Measurement Conditions
To get consistent and realistic results you need the panel to be suspended in air, on a repeatable stable position and angle and with no reflecting objects nearby. The image below shows the simple but effective measurement jig that I put together from an old IKEA CD stand. With a little modification it was just perfect for treble panel measurements.The panel is fixed on the exact same height with the center of the panel 1 meter above the floor. The proper felt lining is attached between the two poles of the stand.
Normal frequency response measurements are all performed with the microphone lined up on an exact straight angle with the surface of the panel, aligned with the center and at a distance of 2 meters. There are no reflecting surfaces near the panel or microphone except for the floor and ceiling.
Measurements are performed with a Behringer ECM8000 microphone, a Lynx L22 soundcard and a PC running the software package ARTA, doing MLS (Maximum Length Sequence) gated measurements. For treble panel measurements the gate is set such to exclude reflections.
Treble panel measurement jig.