A question concerning the use of LFE when playing 2-channel only music

[Turbota]

From Wikipedia:

The Low-Frequency Effects (LFE) channel ...... 'A channel used in surround sound'

LFE is the name of an [audio track] specifically intended for deep, low-pitched sounds ranging from 3-120 Hz.

This track is normally sent to a speaker that is specially designed for low-pitched sounds called the subwoofer.

While LFE channels originated in Dolby Stereo 70 mm film, LFE became commonplace in the 1990s and 2000s in home theater systems used to reproduce [film soundtracks] for DVDs and Blu-ray discs.
____________________________________

So, the way I understand it, is that LFE is actually a dedicated channel of low freq. audio found on the audio track of movies from sources such as movie DVDs ... As an example, this LFE would be very noticable when listening to a movie when a cannon is fired. The LFE channel would give your subwoofer in your AVS system a good amount of this low freq. sound of a loud cannon discharging.

However, the way I understand it, is that 2-channel music such as from a CD, Phono, Audio Tape, or Streaming Music from Spotify, etc does not have the LFE channel as part of it.

So .... My question is .... If you have a 2-channel audio system (no AVS), should you ever hook up a subwoofer to your 2-channel audio receiver / pre-amp using the LFE wire connection?

My guess is you will get none, to very little sound from your subwoofer if you do.

And because of this, you really need to wire your receiver / preamp to your subwoofer using RCA cables between the receiver's Audio Pre-Out (L/R) and the subwoofer's Audio Input (L/R)

Bottom Line ... Stay away from LFE unless you are watching movies on a Home Theater System.

What ya think ? ?

 

[slobmw]

Yes and no. At least some (most? dunno) receivers will also send low frequency signal from stereo signal to your LFE out, depending on your settings (xover, speaker size, what have you).

This requires the DSP chip in the receiver to work it's magic, so often the "stereo direct" function will disable this. In that case, you are right, no sub out and you'd need to use the subs DSP to sort all that out like you suggest.

 

[Turbota]

Thanks "slobmw" ...

In my case, I am using a 2-channel integrated amp, so I have no ability to set 'speaker size' or 'crossover' on the amp itself ... The amp certainly is not a AVS type system.

Fortunatly, it does have a Pre-Out, so that helps a bunch.

 

[slobmw]

D'oh! Sorry about that, sneaking in a quick look at work doesn't make for careful reading.

I had my 2 channel integrated amp set up like that when I was running a sub with it. What I didn't realize is that then does not cut the bass (just the LR speakers) when I plugged headphones into the amp - as my son pointed out to me the first night I tried to rock out past his bedtime.

I didn't notice, as I was using open back headphones and the bass come through just fine.

 

[Aspen]

Took me a while to understand, but you are asking if you should use the LFE input on the sub, right? Since your amp has no LFE out, then no you should not use the LFE input. Just use the RCA to the sub from the pre-outs and use the subs x-over control to blend with your speakers. You could also use high level speaker wires to the sub if you have those inputs.

 

[Turbota]

Aspen ...

I believe the single subwoofer RCA plug on the rear of my amp is in fact LFE (red arrow)

But why hook the amp up to the sub via LFE if the 2-channel music source does not contain a dedicated LFE audio channel.

On the other hand .... Maybe I am wrong about my amp having a LFE-Out ?

 

[Superampman]

I have both line level speaker posts and R/L LFE on my two Velodyne DPS12 subs. I use both L & R LFE inputs via Y cable with both direct to my Oppo UDP205 along with the main power amps so no pre. I find they sound better out of the LFE.

 

[onplane]

From Wikipedia:

So .... My question is .... If you have a 2-channel audio system (no AVS), should you ever hook up a subwoofer to your 2-channel audio receiver / pre-amp using the LFE wire connection?

What ya think ? ?

Turbota, your Onyko two channel amp has a sub out. Onkyo doesn't give specifics on what's going on here, but my guess is on this output you will get a line level signal that consists of the sum of low frequencies of left and right channels.

In short, it will do what you want.

On the other hand, if your sub has speaker level inputs (not all have these) many folks including one of the premier sub manufacturers believes that for two channel music systems, these are preferred. Reason for this is when using speaker level inputs, your sub "sees" exactly the same signal as your mains including any phase shifts introduced in the power amp.

Hope this helps...
Regards,
Jerry

 

[whoaru99]

Aspen ...

I believe the single subwoofer RCA plug on the rear of my amp is in fact LFE (red arrow)

But why hook the amp up to the sub via LFE if the 2-channel music source does not contain a dedicated LFE audio channel.

