SPL too perfect…

[Smalllotus]

Hi there,

I start with REW and I have a bug with the measurements I took. As you can see my answer doesn't make any sense... I have the microphone set up correctly and the whole procedure seems to work fine. I use loopback and i'm wondering if REW listens to the microphone

I am on Ventura with a MacMini M1 and REW 5.20.14

Soundcard : UAD Volt 276

 

[John Mulcahy]

I guess the clue is in the name "Loopback audio" for input and output, you are just measuring a loopback connection. Why not select the Volt directly as the input and output device?

 

[Smalllotus]

Hi john.

If I use my Volt I have two cases. Either it's too loud or it's too quiet. There are boxes (control output volume & control input volume) I can't check on or off. See the attachments. So I can't calibrate the soundcard…

 

[John Mulcahy]

Use the volume controls on the interface and/or in the OS (e.g. in Audio Midi Setup). Make sure you disable all monitoring, the input signal must not be routed to the output.

 

[Smalllotus]

here's the maximum level I can have… I still have feedback… How can I disable it ? OSX Ventura

many THX in advance

 

[John Mulcahy]

From the Volt manual looks like you keep pressing the "Direct" monitoring button until the light goes off.

Have you connected a cable from output to input so you can do the soundcard calibration?

 

[Smalllotus]

the direct monitoring is off, of course, but I still have a feedback. I have this message when i connect a cable from output to input.

 

[Smalllotus]

oops…

 

[John Mulcahy]

The variations in test2.mdat are caused by some monitoring being active, so if direct monitor is off there must be some software monitoring enabled.

 

[Smalllotus]

I've tried with another soundcard. I don't know why there's monitoring… all my apps are closed, loopback is unactive. This should be the sound card measurement...

 

[Smalllotus]

Is it normal that I can't change this? see attachment... I can't control output

 

[John Mulcahy]

Yes, those controls are disabled on macOS. Level is not controlled using those settings in any case, they just reflect the OS controls. For a soundcard calibration the measurement signal is generated at the level set in the "Sweep level" control. In normal use to change the level of signals coming from REW use the "Level" controls on the Measure dialog or signal generator.

 

[John Mulcahy]

I've tried with another soundcard. I don't know why there's monitoring… all my apps are closed, loopback is unactive. This should be the sound card measurement...

That measurement just shows mains hum pickup. The input channel was L and the output channel was 2, did you have a loopback cable from output 2 to the L input?

 

[Smalllotus]

yes, i do, see attachment… it looks good

 

[Smalllotus]

I've just unplugged one output (the first output), and I made measurement, is it correct ?

 

[John Mulcahy]

Yes, looks fine, though the system you measured inverts polarity (which you can see by looking at the impulse response graph with the Y axis set to percent).

 

[Smalllotus]

Thank you very much, I'll check the polarity... Is this due to the use of a mono jack cable?

 

[John Mulcahy]

Shouldn't be, more likely to be in whatever the signal is going to or speaker connections swapped.