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Thread: Charge Coupled Crossover

  1. #16
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JeffW View Post
    It wasn't, evidently, a Greg Timbers discovery but something passed onto him by Ed Meitner, who was not as far as I can tell, a JBL employee. It's entirely possible GT never measured the effect, just relied on his ears to tell him it worked or not.
    Thanks for reminding us of this.

    Contemporary Harman has been led by science and bean counters. If the design team couldn't show the bean counters proof that charge coupling resulted in a measurably superior design at a lower cost than the alternatives, then they must have shown the benefits in their controlled double blind listening tests.

    The bean counters wouldn't sign off on the added expense of CC crossovers if they weren't convinced of its being superior... or a superior marketing pitch. To the best of my knowledge none of Harman's marketing has featured CC technology or given it any more than a passing mention. So, I don't think they were playing the snake oil game like so many in this industry.


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  2. #17
    Senior Member Ian Mackenzie's Avatar
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    No no it’s simpler than that.

    The poster is located in the UK. They see the world differently as often is the case with different continents. But the thing about that lot is that when a bright idea isn’t theirs they carry on and put on a real performance. You know they actually still think they are the hifi industry.

    They can be a bit precious about their Hifi too.

    After the Queen sent her sister over to the US obtain economic support from the president things were never quite the same between the two nations.

  3. #18
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    Firstly can I thank all those who’ve brought some calm and reason to this post. I never thought any replies would become what I can only describe as a ‘rant'. Which somehow managed to include a mention of the British Royal Family. Still it takes all sorts.

    I joined the forum after visiting as a guest many times and always found it informative and open to questioning with many contributors showing a wealth of knowledge and a keenness to assist on all topics JBL related. Having spent over 40yrs working in the broadcast industry I was told from the outset if you intend to make assertions you should be prepared to back them up, with repeatable data. I don’t think its unreasonable to expect a similar approach from others. I’ll leave it there for now, whilst I continue with my 4430 restoration project. But I am hoping in the future to shed some (measured) light on the topic and hopefully give some sort of explanation for the aural perceptions this circuit topology seems to produce.

  4. #19
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    Quote Originally Posted by Epplerd View Post
    Firstly can I thank all those whoíve brought some calm and reason to this post. I never thought any replies would become what I can only describe as a Ďrant'. Which somehow managed to include a mention of the British Royal Family. Still it takes all sorts.

    I joined the forum after visiting as a guest many times and always found it informative and open to questioning with many contributors showing a wealth of knowledge and a keenness to assist on all topics JBL related. Having spent over 40yrs working in the broadcast industry I was told from the outset if you intend to make assertions you should be prepared to back them up, with repeatable data. I donít think its unreasonable to expect a similar approach from others. Iíll leave it there for now, whilst I continue with my 4430 restoration project. But I am hoping in the future to shed some (measured) light on the topic and hopefully give some sort of explanation for the aural perceptions this circuit topology seems to produce.

    Those are all reasonable assertions ( the whole "proof" thing ).

    But consider this :

    A (pair of) speakers ability to "Image" ( from side-to-side plus the ability to portray depth ) are usually considered valued features >> yet are quite immeasurable by todays measurement systems.


  5. #20
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    Quote Originally Posted by Earl K View Post
    Those are all reasonable assertions ( the whole "proof" thing ).

    But consider this :

    A (pair of) speakers ability to "Image" ( from side-to-side plus the ability to portray depth ) are usually considered valued features >> yet are quite immeasurable by todays measurement systems.

    At the risk of sticking my head above the parapet again!

    You are correct it is immeasurable, as there is nothing to measure. In simple terms depth and side to side are an illusion produced by the brain in response to audio clues created when the music was recorded. Level and or phase differences between channels are interpreted as positional information across the stereo illusion and depth is perceived relative to the amount of acoustic added to or recorded with the music. The loudspeakers themselves have no concept of width or depth it's all down to the listener. Different loudspeakers may skew that perception depending on their frequency response, phase response, group delay, coloration, distortion, etc.

  6. #21
    Administrator Robh3606's Avatar
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    Quote Originally Posted by Epplerd View Post
    At the risk of sticking my head above the parapet again!

    You are correct it is immeasurable, as there is nothing to measure. In simple terms depth and side to side are an illusion produced by the brain in response to audio clues created when the music was recorded. Level and or phase differences between channels are interpreted as positional information across the stereo illusion and depth is perceived relative to the amount of acoustic added to or recorded with the music. The loudspeakers themselves have no concept of width or depth it's all down to the listener. Different loudspeakers may skew that perception depending on their frequency response, phase response, group delay, coloration, distortion, etc.
    Now you went and did it!

    Seriously I agree it is mostly in your head. However certain speakers seem to excel at it and 2 that come to mind are both the 4430 and M2. In my experience systems that have a uniform and smooth off axis response and are well matched through their localization range do a better job than those that don't.

