To LFE….or not to LFE? That’s my question.

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Well-known member
Jan 2, 2005
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Rochester, Michigan
Ok go easy on me…..

I am sub woofer illiterate. I know very little about them, but I’m trying to educate myself from the various forums and manufacturer web sites. So please forgive me for any stupid rookie mistakes I may make in this thread.

For movies, how much difference/improvement, if any, is there in using a sub connected to the LFE output of a pre/pro vs. the sub run off the extra main pre/pro output with the fronts set to full frequency (in both cases)? :confused:

Is it typical with in pre/pros to sum the LFE and FR and FL signals if no sub is selected? :confused:

This is leading into much more confusing (at least to me) subwoofer connectivity questions I have that I’d rather hold off asking for the moment.

Input is appreciated.
Subwoofer max sound LFE...


I found this article, which explains the history and development of subwoofers and LFE. It is interesting and I hope will ansewer your questions
Please check it out:

Dan, has been informing us about an up coming piece of gear, which will assist in measuring and optimizing, subwoofer/bass management in HT, the Veleodyne "SMS-1". This device looks, to be very good way to go...


Just to confuse the crap out of you I have my Depth connected both ways. I have it connected from my preamp for 2 channel music and use the LFE input for HT. It seems to work just fine. :eek:

Jeff :cool:
Robin - Thanks, I'll be sure to check out the link and yes I've been following Dan's and the other's posts on the SMS-1. It sounds like something that is almost a necessity for someone like myself for what sounds like it's ease of use and it's abilities. I don't have a sub yet and I'm postive that I want the SMS.

Jeff - That is at the heart of my question.

ML subs have both LFE and L and R RCA inputs. Unfortunately I cannot afford a ML sub, even a used one at this time. The other subs I'm looking at have only L and R inputs and outputs. So if I have a processor with an LFE output (for movies) and then I also want to run the sub from the secondary pre outs of my preamp for 2 channel how do I connect them both to the sub with only the L and R inputs? Or is it not necessary if I set the front outs on the processor to full range, running the sub from the secondary preouts of the preamp and not use the LFE?

Currently my DVD player runs through a crappy processor with almost no bass management (to be replaced soon), while my CD player runs to my preamp. My preamp has a ht bypass for the FR and FL inputs from the processor. I want the set up to give me optimal 2 channel and HT bass.
My setup is not your typical HT - 2 channel configuration. I have not posted the new pics or some of the other equipment I have picked up in the last few months. I can send you a "fair" pic if you like.

My preamp does not have a second set of "outs" so I "Y" the output to my amp and also to my sub. My preamp is part of my HT config. I use it plus 2 other amps to complete my HT setup. My surround processor has a sub out/LFE and that is what is run to the sub also. Without having both you will have to compromise a bit. One option is to run your preamp through your processor/receiver for HT then you will be able to process most of the bass. I would do this only if your processor/receiver has a bypass mode so when you want to listen to just 2 channel it will not "process" the signal. Personally I have that option but chose not too. I guess too much or a purist and simpleton. The more "hops" the more opportunity to alter the signal.

As far as setting up a sub and again, it is my personal opinion, I prefer to do it by ear. Ok for the record I do have perfect pitch but that can be a hinderance as well as a nice thing to have. Every room is different and add in every piece of equipment and peripheral stuff plus the way YOU hear it and you see there are many variables. Before this old dude lays out 500 buckeroos I would do everything I could to optimize the sound myself. Just a bit old fashioned and stubborn.:eek: :D

I hope this gives you an idea.

Jeff :cool:
I agree with you on not wanting to run the pre through the processor. I do not want to compromise my 2 channel sound, with movies I don't care so much. With the ht by-pass on the preamp, I'm running the processor front L and R though the preamp. The preamp has gain controls so that I can adjust the output to match the other channels.

So this still leaves me wondering what to do with the LFE. It sounds like without having an LFE input along with the standard L and R inputs on the sub, I'm going to have run the sub off the secondary preamp outs and not use the LFE.

Now this may be a stupid question. The sub I'm looking at has a L and R input. According to the manufacturer's website instructions, only one sub input is used for their suggested connection. So I run the preamp out to the right channel, can I run the processor LFE to the left channel?

