I am having trouble figuring out how to set my sub level as per the instructions on the Avia CD. I am able to set all of the other 5 channels fine at 75 db. The test for setting the subwoofer, puts out a test tone for both the individual channel and the subwoofer and it alternates back and forth so you can match the two. It says you only need to match it to the first tone, which is the front left, since I only have one subwoofer. I can never get the db level low enough on the sub to match the front level. Tlowest I can get it is around 85db and this is with the sub set at -10db on my receiver. ( the lowest setting) I can even turn it off and the woofers in my mains are around 85 db and they are not adjustable. What gives here? I know many on here say to set the sub to 85 db. Why does Avia say to set match it to the mains? Also doing a frequency sweep shows that my front right doesn't have the peak db readings that my fron left has. What can I do to improve this. At around 72hz my front left peaks out at around 95db at the same frequency my front left is closer to 80 db.

I assume you are using 2 subs...I would check out the sensitivity adjustment that is located on the back of most powered subs, that is probably your culprit. Having these out of wack will cause one sub to reach it's full output with a lower input voltage. Although they do adjust volume, these controls actually vary the input voltage to your amplifier, not the 'amount of watts' to the speaker.

Matt, I only have one subwoofer. The Avia CD allows the user to match each channel with it's sub. (assuming you have a subwoofer for each channel) Since I only have one subwoofer they say to just match it with the front left. My problem is I can't get the sub or bass test tone level to match the tone coming out of the left front speaker. I have the left front set to 75 db. I can NEVER get the bass tone that low. Even if I shut the sub clear off. The bass coming from my main floor speakers ( 12" woofers) is around 85 db even with the sub level on the reciever set as low as it can go. Avia says the sub level should match, the mains evenly.

It seems to me that my subwoofer is somewhat of a useless component to my system. My main speakers at 75db with the sub shut off produce too much bass according to the Avia test tones. Here is my setup.... 1. Running a Kenwood VR 507 with the Cinema EQ Mode enabled. 2. Pioneer 3 way floor speakers for mains with 12" woofers. 3. Aiwa 8" sub. 4. Center channel has dual 5 1/4" Pioneer. 5.Surrounds are one-way Pioneer.
I have receiver set to Large for fronts. The center and surrounds are set to Normal. Is there a better use for my sub? Presently it is just connected via LFE. I only use this gear to for Home Theater. I don't care about music. Is anyone familiar with the test on the Avia DVD where you match your sub to the other channels? Aren't you in fact just matching the LFE to the other channels? This must be the case because, even with my sub off, it still registers as 85db on the low frequency test tone. Any ideas?

Think, if you're getting the sub's level test tone, I think you need to fiddle with the bass management settings. It sounds like the sub (LFE) track is being redirected to your main speakers, especially if you're hearing the test 'rumble' with your sub turned off.

In reference to your top post, you might try BOOSTING the other channel levels to bring them closer to the bass level. Remember, there are no 'absolutes' when using decibels for level matching, only 'relatives'.

Larry

Well, if you set your front speakers to large, you may be bypassing the LFE output of your sub altogether (as Larry said). I'd check that first. Otherwise, the sensitivity control still stands true, adjust that down so your receiver sends a smaller voltage to your subwoofer. That will allow you to match it a bit better.

Thinkly, it looks like you may already have some of the answers I tried to post yesterday (did anyone else have problems?)

Reference the main question in your original posting (bass levels), the Avia disc subwoofer test compares the levels of a "high freq" signal from your (left) main speaker to a "low freq" signal from the sub. BUT (as Larry and Matt pointed out) if your main is set to Large it is also getting the "low freq" test tone. So you're definitely getting way too much low freq test tone! If you temporarily set the main speakers to Normal/THX the left main should only get the higher test tone and the subwoofer should only get the lower tone. After balancing, you can go back to the Large setting on your mains if you wish (but see below).

Reference the second question in your original post (85db vs. "match to the mains"), the Avia disc recommends that you balance ALL (non-sub) speaker levels to 85db if -- and this is a very big if -- you want to calibrate at the THX studio reference level. The disc then goes on to caveat this by stating in multiple places that you may find this level too loud. It also mentions that "most" of its test tones are designed to balance at 75db. Confusing, huh? But... I don't know what formula they used to generate the subwoofer comparison tones, and I haven't tested it myself (I'm not using a dedicated subwoofer at the moment). My theory is that Avia has taken the "extra"
10db into consideration when devising the subwoofer test tones. Therefore if you follow their directions of first setting your main levels -- to whatever level you want to listen at, perhaps 75db? -- and then balancing your subwoofer by using the special sub tone and ONLY adjusting the sub's level, the Avia people have set it to be in the proper balance. I'd be interested in knowing whether the "high freq" test tone is the same level as the tone they use to initially balance the main speaker levels. (Guess I'll be digging out the SPL meter tonight :) This seems to be borne out by your observation that after you calibrated your mains to 75db, the low freq subwoofer test tone came out at 85db.

