Hi
Is Possible Some Body Design Circuit for me ?

I need Variable Band Pass Filter

HPF : From 25 To 500 HZ
Lpf : From 100 To 500 HZ

I need It @ 24 DB /Octav Slope .

I dont know How can be Make it as variable Cutoff Selector..
.

Regards,
Alireza

 

A variable frequency 24db/octave filter needs four pots to change at the same time.
The frequencies are so close together that the highpass will affect the output of the lowpass and the lowpass will affect the output of the highpass.

 

A variable frequency 24db/octave filter needs four pots to change at the same time.
The frequencies are so close together that the highpass will affect the output of the lowpass and the lowpass will affect the output of the highpass.

dear Audioguru
i know it need to change capacitor for 4 one order Linkwitz Circuit .
but i want to know how can i do this :d ?

i want use this Filter on different propose

for example for Subwoofer I use it on Band Pass : 30HZ to 120 HZ
for Midbassess : 100 to 500 Hz
and ...

for Full Range Speaker LPF filter will be Off .

This is Like Car Amplifire .

Let me show you Filter Board of Sound Stream Tra 680.4 Class A/b amplifier
http://img.majidonline.com/show/202425/BandpassFilter.png

It Selectable Hi/Low Pass Filter With Variable Frequency Selector

I Interested To create one of Them

Please Guidance me

Sorry for my bad English

Regards ,
Alireza

 

A sub-woofer uses a lowpass filter, not a bandpass filter.

A Linkwitz-Riley 4th-order bandpass filter will have 100Hz at -6dB, 225Hz at -1dB and 500Hz at -6dB. Why bother with a mid-bass speaker? A full-range speaker can easily go down to 100Hz. Then use a 4th-order highpass filter at 100Hz for it.

 

To Prevent High Excursion and Extra Woofer Cone Excursion
use SubSonic/InfraSonic Filter : HighPass Filter From 15 - 40 HZ [Frequency Is Selectable based on Enclosure Tune Frequency]
It's very important for Ported Enclosure

Extra Excursion May be Damage Cone , Spider , Woofer , ....
It Help Amplifire To Oprate On Higher and hearable Frequency
and prevent amplifier to Waste Power
Clear Sound
,.....

So , We Need Band Pass Filter For Woofer to prevent Getting damage To subwoofer and helping amplifier Performance

 

OK, your sub-woofer is too small to produce 20Hz so use a highpass filter which is part of a bandpass filter to cut deep bass frequencies.