 2019 at 10:28am |
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Hi all,
I am trying to learn the basics of delay setting, with regards to horn length, phase, delay etc. We have a small dub reggae sound (1 stack) consisting of 2 Hog Scoops, HD15 kicks and fairly basic mids/top/tweeters, using a Behringer DCX2496 DSP. I am trying to find specific info on how to set up the delays for each channel, and tbh I'm struggling! All the calculators seem to apply to multiple stack PA systems in large venues, when we only run a 2 scoop stack in small to medium bar type venues. Basically I am unsure where to start with it all and would love a point in the right direction. - I'm guessing on my DSP, only 'short delay' will be applicable? - Can I just delay my tops and tweeters, given the subs are a relatively long horn path? (~2.5m for hogs?) Is there a good starting point to experiment? - How does phase come into it? - How do my kicks come into all this? - Is all this even needed in small/medium venues? A 'Delay for Dummies' guide that applies to basic amateur-run single stack setups would be really helpful I think, googling often reveals an overwhelming minefield! Sorry for the long-windedness, I'm doing my research but a forum with many knowledgeable people in the know is also often a great place to learn from others. Thanks in advance for any pointers! |
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toastyghost
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Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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Posted: 06 May 2019 at 11:59am |
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The delay for dummies guide is to do a course on SMAART or similar. At the very least, a copy of REW and a USB UMIK-1 to take measurements, and a lot of research on best practices and what to look for.
Yes, it is very needed regardless of venue size. Without, there will be problems of distortion, dips and peaks in magnitude response, smearing, and dispersion. If you try to do it any other way the results will not be great. Especially on mids and highs. Look up DIYRM page on Facebook and read all of the PDF documents Scott has posted there - they’re an excellent resource. Edited by toastyghost - 06 May 2019 at 12:01pm |
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Mikkel
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Joined: 17 May 2013 Location: Huddersfield Status: Offline Points: 549 |
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Posted: 06 May 2019 at 2:13pm |
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out of interest toasty, is it feasable to map the horns in hornresp anx get groupdelay data from that to get a ballpark figure to work from? As hornresp even has phase response, where you can line up traces using the delay function, so using that and the group delay could you get an idea of where to start?
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Tom66
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Posted: 06 May 2019 at 3:10pm |
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Thanks toasty, will give those suggestions a go. Just wondered if there were any basic principles that could be followed to get a half decent result as a first go, without investing in more hardware/software.
Cheers.
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Timebomb
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Joined: 11 October 2004 Location: Lancaster Status: Offline Points: 2716 |
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Posted: 06 May 2019 at 3:17pm |
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The hornresp model might get you somewhere roughly near but you could still be 1/2 a wavelength out and cause a cancellation, especially if you are trying to align a ported mid high thats tuned say 60Hz, many factors such as the actual shape of the chambers will affect actual phase, just take some measurements and look as the phase response, move the mic, look at the phase response, delay the mid high a bit more / bit less, look at the phase response, you will start to get an understanding of aligning across a crossover frequency. Aligning impulse response is a bit more complicated, so to get started start by aligning 2 sources in phase around there crossover.
IMO you can read, study do courses etc and that can all help but sooner or later you need to get a measurement mic and some software and take some measurements.
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James Secker facebook.com/soundgearuk
James@soundgear.co.uk www.soundgear.co.uk |
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toastyghost
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Posted: 06 May 2019 at 3:47pm |
The software is free, and for solely doing phase alignment technically any mic will do so long as you use the same one for the entire process. Edited by toastyghost - 06 May 2019 at 3:47pm |
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Conanski
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Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2543 |
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Posted: 07 May 2019 at 1:08am |
The basic idea is everything is delayed to the speaker with the longest horn path.. which is usually the sub. So subs get no delay, kicks are delayed to the subs, and then tops are delayed to the kicks. If tops have reflex mids with a horn loaded CD and are powered separately(bi-amped) the CD will get less delay than the mids. The process is best done 2 boxes at a time but setup a stack as it will usually be deployed and mute everything but the 2 boxes being aligned. Get the subs and kicks aligned as best you can and then move up to the kicks and mids, and repeat as necessary. Your processor has an Auto-Align feature built-in that can do a good job with a measurement mic plugged in, but it may take a few attempts and you need to double check things for some independent confirmation. For me that confirmation comes in the form of a free software package called REW that does FFT analysis, with this I can see if the alignment suggested by the DCX is actually doing what is required.. the freq response thru crossover should flatten and phase response unwrap. Also note that simple math will show you how much minimum delay a horn will need based on path length so you should be able to tell if the processor is in the right ballpark, and actual delay needed for correct acoustic alignment will be a little more than the math suggests. One gotcha with your system in particular is that scoops generally can't be time aligned because they produce both direct and rear horn loaded output, but when used as subs the horn output should dominate so it should work out. Some experimentation may be necessary.
Edited by Conanski - 07 May 2019 at 2:03am |
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corell
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Posted: 07 May 2019 at 2:48am |
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Even for a 3m horn, the sound only travels 9ms from throat to mouth. But the group delay of the kick section (or any passband) might be as high as 20ms at the crossover region. So delaying only by physical path lengths could yield very wrong settings in the end...
Most of the time, the delay for the kick will need to be shorter (not longer) than the physical pathlangth difference of both because the kick has its resonance near to the crossover frequency while the subs resonence is an octave or more apart, which means that GD of the kick would be higher than GD of the sub at that crossover frequency. |
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Keen
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Posted: 07 May 2019 at 3:33am |
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filter/eq settings influence GD, use filter wizard in horn resp to refine your starting point for measurements
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toastyghost
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Posted: 07 May 2019 at 7:25am |
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Scoops can be time aligned just as easily as any other speaker.
Corell is also 100% correct. Longest horn path is going to be wrong. You need to think about the group delay of the cabinet, which will be more affected by loading type and filter choice. It’s a relative problem too, not absolute. I’ve never seen good results from the auto align on any basic DSP either, in principle it can work but it’s not going to make good judgement calls about the data it receives from the mic based on its location, reflections, etc. For HF horns and reflex mids, using 4th order matched slopes, a polarity inversion is likely to yield better results than delay alone. The phase response will not unwrap, unless you set the measurement delay to that range. You can do that even if the boxes are not in time. The DIYRM page already has several articles that show how to choose where and how to align through crossover. It’s about as close to a dummies guide as you will get and is based on free or cheap kit. Edited by toastyghost - 07 May 2019 at 7:34am |
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Tom66
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Posted: 07 May 2019 at 8:57am |
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Thanks for all the helpful replies guys
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Timebomb
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Posted: 07 May 2019 at 9:48am |
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Scoops, tapped horns etc can be aligned, you need to make sure that group delay / phase measurement is derived from peak impulse , not primary impulse, then it will plot phase of the horn part of the scoop, not the direct radiating.
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James Secker facebook.com/soundgearuk
James@soundgear.co.uk www.soundgear.co.uk |
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Tom66 wrote: