Hi,
do you want an active crossover to integrate the sub with the mains?
Then you need a Low Pass Filter on the sub and a matching High Pass acoustic Filter on the mains.
If you use the natural rolloff of the mains which are probably 18db/octave but with a Q that is not Butterworth, then you need an additional 6db/octave to match the LPF.
If you do not know the Q engineered into the mains then moving the crossover point to at least an octave and preferably two octaves above the roll off allows an electrical HPF to nearly match the LPF.
So moving crossover to above 160Hz will allow either Butterworth or Linkwitz Reilly to be bulit up with active electrical filters. I think you stand a better chance of getting sensible integration of sub to mains by adopting this strategy.
An advantage of the higher frequency and steeper electrical HPF on the mains is a substantial reduction of cone displacement on almost all music. The effect is better performance from the mains at all usual SPL levels (not just maximum SPL levels).
Has anyone one else got an alternative suggestion?
do you want an active crossover to integrate the sub with the mains?
Then you need a Low Pass Filter on the sub and a matching High Pass acoustic Filter on the mains.
If you use the natural rolloff of the mains which are probably 18db/octave but with a Q that is not Butterworth, then you need an additional 6db/octave to match the LPF.
If you do not know the Q engineered into the mains then moving the crossover point to at least an octave and preferably two octaves above the roll off allows an electrical HPF to nearly match the LPF.
So moving crossover to above 160Hz will allow either Butterworth or Linkwitz Reilly to be bulit up with active electrical filters. I think you stand a better chance of getting sensible integration of sub to mains by adopting this strategy.
An advantage of the higher frequency and steeper electrical HPF on the mains is a substantial reduction of cone displacement on almost all music. The effect is better performance from the mains at all usual SPL levels (not just maximum SPL levels).
Has anyone one else got an alternative suggestion?
AndrewT said:
18 dB/octave? Sealed boxes roll off at 12 dB/oct, vented at 24 dB/oct. Infinite baffles roll off at 6 dB/oct at the baffle frequency, and another 12 dB/oct below speaker resonance, to make 18 dB/oct. You need to know what the mains are before playing with filters.
And crossing over at 160 Hz will let the listener localize the subwoofers in the room, not what you want.
Francois.
You need an SPL meter, some test tones and preferably an RTA program to blend in a sub. What most people are saying here is that mating a sub to a woofer is exactly the same as mating a woofer to a midrange. You need a proper crossover (phase, XO frequency, slopes) to do it successfully. You need to end up with an ideal Butterworth or Linkwitz-Riley transfer function, or it will never be quite right. I'd also suggest you'll need some EQ, because weird things happen to bass in rooms.
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