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Midrange horn and tweeter upgrades

The biggest improvement in the sound quality of the Klipsch Heritage series is to replace the stock K400 or K500 midrange "squawker" horn with a better one. At this time the choices are very limited. I know of only two good options. The first, if you are up to some woodworking, is the Eliptrac 400 2-inch elliptic wood tractrix. This horn will require a 2-inch driver or an adaptor to continue using the Klipsch K55 driver.

One option:

Enlarge The picture at the left shows the finished Eliptrac 400 horn kit installed in a frame for the Klipschorn. The frame must be constructed to allow the tweeter to be mounted alongside the horn. The frame is NOT currently available. You need to build it. Here's the plans: Enlarge

The horn kit comes like this:

Here are the actual assembly instructions for the kit.

The kit is available from Dave Harris.

Email Dave at: fastlaneaudio@aol.com for pricing and to order.

Another option:

The venerable old Altec 811b and 511b "Voice of the Theater" horns are no longer made but can be found on eBay. These are 1-inch horns and will require an inexpensive adaptor to use the Klipsch K55V squawker driver. They are MUCH better sounding horns than the stock horn!

About the crossovers with the VOT horns: These horns were designed to be crossed over a bit higher than they will need to be when used in Klipsch speakers. Both the 811b and 511b will operate nicely below their rated lower limit but should be used with extreme slope networks. The ES400 is recommended for use with the 511b in the Klipschorn. The 811b should be used with the ES700 crossover.

About drivers with the VOT horns: These horns have a 1-Inch diameter throat. The only drivers that will operate down to 400 Hz in the Klipschorn (511b) are the Klipsch K55, the A55G and the JBL 2470 with its original phenolic diaphragm. In the Belle Klipsch or LaScala (811b), the JBL 2426 can be used.

Here's a few examples of "VOT" horns installed in Klipsch speakers.

511B 511B 811B


Tweeter upgrades

The stock K77 tweeter should be the last item on your upgrade list. It is not a bad tweeter but can be easily damaged. There are better tweeters available. Here are several to consider.


A new tweeter to directly replace the K77.

Introducing the Eliptrac HF

The Eliptrac tweeters will directly replace the K77 in the stock top compartment of the Klipschhorn, Belle Klipsch or La Scala. It can fit neatly between the squawker horn and the top providing a flush mount with the front baffle no matter if the old tweeter was directly mounted or with "Z-brackets". Unlike other direct replacements using the APT50 driver it will have high sensitivity and good transient response equal to the K77 and with good frequency response on and off axis!

Transient response: One method of evaluating transient response is to apply a short burst of pure tone into a tweeter and look at what comes out with an instrument microphone and oscilloscope. Does the tone stop when the applied burst stops or does it continue to ring like a bell after its struck. The picture at the left shows the tone burst of a stock K77 with the details identified, Click the picture for tone burst tests on six popular tweeters and drivers.

The APT50 rings like a Christmas bell! Any tweeter you may have that uses the APT50 driver should be replaced with either the stock K77 or a new tweeter using the B&C DE120 or DE110!


The Eliptrac HF horn is designed to allow the driver to mount flush to the horn. There is no air gap between the driver and the horn throat. There is no need for a "kludge" screw-on adaptor. With the DE110 or DE120 driver the entire tweeter is small enough to replace the K77 with no modifications to the speaker.

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Eliptrac HF horn polar directivity:

Horizontally is the way to mount it!

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When mounted vertically:

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Mounting dimensions:

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