Amps
[Top] [All Lists]

Re: [Amps] Audio/RF compression

To: amps@contesting.com
Subject: Re: [Amps] Audio/RF compression
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 12 Jan 2017 11:13:22 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
On Thu,1/12/2017 10:51 AM, Joe Subich, W4TV wrote:
Delays of over 100 ms begin to become distracting.  It is a matter of
the user's ("talent" for broadcasters) ability to handle distraction.

YES! One thing I did a LOT of was providing sound for large events both indoors and outdoors. In such systems, the acoustic travel time between loudspeaker and listener typically ranges from as little as 20-30 msec to as long as several hundred msec. This is all due to the speed of sound, which is approximately 0.9 msec/ft.

Latency becomes an issue when main loudspeakers are 30+ feet over a stage and further displaced side to side, and spill sound to the stage, often in the range of 30-40 msec. This drives musicians nuts, and is part of the reason large and complex stage monitor systems are used. Performers hear themselves undelayed (or minimally delayed) at levels higher than the leaked sound from the main system. Originally this was done with big speakers on the stage floor; now it is far more commonly done with miniature in-ear headphones connected to stereo UHF receivers.

And as Joe has noted, latencies greater than about 80 msec can turn a highly trained announcer into a babbling fool; we've all witnessed guys like this slow down and stop. I've experienced it myself talking into a mic at the mix position (100 ft or so back in the audience) of a large outdoor system.

So far, what I've described is entirely due to acoustic travel time between loudspeaker and listener. Roughly 25 years ago, we began using DSP extensively in large sound systems. One of those early systems had so much latency that it was unusable; the first successful systems had latencies in the range of 7-15 msec, depending on the size of the DSP system, number of channels, amount of processing being done. These latencies ADDED to the acoustic travel time, so keeping latency low was always important.

73, Jim K9YC

_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

<Prev in Thread] Current Thread [Next in Thread>