I made several sweep measurements on SB26ST-C0000-5 tweeters and two phase curves was generated within each drivers.
Note that SPL curves are the same.
The first one happened a bit more often. I was questionning myself if it's the drivers or something else causing this.
I decided to test the woofer to compare. There was only one phase curve.
I tried other repetitive measurment on Mirage m790 HF portion and I obtained two phase curves again.
All the previous measurements was made with Omnimic V2 and laptop directly plugged in Cambridge audio 640A V2 (I also replaced faulty relays with no change in measurement) at 1 m.
I wanted to be sure that these two initial measurements were good. So I tried repetitive measurements on my other system (Monitor Audio BR6, Moon 220i and Moon 300D). There was only slight variations on phase but nothing alarming. I also tested the famous SB26ST-C0000-5 on the same set up (except the speakers duhh..) and the two same phase curves was identical to the first ones.
Not sure of what was going on.
So... does anyone ever seen this issue and is it the drivers that cause this?
Thank you.
Note that SPL curves are the same.
The first one happened a bit more often. I was questionning myself if it's the drivers or something else causing this.
I decided to test the woofer to compare. There was only one phase curve.
I tried other repetitive measurment on Mirage m790 HF portion and I obtained two phase curves again.
All the previous measurements was made with Omnimic V2 and laptop directly plugged in Cambridge audio 640A V2 (I also replaced faulty relays with no change in measurement) at 1 m.
I wanted to be sure that these two initial measurements were good. So I tried repetitive measurements on my other system (Monitor Audio BR6, Moon 220i and Moon 300D). There was only slight variations on phase but nothing alarming. I also tested the famous SB26ST-C0000-5 on the same set up (except the speakers duhh..) and the two same phase curves was identical to the first ones.
Not sure of what was going on.
So... does anyone ever seen this issue and is it the drivers that cause this?
Thank you.
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It is more likely something to do with sample timing on the measurement. Since those are 'open loop" and the system derives zero from the signal a sample delay of one sample will move the phase significantly at high frequencies. If you adjust the delay in each measurement to get a constant (or almost constant) phase look at the two numbers for delay. I suspect they will be microseconds (or really small) and not significant.
But if it is timing, I should have this with every driver I measure, no? With the monitor audio, I get the same phase curve every time.
I use REW for measument and impupse window are applied to eliminate room effect.
I use REW for measument and impupse window are applied to eliminate room effect.
If you overlay the curves, can you adjust the delay of one and end up with both looking the same?
It works! I selected the two curves and clicked Tim Align. Now the phase curves look similar. I guess that you should time align all together every measurements made for xo design.
Thank you very much I'm so glad it's not the gear causing this.
Thank you very much I'm so glad it's not the gear causing this.
No, this depends...
However what is important is that you have more control of your data. The next step is to recognise that acoustic measurements in REW are most effective with a dual channel approach.