Re: the Buchardt S400, note that the frequency response spec specifies +/- 3dB "in room". So this measurement was probably taken with the speakers close to the front wall in a room of their choice. If you look at the anechoic response curve, 33 Hz is more like the -10 dB point.
I have a pair of the S400s on order, and will try to remember to post my in-room measurements when I get them.
I have a pair of the S400s on order, and will try to remember to post my in-room measurements when I get them.