Q: Let me start by saying I look forward to reading Troubleshooting every month. I have been getting CA&E since the early '90s. Why did so many companies go away from 3-way components? Are the more expensive 3-way components better for sound competition than 2-way components?
-Smoove
A: Thanks for the comments and thanks for reading CA&E for such a long time! The manufacturers will have their own position as to why they shifted away from 3-way in favor of 2-way components - I have my own view, which is based on what happens at the install bay level and how that is translated up the chain to the manufacturers and marketers.
First, from the acoustic science side of the topic: It is accepted as fact that the best speaker is a single point source speaker or emitter. You have one mouth on your face, and when you speak or sing, all frequencies involved emit from the same source. Compare that to a loudspeaker and we hit a couple of snags: A speaker cannot cover all of the audible frequencies, so we need to use a low-frequency device called a woofer and a high-frequency device called a tweeter. Sorry if this sounds a bit elemental; I know you have been reading the mag for a long time, but we also have new readers that I don't want to leave in the dust.
Put a woofer and tweeter together and you can now cover the complete musical band from 20Hz bass notes to 20,000Hz at the treble end respectably. Problem solved? Not so fast - the singer has one sound source, which takes two speakers to equal. If you place the speaker components beside each other, the brain can decode the presence of two sound emitters instead of the expected one source. They are duplicating efforts in that the woofer is playing a bit into the tweeter's range and the tweeter is trying to cover some high bass notes. This duplication of signals causes "phase errors," which is the foundation of how creatures localize the source of a sound - whether prey or predator or punk band.
So we add a circuit called a crossover, which is a filter set that blocks high frequencies from the woofer and low frequencies from the tweeter. Now the sound has become more precise but still doesn't sound exactly like it is coming from only one emitter, especially when the song transitions from a low note to a high note and the sensitive ear notices that the source of the sound has changed position slightly.
The black art of building a perfect loudspeaker is frustrating enough to drive speaker designers to go postal. The loudspeaker is like a guitar - the longer you play guitar, the more you know that it is impossible to tune and keep in tune. It can be maddening! So far, we have only covered a 2-way speaker. Now you want to go 3-way? Who needs the aggravation?
From the physical installation side, cars today are just too cramped to offer spaces suitable for speaker locations. We prefer to have two locations equally distant in path length between the speakers and the ears, forming an equilateral triangle, known as the "imaging triangle." The speakers must also be "on-axis" or perpendicular to the listener, so the speaker is firing directly at the listener. That's tough to get in cars of the last 20 years. Keep in mind that we also need to ensure the speaker elements are within one-half wavelength at the crossover point according to many, including Vance Dickason, the renowned author of the Loudspeaker Design Cookbook. That means the tweeter, midrange and woofer all must be very close together or you get all kinds of phase and timing problems.
Most installs wind up consisting of a woofer in the door and a tweeter in the dash. According to the half-wavelength rule, a woofer and tweeter should be less than an inch or two apart from center to center, depending on the crossover frequency! Where do we put the midrange? Break out the plasma cutter and fiberglass, and let's fabricate a new dash! It seems that there is little chance of getting naturally good speaker placement in a car. Even the carmaker, who has absolute control over the shape of the dash, always designs the speakers to be in bad positions.