Please explain this crossover...???

[gcm908]

Can someone please walk me through this crossover? Thanks GCM

[Zen Mod]

woof have 12db/oct

tweet have 24db/oct with few resistors for level padding and 0,5 UF for augmenting highest frequencies driver can play

ya need more ?

[gcm908]

Thanks Zen Mod...

How would the 0,5 uf augment the hf? raise or lower? and

if the hf is 24db, why would it be wired in reverse? -/+

Any way of knowing the xo frequency without building it?

Thanks again.

[Zen Mod]

Originally posted by gcm908
Thanks Zen Mod...

How would the 0,5 uf augment the hf? raise or lower? and

if the hf is 24db, why would it be wired in reverse? -/+

Any way of knowing the xo frequency without building it?

Thanks again.

0,5UF is for raising from some frequencies ...probably driver (as all drivers) have somewhat falling characteristic

12db/oct twist polarity 180 grades
24db/oct twist polarity 360 grades.......so reversing polarity equals twisting of polarity in low and high legs

but-without knowing exact placement of drivers (horizontal offset-how drivers are mounted in vertical plane) it's hard to have any further comment on phase characteristic of sayed combination........

I can give you xo frequency tomorrow,just because exactly this formula is always slipping form mu mind ,and I always must check in Loudsp Cookbook......

[v-bro]

This filter is specifically tweaked for a certain driver combination. For knowing xo you'd at least need to know the impedance of the drivers.

The switched polarity is done in order to restore the phase. Phase behavior difference between the drivers and different filter slopes can sometimes make it necessary to change the polarity of a driver in order to improve the phase behavior of the combination.

The 5uF cap functions as a 6db/oct. filter(at a higher xo-freq.) parallel to the 24db/oct. filter in order to improve highest frequencies.

[v-bro]

Whoops, I ment the 0.5uF cap....

[Zen Mod]

Originally posted by v-bro
For knowing xo you'd at least need to know the impedance of the drivers.

incorrect

resonant frequency of circuit is dependant solely of L and C parts ;

but-their values depends of drivers impedance,so -L is doubled and C is halved for 8 ohms,comparing to 4 ohms dedicated xover

[hermanv]

I did a quick simulation.

The simulator is free at the Linear Technology site.

[v-bro]

Originally posted by Zen Mod



incorrect

resonant frequency of circuit is dependant solely of L and C parts ;

but-their values depends of drivers impedance,so -L is doubled and C is halved for 8 ohms,comparing to 4 ohms dedicated xover

Whoops again, you're right...("I knew that....." )

Great input on that linear technology site Hermanv!

[hermanv]

Originally posted by v-bro
Great input on that linear technology site Hermanv!

You can build driver models (at least the RLC parts) and then save them as if they were a component. The simulator has no driver library and doesn't know anything about acoustic driver behavior or mechanical Q.

For the chart I posted I just put in 6 Ohms DC for both drivers. I didn't sum the two outputs, but you can by adding an algebraic equation to the plot window.

There's a LTC users group on Yahoo that has sim files for some common vacuum tubes and other useful stuff.....

The FFT functions are also very useful for simulating amps, be sure to use a large number of samples and very small step sizes for performance better than 40 or 50 dB. (just right click in the plot window)