Fullrange FR125S Monitors


Two parallel notch filters are used to address a) the broad hump centred at approxiately 1kHz, and b) the peak at 6.5kHz.

The 0.05mH inductor is made by unwinding 215cm from a 19ga 0.1mH air core inductor (from Madisound).

Above is the frequency response with and without the notch filters and off axis response of the speaker.

The full frequency response, measured on-axis smoothed 1/3 octave.


The bass response of this speaker is impressive for a small fullrange driver. The FR125S has large xmax for a driver of its type and the XBL2 motor allows for a very dynamic bass response up to the point where you hit mechanical excursion limits (and then it's not pretty).

The midrange response is smooth and behaves well until it hits 6kHz where is begins a peak-dip-peak which is partially addressed with one of the notch filters. My hearing is limited to about 17kHz according to the test tones played during measurements (I'm 29) so the upper peak is not too much of a concern, especially considering these will almost always be listened to off-axis rather than for critical listening.

The 1kHz notch smoothes out the large hump and further baffle step compensation is not required as the measurements show a flat response down to the -3db point at ~45Hz.

These speakers are impressive performers at the bottom end and smooth and articulate in the middle. They have a tougher time at the upper end, highlighted somewhat by a dip sitting in between two peaks. There is an active circuit suggested here which can be used to raise the response dip making the peaks much less dramatic.

Overall I favour these over the W3-871S design by some margin, and they will be an excellent upgrade in my non-critical listening environments - but then again I'll pull out the big guns for that!

Cabinet Finish

Copyright © 2006 Vikash Chauhan. All rights reserved.