New Pass Labs Rushmore

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  • Tim
    Junior Member
    • Jan 2003
    • 12

    New Pass Labs Rushmore

    Nelson Pass introduced a new speaker at CES 2003 called the Rushmore http://www.passlabs.com/prodlit/rushmore.htm. I like the appearance of the speaker, but I don't agree with several of the design choices. A 4-way active system with a passive crossover network doesn't seem to make much sense to me. Why bother with separate amplifiers if you are going to use a passive network? The idea of building a cabinet with walls designed to resonate doesn't make any sense to me either. All that vibrating walls will do is add distortion to the sound. I like that idea of a 4-way with high efficiency drivers though, so I may try something similar once it warms up enough in Utah to get my table saw outside again. I have some JBL 2245s and 2234s, so I'm thinking of adding an Audax PR170 or a PHL1120 and a ESG2 to see what I can come up with. My active crossover is only a 3 way so I will have to use a passive network between 2 of the drivers unless I run both of the JBLs up to 350Hz.
  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10940

    #2
    With a wall thickness of 1.25", granite front baffles, curves sides, aluminium extrusions for the rear panel and with a weight of 300lbs /side they certainly aren't going to be very resonate.

    I think you missed the point about the cab construction. Pass thinks composite materials (MDF/HDF/etc) 'sound' acoustically dead and he prefers the sounds of real wood. He implies that it imparts a 'live' sound to the music. But note that he's not talking about making a live = flexible resonating box.

    For XO's he's most likely using using passive line level XO's not standard passive XO's. Those are actually a nice way to go, IF you have control over the power amps being used. Which obviously he does.




    theAudioWorx
    Klone-Audio

    IB subwoofer FAQ page


    "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

    Comment

    • Tim
      Junior Member
      • Jan 2003
      • 12

      #3
      After rereading the brochure, I see that you are correct about the speaker using line level passive crossovers. I based my assumption, that the Rushmore has resonant cabinet walls, on the following statement from the product description: "The front baffle...is made acoustically dead...but the rest of the enclosure has been allowed to remain relatively live, and contributes in its own subtle way to the overall sound of the speaker"(Rushmore brochure, p. 4). Also when discussing speakers from the past, Pass mentions that "wood in the enclosures was flexible and had a sonic signature of its own" (Rushmore brochure, p. 2).
      My line of thinking is that any sound that emenates from the speaker cabinet walls is a form of distortion, unless the cabinet walls are in some way tuned to act as a sort of passive radiator.

      Since I'm interested in reproducing the musical signal as accurately as possible, without adding extra distortion, it seems that it would be better to try to build a cabinet that is constructed to resonate as little as possible, by using special materials and heavy bracing (i.e. Hales and Wilson cabinets) or by using cabinets that have very little surface to resonate (i.e. Linkwitz dipole designs).

      Comment

      • ThomasW
        Moderator Emeritus
        • Aug 2000
        • 10940

        #4
        Nelson Pass is a smart cookie he knows that 'flexible' walls are a bad.

        I think it's a semantics thing. He's associating 'live' with real wood vs MDF/HDF (meaning that MDF/HDF suck the 'life' out of the music) not that the cabinet itself is 'live'. Not sure I agree with his conclusions, but he's making a living in the industry I'm not

        His curved sides are going to be very rigid/stiff, so vibrations won't be a problem. I'm sure a cutaway drawing of his speaker would reveal an interesting arrangement of internal bracing and sub-enclosures.




        theAudioWorx
        Klone-Audio

        IB subwoofer FAQ page


        "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

        Comment

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