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Thread: I Knew They Were Something Special

  1. #1
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    I Knew They Were Something Special

    When I acquired my Super Reds with the electronic crossover and eq units, I knew they were something special (rare) but could find no information on them. Someone saw them on AudioKarma and rememberd an old magazine article mentioning them. Apparently there were 30-40 of these time aligned electronic "Time Sync" crossovers made for use with the Super Reds. They were made by AudioTechniques.


    https://lens.google.com/search?p=ASQ...1URmhPUT09Il0=



    https://worldradiohistory.com/Archiv...DB-1982-08.pdf

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    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by toddalin View Post
    Dead link

    Clip and this is what I got: https://worldradiohistory.com/Archiv...ng-1980-06.pdf
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Administrator Robh3606's Avatar
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    Great articles! Nice history on the 604! Have to edit it and get it into the Library.

    Rob
    "I could be arguing in my spare time"

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    Senior Member grumpy's Avatar
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    A fun read. Thanks Todd. Good job saving those from the crusher!! and that you found out more about their place in 604 history (as Rob said ).
    Did seem like there had to be more to these

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    Quote Originally Posted by BMWCCA View Post
    Dead link

    Clip and this is what I got: https://worldradiohistory.com/Archiv...ng-1980-06.pdf
    Thanks.

    My crossover looks nothing like the one AudioTechniques sold and shown on pages 115 and 117.


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    l recall hearing them at Todd’s.

    A great story.

    It confirms three things to me.

    Listening to the original 604 dual concentric design does drive you crazy as confirmed by Doug Sax. That in those days acclimation was more important to studio users than absolute accuracy. What ever large monitors got in the recording industry back then stayed in due to the need for consistency.

    In comparison it’s interesting that multi way loudspeakers were all the fad in the consumer hifi market place from the 1970’s right up the present. Very few brands promoted time aligned loudspeaker in the Ads. Some brands used stepped baffles to align loudspeaker drivers.

    I tend to agree that time alignment was/is only discernible on certain kinds of program material.

    What we do know is that driver voice coil offset can impact on the smoothness of the frequency response in the vertical domain. If you stand up and listen it will sound tonally different to sitting down. This is due to differences in path distances caused by geometry angles which causes phase cancellation in the crossover region. This also applies to dual concentric loudspeakers.

    Time alignment can only be accomplished on axis with dynamic drivers.

    My preference is a loudspeaker that is fundamentally accurate with discernible few time alignment flaws over a loudspeaker that compromises absolute accuracy for exact time alignment.

    I don’t think any can argue the point on that but this could end up a very long thread.

    Bring it on……Lol.

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    Quote Originally Posted by Ian Mackenzie View Post
    ...My preference is a loudspeaker that is fundamentally accurate with discernible few time alignment flaws over a loudspeaker that compromises absolute accuracy for exact time alignment...
    Well, that's a broad brushstroke. I'll narrow it down by saying you can't have absolute accuracy without nearly perfect accuracy in the time domain. Maybe that can't be argued with? ;-)

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by rusty jefferson View Post
    Well, that's a broad brushstroke. I'll narrow it down by saying you can't have absolute accuracy without nearly perfect accuracy in the time domain. Maybe that can't be argued with? ;-)
    I’ll narrow it down further. You can’t have absolute accuracy. Period.

    That said, I think it is obvious that absolute accuracy is not needed for musical enjoyment.


    Widget

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    No, but the pursuit of it is.

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    Administrator Robh3606's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post

    My preference is a loudspeaker that is fundamentally accurate with discernible few time alignment flaws over a loudspeaker that compromises absolute accuracy for exact time alignment.

    I don’t think any can argue the point on that but this could end up a very long thread.

    Bring it on……Lol.

    I agree as well. Time alignment and phase coherence are greatly overrated. Frequency domain is much more important.

    Rob
    "I could be arguing in my spare time"

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Robh3606 View Post
    I agree as well. Time alignment and phase coherence are greatly overrated. Frequency domain is much more important.

    Rob
    +1

    The stepped baffles, staggered arrays, "time coherent" crossovers, and even the rounded corners of the past while not irrelevant are really only the last 10%... you gotta get the 90% right first!


    Widget

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    Hi Rob,


    Altec 604
    Looking at the 604 design it’s kind of odd that Altec either had their heads in the sand or perhaps were playing it safe and decided to keep the 604 as the original.

    At the time DB Keele Jnr had involvement with Altec’s manta ray horns and then worked on JBL’s bi radial horn for the 4430/4435.

