To delay or not

[linuxonly]

Hi.

Following @moedra tutorial https://www.avnirvana.com/threads/convolution-room-correction-and-room-curve.14005/ using one set of measurements and IR filters for the listening room where the front speakers are equidistant from the MLP, I'm getting used to it after repeating the process again and again for refinement.

In the same listening room however, I have a 2nd listening position facing a 2nd screen (computer screen at 90 degrees left from the main). I took another set of measurements with the mic positioned where the seat is and generated new IR filters. One speaker is 3 ft away from the seat whereas the other (the reference) is at 9 ft. I wonder whether or not I shall apply a 6 ms delay to the closest speaker to get them in phase again? Maybe it's already part of the correction, I'm not sure about that. The speakers are screwed on the walls so moving them is not an option. On top of that their position is already optimized for the first case. In case one wonders how it's possible to turn left 90 degrees and still have FL and FR speakers, I remapped the FL channel to the RL speaker and the FR channel to the FL speaker. In other words, I'm facing the left wall. I have a different CamillaDSP for each case and I switch depending if I watch a movie, listen to music (main, facing front) or play a game (at the keyboard, facing left).

 

[linuxonly]

Another question.

I took measurements for 6 speakers on a 5.1 system and for each speaker I got something like

Delay 3.9500 ms (1.355 m, 4 ft 5.3 in)
using IR start time relative to Acoustic reference played from LINE_OUT L with no timing offset
Clock adjustment: -232.0 ppm

1 - For given speaker, the delay is not constant. It changes constantly from -2 ms to 6 ms. Why is that?

2 - Let's suppose I have the following results on measurements at the MLP

FL: -0.025 ms
FR: 0.34
FC: -1.96
FLE: 1.99
BL: -0.26
BR: 0.03

How would you apply those delays to CamillaDSP? I tried entering them as they are and got a ' Invalid filter 'delay_l'. Reason: Delay cannot be negative' error, e.g.

  delay_fr:
    type: Delay
    parameters:
      delay: 0.0352
      unit: ms
      subsample: false

I mean what values would you enter to time align? This isn't clear to me.

 

[JStewart]

1 - For given speaker, the delay is not constant. It changes constantly from -2 ms to 6 ms. Why is that?

Not sure.. are you using a usb mic? on the analysis preferences tab is the box checked for:

The Adjust clock with acoustic ref selection controls whether REW compensates for clock rate differences between input and output when using the acoustic timing reference. If this option is selected an additional timing reference signal is played at at the end of the sweep and the time between the timing reference signals is used to calculate any clock adjustment required to match the input and output device clock rates.

2 - Let's suppose I have the following results on measurements at the MLP

FL: -0.025 ms
FR: 0.34
FC: -1.96
FLE: 1.99
BL: -0.26
BR: 0.03

How would you apply those delays to CamillaDSP? I tried entering them as they are and got a ' Invalid filter 'delay_l'. Reason: Delay cannot be negative' error, e.g.

I haven’t used Camilla, but to get rid of the negatives make FC 0 and add 1.96 to every other speaker’s delay.