Does anyone else have any suggestions?
For my setup, I do not use the LFE on my HT Receiver. I have my system setup first for two channel, then movies and some MCH audio stuff.

I have two pre outs from my ARC Pre Amp...One goes full range to the main speakers (CLSIIz's), and the other goes to a Xover for the Power Amp for my sub (I have a passive, cabinet only sub - gives me the choice of Xover and Power Amp).

I run my Main Speakers LARGE on HT setup, and Pre Out the main back through the HT Passthrough on the ARC Pre. I also have NO SUB choosen in HT Receiver and let it send full range signal (main and bass) to the Main Speakers. The CLS still runs full range for movies and the sub kicks in for the lower frequencies. I also pre out (to a dedicated amp) for my surround speakers (Sequel's) and they too are set to LARGE. The only thing I let my HT Reciever power is my Center Channel and my rear speakers in the 7.1 setup.

This has worked very well for me, and I still have the two channel setup for optimal sound.

Follow that?

I know what your talking about but it was a mouthful for sure. Basically translated run the front L R "full range" and run from the pre outs, if there is no LFE available, to the sub and you should be fine is what I read. :D The amount of actual LFE signal is probably a small percentage lost running it that way and I do not think most people will not notice.

Given the choice I would always run L&R signals. In your case with the sub you are looking at I would run both channels to the sub from the Pre out. :rolleyes:

Jeff :cool:
Jeff Zaret said:
I know what your talking about but it was a mouthful for sure. Basically translated run the front L R "full range" and run from the pre outs, if there is no LFE available, to the sub and you should be fine is what I read. :D

I have LFE available, but I do not use it. I use the Front Channels for full signal as the LFE and Subwoofer are disabled in my HT Receiver setup.

Thanks Dan,
I follow you and you're confirming my original thoughts. You're set up is basically what I originally figured that I would have to go with provided I did not end up with a sub with a LFE input in addition to the standard R and L RCAs. Except that I am looking at powered subs and would utilize the internal X-over (until I get a SMS-1) :D. By the way what sub do you have? I think I remember you discussing a DD-15 or 18 at one time.

That's what I'm getting at too. How much signal is lost setting the mains as Large without the LFE vs. using the LFE. Just looking for others knowledge and/or experience. My processor does not have the option to choose "No Sub", it's old and really really needs to be replaced.

One particular manufacturer shows only one connection to their sub in their owners manual pdf from their website. It had me questioning myself.
Kruppy said:
By the way what sub do you have? I think I remember you discussing a DD-15 or 18 at one time.

I have an old Sumo Sub with a 15" driver in it. If I had a DD sub, I would not need the SMS unit as the DD subs have the SMS thing built into them.

That's what I'm getting at too. How much signal is lost setting the mains as Large without the LFE vs. using the LFE.

With LFE, if I am not mistaken, you set the crossover point of the LFE and levels - at least with mine that how I think I remember it being setup. Since I do not use it, it has has been awhile from reading the manual.

For Large, I do not think you lose anything. Full range is sent to the mains as Large. One thing to look at if you are thinking of MCH music using LFE, is some units will change the signal to PCM for output via LFE.


I think we are all in agreement here. Now all we need is some pizza and beer at your house. I have my fronts and my rears set to full. Of course my fronts are CLSiiZ's and my rears are Sequel II's. :D I do occassionally here the sub in HT but most of the bass is coming from the system and sounds great.

Jeff :cool:
Hey, Pizza and beer at my place is fine with me. As long as you don't mind watching a movie on my 27" (Doh!) TV that everything is hooked up to.

I need a second job to afford the toys I want. :rolleyes:

BTW, the link Robin posted was pretty interesting.
If you are getting only one sub and your placement options are limited like in my room, be sure to get something with a parametric EQ. If your room is anywhere near normal size you will have at least 1 major room mode. In my 17' x 19' room there is a mode at around 80Hz. It is something like +15db!
That's my plan. Only one sub due to financial constraints, at least for now. With all the information that Dan has been posting on the SMS-1 and what I've seen on AVforums, I think I will end up getting one.