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designing and building with wood channels my creativity and challenges my mind.
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Monday, February 7, 2011

Klipsch Heresy Rebuild

Klipsch.  The name is well known among audiophiles, for it's the name of one of the greatest U.S. speaker design companies ever known.  The Company made its name on four classic speaker models  - La Scala, Heresy, Cornwall, and Klipschorn - and the signature horn-loaded tweeters and mid-range drivers used in those models. 

These four "heritage" designs made their debuts in the early 1960's, and the designs haven't changed much since.  And while Klipsch is now a mass-market company, with manufacturing operations in China, they still offer these four flagship speakers for sale to discriminating listeners.  Unlike other Klipsch-branded speakers, the Heresy, La Scala, Cornwall, and Klipschorn are made to order in Klipsch's original plant, located in Hope, Arkansas. 

The Heresy is the smallest of the four speakers, sporting a 12" woofer, a mid-range horn, and a tweeter horn.  If you want Klipsch to make you a pair of Heresies today, it'll set you back around $1,500. 

I happen to have a pair of Heresies, built some time in the 1970's.  The cabinets on my speakers were badly damaged, but the drivers and crossovers were pristine.  So I decided to re-build the cabinets and bring my Heresies into the 21st century.

The original boxes were made from 3/4" plywood, and the front and back baffles of 1/2" plywood.  inside, the front and rear baffles sat on 3/4" by 3/4" strips of plywood, stapled into the inner edges of the cabinets.  These original cabinets were dressed up with walnut veneer. 

For my new cabinets, I decided to go with 3/4" bamboo plywood.  It's a departure from the original design, but I like using bamboo plywood for several reasons.  First, bamboo plywood is a renewable material and therefore will be used more and more as time goes on.  I wanted to show that bamboo plywood can perform as well as traditional speaker cabinet materials.  Second, I wanted to show that bamboo plywood can look just as good (or better than) hardwood veneer, and has a place as a final face material for fine furniture.  Third, I had a bunch of the stuff lying around.

My boxes are built entirely of 3/4" bamboo plywood, with no veneer. 

Most speaker cabinets are made from four sheets of plywood or MDF, with mitered edges.  These miters are usually disguised by veneer.  My cabinets don't have veneer, so the miters had to be perfect. 

I cut the bamboo sheet with my circular saw, then squared up the corners and cut the miters on my table saw. 

The front and rear baffles had to fit the boxes perfectly, so after cutting them to rough size, I slowly eased up to the final dimensions, compensating for any small irregularities in the cabinets.

To make the cutouts for the drivers, I first traced out their footprints onto the back of each front baffle.  Next, I cut entry holes on my drill press, in order to fit the blade of my jigsaw into the middle of each outline.  Then I made rough cutouts with the jigsaw.  Then, using the original front baffles as a template, and a flush-trim router bit, I trimmed away the excess from each cutout, leaving me with perfect copies of the original cutouts for the drivers.

To fit the backing strips into place, I put each cabinet face down, with either the front or rear baffle dry-fit in place.  Then I placed each strip into the case, flush against both the cabinet walls and the baffle, and screwed them in place.

I glued the front baffles onto the cabinets, but left the back baffles un-glued, so they could be removed to access the crossover and drivers.  The last step is to fix foam or rubber seals to the rear strips, to make an air-tight seal around the back baffles.



  1. Hello,

    i've baught from USA a pair of K22 drivers to build bass and low medium for my system (with JBL2426h horn mounted for medium and Fostex 925 for tweeter), but i can't find any cabinet plans of the Heresy. Can you help me for volume, dimensions end bass reflex caracteristics ?
    best regards from France,

  2. Hi Totalarico..
    This may help you..
    105 watts maximum continuous (500 watts peak)
    96dB @ 1watt/1meter
    8 ohms
    K-77-M 1" (2.54cm) Phenolic diaphragm compression driver
    90°x40° Exponential Horn
    K-55-V 2" (5.08cm) Phenolic diaphragm compression driver
    80°x30° Exponential Horn
    K-22 12" (30.48cm) Fiber-composite cone
    Birch Plywood or Veneered Lumbercore
    21.4" (54.36cm) x 15.5" (39.37cm) x 13.2" (33.53cm)
    55 lbs. (24.97kg)
    Walnut, Rosewood, Teak Oil, Walnut, Oak, Cherry Lacquer, Raw, Black Birch

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