where to low-pass the sub

sponger

Currently I have the mains high-passed at 80HZ. According to the manual for the receiver, this means that the sub is automatically low-passed at 80HZ. It adds that the only way to low-pass the sub independently of the speakers is to set the speakers to full range.

So, here's this comment from Chris Kyriakakis at Audyssey in regards to where the LFE should be set for a 5.1:

Chris at Audyssey wrote:

It's a filter that is applied to the content of the separate LFE track found in 5.1 content. That content is authored up to 120 Hz and so the only correct setting is 120 Hz.

So, does this mean that by setting my LFE at 80HZ I'm creating a bass "hole" for all of my 5.1 audio? I don't mind setting my mains to 120HZ and thereby setting the sub at 120HZ as well, but this is the first time I've heard of having to do this.

Any opinions welcome.

McLoki

No, your fine. Chris (or anyone that says there is only one correct setting for every speaker/Room combination) is an idiot.

Take into consideration your main speakers frequency response (in room, not on paper), your subs frequency reponse and how it sounds blending them together.

80hz is the most common - I would say 60-100 is a great starting point (most speakers will fall into that) in some circumstances though - lower or higher may be called for.

Michael

nwohlford

The highpass for the mains does not affect the LFE channel. The lowpass for the sub you mention is just for the main channel information. Some receivers allow you to set a separate lowpass of the sub which would affect the LFE channel.

McLoki

It was my understanding that the LFE track should always be unfiltered. (they (being the people encoding it) are not to put greater than 120 hz into the LFE track)

I thought the filters are only in place for proper blending of the full range speakers and subs. If your filter is does affect both the LFE channel and the crossover to the other speakers, I would still balance it for what produces the best bass in your room but not go below 60hz.

many people can localize the bass (tell where it is coming from) above 80hz so keep that in mind as you are setting your crossovers. (it may still be better than having a hole though)

kuntasensei

McLoki wrote: »

No, your fine. Chris (or anyone that says there is only one correct setting for every speaker/Room combination) is an idiot.

In fairness, you're taking that quote from Chris Kyriakakis out of context. That was meant specifically for the "LPF of LFE" control on some receivers, for which there IS only one correct setting by the very nature of digital surround - 120Hz.

People get confused when it comes to crossovers vs. the LPF of LFE control that Chris is referring to (and that the OP is taking out of context). The crossovers of your individual channels contain a high-pass and low-pass filter (because that's what a crossover is). Ideally, you want to set the crossovers for the individual channels for the best blend for your room. Then, on some receivers (usually THX labeled), you also have a low-pass filter that operates just on the LFE channel, not the subwoofer output as a whole. The only reason this control exists is to maintain compatibility with THX-spec'd subwoofers that are designed to roll off above 80Hz. This control does NOT affect the bass management from the other channels.

However, the vast majority of subwoofers are not designed that way. And moreover, the LFE channel in digital surround tracks is brickwall filtered at 120Hz by its very nature (which is why it's the ".1" channel). Audio mixers don't tend to put much above 80Hz in this channel because bass gets directional around that point... however, there IS harmonic content above 80Hz in the LFE channel that gives deep bass its perceived tone without being significant enough to affect perceived directionality. That is why the ONLY correct setting for LPF of LFE is 120Hz or bypassed completely (though 120Hz is typically what THX-labeled AVRs have as an option).

If you're talking about the low-pass filter on the subwoofer itself, the majority of setups should have this control turned to its maximum or bypassed so that the analog low-pass on the sub doesn't cascade with the digital low-pass being done by the AVR's defined crossovers. Doing so can create a gap in frequency response in bass redirected from the other channels (i.e. any channel set to "small" or given a crossover point) and cause LFE information above that point to be thrown away completely . However, some people use those filters to adjust out room issues, so there is not necessarily a "right setting" overall for that. LPF of LFE, however, should always be set to 120Hz.