I was just poking around on the Polk Audio site, and saw this article:
http://www.polkaudio.com/education/article.php?id=19

If I'm reading it right, there are basically three options for getting bass out of your subwoofer in a 5.1 setup:

(1) Set L/R front speakers to "large" and attach the sub to the subwoofer output.

(2) Set L/R front speakers to "small" and attach the sub to the subwoofer output.

(3) Set L/R front speakers to "large", subwoofer to "off", and attach the sub to the front L/R outputs, then connect the speakers to the sub L/R outputs.

If you go with option (1), the sub will only play the .1 of the 5.1 channels. This is fine if your front speakers can handle a pretty full range of sound, but not so good if you want the sub to be helping out with general bass.

If you go with option (2), which is what I've often seen recommended here, the receiver will filter out low tones from the L/R channel and pass them through to the sub. This is good for getting the sub to help out, but potentially creating a "hole-in-the-midrange" effect (as I understand it, the risk is that everything under 150 Hz gets filtered out of the L/R channel, and everything over 80 Hz gets filtered out of the sub channel, leaving a hole from 81-149 Hz).

With option (3), the receiver packs the .1 into the front L/R channels, which go to the sub. The sub then does its thing according to its own crossover setting and passes the rest to the front L/R speakers. This supposedly produces the best blending.

Is this right? If it is, it seems like option (3) is clearly the way to go, but I haven't seen it recommended very often here. Am I missing something?

Sometimes it seems like doing more research on speaker setup just teaches me new things to worry about, instead of providing definite answers.

Jake

If you have a 5.1 setup, and a receiver that does 5.1, the best way would be to use the Sub preout. Depending on your speakers is where you would need to set your crossover. If you have large floorstanders that can go low, set you mains to large ,and have your sub take the lowest settings. If you have small speakers and set your crossover at 80hz, (THX setting) If I understand correctly the .1 channel on soundtracks is specific for subs, so if you do not use this channel you might be missing out on some of the soundtrack, if you route the sub to the speakers. For general music, some people shut off the sub, and run their speakers as large. Depending what I am listening to, I sometimes do this.

jrl264,

You seem to have a VERY GOOD understanding of your various options. This is refreshing, as we often encounter people on this site who are either clueless or uneducated regarding how bass management works.

One thing that I would like to clarify is that with Option #2, as long as you set the crossover in the receiver properly for your particular speakers' capabilities, you will not lose any info, and there will be no "hole-in-the-midrange".

Regarding Option #3, as evidenced by your post, you already know that NONE of the LFE channel info will be lost, but instead will be properly routed to the front L/R channels and, if you wired a sub+speakers to these outputs, the LFE will be reproduced properly by the sub+speakers.

The recommendation by Polk to connect your equipment this way (#3, receiver set to NO SUB, sub+speakers wired to the front L/R speaker outputs) is quite dated, as AV receivers have become more standardized and functional regarding their bass management capabilities and schemes.

That said, Polk's recommendation is actually not a bad one. One reason for this is that subwoofers' crossovers are often not as steep as the digital crossover used in AVRs. Also, most subwoofers don't have a continuously variable crossover, per se, but instead, have a fixed high-pass filter, usually in the neighborhood of 80-120Hz and a continuously variable low-pass filter that is controlled by the sub's "crossover" knob. With an AVR, the digital crossover, although limited to particular values, does vary both the high-pass and low-pass filter settings similarly to the way a truly continously variable crossover would work. With Option #3, the result of the subwoofer's own "crossover" being shallower, plus the subwoofer's high-pass being fixed while the low-pass is variable, can actually provide for, as you say, better blending of the sub with the speakers.

Now, I know that some of this info directly contradicts what the Polk article says, but as I indicated, the Polk article is quite dated and AVRs' bass management capabilities and methodologies have changed considerably since that article was written. Many of the early "kinks" have been ironed out. Some of the Polk info is just not applicable anymore.

An issue that you will have with the Option #3 setup is that it will make proper calibration with the usual methods (calibration DVDs or receiver test tones) a bit problematic, although not impossible. Most people with this sort of setup would simply adjust their subwoofer's output level (with the sub's volume knob) and "crossover" setting (with the sub's "crossover" knob) by ear, usually with music.

Another issue that you may encounter if you listen to hirez (DVD-A/SACD) music is that, in most cases, the hirez player will be connected via a 6-channel analog connection which includes an LFE connection. In almost all hirez players, if you set the player up as having NO sub, unlike with an AVR, the LFE channel will NOT be properly routed to the front L/R speaker outputs and instead will be lost. This, of course, is not an issue for you if you don't have a hirez player.

