First Midrange Horn

1973-1974

Chapter 8

This page is kinda lengthy but it should be readable as the photos load.

 

Here I've placed some photos of old drawings made during my first attempt at adapting a Wharfedale Super 3 tweeter to use as a midrange horn driver.  All parameters of the cone assembly had to be measured very carefully as a plaster phasing plug was to be designed to fit over the cone and very close to it.   These photos are rather large but compressed in jpg format so the file size is still somewhat small.  To see a larger view,  click on any photo.  They are readable in full size.

The intent of this page is to give the reader an appreciation of what went into my obsession with building a fully horn loaded system similar to the venerable Klipschorn.  I just HAD to understand how that thing worked.  I could have purchased midrange drivers but money wasn't as readily available back then as were the drivers; so I made do with what I had.  When the system was complete, although never cosmetically finished, a friend drove 30 miles at night for an audition.  He was silent as he listened to his favourite Beethoven, Piano Concerto No. 5.  Having a piano at home himself, he mentioned that had he not known he was listening to speakers he'd have sworn it was a real piano.  The highlight of the audition came with Beethoven's 5th symphony, second movement.  The kettledrums were nothing less that awesome.  Never before in my life had I experienced such a moment of elation.  It was quite an emotional experience.  A little over a year later, unbeknownst to me at the time, another such moment was bestowed upon me; Phoenix, Az., Jerry's Audio, May 8, 1975, when I had the prestigious honor of showing and discussing these papers with one Paul Wilbur Klipsch.  The whole story is related here.  

Anyway, here they are, with comments attached.  Enjoy.  :)

 

One of the drawings of the diaphragm assembly of the Wharfedale Super 3 tweeter. A freehand sketch of one study on the phasing plug. There is, somewhere in my notes, a much prettier drawing but it's location eludes me.

 

The original intent was to transition from a circular area to an ellipse.  However, transitioning from an ellipse to a rectangle proved to be too complicated.  I still wonder why I even considered this in the first place.  We live and learn.

 

 

A drawing showing two views of the tweeter mounted in its chamber.  The rectangle in the center of the upper drawing is the throat to which the horn is coupled.

 

A drawing of the Super 3 tweeter in which I got carried away with the watercolour.  In retrospect, I wonder how I found the time.

 

Two views of the tweeter.  These tweeters were acquired many years later just because the labels were in such good condition.  The annuli and spiders on both have to be replaced, something I have yet to do.  They were purchased sometime in the very early 1980's.

Consideration is being given to designing a midrange horn to work with these guys as getting them down to 125 Hz. should be easy.  Another and probably better alternative being considered is to use the Focal 5K013L or current equivalent as it already has a phasing plug.  All that is left is to construct the outer ring of the plug to achieve the proper throat area.  This driver's worth as a midrange, when properly loaded, has already proven itself.  Horn loading may yield altogether different results.  As I have a non-working unit available, the cone can be used as a mould for the outer part of the phasing plug.

 

 

Chapter 9

Horn Theory - Chapter Index