A hundred people are all probably responding at this one. The order refers to the rate of rolloff in db above or below the xover freq. (i.e. high-pass, low-pass filters, all-pass (a combination of the first two)), since a speaker w/ a 3000hz xover the drivers just don't stop like a brick wall and change hands above or below that frequency. There's a portion of sound shared by the drivers and each "fades" into the next. 1st order rolls of at 6db an octave beyond the xover point; 2nd order=12db an octave rolloff; 3rd order=18db etc. Most don't go beyond 4th order. The highest I've seen is Joseph Audio's 120db octave: that's a 20th order. Obviously the 1st order is one in which the driver's will share the largest region of overlap. These have a cult like following (Thiel and Vienna acoustics do them). Only problem is the driver has to be able to play well beyond the crossover freq. w/ these types and so alot of drivers aren't suited for 1st order. Beyond the rate of rolloff (6db for each step up in order) is the phase relationships. Some orders change phase relationships between the drivers. I'll bail here because I'll probably mess it up. I've read several books, but none that I thought explained it very well. But no one xover type is really superior to another, in large part it depends on the driver's being used and the system itself. In a three way with a midrange in a sealed enclosure there's a mechanical rolloff only half that off a bass reflex design. So the designer would take that into account in his crossover choice to achieve a specified total rolloff into the LF driver. The sum of the mechanical rolloff and electrical rolloff is often referred to as the system alignment. 7th order would correspond to 54db an octave rolloff (a bit obscure). Which basically mean an octave above the crossover freq. the drivers output would be down 54db, fairly steep. An octave is just a doubling of the frequency. So at 3,000hz-an octave above would be 6000hz.
6 responses Add your response