On the other hand .... Maybe I am wrong about my amp having a LFE-Out ?

Didn't I explain this in the other thread, or was that someone elses thread on the exact same thing?

 

[Turbota]

Turbota, your Onyko two channel amp has a sub out. Onkyo doesn't give specifics on what's going on here, but my guess is on this output you will get a line level signal that consists of the sum of low frequencies of left and right channels.

In short, it will do what you want.

On the other hand, if your sub has speaker level inputs (not all have these) many folks including one of the premier sub manufacturers believes that for two channel music systems, these are preferred. Reason for this is when using speaker level inputs, your sub "sees" exactly the same signal as your mains including any phase shifts introduced in the power amp.

It's a Polk powered sub.

Here is a photo of the rear panel:

 

[onplane]

It's a Polk powered sub.

Here is a photo of the rear panel:

Yep, no speaker level inputs. Too bad. Anyhow, the LFE output from your Onkyo is designed for the LFE input on the sub.

It will provide the "sum" of low frequencies from right and left channels. It would NOT work in the case where you had dual subs, one for each channel.

Regards,
Jerry

 

[whoaru99]

http://audiokarma.org/forums/index....nnel-audio-system.814512/page-2#post-11425814

 

[Turbota]

Didn't I explain this in the other thread, or was that someone elses thread on the exact same thing?

You sure did in another thread ... I guess my brain is confused again about the hook-up of a sub since I now have read that LFE only pertains to the audio in movies (DVD's, ect).

Well, from here on out, I am going to drop this whole question about the hook-up and just wait till the sub shows up here ... and then connect it the various different ways and see what sounds the best ... and then leave it at that.

Ron,

 

[Turbota]

Yep, no speaker level inputs. Too bad. Anyhow, the LFE output from your Onkyo is designed for the LFE input on the sub.

It will provide the "sum" of low frequencies from right and left channels. It would NOT work in the case where you had dual subs, one for each channel.

Regards,
Jerry

Thanks Jerry ..

 

[whoaru99]

@Turbota

What is the exact model of the sub you have coming in?

The LFE input on a sub doesn't strictly mean it is for use only with an HT system. It depends on what the sub can do with that input.

Some subs it is intended specifically for that use, others can be switched or set to use it other ways.

If we know the specific sub model we can answer specifically

 

[JoeESP9]

The Yamaha HTR in my bedroom produces a signal on the LFE channel regardless of which input I select. If I set it for Straight (no processing) select the Aux front panel input and connect it to my laptop playing 2 channel FLAC files via a USB DAC, I get output from the subwoofer. This is reflected in the receiver's display as it shows two speakers and the sub.

 

[musichal]

The LFE input depends on the signal from the receiver/amp incorporating the amp's own crossover controls, or the LFE HT channel. The RCA inputs allow you to use the crossover controls on the subwoofer. So the answer to your question really is that there is no hard and fast rule; it depends on what signal options your amp, or preamp, provides. When I used a two-channel Emotiva XSP-1 preamp, which has built-in discrete-element, adjustable subwoofer settings, I used the LFE input on the Klipsch R-15 sub rather than Klipsch's control settings.

When I switched to the system in my signature, I fed a FR signal from the two-channel Levinson integrated amp via unbalanced ICs, using the SVS subs' controls. There's no real hard-and-fast rules, and what works best will depend upon the options your specific gear offers, which it would appear some here have researched for you.

 

[Turbota]

What is the exact model of the sub you have coming in?

It's a Polk HTS 10

https://www.polkaudio.com/products/hts10

 

[onplane]

It's a Polk HTS 10

https://www.polkaudio.com/products/hts10

Oops, according to the Polk manual the LFE input assumes the receiver is sending only low frequencies. That might not be the case here!

That would mean that frequencies way too high are being sent to your sub.

You should try adjusting the sub's frequency filter to see whether you can hear any difference and I suspect that you will NOT. You really want to engage that filter and you have two choices:

1. Connect L and R pre outs to the sub

2. Use the LFE output and get a Y so you connect to the L and R line inputs on the sub.

Regards,
Jerry

PS: Just to show how confusing this gets ... in my sub the internal adjustable filter is always engaged. When connecting to an AVR, we just set it to max frequency and let the AVR adjust downwards. Your sub is specifically marketed as a home theater sub.

 

[whoaru99]

@Turbota

Perfect.

On this sub the LFE input is unfiltered so you do not want to use it with the sub output on your amp.

You could, however, connect the amp's sub output jack to one of the other two line level inputs.