Klipsch loudspeaker corner


With Respect

Paul W. Klipsch

March 9, 1904 - May 5, 2002

** PWK's loudspeakers **
The loudspeakers Mr. Klipsch designed are among the finest ever made. His horn-loaded woofers in particular are first class. We don't mess with them! No changes of any kind should be made. Don't try to put a better woofer driver in them. Don't stuff the back chamber with damping material or do any other kind of changes. You will be taking a step backwards!

However, some of these speakers have been in use for as long a 50 years and the state of the art has moved on making the high end ready for some improvements. The midrange (Squawker) horn and crossover networks in particular could use some improvements. To a lesser degree, the tweeter can also be improved. The upgrades we offer will make your Klipsch heritage speaker second to none!

Unfortunatly the filter design skills at Klipsch have not improved over the years and it would be a very expensive mistake to purchase one of the official Klipsch "upgrades". The latest invocation of the Klipschorn crossover is very poor. It is called the AK-4. Here is the actual measurements made on an AK-4. Notice the extremely rough midrage (squawker) and tweeter filter responses. Compare this plot with any of the plots of the upgrades we offer. The difference will be quite obvious.

** Crossover network overview **
All our networks, except the Universal , are divided into two separate modules to allow flexibility. Each module is a constant-impedance crossover formed by a high-pass and a low-pass filter of the same frequency. The high frequency output of the lower crossover is fed to the input of the higher frequency crossover. The diagram below shows the ES500T crossover connected to the ES5800 crossover. Any of the low frequency crossovers may be used in place of the 500 Hz network shown including one of the AP12 series 12 dB / octave networks. The Universal network 6000 Hz section can even be used in place of the ES5800 by connecting to its Bi-Amp input. This lets you upgrade your speakers slowly, one module at a time!
** Filter slopes **
The "slope" of a filter is a measure of how fast the frequency range outside the range a filter is to pass gets rejected. Most crossover networks will increase the rejection at a rate of 6, 12 or 18 dB / octave. An "octave" is each time the frequency doubles. We refer to this type of filter as the "gentle slope" type. Our AP12-600 is an example of a 12 dB / octave filter.

Our Extreme-slope filters reject at a rate beyond 120 dB / octave until they reach about 25 dB where the rejection levels off. The faster slopes yield a noticeably better stereo image.

The computer plots below compare the woofer filters of the AP12-600 and the ES600 extreme-slope networks.

** Network selection guide **
Speaker / Squawker horn Good Better - step up Best (Extreme-slope)
Belle / stock K500 Universal AP12-500+ES5800 ES500T+ES5800
Belle / Trachorn 400 Universal AP12-500+ES5800 ES500T+ES5800
Belle / Altec 811b -None- AP12-700+ES5800 ES700T+ES5800
LaScala / stock K400 Universal AP12-500+ES4000 ES500T+ES4000
LaScala / Altec 511b Universal AP12-500+ES5800 ES500T+ES5800
LaScala / Altec 811b -None- AP12-700+ES5800 ES700T+ES5800
LaScala / Trachorn 400 Universal AP12-500+ES5800 ES500T+ES5800
Klipschorn / stock K400 Universal AP12-350+ES5800 ES400T+ES5800
Klipschorn / Trachorn 400 Universal AP12-350+ES5800 ES400T+ES5800
Klipschorn / Altec 511b Universal AP12-350+ES5800 ES400T+ES5800
(stock drivers is assumed - K33, K55, K77)

Notes:

* The Universal network "Bi-Amp" input may be used in place of the ES5800 together with any of the AP12 series networks. That is, the woofer filter of the Universal can be replaced by the recommended AP12 sereis network. This is only a good option for those who already have the Universal netork and want to move up the the Extreme-slope (ES) networks slowly.

* Two-way operation can be done with any "ES" or "AP12" network within the limits of the squawker horn and driver.

* If your Klipschorn has the stock AK-3 network, you can use the AP12-AK3 in place of the AP12-350 and utilize the components already inside the woofer compartment.

* If you have one of the newer speakers with the 4000 Hz crossover you should not pick a network that will move the crossover up to 5800 or 6000 Hz unless you also replace the stock K400 squawker horn. The 4000 Hz crossover frequency is to move away from the K400 horn as low as possible. It's NOT a very good horn. Even a correctly designed crossover at 5800 Hz can't compensate for a horn that sounds bad between 4000 and 6000 Hz. It's better to route that sound to the tweeter instead. Older LaScalas require major wood cutting to install a better horn. Most people are not willing to do that. This is why I advocate the ES4000 and tweeter upgrade for these speakers. This actually applies to any speaker owner who must retain the stock K400 horn for whatever reason. The only complication is that the stock K77 or K77M tweeter can not safely god down to 4000 Hz. The K77F (of the new speakers) will however.

** The ALK Engineering warranty **
Any crossover network or horn upgrade you buy from ALK Engineering will be worth the money you spent for it, or within the firt two weeks, I will buy it back so long as it is unmidified and undamaged. In the case of the Trachorn, you don't even have to install it. Just set it on top of your speaker, move the squawker driver and listen! All you will lose is shipping cost if you don't like it.
A word about on-line audio forums

These on-line audio forums exist for the finantial enrichment of their owners. This is certainly the case with the Klipsch company forums. The long list of sales banners at the bottom of the AudioKarma forms is certainly evidence of THEIR agenda if not outright proof. Unless you pay them, a "vendor" such as myself can not mention his products without being accused of abusing the forum. In spite of care not to directly tout my products I have been repeatedly accused of it. When owners of Klipsch Heritage speakers post asking questions like why do my speakers sound great but give them headaches after listening for a while, I feel obligated to point out the reason, the K400 squawker horn! When an owner posts asking for ideas on how to upgrade his speakers I have two choices. I can to point to the items that I know need improvement and get accused of abusing the forms or I can say nothing waiting for other to suggest my products and later be asked why I didn't help! I considered sponsoring one of the forums but realized that doing so would not pay off. I do no paid advertising at all but rather depend on word-of-mouth to sell my upgrades. This is the best advertising there is and it's FREE! This is one reason I can offer my upgrades at reasonable prices. Paid advertising is expensive! After years of fighting the unavoidable I have concluded that I should never again join any of these forums and I never will.

Al Klappenberger

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