[Sasha]

From what I understand, FB1 had 3kHz crossover point and 2nd order crossover.
With FB1+, a new tweeter was introduced and crossover point was moved to 2kHz.
Does anyone know if the slope remained the same, or it is now 4rd order?
From what I have read, the new tweeter is not the best one out there (better then the old one, but still not capable of going to extreme lows), so I was wondering if the new tweeter is forced to run too low, and consequenty produces larger amount of distortions?
Is it possible that PMC had made modifications to achive better off-axis response at the expense of tweeter distortions?
I would think so, if crossover remained 2nd order, tweeter would be forced to work at too low frequences?

[James Tanner]

From what I understand, FB1 had 3kHz crossover point and 2nd order crossover.
With FB1+, a new tweeter was introduced and crossover point was moved to 2kHz.
Does anyone know if the slope remained the same, or it is now 4rd order?
From what I have read, the new tweeter is not the best one out there (better then the old one, but still not capable of going to extreme lows), so I was wondering if the new tweeter is forced to run too low, and consequenty produces larger amount of distortions?
Is it possible  ...

Dear Sasha,

Thanks you for email regarding the FB1+ upgrade.

The crossover slope is still 12dB per Octave.

The new tweeter uses a chamber behind the dome to allow a low 650 Hz resonant
frequency more than an octave lower than the new crossover frequency. This lower
crossover point improves the dispersion significantly as you suggest however
distortion is reduced as the maximum output of this tweeter is higher than the original
aluminium dome.

I hope that explains our design philosophy in the FB1+ and hope that you have the
chance to hear the benefits of this improved design.

Kindest Regards

Peter Thomas