Adc 7000

[IndianaBill]

Greetings!

I bought an ADC 7000 last year, and, after an extensive remodeling, I am finally about to complete the permanent (hopefully final) installation. The church I bought it from had bypassed the ADAC units, and to be sure, their sanctuary was lively enough they didn't need the ADACs.

This is what I don't understand: this is a nine channel instrument. If I understand the ADACs correctly, everything is mixed down to two channels and then passed through the ADACs. Doesn't that defeat the purpose of having nine channels? And if I were going to mix down to two channels, would I not now only need two amplifiers and speakers? I understand the issues with canceling harmonics and the like, but in a typical home application, would that be that noticeable?

As always, input from Forum members is most appreciated.

[jbird604]

While the signal is indeed mixed down for inputting to the reverb, this mixing does not affect the audio path itself. The outputs from the nine cage outputs go straight through the reverb mixer (USRM) and come out unchanged, going on to the amps and speakers as nine discrete channels.

The "wet" portion of the signal (the output of the reverb system) gets blended into the nine audio streams in a planned manner when it returns to the USRM board, with some channels getting the Left reverb and some getting the Right reverb, preserving the "stereo image" created by the reverb processor. But this reduction to stereo does not affect the main tones at all. They remain fully discrete, and each speaker delivers only the sounds of the channel to which it belongs....

BUT, when reverb is on, you will obviously hear SOME bleed from other channels in each speaker. This is intentional and in fact desirable, as it is part of the "ambiance" generated by the reverb system. This doesn't mean that you will now hear the entire swell division coming out the great speakers, for example, but you will hear "traces" of it, just as in a true lively church situation the sound becomes quite non-locatable by the ear once it leaves the pipe chamber and begins to swirl and bounce around the room.

So you still need all the audio channels in order to play the organ with reverb. Just be assured that the reverb effect will be properly distributed among all the speakers and will slightly obscure the distinction among the channels, though it will still be obvious that the organ divisions are split up by channels.

[JohnBoyDeere]

Post some pictures if you can:)

[jbird604]

As to the general question of mixing the nine channels down to two for a home setup... I used to be a proponent of that, but have changed my mind somewhat. With old single-computer MOS-1 Allens, with no frequency separation, I have found it not too detrimental to mix the main and flute outputs of a DAC board together and use a single amp and speaker in a limited space situation. Obviously that's already a barebones organ, and mixing the two outputs is not that big a step from the existing total mixdown of all the stops in each channel to a single output. And the stops all remain locked in tuning and phase, so there isn't any outphasing weirdness going on.

But once you get beyond these simple old organs, all newer ones have multiple tuning references. Allen's ADC models are designed so that the stops that share an audio channel also share the same frequency generator table, therefore they are all tuned to the same reference pitch, and do not outphase with one another. It is the interaction IN THE AIR among the various separate audio channels that produces the interesting undulations and chorusing and so on. If you take note, you'll see that opposite members of a celeste pair are always in different audio channels, so the "celesting" takes place in AIR and not inside the amplifier. This makes the sound far more pleasant, not to mention more like what happens with real pipes.

Because of this, nearly every Allen ADC model is designed with the optimum number of audio outputs. All the phase-locked stops from a given frequency table are mixed, thus taking best advantage of each audio channel. Mixing them down differently is going to involve some degradation of the sound. In some cases, this may be acceptable, and in others it may be quite wretched. And it depends on how sensitive you are to this sort of thing as well.

As I said, I was once a proponent of mixing. Twenty years ago I installed a big old Baldwin at the church where I played, and I literally mixed all the outputs, of which there were nine, as I recall, down to mono. I ran the mixed signal through an Alesis MIDIVerb4 processor to give it some artificial "space" and movement, and I thought it was grand. I eventually replaced that old organ with a newer but still ancient Rodgers analog, and mixed the six outputs of that one to mono as well. The primary need for the organ in that church was for it to be quite loud, and I had a massive two-channel audio system to play it through, so it sounded good to me, at the time anyway.

Once I started having a good organ at home -- I've had, over the years, among others, two ADC Allens, and now an Allen Renaissance -- now I can clearly hear the wretched outphasing beats and unpleasant "grinding" of repetitive chorusing when channels are mixed. So I have been going the other direction, ADDING discrete audio channels whenever the design allows it. So I modified the two-channel ADC I used to have into four channels by un-mixing channels. Same with the last Rodgers digital I had at home. I did the same with my current Renaissance organ, though it requires some hardware changes as well as DOVE software to do it. And I find these organs far more enjoyable than they were with the channels mixed.

My advice on the 7000 is to use all the channels, but use some small speakers for the non-pedal channels. Allen's HC-13 cabinets are much smaller than the standard HC-15. Other good quality pro-quality small speakers can be used, but don't go too small. It's still organ sound you want, and organ sound is somewhat demanding of the speakers. Miniature hi-fi speakers, even "audiophile quality," are not always suited for organ tone projection, though I've heard, for example, higher-end Advent audiophile speakers used on an Allen with good results. Be sure to use HC-15 or HC-12 cabinets on the channels that carry pedal stops at 16' or 32' pitch.

[myorgan]

Be sure to use HC-15 or HC-12 cabinets on the channels that carry pedal stops at 16' or 32' pitch.

If you do not have sub-woofer speakers, I highly recommend the HC-12 over the HC-15 speakers for the 32' pitches. If you really want to know why, there are several threads where the reasons have been extensively discussed. Let me know if you need me to look them up.

Michael

[organman95]

The ADC 5000 one of the church buildings here has (if you recall, I have a cluster of three buildings) has five HC-14 and one HC-12, specifically for the lowest notes of the 32' stops.

[don60]

One of the nine channels in a standard ADC 7000 is devoted exclusively to the Contra Bombarde 32'. This channel could be mixed into one of the remaining pedal channels with no ill effect in a smaller installation.

John, the ADAC (Allen Digital Ambiance Computer) is a mono unit and would not preserve any "stereo" imaging. Some installations of larger instruments used two ADAC units, but Allen did so because the first reverb mixer board and ADAC box were maxed out on channels and a second one was needed to pick up the remaining channels. At least that is what they did with my ADC-7000. I saw no indication that they were trying for some pseudo-stereo effect.

[IndianaBill]

Thanks everyone for your input. As always, the Forum is helpful because of people like you!