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Thread: CBM-170 Signature Edition (SE)

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    Post CBM-170 Signature Edition (SE)

    CBM-170 Signature Edition:

    Every tweeter has a sweet spot in its response range where distortion is lowest and resolution is greatest. This range usually begins an octave or two above resonance and continues until the tweeter’s impedance begins to rise. For typical dome tweeters, impedance rises as frequency increases and while this can be somewhat compensated for in a crossover (Zobel network) it is still audibly evident. As frequency and impedance increases, instruments tend to blend together and lose distinctness, lose delicacy. As frequencies decrease and approach the tweeter’s resonance (typically between 2 – 4kHz) distortion increases dramatically and the sound will become “edgy”.

    2 years ago we began researching ways how we could expand our tweeter’s sweet spot. It was soon realized that this would require lowering the resonant frequency and making massive modifications to the motor assembly of the tweeter. We sampled dozens upon dozens of highly regarded neodymium tweeters from such prestigious companies as Vifa, Peerless, Morel, Foster… and dozens from various Asian manufacturers.

    It was quickly realized that lowering the resonant frequency would require use of a chambered tweeter. A tweeter that was designed with a large air-pocket (a damping chamber) behind the dome, thus increasing the compliance of the air behind the dome (same principal as increasing box volume to improve bass response).

    Many of the well regarded tweeter manufacturers are starting to produce chambered tweeters, but these are large, heavy tweeters using bulky ferrite magnets. We desired a chambered compact neodymium tweeter with similar timbre to our current tweeter.

    Enter SEAS of Norway… synonymous with high-end audio and simply the highest quality tweeters in the world today. We approached them with our exact requirements and much to our surprise, they were interested.

    Almost 2 years later... success!

    I am proud to introduce what I feel is the world’s very best compact neodymium tweeter. The only double-chambered compact neodymium tweeter than I know of. It is truly one-of-a-kind being built specifically for us by SEAS of Norway. A fully custom design and you will simply not find a more advanced tweeter in ANY loudspeaker at this price point.

    Flat response to 22kHz, a very low resonant frequency and very low distortion all combined with exceptionally wide dispersion. Smooth and accurate to an entirely new level...

    Please see the below pictures. Notice the magnet assembly of our new tweeter compared to a very well regarded compact neo tweeter built by Vifa and another very well regarded compact neo tweeter found in a bookshelf speaker that costs more than twice as much as the CBM-170.


    ours is in the middle of course

    Notice the damping chamber with acoustic foam removed.





    There is even a second damping chamber behind the chamber with the foam plug.


    These chambers effectively lower the resonant frequency and also serve to absorb and cancel the back sound-wave produced by the tweeter’s dome, which bounces off the magnet and travels back out the front of the tweeter causing phase problems which leads to smearing and a loss of detail.




    Next up on the CBM-170 SE.. Woofer Improvements:

    While not nearly as dramatic a change as the tweeter, we have incorporated a few improvements to the CBM-170 woofers.

    We have reformulated the cone material changing one of the components of the original aerogel. We have found over the years that while aerogel offers excellent detail, at loud volumes it becomes a bit “edgy” sounding and we determined that this was due to aerogel being a bit too brittle, corresponding to large cone-breakup modes at medium to loud volumes.

    The new woofer sounds and looks the same but the modified cone material is more durable which subsequently allowed us to increase excursion and utilize a more powerful magnet, thus improving bass response and impact.

    Brief summary of overall performance improvements:

    • Improved high-frequency extension, transparency and smoothness
    • Deeper bass with faster transient response, noticeably more "punch"
    • Class-leading low distortion measurements
    • Higher power-handling


    Combination ground plane (for accurate LF response) + on-axis (for accurate HF response) at 1 meter.



    sensitivity = 89dB @ 1w @ 1meter
    Last edited by davef; 10-18-2006 at 04:46 AM.
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

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