A more advanced reverb

Third Party Modules.

Requires the TD Allpass Dly2 module.

The Moorer Model of Reverb.

James Moorer’s version improves on Schroeder’s model of reverb, which tends to suffer from the disadvantage of a somewhat metallic sound (unless of course you want that sound).
Moorer suggested the use of low-pass filters in the comb filters’ feedback
path to emulate the sort natural high frequency damping to be found in rooms and halls full of people.
He also generated early reflections using tapped delay lines. Moorer’s reverb model employs six comb filters in parallel, the outputs of which are summed and fed into just one all-pass filter. The image below outlines its schematic.

The Delay and it’s feedback loop.

In our structure each comb filter’s feedback loop includes a one-pole low-pass filter as you can see below: (Moorer Delay prefab). As is usual to have a feedback loop in a SynthEdit structure we need to have a special Feedback – Volts module in the structure to allow this, but although this is going to introduce a delay in the loop this really won’t be all that noticeable in this application.
The only settings of note are:
1) Pitch to voltage: The Pitch control parameter should be set to 1 V/ kHz on all low pass filters. We need all filters behaving identically.
2) The Filters: 1 Pole LPF is all you need in the feedback loop. If we have any steeper cutoff it just won’t sound natural. The filter is only affecting the feedback loop because we don’t want to colour the incoming sounds in any way. We also really don’t want to introduce any resonance into the loop either.
3) Feedback: We need to ensure that the Feedback plug has its parameter set to 0. Because we are using an external feedback loop we don’t wany any feedback whatsoever in the delay module.

Having completed our delay with damped feedback we now come to the structure of our Reverb 6 container which has the structure shown below. This is where we have our six delays connected in parallel, with their structure of delay times.
This prefab employs the same delay times that were originally used by
Moorer: 50 mS, 53 mS, 61 mS, 68 mS, 72 mS, and 78 mS. These values could obviously be changed slightly to allow for different room/hall/ sizes.
Notes:
Delay times: Remember we are looking at reverb, not echo so we don’t want such a long delay that the repeated sounds become noticeably separated from each other, varying the voltages by +/- 0.3V would be plenty.
Consistency: However do keep them to the same time differences to keep the effect sounding consistent.
Suggestion: If you decide to implement a method of changing the delay times to alter the room “size” my suggestion would be to use switching to change the voltages rather than a control knob.
Warning: Do not modulate the delay times as this will introduce unwanted and unpleasant pitch changes,

The voltages set in the Fixed Values module are shown below.

The final structure for our reverb, has two All Pass filters following the Reverb 6 modules just to “smear” the reverberated sound a little, the values used in the Fixed Value for the left and right channel All Pass filters are shown below.

To avoid creating a ringing metallic effect as well as reverb, you need to limit the Maximum Decay parameter to around one volt (using the usual Min/Max settings in the control preferences).