    I am wondering why Altec did not leverage Keele’s horn design expertise in developing the 604 to maintain its position in the market?

    Around the late 1970’s to early 80’s Altec re-launched its brand into consumer hifi with the model 19 as the flagship, the model 17 (604 design) and the smaller systems. I heard them all at a demonstration arranged by the distributor. It’s was all about a big reverberant sound. At that point in time (pre cd red book) it was impressive but l personally felt that the bass was lacking.

    More recently Great Plains Audio have picked up the 604 and made an attempt to offer an iteration but l am unaware of how far they went on R&D to improve it or just a different take on the 604?

    Perhaps someone can chime in with any relevant information on the Great Plains 604.

    Kef Uni-Q
    Interestingly Kef’s head of acoustics now with Kef for 15 years has made significant R&D advances into the Kef Uni-Q dual concentric driver HF lens/wave guide. In a YouTube he explains how how the planar action of the HF diaphragm is converted into a wave squeezing action via a mathematically derived waveguide/acoustic lens. The outer mid cone then continues the development of the wave front.

    The Hi end variant of the Uni-Q driver used in the Kef Blade and reference series has a very large voice coil that is terminated mid way from the centre of the mid range diaphragm to the surround. Kef R&R has engineered a special lossy plastic decoupling to terminate the voice coil to the metal diaphragm. The lossy coupling is activated at frequencies above the crossover point forming an acoustic low pass filter. This effectively suppresses high order break up resonances from the metal mid range diaphragm by attenuation of high frequency vibrations.

    Pretty clever engineering. The driver is a work of art.

    https://m.youtube.com/watch?v=mR1m0U4xZvY

    https://m.youtube.com/watch?v=9Lij_9adOYE

    R&R from Kef’s sister company Celestion is shared with both businesses.

    https://celestion.com/products/?fwp_...riodic-drivers

    https://celestion.com/key-technologies/


    Other coaxial driver manufacturers
    Over at Radian they are mounting Ribbon drivers into their coaxial driver units as s as n alternative to compression drivers. Their co axial driver are relatively affordable for us audio amateurs.

    RCF and others also make very good coaxial drivers in various sizes available from

    https://usspeaker.com/homepage.htm

    I thought this might be of interest to the thinking cap type of audio amateurs who like to seek out new approaches to sound re production. I do not believe that a high quality coaxial driver is an exclusive design and nor should it be expensive. An interesting project for the audio amateurs. These other manufacturers have improved these coaxial designs in recent times. They have received good reviews on Voice Coil an industry journal. If interested l would be looking at the aluminium or titanium version over the exotic beryllium until you get an idea of what they can do. Radian would be my pick but l would also look at the others.

    As a side note while the top Kef system are expensive the key tech is engineered to lower price points.

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    Senior Member Ducatista47's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    I’ll narrow it down further. You can’t have absolute accuracy. Period.

    That said, I think it is obvious that absolute accuracy is not needed for musical enjoyment.

    Widget
    I could not agree more, I enjoy listening to 1930s recordings if the music is great.

    Even so, I continue to be let down over how few music enthusiasts seek reproduction that attempts to follow as closely as possible what went into the microphone. You know, what the musicians actually did. As I have said before, it seems everyone has their favorite distortion; euphonics is the biggest flavor in high end audio. I have passed the point where speakers can come close enough to the truth to compete with what a modest personal listening system can do, so I have nothing to contribute anymore to speaker discussions. But I still like to hear what you guys have to say and report about it.

    Since we now actually know how to record accurately and create media (streaming included) for home use that reflects that result, I do find it strange how much money and toil one will put into improving speakers, which will still have a couple of orders of magnitude more distortion than the electronics that drive them and at least another order of magnitude worse than the source material. If one is chasing perfection speakers are not a fitting tool to do it with. Playing music euphonically should not cost much. Simply accepting the shortcomings of the tools we enjoy anyway seems a more rewarding path than dwelling on the ways we wish they were better.

    Remembering the vinyl era, we ancient ones often have to explain that we didn't even hear the pops and cracks. We learned to ignore them. Speakers are like that, if we let them be. Our brains know what music sounds like and it does a fine job of filling in the blanks both speakers and listening rooms get wrong, and tweaking towards reality.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


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    Quote Originally Posted by Mr. Widget View Post
    +1

    The stepped baffles, staggered arrays, "time coherent" crossovers, and even the rounded corners of the past while not irrelevant are really only the last 10%... you gotta get the 90% right first!


    Widget
    Hi Widget,

    In your view what is the 90%?

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