[Lyson]

Apologize in advance if this is a dumb question.


How do I achieve stereo bass - assuming that it's a worthwhile pursuit. I presently have 2 subs on opposite sides of the room. My pre-pro (IR RDC-7)

has a subwoofer output and a LFE output. i have one sub connected to each. i know the LFE and subwoofer channels are different and my guess is the LFE is a separate discrete channel used for movies - does it come into play for music concert dvds?


To synthesize my questions:

1) Is stereo bass through 2 subs a good idea?

2) If so, how do you achieve it with a pre-pro that has 1 sw ch and one lfe ch?

3) Is the LFE ch a factor in music dvds?


Thanks - it seems like I should know how this works and high pass - low pass settings etc. but I don't

 

[DMF]

1) No. The ear can't localize bass, so there's no point.

2) You don't. LFE is a single channel.

3) Depends. On certain formats there may be a LFE channel. Mostly though, the processor's bassmanagement system is sending low frequencies from other channels through it to use the subwoofer (assuming your mains are set to Small as they should be).


I have no idea why a pre/pro would have a "LFE" and a "subwoofer" output. What does your manual say?

 

[bpape]

Subwoofer may be for crossed over satellites with a variable xover point/slope/etc. LFE on the other hand would probably be fixed 80Hz LFE channel only.


I'm not familiar with that piece so this is purely a guess.

 

[bgeiger]

A different perspective:


1) Bass is VERY localizable, Bass BELOW 60hz is not localizable. Most agree that the THX cutoff of 80 hz for a sub is too high, as it is localizable. That being said, if your sub crossover is set above 60 hz, perhaps it might add some additional stereo effect if there were 2 subs (after all, some higher end front speakers actually have built in subs!)


2)LFE is a separate channel. But there is more than one way to skin a cat. You could drive the subs from the front left and right pre-outputs. If your sub has speaker level inputs, you could drive the subs from the main outs of the amp, or lastly, you could "Y" the front L & R speaker outputs, connect one run to the speakers, and one to a line level converter (I do this for my tactile transducers), and then th each of the subs LFE inputs. In all examples, set front speakers to large, sub to off. So it is very possible in a variety of ways.


3)MANY music DVD's have no LFE channel. In fact, it is mostly used in DVD movies with x.1 encoding. HOWEVER, if you hook up as suggested above, ALL of your audio sources will benefit from your sub. Check this out:

http://www.polkaudio.com/home/faqad/...cle=bassmanage

 

[DMF]

"1) Bass is VERY localizable, Bass BELOW 60hz is not localizable."


While you're at it, let's redefine bass, shall we? "Bass" is not what comes out of 6" woofer. It is a frequency range. The generally accepted localizability point is 100 Hz and above. Some people won't even call >100 Hz "bass".


You don't localized a sub from the 80 Hz component, but from the harmonics starting at about 100 Hz. The better the sub, the smaller the harmonics in relation to the fundamental, and the smaller in relation to the other speakers playing in that range. Within a system, a good sub is very difficult to localize.


Your assertion that bass is localizable is not true. Subs, especially poor ones, may be localizable.

 

[spidey07]

Use the left and right speaker outputs to the subwoofers, and then from the subwoofers to the main speakers.


that way you can use the crossover in the subs and get stereo bass. I can't think of a way with receivers as I haven't seen any that let you have two stereo subs.


enjoy!

 

[Lyson]

Thanks for the replies. My subs are Aerials and they do have a number of line level outputs. I will do some experimenting - my aim here is twofold - I love bass and I love music - my current setup works fine for movies - it's the music listening I want to impact.

 

[sdurani]

Quote:

Originally posted by Lyson My pre-pro (IR RDC-7) has a subwoofer output and a LFE output. i have one sub connected to each.

Not a bad idea. The LFE channel requires 10dB more headroom than the other channels. If your subs are dissimilar, I'd use the beefier sub on the LFE output (since it will only be used for sources that have a discrete .1 channel). For the subwoofer output, I'd use the sub that best blends in with your main speakers (since it will only contain information filtered from other channels). The only downside to this set up is that one of your subs remains silent for all sources that don't end in ".1".
Quote:

i know the LFE and subwoofer channels are different and my guess is the LFE is a separate discrete channel used for movies - does it come into play for music concert dvds?

