Posted by Duke [ 208.98.184.1 ] on November 06, 2007 at 18:14:18:
In Reply to: Re: crossover posted by valveman on November 06, 2007 at 16:54:49:
Hi valveman,
Thanks for the thumbs-up!
The frequency response measurements I make include far more off-axis than on-axis measurements. Some are time-gated to eliminate room reflections, and some (taken from farther back) are not time-gated because I want to include the reflections. Some are close-miked almost touching the woofer cone and right at the mouth of the port, but those are really unnecessary for crossover design. As far as crossover design goes, I spend far more time looking at the off-axis response curves than at the on-axis curve, as in my opinion the off-axis response is telling me much more about how the speaker sounds.
I use the LMS system from LinearX for my measurements. I model the crossover using CrossoverShop, also from LinearX. Before building prototypes, I model the design using EnclosureShop from the same people. I'm not saying this is the best suite of loudspeaker design tools because I haven't really used any others that are comprehensive like this one. I've been told that there are more capable ones out there for less money, but don't remember what they are because I don't feel like buying another package. The feature LinearX has that most of the others don't is excellent customer support, and that's why I paid the extra money for this package. I also have a home-made speaker turntable, so that I can easily rotate the speaker by hand a precise number of degrees in the horizontal plane to get my off-axis measurements.
I think the guidelines I've given out here are about as specific as I want to get, far as teaching what I do goes. Some specific details I'd rather keep to myself, as that knowldege was expensive and time-consuming to acquire. I consider the crossover to be the heart and soul of my designs. That being said, pretty much everything I do is covered in the Loudspeaker Design Cookbook by Dickason - it's just that crossing over and equalizing a constant-directivity horn-loaded compression driver is sort of a worst-case scenario as far as complexity goes. In my admittedly limited experience, there are no short-cuts to doing what I want to do. The only road is the long road.
I can tell you right off the bat that Wayne's crossover design guide is an excellent starting point. What I do ends up being a more complicated network, but strip away some of my equalization circuits and the basic topology looks like what Wayne does. I think his horns don't require as much attention to equalization as my waveguides do.
Duke
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