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Two lavaliers technique


cinetj

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For backup.

And yes. Is very important to use two lav in live news, chat shows etc.

One week ago I saw (and heard) in Greek television the live news (the football news).

The guy to talk about news is off. Signal is off from lav (one used).

And the theme for commercial is on.

LOL

("teach me master", I thought)

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Yes , It used to be common practice to double mic in live news. I used to do it all the time for live shots, but it has become a dwindling practice. Most correspondents want to be all wireless these days, so they can walk away and get coffee and incoming news reports, walk back to the sat truck and etc, without having to get rewired all over again for the next one.

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Peter Jennings would never let me put two lavs on him even when he anchored World News on Location. He would only let me put a wired handheld nearby which wasn't my preference but he was the boss. The lav was always wireless as was his IFB. Charlie Gibson on the other hand would let you do what ever you wanted and I would use a wireless double lav and IFB set up and have a wired handheld standing by. I love doing live shots.

Andy

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Thanks for the info, interesting. You see double lavs on TV all the time.

Phasing makes sense, I was thinking perhaps since they would be so close together they may be in phase.. Of course i can't think of any benefit to mixing them either...

Yes I agree that because they are theoretically the same distance that there shouldn't be a phasing effect. That said I usually do hear a degrading of sound quality when listening to both mics summed. Usually I noticed some hollowness in the voice. Maybe reflected sound might be a factor.

Andy

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If the lavaliere elements are a 1/2 inch apart center to center, you shouldn't have a null until 13.8 kHz if you mounted them in the worst possible alignment, in line with the sound source, i.e., one above the other on a person. Mounted in the usual left to right alignment, even if a little off center, phasing issues would be much higher in frequency, easily outside the audible range.

Best Regards,

Larry Fisher

Lectrosonics

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" Do you split them left / right in case of rf hits? "

Huh ??

" so close together they may be in phase.. "

they should be in phase... that is the theory behind the cross-firing cardioids you see on so many podiums on award shows, etc...

" used three microphones up on the Presidential Podium "

actually there were at least 2 separate feeds and only one, if that, for a"spare". IIRC, at least through Reagan's years, WHCA recorded onto 2 independent Nagra recorders directly from the podium mics, and had a separate mic to feed the press distro system.

BTW WHCA still uses SM-57's, which are replaced relatively frequently (mostly for appearance), and always fresh windscreens, when outdoors...

Edited by studiomprd
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With the deepest respect for you and the products you represent, that I use and love, I don't think it would sound as good....

In my humble opinion, In theory, the two elements could never be in the same space. Therefore the timing of the sound pressure from the speaker would be slightly out of line and would add and subtract the sum of the two lavs with a slight comb filter result. I bet the low end (bass) response would suffer the most and just wouldn't sound quite right. Then there's the factor of varied frequency response between the two mic elements. X/Y stereo configurations probably work well, because they are matched and usually further from the source, hence a less exaggerated deviation of the waveform (inverse square law?) and panned hard L and R, and though they are supposedly mono compatible, they would never be as honest a frequency response as the single mic, when summed to one channel.

I wish I had two lavs that were nearly identical and could try this out in the "best possible way", with the two lavs right next to each other. I would track the two lavs through identical signal chains into my Pro tools rig and then record the sum and observe the variation of the resulting waveform from a single lavs waveform. Of course I would also listen to it, and either prove or disprove my assumptions that It just wouldn't sound as good as one lav, specifically in the low end. or maybe I'm just splitting hairs

30 years ago, politicians tried to talk to both the left and the right at the same time. Now they only speak in one direction...
Nice!!!
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Hi Dustin,

Here's my thoughts put into snips of your post:

"In theory, the two elements could never be in the same space. [snip] Therefore the timing of the sound pressure from the speaker would be slightly out of line and would add and subtract the sum of the two lavs with a slight comb filter result."

LEF-Consider a 2" studio condenser. Some people think they sound better than the average lavaliere. And yet most elements on the diaphragm are more than 1/2" apart. Since they are generally parallel to the sound source, phasing is not a problem. Oddly, they do have strong phasing effects at high frequencies off axis.

" I bet the low end (bass) response would suffer the most and just wouldn't sound quite right."

