摘取2004年某专题文章如下，特殊字体和颜色由我添加，以下言论不代表本人观点，仅供参考：
Designing Loudspeakers At Revel -
An Interview with Kevin Voecks, Director of Technology, Harman Specialty Group (Revel, Mark Levinson, Lexicon)
Sumit: You mentioned high-order crossovers a while back. Revel speakers have always used high-order crossovers. Several companies take the opposite approach i.e. they use low-order (first and second order) crossovers. What are the disadvantages of using low-order crossover designs? Are there any advantages to using low-order crossovers?
Kevin: Well, we were fortunate enough to have done research that has allowed us to know, to really understand, what are the characteristics that are important to sound quality and what are the characteristics that have some value but less, and those characteristics that don't have any sonic value and that allow us to make the optimum choices in the design. That all points very, very strongly to high-order crossovers because high-order crossovers are necessary in order to have low distortion which is way up there on the list of important sonic qualities. High-order crossovers are important to have good dynamic capability without compression. It would really shock audiophiles to see how much the response of most high-end loudspeakers changes at different volume levels. They are like completely different loudspeakers when played even at moderate levels, and it is something that is very directly measurable. So we really focus on making sure that not only is the timbre really accurate, but that it changes as little as possible over a very wide dynamic range. Plus the distortion is below the audible threshold; resonances are below the audible threshold because our research has shown those are really important things. If we used first-order crossovers, we would degrade the off-axis response, and therefore the timbre, we would completely degrade the distortion characteristics, we would loose our dynamic capability, our freedom from compression because tweeters and mid-ranges are then getting signals that are outside the frequency range that they are really designed to handle. So it's really mostly heat, and that heat makes the voice coil impedance go up, and as a result of that the filter network is mis-terminated because it's not seeing the termination impedance it expects to see, and then the response of the crossover is impacted. So what that means is that when speakers heat up, voice coils heat up, the crossover networks don't work right anymore and you get peaks and dips in the response, several dB peaks and dips in the response. So with high-order crossovers and with all the things that we are doing in the transducer design to keep the voice coils cool which means we are generally using a very large voice coils which spreads out the heat over a large area, and we're using in some cases multiple woofers to further spread out the heat. We are using all of these techniques including the way we vent them which forces the air through the gap at the same time, the vents are designed in such a way so that they don't create noises. It's a very sophisticated approach to solving the problem with heat. But a big part of that is the high-order crossovers. It's an essential part of it.
Sumit: What crossover slopes are typically employed in Revel designs?
Kevin: Our networks are always tweaked to result in the smoothest possible transition between transducers. Because of that, their electrical characteristics don't meet the textbook definition of classical filters, which is why we don't specify them in our literature. However, the resulting response of the transducer/enclosure acoustic and the filter's electrical response is close to a 4th-order (24dB/octave) Linkwitz-Riley characteristic.
Sumit: Have you ever heard a good loudspeaker that uses a low-order crossover?
Kevin: I have heard good loudspeakers that use low-order crossovers. I haven't heard great loudspeakers that use low-order crossovers. They run into these problems. It's inevitable. | 
发表于 2015-7-15 23:04
