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The Dayton 120CX-8 is a 4″ coaxial with a 3/4″ silk dome tweeter. This is the first time I’m working on a small HiFi coaxial. If she meets my expectations, she would make an ideal candidate to mate with a woofer. Basically, I’m looking at a hybrid 3-way. The CX120 will be the mid/high unit with a passive crossover and the woofer is active. Crossover frequency is about 125Hz~250Hz (24/db/oct). Manufacturer’s Specs I’m surprised that the CX120 tweeter’s Fs is at 4178Hz. This is significantly higher than Dayton’s specs of 2745Hz. Usually for a 3/4″ silk dome tweeter, I would cross at 3,500Hz. It remains to be seen whether I’ll be able to do this. Dayton CX120-8 Woofer Thiele & Small Parameters (DATS) The woofer fared much better. My DATS measurements are close to the manufacturers’. Qts is 0.499 and Fs is 90.8 Hz. Vas is 3 liters. All these indicate a small closed box, exactly what I’m looking for. I am no fan of trying to get bass out of a 4″ but nonetheless, I simulated the CX120 in a bass reflex for completeness. Sealed Box=3 liters | F3=130Hz | Q=0.67 It seems the optimal loading for the CX120 is a 3 liters sealed box. F3 is 130Hz. This would be about right for me to cross to a woofer at 125Hz~250Hz. Sealed Box=7 liters | F3=133Hz | Q=0.58 7 liters would offer more space to install a crossover. F3 is only slightly higher at 133Hz. Crossover slope is more towards a Bessel alignment. Ported Box=7 liters | Fb=65Hz | Q=0.58 With the same 7 liters box but this time ported, the bass is lower at 57Hz (-3dB). One ought to be careful with the loudness of the bass when the CX120 is in a bass reflex because the Xmax is only 3mm. Too much and the CX120 will distort. Ported Box=5 liters | Fb=72Hz | Q=0.60
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June 14, 2023Drivers Thiele & Small, HIFI DRIVERS