Hard to give a definitive answer since use of the LFE channel varies so wildly from recording to recording. Some music recordings (especially ones with heavy precussion) really take advantage of the additional headroom that the LFE channel can provide. Others barely have content there. Many recording enginers are still trying to figure out the best way to use the LFE channel (or whether to use it at all).
Quote:

Is stereo bass through 2 subs a good idea?

It is, though more for music listening than movies. Our human hearing has trouble localizing bass below 80Hz, but we can perceive envelopment down to 40Hz; David Griessinger (of Lexicon) and Bob Stuart (of Meridian) have demonstrated that. Mono bass has an almost in-your-head quality while stereo bass definitely sounds more externalized (think of how bass sounds when you hear live, acoustical music). In fact, if you have 2 identical subs, I think L/R stereo bass would be a better use for them than Sub & LFE; especially when listening to music (2-channel and multi-channel).
Quote:

If so, how do you achieve it with a pre-pro that has 1 sw ch and one lfe ch?

The only way I can think of is to turn off the Sub and LFE outputs and use the subs as the low frequency section of your main Left & Right speakers. Depending on the connections on the back of your subs, this can either be done via line-level connections or via speaker connections. Even if you have large speakers up front, chances are that the subs will produce the bottom octave (or two) with more authority. You'll have to set your front speakers to 'Large', since they will now be handling a truly full range signal. Your processor will re-route the LFE content to your main channels. Best part: both subs will be active all the time, with 2-channel and multi-channel material.


If you do go this route, you should experiment with subwoofer placement. The location where your speakers image best might not be the best place for low frequency reproduction. Aside from placing the subs next to their respective Left & Right speakers, you may want to try moving the subs wider apart, even to the middle of each side wall. A little experimenting and listening will let you know when you've found a good location.
Quote:

Is the LFE ch a factor in music dvds?

Same answer as above: it varies wildly from recording to recording.


Best,

Sanjay

 

[DMF]

Quote:

It is, though more for music listening than movies. Our human hearing has trouble localizing bass below 80Hz, but we can perceive envelopment down to 40Hz; David Griessinger (of Lexicon) and Bob Stuart (of Meridian) have demonstrated that. Mono bass has an almost in-your-head quality while stereo bass definitely sounds more externalized (think of how bass sounds when you hear live, acoustical music). In fact, if you have 2 identical subs, I think L/R stereo bass would be a better use for them than Sub & LFE; especially when listening to music (2-channel and multi-channel).

Interesting, and new to me. Do you have a link, perhaps?


I do in fact have two identical subs, but the intention was to smooth room response, not for a psychoacoustic effect. Maybe I can enjoy both!

 

[sivadselim]

do you not have available L+R pre-outs?

 

[Lyson]

Quote:

Originally posted by sivadselim do you not have available L+R pre-outs?

I do not. i have a SW output and a LFE output.


Sanjay - thank you very much, as well as the other replies. Nowif someone can ony succinctly explain high pass and low pass I will be a happy man. i know I am not effectively using the excellent equipment that I have which is frustrating - especially for critical music listening.

 

[Lyson]

quote:

The only way I can think of is to turn off the Sub and LFE outputs and use the subs as the low frequency section of your main Left & Right speakers. Depending on the connections on the back of your subs, this can either be done via line-level connections or via speaker connections. Even if you have large speakers up front, chances are that the subs will produce the bottom octave (or two) with more authority. You'll have to set your front speakers to 'Large', since they will now be handling a truly full range signal. Your processor will re-route the LFE content to your main channels. Best part: both subs will be active all the time, with 2-channel and multi-channel material.



How do I do this? Do I use a IC from sub to the pre-out section of the pre-pro? If so, and I adopt the suggestion of connecting it through the main speakers - which is intriguing - I assume I use the main L R pre-outs since it's going to the main speakers?

 

[hometheaterguy]

Find a picture of the back of the Lexicon MC-12 as there are outputs for stereo bass, left sub and right sub and discrete LFE. If you want stereo bass imaging as found in concert halls and theater like Bass Management you will need three subs. You will gain bass imaging and considerable more headroom output.

 

[sdurani]

Hi DMF,
Quote:

Interesting, and new to me. Do you have a link, perhaps?

