Adjusting reverb on an Allen ADR-4 Reverb unit in MDS-40S organ

[whayes]

My MDS-40-S has the ADR-4 reverb unit in it. It has not been adjusted at all since it came from the factory. I looked at the unit and saw several screw-type adjustments to tweak the sound (look similar to the voicing "pots" on the cages), but I have been hesitant to adjust any of them since I'm not that familiar with the mechanics of what everything controls.

When I play the organ with full principal chorus, mixtures, reeds, etc, the reverb is fantastic, and the sound lingers just as if I was in a large, acoustically live room. But the softer sounds don't seem to have enough reverb. When I play a quiet piece with strings or flute celeste accompaniment, with a Krummhorn, English Horn, or any quiet solo reed, the reverb dies too quickly and almost appears as if there's no reverb at all.

The sound also seems to die when I play individual stops, even relatively loud ones such as the 8' Great principal, and to some, although a lesser degree, even the 8' Festival Trumpet on the Choir. But when the full principal chorus is drawn, it isn't an issue. Maybe just the sheer combination of stops that create a full foundation ensemble make the reverb seem to last longer because of the volume of sound to begin with.

Just wondered, is there any way to adjust the unit so that the sound "lingers" longer even when playing the softest stops on the organ, without making it sound "fake" when full organ is played?

And can anyone tell me what all those adjustments on the ADR-6 really do? I am not at home right now and don't remember what all the adjustments on the unit were, but I remember one that was something like "bass boost" or something to do with bass. I wondered what in the heck bass boost had to do with reverb! I hate to start messing with it and throw the sound completely out of whack and never be able to get it back to where it is now!

[DellAnderson]

You are correct not to rush in and change things if you like how things are now. It is somewhat tricky to retrace your steps, especially since there are inexplicably what appear to be two adjustable potentiometers in series - the input and the output + the bass (which seems to be some kind of primitive tone control for the reverb). I played around with mine and finely got something tolerable (too much is bad!!) but I'll be very interested to hear how these work. I have a lowly ADR-4 and it has the following adjustables:

Input Gain
Output 1 Gain
Bass 1 Gain
Output 2 Gain
Bass 2 Gain
4 dip switches of which there is little or no clue what they do (they are presumably for the Chosen Ones to adjust ;-)

ADR-4 (not 6) photo here: http://anim8.com/G2/main.php?g2_itemId=1704

[whayes]

Actually, mine might be an ADR-4 also... I looked at your picture and I think that's what mine looks like. I haven't pulled the organ out from the wall in a while. I was going off memory yesterday when I wrote that. I agree that I don't want to touch anything and screw it up! It's sort of "ok" as it is, just wanted to make it better. Maybe someone who has a lot of experience adjusting the ADR units will reply, or perhaps a previous Allen technician that knows what each of those controls and dip switches does!

[whayes]

I talked to a good friend who is knowledgeable about digital organs and he gave me some insight. I wouldn't call him a specific Allen organ expert, but he has had and worked with many digital organs over the years and knows what makes them tick.

Mine reverb unit is, in fact, also the ADR-4 unit as well, with the same controls as yours, Dell.

As far as the DIP switches, go, I have no clue what they do either, and neither did my friend. After throwing caution to the wind, I played around with them some and saw no difference (that I could tell) with them in either position. I figured that was the easiest thing to play around with first since it would be easy to put them all back in their original position. Mine came from the factory with all four switches set to the "off" position, and after I played around with them, I put them all back in the "off" position.

For the input gain, my friend said that what that control does, essentially, is control how much of the organ's sound actually is fed into the reverb unit. Basically, turning the control more toward the open position feeds more of the underlying sound into the unit. Turning it completely off, I found, does just that, eliminates all reverb just as if the stop tablet was off. Putting it almiost in the wide open position created LOTS of reverb, and I do mean LOTS.

