Axiom Home Page Forums General Discussion Home Theater AV receivers/Amps confusion, please help.

Yes, it is very confusing. A google search for "LEF+MAINS" turns up a s#!t load of other folks who are confused and very little in the way of advice from the professional reviewers. I've always hated the Denon manuals. You would think that with all the product improvements they've made over the years, they would put a little extra effort in the manual .

Maybe Alan can shed some light on this for us.

For DD/DTS I simply use the "LEF" setting with the mains set to small. My main concern is 2 channel material without the .1 channel when used in direct/pure direct modes and you want mains set to large with sub output as well.

How about it Alan? What is the definitive poop on the "LEF and LEF+MAIN" subwoofer mode setting?

Yet another complication of LFE+MAINS concerns speaker level calibration vs real material.

There are various calibration sources: built-in receiver test tones, built-in player test tones, DVD cal discs like Avia, etc.

If you don't know exactly how the LFE+MAIN bass management works for the calibration method you choose, you could easily get bass doubling.

E.g. Using either Digital Video Essential or my Dolby calibration disc, there's no difference in bass output when switching from LFE=BOTH to LFE=SUB (with FRONT=LARGE). No difference audibly or on a meter. Say you have LFE=BOTH, FRONT=LARGE and set subwoofer levels based on this.

Then you play real material, say a CD. I have some organ music that outputs constant low freq notes -- easy to measure bass output on that. While playing that, if I switch from LFE=SUB to LFE=BOTH (with FRONT=LARGE), bass output goes way up -- classic bass doubling.

It is the worst possible situation -- a behavior variance between calibration and real material. That effectively means I can't calibrate bass levels with LFE=BOTH and FRONT=LARGE.

This stuff should be so easy, but the mfgs through poor documentation and lack of standardization make it very complex. And I've worked with this stuff for years -- I can't even imagine (say) my wife tackling this.

And that doesn't even include the SACD bass standardization problems, or other setup/calibration complications from multichannel analog sources.

If the home theater/surround/media vendors want broader acceptance of this stuff, they need to do a better job of documentation and standardization.

Indeed. I have a solution, albeit a costly one. For those who don't have the LFE+Mains option, as I do not, you can use the preouts on the back of your receiver to send the singal to your subwoofer. I'm actually going to try this when I get home tonight. I have my surrounds set to small, my front soundstage set to large. I think almost all receivers will at least do a large + sub setting for your front left and right speakers.

So, I have one cable coming out of the preout sub channel, and another sub cable coming out of my preout center channel (because my sub has a stereo left/right input and I'm only using one of them now, plus the bass track is mono so it should only just add additional signals). If it works out I'll probably eventually get a sub specifically for the side surrounds. So all 5 channels can be set to large and get a sub signal. Obviously this sub can be smaller than my main one.

Again, a little costly, a little room consuming, but I imagine this is the best of both worlds. Those of you with two subs can test this stuff out now.

I'll post tonight and let you all know if it works.

>>If the home theater/surround/media vendors want broader acceptance of this stuff, they need to do a better job of documentation and standardization.

The HT industry found a better and cheaper solution -- crappy little mains that don't have a hope of overlapping (doubling) with the subwoofer. Doesn't matter what setting you use with 90% of the HTIB's...

Mike, you mean that you don't find all the owners manuals to be clear and concise?....... Okay, so maybe quantum physics is about the only thing I've studied that's more complicated than a HT receiver manual. But on your LFE/LFE+MAIN point, isn't the relatively definitive poop that if you set the 3805 for LFE only in the sub, then the sub would only play LFE special effects(if and when present on DD/DTS movie tracks)and redirected bass from speakers set small. If there's no .1 LFE channel and the speakers are set large, then there's no output to the sub. If LFE+MAIN is set and the mains are set large, then the mains(and the receiver amps)will carry a full-range load and the sub will also double the bass of the mains below the selected crossover frequency.

John, are you trying to confuse me more cause it's working.

Except for the typos, the vague references to obscure intricacies, and the mis-worded/mis-punctuated sentences, the owners manuals are wonderful.

In reply to:

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isn't the relatively definitive poop that if you set the 3805 for LFE only in the sub, then the sub would only play LFE special effects(if and when present on DD/DTS movie tracks)and redirected bass from speakers set small. If there's no .1 LFE channel and the speakers are set large, then there's no output to the sub. If LFE+MAIN is set and the mains are set large, then the mains(and the receiver amps)will carry a full-range load and the sub will also double the bass of the mains below the selected crossover frequency.

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Why would it double the bass below the selected crossover? If you set the mains to large and set the crossover to a setting that is right at or slightly above what the speaker is capable of, shouldn't the low bass below the crossover be kicked out to the sub.

It seems that there should be one more "setting" choice for playing 2 ch material while using the mains as large while sending the bass below the crossover to the sub. Which, I suppose, would be the same as setting the mains to small and having a low (60Hz or lower) crossover. Come to think of it, if you are going to use a sub there is probably no point to running the mains as large no matter what thier bass capibilities are because you can always set the crossover low and the mains will still act like a full range speaker.

But in the receiver settings,what do you do if you want to run the mains as large and still use the sub to fill in below what the mains are capable while not having the mains receive a full range signal (while playing back 2 channel CD)?

Obviously, when playing 2 ch there is no .1(LFE). So if the receiver is set to "LFE" and the mains are set to large there should be nothing going to the sub. Right?

Mike, of course speakers roll off and don't suddenly stop, so whatever frequencies are still being output in the bass by the mains will be duplicated by the sub, not to a good effect in my view.

Your "Come to think of it..." is my view. If a sub is used, set the speakers small and set the crossover at an appropriate frequency.

No receiver setting could set the mains large but not force them and their amps to carry the low bass load because large means full-range by definition. The benefit of bass management in relieving the speakers and the receiver amps of part of the low bass burden requires the small setting.

Yes, if a regular stereo source with no .1 LFE channel is being played, the mains are set large and the sub is assigned LFE only, it should receive no output.

Ah! Ha! I knew that you knew that I knew what I was talking about.

It's good to know that knowers know the things they know, don'tcha know?

You know it!