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[mattkhan]

I have read a few threads on this subject and I'm still confused as to how it should be implemented.

I am using acourate to do bass mgmt & time alignment & correction. It has no explicit LFE channel support/awareness so does this mean I should simply apply a +10dB gain to the relevant filter or is there some other recommended approach that people use?

Thanks
Matt

[Hendrik]

The recommended/simplest way is to use the Room Correction DSP to apply per-channel volume gains if needed, that's what I use anyway.

To check all your efforts, you can use the volume calibration mode under Tools -> Advanced Tools -> Audio Calibration, the LFE signal generated there has the usual -10dB gain, so that real-world tests can be performed.

[mwillems]

It depends on how you're doing the mixing on the front end.  If you're using JRiver to downmix the LFE channel into the other channels, JRiver will "bake in" the 10 dB differential.  So if you were, for example, tri-amping using 2 channels in a 5.1 channel container, the LFE information would be commingled with the other bass info, but it would be 10dB louder.  So you'd just want to set your woofers normally.

http://yabb.jriver.com/interact/index.php?topic=79282.0

If your mixing target includes a dedicated LFE channel (i.e. 2.1, 5.1 or 7.1), and you're just applying convolution filters to the sub channel, you'll need to ensure the sub is calibrated 10dB louder than the other channels somewhere in the chain.  The best way to do that is to just set the sub amp higher.  If that won't work, you can (instead) add +10 dB of boost in convolution or PEQ (if you use internal volume and know you'll never get close to -10dBFS), or you can "play it safe" by using room correction or attenuating the other channels in JRiver by 10 dB, etc.  

One potential pitfall in the .1 scenario relates to re-routed bass from the other speakers (as distinct from true LFE information).  My understanding is that JRiver's room correction module preserves the volume differential between re-routed bass and LFE information, but if you're manually routing bass to the subwoofer channel in PEQ or convolution, you might need to do the necessary attenuation manually to make sure your re-routed bass isn't coming out at +10dB.  Not sure if that's an issue in your setup.

[Hendrik beat me to it   ]

[mattkhan]

My filters will deal with bass management so that suggests I will need to scale the .1 channel vs the mains accordingly. This seems to mean either by raising the .1 or by attenuating the low pass of each 5 and raising the sub amp gain.

[mojave]

Before Audiolense implemented the ability to handle the LFE track with +10 dB of gain, the best way to handle it was as suggested by Hendrik.

Activate Room Correction and put it before Convolution in the DSP. Add 10 dB to the subwoofer. This will actually lower all other channels by 10 dB to prevent clipping.

If you try to change the amp gain or filter levels it gets more difficult to match levels and have the LFE the correct proportion compared to rerouted bass.

[mattkhan]

Before Audiolense implemented the ability to handle the LFE track with +10 dB of gain, the best way to handle it was as suggested by Hendrik.

Activate Room Correction and put it before Convolution in the DSP. Add 10 dB to the subwoofer. This will actually lower all other channels by 10 dB to prevent clipping.

If you try to change the amp gain or filter levels it gets more difficult to match levels and have the LFE the correct proportion compared to rerouted bass.

Is there a description somewhere of how audiolense handles this? Or how jriver itself deals with it?

[mojave]

Audiolense has a check box that lets you increase the LFE channel by 10 dB. It essentially lowers the other channels by 10 dB prior to mixing just like JRiver does when using Room Correction or when downmixing to stereo.

It isn't any more complicated than that so I'm not sure what else you are asking. Acourate expects the LFE channel to already be +10dB before it goes through its filters. Just do that in Room Correction and it will work fine after you have created the filters in Acourate.

Here is a thread discussing it a couple of years ago:
LFE Level and Bass Management With DSP Convolution Filters

[mattkhan]

It isn't any more complicated than that so I'm not sure what else you are asking.

OK thanks. I am now conditioned to expect everything to be incredibly complicated for apparently obscure reasons which is why I was asking  

Does that mean that's all av processors do? i.e. just cut everything else by -10dB

Finally, just to double check, this means doing nothing (no delays, no XO, no nothing) in Room Correction except adding 10dB to the sub channel which at this point in time is the LFE track only because bass mgmt is happening in the subsequent filter.

[mojave]

Does that mean that's all av processors do? i.e. just cut everything else by -10dB

I believe a receiver will adjust all channels by -10dB, perform bass management, and then raise all channels again by 10 dB. The subwoofer output then has an extra opamp in the signal path that increases the subwoofer level by 10 dB.

When you are using Room Correction to do bass management, JRiver essentially does this and expects you to use your sub's amp to increase its level by 10dB to to manually do it in JRiver. The external increase in the sub's amp increases signal levels for other channels. You could probably do something similar in JRiver by using Room Correction before Convolution and then Parametric Equalizer after Convolution

Room Correction - +10 dB to LFE by actually adjusting all other channels by -10dB
Convolution - mix LFE and rerouted bass
Parametric Equalizer - Add Adjust the Volume and increase all channels except subwoofer by 10 dB
Subwoofer - increase volume level

You can check that it is working properly using Tools > Advanced Tools > Audio Calibration > Mode:Volume Calibration

Finally, just to double check, this means doing nothing (no delays, no XO, no nothing) in Room Correction except adding 10dB to the sub channel which at this point in time is the LFE track only because bass mgmt is happening in the subsequent filter.

Yes, you don't need to do anything else in Room Correction other than activate it and add 10dB to the sub channel.