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.

Hours with REW and the MiniDSP

I've spent most of the evening playing around with REW, the MiniDSP and my UMIK-1.

I started with measuring the response. Pretty flat since I had already set the main EQ stuff a couple of days earlier. But there was lots of room for improvement and I still have some nasty stuff going on at ~90-400Hz.

Today I have tried different crossovers, inverting phase and fine-tuning the EQ. This is the result so far, presented with 1/24 smoothing.

Right now the subwoofers are crossed over at 120Hz with a 24dB/octave Butterworth filter. The main speakers are crossed over at 80Hz with the same type of crossover as the subwoofers. Might be it's better to set it a few Hz higher to flatten the tiny peak at ~84Hz. And by the way I don't think the graph can be trusted below maybe 30Hz because right now the fans of the Behringer amp is blowing straight towards the mic (I have the muff on) but the background noise is slightly high because of it.

I also noticed an electrical buzzing sound coming from the Behringer, from behind the power button. It doesn't sound very healthy so I'll contact Thomann about it. I don't want to switch fans if I have to return the amplifier.

Speaking of fans I have decided to use Fractal Design 1400rpm 80mm fans. I bought one for cofffee-money from my friend Robin and I have ordered a second one from CDON. Hopefully it will arrive before the weekend. While searching through my boxes for some cables I stumbled upon two pairs of Noctua low-noise adaptors (basically a 3-pin 10cm extension cable with a resistor mounted on it) which will come in handy if I need to reduce the RPM of the new fans.

I guess I don't have to say it sounds really good now that the massive 50Hz peak is gone. There's more nuances in the bass now, it's not that one-note bass any longer.

Edit: Here's another picture with phase included.

Something is happening there at ~100Hz but I know too little about phase to draw any conclusions. My guess though is that it's because of the room dimensions.

Edit #2: I did some close up measurements of the right channel speaker.

This is with the mic 10cm from the upper woofer, on-axis. Only right channel speaker playing and being measured.

This is with the mic 10cm from the tweeter, on-axis. Only right channel speaker playing and being measured.

And here's a picture of both main speakers running full-range without crossovers and EQ.

As you can see the room has a HUGE impact on the sound. Close-up the speakers are pretty flat but ~2.8m away they are anything but flat. Room acoustics are important, very important...

A package from Thomann arrived

A package from Thomann arrived yesterday. As usual it was five time bigger than needed and so it was stuffed with those huge bubble wrap things. Great, now I have another 15m of it.

The package contained a Behringer iNuke NU6000 and a microphone stand. I unpacked the Behringer yesterday and put it in the shelf but I haven't gotten the MiniDSP plugin yet so there's no need to hook it up yet. I tried the microphone stand though and I did a quick measurement in REW at listening position. Unfortunately I forgot to save it but it looked quite similar to the measurement I did before. Above 400Hz it is acceptable but below ~200-250Hz it goes all crazy. Hopefully I'll be able to fix most of it with the MiniDSP and subwoofers.

Quick measurement of in-room response

Here's a quick measurement I did yesterday. Since I haven't got any microphone stand I had to hold the mic in my hands, which could have had some impact on the measurement. It looks similar to what I have measured before. With my MiniDSP I will try to tame the huge peak in the bass but I don't think I will be able to do much about the dip at 100Hz because it seems to be some room cancellation. Same with the dip at 200Hz. But I don't think the dip at ~650Hz is a room cancellation, any clues to what it may be?

The MiniDSP and UMIK-1 has arrived!

Hello dear readers!

The MiniDSP and UMIK-1 arrived today. I have been very busy though so I haven't had time to try the MiniDSP and I have only tried the UMIK-1 for a quick voice recording (which sounds very promising!). I don't know if I will have time tomorrow, but if I do I will put up some pictures and maybe a recording as well.

Initital impressions of the UMIK-1:

• Heavy and well-built! Well, not heavy but it's no cheap plastic stuff
• Nice little table stand, feels quite sturdy and easy to use and fold.
• Very easy to use. Connect the mic to the computer via the USB-cable that was in the box and you're ready to go. No additional software needed.
• Crystal clear voice recordings

I just did a quick voice recording but from what I heard I think I will use it for not only measuring speakers and room acoustics but also for Skype and Teamspeak. I don't know the directional pattern of the UMIK-1 but I guess it's a bit more narrow than the Logitech C270 webcam that I use as a microphone at the moment.

Here's a picture from the manufacturer.