I see monitors positioned on the meter-bridge of a mixing desk, sometimes horizontally and other times vertically, which is better?
Firstly, positioning a monitor on the meter-bridge will cause the entire surface area of the mixing desk to vibrate when playing loud music. This will affect the perceived sound quality as energy is transmitted through the desk causing additional sound to be radiated off the console surface and towards the listening position. The monitor should be mounted on stands behind the mixing desk and sufficiently high that the bass driver is not obscured. To reduce mechanical coupling of the monitor cabinet to the consol, the 8000 Series models are equipped with the Iso-Pod™.
Secondly, horizontally orientated monitors positioned on the meter-bridges of mixing desks may look nice but acoustically it is not a good idea for the following reasons:
Mounting the monitor vertically increases the distance and angle of the off-axis reflection from the console surface. This reduces the comb filtering caused by the reflection, as the reflected sound level will be lower in level.
Below is a real world example measured in a studio where the monitor was positioned horizontally on the meter bridge of a large mixing desk (red line). The comb filtering on the horizontally mounted monitor starts quite clearly at 1kHz and extends nicely up to 7kHz. This is caused by the reflection from the mixing desk surface and the resulting frequency response is clearly not acceptable.
The monitor was then simply rotated through 90° and placed in the same position back on the mixing console meter bridge. Nothing else was changed and the monitor was remeasured (green line). It can be seen that frequency response is much flatter due to the change in the angle of reflected sound. The response below 200Hz is unaffected when rotating the monitor as the sound energy is omni-directional. The tolerance of this monitor's anechoic frequency response is ± 2.5dB in the passband. Everything outside this tolerance range is an effect of placing the monitor into the room!
All spaced driver monitor solutions suffer from a notch in the frequency response when listening off-axis in the plane of the drivers. Positioning the monitor horizontally causes this notch to become audible when moving from left to right along the mixing desk. Positioning the monitor vertically removes this problem.