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Question on "theory" of multiple output channels

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  • Question on "theory" of multiple output channels

    On Rodgers organs(and I am sure others), there are multiple output channels. For instance on a 330 the output channels are:

    Swell Reeds and Celeste

    Swell Flute

    Swell Diapason

    Great and Choir Flute

    Great and Choir Diapason


    In the manual it gives several different options based on how many channels/speakers you are going to use.

    Coming from a pipe organ background, I am trying to figure this out based on my understanding of a pipe organ. In a pipe organ, each sound is being created by an individual pipe. AFTER it is created, it of course is mixed in the air with any/all of the other pipes that are being played at that time. The sound of the pipe is determined by it's construction, scale, voicing and wind pressure. To accomidate varying room sizes, you can also change the scale or voicing of each rank of pipes or the pressure of the wind supply or all of the above. (Very basic description).

    As for electronic organs, I have thought of 2 different possible theories for this, but I have no documentation to back up either one.

    1 - Put simply, the larger the space, the more channels/speakers you use.


    2 - Dividing the channels allows for more control of the individual sound that each channel is putting out. This would perhaps allow the speakers to put out more "pure" sounds of a given type i.e. reeds or flute without having other sounds "mixed" in and possibly altering the "integrity of the seperate sounds.

    So if you had a speaker that is only putting out the reed sounds you could choose a speaker that would be more suited for that purpose. The same for the flute or diapason. If this the case...and if so, does it actully work in practice?

    I would appreciate more clarification on this.

    Thank you,
    Steven C. Scott, Founder, CEO
    International Society for the Preservation of Historical Instruments
    2391 Porter Street
    Lebanon, Oregon 97355
    [email protected]

  • #2
    Re: Question on "theory" of multiple output channels

    I think it's your #2 guess.I saw it in the Conn 6xx schematics which had like 3 channels and even they started making leslie's with many channels for this reason.The 251 leslie is 2 channels' but there's other's that are 4 channels.


    • #3
      Re: Question on "theory" of multiple output channels

      I agree with Albaners. My 3-manual Wurlitzer/Viscount can accomodate from 2 up to 8 external channels, although there are just two internal channels within the console. The external-channel breakdown is one channel for each manual and pedal for the first four. If Iutilize the second four outputs, each one breaks off the "treble" voices from the first four channels, so there are effectively two channels for each manual and the pedal. I have experimented using 2, 3, 4, and 5 external channels, and with each added channel, the sound quality improves noticeably.


      Wurlitzer/Viscount C-380 3 manual with Conn pipes.


      • #4
        Re: Question on "theory" of multiple output channels

        None of the above.

        The main reason for multiple channels is to mix the various voices acoustically, in the air, rather than electrically in the amplifier.

        Electrical mixing is perfect causing harmonics to be cancelled out and destroying the the ensemble you'd get by routing the voices through separate channels.

        In electronic organs channels tend to be defined the way they are for economy and convenience. Given a four channel organ, for example, you'd get a much better ensemble by distributing the notes of a diapason stop over the four channels rather than routing them all through a single channel.


        • #5
          Re: Question on "theory" of multiple output channels

          What if one were to build an organ with a separate channel for each note on each rank? Then, taking it one step further, have a dedicated monitor for each 'pipe'. If each speaker was tuned for its adopted tone, then the result would be as good as a real pipe organ... Correct?
          Think of it like this:

          Pipes build on each other, one tone at a time. This would also.
          Pipes move the air, as do monitors
          Pipes are separate modules and speak in different location, as does this setup

          Theoretically, couldn't this be plausible? I mean, no doubt it would be extremely costly, and obscenely massive to build.... but just use your imaginations on what it would be like.

          (in case anyone thinks I'm throwing the thread off topic, I am merely "Questioning the 'theory' of multiple output channels", and not trying to hijack the thread) ;-)


          • #6
            Re: Question on "theory" of multiple output channels

            I wish all Happy New Year.

            Regarding multiple channel organs, this was done in the 60's with some of the large analog organs. They had individual oscillators, amps and speakers for each note. The advantages were far outweighed by the cost. I was considering such an organ but the cost was prohibitive.

            You can play back a good record or tape of an organ and it sounds good with only 2 channels so doesnt it make sense to apply this to organ design?

            A better and cost-effective solution is to dedicate channels based on the response requirements. That's what Allen and most others do.

            As personal experience has shown, if you want a true pipe sound you need pipe. The tuning errors, noise, trem response, and other factors all combine for the pipe sound.

            Electronic is very good and comes close but it aint pipe.

            (I'm not going off-topic, just explaining my point)


            • #7
              Re: Question on "theory" of multiple output channels

              I attended a concert in a resonant church using a new Allen 5 manual with 50 channels. The speakers were placed all over the front of tjhe church on the floor pointing in random directions. The sound combined in the air rather than electronically giving a much more pipe like sound. The build up of the ensemble was excellent. The resonant acoustics greatly helped the sound.

              I believe that the multiple channel theory that the sound mixes in air is correct. If the waveforms are mixed electronically, the amplitudes of the harmonics add and subtract do to the different phases of the waveforms. In the air, the resonances of the room change the phasing of the harmonics unpredictably (if a non-rectangular room) and thus the amplitudes will add and create a slight celeste effect making for a bigger sound.

              The Allen electronic was very good but but still am not ready to trade in my Wurlitzer pipe organ which has a nice big ensemble.


              • #8
                Re: Question on "theory" of multiple output channels

                >You can play back a good record or tape of an organ and it sounds good with only 2 channels so doesnt it make sense to apply this to organ design?

                >I believe that the multiple channel theory that the sound mixes in air is correct.

                I do, too. The difference in listening to a two-channel recording of a pipe organ, and an electronic organ through two channels is this:

                In a real pipe organ, all the cancellations due to phase differences in the different pipes, as well as room resonances and standing waves, all contribute to the final sound. Mixing electronically doesn't produce the same effect.