94.214.97.240
In Reply to: RE: So, what's the down side, if any? nt posted by stickler to perfection on July 04, 2009 at 06:59:43
Hi David,
I had seen the Sanders video before. I must say my alarm bells immediately start ringing when I see someone single out one aspect of speaker design and put's that much emphasis on it. Especially when it is accompanied by pseudo science (which by my definition is the presentation of claims as facts without the supporting evidence, nor any pointers to previously scientific work to support the claims). It almost always is a sales pitch and nothing new under the sun. What amazes me even further is that there are no polar plots to be found on Sanders website. So he talks a lot about directivity, but does not show the measurements for his own speakers. Sorry if I sound so harsh towards Sanders, but this is the way I see it.
I could go into the claims that he makes in the video one by one, but I chose not to do so mostly because this forum is not a technical forum and probably 99% of the readers would be bored to death. Note that I do not necessarily disagree with his point of view, but I do disagree with the way he presents and over emphasises it.
Directivity is nothing new. Let me quote a piece written by Baxandall on this subject from circa 1988. Baxandall is a true genius when it comes to electrostatic loudspeaker theory, acoustics and electronics.
"Taking all aspects into account, it is evident that some loudspeaker directivity is always desirable, but that the nature of this directivity needs to be rather carefully controlled, both for good stereo imaging, and to avoid an unpleasant or unnatural quality in the overall sound received by listeners.
The directivity of a loudspeaker at very low frequencies cannot in practice be made very great, for any totally enclosed cabinet design has substantially zero low-frequency directivity, and a doublet design has a theoretical directivity index of 4.8dB. At higher frequencies, more directivity is desirable, so that the directivity must in practice be allowed to increase with rising frequency, but it is m,ost important that this increase should be achieved in a smooth and continuous manner. It is also important that the off-axis frequency responses which accompany this increase in directivity should not have exaggerated and unnatural features, such as pronounced peaks or dips, nor be if a shelving or step-like form (ref 13 = D.E.L. Shorter, 'A survey of performance criteria and design considerations for high quality monitoring loudspeakers' - Nov 1958)
Gently falling high-frequency responses are frequently met in natural circumstances, for example when listening to sounds that have travelled round corners (ref 13) so it is hardly surprising to find that the off-axis sound from loudspeakers should be arranged to have this kind of characteristic of the overall results is to be interpreted as natural sounding.
Not only should the directivity increase smoothly and continuously with frequency above a certain frequency, but also the magnitude of the increase should be appropriately optimized - sufficient to give good stereo conditions, but not so great that listening positions become unduly critical. If any large increase in directivity is allowed to occur by 1000 Hz, the reverberant sound will appear to be bass-heavy and dull, and yet, for good stereo, some directivity at 1000 Hz is desirable. In this respect a doublet system has a real advantage, for directivity at 10000 Hz is then obtainable without having to suffer a variation in directivity below this frequency."
Note that Baxandall is discussing directivity in the light of electrostatic speakers, which by nature have an increasing directivity with frequency, but one that is far too much when no measures have been taken to prevent this. The original Quad ESL also has a number of mechanisms in place to control directivity.
Let me finish with another quote from Baxandall:
"No single recipe can be confidently stated to be universally right, partly because personal preferences are inherently involved, but also because the optimum directional characteristcs are very considerably influenced by the acoustics of the room in which the loudspeakers will be used (ref 35, P.J. Walker, 'The sound of the room', August 1991)"
Follow Ups:
Post a Followup:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2009, Audio Asylum, all rights reserved ]
[ Go Green ]
[ Take5 ]