LRM vs LRMsum vs LCR

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This topic contains 6 replies, has 2 voices, and was last updated by Profile photo of Tofke78 Tofke78 4 years, 8 months ago.

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  • #57862
    Profile photo of Tofke78
    Tofke78
    Participant

    Hi

    I would like to connect my subs separate from the LR. Which setting is perfect and what are the differences: LRM, LRMsum or LCR? I can’t find much information on this for the GLD.

    Last weekend I used the LRM but occasionally I saw a peak on the level meter even when the fader was on low volume. Probably it’s because it’s a sum of the LR but it is not possible to set a different mix in LR and M with the GLD…? Is it therefore more wisely to use an Aux in stead of LRM to feed the subs?

    I think it would be nice to that the M-fader could follow the LR-fader.

    What are your suggestions for this issue?

    Thanks everybody!

    #57863
    Profile photo of cornelius78
    cornelius78
    Participant

    LR+M is what you want. Separate mixes for LR and M. LR for tops, M for subs. LRMsum simply sums L+R to a single bus for a mono output. LCR changes the panning to pan between left, centre and right, based on your channel assignments, if you’ve got that type of setup. If you’re just wanting to do aux fed subs, use LR+M. Channels can be assigned/unassigned from the M bus using the Mix buttons. By default everything is assigned (and the sends from channels are post-fader fixed at unity, essentially a subgroup,) which is probably why you thought it was just a copy of LR. Unassign the channels you don’t want in it, just leaving channels like kick, bass, keys, playback etc assigned. As for control, just assign LR and M to the same DCA. Have the “mains” DCA fader on the surface, you can bury the original LRM faders (or remove them from the surface completely) if you’re happy with their relative levels and assignments. You can put their Sel buttons on the softkeys if you need.

    Edit: As for the peaking, the peak meters are multi-point sensing, ie they illuminate if the console senses a peak anywhere in the channel\bus’s signal chain, not necessarily just post-fader. The channel\bus the fader could be down at -inf, but if the preamp\input signal is peaking, or the gain on the eq, or the make-up gain on the compressor is peaking, the peak light will still illuminate.

    #57864
    Profile photo of Tofke78
    Tofke78
    Participant

    Cornelius78, thanks for your explanation.

    I agree, but you can’t make another mix (fader volume settings) than as it is in the LR-mix? So is it therefore not more interesting to use an LR setup and feed the subs with an Aux in stead of M in the LRM setup?

    To the LR I assigned everything (keyboards, guitar, vocal mics, effects). To the M I assigned only the keyboards.

    The peak was only on the grand level meter M on the surface and not on the grand level meters L and R on the surface. Therefore I did get the feeling that it was because of the sum of the Left and Right channels to the M output.

    I like the idea of putting the LRM on a DCA 🙂 Thanks

    #57866
    Profile photo of cornelius78
    cornelius78
    Participant

    You could use an aux instead of the M bus, and it would give you more flexibility in terms of sending more of one channel to the subs (send level not fixed at unity.) Personally I don’t like that method, as it messes up the balance of the instrument when it’s routed to both subs and tops: to my mind a fixed send at unity makes more sense. To each his own. If you do decide to use LR+Aux, you can still tie LR+aux masters together on a DCA.

    If L and R were the same signal (you were essentially running dual-mono) and you summed them to mono you’d get +6dB at the mono bus input. Depending on how close you were to 0dBFS, that would have caused the clip light to illuminate, even if the M bus fader was down.

    #57871
    Profile photo of Tofke78
    Tofke78
    Participant

    Thanks again for your reaction

    The reason why I would use an Aux instead of the M-bus is to drop the leven of the inputs a bit so the M-bus would not peak that fast. I don’t think that would not mess up the balance of the instrument. The intruments we use are:

    2 vocal mics: routed only to L and R
    1 mic for the guitar amp: routed only to L and R
    2 stereo keyboards (providing drum, bass, piano…) each one connected L to an mono input (panned fully L) and R to a mono input (panned fully R): routed to L and R and M

    The input signal of each mono channel L and R of the keyboards is around 0dB. So you say this becomes + 6dB at the M-bus?

    So when I use an Aux to feed the subs and rout the keyboards to LR and Aux with the level to the Aux a bit lower than as to the LR, the problem of the peak would be resolved I think. And this without messing up the balance. No?

    The idea of the DCA to control LR and Aux still remains great 🙂

    #57873
    Profile photo of cornelius78
    cornelius78
    Participant

    If the signals were identical then yes, when summed you get approx +6dB (IIRC due to logs the number is actually +5.94db with a lot of decimal places.)

    The more different the signals are from the L and R outputs of the keyboard the less coherently they’ll sum, resulting in less of a boost at the input of the M bus. In fact if they’re out of phase with each other you’ll notice a decrease in level when they’re summed. If they were so different that they were 180degress out of phase with each other they’d sum to nothing.

    You might have to dig around a bit to find the exact numbers for the GLD, but often peak lights on consoles are configured to illuminate a couple of dB before anything clips (eg on an analogue console who’s outputs could do +26dBu before distorting, the peak light might come on at +22dBu, so despite the peak light, you weren’t actually clipping. Some digital mixers will show a clip light at -6dBFs, even though technically the user still has 6dB (1-bit) of headroom before actually clipping.

    With only 2x vox and 1x gtr amp, no acoustic kit and no bass stack, are you sure you actually need to be running aux-fed subs? Sure if you had an acoustic kit a bass stack and you had LF from stage bleeding into all the 6x vocal mics and other drum mics it would make sense, or if your vocalists were wandering around in front of the subs it would make sense, but do you really need it for your setup?

    #57881
    Profile photo of Tofke78
    Tofke78
    Participant

    It’s pretty technical for me, but thanks for your expertise 🙂

    I think I read somewhere that on the GLD the peak lights up about 6db before actual clipping, but I’m not sure. Anyway during the show I could not hear any distortion but I prefer not seeing any red lights 😉

    Why do I prefer running the subs apart from the LR? Simple, you’ll become a much more relax global mix. For us especially on the vocals. Before I set up some high pass filters on the vocals but many times it’s not just that… And yes many times the FOH is so close near the vocals (because of a lack of space) that on higher volumes the difference with subs fed apart is huge.

    I think I’m gonna try it out this weekend with an Aux in stead of the M-bus. I’ll let you know the result

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