msc@alessia.dei.unipd.it (Matteo Santinato 228156) (06/26/91)
Hi. I have been speaking with a friend of mine (Francesco) about the design of the crossover networks for the Mirage M1 and M3 loudspeakers. As you know, the dispersion of sound is a function of frequency: Low frequencies are omnidirectional, while high frequencies are very directional. I assume that the low frequency response of the M1 crossover unit is the same for both the front and rear woofers and that the response of both woofers is added in the room. On the contrary, the tweeter response is not added because it is directional. In order to have a flat frequency response from the system, assuming the same sensitivity from all of the drivers, I must provide more drive to the tweeter than to the woofer. Am I right? What is the best design for a midrange crossover unit? Any advice is appreciated. Thank you. Matteo Santinato msc@alessia.dei.unipd.it
kasha@twolf.ce.YALE.EDU (Dan B. Kasha) (06/27/91)
I wish to answer the first part of your question. You say low frequencies are dispersive. Not true. As you know, Radio Frequencies can be beamed to sattlites by antenna arrays. I remeber a trick question in a physics of music class. "What is larger, a woofer or a tweeter?" The trick was that they ment larger compared to the wavelength, which is the naswer to your question. A woofer diam. is about a foot. And at 20 hz, the wavelength is many feet (look at a low organ pipe). And the woofer diameter is very small compared to wavelength. At 1KHz, the wavelength is about a foot. When the wavelength is large compared to the source, the sound is omni directional. When the wavelength is cmparable or smaller than the source, the sound is directional. This is why I hate 2 way speakers. The woofer must go to a couple of KHz, and if it is large enough to have guts, it has no dispersion. I do not sit in an ideal spot, and I like a reflective sound, so I like when the 1KHz stuff bounces off the walls. At 20Khz, the wavelength is about 1/2 inch. The tweeter beems then as well, but there is little to do about that. I like multi tweeter/mid speakers that shoot sound all over. I do not buy the interference stuff, and have heard such speakers DUST the best- B&W, Magnapan's, Duntec, though the speaker is a bear to work with. The Cello speaker - based on the 1968 AR LST!