    An example my 4344 clones are not image champs by comparison. They are the complete opposite marginal imaging prone to collapse, wall of sound in comparison, very small sweet spot in comparison. As a matter of fact stereo localization was a contributing factor for the 4430 design and is addressed in the white paper for that speaker. It's posted here if you don't have it:

    http://www.audioheritage.org/vbullet...peaker-Systems

    I think that there could at some point be a measurement group that at least loosely defines or is related to how well a pair of speakers image. So I wouldn't be so quick to say it is immeasurable. I doubt anyone has actually done the research and I also realize my examples are subjective. Food for thought.

    Good luck on your restoration.

    Rob
    "I could be arguing in my spare time"

  7. #22
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Epplerd View Post
    At the risk of sticking my head above the parapet again...
    I agree with you that the perception of ďimagingĒ is entirely in our heads. This fact doesnít lessen its importance. The fact is that many of us perceive it and consider it a desirable part of the music playback experience.

    While this effect is controlled by a loudspeakerís polar response, phase response, frequency response, placement in a room, and possibly other factors, we donít have a simple way to quantify it. That doesnít diminish its importance any more than any of the other aspect of this hobby or profession that are considered important by many and are not easily quantifiable.

    To further muddy the waters regarding ďimagingĒ, not everybody is able to perceive it or consider it all that important. Since the illusion of stereophonic playback is entirely an experience created within our own heads, there is a lot of room for differing views on what is important and creating our own performance hierarchies.


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  8. #23
    Senior Member grumpy's Avatar
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    Here's a bit of somewhat related reading fun:

    http://www.princeton.edu/3D3A/MediaCoverage.html

  9. #24
    Senior Member Ian Mackenzie's Avatar
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    The question is why to some loudspeakers and indeed systems image better than others?

    Many reviewers, audiophiles and in my own experience have found absolute symmetry to be important to the perception of imaging.

    But first consider the recording, the venue and the number of microphones and locations. Was it mixed down at the venue or later ? In many cases we don’t know.

    I have generally found the Chesky CD label to provide recordings that offer a natural sense of space, depth and location. Across the record or CD collection there are no consistencies in how a recording is mixed.

    The perception of imaging in my experience is about focus. Much like a lens any system or loudspeaker can have poor focus or sharp focus depending on how it’s set up and adjusted.

    The reflections in a domestic living room have a considerable impact on the direct and reflected sound one heard. The associated room boundaries and distance from the loudspeaker(s) therefore should be equal or symmetrical for both left and right loudspeakers.

    Differences of a centimetre or two are discernible.

    Next the differences in sound level needs to be accurately set for symmetry. This also applies to each loudspeaker and each driver in a multi way loudspeaker. Differences in symmetry of +-0.3 dB can effect the perception of imaging when the left channel for example is not tracking the tonal balance of the right channel of a multi-way loudspeaker. People interpret things differently but l interpret differences in tonal balance, level and enclosure location in not just the onset of a note from an instrument but the space immediately around it that separates it from other notes from other instruments. When the enclosure locations, levels and tonal balance are not symmetrical the effect is washed out, vague or confused.

    Many moving coil cartridges have an imbalance of one or two dB. But it’s assumed the balance should be good. “Don’t assume anything in audio. Everything matters” (A quote from GT).

    It’s interesting to note that GT spends half an hour or so taking measurements from 5 or more locations using a pvc pipe jig around the primary listening position and then adjust the levels before critical listening. It’s hardly surprising that his system sounds so incredibly real and life like.

    Many don’t give these factors a second thought but it’s just as important at home as it is in the recording process. When was the last time any of you measured your loudspeaker locations and matched the left and right levels?

    You might reply that the design of the loudspeakers and the technology is more important.
    It’s counts but the true imaging virtues of a particular loudspeaker are only as good as the setting in which they are used.

    You might ask why such a long post(s).

    In this kind of communication format the interactions are very much short, reactive and not a joint sharing of thoughts. From my perspective it’s not just what you think but the why and how that contributes value.

    It then becomes something useful.

  10. #25
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Epplerd View Post
    At the risk of sticking my head above the parapet again!

    You are correct it is immeasurable, as there is nothing to measure. In simple terms depth and side to side are an illusion produced by the brain in response to audio clues created when the music was recorded. Level and or phase differences between channels are interpreted as positional information across the stereo illusion and depth is perceived relative to the amount of acoustic added to or recorded with the music. The loudspeakers themselves have no concept of width or depth it's all down to the listener. Different loudspeakers may skew that perception depending on their frequency response, phase response, group delay, coloration, distortion, etc.
    I donít necessarily agree with all of your post.

    One of the key measurements of audio equipment pertaining to stereo sound reproduction is channel separation.

    Thatís been around forever.

