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Thread: Sierra - The Crossover

  1. #1
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    Smile Sierra - The Crossover

    At the heart of the Sierra is OPPIX™.

    OPPIX stands for Optimized Paradromic Phase Integrated X-Over (crossover). This sophisticated variable slope crossover precisely aligns the acoustic phase response of multiple transducers at the exact point where the response of one transducer crosses over to another, with reference to a specific point in space. This precise alignment allows the transducers to mimic a single point source radiator, allowing for symmetrical dispersion even with an asymmetrical transducer layout while maintaining a linear frequency response and greatly reducing off-axis phase and response anomalies. It also avoids the undesirable frequency response anomalies commonly found with even the best coaxial drivers.

    As an example, examine the off-axis measurements of these 2 popular high-end 2-way loudspeaker using a common tweeter-woofer driver layout (see below). Notice the dramatic difference in the off-axis frequency response above and below the speaker (vertical symmetry). Also compare the horizontal response to the vertical response. This is a typical asymmetrical response, and since what we hear in a room is a combination of direct-sound and reflected-sound from all directions, even though the on-axis response might be flat, the asymmetrical loudspeaker will deliver a less accurate response, since the speaker performance varies dramatically off-axis.


    Competing 2-way loudspeaker


    Another Competing 2-way loudspeaker


    Now notice how symmetrical the Sierra’s off-axis response measurements are (see below).. Symmetry is maintained up until the point where the length of the sound waves become less than the distance from the source to the edges of the baffle. In the case of the Sierra, precise response symmetry is maintained from 40Hz up to approximately 10kHz, at up to 25 degrees off-axis. This translates to accurate in-room performance, a “correct” soundstage with precise imaging, and allows the Sierra-1 to perform to spec when positioned vertically or horizontally. OPPIX™ also allows the Sierra to perform exceptionally well as a vertical or horizontal main and a vertical or horizontal center. I recommend three Sierras in the front (left, center, right) for the ultimate in timbre matching and soundstage consistency.


    The Sierra-1


    Another feature of the Sierra crossover is maintaining extremely linear electrical impedance. From 1 kHz up through 20 kHz, impedance varies by only ±3 ohms, from 2 kHz up, by a remarkable ± 1 ohm. You will also notice that impedance does not rise as frequency increases. This translates to an easy load for any amp and consistent performance from one amplifier to another. We have tried the Sierra on a host of receivers and amplifiers and it delivered consistent performance from all of them.


    The Sierra-1 Impedance + Electrical Phase



    This advanced crossover also features:
    • High-performance metalized polypropylene capacitors in the direct signal path, these offer lower dissipation than the more common polyester based film capacitors
    • Air-core inductors to reduce saturation effects combined with heavy gauge windings to reduce resistance and improve efficiency
    • Low inductance resistors to reduce distortion and provide accurate transient information
    • Heavy gauge internal copper wiring
    • Linear impedance response for consistent performance regardless of amplification source
    • Isolation mounting, whereby the crossover is attached to the cabinet using isolation feet, which reduces the transfer of resonances from the cabinet to the crossover components


    Optimizing this crossover and developing the technique and circuit topology to accomplish this was my most rewarding and challenging aspect of this loudspeaker…



    The Sierra-1 Crossover


    The Sierra-1 Center with rotated tweeter (a FANTASTIC center speaker)






    Woofer and tweeter tomorrow
    Last edited by davef; 05-17-2007 at 04:08 AM.
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  2. #2
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    Very impressive. Does this mean they are phase aligned from 40hz to 10khz?
    Last edited by Quinn; 05-17-2007 at 04:16 AM.

  3. #3
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    Very nice Dave! Identical speakers across the front, like the 340's, but with better dispersion characteristics.

    Will that center speaker match well with my 170's?
    Ed

  4. #4
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    This is fantastic stuff. And here I was ready to order the 340's within the next month.

    Congrats to you and the company Dave, it's great to see you succeed.

  5. #5
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    Ed...no it won't, your buying my 340 remember!
    Jeff

  6. #6
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    Quote Originally Posted by debo
    Ed...no it won't, your buying my 340 remember!
    ....but the piano black finish will better match my new AQUOS 32" HDTV!!

    Jeff, it will come down to price, my patience, and willingness to save up for one of these. If people are gaga over these once they start getting them, I will definitely be considering the Sierras! Do give me a price for the 340 though.
    Ed

  7. #7
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    Very Interesting Stuff!!
    -curtis

  8. #8
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    I'm digging the natural bamboo finish a lot. It will definitely require very little maintenance, while daily dusting/polishing of the piano black may be needed.

    I noticed that the grill mounting holes for the center are in the same locations as the L/R, while the grill itself has been lengthened to cover the entire front of the speaker. Where will the logo go?
    Ed

  9. #9
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    For the center, my guess is that you can put the logo on the grille if you wish.
    -curtis

  10. #10
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    Default Subwoofer Integration

    Hi Dave,
    what would be an ideal crossover point for Sierra's from subwoofer? Now, when are you taking orders for these?? Can you book me a pair+center channel?

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