In-line xover question

A plug-in high-pass filter like you describe will roll off the bottom end of your main speakers at 6 dB per octave (it's a capacitor selected with the amplifier's input impedance and desired rolloff point in mind).

Whether or not it will help get a better blend with your subwoofers, I can't predict from here.

Are you already using some sort of high-pass filter on your main speakers?

Are your main speakers sealed or vented (makes a difference in how rapid their inherent rolloff is)?

How steep is the low-pass filter on your subwoofer?

What ballpark crossover frequency are you using?

Thanks.

Duke
dealer/manufacturer

Hello Sydneysophia,

Thanks for replying.

Okay, when doing a crossover I try to get a symmetrical slope on both sides of the crossover frequency. In my opinion, this applies to subwoofers as well.

The Velodyne HGS-10 has a second-order (12 dB per octave) variable low-pass filter. So, we'd like for your main speakers to also have a second order rolloff (12 dB per octave).

Your main speakers, being vented, have a 24 dB per octave (fourth order) rolloff below the port tuning frequency - this is inherent in the breed. If I understand correctly, your speakers are the Von Schweikert VR-4 Jr, with claimed bass extension to 23 Hz (-2 dB). Is that correct? If so... well, this gets a bit complicated because your main speakers' inherent bass rolloff is way too low to be part of the crossover to your subs, but on the other hand I think that can be changed.

I suggest stuffing the port tightly with closed-cell foam which will turn the box into a low-Q quasi-sealed enclosure. The bass will then probably (or should I say hopefully) roll off at 6 dB per octave starting somewhere above 40 Hz, transitioning to 12 dB per octave somewhere well below 40 Hz. I do not know the exact frequency that would work best for your in-line filter, but your 65 Hz filter might work just fine. [Make sure that your in-line filter is designed for the specific input impedance of your amplifier, as the frequency where it starts rolling off will be different otherwise.]

The idea is to change your bass enclosure's characteristics to give an inherent 6 dB per octave acoustic rolloff in the crossover region, and to accelerate that by using your in-line filter so that you get a net 12 dB per octave high-pass characteristic. You should be able to match this up well with your subs given their variable-frequency 12 dB per octave low-pass filter.

Just to see if this idea is in the ballpark, try the closed-cell foam with your present filter before investing in a new in-line filter. I'm guessing that you'd use a setting of around 50 to 60 Hz for the sub's low-pass filter. I would also guess that a 50 Hz in-line high-pass filter would probably be closer to ideal (along with a lower low-pass setting on your sub), but try what you have on hand first.

No guarantee that this would work of course, but it's what I'd attempt.

Duke

Thank you, Syndeysophia, and very best of luck to you. I have no experience with the NHT unit, but that might well be a more ideal solution.

Duke