Measuring with a timing reference

[John Mulcahy]

The system being measured includes the soundcard, so the response includes the soundcard's response. The idea of the loopback calibration is to measure the soundcard on its own so its response can be removed.

 

[sm52]

This is the measurement of a single four-speaker enclosure. In one screenshot, t = 0 shifted so that the phase response at 22 kHz = 0 degrees. On the other screenshot, impulse at this t = 0. Did I set t = 0 correctly? REW itself sets the Ref point to the second negative peak of the impulse, and t = 0 nearby.

 

[sm52]

I tried to make measurements of the mid-range speaker in own box according to scheme 2 from post #1. Divider - 10 kOhm and 1 kOhm resistors. The delay is always = 0. Unlike measurements according to scheme 1. There, the delay varies with each measurement. Sometimes it turns out (usually after 30-40 minutes of work) to get several measurements in a row with a delay = 0.
But. When using scheme 1, the GD is always around 0. When using scheme 2, the GD increases greatly after 15 kHz. GD of one speaker should always be = 0. I think because of the resistors. If interested, I can give measurements.

 

[sm52]

John,
hello. Question-proposal on acoustic synchronization of measurements. Sometimes, for some reason, the frequency of the preliminary high-frequency signal is not very well reproduced by the high-frequency driver, which is selected as a reference. Or it is not possible to use a separate HF driver. Or this frequency is played by two drivers - mid and tweeter together. Can the user be given a choice of the pre-tone frequency? Or there are several options to choose from, such as 5 kHz, 8 kHz or 10 kHz. Or from some range, for example, 5 kHz-12 kHz.