Should I expect system delay when measuring the timing reference speaker?

[Bebbetufs]

Hello all. I'm new to the forum and looking forward to learning a lot about this excellent software and what it can do.
I have a few questions regarding the acoustic timing reference.

Does not REW use the time it takes to recieve the referenc signal as point zero to which all other speakers are compared? If so should this measurment no be 0.0ms after system delay has been subtracted?
In my system I get very varied results when measuring, say Front Left for tiiming reference and delay. With the mike on the coffee table I get about 0.30ms delay. Moving the mike to a different location changes the measured delay. Moving it one meter changes the measured delay/distance by 40 mm. Should these two not be equal as long as the same speaker is measured.

Also, changing the timing reference to Front Rignt and measuring the Front Right sometimes causes a negative number.

Am I doing something completely wrong?

 

[John Mulcahy]

The timing reference signal is played back by the tweeter, there are often small timing alignment differences between the tweeter and the full speaker response.

 

[Bebbetufs]

Thanks for the quick reply. Much appreciated. I should have considered that. I will have to do more measurements to verify I get repeatable results.

Could room modes and reflections severely throw off the timing measurement when the mike is placed close the rear wall or in a corner?

 

[John Mulcahy]

Could room modes and reflections severely throw off the timing measurement when the mike is placed close the rear wall or in a corner?

Reflections can have an influence if they are large.