Measuring Reflection Points in the Impulse Window

Sonder

Member
Supporter
Thread Starter
Joined
Dec 17, 2018
Messages
12
Hi could anyone help please, I am trying to understand measuring the distance for reflection points. Attached is a sweep taken with the loopback in, it estimated the mic from speaker is approx 70cm, which is spot on.

So am correct in assuming the red vertical dash is the first direct wave from the speaker (0u being the speaker), this also tallies with my measuring tape. But when I measure from this to the first big peak, it says 1.649m - where should I measure this from; the speaker, or from the mic, and what is this spike, there is nothing around that is 1.649M away, this is where I am confused?

Any help much appreciated.
 

Attachments

Last edited:

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
2,290
1.649m is the additional distance the reflection had to travel compared to the direct signal from the speaker, so total path to the mic is 2.349m.
 

Sonder

Member
Supporter
Thread Starter
Joined
Dec 17, 2018
Messages
12
Many thanks for the reply John, just so I am clear I have attached a small drawing in an attempt to understand the reflection points.

Would I be correct in saying that theoretically the round trip is 226cm - and REW is showing the exact 235cm as attached?

Thanks again for an amazing piece of software.
 

Attachments

Sonder

Member
Supporter
Thread Starter
Joined
Dec 17, 2018
Messages
12
Thanks, so when trying to establish where the reflection is alway measure from time 0, would this be the best way to establish location?
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
2,290
The t=0 position depends on what was used as the timing reference and any relative delays between the reference and the measurement channels. Probably easiest to just add the distance from mic to speaker to the distance corresponding to the time from the direct peak to the reflection peak.
 
Top Bottom