Low Pass Filter setting on a Subwoofer - questions?

[rjrbass]

I have just purchased my first subwoofer, and I love it. I love it so much that I will purchase one for each system, while they are still on sale.

My musical taste is classical, musicals and vocals.

Where should I set the low pass filter for use with my Klipschorns?

Now where should I set it for my LaScalas?

Finally, same question with my Cornwalls?

Thanks,

Richard

[Chris A]

IMHO-only based on your stated music preferences--I'm assuming that your sub uses a direct radiating driver and not a fully horn-loaded one, and you are not using these primarily in a HT:

Khorn crossover frequency: 40 Hz

La Scala crossover frequency: 60-90 Hz, depending on how close the the corners of your room that your La Scalas are located.

Cornwall crossover frequency: anywhere from 40 Hz-80 Hz, depending on the quality of the subwoofer's output, i.e., how much FM distortion it has relative to the Cornwall's direct-radiating bass. A very large sub might have lower FM distortion than the Cornwall's bass bin.

Rationale: Horn-loaded bass sounds better to my ears than direct radiated bass. If this isn't true for your ears (i.e., you don't mind higher FM distortion), then you can set the sub's crossover frequency just about anywhere that you like.

Remember to time-align your sub(s) relative to your speakers based on listening distance and the built-in delay of your horn-loaded speakers: the Khorn's bass bin is an additional 9.5 feet delayed than the physical distance from your listening position to your Khorns. The La Scala's bass bin is about half that delay value.

Chris

[rjrbass]

Chris, thank you for your informative reply. I will set the parameters as you indicated. I had never considered the built in delay, and moving the sub may not be an option due to the room. I don't think that I will use a sub on the Cornwall system. I appreciate the Cornwall as it is.

Thanks again - Richard

[Chris A]

I had never considered the built in delay, and moving the sub may not be an option due to the room.

Many subs have a phase control on them, and their typical use is to set that phase control to get maximum bass response at your listening position. This will not be as desirable as a delay setting that you usually find in an AV Receiver or preamp, however, it will at least set the delay of the sub(s) to a multiple of the actual delay at the crossover frequency--which is more desirable than no correction at all.

[rjrbass]

Thanks Cask05. My subwoofer does have a phase control, however I am unsure how to set it up. The manual states to set it for the most bass, which happens to be at 180 degrees. Is there a better method to set it up? My only choices are 0, 90, 180 and 270 degrees. If you have the time, I would really appreciate an understanding of what it does.

Thanks - Richard

[Chris A]

My subwoofer does have a phase control, however I am unsure how to set it up.

Simply adjust your sub's phase filter for maximum bass at your listening position(s). If you have some music or a test disk that can play the frequencies in the crossover frequency band, you can hear what you need to hear to adjust this control. Here is a chart that might help you figure out what frequencies to listen for:

I would really appreciate an understanding of what it does

The phase shift on the sub is probably an all pass filter that shifts the phase of the incoming signal by set amounts (user selectable presets in your sub's case) at the crossover frequency between the sub and the other speakers in your setup. This allows you some control over the cancellation effects of two speakers emitting at the same frequencies, but that are not in phase relative to your listening position.

If you adjust the phase filter for maximum bass at your listening position, you are in fact correcting for distance differences between your main speakers' woofers and your sub's woofer if they are not equidistant from your listening position and if the two woofers do not have the same phase response in their crossover frequency band. The phase control should have no other effects on the output of your sub.

There are a lot of things about human hearing that get involved in whether or not you can actually hear the difference between simple phase correction and digital delay filters that can correct for more than one wavelength at the crossover frequency. If the distance difference between your sub and your main speakers (relative to your listening position) is more than a wavelength at the crossover point, e.g., 28 feet at 40 Hz, then your phase filter is correcting for the "next wavelength" that comes along in order to phase align the woofers relative to your listening position. The fact that you can't hear a steady state bass signal difference is one reason why this technique works so well, but you can potentially hear a difference on impulsive transients (drums, percussion, etc.) if the phase difference is more than a wavelength.

[rjrbass]

Cask05, thanks again, now I have an understanding of what I am doing, and how the phase affects the sound. Basic physics, simple harmonic motion, waves, nodes, crests etc. and timing the waves with the phase control.

- Richard

[garyrc]

Rationale: Horn-loaded bass sounds better to my ears than direct radiated bass.

I agree with Cask... better, cleaner attack, etc.

I decided on a 40 Hz crossover for my sub (Klipsch RSW15) and my Klipschorns after a long period of experimenting. I had a choice of 40, 80, 100, etc., but 40 just sounded better, punchier, and more effortless. K-horns are pretty good down to 40, at least in the 4 rooms I've had them in. With classical and modern orchestral music 40 Hz seemed to provide a "quiet authority" .... oops, there I go sounding like a high-end reviewer!

[SWL]

40 Hz seemed to provide a "quiet authority"

I agree. I appreciate the subtle accent a sub provides in a two-channel system. However, the headroom ("quiet authority") is what I appreciate most. [Y]