I am going through the how-to's now and re-aquanting myself with Room EQ Wizzard - but some questions linger for me:
1) Loopback and Sound Card Calibration
I understand the idea behind soundcard calibration pretty well - but the use of the loopback is a bit fuzzy to me (beyond the calibration). While I DO have a Dayton Omnimic V2 and I DO plan to actually measure room acoustics and loudspeaker response - my imediate use for REW will be measuring active EQ circuits. I fully understand: the sound card L-OUT will go to my active xover circuit and the output [from the xover] will be sent back to the L-IN.
But what about the R-OUT and R-IN? Do I leave these two simply open (not connected)? Or should they be jumped directly (direct loop: L-OUT -> L-IN) for some sort of reference? I think ARTA keeps the "second" channel in full-loop mode for the sake of comparing the input-vs-output of the signal under test. But not too sure about REW.
2) What the hell is "Mic Calibration" for?
Is that not what the factory calibration file (from Dayton) is for? Yes, I have a calibrated SPL meter - and can carry out the calibration. But I am not sure I understand the purpose of this if I already have a calibration file. Does this calibrate some other aspect of the microphone? Will this overwrite the calibration that was provided by my factory calibration file?
3) Have I found a bug with REW?
It seems every time I switch inputs (say, from "Omnimic" to "Sound Card Line In") I notice under the Devices section that - rather than re-use the config for the sound card - it adds a NEW entry. While the ever-growing list of "Input Devices" is only a minor inconvinience, the fact that every time you switch back to an input (and a NEW entry is made), that NEW entry does NOT have the path to the calibration file. Meaning - everytime you switch between inputs - you must manually go into the device config and ensure that the duplicated (new) device entry has the same calibration file specified.
I noticed this SAME thing happens to others on YouTube videos as well and would venture to say it is a bug that likely affects all but has just gone unnoticed?
Every. Single. Time.
This is latest version of REW as of October 28, 2023.
I am sure I will have more questions in the coming days and weeks but wanted to ask these questions since surely someone else has likely noticed or wondered the same but probably been too lazy to ask and wait for an answer.
-Dean
1) Loopback and Sound Card Calibration
I understand the idea behind soundcard calibration pretty well - but the use of the loopback is a bit fuzzy to me (beyond the calibration). While I DO have a Dayton Omnimic V2 and I DO plan to actually measure room acoustics and loudspeaker response - my imediate use for REW will be measuring active EQ circuits. I fully understand: the sound card L-OUT will go to my active xover circuit and the output [from the xover] will be sent back to the L-IN.
But what about the R-OUT and R-IN? Do I leave these two simply open (not connected)? Or should they be jumped directly (direct loop: L-OUT -> L-IN) for some sort of reference? I think ARTA keeps the "second" channel in full-loop mode for the sake of comparing the input-vs-output of the signal under test. But not too sure about REW.
2) What the hell is "Mic Calibration" for?
Is that not what the factory calibration file (from Dayton) is for? Yes, I have a calibrated SPL meter - and can carry out the calibration. But I am not sure I understand the purpose of this if I already have a calibration file. Does this calibrate some other aspect of the microphone? Will this overwrite the calibration that was provided by my factory calibration file?
3) Have I found a bug with REW?
It seems every time I switch inputs (say, from "Omnimic" to "Sound Card Line In") I notice under the Devices section that - rather than re-use the config for the sound card - it adds a NEW entry. While the ever-growing list of "Input Devices" is only a minor inconvinience, the fact that every time you switch back to an input (and a NEW entry is made), that NEW entry does NOT have the path to the calibration file. Meaning - everytime you switch between inputs - you must manually go into the device config and ensure that the duplicated (new) device entry has the same calibration file specified.
I noticed this SAME thing happens to others on YouTube videos as well and would venture to say it is a bug that likely affects all but has just gone unnoticed?
Every. Single. Time.
This is latest version of REW as of October 28, 2023.
I am sure I will have more questions in the coming days and weeks but wanted to ask these questions since surely someone else has likely noticed or wondered the same but probably been too lazy to ask and wait for an answer.
-Dean
Oh.. and gonna add a #4...
4) My "soundcard" is currently a Lexicon Omega - how is hardware mixing handled?
Here is my concern. The soundcard is calibrated - I got that. The mic is calibrated - I got that, too.
Now let's say I decide that I want to use a calibrated XLR microphone (instead of the USB Dayton Omnimic).. Would I have to apply the calibration file to the input of the Lexicon Omega? Keep in mind: there is no separate "MIC IN" with the USB interface itself - you simply adjust which input you want mixed into the "line in" from the front panel. That mixing is done in analog (with the hardware) before it is ever sent to the PC.
When doing a room measurement, I would need to apply the MIC calibration file (mic plugged into the Omega) and if/when I switched back to measuring a line-level crossover circuit, I would need to remove the calibration file - no?
-Dean
4) My "soundcard" is currently a Lexicon Omega - how is hardware mixing handled?
Here is my concern. The soundcard is calibrated - I got that. The mic is calibrated - I got that, too.
Now let's say I decide that I want to use a calibrated XLR microphone (instead of the USB Dayton Omnimic).. Would I have to apply the calibration file to the input of the Lexicon Omega? Keep in mind: there is no separate "MIC IN" with the USB interface itself - you simply adjust which input you want mixed into the "line in" from the front panel. That mixing is done in analog (with the hardware) before it is ever sent to the PC.
When doing a room measurement, I would need to apply the MIC calibration file (mic plugged into the Omega) and if/when I switched back to measuring a line-level crossover circuit, I would need to remove the calibration file - no?
-Dean
1) Loopback is used to get absolute impulse from the DUT. That is - if REW uses a loopback to eliminate the shortest "output / input" path, then anything else is flight time for the measurement (through amplifier, or crossover and speaker to distance to mic). it allows us to assess acoustic offset differences between multiple devices under test (assuming you aren't moving your measurement mic).
2) Mic calibration allows your non-linear / lumpy microphone response to have a curve applied to it so it measures "flat". This is separate to any soundcard or amplifier calibration which does the same for those output devices (but usually modern soundcards and amplifiers are flat enough to not need that)
3) Best ask John I think via the REW forum on I can't remember where
2) Mic calibration allows your non-linear / lumpy microphone response to have a curve applied to it so it measures "flat". This is separate to any soundcard or amplifier calibration which does the same for those output devices (but usually modern soundcards and amplifiers are flat enough to not need that)
3) Best ask John I think via the REW forum on I can't remember where