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CCRMA Classroom (Surround) Sound System 2018-2021

Historic documentation no longer current

During summer 2018 we temporarily upgraded the CCRMA Classroom’s sound system from 4 to 6 audio channels of [Mackie HR824][HR824], with the beyond-stereo channels accessible only from the Linux Machine. In summer 2021 we went back to stereo as part of a revamp to accommodate Ballroom overflow seating; there is no surround in the Classroom as of 2022.

We aspire to 8 or more along with additional acoustic dampening (to control the excessive reverb).

Only the Classroom Linux machine can access the surround speakers, via a MOTU 1248 in the rack with the “Extron” (remember that this historical documentation predates the Kramer) system, below the document camera.

(Maybe someday a KVM switch will mediate laptop access to this MOTU (as in Studio D), but not yet - consider JackTrip as a way to get multichannel sound from another computer (your laptop) to the 6 speakers via cmn8.)

As in every other CCRMA multichannel space, the channels are numbered in stereo pairs from the front to back of the room. So with 6 channels that gives:

  1. front left
  2. front right
  3. mid left
  4. mid right
  5. rear left
  6. rear right

(Note that “left” and “right” are from student/audience perspective (as you look at the projection screen), which is the opposite of the instructor perspective (as you sit at the desk looking out at the students).)

The front stereo pair is fed from the “Extron” switching system, so that those two speakers can flexibly play stereo from multiple sources, with gain control and audio mute functions on the little touchscreen. Therefore to use surround you must select “Linux” on the Extron system (under “Audio”) - otherwise a different audio source (likely silence) will come out of the front speakers.

The gain control for the four surround speakers is controlled by a vintage bespoke 4-fader gain control box (built ages ago by Jay). The faders all have labels like “Linux #5 / rear left”. (The gain for the front two (as a linked stereo pair) is via the Extron touchpanel.) There’s no calibrated way to keep all 6 channels’ relative volumes the same; it’s on you to set the levels to balance the 6 channels properly.

This page of CCRMA documentation last committed on Tue Dec 6 09:37:03 2022 -0800 by Matthew James Wright.