My subwoofer is on the way and I currently run my home theater without a subwoofer. Right now I run my main speakers as "large" and my center and surrounds as "small" with a crossover of 80Hz and the subwoofer output set to "none."

Just for practice for once I get my subwoofer, I configured my home theater as if I were running a subwoofer. I set all my speakers to "small" with a crossover of 80Hz and the subwoofer output set to "sub" (not "sub + mains").

I own the original/first AVIA calibration DVD. Under "Audio Calibrations," if I go to "Main Speaker Setup" and run the "Channel Identification (5.1)," I get sound from each speaker as the tone goes through the left-main, then center, then right-main, etc. expect for when the LFE test is played. When the test reaches the LFE part, I can hear the voice say "LFE" but I don't hear any bass tone. This is expected as I have all my speakers set to "small" and with the subwoofer output selected as "sub" rather than "sub + mains."

However, under "Audio Calibrations," if I go to the "Subwoofer Setup," I have options named "Subwoofer Level, Left-Front," "Subwoofer Level, Center," "Subwoofer Level, Right-Front," "Subwoofer Level, Right-Surround," and "Subwoofer Level, Left-Surround." For example, if I select "Subwoofer Level, Left-Front" a tone is played through the left-front speaker for a few seconds, and then a subwoofer/LFE tone is played for a few seconds. I guess you are suppose to match the level of the two tones. My question is, how come if I select "Subwoofer Level, Center" (or any other main speaker/subwoofer test tone), I can hear the relative tone from the relative speaker for a few seconds and when the subwoofer/LFE part is played for a few seconds, I can actually hear bass coming from the main speakers. I would have thought that when the tone switches to the subwoofer/LFE part, I would hear nothing considering I have all my speakers set to "small" and the subwoofer output to "sub" not "sub + mains." What's happening here?

Lastly, under "Subwoofer Setup," why isn't there a simple subwoofer only test tone? Why is the subwoofer test tones "linked" to the other channels (such as "Subwoofer Level, Center?"

Hey Kain,

The SubMersive you are waiting on comes with the AudioToolkit DVD (http://www.audiotoolkit.com/) which has no confusion with the levels you should be reading and setting.

Tough to say about the spill to the main speakers seeing some bass. Some receivers might handle some things differently, and it could always be some signal crosstalk. Curious behavior, but probably not a problem in use, nor anything you can likely change without buying a new receiver.

I would guess the LFE test tone is up to 120Hz and your Xover is set to 80. It may be you are hearing tones above the XO playing in the mains. Try raising the XO and see if you get less from the mains.

Hey Kain,

The SubMersive you are waiting on comes with the AudioToolkit DVD (http://www.audiotoolkit.com/) which has no confusion with the levels you should be reading and setting.

Tough to say about the spill to the main speakers seeing some bass. Some receivers might handle some things differently, and it could always be some signal crosstalk. Curious behavior, but probably not a problem in use, nor anything you can likely change without buying a new receiver. Ah yes, I forgot about the DVD you will be including. :D

I would guess the LFE test tone is up to 120Hz and your Xover is set to 80. It may be you are hearing tones above the XO playing in the mains. Try raising the XO and see if you get less from the mains. Good point. Unfortunately, the highest crossover setting on my A/V receiver is 100Hz but I'll still give it a go.

Okay, I noticed one more thing. If I do a low-frequency sweep (200Hz-20Hz) for either the left-front or right-front speakers, I can hear traces of bass even at 50Hz and lower and this is with the front two main speakers set to "small" with a crossover at 80Hz. However, I must note that the volume or loudness of the bass is no where near that of when I do the same low-frequency sweep with the mains running as "large." With a "large" setting, my main speakers are strong till around 30Hz.

Is it normal to hear traces of bass below the crossover point for the speakers?

Okay, I noticed one more thing. If I do a low-frequency sweep (200Hz-20Hz) for either the left-front or right-front speakers, I can hear traces of bass even at 50Hz and lower and this is with the front two main speakers set to "small" with a crossover at 80Hz. However, I must note that the volume or loudness of the bass is no where near that of when I do the same low-frequency sweep with the mains running as "large." With a "large" setting, my main speakers are strong till around 30Hz.

Is it normal to hear traces of bass below the crossover point for the speakers?

That's perfectly normal. If you set the crossover to 80hz then 80 is not a brick wall, if it was it would be near impossible to get a seemless integration between the sub and mains. Rather it's where the slope begins. Most receivers if I'm not mistaken have a 12db per octave slope meaning the slope will be -12db at 40hz than it is at 80hz so you'll likely get response below 80 but it will fade the lower you go.

