Bought a pair of Straight 8's

[debk]

I have been studying the crossover for the ST324 on the climax page.  While I understand the the straight 8 version 3 crossover and can calculate values fairly close to the given values.  I am having trouble understanding the  Climax high pass filter.  The Climax ST324 crossover seems to have a crossover frequency of 20KHz.  The explanation given on the Climax page if I follow it correctly is that the normal roll off of the ST324 combined with the 1st order 20KHz high pass filter will give a flat response for the tweeter that aproximates a 4th order high  pass filter with a cut off around 3.15KHz

Am i close or have i missed something?
Thanks
Deb

 

[Doc B]

Yup, you got it right. Imagine that the stock treble response above 3kHz is more or less a first order slope rolling off from 4kHz to about 15kHz. The trick is that the sensitivity of the driver is so much higher than the bass array that the 20kHz 1st order 'bass' roll off actually flattens the falling treble response of the driver and drops the output sensitivity to the same level as the woofers. Below 3 or 4kHz the bass rolloff of the tweeter combines with that first order slope from the cap and makes that nice steep crossover point.

 

[debk]

Thanks that helped. I have been trying to wrap my head around all afternoon

Deb

 

[Paul Joppa]

For what it's worth, we did a lot of measurements that time, and the match with a 4th order Linkwitz/Riley at 3.15kHz is really remarkable in the crossover region - +/- 10-15 degrees of phase, for one thing, which startled the heck out of me when we made the measurement. This tracks through the full 360 degree phase rotation.