Rocket driver construction?

Discussion in 'Archived Threads 2001-2004' started by jad, Jul 23, 2002.

  1. jad

    jad Agent

    Joined:
    Jun 17, 2002
    Messages:
    35
    Likes Received:
    0
    Does anyone know the makeup of the woofers used in the rockets, such as driver basket construction and/or magnet and voice coil size? Their web site says they're a custom designed long throw driver but does not give any other details.
     
  2. Bruce Chang

    Bruce Chang Second Unit

    Joined:
    May 10, 2002
    Messages:
    283
    Likes Received:
    0
    Jad, it makes no difference whether a speaker uses dynaudio drivers and some cheap vifa drivers, it's the design of the overall speaker.
     
  3. SkiingNinja

    SkiingNinja Second Unit

    Joined:
    Aug 14, 2001
    Messages:
    311
    Likes Received:
    0
    Bruce is right that the difference is in the SYSTEM and not just one part....but to answer your question, here is your answer from Dick Pierce:
    Indeed they are custom drivers, with electrical, mechanical and
    acoustical parameters tailored to the specific applications.
    The customization is in several areas, the following being just
    a partial summary of the specific tunings:
    All the drivers have suspension and centering spiders selected
    to achieve the required compliance so as to be matched to the
    cabinet volume, enclosure tuning and cutoff frequency.
    Drivers have had voice coils and magnets designed for specific
    purpose. For example, even though they outwardly look the same,
    the 6 1/2" driver in the RS 250 is NOT the same driver as in
    the RS550 or the RSC200. The former is a nominal 8-ohm driver,
    while the latter's use a nominal 13 ohm driver, so that two
    can be used in parallel without an unduly low impedance resulting.
    However, it is not a trivial task to change a driver's impedance:
    it requires a very careful adjustment of wire size, winding length,
    number of layers and the magnet itself to achieve both the desired
    impedance at the same time as retaining other important parameter
    values, such as electrical damping and efficiency.
    Driver magnet structures use single-piece cold-forged, vented
    pole-piece/back plate assemblies. Single piece forgings of this
    sort have higher efficiencies (due to the elimination of a
    potentially lossy high-reluctance gap between pole-piece and
    back plate), resulting in higher voice-coil gap flux densities
    and lower external leakage. One under-appreciated result of this
    is that the entire magnet system can be placed at the most efficient
    portion of the magnetization curve, and that contributes to better
    long-term stability as well as achieving the required damping and
    efficiencies with less hard magnetic material.
    The vented poles of these magnets contribute to more uniform response
    by eliminating the need to ventilate the voice coil chamber through
    holes punched in the voice coil itself. The resulting increase in
    stiffness of the voice coil reduces flexure at high frequencies.
    The baskets for the woofers and midrange drivers are all carbon-steel
    precision stampings. Much ballyhoo is made of the differences between
    stamped and cast baskets, little of it having anything to do with
    actual performance. Often claims are demonstrated by taking raw baskets
    and examining how they "ring" when struck, but this highly unrealistic
    "test" completely ignores the fact that once the basket is part of
    an ASSEMBLY, including the much more massive magnet structure and
    speaker front baffle, the basket itself is, at most, a small minority
    contributor to the performance. For example, firmly attaching a basket
    of ANY kind to a baffle largely eliminates resonances.
    One of the properties claimed for die-cast aluminum or magnesium
    frames is supposedly better resistance to water. That MIGHT be
    an advantage for outdoor application, however, in working with
    clients in that business, let me assure you that the appearance
    of a cast aluminum frame that has been exposed to even light salt
    air is NOT pretty.
    I hope that helps [​IMG]
    Sean
     
  4. rodneyH

    rodneyH Supporting Actor

    Joined:
    May 22, 2001
    Messages:
    844
    Likes Received:
    0
    Wow, sean, you are all over the place!!

    Also, don't forget the importance of the crossover network (which the rockets is supposed to be very good as well)
     
  5. Cam S

    Cam S Screenwriter

    Joined:
    Jan 11, 2002
    Messages:
    1,524
    Likes Received:
    0
    I'd love to see some pics of the drivers used in these speakers if anybody wants to do so.
     
  6. Russell _T

    Russell _T Supporting Actor

    Joined:
    Aug 26, 2001
    Messages:
    579
    Likes Received:
    0
    The data on the crossovers for these speakers just blows my mind. Mainly because I don't understand most of it. :b
     
  7. jad

    jad Agent

    Joined:
    Jun 17, 2002
    Messages:
    35
    Likes Received:
    0
    Thanks Sean, great reply. I think an audition of the Rs250 might be in order. Have you heard these with the Outlaw 1050?
     
  8. Russell _T

    Russell _T Supporting Actor

    Joined:
    Aug 26, 2001
    Messages:
    579
    Likes Received:
    0
    Cam,
    Gluegun just posted a picture of the Vifa tweeter on AVS under the Rockets thread. It's the black one not the silver one. Also, the Rocket loudspeaker site at AV123.com has cool animated pictures of the models with the grill on and off. If you touch your cursor to one of the pics, it removes the grill.
     
  9. Matt_Briol

    Matt_Briol Agent

    Joined:
    Jun 27, 2002
    Messages:
    41
    Likes Received:
    0
    Here is a pic of the tweeter.
    [​IMG]
     
  10. Patrick Sun

    Patrick Sun Moderator
    Moderator

    Joined:
    Jun 30, 1999
    Messages:
    38,674
    Likes Received:
    423
    It looks mighty excited. [​IMG]
     
  11. SkiingNinja

    SkiingNinja Second Unit

    Joined:
    Aug 14, 2001
    Messages:
    311
    Likes Received:
    0
    I inadvertently truncated part of Dick's reply on the driver makeup...here is the rest:

    The basket design is inherently flush-mounting, contributing to smoother
    on-axis response by reducing or eliminating secondary diffraction effects
    due to sharp transitions. In addition, the rim design has inherently
    better acoustic sealing properties than other baffle designs.

    The cones are all proprietary coated-metal cones, the shape of which
    are spherical segments. This shape is chosen because of its extremely
    high mechanical stiffness. Combined with the inherent high internal
    propagation velocity of metal leads to drivers of very wide bandwidth.
    The coating provides appropriate mechanical damping.

    The surround chosen are high-quality modified polybutadene allows with
    high internal damping and provide suitable termination properties for
    the cones. They have high linearity leading to low distortion and
    very minimal memory effects. One positive side effect to this choice
    of materials is that they do not suffer the deterioration found in
    other surround materials.




    Sean
     
  12. SkiingNinja

    SkiingNinja Second Unit

    Joined:
    Aug 14, 2001
    Messages:
    311
    Likes Received:
    0
     
  13. SkiingNinja

    SkiingNinja Second Unit

    Joined:
    Aug 14, 2001
    Messages:
    311
    Likes Received:
    0
     
  14. Cam S

    Cam S Screenwriter

    Joined:
    Jan 11, 2002
    Messages:
    1,524
    Likes Received:
    0
    The tweeter that the rockets use looks like the ones that are used in the new Polk LSi's?
     
  15. SkiingNinja

    SkiingNinja Second Unit

    Joined:
    Aug 14, 2001
    Messages:
    311
    Likes Received:
    0
    They are the same design but are made with different materials...the Rocket Vifa is an upgrade of the one in the Lsi's.


    Sean
     

Share This Page