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I can't even get a loop back?
It looks like the XLR outputs can be switched from mic to line level, so all you need is a cable with a female XLR to a 1/4" TS, or XLR to RCA, and connect between the line out and either line or AUX in.

That said, a soundcard calibration might not even be required for using the HDMI output; I don't know enough about it to say. Perhaps John can comment.

Regards,
Wayne

 

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There is no roll-off for the HDMI output (digital path), but roll-off tends to be mostly in the input path. Can just skip it with that card though, spec is within 0.5 dB down to 10 Hz.
 

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Discussion Starter #4 (Edited)
OK, sounds good. Is there a way to make sure I am getting correct measurments, eg all the HDMI settings are set correctly and the USBPre2 settings in the PC are set correctly?

BTW John, REW in Japanese windows OS does not display characters correctly, but on some pull down menus it does??? Upon closing it shows Japanese characters fine.

check out the letters in the red circle below.
 

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OK, sounds good. Is there a way to make sure I am getting correct measurments, eg all the HDMI settings are set correctly and the USBPre2 settings in the PC are set correctly?
Quickest is to make some measurements and post them here for us to take a look at.

BTW John, REW in Japanese windows OS does not display characters correctly, but on some pull down menus it does??? Upon closing it shows Japanese characters fine.
There are probably a few (or more than a few) things I should be doing for better internationalisation support, but the nights are short and my todo list is long... :)
 

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Discussion Starter #7
How are these two graphs,

The first one is without EQ @ low SPL with the longest time taken for the measurement and the second one is at higher SPL levels with @ half speed.

So do these graphs look OK?

I am having trouble stopping clipping in the USBPre2 , when I go for the higher SPL readings??? How do I enable it so I can take higher SPL measurements. The subs are still not being pushed at this level and I want to apply a better EQ curve. Cheers.



 

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Discussion Starter #9
What would the reason be that I have to turn the gain on the preamp nearly to max when trying to get -12db when setting levels in the preferences? Then when I go to make a measurement, it says it clips, so I have to turn the gain down. And this is on low SPL measurements. Something is clearly wrong, any ideas?
 

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I also have a USBPre2 which I'm using to successfully make measurements with REW. I'm not experiencing the problems you're describing with my setup, but I'm using the USBPre2 for both input and output sources, whereas if I understand you right, you're using HDMI for the output and only using the USBPre2 as the mic input?

How exactly do you have everything connected and configured?
 

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Discussion Starter #11
I also have a USBPre2 which I'm using to successfully make measurements with REW. I'm not experiencing the problems you're describing with my setup, but I'm using the USBPre2 for both input and output sources, whereas if I understand you right, you're using HDMI for the output and only using the USBPre2 as the mic input?

How exactly do you have everything connected and configured?
I have setup this way: mic in XLR input 2 > USB > PC > HDMI > Reciever
I have the dip switches 9 & 10 set to 48v Phantom on A , Everything else on A & B is switched off.
I have the unit switched to "Pre" not "PC". The two small popout knobs are turned to infinity and the other to "Pre".

I can't even get a sound card calibration. I connected a female XLR to the right Mic out and the 1/4 to Line 2 in. But this does not give a loop??? Any ideas?
 

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There's actually two ways of doing loopback on the USBPre2, either you can do a physical loopback via the back panel XLR output into the side panel line in, like you are trying to do, or you can switch channel 2 into an internal loopback mode by toggling the channel 2 input selector until it indicates 'loop'.

I remember when doing the external loopback it took me a few goes to work out whether the left or right main output was channel 1 or 2 - so it was possible to mix them up and not actually get a loopback at all because you were trying to loop channel 1 into 2 or vice versa. For my actual tests, I use channel 2 in internal loopback for the timing reference and use channel 1 for the mic, and also my output test signal.

Getting the loopback test working with a physical cable first is probably a good way to check you have everything set right. Things to note :

The input selector on the channel you're doing the loopback test on should be set to 'line'
The metering toggle can be set to either pre or PC, in fact it's useful swapping between them while you're running the test to see that you're getting audio out from the PC, and audio in from the pre. Note that with the default dipswitch settings, it automatically switches to monitoring PC whenever you have the USB plugged in. I find this a pain, and so I've set dipswitch B4 to make that always manually selected.
Adjusting the output gain on the tiny little knob is annoying, so I've set dipswitch B5 to make the large headphone knob control the output gain, which is much less annoying.

Given all of those, and selecting the right combination of channels, you should be able to get a loopback test and soundcard calibration to work. The results should be *very* flat (it's a lovely bit of kit :))

Report back on how you get on with that, and then we can run over the actual REW sweeps via HDMI and work out why that's not working as you expect?
 

