One thing I have been wondering about...how much has speaker technology advanced since the eary 80's? In those days, the consumer level speakers I remember we all coveted in high school had huge woofers. That seems to have gone by the wayside. Is that because driver technology is so much better, or they had the physics wrong back then, or it's just a cost thing, or what?
Its not so much new speaker technology but more like marketing and fashion trends that have caused 6" and smaller woofers to predominate now. People buying multiple speakers for 5 or 7 channel home theaters seem to want smaller and less costly speakers. The existence of powered subwoofers can cover the bass that these smaller speakers cannot do. And, most people spend more money on new TV technology than on speakers or sound systems in general.
This trend has been accompanied by the industry's efforts to improve 6" and smaller woofers. So there has been incremental improvement of these drivers. In general, they perform better and produce better bass that such sizes could in the 70s and 80s. Most of these drivers have been built to perform best in small ported cabinets, again because size is on the public's mind. It is less common to see speakers with sealed cabinets, because these designs usually need larger cabinets or produce less volume.
There are some real advantages to 2-way speakers with 6" and smaller woofers. It is easier to design a crossover to a 1" tweeter that has level response across the midrange, than with 8" or larger woofers. I doubt if any of the more popular 2-way speakers from 70s or 80s had good midrange performance – they probably had a big response hole in the middle of their crossover range.
Also, I noticed lines like polk will sometimes upgrade within a line by just adding an additional identical driver or two. What does this accomplish? When will more drivers start to degrade the sound, if ever? For some reason I thought a lot of drivers close together would distort the sound waves?? lol
Two woofers will move twice as much air as one. This won't produce deeper bass, but it does produce louder bass. Two woofers in a vertical line with each other, as in typical MMT or MTM designs, can create zones where sound is lost due to interference (not distortion) with the waves from each woofer, but this is only noticed if the listener sits above or below the plane of the two woofers. In fact, because each driver has to work less hard, there can be less distortion rather than more. There are also advantages because smaller woofers have less mass than larger woofers. They can start and stop responding to transient bass signals faster.
For more than 2 woofers, there are increasing problems with interference, but if the crossover point is low enough, this is not a serious problem. It's not a simple matter of throwing in another woofer in a larger cabinet, it requires more care by the designer to avoid the problems introduced by these types of designs.
