Home Theater Forum and Systems banner

1 - 7 of 7 Posts

·
Premium Member
Joined
·
129 Posts
Discussion Starter #1
I'm using a USB interface by Native Instruments for REW measurements (it's called the Konnect Six). For convenience so I can easily feed any of my channels I'm using its SPDIF output to feed my Z Sys router, and then I can route it to the digital inputs of all channels of my DACs, as I can route this SPDIF output to multiple destinations using the router.

Now I want to measure time of flight of the subwoofer to check its time alignment with the satellites, and for that I need the loopback function. I do not need to know the EXACT distance that the loudspeakers are from the microphone, but I do need a consistent loopback so REW can do its work and compare the time of arrival from the sub to that of the main speakers.

Now comes the rub. How to get an analog feed to the loopback input. If I could get REW to feed multiple outputs at once then I could take an analog output of the interface and patch it to the loopback input. Presto: Done. And no extra hardware needed.

I can think of a trick, but it requires more hardware: I can feed a spare DAC and then feed its line output to the loopback input. Kind of a waste of hardware if instead I could just feed the SPDIF output and an analog output of the interface at the same time.


P.S. I once saw a post I think by John relating to a freeware ASIO mixer that can be downloaded that may solve my problem but I can't seem to find it after a zealous search.
 

·
Premium Member
Joined
·
6,711 Posts
By default REW puts its test signal on both left and right channels of the selected output (when using the Java drivers), so there are two output signals available. If the ASIO drivers are used the test and reference signals can be selected independently, but they have to be from the same ASIO device. A potential workaround for that is to create a composite ASIO device using ASIO4All, but from some quick testing I did a couple of weeks ago it does not appear that separate devices maintain the same relative sync on successive measurements, so that method did not deliver a stable timing reference when I tried it. Easiest is probably to use the Java drivers and use your router to pipe one of the REW stereo output channels to a fixed analog output and the other to the channel to be measured.
 

·
Premium Member
Joined
·
129 Posts
Discussion Starter #3
By default REW puts its test signal on both left and right channels of the selected output (when using the Java drivers), so there are two output signals available. If the ASIO drivers are used the test and reference signals can be selected independently, but they have to be from the same ASIO device. A potential workaround for that is to create a composite ASIO device using ASIO4All, but from some quick testing I did a couple of weeks ago it does not appear that separate devices maintain the same relative sync on successive measurements, so that method did not deliver a stable timing reference when I tried it. Easiest is probably to use the Java drivers and use your router to pipe one of the REW stereo output channels to a fixed analog output and the other to the channel to be measured.
Thanks for always being there, John! I'll try the ASIO and see if I can route one channel at a time as you describe!

Not realizing this, I just installed JACK on my PC and boy is it complicated! And scary to boot. But using Jack I was able to simultaneously route REW to both the SPDIF and analog outputs of my interface, and then with an analog cable patch an analog output back to an analog input, and PRESTO --- I have loopback.

But I'd much rather get rid of JACK, it looks like a curse on the Operating system and every time I'd have to launch REW I'd have to launch Jack and make sure it is patched. I'll let you know if the ASIO driver thing works. Stand by and thanks.
 

·
Premium Member
Joined
·
129 Posts
Discussion Starter #4
Well, I tried the ASIO. Is it possible for you to feed multiple outputs at once? If you can feed both Left and Right of the SPDIF at the same time it will avoid my having to make multiple trips to the preferences every time I want to measure a different channel, and as you know, we switch between measuring left and right speakers quite often.

The problem for me is that you can assign only ONE channel of the selected output at a time with the ASIO, but with JAVA you went out to both. So I have to go back to the preferences to change the channel it's feeding out, with ASIO. It would be nice to be able to choose the channel of the output at the time of making the measurement, OR, in the preferences, to feed both channels, because I can mute any speaker in the Avocet monitor controller, so I can go quickly through measurement of all speakers. Other users may not have individual speaker muting controls, and so it would be better if REW can select the channel output on the measurement page. And if you have a multichannel ASIO interface, to select any or all channel outputs on the measure page, because that's the page you live on, not the preferences.

For example, my digital router, being an AES router, routes both channels at once and has no "channelization". My routes are stereo pairs, LF/RF, C/LFE, and LS/RS and I can digitally route the interface SPDIF to all six channels at once, but no channelization. So when using ASIO with SPDIF I can only feed the "left" or the "right" channel of those pairs at a time, unless you are able to choose to feed both channels in the prefs. It's not the most ergonomic place to use the preferences page to select the channel, but of course it's useable right now and I'm having fun already with the loopback!
 

·
Registered
Joined
·
114 Posts
If you use JRiver, you can use its loopback by using File > Open Live and selecting WASAPI Loopback. This lets you route REW through JRiver. There are further directions at JRiver's forum. Now you can use the Parametric Equalizer DSP in JRiver and add Order Channels. This lets you easily change the left channel output to the other channels and you can easily measure all speakers with REW.
 

·
Premium Member
Joined
·
129 Posts
Discussion Starter #6
If you use JRiver, you can use its loopback by using File > Open Live and selecting WASAPI Loopback. This lets you route REW through JRiver. There are further directions at JRiver's forum. Now you can use the Parametric Equalizer DSP in JRiver and add Order Channels. This lets you easily change the left channel output to the other channels and you can easily measure all speakers with REW.

Thanks. I haven't even installed JRiver yet, that's how far "behind the curve" I am at this moment. Will this feature work with ASIO as my Lynx AES-16 is running with the ASIO driver. Regardless, Mojave, I think the feature should be built into REW's measure screen, where you should be able to choose the output channel(s) you want to feed. I didn't get this idea out of the blue, by the way, I've been using this approach successfully and conveniently in Fuzzmeasure. The idea is ergonomics, the choices you have to constantly change should be on the screen that you are working in (the Measure screen), without having to navigate and jump around.

BK
 

·
Registered
Joined
·
114 Posts
Yes, it will work with your Lynx. However, you have to have another audio device setup as the default audio device. You send the REW output to the default device, it is intercepted by JRiver and then routed to the output setup in JRiver (such as the Lynx). I set the motherboard's audio as the default. In reality it is never used.

I use either the parametric EQ in JRiver or an Audiolense convolution filter, so I always measure through JRiver anyway when using REW.
 
1 - 7 of 7 Posts
Top