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In Reply to: Re: Microphone Rise Time- Is this the key? posted by JOEY. on December 02, 2002 at 12:53:53:
Joey, the fastest practical risetime in a microphone is about 10us. Faster is possible, but signal/noise suffers, bigtime. Larger element caps are somewhat slower, but they can still have a pretty good audio bandwidth. Sometimes large area mikes can sound better. 30 years ago I did a live recording with Santana at the Fillmore Auditorium. We used only the stage mikes which were Shure or Electrovoice dynamic mikes. Wally Heider (sp) recording ADDED Neuman large element mikes and parallel recorded the event. When we listened to both tapes, we chose the Heider tape over ours, because of the improved transient response. ps. I haven't forgotten my info to you
Follow Ups:
Hello John,With 10 us as typical of the fastest practical rise-time for microphones, let alone loudspeakers, it is now clear to me that this factor (along with frequency response and dynamic range) must surely be one of the greatest impediments to recreation of the live event. Imagine even a 10 kHz tone (100us period) having its 'leading edge'(1st 1/4 cycle of 25 us duration) delayed by 10 us AT BEST. No wonder a trumpet never sounds real. Horror of horrors, imagine what happens with really slow microphones. Thanks again for the offer of the microphone info- there is no hurry.
HAVE FUN,
Joey, 10us risetime is a -3dB response at 35kHz with a single pole rolloff. This is barely possible with 30 ips analog recording, quality vinyl reproduction, SACD or DVD 24/96kHz recording. Most of the 'delay' associated with the risetime is JUST DELAY. That is: Total delay of the event, so it does not effect the sound. However CD cannot approach this ideal, and in practice is much worse. Speakers can have extended bandwith, but usually are not that good. An important point is that there are many factors that make a difference in audio reproduction, risetime is one of them.
Hello John,I think I got the wrong end of the stick. Now I take your point, earlier on I understood you be referring to a type of delay and hence my concern about blurred leading edges since 10 us represents a significant time period compared to the period of a 10 or 20 kHz tone, BUT NOW...I understand (hopefully) what we are really talking about is the fastest possible SIGNAL rise time that can be tracked by the microphone (quite a difference!). If that is the case then I am happy and would withdraw my contention that rise-time is a VERY significant issue, especially where the rise-time allows a 20kHz+ signal to be tracked accurately. (unless of course someone can prove that we can hear OR perceive frequencies greater than 20kHz).
HAVE FUN,
JOEY.
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