The fact that it isn't as loud at 50hz with the crossover set to 80hz small as opposed to the speakers set to Large would indicate the receivers crossover is doing what it's designed to do.

All is well. The subwoofer calibration tones are not encoded in the LFE channel. They are encoded in the main channels and are meant to be bass managed by your receiver according to your crossover setting. As you play the tone, it will slowly warble up and down in pitch and as it does so, it will be bass managed by your receiver appropriately, so the tone will move back and forth between your speaker and the subwoofer. And, yes, you adjust the tone so that it is at the same level as it moves back and forth between speaker and sub.

There are tones for each speaker for a few reasons. The phasing can differ between the sub and each individual speaker. And when the tone is spread across both the speaker and the sub, as you observed, there can be different interactions between the room and the tone as it is reproduced by both units. So, there can be cancellations and reinforcements depending upon the speakers' and sub's locations and their interactions with each other and the room. You can observe this first-hand as you fiddle with the tones and you can decide exactly how you want to use the tones to calibrate the sub. You can simply use the speaker closest to the sub. Or you can use the front 3 speakers, observe what setting is required to calibrate each of those individual speakers to the sub, and calculate an average setting for the sub. Or, you can even do the same with all 5 of your speakers and calculate an average setting if you wish, although I think that the front 3 are probably best if you wish to use multiple speakers to calculate an average level. There shouldn't be too much difference between the level required to calibrate the sub to each speaker, but if there is, you can see where there might be an anomaly and not use that particular speaker's result to calibrate. In the end most people end up adjusting the sub to taste give or take a few dBs, so if there are reasonably small differences from speaker to speaker, it is not really a big deal.

The subwoofer calibration tones are not encoded in the LFE channel. They are encoded in the main channels and are meant to be bass managed by your receiver according to your crossover setting. As you play the tone, it will slowly warble up and down in pitch and as it does so, it will be bass managed by your receiver appropriately, so the tone will move back and forth between your speaker and the subwoofer. And, yes, you adjust the tone so that it is at the same level as it moves back and forth between speaker and sub.

There are tones for each speaker for a few reasons. The phasing can differ between the sub and each individual speaker. And when the tone is spread across both the speaker and the sub, there can be different interactions between the room and the tone as it is reproduced by both units. So, there can be cancellations and reinforcements depending upon the speakers' and sub's location and their interactions with the room. So, you can observe this first-hand and decide exactly how you want to use the tones. You can just use the speaker closest to the sub. Or you can use the front 3 speakers, observe what setting is required to calibrate each speaker to the sub, and calculate an average setting. Or, you can even do the same with all 5 of your speakers and calculate an average setting, although I think the front 3 are probably best if you go that route. There shouldn't be too much difference between the level required to calibrate the sub to each speaker, but if there is, you can see where there might be an anomaly and not use that particular speaker's result to calibrate. In the end most people end up adjusting the sub to taste give or take a few dBs, so if there are reasonably small differences from speaker to speaker, it is not really a big deal. I see. :)

However, there is quite a bit of difference between the front-left, center, and front-right speakers' bass output. With the master volume set to the level where all speakers output 75 dB, if I run the "Subwoofer Level, Left-Front," I get around 73 dB bass output. For the center, it's about 65 dB and the right-front it's about 70 dB. Which speaker should I use to calibrate the subwoofer level? I mean for the left-front speaker, its bass output already matches the speaker tone and this is without a subwoofer.

However, there is quite a bit of difference between the front-left, center, and front-right speakers' bass output. With the master volume set to the level where all speakers output 75 dB, if I run the "Subwoofer Level, Left-Front," I get around 73 dB bass output. For the center, it's about 65 dB and the right-front it's about 70 dB. Which speaker should I use to calibrate the subwoofer level? I mean for the left-front speaker, its bass output already matches the speaker tone and this is without a subwoofer.As I said, just fiddle around once you get the sub and see how everything behaves. The reason you are seeing differences is probably because the tone is already being bass managed to some degree when you play it and each speaker is interacting with the room differently at that particular pitch. Once the sub is added to the picture things may be different. Or not. No worries. Again, in the end, most people end up adjusting their sub a few dBs here or there to taste. The tones will get you in the correct ballpark and you can fine tune things from there.

BTW, if your AVR (or processor) has some sort of auto-CAL/EQ, you should give that a whirl, too. Just to see (hear) that result, too.