LEF- Low frequencies are affected the least due to the very long wavelengths (20 feet long at 50 Hz). This is not the same phenomena as having two speakers out of phase, which does destroy low frequency response. Comb effects are only apparent at mid range and higher frequencies for any usual mic separations. If the mics are 20 feet apart though, you will indeed have low frequency phasing.

"Then there's the factor of varied frequency response between the two mic elements."

LEF- The average of the two mics would be smoother if the gains are set about the same, as I would assume would be the sound mixer's goal. If one mic has a 10 dB "hole"' in its response at one frequency and the other mic does not, the summed response would only have a 3 dB drop.

"I wish I had two lavs that were nearly identical and could try this out in the "best possible way", with the two lavs right next to each other. I would track the two lavs through identical signal chains into my Pro tools rig and then record the sum and observe the variation of the resulting waveform from a single lavs waveform. Of course I would also listen to it, and either prove or disprove my assumptions that It just wouldn't sound as good as one lav, specifically in the low end. or maybe I'm just splitting hairs."

LEF- Sounds like an interesting experiment. You don't have to use lavalieres; use two identical microphones placed close together (touching) and pointing directly at a sound source. Set the overall audio gains to be equal including adjusting for relative mic sensitivities. If this bigger setup sums to a good signal, two lavalieres would just work even better being smaller and easier to get close together.

Thanks for thinking about this and being curious.

Best Regards,

Larry Fisher

Lectrosonics

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Yes I agree that because they are theoretically the same distance that there shouldn't be a phasing effect. That said I usually do hear a degrading of sound quality when listening to both mics summed. Usually I noticed some hollowness in the voice. Maybe reflected sound might be a factor.

That's one of my biggest pet peeves with a lot of the local LA news sets -- tons of reflected sound in the studio, I suspect from the "high tech" glass desks they use on the set. The sound is awful to me on some of these shows.

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Hi Dustin,

Here's my thoughts put into snips of your post:

"In theory, the two elements could never be in the same space. [snip] Therefore the timing of the sound pressure from the speaker would be slightly out of line and would add and subtract the sum of the two lavs with a slight comb filter result."

LEF-Consider a 2" studio condenser. Some people think they sound better than the average lavaliere. And yet most elements on the diaphragm are more than 1/2" apart. Since they are generally parallel to the sound source, phasing is not a problem. Oddly, they do have strong phasing effects at high frequencies off axis.

..........

Thanks for thinking about this and being curious.

Best Regards,

Larry Fisher

Lectrosonics

Hi Larry,

Thanks for your detailed response. I probably need to review some of my notes from college and brush up on some of the terminology I used, like comb filtering. I specifically like the example of the 2'' diaphragm. The 10dB drop in one frequency in one mic evening out to a summed 3dB drop between the two mics puzzles me mathematically- but seems right the way you laid it out. Acoustics are so easily misunderstood and I really appreciate you taking the time to break some things down for me.

Have a great weekend!

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Oops. Should have used an 8 dB drop not 10 dB. That's what I get for typing faster than I think and I type pretty slowly.

Here's the numbers carefully. Assume the two mics sum to one Volt ideally and each one of them is providing 0.5 Volts (0.5+0.5=1). To get them to sum to 0.707 Volts (-3dB) given that one remains a perfect 0.5 Volts, then the other one has to drop to 0.207 Volts to sum to 0.707. The Voltage ratio of .5 to .207 is 0.414 and the power ratio is 0.171 (0.414 squared). Then 10 log 0.171 = -7.95 dB or my now correct 8 dB hole. So if one mic has "flat" response at a frequency point the other mic can drop 8 dB with a combined result of a 3 dB drop, a major improvement.

An easier mental example is if one of our two mics drops out completely. You still have half the voltage from the other mic. Half voltage is only a 6 dB drop rather than a total loss of signal.

Assuming the usual mics have a somewhat random response about an average curve, multiple mics, very close together will give you a smoother response, i.e., closer to the average. This falls apart far off axis, at very high frequencies, of course.

Best,

Larry F

Hi Larry,

Thanks for your detailed response. I probably need to review some of my notes from college and brush up on some of the terminology I used, like comb filtering. I specifically like the example of the 2'' diaphragm. The 10dB drop in one frequency in one mic evening out to a summed 3dB drop between the two mics puzzles me mathematically- but seems right the way you laid it out. Acoustics are so easily misunderstood and I really appreciate you taking the time to break some things down for me.

Have a great weekend!

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