GLS Control Room Setup
2005-06-13-- Our most recent pink noise test results are shown above. Each graph is an average of 100 samples done using PRAXIS, 1/24 octave bandwidth and a Fast Fourier Transform Size of 65536. The frequency range shown is from about 25 Hz to 20 kHz. Each graph is shown centred on its own measurement position. Click on a graph within the room image for a larger graph of the room characteristic at that position. (To see the scale of the graph in FireFox browsers, click on the large graph, which should enlarge it further.) On the individual graphs the green trace is an omni-directional microphone, and the pink trace is a uni-directional microphone pointed due west (i.e.towards the speaker wall). All measurements are at 46" and 48" from the floor respectively for the omni- and uni-directional microphones. Excellent listening accuracy may be achieved in the area occupied by the graphs when the traces are essentially flat or slightly downward-sloping to the right.
- the `design' room dimensions are 7'x12'x17' [optionally 18'8"] (side walls currently under construction).
- the amplifier is a Crown DC300A Laboratory Power Amplifier Series II (155 Watts/channel).
- the monitors are JBL 4412 Studio Monitors (-4 Hi Freq Control, +0 Mid Freq Control), woofer centres positioned 46" from the floor, 35" from front wall, 114" apart, tilted inwards 35 degrees and downward tilted about 2 degrees.
- ceiling height is 7 feet, front-to-back room depth is 12 feet, room width is 18 feet 8 inches currently open on the south end. The wall is unfinished on the north end and has 3.5 inches of roxul covered with polyethylene. (but construction is pending on some surfaces). The ceiling is 3/4" fir plywood resiliently mounted on 12" OC channels and partially finished in 0.25 inch cedar siding.
- the equalizer/analyzer, a dbx Model 10/20, is shown below left. Each vertical unit is 1dB. Columns are 31.5, 63, 125, 250, 500, 1k, 2k, 4k, 8k and 16k Hertz. Unless otherwise noted, the response measurements are raw data (that is, without any equalization or correction). The dB level is shown in the middle right of the picture (the pink noise for the 10/20 is specified to be accurate to .5dB).
The 1dB vertical divisions are easily seen in some columns as a result of fluctuations
which do occur during the time it takes for the camera to record the image...
a long exposure snapshot!
If you look carefully you may see the reflection in the glass
of the engineer (me) holding the camera.
The desire is to have as flat a response as possible-- i.e. a horizontal line.
The acoustic pink noise response
at the listening position in our control room
at Greenledge Studios on May 12, 2005, after
JBL left speaker was refoamed.JBL speaker
settings are HIGH=+1 MID=-4, as before the repair.
Both speakers, as above.
Left speaker alone(S/N 323071)
Right speaker alone (S/N 272508)
The acoustic pink noise response at the listening position in our control room at Greenledge Studios on May 12, 2005, after JBL left speaker was refoamed, with auto eq
[flatter is better ;)].
The acoustic pink noise response at the listening position on the speaker axis in our control room at Greenledge Studios on May 17, 2005, after JBL left speaker was refoamed, HIGH=-1 MID=-4, using PRAXIS @ 1/12 octave, 65536 points. Raw data obtained using a calibrated Beyer MC740N Microphone set to Omni mode (green trace), and a beyer M88 unidirectional microphone (pink trace). The dip in the response at about 150 Hz is phase cancellation caused by the reflection from the front wall (specifically the wall behind the speakers), which may be corrected by a flush mounting of the speakers. Click the graph for a bigger image (576 x 470).
Super-size (1071 x 874) here.
The acoustic pink noise response at the listening position on the speaker axis in our control room at Greenledge Studios on May 17, 2005, after the left speaker (JBL woofer) repair, JBL settings HIGH=-1 MID=-4, with graphic equalization, measured using PRAXIS @ 1/12 octave, 65536 points. Data obtained using a calibrated Beyer MC740N Microphone set to Omni mode (green trace), and an AKG C451 EB uni-directional microphone (pink trace).
Both the green and pink traces are actual, measured responses of the speakers in the room after equalization (using the different microphones described above).
[flatter is better ;)].
Super-size (1071 x 874) here.
More Information:
Yamaha NS10 Raw On-Axis PRAXIS Data Two-Microphone Comparison
Yamaha NS10 Equalized PRAXIS Data
Comparison of Yamaha NS10 - JBL 4412 Raw PRAXIS Data
JBL 4412 Music Response to Robbie Robertson's The Last Waltz - Cripple Creek
The acoustic pink noise response at the soffit-simulated listening position in our control room at Greenledge Studios on May 23, 2005, HIGH=-4 MID=+0, using PRAXIS @ 1/24 octave, 65536 points. Raw data obtained using a calibrated Beyer MC740N Microphone set to Omni mode (green trace), and a beyer M88 unidirectional microphone (pink trace).
Details (1055 x 684) here.