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Room Measurement Advice

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Room Measurement Advice

Postby UncleFester » Mon May 13, 2019 7:33 pm

Hello To You All.

I am in need of a little advice concerning room measurement.

First a note about the setup.

I am using REW through a RME ADI-8.
This goes to a Presonus Monitor Station V2 (the volume control of which is used to set the in-room SPL level).
This then goes to a pair of Event TR8's that have a max SPL of 108dB.
This is being measured through a calibrated CSL EMM-6 measurement mic using a 90 degree (off axis) calibration file as the mic is pointed at the ceiling.
This then goes through a FMR RNP preamp with a gain of 48dB (front panel indication, not measured).

REW has been calibrated with an SPL meter (C-Weighted & Slow) using the pink noise test signal to give an in room SPL of 75dB.
This gives a figure of around 83dB (peak hold) when using the logarithmic swept sinewave test signal.

The ambient noise level in the room is around 60dB. Which seems a little high to me but is probably due to the DAW computer being in the same room.

To my thinking this gives me the following SPL headroom when perfoming the measurements:

SPL Headroom = Swept Sinewave Test Signal - Ambient Room Noise = 83 - 60 = 23dB

Do I have enough headroom to make a proper measurement?

Thanks to anyone who takes the time to respond.
UncleFester.
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Re: Room Measurement Advice

Postby Hugh Robjohns » Mon May 13, 2019 8:18 pm

If that's an accurate figure your ambient noise level is quite high. 60dB SPL is quiet conversation level.... A half decent semi-pro listening/mix room really should be under 50dB SPL and ideally under 40dB SPL.

H
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Re: Room Measurement Advice

Postby UncleFester » Wed May 15, 2019 1:02 am

Hello Hugh and thank you for your response.

I had another go at measuring the in-room ambient noise level to make sure I hadn't done something daft. The SPL meter was pointing at the ceiling in the listening position as before.

This time I took the measurement at night when it's a little quieter (wife and kids asleep) and got the following figures:

57dBC (C-Weighted & Slow).
36dBA (A-Weighted & Slow).

This gives at best 26dB SPL headroom using the C-Weighted figure.

Is this enough headroom to make a proper measurement?
How large on average are modal nulls in a typical small room in a house?

Without enough SPL headroom I am worried the deep nulls will get lost below the in-room ambient noise level. This is particularly important as I want to look at waterfall plots for the room.

Thanks for the help so far.
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Re: Room Measurement Advice

Postby Hugh Robjohns » Wed May 15, 2019 10:50 am

Yes, that will be fine...
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Re: Room Measurement Advice

Postby UncleFester » Thu May 16, 2019 7:41 pm

Thank you for your help Huge. Very much appreciated.
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