Hi,
I am not that familiar with x-over filters from Subwoofer, commercial or DIY design. Questions please:
1. What kind of filters do high-quality commercial subwoofer use in their sub, e.g.BW 12db(-3dB at F3) or something else if so what? Please explain.
2. If I build a subwoofer from scratch and use an external DSP filter what kind of filter should I set if my main speakers are sealed? DO I have to phase invert if necessary, how to make sure the phase is correct? BTW I have a measuring instrument, microphone and REW s/w. Please explain.
This would help me to integrate my Sub with the sealed Main speakers.
Thanks to those who can answer my questions?
I am not that familiar with x-over filters from Subwoofer, commercial or DIY design. Questions please:
1. What kind of filters do high-quality commercial subwoofer use in their sub, e.g.BW 12db(-3dB at F3) or something else if so what? Please explain.
2. If I build a subwoofer from scratch and use an external DSP filter what kind of filter should I set if my main speakers are sealed? DO I have to phase invert if necessary, how to make sure the phase is correct? BTW I have a measuring instrument, microphone and REW s/w. Please explain.
This would help me to integrate my Sub with the sealed Main speakers.
Thanks to those who can answer my questions?
Last edited:
Lucky you got sealed speakers, because you have to determine the resonance and the Q-factor. This is easily done with an impedance sweep and REW can calculate the resulting Q.
For such a sweep you need a soundcard with stereo line inputs and a precision resistor of say 47 ohms.
Alternately you can run a frequency sweep with your mike very close (5mm) to the diaphragm and compare it with a 2nd order highpass.
Now when you know these 2 data, you can select a second order highpass with the same resonance, the Q factors multiplied should be 0.5
Example you measured 75Hz and Q=0.85, the filter for the mains would be 75Hz and Q=0.588.
You now have a Linkwitz-Riley 4th order high-pass.
The sub doesn't need measurements just insert a 4th order L-R lowpass 75Hz
For such a sweep you need a soundcard with stereo line inputs and a precision resistor of say 47 ohms.
Alternately you can run a frequency sweep with your mike very close (5mm) to the diaphragm and compare it with a 2nd order highpass.
Now when you know these 2 data, you can select a second order highpass with the same resonance, the Q factors multiplied should be 0.5
Example you measured 75Hz and Q=0.85, the filter for the mains would be 75Hz and Q=0.588.
You now have a Linkwitz-Riley 4th order high-pass.
The sub doesn't need measurements just insert a 4th order L-R lowpass 75Hz