Thanks for the flashlight idea! I first learned about it from you.

(Don't remember in which thread you mentioned it, I think it was the U47 and LOMO shootouts)

hello !
If I put 2 microphones in front of an Gt amp, at exactly 20 inches.
The difference between 2 capsules generated solely by their placement in the windscreen will cause phases problems ?
The difference in time for 1 inch, which could represented the difference between two capsules is not too short to create a phase problem that we could hear ??
I am septic... I did calculations, but since I'm bad at maths this may be false. Let me know
(in meters)
sound speed-> 340m/sec
wavelength : for 20Khz and 15Khz and 1 khz
->
340/20000 = 0,017 meters -> ≈ 0,66 inches
340/15000 = 0,022 meters -> ≈ 0,86 inches
340/ 1000 = 0,34 meters -> ≈ 13,3 inches

for that phase of a sine wave is inverted we agree that we need to add a delay the corresponding half of its wavelength

20Khz we need to have 0,33 inches difference...
15Khz we need to have 0,43 inches difference...
1Khz we need to have 6,6 inches difference...

(if i say shit let me know)


i think you don't need to use un scope... a string or anything where we can read inches will be sufficient

sorry my english is not good....
And i think i'm probably Off topic.....

That all seems reasonable to me monsieur. But what do I know? I decide if the mics are going to be "three fingers away" or "five fingers away" then I just look at the waveforms. I didn't realize how caveman I am.

It's never a bad idea to pull out a tape measure. Otherwise most dynamic mics have similar capsule orientation and most LDC's you figure it hits it right about in the center of the mic, past the windscreen.

losthighway wrote: then I just look at the waveforms. I didn't realize how caveman I am.

are you being ironic ?

?
One day i will take english lessons and i will understand

three fingers or five...at least I'm not the only one...

anyway

It seems easier for me to tell when the mics are perfectly out of phase than when they're perfectly in phase...so I invert the phase of one mic on the pre...then I listen with headphones and move it until there is no, or the least amount of sound...then flip the phase back on the preamp.

owens wrote:It seems easier for me to tell when the mics are perfectly out of phase than when they're perfectly in phase...so I invert the phase of one mic on the pre...then I listen with headphones and move it until there is no, or the least amount of sound...then flip the phase back on the preamp.

I read every response thinking "nobody's gonna say it?!?!" but I got to the last one, and you did. I'd say that's the best way I know of, without relying on the DAW waveform thing. Use headphones, mono the two mics with one out of phase, and move one mic around until the sound is as thin and shrill as it gets.

Looking at the waveforms in the DAW is a great sanity check to make sure they're in phase on "tape".

I usually use a length of wire to measure the distance from the snare to the overheads; there's no need to use an actual tape measure since the key is that they're the same distance, not that you need to know that distance to the 1/4" or something. for guitars, I just set up the mics; they're usually too close to measure anything anyway.

I thought of trying to cancel the mics, however, because it's two different mics going through two different preamps(well, not always) you'll never get a perfect cancellation. But yes, shrill thin sound is enough..

scott wrote:I usually use a length of wire to measure the distance from the snare to the overheads; there's no need to use an actual tape measure since the key is that they're the same distance, not that you need to know that distance to the 1/4" or something. for guitars, I just set up the mics; they're usually too close to measure anything anyway.

Yep. I tape a piece of string to the center of the snare and use it to measure the distance to the mic. With amps I usually just eye-ball it. Haven't ever ran into any phase issues that were too serious. Whenever I mic an amp with 2 mics it is usually because I like one more for clean and one more for dirty. I usually don't sum the two but have in the past.