The output gain controls, still unclear as to why there are Gain 1 and Gain 2. Will get to bass controls in a minute. The output gain controls appears to control how long of a delay the sound that's input lingers. I played around with moving both controls separately but again, couldn't tell any audible difference, so I decided to start moving them in tandem so that both of them were always in the same "position" if you will. The key I found is to play with it enough so that just enough sound is input through the input gain control, and lingers just long enough by controlling the output gain.

For the bass output controls, I deduced that it controls the "linger" of the low frequencies only. Turning those in the fully on position made the low pedal notes linger a long time and gave the effect of a lot of bass resonance in a very acoustically live room.

So, in a nutshell, the key is to feed just enough sound into the unit, and then control that portion of the sound's resonance through the output controls. It definitely takes some playing around to get it all snychronized together and sounding realistic. One can turn the input gain all the way up, output gains all the way off, and have no reverb, or vice versa, so finding that middle ground seems to be an art!

I finally wound up with this sort of adjustment...

The input gain feeds I'd say, about 25 to 30 percent of the sound into the unit. So the knob is adjusted about one quarter turn "open" if you will. The two output gains are probably about halfway open. The bass gain controls are probably three fourths, or perhaps a little more, open. The overall sound I'm fairly pleased with. It's better than it was. I will say, the softest stops on the organ (the Viole and Viole Celeste in the Swell and Erzahler and Erzahler Celeste in the Choir) still don't have as much reverb as I'd like, but adjusting the controls to give those stops enough resonance makes the overall effect very unrealistic when played with louder flutes, principals, and VERY much so with full organ. The Festival Trumpet seemed to blare on forever and playing a fast passage on it made it sound like a bad, muddy recording in a gymnasium! I worked for about two hours to find the "happy medium." I like the additional bass resonance. The way it's adjusted now, the upper partials linger about as long as the deep pedal tones do and overall gives a pleasing result. I love it with the 32' stop on, the sound continue to rumble for a couple of seconds and gives the impression of a vast space.

I'm sure others may be able to comment in a more technical way than I have, but that's what I learned by talking with someone and just plain trial and error. I consider John to be an Allen organ expert. Maybe if he reads this he might have a few more insights. He wrote a comment on one of my posts earlier and said he services some organs of the same model I have, so he might also be familiar with the reverb unit in ours. Perhaps he knows what those darned DIP switches do!

[davidecasteel]

First off, let me disavow any knowledge on this instrument. However, a thought occurred to me about the "Gain 1" and "Gain 2" controls: could it be that one of them sets the reverberation time for loud sounds and the other does it for softer ones? Unless one specifically checked to see those effects it might not be noticed.

David

[DellAnderson]

Will - first off I want to thank you for an astoundingly straightforward explanation of what must have been an arduous 'chinese-fire-drill' of adjusting and testing and adjusting and testing. I know because I did some myself, but you took it to the level of an artform. Bravo! and Thanks.

I too await expert input about the DIP switches, but I wouldn't be surprised if they were only for use on different model organs and were used to adapt the system to our organs. On my organ's ADR-4, #1 Dipswitch is ON all the others are OFF and if I recall correctly that is how it came to me (used).

As for Gain 1 and Gain 2, David may be onto something with the loud and soft sounds, although it occurred to me that it may simply be a crude way to add an extra 'virtual reflection wall' - perhaps there is a slight difference in attack delay or decay on one more than the other. Other than that, another possibility I thought of was different tone, but that's pretty well covered with the Bass adjustments.

But the most likely possibility, if I recall correctly from my tests, now that I think of it, the two gains may allow better shaping of the falloff. In other words, one gain could be set to a short reverb and the other to a long reverb, causing a LOT of reverb initially and then a long tail of much softer reverb. By adjusting the length of the shorter one, you can adjust the falloff slope of the reverb and possibly make both that trumpet and the flutes sound good. This actually seems like the most straightforward explanation, but it is only a hunch based on much more limited testing than you did so I defer to your opinion on this.

Another thought - is there an adjustment for the volume on your flutes and celests and trumpets? Perhaps you could balance them a bit better (I don't know anything about voicing or registration, but I read somewhere you should be able to mix and match most stops and not totally lose any of them in the ensemble. But I'm sure the trumpet might be an exception.

