2-way with wide dispersion and low distortion. Linear CTA-2034. Mechano26

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Another take on a small two-way monitor design. 

While searching through various datasheets, I came across a driver setup that seemed to allow for directivity matching between the tweeter and woofer without using a waveguide. This would allow for both good control of the CTA-2034's characteristics and wide dispersion.

Drivers used:

SB15MFC35-4

SB26CDC-C000-4

18 mm birch plywood enclosure, dimensions: 314 x 184  188 x 278 mm HxWxD.

I took a complete set of measurements in both the horizontal and vertical planes. The driver choice turned out to be valuable; indeed, it was possible to design a crossover with good control of directivity and related characteristics. It's worth to note that the DI, even in the highest octave, doesn't even exceed 9 dB.


I built prototypes according to the design. There was a small problem however: the  measurements taken on the built speaker didn't quite match the simulations. A quick check of the connections revealed nothing. But it turned out that the characteristics could be restored by modifying some of the crossover component values. And that's where I left it for now, although the issue hasn't been fully resolved: introducing modified values ​​into the simulation again resulted in some discrepancies. But the measurements are now quite correct:


NF measurements and merging port with cone response


Comparision of simulated (yellow) and NF-measured response (red). Shifted to overlap at 100Hz where the filter response is 0dB 




Possible reason for the discrepancy: the driver parameters given in the specification differ from those of the units used, e.g. the free air resonance seems to be around 56 Hz compared to 35 Hz given in the specification.



I had some scraps from 45-degree cuts. I glued them together and used them to brace the enclosure from the inside (there is one more slat in the middle which was not installed when the shot was taken).


This bracing is an improvisation ispired by a solutions used on some popular bookshelf models. 
By chance it turned out to be quite effective, the enclosure resonance problem is hardly noticable (comparing to for example Mechano23)


THD distortion:


Measurements were taken at 1m on axis. The graphs are normalized to SPL. At 86 dB, midrange distortion reaches a maximum of -49 dB relative to SPL, which translates to a percentage value of 0.35%. As the signal level increases to 96 dB, distortion locally reaches -41 dB, or 0.9%, still quite ok.


Filters (component values ​​after the modifications)




Preference rating



Polar maps


Front panel


























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