(OPTIONAL) Crossover mods for the new BEC tweeter

[Al Klappenberger]

Guys,

The new BEC tweeter, besides being a direct upgrade for the K77 tweeter withOUT any network changes offers a chance to move the crossover frequency down lower than 6000Hz. The K77 can't be counted on to go that low or to handle any power down there if it could! The horn itself is a defraction horn and will give you better dispersion BELOW 6000 Hz if it is mounted vertically. Here is a computer simulation of the stock "A" network modified by changing the tweeter capacitor (2 uF) to 4 uf and adding a 500 uHy (.5 mHy) inductor in series with the squawker. I believe that lowering the crossover is an improvement becasue it takes you away from the less-than-wonderfull K400 and K500 squawker horns sooner. If you want to stay with that horn, lowering the crossover will help.

Here is the computer simulation of the modified "A" network. It looks like a typical Klipsch network. It's impedance rises to roughly 30 Ohms in the middle of the squawkers range. The actual crossover looks like about 5150 Hz. With a 1st order filter like this, both drivers have a major overlap. I don't like that, but a lot of people like it. It is a tolerable situation at low listening levels. This arangement yields about 6.2 dB rejection of the 9 KHz "glitch" found in some early K55V squawker drivers. The lower crossover improves this rejection.

I sugest that the values be changed to 4.7 uF and .56 mHy to take the crossover down to 4500 Hz if you have't done the mod yet. This is a very small change and I wouldn't bother making the change if you have already made the modification.

Al K.

[Daddy Dee]

Al,

I was wondering what it would take to modify your universal Type A replacement crossover for this 4500hz frequency.

[Al Klappenberger]

Dee,

Here's the next stage. This one is a higher order version of the stock "A" network mod. It provides a crossover at 4500 Hz and yields about 12 dB rejection to the 9 KHz "glitch". The impedance still rises to 30 Ohms in the midrange and the squawker level is fixed at the 4-0 setting on the transformer. The modifications need to bring my Universal "ALK" network down to 4500 is next..

AL K.

[Al Klappenberger]

Guys,

Here's the Universal "ALK" modified to bring the squawker / tweeter crossover down to about 4600 Hz. The 9 KHz glitch is about 11 dB down. The impedance is virtually a constant 8 Ohms.

AL K.

[J.4knee]

Al,

Do you see any real benefit to mod the crossover down to 4.5 KHZ'ish when using a horn such as the Altec 511B. I am using Bob's prototype tweeters with your Universal replacements and a K55 mounted to a 511B and it seems to be pretty seamless.

[Deang]

Al likes 4500 because he doesn't like the K-400.

Bob likes 4500 because he likes the sound of his tweeter.

We do all realize we're only talking a measly 1500 cycles in a first order application? Seriously, is it even worth the trouble? If you low pass the squawker on a Type A or AA with .40mH you're at 5725Hz and don't have to mess with the tweeter filter unless you want to.

What about all those folks with drivers that really go out to 6000Hz -- what real benefit are they getting out of this drop in the crossover point?

Right now all of our networks have at least one thing in common -- PK's crossover points -- four octaves through the middle.

Am I just being hard headed again?

[Al Klappenberger]

J.4,

If you are using the Altec horn I would NOT move the crossover. Like Dean says, I think the only reason to do it is to get off the K400 ASAP!

Dean,

Moving the crossover from 6000 down to 4500 is only 1500Hz, but that is actually 25 percent. This is more significant than you might think.

Al K.

[J.4knee]

Thanks Al/Dean

[SilverSport]

It's like watching them build the bomb...I love this...

Bill

[Duke Spinner]

not having Heard the combo ......

1) to get away from the K55 at 4500, and have less overlap would be great...

2) on the other hand, one driver reproducing the midrange, should be a plus

the detriment is the klipsch horn

3) if i was using a 511, i would go 2 way, w/ the 902, or 908 driver, i can't hear above 15k, anyways

[Deang]

Whether constant impedance or Type A -- my networks incorporate a simple 1st order low pass on the squawker at 6kHz -- and it sounds great. The stock horns only sound rough if you don't roll them off at all.

[LarryC]

Moving the crossover from 6000 down to 4500 is only 1500Hz, but that is actually 25 percent. This is more significant than you might think.

Al K.

That drop is an interval of a fourth, almost half an octave, which I agree is significant. Those are very high notes -- 6000 is approximately the highest G on the piano, and 4600 is approximately the highest D (3 octaves higher than middle C). If you play those notes on the piano, you will hear how really, really high the tweeter's lowest notes are!

Frequencies of 4500 or 6000 and above are almost entirely overtone territory, well above the fundamental frequencies of the highest notes of even the piccolo, harp, or xylophone. The few pitched instruments that go that high include the violin (especially high harmonics), pipe organ, celesta, glockenspiel, and of course the piano. And non-pitched instruments (no definite frequency) like the cymbal and triangle undoubtedly have overtones going well above 6K.

The tweeter sometimes doesn't sound much like music (though Bob Crites's may be better at it), but very much present the "tingle" and life of practically all instruments, even ones in the bass. A must for triangles and cymbals, again IMO.

Larry

[Deang]

Informative -- thanks Larry.

It sounds like a lot, but because of the nature of a first order filter it doesn't really amount to a hill of beans from an acoustical perspective. This is one of the problems with math and plots -- they don't make any sound!

You're an AK-4 user -- have you made it back over to Gary's to hear his Klipschorns with the new networks?

[LarryC]

Dean, you're right in that a fourth sounds a lot less obvious and significant way up there than it does around, say, mid-range crossover points (IMO). I'll send you an opinion after I give Gary's a thorough listen.

[Daddy Dee]

Moving the crossover from 6000 down to 4500 is only 1500Hz, but that is actually 25 percent. This is more significant than you might think.

Al K.

That drop is an interval of a fourth, almost half an octave, which I agree is significant. Those are very high notes -- 6000 is approximately the highest G on the piano, and 4600 is approximately the highest D (3 octaves higher than middle C). If you play those notes on the piano, you will hear how really, really high the tweeter's lowest notes are!

Frequencies of 4500 or 6000 and above are almost entirely overtone territory, well above the fundamental frequencies of the highest notes of even the piccolo, harp, or xylophone. The few pitched instruments that go that high include the violin (especially high harmonics), pipe organ, celesta, glockenspiel, and of course the piano. And non-pitched instruments (no definite frequency) like the cymbal and triangle undoubtedly have overtones going well above 6K.

The tweeter sometimes doesn't sound much like music (though Bob Crites's may be better at it), but very much present the "tingle" and life of practically all instruments, even ones in the bass. A must for triangles and cymbals, again IMO.

Larry

Larry,

Thanks for this most interesting post. I'm looking forward to hearing about what you hear in the new tweeter.

[BiggerIsBetter]

I think it is mixing apples and oranges a bit when coming 4500 to 6000 between a ESN and a first order. I agree that with a 1st order all the crossover point are ish anyway, the changes in question are just a few dB here and there on a 1st order and I expect there are driver and room variation great than the changes being discussed for a first order.

[Deang]

Thank you.