[whayes]

Dell and John,

Those are some thoughful insights into the reverb, let's see if we get any other comments.

On voicing, yes, there are multitutes of voicing adjustments on the MDS organs: separate controls for each channel for gain, bass, midrange, treble, and a "wind" control that injects a breathy pipe-blown wind sound into certain voices on each channel.

In a nutshell, I have eight channels in two separate cages that are independently voiced that make up the approximately 50 ranks in the instrument... so... that means about six voices are grouped together on each channel. In case anyone who reads this wonders, I do have the cage chart, so I have the roadmap to what is contained on each channel. I haven't done a heck of a lot of voicing myself because the Allen techs spent many hours on two occasions voicing it. What's interesting that I posted on the "Pipes vs Electronics" thread, is that the grouping of stops on each channel doesn't make much sense to me. For example, on the choir, the loudest stop on the entire organ, the 8' Festival Trumpet is on the same channel as the softest stop on the organ, the 8' Erzahler. That just seems sooooooo odd to me. That's also true for almost all the channels. There's always a "loud" voice in the same group with a "soft" voice, so balancing them is VERY tricky. It's just as tricky as this darned ADR-4... You have to get just the right amount of gain to balance the entire channel with the other channels, then tweak the midrange to make the "big" voices project over others, but adjust the bass and treble so, for example, the Erzahler doesn't become louder than the 8' Principal on the great! I'm telling you, it's enough to make a man pull his hair out, and I don't have much left to pull!

Also, my MDS has sub and super couplers on it, and those tones are voiced separately (on yet another channel) from their unison counterparts, so that comes into play also. One could have the unison stops voiced beautifully, but put on the super coupler and you might have "super" mixtures and a 4' Clarion screaming at you! The Swell took hours to voice it just by itself.

I'm rambling, but, what I guess I'm getting at, is I don't think there's any way to really increase the volume of the flutes and strings and such, without increasing the volume of the louder stops as well, and right now, I'm not willing to fiddle with that because I'd probably get it so out of whack I'd be calling the Allen folks screaming HELP! I ought to just call my Allen tech and ask him about the reverb unit. He's been very, very helpful to me. But they have admitted that they have forgotten a lot about the MDS-series organs because most of them have been in place and voiced for years and they don't do much with them anymore. All the Renaissance and Quantum instruments are voiced through a PC with software and the Acoustic Portrait system has replaced our "lowly" ADR units...

[jbird604]

Will and Dell,

I posted a comment on that "pipes vs electronics" thread concerning (Will's) Festival Trumpet issue. Please read that, as it has the actual solution!

RE: the dip ADR-4 switches. Ignore #4 for the moment, as it has something to do with pre-delay. According to Allen, it should be set off if the Reverb speakers are in the front (i.e. mixed into the main channels) and on if the reverb has its own amp and speakers. Not sure you'll hear much difference.

Switches 1 through 3 determine the reverb length. The reason you noticed no difference when switching them around is that the reverb tab must be toggled off and back on each time you make a change to hear any difference. That is to say the system "reads" the positions of the DIP switches each time the tab is turned on, but otherwise does not notice when you alter them.

Maximum reverb length is with all three in the "off" position, and shortest reverb time is with all three in the "on" position. Other combinations result in something between the two.

Yes, Will, it is a bit odd the way they divided up the stops. The idea was that only two or three of the stops in each group is a major part of the foundation ensemble, so the workload of most registrations is spread evenly among the 8 generators and audio systems. In normal playing, for example, one would probably not draw both the Erzhaler and the Festival Trumpet at the same time, so that particular DAC is unlikely to be forced to output more than one or two stops at the same time, maximizing the realism and individuality of the stops.

As far as the two output level controls on the ADR-4, there are two independent reverb units in the box, and each one is feeding a separate audio output, therefore being fed into different audio channels. In some setups it might be necessary to have one of the reverb channels louder than the other one, but in most cases the two controls will be set about the same. The bass controls function as you have discovered, letting one adjust the amount of bass sustain to simulate a larger or smaller "church" or space.