Yes, a few links; at least for the David Griesinger stuff. First a quick one: read the first three questions/answers on this page (it's an interview with Dr. Griesinger from two years ago). You can also go to Dr.G's home page , where he has a bunch of his research papers posted. Scroll down about three-quarters of the page and you'll see the following paragraph, which includes a couple of links:


"Most recently the concept of interaural fluctuations has been used to solve a very old riddle - the riddle of how many independent bass drivers one needs in a sound system in a small room, and where should these drivers be put. To make a long story short: you need at least two low frequency drivers, and ideally they should be at either side of the listeners. This work is described in the recent papers on small room acoustics: Speaker placement, externalization, and envelopment in home listening rooms . General overview of spatial impression, envelopment, localization, and externalization ."


I've included the links to the two .pdf files in the paragraphs above. The first paper is 48 pages long (made my eyes glaze over) and the second paper is 15 pages long. You may want to browse Dr.G's site for other papers of interest. I read the Bob Stuart paper a few years ago but unfortunately don't have a link handy. I'll keep looking; if and when I find it, I'll post (or PM you) with the link.
Quote:

I do in fact have two identical subs, but the intention was to smooth room response, not for a psychoacoustic effect. Maybe I can enjoy both!

You should be able to enjoy both, but it will depend on subwoofer placement and the recordings you listen to. Placing the subs on either side of the listener works well for stereo bass, but I'm not sure those locations would give you the smoothest response in your particular room. Also, if you're listening to music with mono bass (usually on studio/pop recordings), then you won't get much of the externalization effect that Griesinger talks about. On recordings with strong stereo/de-correlated bass, you'll hear it more easily.


Since playback rooms, recordings and our hearing vary so much, you'll have to experiment to see what works and what doesn't. Remember to run the subs as stereo (either via the front Left & Right pre-outs or, if you have them, through stereo subwooer outputs).


Best,

Sanjay

 

[sdurani]

Lyson,
Quote:

How do I do this? Do I use a IC from sub to the pre-out section of the pre-pro? If so, and I adopt the suggestion of connecting it through the main speakers - which is intriguing - I assume I use the main L R pre-outs since it's going to the main speakers?

I'm not familiar with your pre-pro nor your subwoofers, so I'm going to guess an answer.


In the set-up menu of your pre-pro, set your Sub and LFE outputs to None. This will prevent bass from being filtered out of the main channels and should fold the LFE content into your main channels. Next, set your front Left & Right channel to Large.


There are two ways to hook up your subs: line level (pre-outs) or high level (speaker outputs). For the former, run (long) interconnects from the front Left channel output of your pre-pro to the matching input on the Left channel sub. Repeat for the right channel. Then run interconnects from each sub's line level output to the Left and Right input on your amp. This will send the pre-out signal first to the subs and then to their respective speakers.


If you want to use the high level method, follow Spidey07's advice. Run speaker wire from the Left speaker output of your amp to the matching input on your subwoofer. Ditto the Right side. Then run speaker wire from the speaker output of your subs to their respective speakers.


Whichever method you use, you'll have to set the crossover and volume level on the back panel of your sub. Find a frequency and volume level that gives the best blend (most seamless integration) between the subwoofer and speakers. The crossover setting means that frequencies below that point will be reproduced by the subwoofer while frequencies above that point will be reproduced by the front speakers.


Good Luck,

Sanjay

 

[FITZUNI]

*** OUTLAW ICBM ***

 

[bgeiger]

So DMF, what is your position. At first, you say there is no point, that "the ear can not localize bass". Last post says "...while stereo bass sounds more externalized". Flip/Flop. Must be a Kerry supporter...

 

[bgeiger]

Oh, and of course, with your logic you must feel also that high frequency sounds are not localizable, it is the bad tweeter that is localizable, and I guess I must have to go out and buy a better treeter so it wont be localizable...

 

[DMF]

No, I haven't changed my position. You were wrong before, and you're wrong now. Sanjay confirmed that the ear can't localize bass. Whether 80 or 100 Hz is the limit isn't particularly relevant. While I can't make a judgement yet on the effect he references (not having read the material), it appears that using two subs *increases* the "where is it coming from?" effect by making it sound like the bass is all around the listener. Quite the opposite of localization.


If you knew even half what you think you know, you'd keep your mouth shut.

 

[Larry Fine]

I also run my subs in stereo. While I won't call it "localization", there is a definite improvement over mono bass. It sounds much more realistic.