Sunday, 2 June 2013

An evening of experimenting and measuring

This evening I have been experimenting further with the room's acoustical properties.

I started with moving one of the subwoofers forward about 1 meter and 0.5 meter to the right so it's against the wall. It is still facing forward though.

Unfortunately I haven't saved any measurements and I can't be arsed to make new ones now, so I might add a picture tomorrow or some other day. The big differences were that the problems at around 100Hz was reduced drastically and the peak at ~50Hz reduced slightly. Of course I added a time delay to the subwoofer so they are acoustically aligned.

I used the EQ-function in REW to get the proper values for the EQ biquads. REW's graphical interface is still going crazy even though I have updated Java and my grahpics card drivers. I don't know why, but it's annoying as hell. I managed to export the filter values though and I imported them to the MiniDSP. The Q of the EQ bands were much lower now than before, which of course is good, and in general less EQ was needed. I got a much more flat response now and another "dimension" has been added to the music now that I have the 100Hz region playing along as well.

I think I mentioned before that I had an electrical buzzing sound from the Behringer and that I was going to send it back. Well, I haven't heard any buzzing at all today. I will wait with sending it back, the shipping label is valid for another ~3½ weeks so there's no hurry. And if I shall send it back I will wait a couple of weeks and send it just before I go to Germany for ten days.

Another thing I did was to see the impact on the sound when adding lots of pillows and cushions to the room. I did two measurements, one without pillows, and one with pillows.

Without pillows the room looked like this:

And this was the measurement.

If you wonder why the subwoofers are still in the same place as before it is because I did this experiment before I started moving the subwoofer. The measurement is with the subwoofers playing and the EQ active. Take note on how the bass is somewhat flat actually. Ignore the black line, that's just the microphone calibration curve which I forgot to hide.

I then proceeded with filling the room with pillows. I couldn't get the whole room in one picture but there are more pillows to the right which aren't visible.

And this is how it measured.

Much less phase issues than without the damping, and the dips in the midrange are not as severe as before. High frequency levels are slightly reduced, not much though.

Both at the same time. Blue before, green after. No smoothing.
1/24 smoothing. Blue before, green after.
Conclusion: Did it sound better? Well, I'm not sure. Arbitrary damping might be good and it might make things worse. The measurements show that the damping reduced some phase issues and reduced the amplitude of the dips in the midrange. Another thing I did not include was reverberation time. I don't know how to measure that so therefore I decided to leave it out. Though my ears could tell me that there was much less reverberation with the pillows than without them.

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