    ďHaving spent over 40yrs working in the broadcast industry I was told from the outset if you intend to make assertions you should be prepared to back them up, with repeatable dataĒ

    I think you might have taken that remark a bit too seriously at least in the literal sense.

    Lighten up old boy 👦. Donít let the doubters in this world undermine your confidence to speak your mind. Btw l did once but l donít find anything particularly Royal about the Windsors anymore.

    I did enjoy by a tour of the Royal Mews in 2018 by a family friend Philip Barnard Brown, one of her Majestyís senior horseman. Unfortunately the Palace kicked up such a fuss over his media coverage he resigned after nearly 20 years of devoted service. Tells you something about them doesnít it.

    https://www.globetrotting.com.au/phi...of-the-royals/

  11. #26
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    One of the pluses of active as opposed to charge coupled (or passive in general) - I can sit in my easy chair with a laptop and make minute changes in delay, phase, etc. and hear the changes in imaging. I couldn't, even in my wildest dreams, do that with a passive crossover. Some here probably can, I ain't one of them.

    That said, if I could somehow replicate what I have with a passive, the simplicity would be a strong argument in favor.

  12. #27
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    Quote Originally Posted by JeffW View Post
    One of the pluses of active as opposed to charge coupled (or passive in general) - I can sit in my easy chair with a laptop and make minute changes in delay, phase, etc. and hear the changes in imaging. I couldn't, even in my wildest dreams, do that with a passive crossover. Some here probably can, I ain't one of them.

    That said, if I could somehow replicate what I have with a passive, the simplicity would be a strong argument in favor.
    I personally favour active crossovers, which I intend to implement in my 4430's restoration. As you state the refinement of adjustments far exceeds anything possible in a passive crossover. Plus you have the added advantage of transducers being directly connected to the power amp. Of course you can't make a silk purse from a sow's ear, you need to have high quality drive units to start with. I think that's where JBL professional excel, from the start it was all about quality, within the limits of the materials and knowledge of the time.

    Ps is it now time to start a seperate post, 'Mackenzie's Royal Reminisces' ?

  13. #28
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    Quote Originally Posted by grumpy View Post
    Here's a bit of somewhat related reading fun:

    http://www.princeton.edu/3D3A/MediaCoverage.html
    Very interesting. There's a huge amount of work going into audio perception, but as far as reproducing
    sound goes, there's still more than a country mile to cover before loudspeakers become as transparent to the audio signal as electronics are.

  14. #29
    Senior Member Ian Mackenzie's Avatar
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    Audio and Capacitors- This document explains the importance of particular characteristics for audio signals

    https://www.wima.de/wp-content/uploa...WIMA-Audio.pdf

    Reference to pulse rise time and pulse behaviour is interesting.

    One of the problems with measurements is how to measure the component under test in a real circuit?

    Typically the part will go to the test lab and the technician will test the part like everything else he tests which is usually outlined in the AP manual. The test signal may only be suitable for 50 or 100 ohm loads out of the analyer. The the part is connected to a 100R load. The technician does not think twice about or because thatís the way he was trained. The loudspeaker engineer only does his job and he is too busy to learn about distortion tests of capacitors.

    But in the real circuit the part interacts with other crossover elements that form resonance by virtue of the filter functions time constant and the load impedance is much lower but can vary with frequency.

    The music signal while a sine wave is a random and complex number of harmonics with constantly shifting amplitude.

    Itís not a constant steady state sine wave or a standard lMD test.

    This is the disconnect in large corporations where functions are departmentalised. The chief loudspeaker engineer gets the report back with the measurements.

    Smaller organisations donít have the resources to undertake such research. Instead they build to a cost or put in flavour of the month audiophile capacitors that might get the attention of the audiophile consumer.

    Then there are personality types with an autocratic approach to running the business and set beliefs like Nelson Pass who put in the cheapest or most economical part from the Digikey catalogue. Capacitors are not on the radar. They might end up with half a dozen electrolytes in the signal path because itís the easiest way to design and build a piece of equipment. These are the challenges and the economic forces facing audio sound reproduction.

    But in the diy space you donít have to live with these constraints. But you need to understand whatís important and where to spend your money,

  15. #30
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JeffW View Post
    One of the pluses of active as opposed to charge coupled (or passive in general) - I can sit in my easy chair with a laptop...
    Yes, very cool. The control and flexibility available today is amazing and was impossible a couple of decades back. Unfortunately to do this you have to find a digital crossover that you like and it needs to be networked. These days there are many to choose from that will sit on your LAN, but I haven't found one for my use that quite does it for me sonically. I am still waiting for them to improve or my hearing to fail.

    You mention the simplicity of a passive system... there is a lot to be said for that. I have a 5' rack of gear running my 2 channel system and that doesn't include the sources or the preamp. Admittedly Class D amps and a 1 or 2 U digital crossover would remove a lot of the bulk. It would also reduce the energy use and heat. My system really warms up the Guest Bedroom.


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