LFE vs High-level subwoofer connection, for FIDELITY

>> "As shown earlier, the spectrum from the music file confirms a sub 60Hz guitar solo in the right channel."

Guitars don’t typically produce sub-60 hz.  The fundamental of a low E is 82 hz.  Even drop D tuning is 74 hz.  It’s not going to produce anything lower.  Most of the energy on both guitars and bass is in the harmonics though especailly first harmonic.  What you’re showing looks like the frequency resolution / FFT size isn’t high enough.  Run it through Audacity and tighten that up with a larger size and you probably wouldn’t be thinking you’re listening to sub-60 hz guitar solos.  

>> "This isn’t correct. Set Speakers = Large and Subwoofer = No. This sends LFE to the mains and subwoofer (using high level)"

This is typically just not true.  Some high end processors can be configured to do that but your typical low end receiver as stated simply does not automatically reroute the LFE channel to the mains.  Even if that were true, why on earth would you want to send powerful LFE signals to your mains?  For real.  Watch Blackhawk Down when the Irene scene comes on and you’re sending powerful 6 hz signals to the mains?  Powered by a cheap receiver?  Why on earth would you ever want to do that?  Why on earth would you want a receiver automatically doing that if you do not have a subwoofer?  You do not, that’s why it’s not done.  

That being said, if a 20 hz signal comes through your main channels, it’s going to send that 20 hz signal to your main channels which of course will get picked up by your sub.  But what it’s not going to do is reroute the LFE channel.  It gets thrown away.  So yes you can still get a decent amount of bass going on. That doesn’t mean it’s the LFE channel.  

Even if this happened, it would be mixed incorrectly.  LFE channel effects are supposed to be 10 db hotter than everything else.  There is no way to do this properly with a high level input.  

>> "Further subwoofer effect is mono. Directional (localizable) bass is retained using high level, or as Denon has done, they created ’directional bass’ for LFE to retain full range or high level performance."

The new Denons have four subwoofer outputs.  You’re not gaining what you think you’re gaining by using high level inputs from the mains.  It’s still sending bass that can be directional to where it needs to go.  The idea that if there's an explosion behind you, it's going to send it to the rear subs.  You do not need two high level input subs up front to take advantage of this like you think.  

@paducahhometheater 

Some high end processors can be configured to do that but your typical low end receiver as stated simply does not automatically reroute the LFE channel to the mains.

It's a basic function in receivers of all budgets. does setting speakers to large and subwoofer to no route LFE signal to the front speakers? - Google Search

Watch Blackhawk Down when the Irene scene comes on and you’re sending powerful 6 hz signals to the mains?  Powered by a cheap receiver?  Why on earth would you ever want to do that?

Answer: external amplifiers. Flagship receivers can also do a fine job. I'm not sure where 'low end' receiver or budget was mentioned.

Run it through Audacity and tighten that up with a larger size and you probably wouldn’t be thinking you’re listening to sub-60 hz guitar solos.

Here's a screenshot filtered below 100Hz. There's a fair amount of energy down there.

https://mega.nz/file/bV41SJAY#97HLq57ez-QNXwZ_6Bqt1zW7fG0ZktEUVB3vzjcQxkg

You can also play this 80Hz test tone in 2CH and disconnect the left speaker to see if you can localize it. If there are confusing room modes, stand in front of the right speaker and then stand in front of the left speaker. Then switch the audio to the left speaker and do the same. I believe the first thing you should notice is the SPL being more intense in the direction of the active speaker. The next thing you'll notice is the ability to localize the intensity of the vibration as you get closer to the source. 80 Hz clean pure sine wave BASS TEST TONE frequency

The new Denons have four subwoofer outputs.  You’re not gaining what you think you’re gaining by using high level inputs from the mains.

Just to clarify, I was referring to line level and bass being 'directional' as referenced in the song mentioned earlier. It's in reference to 2CH music using high level stereo vs line level mono.

>> "Answer: external amplifiers."

Why on earth would you want your mains being slammed with 6 hz from a powerful external amplifier?  Serious question.  There's tons of infrasonic material out there today.  You're killing headroom, adding distortion, introducing the risk of damaging speakers, it's just not a good thing.  No serious home theater is going to do this.  

>> "Flagship receivers can also do a fine job."

They do not do such a fine job when pushed, no, even nicer ones.  Even with extremely efficient speakers such as pro cinema, even when crossed over at 80 hz, all it takes is like a -10 on the volume and it's going to be compressing.  Now imagine what's going to happen when you're using less efficient speakers and trying to reproduce infrasonics.  It's not going to work too well.  At all.  

I specifically mentioned a nice processor because as mentioned before, you can do things like this once you get into Trinnov or whatever.  I have yet to see factory verbiage saying a typical receiver whether it be cheap or flagship will reroute the LFE to the mains, it's all second hand forum posts or whatever as the source.  I don't believe it always works like that but even if it did, I think it's really stupid to voluntarily do that in a nicer system, just doesn't make any sense at all.  

I do have to ask... the people who are all worried about fidelity and wants to use a high level input from their amp.... why not use a Jensen transformer?  Your typical factory subwoofer with high level inputs only runs it through a resistor then into the low level inputs.  It's a cheap solution to be honest, but people are addicted to the marketing. 

If you truly cared about fidelity you'd use a Jenson transformer then plug it into the low level input.  It's going to be much more clean and linear.  Only problem is that it costs $450.  I've yet to see a single person use these but this is going to be the superior solution if you want what you say you want.  

https://www.jensen-transformers.com/product/sp-2sx/

>> "Here’s a screenshot filtered below 100Hz. There’s a fair amount of energy down there."

Dude you’re listening to SoundGarden?  You do realize that there’s kick drums and a bass guitar going during that solo right?  lol.  What is the time stamp you’re listening to?  

If you analyze the intro which doesn’t have other instruments you’ll see what I’m saying.  Notice that peak at 82 hz?  That’s a low E.  If you cross reference the guitar tabs, you’ll see that they play an open E string sometimes.  That’s as low as this guitar is going to play on this track.  The stuff below it is just junk, it’s registering as low as 1 hz on the intro, just not reality... distortion artifacts or something, it’s never going to go away if there’s anything playing at all.  Most of what you hear on a guitar is going to be the second harmonic.  Seeing the biggest fattest spike start up at 164 hz isn’t a coincidence.