I've recently taken to using one particular AKG D224 as reference as I've been looking at ribbon mics and testing other dynamics for which phantom power would be death and, using the software as I had been, the D224 matched up with the reference and didn't want the possibility of catastrophic muddle.
However, setting the measurement software to Frequency Response, attached is the graph of the D224 vs the reference mic, not as straight as I'd like.
I've tested today a Voigt horn and retested the TP1 London and in doing so tested the D224 against the reference. None of the bumps match up and I'm assuming that these may be caused
- by room reflection differences on account of the reference being omni and the D224 being cardioid
- possible phase or delay issues between the treble and bass capsules of the D224.
The tests today were repeated with the Voigt and the TP1 London at the speaker grill and at 1m.
The file AKG D224 38316 and reference was done with the Tannoy 611 which I've used as a reference speaker. Measurement variations could be caused on account of the two unit bass causing places of different interference and with the TP1 likewise with treble and bass horn.
The differences leave me somewhat at a loss but at least being consistent with this group of speaker measurements might give an idea at least about how the speakers behave.
This is neither the time of year nor weather nor light outside to be taking speakers out into a carpark or a wood, for which I apologise.
Best wishes
David P