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Thread: EVEREST DD66000

  1. #91
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    Smile Lansing Heritage

    Here's Stereo Sound's HiViweb assemblage of the DD66000's ancestors.
    Attached Images Attached Images  
    Out.

  2. #92
    Senior Member Steve Schell's Avatar
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    The covering on the woofer baffle boards is leather; not sure if this has been mentioned already.

  3. #93
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    I think that's the first I've read about it. Is it 'Roo leather, like my old Adidas track shoes?
    Out.

  4. #94
    Senior Member Don C's Avatar
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    I think that they are stunning, and they look better each time I see the pictures. Bravo.

  5. #95
    Senior Member Steve Schell's Avatar
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    The DD66000 really does look stunningly beautiful in person, a design for the ages fully in keeping with the standards set by the Hartsfield and Paragon. Dan Ashcraft and his team did a stellar job with the industrial design.

    They also sound quite splendid as you might expect, and exceeded my expectations for a horn system with a direct radiator low end. Greg Timbers is the best there is at selecting and blending elements to create a unified whole, and many high end speaker designers could learn an awful lot from him. I suspect that Jim Lansing would be proud of the work that Greg has done here and throughout his career at JBL.

  6. #96
    Senior Member Ducatista47's Avatar
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    Quote Originally Posted by Steve Schell

    They also sound quite splendid as you might expect, and exceeded my expectations for a horn system with a direct radiator low end. Greg Timbers is the best there is at selecting and blending elements to create a unified whole, and many high end speaker designers could learn an awful lot from him. I suspect that Jim Lansing would be proud of the work that Greg has done here and throughout his career at JBL.
    And how. Think of the complexities involved in designing the four-way 43xx cone/horn monitors. I give Mr. Timbers a silent thank you every time I listen to my 4345's. For me, he is THE MAN.

    Wish I could afford his new creation. Since it seems to blow away whatever came before, it must be desirable beyond words.

    Clark in Peoria
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  7. #97
    RIP 2013 Rolf's Avatar
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    Quote Originally Posted by Mr. Widget
    The post isn't going anywhere... but yes, Sgt. Schultz has left the building.


    Widget
    Why?

  8. #98
    Senior Member Hoerninger's Avatar
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    Sgt. Schultz had to go by law and order,
    I suppose.
    Don McRitchie has changed forum rules, he has an better insight than we do:
    http://audioheritage.org/vbulletin/s...73&postcount=1
    ___________
    Peter

  9. #99
    Senior Member spkrman57's Avatar
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    Maybe the next mysterious post will be by Col Hogan!

    I don't question how I get info, just happy when it happens.

    Ron
    JBL Pro for home use!

  10. #100
    TimG
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    DD66000 white paper in Japanese

    It looks like the sections of the white paper are already posted here, but I can't figure out how to translate it.

    http://www.jbl60th.jp/

  11. #101
    Member jack_bouska's Avatar
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    Some questions related to the design of the D66000

    I have reviewed the recent posts on the DD66000, and had a look at the technical information on this site, and on the 60th anniversary JBL-Japan site, and I'm embarrassed to say the information raises more questions than it answers. In the hopes that some members of this forum can shed more light on the subject, I would like to ask a few basic questions about the design choices, as follows:

    1) The low frequency cutoff -3dB point (45 Hz) has already been mentioned as being somewhat on the high side for a world class system of such high cost, however a ported system typically exhibits a 4th order roll off below the F3 point, however the DD66000 shows 2nd order rolloff (-24dB at 20hz). The ports appear to be vented to a common cavity, so are the two woofers identical, or do they have different TS parms (Fs, Vas, Qt, etc)?

    2) What frequency are the pair ports and interior volume tuned to?

    3) If the ports are tuned to a much lower frequency than cut-off, can electronic bass boost be added to safely extend response?

    4) The DD66000 specifies the capability for bi-amping. Is this true bi-amping, or simply bi-wireing? If bi-amping, then does JBL market a separate high level crossover for this unit?

