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[mykillk]

In the near future I'm going to move away from using a simple HDMI to my receiver. Instead, I'm going to get something like an Asus Essence ST + H6 combo to do the decoding on the PC and output via RCA to my receiver. The big reason is the amazing level of calibration that is possible using a setup like this.

I have two subwoofers. I'd like to be able to independantly calibrate them, so each would need its own output from the sound card.

The $64,000 question: Could I use one of the surround-back outputs as a secondary subwoofer output and with the remaining surround-back ouput have a 6.2 setup?

[Matt]

The $64,000 question: Could I use one of the surround-back outputs as a secondary subwoofer output and with the remaining surround-back ouput have a 6.2 setup?

Sure.

You're only limited by the number of output channels you have.

I run a 5.2 system at home (but the 0.2 go to a single dual voice-coil subwoofer).

Some users like TheLion are running like 24 output channels.

You can do a lot with 'Parametric Equalizer' in Media Center.  If there are things you can't do but want, you should ask because we might be able to add them.

You can also explore convolution packages for advanced routing and calibration.

[mykillk]

You can also explore convolution packages for advanced routing and calibration.

I'm drooling with anticipation over the arrival of my UMM-6 USB calibration mic. Should be here within a week. Should keep me busy for quite a while given how difficult and complicated this advanced calibration stuff looks  

Quick Q: What would be the best method for combining the surround-back Left and Right channels into a single surround-back channel? I'm worried there might be clipping if the levels coming out of both the surround-backs are high. Or is that already handled internally in the MC18 audio system?

[mwillems]

In the near future I'm going to move away from using a simple HDMI to my receiver. Instead, I'm going to get something like an Asus Essence ST + H6 combo to do the decoding on the PC and output via RCA to my receiver. The big reason is the amazing level of calibration that is possible using a setup like this.

I have two subwoofers. I'd like to be able to independantly calibrate them, so each would need its own output from the sound card.

The $64,000 question: Could I use one of the surround-back outputs as a secondary subwoofer output and with the remaining surround-back ouput have a 6.2 setup?

I've wondered this myself (what's the best way to get volume levels correct with freestyle channel mixing).  I think JRiver's clip protection should engage to prevent any actual clipping. Or is the adaptive clip protection what you're trying to avoid? 

If so (and you're using internal volume) you could resolve it by setting your maximum internal volume somewhat lower than it currently is (three or four dB).  That way, there'd be some additional "headroom" for the slightly higher peaks coming out of the rear speaker. 

Unless I'm confused, combining the two channels should only result in a 3dB gain in maximum volume over the baseline, so it should be easy to give it some additional headroom. Or if you already have internal volume set low for calibration purposes, you may already have all the overhead you need.  For example, 77 on the internal volume slider is my calibration point (the point where my amps are driving my speakers to 83dB at the listening position), which gives me another 10 or 12 dB of overhead for DSP.

[Matt]

You can add two channels together using a 'Mix channels' filter in Parametric Equalizer.

For clipping, I would recommend switching to Internal Volume so you always have plenty of headroom:
http://wiki.jriver.com/index.php/Volume#Internal_Volume_Headroom

If that doesn't work for you, you could use an 'Adjust volume' Parametric Equalizer filter to bring down all the channels.

[mojave]

You can do the same calibration with HDMI as you can with analog output. Don't bitstream and turn off any processing in the receiver. Some receivers still convert the analog signal to digital internally because they control the volume digitally. Keeping the signal digital via HDMI can sometimes be better.

It is best to mix the rear channel first with Parametric Equalizer; perform bass management, distance, and level adjustment next with Room Correction; and finally copy the sub channel to the empty rear channel in Parametric Equalizer 2. In Room Correction JRiver will mix the redirected bass with the LFE and make sure the sub levels are correct. After this is done, then you copy the sub to the empty rear channel. That way you know it is identical to the first sub output.

In the attachments I show the two PEQ setups. You can see on the left how I have ordered the DSP.

[mwillems]

You can do the same calibration with HDMI as you can with analog output. Don't bitstream and turn off any processing in the receiver. Some receivers still convert the analog signal to digital internally because they control the volume digitally. Keeping the signal digital via HDMI can sometimes be better.

It is best to mix the rear channel first with Parametric Equalizer; perform bass management, distance, and level adjustment next with Room Correction; and finally copy the sub channel to the empty rear channel in Parametric Equalizer 2. In Room Correction JRiver will mix the redirected bass with the LFE and make sure the sub levels are correct. After this is done, then you copy the sub to the empty rear channel. That way you know it is identical to the first sub output.

