MiniDSP FLEX/REW Acoustic Timing Reference - Two impulses in a single sweep?

[Calypso1]

MiniDSP FLEX and REW - Assistance needed. I am trying to setup one speaker as a timing reference, however despite all the changes in configuration and REW settings I continue to get two impulses for a single sweep. I also setup REW on my Mac and ran it from there but to no avail, two pulses observed. Also, tried switching the timing reference from the left to the right speaker, also no change.

Thanks in advance

 

[Broma15]

Hello Calypso.

I remember having this once, when i switched back from loopback measurement to acoustic timing ref. I forgot about the connection between IN/OUT.
And
Are you measuring close to a wall?

For me it is looking like this, when i place the microphone 20cm away from the back wall. For this measurement i used the settings you showed.

B.

 

[Calypso1]

Hello Calypso.

I remember having this once, when i switched back from loopback measurement to acoustic timing ref. I forgot about the connection between IN/OUT.
And
Are you measuring close to a wall?
View attachment 356870
For me it is looking like this, when i place the microphone 20cm away from the back wall. For this measurement i used the settings you showed.

B.

Yes, I am measuring close to a wall so I will try moving the mic away to see if there is any change. Which measurement setting were you using, loop back or acoustic reference?

 

[Broma15]

I was using acoustic reference.

 

[Calypso1]

Ok, I moved the speaker inwards (away from wall) and moved the mic (away from wall) and it has had an effect. I changed the scale and correctly if I am wrong, but it almost looks like a reflection as it repeats itself. See attachment.

 

[Broma15]

Ok, you moved the speaker and the mic. For transparent measurement its good to change only one by time. You now have different reflection from the speaker in your measurement.

 

[Broma15]

If your listening place is close to the backwall you could use a blanket on the wall for measurement, to lower the reflection.
But you should be ok now, using timing reference.
And your measurements are good examples how reflections behave.

 

[Calypso1]

Ok, you moved the speaker and the mic. For transparent measurement its good to change only one by time. You now have different reflection from the speaker in your measurement.

Apologies, I did in fact just move the mic, then speaker to see the changes. I posted only the version where both were moved. I will moved back slowly to the starting position and use something "pillows" to absorb some of the energy that later leads to the reflection. Thanks.

 

[Calypso1]

@Broma15 - Setup a few pillows behind the mic, re-measured, calculated the delays, inserted back in MiniDSP, re-measured, See attached impulse of the left and right speaker impulses overlaid.

 

[Broma15]

I am not an expert but i think you did good, when your goal was to time align them.