    5) The pair of woofers operate in parallel between about 45Hz and 150 (or 200) Hz, with one of the woofers rolled off above that. The low end choice appears reasonable, as the woofer centers are spaced within 1/4 wavelength for all frequencies below 200Hz, but the roll off of one of the woofers (labeled LF1) leaves the 2nd woofer (labeled LF2) slightly off-center on the front baffle. At low frequencies, this will be undetectable, but nearer the upper crossover frequency (listed as 700Hz on the spec sheet) this may create astigmatic coverage by inducing a 45 deg tilt to the plane of constant phase in the crossover overlap region (approximately 1 octave between -6dB points according to the published curves). Most modern designs tend to place the drivers in a vertical line, so that the isophase plane is invariant in the horizontal axis, ensuring all listeners (at seated ear height) across the area of coverage hear the same frequency response. With the active woofer offset by ~10" from the vertical line running through the tweeter center, any shift horizontally will result in variation of the path length between woofer and tweeter, creating significant lobeing in the directivity/frequency response (over the 1 octave overlap region) as the angle between listener and front baffle axis is varied. The question is: has JBL done something special with this design to mitigate this effect?

    6) The pictures, and drawings indicate sharp edges, both on top (into horn flare), bottom, and sides (with protruding edges on the sides). These abrupt baffle terminations are likely to cause significant diffraction effects for the LF2 woofer, which will have 180 degree directivity coverage up to a frequency of ~700Hz. A single driver on a square baffle measuring 40" x 40" would produce a strong peak-trough-peak frequency ripple in the response, which would occur at 300, 600 & 900Hz. While it is true that the non-symmetric placement of the LF2 woofer on the front baffle will suppress some of the frequency response anomalies, it is also the case that the rapid acoustic impedance contrast at the baffle edge will act as a distributed set of secondary sources, 180degrees out of phase, and temporally displaced from that of the main LF2 wave front. These delayed secondary sources have been reported (by researchers such as Geddees) as being both audible, and objectionable, despite careful asymmetric driver placement, and smooth on axis frequency response. The question is: has JBL done something special with this design to mitigate audible diffraction effects?


    7) The generous dimensions of the front panel are echoed by a pair of significant measurements across the internal volume of the DD66000, about 38" high, and 30" wide. These two dimensions will generate cavity resonance modes of ~175Hz, and ~215Hz. (plus harmonic modes) The back panel is curved, so the front to back resonance will be much higher in frequency (1st mode ~550Hz), and distributed due to the variable depth. The horizontal and vertical dimensions do not vary appreciably, so the modal resonances will be present within the enclosure. Indeed, two small response bumps are visible on the graph from post #67 at 175 and 220Hz. without seeing a waterfall plot, or cumulative spectral analysis, I am unable to discern if these response anomalies are under damped or not. So my question is: what has JBL used (other than judicious application of fiberglass batting) to attenuate these internal resonance modes?

    8) I also note that the horn appears to be a bi-radial, with published coverage of 100deg x 60deg. The 100deg coverage (+/- 50deg horizontal axis) is a trifle wide, and means that however the speakers are angled, they will always generate an early reflection from either the side walls, or the wall behind the speaker. These early reflections are notorious for interfering with high resolution imaging. For example, corner placement with a 80deg CD horn simultaneously avoids reflection from the near side wall and back wall, and can generate near holographic imaging in a good design. The question is this: how does JBL recommend setting these speakers up in a normal living room?

