Hi all!

I have access to a space with 8 speakers, they are in multiple rooms:

The gear (showing for 6 speakers)

I want to use pure data to control the volume of each room and to also select stereo or mono (or even try to play with 4.1 for ambisonics).

Here's what I have in mind for the patch:

ADC~
---
Gate
EQ
COMPRESSOR
hip~ (remove DC)
LIMITER
Mixer
VU meter
---
(stereo, mono, 4.1?)
---
DAC~ 1-2, 3-4, 5-6 with high pass (for channel using subwoofer)
DAC 7-8 for subwoofer with dedicated low pass (built-in in amp but fine-tuning)

Questions:

• Am I forgetting something important in the chain?
• Is there a patch out there to do Room calibration?
• Speakers are pointing at each other in the first room, I had in mind to invert the phase (the cables) but maybe I can use pure data to control that too (not sure)?

@whale-av I recall a patch you uploaded on this forum (like a mixer patch). Would it be interesting for me to use part of it?

Thanks for any advice!

@EEight My mixer was for in-ear live on stage, the musicians using TouchOSC to control their earphones. So everything was mono. You are welcome to try it of course, and change it as you need. But although there was input and output eq there were no effects. It might be useful though for you to have Wi-Fi control while you are setting up.

I think you will find what you need (mostly) in Automatism..... all the eq and effect modules..... but I haven't seen an automatic room flattener. It is easy enough by ear though using a sweep generator.... sweep-explained.zip or easier still by humming, singing, whistling and "tssss'ing" with a microphone. You will hear the room resonance sing out at the frequencies you need to cut, and it's better than using pink noise as a source. You get the inaccuracies of the speakers at the same time.

You will have to spend some time setting up though. The real problem eq'ing a room is the comb filtering at lower frequencies.... much worse than the room or the speaker response because you can hear a note loud and then take one step and you can't hear it at all. The more speakers you have the worse it will be, and speaker placement is the most important factor. Really you need a room with very little reflective surface and the public should be listening to only one speaker wherever they are. It's ok'ish in a home cinema because you sit in one place and delays can be set to adjust the relative timing between speakers, but you will have noticed that public cinemas have soft furniture and each sound comes pretty much from one speaker as delays don't work for an audience sitting everywhere in the room.

It's probably worth at least slowing down the sweep, or having manual control, as it takes time for the room to get humming sometimes.
The vocal method works really well..... like when you are humming in the shower..... you really hear those room resonances coming back strong....
David.

@EEight Just to add on to what David said, multiplying an audio signal by -1 is the same as using a phase-inverted cable.

As usual thank you for all the informations @whale-av
@jameslo Perfect, I will be able to use a toggle in pd to invert the phase then!

I am currectly looking at those solutions for room calibration, I simply don't have a good ear

• https://www.roomeqwizard.com/
• https://torger.se/anders/brutefir.html

Have a good one!

@EEight Regarding room calibration, it may not matter, depends on the situation. People absorb sound and affect the room, if the room is going to be full of people and it is a small room all your work could do more damage than good, but if it is a big room and there will never be more than a few people in it there could be a real advantage.

Regarding phase, phase cancellation could be a benefit if people are going to be walking through the room, increasing phase cancellation will make the sound more dynamic as they move through it. But lots of variables, depending on room size, what is being played, volume and a good number of other variables you may get more cancellation with the phase inversion on one channel. Sort of thing which takes some experimentation to figure out what works best for what you are doing.

@EEight The REW wizard is great software..... I would recommend that especially as it is free and powerful with great forum support
Phase inversion of treble frequencies can make you feel dizzy as you move your head...... we are much more sensitive to phase than other audio information.
Just one treble speaker in a stack is instantly horrible...... not so noticeable if the speakers are further apart though.
If you had more than one sub you would need much more tuning...... moving subs around until it sounds good everywhere is an everyday challenge on tour....... a few inches..... or less... can make a big difference.
David.