Latency and Delay Ramifications for speaker alignments
mikekars
Posts: 8
I am trying to set up different subwoofer cardiod patterns and also align the subs to the mains using physical positioning and delays. I have read the various posts about latency in the DR260 and DRPA I have both devices and sometimes use both at the same time in series or parallel for differnt output bandpasses. But I am still not quite understanding if and when the latency will change and what exactly the implications are. I am probably making this more complicated than it is but here goes:
Question 1: In one detailed study it seemed the DR260 exibited a minimal and fixed latency for the mids and highs (<2msec), but showed significantly longer latency for the low output depending on the slope of the crossover between low and higher bands. My main confusion here is whether the latency figures given for a particular crossover type/slope apply just to the output of the low channel, or to all channels. If the latency applies to all the outputs consistently, then all outputs have the same built in latency and further delay setup is fairly straight forward. However if the latency between the low out and higher channel outs is different, then that needs to be taken into account and the delay setup becomes more complicated.
Question 2: Why doesn't the DRPA exibit similar crossover slope depencies? How come it is just "1.79msec" (from one of the posts) across the board? That seems fast and easy to deal with.
Question 3: Is there a whole different approach to this that is much simpler than I am making it. And I hope that answer is not just "use your ears"!
Question 1: In one detailed study it seemed the DR260 exibited a minimal and fixed latency for the mids and highs (<2msec), but showed significantly longer latency for the low output depending on the slope of the crossover between low and higher bands. My main confusion here is whether the latency figures given for a particular crossover type/slope apply just to the output of the low channel, or to all channels. If the latency applies to all the outputs consistently, then all outputs have the same built in latency and further delay setup is fairly straight forward. However if the latency between the low out and higher channel outs is different, then that needs to be taken into account and the delay setup becomes more complicated.
Question 2: Why doesn't the DRPA exibit similar crossover slope depencies? How come it is just "1.79msec" (from one of the posts) across the board? That seems fast and easy to deal with.
Question 3: Is there a whole different approach to this that is much simpler than I am making it. And I hope that answer is not just "use your ears"!
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Comments
I feel you are asking all of the wrong questions. You are trying to align by ear or with a tape measure and these methods are not accurate...you can easily do more harm than good. Judging from your post, you have become excessively interested in audio system design and optimization. Thats not a bad thing but the beginning of a long journey...there are no magic latency numbers that you can add to your tape measure equations that will give you the results you are looking for.
You need to be making your measurements with a dual FFT program/analyzer and it will take into consideration latency as well as physical distance...it doesn't matter what the specific latency is that a DSP exibits from any output, it is all calculated as one number by making use of pink noise and a measurement mic. When the program displays a delay number for a componet or speaker box, the number is a combination of physical distance from mic to speaker PLUS any latency created by electronic equipment.
The dual FFT program costs money. The setup with computer, interface, and measurement mic costs money. The training to operate the dual FFT program costs money. And don't tell me " Oh, I just wanted to do a little tweeking on my band's PA, I don't want to spend all that money"....Your post tells me that your interest in the topic has progressed beyond that point.
Dennis
For the DR260, if you have a stereo input with some arbitrary set of DSP program settings such as a low/high crossover, peq, etc. but with no delay entered, will the latency between the input and the outputs be consistent across all ouput channels? Specifically will the latency of the low channel output(s) always be exactly the same as the latency of the high(er) outputs regardless of what that latency turns out to be?
Latency occurs equally at all frequencies but if you have it going through a crossover, the various xo filters add different amounts of delay (latency) so you are not going to end up with the same number everywhere.
Ah, excellent answer. I guess that explains the need for empirical measurments against the final configuration. Thanks for your considered reply.
Mike
Mike -- if you want to nail this thing. You will have to get into some FFT technology like Dennis said. Smaart (Rational Acoustics) has a 30 DEMO that will allow you to make corrections to the system. It is a very complicated program (at first) but one that will teach you more about sound than what your ears alone can do. If you do the download -- Don't open it until you have watched all the videos on rational's site and you know for certain you have everything you need to make it work. You will need every bit of 30 days to get the best of it.
If you are interested -- I may be able to get you going on it. http://www.rationalacoustics.com
Most of the demos out there are fully functional except for the 30 day time limit AND maybe the ability to save stored traces. Have you had a chance to dive into phase aligning your drivers using the software?