My new type A crossover

[Al Klappenberger]

Hi Guys,

Sorry I'm late! I had not been following this thread.

To the question about the crossover at 400 Hz.....

The reason you can use the first order crossover, like in the A, AA and my

network, with virtually any combination of horns is that it has an extremely

slow rolloff and is so dependent on the load impedance to determine what its

actual crossover frequency is that you can virtually let the horns

themselves determine the crossover. PWK used the same AA network in the

Khorn, LaScala and Belle Klipsch for years. The Belle has a 500 Hz horn and

the others use a 400 Hz horn. If you run tests on these horns you will see

that they will perform below and above their specked ranges. This means lots

of overlap. The 400 Hz crossover in my network measures to be 400 Hz with a

5 Ohm load and the squawker taps at 5-2. If you change any of these the

measured crossover frequency will move. This is why you don't have to worry

about the combination of horns you are using with a first order crossover.

If you go to a second order (12 dB / octave), the network starts to have a

more pronounced effect though.

I am currently experimenting with the opposite extreme, that is, infinite-

slope networks that have slopes on the order of 120 dB / octave. This is

equivalent to N=22 (twenty second order). This allows virtually no overlap

at all. In this case, the network nails the crossover and the horns better

keep up! The advantages are that there is no energy on either side of the

crossover to cause interference between drivers, so that don't have to blend

and there is no need for time alignment. It is my contention that you can't

hear delay differences between drivers anyhow. All you hear the in

interaction between them when they are both sounding together. Another

advantage is that you can extend a squawker driver safely below its rated

low frequency limit since energy from lower frequencies can not reach the

driver. Drivers are often rated for a particular low frequency limit with a

12 dB per octave slope in mind. I am running an Altec 811 horn and JBL

driver crossed over to my Belle woofer at 700Hz that is supposed to be

crossed at 800 Hz. It sounds fine. I have not measured the impedance of the

JBL driver on this horn to see that it's being loaded properly that low as

yet but plan to do it very soon since I plan to convert my other two Belles

from 511 horns to 811s. I'm going to do this becasue the 811 fits in the

Bell very neatly. The 511 sticks out the back and leaves no room for the

tweeter!

Al K.

[Al Klappenberger]

Hi Guys,

I just did the impedance test on my two horn / driver combinations. I find

it very hard to believe, but the Altec 811B and JBL 2426h combination seems

to provide a smoother impedance between 500 and 1000 Hz than the combination

of the 2426h and the Altec 511B horn! The impedance swings from 4 to over 15

Ohms in that reigon on both. The 811b definitly seems smoother above 750

where I will be using it. I also find that the impedance appears to be

capacitive down there too! That I definitly didn't expect.

I think I will be selling a couple Altec 511B horns before too long! 8^)

Al K.

[Mike Lindsey]

Al,

Do you have to do anything different with your crossovers to get them to recognize the 700hz crossover on the 811B (versus the 500hz on the 511B)? Are you running tweeters with your 811B's? If not, what is the freq response of the 811B?

Thanks,

Mike

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My Music Systems

[Al Klappenberger]

Mike,

Click on the little house icon below one of my posts. This will expalin what I am doing on an experimental basis. The network I am going to build for you is nothing like the one I am expeimenting with. I am crossing over at 700Hz woofer to squawker and 7500 Hz squawker to tweeter. The experimental networks have skirts like the sides of a barn! I am using different drivers. I am also about to change out the tweeters for T-35 to Beyma CP25.

My type "A" network (the one I build for customers) is 6 db / octave and should work at 500 Hz easily. Pushing it to 700 might be a stretch though!

AL K.

[jweed]

I'm using Altec 805 tar filled horns with 288B drivers and ALK crossovers on my K-horns and they work fantastic. I'm also using JBL 2404H baby cheek tweets and love how they sound.

K-horns have never sounded better.