@TechToys2
@TechToys2 – This is a follow-up to your answer to a question from
@mazersteven , about what speakers are you running – B&W CDM-1NT speakers.
In speakers where the mid-range sometimes (depending on the music) sounds too forward or even harsh, a major cause is a natural bump in the woofer's response in the upper mid-range (roughly 3-6 kHz). It's caused by a resonance coming from where the cone meets the surround. This bump in the frequency response curve is not just a louder response, but noise that you really don’t want to hear. It’s often called woofer break-up noise. This resonance, found in all coned speakers, a result of the whole mechanical system formed by the cone, surround, and suspension, varies significantly with the speaker cone material.
Most woofers have at least a little of this, but some have quite a bit. Paper coned drivers suffer much less than speakers with stiffer cone material, such as metal or woven glass or Kevlar fibers. That’s the ugly secret of most mid woofers, and, a large reason why good crossover design is so important. Again, this can result in accentuated detail, but also produces an irritating edge to the sound that leads to listener’s fatigue. Speakers that at first listen seem to add detail over and above what is in the recording generally suffer from this kind of upper mid-range peak. Not surprisingly, many people mistakenly believe this fatiguing sound comes from the tweeter and not the woofer.
B&W, in particular, has hitched its wagon to those highly visible yellow mid woofers. I can't tell you what the engineers and marketing people were thinking, but it seems to me that they wanted their speakers to sound as identifiable as they look. So they moved the crossover point high enough, 4 kHz, to include the range where the Kevlar driver was beginning to go into break up. That did succeed in making it sound different, but it also led to listener's fatigue. Eventually B&W lowered the crossover frequency some, to 3.5 kHz, the problem was diminished, but still remained. If the crossover frequency was lower, such as 2 kHz, it wouldn't have the fatiguing noise, but it would also lack that identifiable Kevlar sound.
Over the years, there have been too many different B&W model versions for me to be able to clearly say which ones do and don't suffer from this problem. Several 600 series speakers I've heard in the past have all suffered from it. The few CM series speakers I've heard also have the problem, but a bit less. The trouble is, once I learned to hear the problem, it was hard to "unhear" it. And many of those 800 series speakers I heard all sounded rather good.
From my own viewpoint, I would never want a speaker with a Kevlar mid-woofer combined with a high frequency crossover point. However, it does seem like the engineers found ways to silence that ugly break up noise, but only in the very expensive 800 series speakers. For me, they cost much more than I would want to pay. It is interesting that the most recent B&W models have what looks like a completely new mid-woofer. It isn't yellow and it doesn't look like it's made from any woven fibers.
