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-   -   LFE Question (https://www.avsforum.com/forum/91-audio-theory-setup-chat/1895865-lfe-question.html)

James Martin II 02-15-2015 10:09 PM

LFE Question
 
Hello, Im new here to AVS and been trolling for awhile and have a question about LFE. I'll start with my planned set up. I'm looking at getting the Denon X7200w with an Emotiva UPA-7 amp, my speaker setup is Polk RTI A7's for fronts, CSI A6 Center Channel, RTI 4's for surrounds and surround backs and a PSW 110 sub woofer. OK so on with my question what I am looking at doing is on the A7's is bi amping them by passing the passive filter on the sub woofers and splitting off one of the LFE Channels on the receiver to the AMP and to the speakers. so i am wondering is the LFE channel only pass audio in the LFE frequency range? will this be too much for the speakers to handle?

Thank you
James

sivadselim 02-16-2015 01:59 AM

Although it's not absolutely clear to me exactly what you are trying to do, it IS clear enough for me to recommend you not do it.

If you REALLY want to spread the LFE channel into your speakers, consider setting your AVR up as having NO SUB connected and connecting your sub to the front channels, either via your AVR's front channel pre-outs (if so-equiped) or via a speaker level connection, with the sub's own low-pass filter adjusted to your A7's roll-off. This will reroute the LFE channel to the front channels where it will be spread across and reproduced by your front speakers and your subwoofer.

FMW 02-16-2015 03:14 AM

The concept is to use a subwoofer for LFE. That is what you should do. Don't waste any money on passive biamplification. No point in it at all. Not even a little.

NODES 02-16-2015 03:35 AM

you have great gear... get a real sub to make it sound amazing.

James Martin II 02-16-2015 03:37 AM

Ok thank you for your input.

James Martin II 02-16-2015 03:40 AM

Ya I'm saving up for a SvS pc12 sub. Been eyeing one for awhile now

Alan P 02-17-2015 04:00 PM

Why would you add that amp to a Denon 7200? :confused:

fbov 02-18-2015 11:42 AM

Quote:

Originally Posted by FMW (Post 31819881)
The concept is to use a subwoofer for LFE. That is what you should do. Don't waste any money on passive biamplification. No point in it at all. Not even a little.

+1

Why use a subwoofer? The only unforgiving reason is sound quality.

I went into this in detail on another thread. The gist is that speaker locations are fixed by imaging requirements, while subwoofer locations can be optimized to reduce the room mode/standing wave pattern.

Everyone's familiar with the Dolby recommendations for 5.1/7.1/etc. speaker placement, which are based on the program fed to that speaker, L/R, center and surrounds. Placement matters because the frequencies produced are directional, and the program calls for direcitonal cues in specific locations.

Low frequencies are omnidirectional, so it's not possible for the program to require a specific location. Low frequencies interact very differently with the room than higher frequencies (discussed in the link), interacting directly with boundaries to set up standing wave patterns. Subwoofer locaiton in the room is one tool for optimizing (minimizing) the strength of the standing wave pattern, so it's a good thing the location can vary without impacting the program. That's no longer true if any of the other speakers are also producing the LFE program.

Have fun,
Frank

sivadselim 02-18-2015 09:42 PM

Quote:

Originally Posted by NODES (Post 31820009)
.......................get a real sub to make it sound amazing.

Yep. With that sub and those towers it is certainly understandable why the OP is interested in having his main speakers reproduce some LFE. The two towers may well outperform the sub, particularly in the slam/punch department.

JHAz 02-19-2015 11:19 AM

There are two technically unrelated things that get smooshed together for lfe. First, depending on the size of the baffle, below some frequency with typical box speakers sound starts emanating omnidirectionally. Second, our ear-brain systems do not identify directionality below some frequency. There are speakers (can't remember the name of the german speaker with the fire hydrant looking tweeter) that emit highs omnidirectionally. You can still identify direction. otoh, it is the third harmonics and above that identify where the lowest note of a bass is, and it simply does not matter, from a directional perspective where the lower frequencies cone from. If you are human your ears cannot identify the direction from which a 40-80 Hz tone emanates. But the 160 Hz and 320 Hz parts of the sound start to directionalize .. .

DreamWarrior 02-19-2015 12:29 PM

Quote:

Originally Posted by JHAz (Post 31931329)
*snip* There are speakers (can't remember the name of the german speaker with the fire hydrant looking tweeter) that emit highs omnidirectionally. *snip*

MBL 101E? If I were rich, I'd put together a cigar/wine lounge in my home and these would be in it just because they look like sex, lol.

Alan P 02-19-2015 12:37 PM


DreamWarrior 02-19-2015 12:44 PM

Lol, but what about this guy:

http://audiofederation.com/ces-2012/...aker-small.jpg

Audio sculpture! I suppose I'm just nuts, lol.

JHAz 02-19-2015 04:04 PM

The mbl is exactly what I was thinking about. The primitive part of my brain expects them to expand or morph into Star Trek mankillers. Probably the sex would be good til then, though

sivadselim 02-19-2015 07:10 PM


Soulburner 02-19-2015 07:35 PM

1 Attachment(s)
If you don't already have the emotiva, skip it and add the money to your sub budget.

James Martin II 02-23-2015 06:42 AM

I got a good deal on the amp and am using 4 of the seve channels to power atmos speakers for 7.1.4 and was thinking of ways to uses some of the extra channels.

I am planning on picking up a better sub

James Martin II 02-23-2015 06:42 AM

Those speakers look wicked Kool.


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