Loudspeaker Designs and Articles for the DIY Enthusiast
The Crossover is a simple first order series crossover, crossing at about 400Hz, and a small shelving network on the Alpair to properly voice it and provide
additional treble in the top octaves. The crossover frequency chosen had two advantages: It off loaded much of the Alpair’s excursion duties onto the SB
woofers. It also fell more or less midrange in the baffle step. Due to the increased sensitivity of the woofers and the slow roll off of the first order crossover,
the baffle step compensation is essentially compensated for without additional manipulation of the crossover components.
Tips and tricks:
Interestingly enough, I found this design is quite sensitive to crossover components.
While the capacitor across the woofer is a large value, I cannot recommend using non-polarized electrolytics in this position. –That is, unless you like the
sound of a speaker covered by a blanket. I actually used good quality NPE’s to flesh out the prototype crossover. The sound was OK, but it was
disappointed in the Alpair performance. When I determined the final value for that cap, I replaced the NPE’s with Clarity PX caps. There was simply no
comparison to the sound quality with the Clarity caps. I did not try other brands of poly caps, so it will be up to you to experiment with them. Since 150uF
caps are difficult to come by anyway, I suggest you make up a ‘cap pack’ of multiple values that add up to the desired value. Three 50uF caps work fine. I
actually used two 50’s, two 20’s, and a 10uF in the design.
-More because I was fine tuning although the combined ECR will be less with multiple caps. Buy what brand and quantity you choose, but don’t skimp on
Another revelation on the sound quality of the Alpair had to do with the resistor type. My initial testing was with wirewound resistors, but after values had
been chosen, I replaced them with a quality thick film MOX resistor. The resultant sound quality was not subtle, nor pretty. Your basic low cost, high value
wirewound resistors went back in and the quality sound returned. At these resistor values all wirewound resistors can be considered non-inductive, so you
can save a few bucks here and spend them on the caps.
The inductor should be a low DCR type. I used a steel laminate cored inductor.
A FULL RANGE PROJECT
WITH BASS ASSIST AND
The components to build the Halcyons are available as a kit with special pricing.
Click as a link on the Madisound logo below for more information.