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Thread: Controlled directivity speakers

  1. #31
    Thanks Bjorn, keep us posted as your impressions of the CBTs develop.

  2. #32
    Quote Originally Posted by rblnr
    The goal is to greatly reduce or eliminate the first reflections from the side walls and floor and ceiling. The reflections that do hit your ear are later in time and blur the sound less
    To the best of my knowledge there is no evidence that first reflections are a problem as a matter of principle, i.e. in each and ever case, regardless of circumstances. When Richard Heyser invented his method of Time Delay Spectrometry in the late 1960’s it was possible for the first time to “visualize” boundary reflections in room response curves. Without ever having done psychoacoustic research to see what human perception “thought” of these reflections, the reflections were declared undesired, disturbing, hence the “need” to eliminate them. What people tend to forget is that the fact that reflections are audible not necessarily means that they are disturbing. I had a good look at the relevant literature and there is simply no research where a 2-channel stereo system reproducing music in a typical domestic setting has been used.

    As far as speaker directivity is concerned, the direct sound is the first to arrive at the listener’s ears, and is the reference with which all sounds coming later are compared. The precedence effect works well within its time window provided the spectra of direct sound and first reflections are no too different. Floyd Toole has further found that listeners prefer speakers with response that is flat on-axis and smooth off-axis.

    Hence there is a need for controlled directivity, which does not mean that its purpose should be to reduce or eliminate first reflections. When looking at speaker measurements many speakers perform rather poorly in this respect, but they also perform rather poorly when looking at on-axis response.

    I’m with Bjorn when he says

    The question one might ask though is: Does one have to audition speakers at all or is it enough or even better to buy speakers based on measurements? I would say the latter is sufficient and also better.

    Like Earl Geddes said in a recent interview: “Personal preferences have such a low stability as to be an almost completely pointless thing to stake a claim to. “Hi-Fi” does not mean “pleasant” — it means “accurate”; accuracy, as opposed to preference, is absolutely quantifiable and extremely stable – as stable as I care to control in my lab from day to day or test to test (but in any case its uncertainty is easy to quantify and understand). Decisions based on accuracy are therefore much more likely to be valid than decisions based on “how it sounds.” I do not see how one could ever support a position that “preference” trumps “accuracy.” That’s simply taking a giant step backwards in the evolution of Hi-Fi.”


    I for one did buy my speakers based on measurements alone, taking Toole’s results as guide and also looking for the most accurate ones.

    Klaus

  3. #33
    Klaus
    And those speakers were Klein & HummeL 0500C according to your profile yes?

  4. #34
    Quote Originally Posted by iansr View Post
    Klaus
    And those speakers were Klein & HummeL 0500C according to your profile yes?
    Yes, indeed. While shopping I took a subscription to Stereophile. I also contacted manufacturers asking for measurements and all I got was audiophile gobbledygook.

    Klaus

  5. #35
    Looks like they cost $20k new? They look rather like a 3 way version of the Geddes Abbey (albeit active, DSP etc). Out of interest have you heard the Abbeys?

  6. #36
    Quote Originally Posted by iansr View Post
    Looks like they cost $20k new? They look rather like a 3 way version of the Geddes Abbey (albeit active, DSP etc). Out of interest have you heard the Abbeys?
    The K+Hs were designed around the year 2000, when did Geddes launch his Abbeys? Now they are discontinued, $20k was roughly the price when they were still available. I bought them back in 2001, and no, I did not hear the Abbeys.

    Klaus

  7. #37
    The fact that you have had them for more than a decade clearly says something about how happy you are with them. Care to comment? Shame about the looks though. Do you have grills on yours? ( looks like it was an option).

  8. #38
    Quote Originally Posted by iansr View Post
    The fact that you have had them for more than a decade clearly says something about how happy you are with them. Care to comment? Shame about the looks though. Do you have grills on yours? ( looks like it was an option).
    With small kids and a cleaning lady the optional grills were an absolute must, and I’ve got the first pair they’ve manufactured.

    The overall sound is neutral, very clear and very clean even at highest levels, no sign of strain, effortless performance. Bass is very deep, powerful and clean, even at low levels. One can listen at highest levels without feeling the desire to lower the volume, on the contrary, adding some more dB is no problem at all.

    The FIR-filters : The speakers come with 3 factory settings: all ways linear phase, all ways minimum phase, mixed. The differences are audible but subtle, the LLL provides somewhat tighter and better controlled bass. Since LLL (zero group delay, zero phase shift) is the correct way, I’m using that setting.

    Hifi is about accuracy, accuracy can be judged upon by measurements, these are the most accurate speakers I could find back in 2001 and I think they still are. For me the journey has come to an end. As for the looks, waveguides by definition are form-follows-function. I also asked my wife for approval before buying.

    Klaus

  9. #39
    [Industry Expert]/Member Sponsor Senior Member Duke LeJeune's Avatar
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    Quote Originally Posted by KlausR. View Post
    To the best of my knowledge there is no evidence that first reflections are a problem as a matter of principle, i.e. in each and ever case, regardless of circumstances.
    You're probably familiar with all of this Klaus, but I wanted to go off on a tangent here:

    Some of the circumstances that can influence whether an early reflection is beneficial or detrimental (or some combination thereof) include its direction, time delay, intensity, spectral content, and whether it is diffuse or specular.

    Let's look at direction. If the reflection comes from the exact same direction as the original sound, it is primarily interpreted by the ear/brain system as coloration. Move that same reflection around to the side, and it is primarily interpreted as enriching the timbre and adding a sense of ambience. Move it over to the opposite side, so that it arrives at the opposite ear from the first-arrival sound, and now it enhances ambience even more to the point of introducing a sense of envelopment.

    Quote Originally Posted by KlausR. View Post
    As far as speaker directivity is concerned, the direct sound is the first to arrive at the listener’s ears, and is the reference with which all sounds coming later are compared. The precedence effect works well within its time window provided the spectra of direct sound and first reflections are no too different. Floyd Toole has further found that listeners prefer speakers with response that is flat on-axis and smooth off-axis.
    Very well said.

    To the best of my knowledge Toole didn't really investigate speakers with well-executed polydirectional radiation patterns, which preserve the spectral balance of the first reflections while increasing their time delay and/or intensity and often modifying their arrival direction.

    Quote Originally Posted by KlausR. View Post
    Hence there is a need for controlled directivity, which does not mean that its purpose should be to reduce or eliminate first reflections.
    I think there are many types of controlled directivity, though they may have widely divergent goals as to what should be done regarding reflections - from filling the room with them a la MBL, to reducing them to insignificance a la Sanders Sound. Different designers have different goals, and often the road to that goal lies through their vision of a correct reverberant field. If I recall correctly, the Klein & Hummels you have do an exceptional job of generating smooth off-axis response, and imo that sets them apart from monitors which fail to do so. If the price of entry hadn't been so darn high, I'd have become a Klein & Hummel dealer about ten years ago.
    Industry affiliation: AudioKinesis

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