New crossovers for HECO Aurora 300 – small bookshelf 2-way speaker systems.
In terms of sound, the Aurora 300 is a typical representative of inexpensive speakers with a characteristic saddle-shaped frequency response: the midrange frequencies are recessed relative to the low and high frequencies.
FR before upgrade 
off axis FR 
transferred functions of filters 
impedance
As we can see from the measurements of the frequency response and filter transfer functions, the developer of these speakers consciously and intentionally “dumped” the midrange frequencies by 6 dB, that is, 2 times in the crossover settings. Nothing surprising – a typical story among many speaker system developers. I partially tried to reveal the “secret” of the saddle-shaped frequency response phenomenon in the article FINE-TUNING OF SPEAKER SYSTEMS
Standard crossovers have a simple circuit and are mounted on a terminal block, so due to the limitations of the available dimensions of the block itself, miniature inductors on iron cores and non-polar electrolytic capacitors are used.
I offer new crossovers also of simple design, but taking into account a uniform frequency response along the speaker axis and smoother off-axis declines:
FR with new crossovers 
off-axis FR 
transfer functions of filters 
impedance 
assembly and schematic diagrams
In terms of tonal balance, the sound is neutral, expressive, and objectively the frequency response is almost perfectly even. Subjectively, the sound quality is limited by the not very high resolution of the HECO drivers.
new crossovers 
inside installation
I divided the boards of the new crossovers into low-pass and high-pass filters, since the dimensions of the standard crossover slot did not allow for one full-fledged board. Therefore, only half of the crossover, namely the high-pass filter, is placed on the terminal block, and the other half – the low-pass filter – is placed on the bottom of the box. The possibility of separate Bi-wiring or Bi-amping connection is retained.
