Forum Top Banner Ad

Collapse

Ebay Classic organs

Collapse

Announcement

Collapse
No announcement yet.

MDS Channel Mixing

Collapse
This topic is closed.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • MDS Channel Mixing

    The MDS Organ I play has four channels (GT/PD1, SW1, GT/PD2, SW2) that are mixed down to two. Those two (SW & GT/PD) are split to the 4 channel amp. The amp feeds 6 speakers. 2 Front Left (GT/PD), 2 Front Right (SW), and two in the rear (SW & GT/PD). You can then turn on or off the MAIN (4 front) or ANTIPHONAL (2 rear) speakers from the stop tabs.

    Anyway, I'm wanting to split the channels back to 4 outputs because acoustic mixing is better than electronic mixing. I'm planning on adding a Stick-On mixer from RDL and another amp to power the rear antiphonal speakers mixed down to two channels (like it is now).

    1. The signal from the Allen ADC mixer is line level (1 volt) right?
    2. Should I mix the antiphonal speakers as two channels (SW & GT/PD) or all the way down to one?
    3. Is there a different way to mix the signals for the Antiphonal speakers other than another mixer - does the speaker relays have the ability to mix signals?
    4. How many speaker signals can I run through one speaker relay - obviously 2 because that's what it is doing now, but will it take 4?

  • #2
    Unless someone has altered the original channeling, an MDS organ would not be mixed down in that manner. A two-channel organ would still have some Gt/Pd stops in the left and others in the right, likewise with the swell stops. For example, the swell salicional and the voix celeste would never be in the same channel because their frequencies should only "mix" in the air, not in the electronics, which would produce an ugly phasing sound.

    You need to consult the documentation for the model you have and try to discover if it has been messed with and why. The antiphonal relays only serve to switch speaker-level signals and do not mix channels in any way. Normally an antiphonal is simply a duplication of the upfront speaker system, so it's odd that you have four channels up front and only two in the rear.

    What MDS model is it? I might be able to send you a factory audio chart that might help you sort it out.
    John
    ----------
    *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

    https://www.facebook.com/pages/Birds...97551893588434

    Comment


    • #3
      It's an MDS-25.
      Last edited by tschnuckel; 09-21-2013, 07:48 PM.

      Comment


      • #4
        The MDS-25 is a W4 based organ with the W4 cage having a total of 6 audio outputs on RCA plugs. Two carry combined great/pedal stops (not separated in any way, just some great and some pedal in each channel). Two others carry swell stops, with the usual type of Allen cascading of the stops -- 8' and 4' members of a chorus are in opposite channels, the string and string celeste are in opposite channels to they won't do any electronic out-phasing in the audio system. The remaining two outputs are for the two Alterable Voices -- the Card Reader stops, which are of the same type as in MADC-3 organs of the previous era.

        The audio mixer board combines these 6 channels down to two. Each of the two output channels carries one great/pedal channel plus one swell channel plus one Alterable channel. So you can see that there is not a "swell" audio channel or "great" channel in the output. That is why I'm puzzled by your description of the channel arrangements. Also there are not normally four discrete channels coming out of the mixer, so if your present setup has four up-front audio channels, either they are simply the two standard channels duplicated, or else there has been some tinkering with the audio configuration.

        That is in fact quite easy to do, if a dealer or tech were so inclined. Knowing as we all do that the more discrete channels the better as far as realism, it would be an easy step for a dealer or tech to make simple changes that would give an output of four audio channels -- two of them carrying only the left and right great/pedal mixes and the other two carrying the left and right swell mixes. This would be a nice way to set up an MDS-25 if it were done properly. (This would in fact change your MDS-25 into an "almost" MDS-35, a virtually identical model with audio mixed down to four channels instead of two, but also has drawknobs instead of tabs.)

        Now, if an organ were to be modified in this way, you could no longer have an antiphonal with only two channels in it because once these channels are separated out and sent through separate amplifiers, you can't re-combine them without some fairly elaborate electronic stuff. OR you could have an antiphonal that carries only the swell or only the great/pedal, but not both.

        It's pretty rare for a dealer to have the desire or knowledge to do something this elaborate, and Allen always encouraged dealers to "sell it like it is" and specifically to avoid re-configuring the audio in any way that required non-standard Allen equipment in the console.

        So I'm curious to know what exactly might be coming out of each of the various channels in your setup. That might shed some light on what, if anything, has been modified. I'm inclined to think that all you have is just a doubled-up set of main speakers up front and a single pair in the antiphonal, and that great, swell, and pedal stops come out of all of these, though the left/right separation of each division is maintained.

        Please let me know what you find out.

        - - - Updated - - -

        Wow, that was a long-winded treatise. I probably got way off topic and failed to answer your questions, but I guess I explained it pretty well!

        No, the Allen antiphonal relays can only switch two channels each because that is all the contact points there are in the relays. One two-channel amplifier output can be directed into either or both pairs of speakers. That is the only function of the relay unit.

