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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: But this seems to be posted by RGA on July 24, 2002 at 15:21:25:
Actually I don't find B&W speakers particularly bright. The company seems to voice for a hot or peaky on-axis balance in the high treble to compensate for the lack of wide-dispersion in this passband. If you sit just a little off axis of a B&W tweeter you get a fairly dry (ruler-flat) result. Unfortunately though, the treble seems too dry and as you move off-axis, high treble response falls off quickly. This puts less power into the room at the very highest frequencies resulting in a lack of air and high frequency "wetness." Whether or not this is noticeable, depends on how much of your high frequency hearing you still retain. Some manufacturers use additional "ambience" tweeters to compensate for lack of high frequency dispersion (but not B&W).What I think is more audible and objectionable are the power flares that occur in the lower treble. Specifically, these metal domes show wide dispersion in the bottom of their passband, which drops off steadily with higher frequency. You might see 180 degree dispersion in the 4-8 kHz passband, which narrows to 90 degree dispersion at 10 kHz and narrows to less than 20 degree dispersion at 15 kHz and so on. Consider that the kevlar cone produces 90 degree dispersion at 1 kHz and very rapid changes of dispersion through the actual crossover, you end up with some pretty drastic changes of dispersion through the upper mid/lower treble. This will not load the room evenly, resulting in too much energy in the lower treble passband and too little above. The human ear is ten times more sensitive to lower treble frequencies than to high treble frequencies. This uneven power response will irritate.
Yet, I don't have a problem as much with the quantity of the treble produced by these metal domes as its quality. The domes need better damping. I am sure loading the dome with a column of air (the Nautilus transmission line) is helping to lower the resonant behavior of these domes, but I still hear a residual chromium plated edge in the lower treble (which coincides with the domes peak power). The domes are ringing ever so slightly at the bottom of their passband around 4 kHz (visible in time domain graphs). The domes need to be damped better. Perhaps they need to be lighter to resist ringing better. It can be done. Focal have succeeded in producing high quality metal domes that resist this low treble ringing (probably by careful use of damping compounds applied to the dome), resulting in a less fatiguing low treble sound.
Getting back to the kevlar cones…they seem to be fine up to around 1-2 kHz…then they go into break-up. B&W run them all the way up to 3 or 4 kHz, but the cones are not behaving in a linear fashion in this crucial passband. This is far, far more audible than any problem occurring in the treble (due to the extreme sensitivity of human hearing at these frequencies – the nails on a chalk board passband). As a result (depending on your listening angle) violins can screech unnaturally or sound unnaturally dull. The lack of linearity in the presence passband creates colorations of the human voice…the pinched or nasal coloration that we are somewhat used to from loudspeakers. Presence band instruments like trumpets and trombones can sound very synthetic and unconvincing due to power anomalies in this passband (even though technically the speakers might measure flat on-axis). The results…the sound…speaks for itself.
A speaker designer absolutely MUST get the upper crossover right for the speaker to sound coherent. Otherwise the music will separate into treble and mid-range. It's a delicate balancing act. Ideally you DO NOT want to stick a crossover between 2-4 kHz, but if you MUST…you will need to spend all your time and effort getting the drivers to work together in phase over a useful range of vertical and horizontal angles. B&W solved this problem (and many others) in the original Nautilus by dividing the audible spectrum into four bands (using four drivers); all of which behaved as true pistons in their operational passbands (no in-band break-up modes a la kevlar). If I were designing "Nautilus" speakers, they would follow the original design much more closely.
As you can see, the designer in me causes me to think, "how could I improve the sound of these speakers?" Before starting, I would need to identify those areas that needed help. If I listen to a loudspeaker long enough, I am usually ready to re-engineer it. I often think, "if I could combine that speaker's treble, with this speaker's mid-range, with that speaker's bass…and avoid crossover irregularities, I'd have a really good product." It can be done; especially when you don't have to design by committee or design based on what sells or the latest trend. In my world-view, speakers need to be accurate…period.
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Follow Ups
- Quantity vs. Quality - layman 18:42:17 07/24/02 (2)
- Re: Quantity vs. Quality - musicluver 20:44:15 07/24/02 (1)
- Re: Quantity vs. Quality - layman 22:25:57 07/24/02 (0)
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