    9) The horn mouth also appears to have little, if any radius or gentle flare rate change transition into the plane of the front baffle, all the edges appear quite sharp. Although this is visually dramatic, it is also known to have adverse sonic implications. The abrupt termination at the horn mouth generates significant diffracted energy, which appears as an acoustic impedance contrast that sets up internal resonances, between mouth and phase plug, within the length of the horn. These resonances are responsible for much of the dreaded "horn sound", and create a comb filter effect which is visible as ripple on a standard frequency response graph. The physical length of the resonating chamber and time period of resonance is related to the periodicity of the ripple on the response by the equation Reflection time = 1/Fp. When I study the response graph from post #67, I can clearly see a series of ripples with a period somewhere between 1-1.2kHz. This corresponds to a resonant temporal period of ~.85 to 1ms, or a (two way) path length of about 30-35cm. This would mean a path length in the horn (from mouth to throat) of approximately 7", which seems to correspond to the device in the DD66000. My question is this: Why has JBL chosen to use a bi-radial horn, with poor mouth termination, when the JBL-Pro division has very sophisticated devices which perform to a much higher standard (both for CD, and acoustic impedance matching.)

    9) The last question is generic, and relates to the employment of a passive crossover, in what is supposed to be a cost-no-object state of the art system. Most modern studio monitors, and almost all large public address systems use active filters, and multi amp drive. Significant advances have been made in the area of digital crossover controllers, and indeed JBL was among the first to employ this successfully with the DMS-1 monitor. So my last question is this: Does anyone know why JBL chose to use passive crossovers instead of the much higher fidelity route with a digital-active multi-amp configuration?

    Thanks, I'm just curious,
    Jack Bouska

    Oh, forgot to ask one more question:
    10) The documentation lists the horn as covering 100x60deg, however the operating woofer LF2 will not have significant directivity narrowing except at frequencys above the crossover point, reaching 100deg at just above 1kHz, and 60deg at beyond 2kHz. This will means that the LF2 and horn will have differing sold-angle coverage patterns just below, throughout, and just above the crossover point. This has been identified in the JBL sound system design manual as leading to problems in balancing the EQ between the direct and reverberant sound fields. My question is this: how has JBL balanced the DD66000? Have they focused more on the direct arrival, or on the reverberant portion (in a “typical” living room?

  12. #102
    Administrator Robh3606's Avatar
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    Does anyone know why JBL chose to use passive crossovers instead of the much higher fidelity route with a digital-active multi-amp configuration?
    Hello Jack

    My guess would be SACD/DSD and analog sources would have to encodded. Not everyone is on the bandwagon that digital is completely transparent. There is a schematic posted in the earlier part of the thread to answer your biamp questions. The woofers can safely handle EQ. More later.

    Rob

  13. #103
    Member jack_bouska's Avatar
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    Quote Originally Posted by Robh3606
    Hello Jack

    There is a schematic posted in the earlier part of the thread to answer your biamp questions.

    Rob
    Thanks for the reply - I have briefly reviewed the schematics, and my interpretation of the bi-amp switch positions indicates that the bi-amp setting would by-pass the passive crossover between LF2 and HF drivers, while leaving the response tailoring (EQ) for LF1, and HF in circuit. (the HF to UHF xover is always in circuit). This "halfway house" appears to allow the end user to insert a generic 2nd order (or higher) active crossover, and facilitate the use of two stereo amplifiers to power the system. Leaving the response tailoring, gain setting, and HF-UHF xover in circuit relieves the end user from the requirement of emulating the complex EQ using whatever generic "off the shelf" active filter set that they decide to use.

    This still begs the question as to why JBL would design a system for bi-amping without providing an application specific active (digital -or- discrete/analogue) crossover option, so that all the attendant the insertion loss (from the passive gain setting), and complex impedance baggage from the response tailoring inductive & capacitive components (left in circuit) could be eliminated?