In the attachments I show the two PEQ setups. You can see on the left how I have ordered the DSP.

Matt and Mojave, I have a quick question:  you suggest setting the level adjustment for the speakers after combining the two rear speakers, but what is the target volume for the now unified rear speaker in calibration?  Should it be the same as the other speakers, or louder?  By combining two channels, shouldn't there be some increase in volume so that the original mastering of the program material retains it's balance with the other speakers?  Or should you just output pink noise to either one of the rear speakers [EDIT: should read "channels," sorry] (but not both) and make that level with the rest of the system?

[mykillk]

You can do the same calibration with HDMI as you can with analog output. Don't bitstream and turn off any processing in the receiver. Some receivers still convert the analog signal to digital internally because they control the volume digitally. Keeping the signal digital via HDMI can sometimes be better.

It is best to mix the rear channel first with Parametric Equalizer; perform bass management, distance, and level adjustment next with Room Correction; and finally copy the sub channel to the empty rear channel in Parametric Equalizer 2. In Room Correction JRiver will mix the redirected bass with the LFE and make sure the sub levels are correct. After this is done, then you copy the sub to the empty rear channel. That way you know it is identical to the first sub output.

In the attachments I show the two PEQ setups. You can see on the left how I have ordered the DSP.

Wow, that's neat. Very informative, I will have to try this. About this conversin of analog audio to digital for volume management, does it tend to be more typical with certain brands? I have an Onkyo TX-NR709

[mojave]

Matt and Mojave, I have a quick question:  you suggest setting the level adjustment for the speakers after combining the two rear speakers, but what is the target volume for the now unified rear speaker in calibration?  Should it be the same as the other speakers, or louder?  By combining two channels, shouldn't there be some increase in volume so that the original mastering of the program material retains it's balance with the other speakers?  Or should you just output pink noise to either one of the rear speakers (but not both) and make that level with the rest of the system?

mykillk is doing a 6.2 system. Are you also doing something similar? You asked about combining the rear channels, but now you mention having two rear speakers. Can you explain more how you are setting things up and mixing channels.

Wow, that's neat. Very informative, I will have to try this. About this digital volume management, does it tend to be more typical with certain brands? I have an Onkyo TX-NR709

If you can do any type of DSP in the Onkyo to the analog input, then it is converting to digital in the signal chain. For example, can you change level settings for each speaker on analog inputs or can you turn on Audyssey or EQ for analog inputs? If so, then it has to be doing an A/D conversion.

[mwillems]

mykillk is doing a 6.2 system. Are you also doing something similar? You asked about combining the rear channels, but now you mention having two rear speakers. Can you explain more how you are setting things up and mixing channels.
If you can do any type of DSP in the Onkyo to the analog input, then it is converting to digital in the signal chain. For example, can you change level settings for each speaker on analog inputs or can you turn on Audyssey or EQ for analog inputs? If so, then it has to be doing an A/D conversion.

I was only asking about his use case (combining two rear channels to output to a single rear speaker in a 6.2 arrangement).   I guess I didn't phrase my question very elegantly: what I meant to ask was what volume level should he be calibrating his newly combined single rear channel to, and how should he go about doing that?  You just said to do "level adjustment" in room correction, but how would he do that?  Play the level tone on only one of the rear channel outputs?  Play pinknoise out of both?  Is the target level the same as for the fronts/center/other channels? Does that make sense?

I've just had a hard time grasping volume calibration in systems that include both manually mixed channels and unmixed channels in JRiver.  My instinct tells me the doubled channels should be louder, but how is that accounted for in calibration?

[mykillk]

For clipping, I would recommend switching to Internal Volume so you always have plenty of headroom:
http://wiki.jriver.com/index.php/Volume#Internal_Volume_Headroom

If that doesn't work for you, you could use an 'Adjust volume' Parametric Equalizer filter to bring down all the channels.

Excellent just what I needed. Along with the DSP Visualizer to monitor the levels.

[mykillk]

Grr, I just realized my plan to use the rear right as a secondary subwoofer output won't work. My receiver does not allow "Full" crossover on rear speakers, only on the Fronts. The lowest the crossover goes is 40hz and my sub can go lower than that.

Maybe I could use my front right as the secondary subwoofer output and use rear right as front right? Or would it be better to go with the sound card analog output and route the subwoofer channels directly to the subs instead of through the receiever?

EDIT: Well I did some testing and it seems like when using "Pure" or "Direct" audio modes it disables the crossover frequencies on the receiever. Nice, now I can still use the rear right as a sub output!