Does Acoustic Timing Reference Send More Than a Chirp

[martins5]

In another forum I was working with an individual who is using the center channel for the acoustic timing reference. He was asked to measure the sub only for the left channel. He disconnected his left speaker and ran a full range sweep to 20khz. Surprisingly, the sub only sweep showed response to 20khz, but at a reduced level. I'm suspecting the timing reference was causing the center channel to respond. When acoustic timing was turned off, the same sweep showed just the noise floor out to 20khz for the sub only sweep.

The question is whether REW just sends a chirp to the acoustic timing reference channel or does it send other content?

 

[John Mulcahy]

The timing reference channel only gets the timing signals unless it is also the channel being measured.

 

[martins5]

The timing reference channel only gets the timing signals unless it is also the channel being measured.

What do the timing signals consist of?

 

[John Mulcahy]

5 kHz to 20 kHz linear sweep. They are used to synchronise capture and check clock rate, they are removed from the signal analysed to produce the measurement.

 

[martins5]

5 kHz to 20 kHz linear sweep. They are used to synchronise capture and check clock rate, they are removed from the signal analysed to produce the measurement.

Much appreciated.

 

[AudiocRaver]

It is not unusual to see reduced-level frequencies clear to 10 kHz and beyond in a full-range sub sweep. It depends a lot on the steepness of the low-pass crossover slope, the dynamic range of the measurement plot, as well as other aspects of the subwoofer's (and amp's) design.