My recommendation would be to try both Options #2 and #3 and see which you prefer. It IS possible to get satisfactory results with Option #2, provided the system is properly calibrated.

If you go with option (2), which is what I've often seen recommended here, the receiver will filter out low tones from the L/R channel and pass them through to the sub. This is good for getting the sub to help out, but potentially creating a "hole-in-the-midrange" effect (as I understand it, the risk is that everything under 150 Hz gets filtered out of the L/R channel, and everything over 80 Hz gets filtered out of the sub channel, leaving a hole from 81-149 Hz).

Not true. If you set the crossover in your reciever to 80hz, your main speakers will play every frequency from 150hz-80hz.

To add another tidbit to sivadselim's excellent comments, there is one more advantage to Option 2, and that's amplifier efficiency. With Option 2, the lowest frequencies are filtered from the "small" channels before the amplifiers, thus reducing the load on the amps. This increases amplifier headroom and reduces amplifier distortion, allowing the entire system to play louder and more cleanly.

With Option 3, the amp's are still sent a full-range signal which is then sent to the sub. The sub filters off the low frequencies, re-converts the bass to a line level signal and then sends it to the sub amp, and sends the remaining speaker level signal to the speakers. The amplifier efficiency is lost. This may not be a problem in systems with large amplifier capacity and/or high sensitivity speakers. However, in most HT receivers at low to moderate price points, this amplifier efficiency is a tremendous benefit, especially if they are driving low to moderate sensitivity speakers. 50 to 100 watts can play much more cleanly if it doesn't have to reproduce the bottom 2 octaves, (which are the most power hungry 2 octaves). (BTW, this amplifier efficiency is also lost with Option 1 for any channel set to "Large").

As sivadselim said, that Polk article is outdated and current receivers, even at moderate price points, have adequate Bass Management to allow the sub to be connected to the subwoofer output jack.

This is good for getting the sub to help out, but potentially creating a "hole-in-the-midrange" effect (as I understand it, the risk is that everything under 150 Hz gets filtered out of the L/R channel, and everything over 80 Hz gets filtered out of the sub channel, leaving a hole from 81-149 Hz).
For speakers that only get to 150 Hz, there is no Bass Management scheme that will work well. If you connect the sub at speaker level and have the sub play up to 150 Hz, you'll trade the "hole" for "localization". 150 Hz is "localizable" by most humans, (IOW, you can tell where it's coming from). Deep male voices and many other mid-bass sounds fall into this category. You will be able to hear them as originating from the subwoofer, not the speaker they were intended to originate from. I have heard this effect with small satellite speakers crossed over above 80 Hz, and it is quite distracting. Frankly, I would take the "hole".

Craig

Not true. If you set the crossover in your reciever to 80hz, your main speakers will play every frequency from 150hz-80hz.
Only if they're *capable* of reproducing those frequencies. Many small satellite's are not.

Craig

Option (3) works particularly well with a matching pair of subs set up in stereo. Otherwise, option (2) will usually get the best results.

Thank you everybody for the very helpful comments. Sounds like option (2) is the way to go--I figured it was unlikely that everybody on this forum was giving inaccurate advice, but the Polk article looked credible enough to make me worried. I'm relieved to hear that it's no longer correct.

I love all the knowledge that everybody brings to the forum. Has anybody ever tried setting up a wiki or something to provide a basic guide for n00bs looking to purchase/install/calibrate home theater systems?

Jake

Dr. Pain (the king of lists) did assemble this list of useful links:


http://www.hometheatershack.com/forums/general-discussion/4083-setting-up-your-home-theater-101-a.html

To add another tidbit to sivadselim's excellent comments, there is one more advantage to Option 2, and that's amplifier efficiency. With Option 2, the lowest frequencies are filtered from the "small" channels before the amplifiers, thus reducing the load on the amps. This increases amplifier headroom and reduces amplifier distortion, allowing the entire system to play louder and more cleanly.Good point. :cool:

Only if they're *capable* of reproducing those frequencies. Many small satellite's are not.

Craig

Are you serious? I never heard of that before. Thanks.

Are you serious? I never heard of that before. Thanks.
Never heard of WHAT before? :confused:

All he's saying is that some speakers are so small that they don't reproduce sound down to 80Hz, but instead may only reproduce sound down to 150Hz (or even higher), for example.

So, if you had speakers that only played down to 150Hz but you set your receiver's crossover to 80Hz, you WOULD create a "hole" between 80Hz and 150Hz.

A receiver's crossover must be set appropriately for the low-end capabilities of the speakers that are connected to it. In the case of speakers that only played down to 150Hz, you would want to set the receiver's crossover to at least 150Hz if not even higher than that.