        Here is a scan of the audio configuration as it would have been at the factory. You can probably see that it is easy to "unmix" certain channels and wind up with four discrete outputs (or even six if you wanted to do that --two of them being the Alterable Voices).

        - - - Updated - - -

        And here is the way to change your MDS-25 into a four-channel organ:
        Attached Files
        John
        ----------
        *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

        https://www.facebook.com/pages/Birds...97551893588434

        Comment


        • #5
          It wasn't too much info. I followed you.

          I crawled to the antiphonal speakers and there are indeed four speakers there as well.

          It is configured just like the diagram for and MDS-25 mixed down to two. Then these two CH are split to a 4CH amp to handle 8 speakers. Each channel appears in the left and the right side and twice in the rear.

          If we split the channels out to four in the front, would we put the SW channels on one side and GT/PD on the other? OR put one SW on the right and the other SW on the left and do the same with the GT/PD?
          The antiphonal are all in the rear center does it matter which speaker is which channel?

          Also will there be a significant drop in volume by splitting to four. There is some input gain left on the amps. I think they are at 6 right now.

          THANKS!
          Tyler
          Attached Files

          Comment


          • #6
            Tyler,

            There would be no downside, AFAIK, to re-configuring it like the MDS-35, thus having two G/P channels and two swell channels. However, I am puzzled as to why the dealer installed it with (evidently) doubled amps but did not make the split. If the dealer had a good reason for leaving it that way, such as inability to get a proper divisional balance or the need for that much audio power, you ought to carefully consider the consequences. Of course, if the results are not good you can very easily put it back the way it was.

            Unless the church is large, the pedal should still be adequate (16' pedal stops may presently be benefitting from getting two amp channels). The increase in separation and clarity should be worth doing, and you can regulate the pedal with a little voicing. Input gain by itself is not a problem, but you will need to carefully work with the bass balance after making the separation.

            Unless there is a huge spread between the two chambers, you could have the swell on one side and the G/P on the other. This will work best if the chambers are quite elevated so that the sound gets distributed all over the church. Otherwise, you might have places in the church where listeners would hear only one division of the organ clearly, and even under the best circumstances you take a chance on creating a little imbalance between the swell and great. It is probably OK as long as the organist can hear both divisions adequately at the console.

            And it doesn't make any difference how the speakers are arranged in the antiphonal if they are all sitting side by side.
            John
            ----------
            *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

            https://www.facebook.com/pages/Birds...97551893588434

            Comment


            • #7
              John,

              The church seating area is about 35'x50'. The sanctuary area is about another 15' deep. Not a large church. Ceiling and walls are wood. Carpet only in aisles and sanctuary. Pews are wood. It seems like 8 speakers is PLENTY of audio for this space.

              The cable that feeds the antiphonal speakers may be the reason for dual channels. It isn't normal speaker wire. It is a cable about the size of your thumb with 28 single wires. It looks like a telephone cable. It must have been from an older organ. Anyway, they took 7 strands and crimped them together to make a larger wire. It's weird, and the cable runs along the peak of the ceiling. It is concealed behind a board. I would consider using it to pull new cables, but don't know if it has been stapled at any point. So I might be looking for another place to run cables, or getting a lift.

              The run is about 85'. My training in sound systems tells me I should use 12ga wire, but it seems I've only seen Allen use 14ga for everything. 14ga still ok since there are less transients in organ than PA?

              I'm assuming I will have to do a little tweaking to the voicing when it goes to 4 channels. I do have the cage chart (it was in the console :->) Is there a method to voicing, like should I reference certain stops, play certain pitches? What about voicing the alterable voices?

              Tyler
              Last edited by tschnuckel; 09-24-2013, 11:05 AM.

              Comment


              • #8
                Perhaps there was an old Saville or other analog with a bunch of channels, thus the big bundle of wire. Allen would not approve the use of such a thing, but if it works, if there isn't more than an ohm of resistance from end to end, and no leakage at all from one to the others, go with it. Obviously you are limited to putting two channels into the antiphonal, but you could have just a swell antiphonal by connecting the great/pedal speakers up front directly to the amps (without going through the relays) and using only one relay to switch the two swell channels.

                Since you have the voice chart, if you re-configure the audio just leave all the controls as they are and check the balances. It may be fine. The usual routine is to center the bass, treble, and level controls (turn the "W" controls off so the wind noise won't influence the balancing). Set the amplifier knobs at "8" (no hard and fast rule on that, that was considered "normal" by the factory back in the day). Then use the chart to first establish the volume of the great principal 8 (a comfortable level, not too loud, similar to what a single pipe would sound like at middle C), then the great octave 4, which should be almost as loud on tenor C as the principal's middle C, though some people prefer to set it a hair softer than the principal. Fiddle with the bass and treble to obtain a natural sound for all the stops in these two groups, paying special attention to the mixture and to the 16' pedal stops.