    Quote Originally Posted by Robh3606
    Hello Jack

    Not everyone is on the bandwagon that digital is completely transparent.
    Rob
    I agree with your statement that "not everyone is on the bandwagon that digital is completely transparent", yet I am always left wondering how difficult it must be for these same people to select any modern CD/DVD-A/SACD recording that has NOT undergone some level of digitization and DSP manipulation during the recording / mastering process. The licensing agreements for SACD and DVD-A might force the output to always be in the analogue domain, however in my experience, re-digitizing this signal (for room correction, EQ, or DSP based xover) causes little (if any) audible degradation of the signal. Claims of digital degradation occur frequently in conversations among my audio friends, and apparently, on web forums as well. Rather than be swayed by anecdotal, 2nd hand subjective conjecture from the self appointed audiophile-intelligentsia, I invariably find myself forced to rely on my own experience (from my aural auditions), backed up by my own acoustic measurements, both of which tell me that properly implemented digital based DSP is mostly indistinguishable from analogue processing, while providing a comprehensive toolkit of EQ and crossovers which would be problematic to implement using discrete analogue components.

    Jack Bouska

  14. #104
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    Jack,

    I agree with your insights however the overriding considerations may have more to do with the sensitivies and sensibilities of the intended market audience. The risks involved in attempting such wizzard like stuff may offend and cause more buyer restance than you or I might appreciate.

    JBL did what you are expressing with the DMS1 however it was not a notable success story nor a system that was sonically rewarding despite the techncial brillance.

    Meridian has an all active digital loudspeaker but I have not heard it demonstrated. I think if JBL were going this route they would do what Meridian has done and package it with self power amps as well.

    That is a real leap into the future and I doubt if JBL or the market is ready for that yet.

    Doing the digital thing also takes away some of the skill and romance of the analogue speaker designer and the subtle voicing that is required to create such a system.

  15. #105
    Member jack_bouska's Avatar
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    Quote Originally Posted by Ian Mackenzie
    Jack,

    I agree with your insights however the overriding considerations may have more to do with the sensitivies and sensibilities of the intended market audience. The risks involved in attempting such wizzard like stuff may offend and cause more buyer restance than you or I might appreciate.
    Ian - You make a very good point. Given the target audience, which might be comprised of wealthy, ageing, Japanese audiophiles who long for the look (and sound) of 1960's American HiFi consoles, I can see why the specific layout, and design choices of the DD66000 make somewhat more logical sense, in that narrow market. It also becomes more clear why JBL will not promote this item outside of Japan, it probably wouldn't sell.

    Not because there is no demand for expensive speakers, (has Wilson audio stopped shipping worldwide?), but because the retro-sound of the D66000 probably can't compete with other expensive offerings. Of course, never having heard the DD66000 myself, I could very well be accused of "posterior oration" on the last point. Clearly I'm just looking a few graphs, and pictures of the unit, and guessing as to it's sonic performance.

    Quote Originally Posted by Ian Mackenzie
    JBL did what you are expressing with the DMS1 however it was not a notable success story nor a system that was sonically rewarding despite the techncial brillance.

    Meridian has an all active digital loudspeaker but I have not heard it demonstrated. I think if JBL were going this route they would do what Meridian has done and package it with self power amps as well.

    That is a real leap into the future and I doubt if JBL or the market is ready for that yet.
    I'm going to do a full 360degree turn, and drop the suggestion of DSP based EQ and Crossover implementation, it's just a red herring which is deflecting the underlying design questions which I raised earlier. Of course it is entirely possible to implement a serviceable active crossover and simple parametric room (bass) EQ using fully analogue electronics.

    Quote Originally Posted by Ian Mackenzie
    Doing the digital thing also takes away some of the skill and romance of the analogue speaker designer and the subtle voicing that is required to create such a system.
    A simple example of technically competent, fully analogue implementation of professional quality, bi-amping with room correction, comes readily to hand from JBL themselves.

    Please take a moment to review the first page of JBL tech note vol 3 no 2a:

    http://www.jblpro.com/LSR/PDF/JBL.tn_v3_2A.pdf

    I'm still curious as to why JBL did not implement *any* of the relatively simple technical features (LSR, RMC) listed on the first page of that document (apart from Hi-Tek drivers, and internal cabinet bracing), in this very expensive Everest system?

    Jack Bouska

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