A receiver's crossover must be set appropriately for the low-end capabilities of the speakers that are connected to it. In the case of speakers that only played down to 150Hz, you would want to set the receiver's crossover to at least 150Hz if not even higher than that.
Unless you prefered the "hole" to the localization issue of the sub as I described above. :)

Craig

Unless you prefered the "hole" to the localization issue of the sub as I described above. :) I'll take the localization issue, please. ;)

I guess we could add the recommendation that, if the crossover is set so high as to make the sub localizable, that central placement of the sub relative to the front speakers would be preferable.

Never heard of WHAT before? :confused:

All he's saying is that some speakers are so small that they don't reproduce sound down to 80Hz, but instead may only reproduce sound down to 150Hz (or even higher), for example.

So, if you had speakers that only played down to 150Hz but you set your receiver's crossover to 80Hz, you WOULD create a "hole" between 80Hz and 150Hz.

A receiver's crossover must be set appropriately for the low-end capabilities of the speakers that are connected to it. In the case of speakers that only played down to 150Hz, you would want to set the receiver's crossover to at least 150Hz if not even higher than that.

Where in the original post does it mention speakers incapable of playing below 150hz? He was under the impression that the LFE output of the receiver would leave a hole in the sound. This is impossible. He didn't say a word about small speakers. Read this paragraph again:

If you go with option (2), which is what I've often seen recommended here, the receiver will filter out low tones from the L/R channel and pass them through to the sub. This is good for getting the sub to help out, but potentially creating a "hole-in-the-midrange" effect (as I understand it, the risk is that everything under 150 Hz gets filtered out of the L/R channel, and everything over 80 Hz gets filtered out of the sub channel, leaving a hole from 81-149 Hz).

Whether he meant it or not, this paragraph is pretty clear that it's the LFE output, and not some imaginary satellite speakers, that is leaving the hole. That's why I said it is not true, as this is impossible.

Where in the original post does it mention speakers incapable of playing below 150hz? He was under the impression that the LFE output of the receiver would leave a hole in the sound. This is impossible. He didn't say a word about small speakers. Read this paragraph again:
Whether he meant it or not, this paragraph is pretty clear that it's the LFE output, and not some imaginary satellite speakers, that is leaving the hole. That's why I said it is not true, as this is impossible.
I think this is just an example of some sort of misunderstanding about the way we're interpreting someone else's post and we're not all "on the same page".

You said that the scenario the original poster presented of there being a "hole" from 80Hz to 150Hz wouldn't occur if the receiver's crossover was set to 80Hz. And just for clarification, craigjohn responded that, yes, there wouldn't be a "hole" in that situation (receiver's crossover set to 80Hz) as long as the speakers were capable of playing down to the receiver's 80Hz crossover setting. To which you clearly responded that you'd "never heard of that". So, I was confused about what you were saying that you've never heard of. Which is why I posted what I did for even further clarification. There was nothing incorrect about what craigjohn or I said. We thought it was relevant to the example the original poster presented.

But it's not really clear to me exactly what the OP meant in his example. I'm not sure from where he got the "80Hz to 150Hz hole". If you just simply read it as it's written, it is actually the receiver that is leaving the "hole". I agree that he makes no mention of any small speakers, but to me, he is implying that there ARE some small speakers in his hypothetical scenario that are incapable of reproducing frequencies below 150Hz. So this is what I assumed he meant. Otherwise, I can't figure out where the 150Hz number comes from. But I did NOT interpret what he said to mean that he thinks that a receiver will simply drop all the frequencies between 80Hz and 150Hz, from both the sub and speakers, for no apparent reason. Maybe that IS what he meant, but I'll give him the benefit of the doubt and assume that he doesn't think that.

The way I read it is there is a "hole" in his example that comes from the gap created by setting the receiver's crossover significantly lower (80Hz) than the low-end capabilities (150Hz) of some hypothetical speakers. The only way to avoid such a "hole", assuming that he IS presenting an example where the speakers are incapable of reproducing sound below 150Hz, would be to set the receiver's crossover to 150Hz or higher to allow the subwoofer to reproduce the lost frequencies that were, in his example, the "hole".

(BTW, the subwoofer's output, when any of the speakers are set to SMALL in the receiver, is not simply called "LFE". The subwoofer's output contains more than just the LFE channel if any of the speakers are set to SMALL; it also contains those bass frequencies, below the receiver's crossover setting, from any speaker channels that are set to SMALL. Bass and LFE are two totally different things.)

I believe I was just repeating some outdated information from the Polk article, which stated that the "Small" setting would set a filter at 150 Hz. That statement is no longer accurate, if it ever was.

The only way you could have the same sort of problem today if your speakers bottomed out at 150 Hz, so I understand why my statements could be interpreted that way.