Reply posted by Paul Tucci on August 20, 2001

To further the conversation and probably take it into unintended waters for the original poster, I'd like to add this observation. It relates to what has been said about the "magic tape measure" that someone mentioned.

As a visiting band engineer, I cannot assume much about the stacks and racks provided for me. There is a wide range of expertise displayed by both reinforcement providers and in the installed systems I utilize. I'd like to relate an anecdote from two days ago.

With a 5 deep Clair R-4 speaker system in the air, you'd ASSUME that life is good. I knew better from my 3 previous visits to the venue. (By no means is this a slam on Clair, OK? They are not responsible for the install.)

Nothing ever sounded good in the room to me; none of my shows, or even a CD. Too many hard, parallel walls, too many reflections,and a speaker system that just sounded sloppy. My Smaart measurements showed me that the arrival times of the speakers' components were all over the place. Not just a little either, but a 40 millisecond difference between the highs and lows. Not right.

The culprit? The MediaMatrix system controller. By measuring the electrical signal at the input to the amplifiers, I found time differences between the subs, lows, mids, and highs. The mids arrived earliest, call that time zero. The subs signal arrived next, but 9.8 msec later. The highs followed but were 23.9 msec behind the mids. Last to arrive was the lows. They came to the party a full 58.14 msec behind the mids. No wonder the speakers sounded drunk.

The delay was not introduced by the crossover section of the MediaMatrix; there was no delay programmed in there. Somewhere, somehow in the digital configuration, an unusable amount of delay is introduced. I am not Media Matrix fluent, perhaps someone else is and can help me clarify how that happens. Tom?? I just know it's wrong, and that it's wrong to ASSUME that front loaded cabinets are automatically time aligned. The carpenter's tape measure does not measure within the digital domain.

There you go,
PT


Reply posted by Marty McCann on August 20, 2001

Within the virtual domain of Media Matrix, the more devices inserted in any signal path, the longer the latency. You can initiate a delay compensation feature within the software and recompile the program. For that matter, if you can access the system, you can insert delays into the outputs (recompile) and calibrate the true acoustic points of signal origin.


Reply posted by Paul Tucci on August 22, 2001

Marty,

Thanks for the response. Access to info is what makes this forum shine. So, the more vitual devices created, the more inherent latency. I can buy that. Processing takes time and digital horsepower.

The system tech, who was there the first three trips in, did in fact recompile. No improvement in the acoustical measurements at that time. This time no recompiling was done. Does the recompiling somehow accumulate the processing delays and distribute it evenly? ie, an overall latency that affects all the signal path?

As far as adding delays to the mess to time align the arrivals...Rather than adding a sizable and UNMUSICAL amount of time to the earlier arriving bandwidths, I left it as it was. I will not be responsible for putting the PA 50-ish milliseconds behind the band. In the end, it was a sellout, the crowd loved, and unfortunately I'll be back in the hellhole sometime.

Thanks,
PT