Passive, active, and dispersion

To Doug Schneider,

I read your response to my letter and found it enjoyable. I would add, however, that particular dispersion issues also arise with the use of passive crossovers. The classic midrange suckout is so pronounced that many have come to consider this to be the correct presentation. I suspect that the guys at ATC Loudspeakers could wax poetic on this point.

I am actually running an active system using the 6” driver’s natural roll-off as the high-pass. The subwoofer has its own adjustable crossover and is built into same floorstanding cabinet as the 6” driver. This allows me to use an 845 tube amp with the 6” driver and run the sub off the binding posts, so as not to introduce a completely different character in the lower frequencies. Perhaps you could give these Omegas a listen, but they may only be built to order.

Unfortunately, there aren't many choices that are not geared to nearfield listening.


Dispersion issues have nothing to do with whether a speaker is passive or active. Neither does a midrange suckout. If a speaker has a big suckout, that’s just bad crossover design, passive or active.

What primarily affects dispersion is the driver design, particularly the size of it, in conjunction with the crossover implementation. A full explanation of this would get far too long, but what’s important to understand is that a conventional driver will radiate nicely to the front and sides providing the wavelengths its reproducing are larger than its diameter. Once the wavelengths become smaller than the driver's diameter, the driver essentially starts interfering with itself (basically, cancellations) and dispersion narrows. That's why a 6" driver will have better dispersion at higher frequencies than a 10" one, and a 3" driver will have better dispersion at even higher frequencies than a 6" one. Many people call this narrowing of dispersion “beaming,” and the same thing will happen whether the speaker's crossover is passive or active. . . . Doug Schneider