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Author Topic: Feature Request: Mixing Sub-channel to front speaker  (Read 5645 times)

free

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Feature Request: Mixing Sub-channel to front speaker
« on: January 17, 2016, 07:57:11 am »

As I do not use a subwoofer it would be perfect if it would be possible to mix the sub-channel signal to the front speaker signal in the bass management / room correction.
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blgentry

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #1 on: January 17, 2016, 09:18:11 am »

By default, MC's DSP "output format" is turned on.  In Output Format, you set the number of channels you have.  If you set channels to 2, and mixing to JRSS, then all of this is automatic.  5.1 will get mixed to 2.0 including the sub channel.

Brian.
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glynor

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #2 on: January 17, 2016, 09:41:39 am »

If one of the preset mixes doesn't accomplish what you'd like, then you can do custom routing using the Parametric EQ DSP.
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free

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #3 on: January 21, 2016, 01:03:50 pm »

Thanks for the answers.

As there is no 5.0 channel output mode, I think for me the solution by using the parametric EQ is the best.

I would like to add the subwoofer channel to left+right front channels. I can add two rules, one for the right and one for the left channel. Am I right that when adding the subwoofer signal to both channels I need to adjust the gain to something minus....?
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mattkhan

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #4 on: January 21, 2016, 02:04:44 pm »

Thanks for the answers.

As there is no 5.0 channel output mode, I think for me the solution by using the parametric EQ is the best.

I would like to add the subwoofer channel to left+right front channels. I can add two rules, one for the right and one for the left channel. Am I right that when adding the subwoofer signal to both channels I need to adjust the gain to something minus....?
so you just want to send the LFE channel to each full range main speaker? bear in mind this is asking quite a lot of your mains given that the LFE channel peaks at 10dB higher than the mains.

I would think the correct amount to attenuate depends on your setup, summing 2 coherent signals will yield an increase in output of 6dB so that would suggest reducing the LFE by -6dB and then adding it to the L and R. However you will actually be acoustically summing these at the listening position so that may or may not end up at 6dB, in particular the resulting output level may be different across multiple listening positions. Measuring would be the best option but otherwise I'd go with -6 and tweak by ear.
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mwillems

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #5 on: January 21, 2016, 02:30:50 pm »

so you just want to send the LFE channel to each full range main speaker? bear in mind this is asking quite a lot of your mains given that the LFE channel peaks at 10dB higher than the mains.

I would think the correct amount to attenuate depends on your setup, summing 2 coherent signals will yield an increase in output of 6dB so that would suggest reducing the LFE by -6dB and then adding it to the L and R. However you will actually be acoustically summing these at the listening position so that may or may not end up at 6dB, in particular the resulting output level may be different across multiple listening positions. Measuring would be the best option but otherwise I'd go with -6 and tweak by ear.

He would need to reduce the L and R channels by 10 dB first to account for the volume differential as the differential is not baked in (both the LFE and the main channels both peak at 0dBFS).  It's assumed that the amplifier settings downstream will handle the 10dB volume differential, so if you're mixing it in yourself you need to create the differential, which is what JRiver does internally when using JRSS downmixing.  So he actually needs to reduce the L and R channels by 10 dB and then add the LFE to them with some additional volume reduction on the LFE to deal with both the duplication of a single channel, and (potentially) to avoid clipping.  So he needs the 6dB reduction for duplicating the signal, and potentially another minor increment (1dB or 2dB) to avoid clipping, so about -7dB or -8dB to be perfectly safe.  

In practice, he could potentially get away with less; I'd probably recommend using -6dB and counting on clip protection to save the day for a perfect storm, but the mains definitely need the -10dB attenuation first.
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mojave

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #6 on: January 21, 2016, 03:19:54 pm »

First you need some more digital headroom since you are mixing signals in the digital realm. You also need to have the subwoofer channel 10dB louder than the rest. However, when it is mixed to both speakers it only needs to be 4 dB higher per speaker. Acoustically the signals won't be exactly coherent so adding .5 dB extra helps. This will take care of both:
- Adjust the Volume -10 dB for all channels except the Subwoofer
- Adjust the Volume -5.5 for the Subwoofer

Next you should protect your main speakers by setting a high-pass filter
- Remove Low Frequencies (High-Pass Filter) on Subwoofer at frequency where your main speakers start to rolloff

Finally add the Subwoofer to the left and right channels
- Mix Channels - Add Subwoofer to Left
- Mix Channels - Add Subwoofer to Right

To test you go to Tools > Advanced Tools > Audio Calibration > Pink Noise at -20 dB > Play.
Add these two Mute items at the beginning of the Parametric Equalizer DSP.
- Mute (R, C, SUB, SL, SR) - This will only play pink noise in the Left speakers
- Mute (L, R, C, SL, SR) - This will play pink noise in both speakers, but it is the rerouted LFE channel

Both Mute options should playback at the same volume. I would leave the high-pass filter off for the testing so the signals are the same.

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mattkhan

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #7 on: January 21, 2016, 03:24:20 pm »

He would need to reduce the L and R channels by 10 dB first to account for the volume differential as the differential is not baked in (both the LFE and the main channels both peak at 0dBFS).  It's assumed that the amplifier settings downstream will handle the 10dB volume differential, so if you're mixing it in yourself you need to create the differential, which is what JRiver does internally when using JRSS downmixing.  So he actually needs to reduce the L and R channels by 10 dB and then add the LFE to them with some additional volume reduction on the LFE to deal with both the duplication of a single channel, and (potentially) to avoid clipping.  So he needs the 6dB reduction for duplicating the signal, and potentially another minor increment (1dB or 2dB) to avoid clipping, so about -7dB or -8dB to be perfectly safe.  

In practice, he could potentially get away with less; I'd probably recommend using -6dB and counting on clip protection to save the day for a perfect storm, but the mains definitely need the -10dB attenuation first.
fair point. I was, possibly incorrectly, assuming jriver would be handling this. i.e. if you have output format set to 5.1 then the output channels are all at the correct relative levels already. The user can then just manually attenuate channel 4, copy it to L and R and then mute it (or just leave it with no physical connection).

or perhaps this (10dB adjustment for LFE) is only applied if you turn on the room correction block?
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mojave

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #8 on: January 21, 2016, 03:38:28 pm »

or perhaps this (10dB adjustment for LFE) is only applied if you turn on the room correction block?
No, all channels are always at 0 dBFS. Room Correction does properly turn down other channels when entering in the dB levels measured for each channel, but doesn't automatically do a digital 10dB adjustment. This is because there are such a variety of subwoofers, efficiencies, amps, etc, that the user can often preserve headroom by increasing the subwoofer level externally.
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mattkhan

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Re: Feature Request: Mixing Sub-channel to front speaker
« Reply #9 on: January 21, 2016, 04:05:53 pm »

No, all channels are always at 0 dBFS. Room Correction does properly turn down other channels when entering in the dB levels measured for each channel, but doesn't automatically do a digital 10dB adjustment. This is because there are such a variety of subwoofers, efficiencies, amps, etc, that the user can often preserve headroom by increasing the subwoofer level externally.
One could interpret this as meaning that jriver does not correctly account for the difference between the LFE channel and the main channels. This must be a misinterpretation surely?

edit: I reckon https://wiki.jriver.com/index.php/Volume and/or https://wiki.jriver.com/index.php/Mixing could probably do with an update to make this clearer
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