High Efficiency Speaker Asylum

RE: optimal horn type

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angeloitacare

In Reply to: RE: optimal horn type posted by Jmmlc on May 31, 2007 at 01:06:19

bonjour Jean Michel

can you explain me why Avantgarde and others do use a >50cm diameter midrange Horn above their 95cm diameter mid-bass horn, if it does only have to cover > 500hz, and theoretically only a 20cm diameter horn would be needed ?

rds Angelo

Follow Ups:

RE: optimal horn type - Jmmlc 05:00:08 05/31/07 (3)
Hello,

There is several possible answers to that question but here the most logical:

- in order to operate the horn inside a frequency range for which the acoustical impedance of the horn is mainly resistive (and not reactive in order to avoid phase distortion) we have to use a high pass frequency an octave minimum above the acoustical cut-off frequency of the horn. This means that for a tractrix horn used above 500Hz, the acoustical cut-off should be 250Hz. If we consider a complete tractrix horn opening at 180 degrees this means a horn having a 433 millimeters diameter.

Please notice: classical empirical formulas giving relations between cut-off frequency and diameter give a minimum diameter. IMHO thet can be useful in the pro domain where a smaller volume is desired. In the hifi domain they should be avoided.

Martin Seddon in Australia and Marco Henry here in France did listening tests on horns calculated with my method and having cut-off frequency around 160Hz. There conclusion are similar: a JMLC round horn with a profile opening at 360degrees is better than a JMLC horn opening at 180 degrees.

For horns: larger is better!

Best regards from Paris.

Jean-Michel Le Cl�ac'h
- RE: Thanks Jean-Michel - ogima 07:55:17 05/31/07 (0)
  Jean -Michel,
  
  Thanks for taking the time to respond with such clear understanding of
  the subject as well as the courtesy expressed.
  
  Dan
- RE: optimal horn type - angeloitacare 05:18:54 05/31/07 (1)
  Hi Jean-Michel
  
  so this would apply also for 88cm mid-bass horn? Meens if acoustical cut-off of the horn is 125hz, the upper bass driver would have to be low pass at 250hz ?
  
  Angelo
  - RE: optimal horn type - Jmmlc 07:43:25 05/31/07 (0)
    Hello,
    
    That's right.
    
    The only exception is if you process the signal sent to the loudspeakerwith a DSP in order to obtain a linear phase signal at the mouth .
    
    Best regards from Paris,
    
    Jean-Michel Le Cl�ac'h

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