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@@ -34,14 +34,25 @@ breadcrumbs:
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- Use a ground loop isolation transformer.
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- Group the ground cables together so no currents get induced into the cables.
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- Use a resistor and/or a ferrite bead to limit AC current.
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-- Phantom power: Applies 48V to XLR3 (or similar) inputs, for powering mics and similar. Applying this to devices which aren't made for it can break them.
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-- Impedance: Basically resistance but for AC.
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-- Proximity effect: Increase of low frequency response when an audio source is close to a directional or cardioid microphone.
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+- Phantom power:
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+ - Applies 48V to XLR3 (or similar) inputs, for powering mics and similar.
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+ - Applying this to devices which aren't made for it can break them.
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+- Impedance:
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+ - Basically resistance but for AC.
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+- Proximity effect:
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+ - Increase of low frequency response when an audio source is close to a directional or cardioid microphone.
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+- Optimal SPL for mixing and listening:
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+ - Optimal SPL for normal music mixing and listening is around 75 dB SPL (conversational level) for small rooms and 85 dB SPL for large rooms.
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+ - The reason a specific SPL is optimal is due to equal-loudness contours, where the music actually sounds different at different volumes.
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+ - Mixing at high volume may help for getting the correct feel of the low end, however.
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- Equal-loudness contours:
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- The perceived loudness for a given SPL depends on the frequency.
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- This is typically visualized as equal-loudness contours, with frequency on the first axis, SPL on the second axis and a set of equal-loudness curves.
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- Fletcher–Munson curves is an early version of equal-loudness contours, but is still sometimes used to refer to the same thing.
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- This is why low-volume music sounds so bass-less and why e.g. car stereos typically provide a "loudness" setting to try to correct it for low volume levels (and make it sound terrible for normal volume levels).
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+- SPL meter weightings:
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+ - Type A is used for noise measurements and cuts off lower and higher frequencies compared to type C.
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+ - Type C has flatter response than type A and is often used for audio calibration.
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- Feedback:
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- Happens when sound is fed from speakers back into a microphone (accidentally), at a high enough "loop gain" that the feedback noise level quickly escalates to annoying/damaging levels.
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- Generally only happens at certain resonating frequencies, depending on the venue/room.
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@@ -50,5 +61,9 @@ breadcrumbs:
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- Use appropriate microphones, e.g. dynamic microphones pointing away from any (loud)speakers.
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- Use an equalizer to reduce the level for feedback-inducing frequencies. To find the frequencies, test the setup at loud levels to try to induce it, then measure which frequency it's happening at.
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- Don't use "feedback destroyers", they're crap.
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+- White and pink noise:
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+ - White noise has equal energy per frequency. The frequency-SPL curve is flat.
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+ - Pink noise has equal energy per octave. Since each octave has double the frequency of the previous (`log2(freq) = octave`), the frequency-SPL curve is decreasing. This makes pink noise appropriate for equalization for human hearing.
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+- Pan law: **TODO**
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{% include footer.md %}
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HON95