Keep up the good work, guys.

John

[whayes]

John,

Thanks you for those very thoughtful and informative insights. I've worked with electronics and computers and home theater audio systems over the years, but NEVER digital/electronic organs until I got mine! Now Dell and I have all the knowledge of what everything does, so he and I both can go back and do some more tweaking!

After I played around with my controls the other day, I practiced for a while last night and I think I've wound up shortening the overall reverb time and it sounds dry. Think I'll be pulling the mammoth console away from the wall tonight and fiddling with it again. At least now I know what I'm doing!

[whayes]

I had to update! Changing those DIP switches makes a world of difference. It now sounds wonderful.

Dell, perhaps try it with DIP switches 1, 2, and 4 off, and 3 on. Then adjust the input and output gains. Remember as John said to switch the reverb on and off after making changes. I forgot that a time or two in doing it! Forgetful in my old age of 39! I also made sure to always change both gain controls 1 and 2 so they were always in the same relative position, and did the same with both bass gain controls.

One thing I did find, pushing the gains up above about halfway did create an ever so slight "hiss" through the speakers. The higher up it's turned, the more hiss. Granted, in a normal church setup with speakers a long way away, you'd never, ever hear it, but in my confined living room with the speakers 10 feet away, it could be heard. I adjusted the gains down just enough so the hiss was barely audible and not distracting to me. I have dabbled with audio systems and home theater for years and even the slighest amount of hiss in an audio system drives me bananas.

But now, I have wonderful reverb across all stops, softest and loudest. The "boosted" pedal decay now balances with the upper partial decay. Also, one cool thing. When I hold down a pedal note for more than a second or two, it seems to emphasize the fundamental, and gives the bass an extra boost as it would in a large resonant room, even before the note is lifted to decay.

I have a whole new respect for the reverb unit now. Perhaps there may be better, more modern units out there, but this one does just fine for my purposes.

Thank you very much John. I knew if anybody would have the solution, it would be you!

[jbird604]

Wow. I never knew that little ADR-4 had such possibilities. I've never tried to make one sound any better, just because they're always in churches and the natural reverb is usually plenty.

Thanks for sharing your experience.
John

[Admin]

in

One thing I did find, pushing the gains up above about halfway did create an ever so slight "hiss" through the speakers. The higher up it's turned, the more hiss.

The way to reduce hiss is to optimize the input gain by playing full organ and raising the input gain until you hear distortion in the output. Then back off until the distortion is gone and adjust the output gain for the desired amount of reverb.

There are scanned Allen documents in the Gallery that describe how to configure a TAS unit which I believe you'll find of interest.

[DellAnderson]

Just a quick note to acknowledge the incredible contributions made here by Will, John, and Admin. I'll have to study the TAS info, but I am not clear how much correlation there is between the ADR-4 and the TAS - is the TAS the successor to the ADR and thus of interest mainly by analogy? Or is the ADR a component of a more generalized TAS system?

Overall, this is the kind of information that any conscientious home organ owner really should treasure, and I don't see any reason why Allen Co. should care that we know how to adjust our own organs. Sometimes daily! ;-)

It is on my ToDo list! (I found the bass reinforcement aspect mentioned by Will especially attractive).

[Admin]

TAS - "Total Ambience System" is Allen's first gen reverb system. It features reverb and chorus generation in the same unit and is bit more complex in it's config options. The document I mentioned talks about the placement of reverb speakers as well as how to adjust it.

[sadatoni]

I remember having a TAS installed on a MOS-1 TH-436 back in the late 70's.

Are those instructions on reducing hiss (a couple of posts back) also usable for the reverb in the W5 cages (in my case, an MDS-317)? Adjustments are:

OUT GAIN ------------ 1 ---------------------- BASS

OUT GAIN ------------ 2 ---------------------- BASS

INPUT GAIN -- -- TREBLE