10-28-12: Doggiehowser writes
Is this for a home theater or a hifi system?
>It's always a bit difficult to integrate a subwoofer with main speakers. One thing I try not to do is to muck with the main speaker's crossovers. The speaker designers have put a lot of work into the speakers' internal crossovers so adding another crossover stage in front of it is going to muck it up further.
Main speakers need an electrical high-pass filter to prevent unacceptable IM distortion unless they're sealed boxes with a high cut-off frequency (80Hz is too low for drivers 8" and under) and even then you may want a steeper roll-off to work around your room's height mode that takes another pair of poles.
For reasonable integration where that's not the case the most reasonable thing is to plug any ports, replace the speakers' two high-pass poles with zeroes, and apply your desired high-pass function where a Linkwitz Transform will give you two zeroes and two poles using one op-amp, a biquad will do it in the digital domain.
A mini-dsp in the digital domain
http://www.minidsp.com/
or Linkwitz wASP (Linkwitz Transforms for both high and low-pass legs, another pair of poles in each to give you 4th order acoustic slopes, optional all-pass for the midrange, pads for a pair of notch filters) in the analog domain will do it
http://www.linkwitzlab.com/Pluto/woofer-asp.htm
You'll want to measure and neither is a plug-and-play solution.
Is this for a home theater or a hifi system?
>It's always a bit difficult to integrate a subwoofer with main speakers. One thing I try not to do is to muck with the main speaker's crossovers. The speaker designers have put a lot of work into the speakers' internal crossovers so adding another crossover stage in front of it is going to muck it up further.
Main speakers need an electrical high-pass filter to prevent unacceptable IM distortion unless they're sealed boxes with a high cut-off frequency (80Hz is too low for drivers 8" and under) and even then you may want a steeper roll-off to work around your room's height mode that takes another pair of poles.
For reasonable integration where that's not the case the most reasonable thing is to plug any ports, replace the speakers' two high-pass poles with zeroes, and apply your desired high-pass function where a Linkwitz Transform will give you two zeroes and two poles using one op-amp, a biquad will do it in the digital domain.
A mini-dsp in the digital domain
http://www.minidsp.com/
or Linkwitz wASP (Linkwitz Transforms for both high and low-pass legs, another pair of poles in each to give you 4th order acoustic slopes, optional all-pass for the midrange, pads for a pair of notch filters) in the analog domain will do it
http://www.linkwitzlab.com/Pluto/woofer-asp.htm
You'll want to measure and neither is a plug-and-play solution.