                Once you are satisfied with the sound of the great/pedal division, set the 4' principal in the swell equal in volume to the octave 4 in the great. The fourth channel can then be set by comparing whatever stop in it corresponds to a great stop. Another method is to make the viola and viola celeste equal in volume, since they will come from opposite swell channels. Again, tinker with bass and treble to get a natural sound from all the stops in each channel group.

                Set the "W" controls in each channel while listening for chiff and air sound on whatever stop is "winded" in that channel, as indicated in the voice chart. Most people don't want this effect overdone, though I once set up an organ in a church where they wanted it to sound like a leaky, wheezing old pipe organ, so I set the W controls over half-way to max!

                This procedure will get you a rough balance, and you may have to tweak it when you listen to someone else play the organ. Balances may be different out in the church than at the console.
                John
                ----------
                *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

                https://www.facebook.com/pages/Birds...97551893588434

                Comment


                • #9
                  I did a little more digging at the "main" (front) speakers. One front side has a pair of HC13 U and the other side has a pair of HC11-2 FV. The rear are HC15 U. I seem to remember reading that an HC11 is the same as an HC13? I'm puzzled that the crossover on the HC11 doesn't have a wire connected to the Neg terminal. Maybe it comes from the back of the card since it's on the front of the speaker. There is one soldered on the Pos. The speaker works, so it must be connected somehow.

                  How do the HC15 and HC11/13 compare, besides 15" and 12" woofers? Do they have the same sensitivity (SPL) & power rating?

                  Anyway, I'm thinking of setting the "main" organ as the rear HC15 speakers and the "antiphonal" as the front HC13/11 speakers. That's the reverse of what it is now. This way the resistors on the relay boards can keep the front speakers, which are lower & closer to people than the rear speakers, from blowing people's hair off. Right now when the congregation sings out, the organ is a little weak, but I don't dare turn up the volume because the front speakers would blow the priest away.
                  Last edited by tschnuckel; 09-28-2013, 08:54 PM.

                  Comment


                  • #10
                    That might work. Can't hurt to try.

                    As I recall, HC-11 and HC-13 are basically identical except for the moving of the crossover assembly to the back of the box on the -13. As to the missing wire, it may well be connected on the back side where you can't see it.

                    The sensitivity of HC-11/13 cabinets should be about the same as HC-15 since the crossover is the same, as are the mid and tweeter drivers. The 12" woofer in place of a 15" surely rolls off the bass response a bit, but in most of the audible range they should sound the same.
                    John
                    ----------
                    *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

                    https://www.facebook.com/pages/Birds...97551893588434

                    Comment


                    • #11
                      Well it's been over a year, but I've finally have the MDS-25 audio split into 4 discrete audio channels.

                      Ended up having to pull 4 new cables for the rear speakers. Connect the right ground wires to the relay board and change the jumpers for the antiphonal to NC since both speaker tabs say OFF. Also had to readjust the cage.

                      The biggest difference I notice, although subtle, is the sound is a bit more "random" sounding. In a pipe organ, the sound comes from a slightly different location because no two pipes are in the same spot. The sound appears to shifts around a bit. With the MDS-25 in 4 channels, it too has a bit more of this locational fluctuation. I also think the sound is less confined or manufactured sounding.

                      Again these are all pretty subtle, but give the organ a more realistic performance.

                      I wasn't sure how the splitting the SW and Gt/Ped would fair at the front. I put an even and odd channel on each side, but after listening, have decided to make it a true Sw Gt/Ped division up front. This too makes the organ seem more organic and less manufactured.

                      Comment


                      • #12
                        Sounds good to me. Glad you finally got it done. Organ work (volunteer especially) goes very slowly in churches, and my own church is no exception. The MDS-45 has been installed for well over a year, and I still haven't gone much beyond the basic speaker setup I started with. (I've bought bass crossovers and additional amps and speakers, but I'm still waiting for a good long holiday to do the work!)

                        I think you'll like having a true split with Gt/Pd on one side and Swell on the other. With our MDS-45, the channeling is in fact identical, with two channels Gt/Pd and two channels Swell. My church is small too, and the chambers are not built as I would like, but they are what they are -- I have openings about 3' wide and 6' high about 8' off the chancel floor, with one opening at each side facing inward only (toward the choir seating), so nothing faces directly out to the nave. The organ console is in the choir area, so I hear the speakers in both chambers quite well. The only complaint I have is that the organ is somewhat louder to us on the chancel than to the folks in the nave, but then I suppose some of them would rather not hear as much organ as I want to hear!

                        At first, I installed ours as you did, with one of each division on each side. But when I changed it to the true divisional split I found I enjoyed being able to hear the separate divisions coming from different chambers. I don't play much fancy organ music, but even just doing a simple improvisation for communion, I enjoy switching back and forth between swell and great for variety, and it's nice to hear the sound field shift from side to side, or to hear a solo stop coming from one chamber while the accomp comes from the other.

                        Keep up the good work and keep posting about your experiences. It's just great to know that there are people out there having this much fun with these great instruments!
                        John
                        ----------
                        *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

                        https://www.facebook.com/pages/Birds...97551893588434

                        Comment

                        Working...
                        X