Measurements

[DrWho]

So I finally figured out this Room EQ Wizard program and thought I'd
share some pics of all the measurements I made of my Chorus II mains
and my single DIY Ascendant Audio Assassin 12" driver in a 3.5 cubic
foot sonotube enclosure tuned to 16Hz (man that's a mouthful...I'll
just refer to it as the AES Thor 12.0 from now on...).

The
measurements were taken with a Behringer ECM8000 measurement mic being
fed into a Behringer UB802 mixer and then fed into the Auxillary 2
input jack on the front of my computer. I calibrated the sound card
frequency response by sending the reciever pre-outs into the behringer
- it's not quite an identical signal path, but I'll trust the Denon to
have a flat frequency response. I'm using the digital output of my
soundcard to the Denon and I feel this will be more accurate than
temporarily using the analog output of the sound card. There are some
nonlinearities with the Behringer mic as well (mainly in the high-end),
but this was accounted for with a calibration file I found for the
microphone online. So if my system has a flat frequency response from
10Hz-20kHz, then it should read flat in the program as well.

Here
is the independant frequency response of the Left, Right, Sub, and
summed total all shown on one graph smoothed to one octave:

(note the summed total indicates better summing as you go down in
frequency - I think this is a fault in using a point source for the
measurement - basically, there is destructive interference occuring at
the microphone that is not representative of what the ears hear or what
the speakers are doing).

Here is the Left Channel at 1/24th octave smoothing:

And the right channel at 1/24th octave smoothing:

The subwoofer at 1/24th octave:

And finally the total summed response at 1/24th:

The
blue lines on the other graphs indicate the target response for that
channel. I am running my mains as small, so I want to see a smooth
rolloff that follows the blue line.

I decided not to post all of the graphs I took, but I have uploaded them online for anyone to view at their leisure:

http://picasaweb.google.com/mebentz2/Measurements/

(For those not familiar with Picasa and Picasaweb, I highly recommend you google it and download the free software)

Anyways,
I would be interested in seeing how other people's systems measure up.
To be honest, I am quite impressed with how flat everything seems to
be. I definetly need to employ some acoustical treatment to address the
issues centered around 80Hz. All of the independant graphs were just
that one speaker playing, so it's not the result of acoustical
interference. I also plan to add a second subwoofer to the system and
my mains will need to move as a result. In the process, I hope to get
rid of, or at least mask with superposition those issues. The way my
room is laid out, bass traps will not be an option [6]

Now to get
my hands on a TEF or some other time-based measurement software to
really get into the nitty gritty...I have no doubt that my ISD and
semi-reverbrant field looks like crap []

[DrWho]

Ok, just for kicks...one more measurement. It's the unsmoothed response for each component (like the first graph above). I just thought some might find it interesting to look at:

All those dips in the higher frequencies are due to comb-filtering.

[damonrpayne]

None of the images are showing up for me

[SilverSport]

...and we are waiting for fini and jacksonbart to give us their responses to "measurements..."...[] [] []

Bill

[DrWho]

Seems picasaweb doesn't like it when you link to their database [6] I thought that was going to be an issue when I saw the URL for the images. Anyways, you can still view the whole collection at:

http://picasaweb.google.com/mebentz2/Measurements/

Or you can see the files on my school account without descriptions (but the file names should make sense):

https://netfiles.uiuc.edu/mebentz2/Measurements/

[garyrc]

Dr. Who,

Any advice or helpful hints on how to get the Room EQ Wizard to work?

Thanks.

[DrWho]

read the manual? [^o)]

http://www.hometheatershack.com/roomeq/wizardhelp/help_en-GB/html/index.html