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RE: Dragonfly

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In Reply to: RE: Dragonfly posted by Roy Lewis on September 10, 2008 at 13:01:43

Hi Roy,

the DF design is made to get maximum fundamental and dynamic basses out of a slim speaker. It isn`t a "classical" horn- design, DF offers much more fundamental basses than other compact horn- designs using drivers of similar size, this design can`t be calculated with existing formulas.
DF is a floor firing- design, also a solid rear- wall is needed to couple the horn- mouth to the room, so the virtual part of the horn- mouth is big compared to other horn- designs. To tune the "system" of speaker in- room to a low frequency results that differences in sound provided by differences in the physical and virtual hornmouth- area are small. The design of the DF horn helps to compensate different room- geometries and placements by "built-in" modifying the size of the virtual opening.
In opposite to the mouth the exact size of the throat of the DF design is extremely important, the closer to the driver the more important. This area is responsible for the proper function, a failure here can`t be compensated by modified hornmouth or placement.

Regards
Robert Bastani

http://www.bastanis.com (Open in New Window)

Follow Ups:

RE: Dragonfly - Roy Lewis 06:06:46 09/18/08 (3)
Thank you for the response. When you state that the exact size of the throat is extremely important, how " exact " is exact.

If the cabinet is modified for aesthetic reasons or differant drivers ( as you mentioned in previous threads ), how much leeway do you have in throat area before the function is compromised ? Besides the horn mouth mentioned in your answer , are there any formulas for the " throat, main volume, to horn entrance " in order to find the optimum throat area ? How did you derive it for your coaxial, or was it trial and error ? Is the horn length important ?

Hope you can answer

Roy
- RE: Dragonfly - Robert Bastani 23:14:55 09/23/08 (2)
  Hello Roy,
  
  i found the dimensions by trial and error (i use tuneable cabinets for the design, by this i only need to build a few cabinets). DF is a mixture between bass reflex and horn. The volume of cabinet and tuning frequency of the horn is similar to a bass reflex- design. When you plan to adapt this for another driver you need to find specific dimensions for this cabinet- part for the new driver. The horn which follows also works for other drivers of the same size when the systems resonance of the "reflex" partition is similar to the DF values. The DF cabinet uses floor and rear- wall to simulate a big sized hornmouth - the mass of air which is moved by the driver thru the horn and the virtual opening increases a lot and lowers the resonance of the system, so the basses are much more fundamental than other compact horn designs offer. The aim of the DF cabinet design was to get a slim speaker offering deep AND dynamic bass response and also a simple cabinet building for diy. All the factors (driver parameters, reflex partition, dimension of the horn and the virtual mouth formed by the room)take influence, each parameter interacts with all others - highly complexed. For your individual design adapting other drivers of the same size the first steps should be finding the right volume and the right tuning frequency (horn lenght and entry diameter), when this is right you may use the contour of DF to get a satisfying result.
  
  Regards
  Robert Bastani
  - http://www.bastanis.com (Open in New Window)
  - RE: Dragonfly - Roy Lewis 03:50:12 09/24/08 (1)
    Hello Robert
    
    Thank you again for your reply
    
    Roy
    - RE: Dragonfly - graylion 09:40:36 12/05/09 (0)
      Hi Robert
      
      would it be possible to combine the dragonfly with the ultratweeter?
      
      cheers,
      
      Bernhard (yes the one in Dublin ;)

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