@amirm very interesting. Different from the Purifi SPK4 Demo Kit I reviewed a while back. Here are some REW measurements at 30cm in my room with no gating and REW's default 500ms window:
That's 1/24 octave smoothing. Excellent response down to 32 Hz with low (relative) distortion compared to other speakers I have measured. Take the distortion measurements with a grain of salt as I don't know the distortion of the measurement mic I used, nor the mic preamp and I forget what SPL level I used (i suspect 83 dB SPL). But good enough to get a characteristic and to compare, relatively speaking, to the KEF LS50 in comparison (same conditions):
Note that the LS50 is down by 20 dB SPL at 33 Hz as compared to the Purifi.
The LS50's overall distortion, relatively speaking, higher than the Purifi's overall and especially at 33 Hz.
While I am not a fan of the AMT21CM2.1, it had a similar sonic profile to the LS50's except the bass response went down to 32 Hz, with a port tuning of 35 Hz (I think they may have lowered it to 32 Hz on my box, but I would have to dig through my correspondence with Purifi). The XO was at 2.5 kHz. The bass response was amazingly loud and clear - smoked the LS50. It also did a pretty dang good job of pressuring my room. So much so, I gathered the family in to listen. Everyone very surprised to feel the bass from such a small speaker.
I wonder what happened with this SPK5 pair?
PS. Here is a link to the
SPK4 Demo Kit application note and a link to my review of
Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review.