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08/09/2015

The first day, we did an on-axis SPL measurement of both speakers. 1 m microphone distance, 90 cm microphone height (center of the tweeter). There goes the answer for the chaotic sound.



Since the mid-bass region was particularly bad, we did an SPL measurement of all four FS41RP planars with the microphone in 5 cm distance from each of the drivers. Something is clearly off.



We also took the impulse response of the right speaker. The reason for the inverted RCA vs. XLR input polarity can be found on this diagram.

17/09/2015

Some days later, we measured the impedance of all magnetostatic drivers in free air.



Here is the detail of the mismatching impedance readings of the FS41RP planars. Not that this should cause the havoc in their SPL measurement. Actually, you can see that Fischer Audio attempted to pair similar drivers into each speaker.



Woofers impedance in free air. We might have to redo this as we probably caught some reflections there. It should be smoother but at least they are all the same.



This is the impedance measurements from the datasheet of this woofer. You can see it is substatially different.

01/10/2015

Today, we measured the frequency response of the four FS41RP mid-bass planars in near field (10 cm). They were put back in their enclosures with new damping and with no crossover before them (actually we measured them all in one enclosure - the top left one - so as to eliminate any differences coming from different enclosures and/or damping). They were hooked directly to a 3rd party amplifier (because all the electronics are now in service). Unfortunately, there is quite some variance between the drivers, as can also be seen on the initial measurements at the top of this page. This won't go away. I would very much appreciate if anyone could share their own, separate measurement of these drivers. I might even buy another pair to try to match it closer to one of my two pairs.



The same drivers but in far field (100 cm). Compare this with the datasheet.



The same measurement but this time for the FS21RP midranges. Compare it with the wonderful set of measurements done by Hifi-Selbstbau.de.

We have measured the impedance of all midbass and midrange planars in newly-dampened enclosures. The damping material used is going to be BASF Basotect in place of the old foam triangles and Monacor MDM-2 in place of the old mineral wool. Compare this with the free-air measurement of the same drivers. This particular measurement was taken in the top-left enclosure for all midbass drivers and left enclosure for both midrange drivers so as to keep the damping exactly the same. I will redo this for each driver in their own enclosures when I am re-installing them back to the boxes for real.



We also measured distortion of each midbass and midrange. This is the top-left midbass:



Bottom-left midbass:



Top-right midbass:



Bottom-right midbass:



Left midrange:



Right midrange: