Hi,
I want to operate a sub in the lowest octave ie from HP 25Hz to LP 50Hz. The bandwidth is so small, so I was thinking that it may need a steeper slope filter otherwise LP may have an effect on HP and vice versa, and to avoid it steeper slopes may be needed. Can you please help me select the filter slopes? Should I use 24dB/octave?
Thanks and Regards,
WA
I want to operate a sub in the lowest octave ie from HP 25Hz to LP 50Hz. The bandwidth is so small, so I was thinking that it may need a steeper slope filter otherwise LP may have an effect on HP and vice versa, and to avoid it steeper slopes may be needed. Can you please help me select the filter slopes? Should I use 24dB/octave?
Thanks and Regards,
WA
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Do you need a HP 25Hz filter ? Most subs I've run (at home, not PA) have not needed a highpass, even ported ones.
Might be worth looking at bandpass subs for such a small bandwidth.
Rob.
Might be worth looking at bandpass subs for such a small bandwidth.
Rob.
For such a limited bandwidth, BW24HP would be the usual go-to selection to minimize filter effect on response around the crossover point.
The LP really depends on the acoustic response, without knowing the design and response of the sub and upper box, selecting filter slopes is a shot in the dark.
Steep slopes cause a fairly extreme ring in the impulse response and IMO are almost always best avoided.
The question is why you feel a need for the steep low pass to your sub at 50hz?……….knowing your in room F3 of your existing system would be imperative to developing a supplemental LF solution.
How you approach that single bottom octave will dictate if a subsonic filter is needed. Typically a sealed system would be built where the system model indicates where excursion of the driver is limited by input power. In these instances more money would be invested in the driver and amplification and less floor space would be needed for the enclosure. Driver excursion is therefore limited by the relationship of the compliance of the enclosure and system input. Done properly, as with a Linkwitz transform filter system output results in an in room f6 somewhere in the teens. My sealed studio subs that supplement dipole woofers that extend to 50hz with an overall in room f3 of 18hz. They are 15” sealed systems with high xmax drivers (24mm) and are powered by 1kw each. Because the enclosures are small (high Q), they cannot exceed xmax with the given system power.
Now remember your passband as a representation of an octave……a sealed system will yield 12db from 50 to 25hz anechoic…..but in room the loss is far less…..more likely 6db…..and could be cut to just 3db per octave using dual enclosures and proper corner loading.
I can’t see any path where a ported system would make any sense here given the output bandwidth of the ports in relation to the driver……tuned low and it’s all port output…..tuned high and the ports are irrelevant.