QUATTRO MEASUREMENTS

- the raw drivers -

Left: Complex response of 8008 driver in cabinet created from merging nearfield response at 375 Hz and adding the response coming from the port. Reading normalised for 2.8V/1 meter.
Right: 8008 response merged with nearfield response at 350 (red), 375 (black) and 400 Hz (blue). This only to show the image to the left should be taken with a grain of salt.
It all very much depends how we manipulate the data. The purpose here is to get an idea of bass extension and that the system sensitivity should be targeted in the 90-91 dB range.

Left: Tweeter response normalised for 2.8V/1 meter. The dip at 2 kHz can be eliminated by modifying the tweeter, however not relevant to this construction.
Right: Impedance of raw drivers in cabinet. No crossover attached.

Measurements final system

Left: SPL at 1 meter, 2 8 volt. Overall system sensitivity = 90 dB/2.8V/1 m.
Right: Final system impedance. Minimum where is matters is 8.3 ohms at 36 Hz and 160 Hz. 7 ohms minimum above 7 kHz.

Left: Complex response of 8008 driver in cabinet created from merging nearfield response at 375 Hz and adding the response coming from the port. Reading normalised for 2.8V/1 meter.
Right: Final system impedance including electrical phase. Considering the general high impedance and modest phase angles, this is an easy speaker on the amp.

Left: SPL from drivers driven from crossover and summed response. Point of crossover is around 2600 Hz.
Right: Horizontal dispersion of speaker at 0, 10, 20 and 30 deg.

Left: Vertical dispersion measured at 1 meter distance at 0 (red), +5 (blue), +10 (green), -5 (yellow) and -10 (purple). 0 deg is right between tweeter and woofer.
Right: Tweeter attenuation always has to be adjusted to personal taste, room, equipment, etc. Here from R1011 = 3R9 (red), 4R7 (blue) and 5R6 (green). My preference is 5R6.

Left: Step response of final system. Right: ETC plot - if interested.

Left: Impact of midrange notch filter. As can be seen it flattens the response in a narrow range between 500 and 900 Hz. Leaving out the notch filter will produce a tremendous
midrange projection, quite appealing on some recordings, but on certain recordings, we start listening to the 8008 driver rather than the music. A bit too much.
Right: Distortion measured at 1 meter, 2.8V. Distortion lines are raised 15 dB.

Left: Distortion as above shown in percent total harmonic distortion (THD). Right: Same thing thing only 10% scaling.
Red is 2.8 volts and blue is 5.6 volts equivalent to 90 dB and 93 dB @ 1 meter.

Left: Final system CSD at 20 dB scaling. Right: Final system CSD at 40 dB scaling.

Step response of tweeter (blue) and woofer (red) respectively.
Measurement done at 1 meter distance with the microphone at a position between tweeter and woofer.