Lexicon MPX 1 Delays
Syncronizing delays to external MIDI clock or just to whatever music happens to be playing can be tricky at first but ends up being pretty simple.

Changing Delay Units
In the old days, digital delays only allowed you to set the delay in milliseconds. If you wanted to use it for any specialized applications (tempo, sound reenforcement) you had to either select the delay time by ear or do the math. The MPX1 did away with that by providing different "units" by which the delay can be set. From the MPX1 EDIT mode, go to the Delay "Time" parameter. Notice that the OPTION button LED just came on? Press it. Turn the KNOB and you see you can select the following ways of setting the delay time:
  ms
  echos:beat
  meters
  feet
  tap ms

When the Delay "Units" you want is selected, press the OPTION button to return to the "Time" parameter where you can edit the delay time in the new units.

ms
This is a standard milliseconds delay units. To provide quick adjustment, two fields are provided: one to adjust milliseconds and one to adjust 100s of milliseconds.

echos:beat
This is one of the more confusing but profoundly useful Delay Units. The basic idea here is that you are defining the delay time as a ratio of echos per beat; "1:1" gives you 1 echo per 1 beat. "2:1" gives you 2 echos per 1 beat. "Beat?" you might be asking yourself. "What beat?". It's funny you should ask.

In the MPX1, a "beat" is defined by a "tempo" value which is stored in each program. The "tempo" is defined in beats per minute (BPM) and can be viewed and manually adjusted from the Tempo menu under EDIT, or by simply pressing the TAP button. Note that the MPX1 has a parameter on the Tempo menu called "Beat Value" which is supposed to change the interval defined by pressing the TAP button to other musical intervals. Tapping in Whole notes for instance. Unfortunately was never implemented by our brilliant system programmer (thats me) so you have to live with tapping in beats (sorry). You can, however, inprove the accuracy of the tapped in tempo by averaging the interval over as many as 8 taps.

Usually you just TAP in the tempo of the music and the "beat" in "echos:beat" becomes a "beat" of your music. Now if you want to produce 2 echos for every beat of your music, you set the Delay Time ratio to "2:1". Some other useful ratios are as follows:
 

1:1 1 echo per beat (quarter note echo) 6:8 6 echos per 8 beats (dotted half note)
4:4 4 echos per 4 beats (quarter note echo) 6:4 6 echos per 4 beats (dotted eight note)
2:1 2 echos per beat (eight note echo) 6:2 6 echos per 2 beats (etc..)
4:2 4 echos per 2 beats (get the idea)    
4:1 4 echos per beat (sixteenth note echo)    
1:2 1 echo every 2 beats (half note echo)    
2:4 2 echos every 4 beats (half note echo)    
1:4 1 echo every 4 beats (whole note echo)    
24:24 1 echo per beat (24 echos per 24 beats)    
23:24 23 echos per 24 beats    

You can really think of them as fractions. Rather confusing but extremely flexible.
 

Note that when there is not enough audio memory in the system, the delay time is divided down to the next available interval (this is kind of a pain cos it doesn't tell you it's doing it so it can be confusing).

meters
The "meters" units allow you to set the delay time based on how fast sound travels through air. Setting the delay time for 20 meters, for instance, creates the same delay as you would hear if you were 20 meters away from the sound source (or if you put one of your amp speakers 20 meters away). If you were using the MPX 1 to delay the sound coming through a PA from the stage to make the sound appear to come from the stage instead of the speakers, you would set the delay for the distance the speakers are from the stage. This is typically used in situations where staggered arrays of speakers provide better sound coverage but lots of echos. By delaying the sound to speakers, ironically the echos are reduced and the resulting sound is much clearer.

feet
Like "meters", "feet" units allow you set the delay time based on how fast sound travels through the air. All of the notes for "meters" apply here except the distance (delay) is measured in feet instead of meters.

tap ms
"tap ms" is the same as simple "ms" except that when the delay time is the selected parameter (blinking on the display), the TAP button can be used to direcly tap in the delay time (no ratios, beats. etc...). The tempo system also contains a parameter which allows foot switches and MIDI controllers to be used for TAP.

Syncronizing to MIDI clock
One of the coolest ways of using delays is to syncronize them to the tempo of the music. The echos:beat section above gets you part of the way there but what if you are already sycnronizing your playing to a MIDI clock driving a sequencer, drum machine or a JamMan? The trick is to set the tempo subsystem of the  MPX 1 to slave to external MIDI clock. Press the EDIT button twice then turn then Knob until "Tempo" appears in the display. Press the > button twice to get to the "Tempo Source" parameter. Set it for "MIDI" and you are set. If your delays are set for echos:beat units, they will be in perfect sync with the incoming MIDI clock. Note that your ratios should match the time signiture of the sequence.

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