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  1. Measurement mic gain settings

    #1
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    Default Measurement mic gain settings

    Hi,
    First post on this forum and hope you guys could help me here. When setting gains for measuring mic, do I leave it as it is or should I increase it to match with the ref signal when moving it further back from the speaker? Trying to EQ my system to the room and not sure where to place the mic, using ECM8000 atm. Should I leave it within 1m for 1st measurement as a good SNR reference then move it to various positions where people will be sitting. Should I just measure half of the room (right if measuring right speaker) or should I place mic on the left half of the room as well? I thought if I cross to the left half, when playing both speakers, I would have some frequency cancellations and hence not a good reading. Do I point the mic at centre stage or to the speaker, but most importantly how loud should the signal be and do I up the gain of the mic when putting further away from the speaker?
    Hope that make sense and any help will be greatly appreciated.

  2. Re: Measurement mic gain settings

    #2
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    Default

    Anyone able to help me with this problem?

  3. Re: Measurement mic gain settings

    #3
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    Hello Aaronius,

    Your questions are complex, most with no definite answers because it depend on the situation. I'll try to do my best. Please be aware that this is based in my opinion and methods. Probably there are as many answers as there are tuning experts out there. Also, this doesn't mean it is all the considerations and methods I use, just the ones I believe will clarify your queries the best I can at this time.

    When setting gains for measuring mic, do I leave it as it is or should I increase it to match with the ref signal when moving it further back from the speaker?

    As usual, it depends. If you are eqing a system with multiple speakers in different subsystems so you can adjust levels and eq independently (i.e. a line array with zones for near, mid and long throw, or a main system plus delay fills, or even a combination of both), it would be better in my experience to leave your preamp gain as it is so you can properly tackle gain, eq. and HF tilt as you are measuring further back.

    If you have a system that you can't treat separately for each audience zone (or throw in this example), it might be a good decision to add gain as you go further back, if only to conserve the preamp S/N ratio as if you want the traces on top of each other for comparison you can always offset each of them within smaart without touching gains. If you want to do averaging, you can select power average to have them normalized even if they have different levels, or deselect it and play with the gains to have the more important ones play a bigger role in the averaging. Please remember that doing averages is tricky, in the sense that you should not average signals that are grossly different as the result will be bad everywhere. Such different curves in different zones point out problems within the coverage of the system in my opinion. Better to try to get a better sound in most areas and if you can't put fills in the "worse" areas, try to minimize them by better pointing the speakers, and use a solution that will even the system for most of the audience or at least have reasonably expected differences (some times you can't avoid losing HF at the end of the venue, and this would be kind of expected to the patrons, whereas too much HF for the front is super annoying)

    Trying to EQ my system to the room and not sure where to place the mic, using ECM8000 atm. Should I leave it within 1m for 1st measurement as a good SNR reference then move it to various positions where people will be sitting.

    1 meter for first measurement is not considered a good reference. You are too close to the speaker to actually capture its best behavior. Rule of thumb is to be at least 3 times as far as the biggest dimension of the speaker your are measuring is (That I took from Synaudcom classes). Usually, I measure being around +/- 15║ of speaker axis horizontally, at least one third of the way from the length of the room, where the audience is going to be as my reference. Or it could be at FOH, if FOH is in a correct position. (I had seen it behind stairs, covered in vegetation, in the back corner of the room, on a side balcony and worse!) You need to choose your mic placements to have as much direct sound as possible to have good coherence (which basically is your S/N in transfer function)

    Should I just measure half of the room (right if measuring right speaker) or should I place mic on the left half of the room as well? I thought if I cross to the left half, when playing both speakers, I would have some frequency cancellations and hence not a good reading.

    My take is to first measure both sides (independently) to make sure they sound equal (which can be a simple measurement or a complex one depending on the system), and then focus on one side copying the adjustments to both. Never measure with both sides on as it will destroy your coherence and invalidate the results. In any case, theoretically at least, L and R should be de-correlated in the mix if you want separation, or have little overlap if you re mixing in mono and using them for zoning. Then try to explain that to the mixing engineer

    Do I point the mic at centre stage or to the speaker, but most importantly how loud should the signal be

    Depending on the mic, you should either point it to the speaker (with a free field calibrated microphone), or to the ceiling (with a diffuse field calibrated microphone). You can buy some mics with both calibration curves though. If that's the case, I rather use the free field one and point it at the speaker unless I'm measuring for noise. Even the best omni measurement mic will have some directionality on HF as it is dictated by capsule size, and it will not affect the diffuse field a lot since reflections rarely have full frequency response.

    but most importantly how loud should the signal be

    you should be as far away from the noise floor as possible. I don't remember the particular recommendations (I believe it is that you have to be at least 20dB over the noise, but I could be mistaken). I shoot to have at least that separation.

    do I up the gain of the mic when putting further away from the speaker?

    I think this was answered above.

    Anyone able to help me with this problem?

    Is not a problem, is a lot of different questions. I believe no one answered before because you covered too much to be answered easily, and the answers leave you exposed to "opinion differences". I welcome this opinions as they will (when they appear) help me enrich my methods, or at least understand what others are doing. Don't be so hard on us, we are busy people trying to be out there tuning every day :-)

    I hope this helps. GS
    Last edited by gluis; May 23rd, 2019 at 04:03 PM.
    Give a man fire and he is warm for a day, set him on fire and he is warm his whole life.

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