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Discussion Starter #13
Adjusting the output gain on the tiny little knob is annoying, so I've set dipswitch B5 to make the large headphone knob control the output gain, which is much less annoying.
Are you talking about the knob circled in red or yellow in the below pic? I can only get the gain to go up and down by adjusting the knob in yellow.

Do you take measurements with input selector on the channel set to 'Line' ?

 

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The knob circled in red on your image controls *output* gain (volume), if you're using the USBPre2 as the source of your audio. Dipswitch B5 swaps that knob with the larger one just to the right of it labelled 'Phones', giving you a more convenient knob to control output volume with.

I believe you've said that you're using HDMI out for your actual testing so it won't make any difference for that since output volume will be controlled by your HDMI output volume settings and whatever your receiver/amp is set to.

For taking actual in room measurements, I have the input selector for the channel I'm using (1 in my case) set to 'Mic' because the input is a microphone, is plugged into the mic input, and needs the extra signal amplifications that microphones do.

I only use the 'Line' input when doing a loopback test.

Can you get the loopback test working as described in my previous message?

Reading back over the problems you're discussing, I'm wondering if you're getting the level setting process right. When you do 'Check Levels' you should be adjusting your output volume on the HDMI output and the receiver to produce a reasonable volume from the speakers (if you're checking that with a sound level meter, it should be 75dB or whatever you're aiming for). The input level should be around -18dB as per the instructions - you shouldn't be trying to set it for -12dB or higher as you then have a tendency to get clipping when there are peaks in the room response at particular frequencies, which may be what you're experiencing?
 

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Discussion Starter #15
The knob circled in red on your image controls *output* gain (volume), if you're using the USBPre2 as the source of your audio. Dipswitch B5 swaps that knob with the larger one just to the right of it labelled 'Phones', giving you a more convenient knob to control output volume with.

I believe you've said that you're using HDMI out for your actual testing so it won't make any difference for that since output volume will be controlled by your HDMI output volume settings and whatever your receiver/amp is set to.

For taking actual in room measurements, I have the input selector for the channel I'm using (1 in my case) set to 'Mic' because the input is a microphone, is plugged into the mic input, and needs the extra signal amplifications that microphones do.

I only use the 'Line' input when doing a loopback test.

Can you get the loopback test working as described in my previous message?

Reading back over the problems you're discussing, I'm wondering if you're getting the level setting process right. When you do 'Check Levels' you should be adjusting your output volume on the HDMI output and the receiver to produce a reasonable volume from the speakers (if you're checking that with a sound level meter, it should be 75dB or whatever you're aiming for). The input level should be around -18dB as per the instructions - you shouldn't be trying to set it for -12dB or higher as you then have a tendency to get clipping when there are peaks in the room response at particular frequencies, which may be what you're experiencing?
I finally made a calibration of the sound card via the cabled option. I can't seem to make one with the loop feature.

Also with my setup, both the knob circled in yellow and the volume on the receiver can change the levels. Is this normal?
 

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I finally made a calibration of the sound card via the cabled option. I can't seem to make one with the loop feature.

Also with my setup, both the knob circled in yellow and the volume on the receiver can change the levels. Is this normal?
Well it's good that you have a calibration via the loop, that suggests everything is working properly. How did it look, it should be very flat indeed?

The knob circled in yellow adjusts the amount of amplification applied to the signal received by the microphone, and thus for any particular volume out of the receiver will adjust the level seen by REW's input up and down. The receiver obviously affects the output volume, so again, you expect that to adjust the input seen by REW up and down as more or less sound is received by the microphone. Is that what you mean?

Later today I'll see if I can take some photographs of how things are set up on mine by way of comparison.
 

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Right, as promised, here are some images of how my USBPre2 is connected and configured for REW.

Front panel:


Front panel detail - note how the input selectors are configured and the monitoring:


Inputs - Mic in from my measurement microphone into channel 1:


Outputs - Aux out to feed my receiver, and USB to my computer:


Hope that helps understand how I have it configured. Yours should be very similar except you won't need the output because you're doing that via HDMI as I understand it.

Also, are you using the Sound Devices ASIO driver on windows or the native WDM? And have you got the latest firmware installed on the USBPre2?
 

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Discussion Starter #18 (Edited)
Hey
That makes things a whole lot easier , thanks for the pics.
I am not using the USBPre asio driver, Should I? I am using ASIO4all at the moment.
And I am not sure if I have the latest firmware either????

Dave
 
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