Moving along to why your left and right main channel show a different SPL at 72Hz: (BTW, your post says that both the 95db and 80db are your "left" channel :) The difference is almost certainly due to the room's acoustics rather than the speakers. Perhaps one speaker is losing part of its output into an upholstered piece of furniture, or the other is bouncing off a glass-framed picture, etc. The simplest way to fix this is with an equalizer. IMHO, equalizers are absolutely essential in any setup where you want to get a balanced output from multiple speakers.

Reference your later posting about whether your subwoofer is "useless:" In theory, with your current system settings you still need your subwoofer. When your sub is connected to the LFE channel and the receiver knows it's there (is set to "Subwoofer ON"), it should be the only speaker getting the signals for that channel. Setting your other speakers to Large or Normal/THX should not impact on this at all: That setting should only determine whether or not the bass information on those channels is sent to the subwoofer IN ADDITION to the LFE information it's already getting! (LFE should only be directed to Large speakers when the reciever has been told there is no subwoofer, which is not the case with your configuration). Notice I use the word "should" a lot. Larry, jump in here if I'm wrong. So with your current settings, your subwoofer is the only speaker receiving not only the LFE, but any bass from your center and surrounds. Definitely not useless IMHO.

My recommendations: First, set your mains to Normal/THX, and see if you can then successfully use the Avia subwoofer test tone to balance the sub. Keep Larry's comment in mind: If the max reduction (-10db) setting on the sub is still too loud, you may have room from your initial balancing to raise your other speakers' level settings to meet it. Second, assuming the above works, play your favorite movie scenes with the following three settings and pick the one that you enjoy listening to the most!
1) All speakers "Normal/THX" and "Subwoofer ON."
2) Mains "Large," others "Normal/THX," "Subwoofer ON."
3) Mains "Large," others "Normal/THX," "Subwoofer OFF."
Switching back and forth between options two and three should tell you pretty quickly whether your sub is making a worthwhile contribution.

One last possible consideration, if you still can't get the sub's level low enough. Your subwoofer's placement may be allowing it to take unfair advantage of the listening room's acoustic resonance factors, making it too loud. Try moving it to a different location and see if that makes it quieter. A good article on placement advice can be found at [Link: sonicdesign.se]

Remember, the test tones are only the starting point. What really matters is whether your subjective ears enjoy the sound!

-Bruce

This message was edited by Bruce Burson on 12/19/01 10:06.26.

I'd be interested in

Great info, everyone. Bruce, I am aobut 95% sure that I did experiment with setting the mains to normal and I still had a HEAVY bass tone coming out of the mains. I need to play around with it more to be sure. I am a little uncertain on the way my receiver handles LFE. The manual states that if the mains are set to Large, than there will be no signal sent to the subwoofer. I can understand that fine. It then goes on to say that if you have the recever in the Cinema EQ mode (which I do because the sound is MUCH more dynamic)than the subwoofer will receive a signal. What are they doing here? Also as for the second quote above, the high freq test level does fall in right around the 75 db level on my front left. That is what I calibrated all of the others to as well. I guess the thing I am a little fuzzy on is the role of the subwoofer in my system. Supposedly if I set the mains to normal than the sub will receive all of the LFE. I am not certain that is taking place with my receiver. (I will investigate again) I am quite positive that it doesn't do that because I can toggle between normal and large and I notice no difference while using the test tone or watching a movie. I will assume that the sub will handle the lfe for all other channels as well, regardless of the Large or Normal setting on the mains. I now have the sub backed off as far as possible, from when I was trying to match the bass signal to the higher signal. Maybe it won't matter anyway if my mains are set to Large or I guess in my case it will never matter because apparently my receiver is sending LFE to the mains regardless. At least the Avia CD using the sub match application goes that way.

Wouldn't this mean I would have to set my other channel levels to 85 db? I think that would be too much for comfortable listening. When you say that there are no absolutes - only relatives, what do you mean specifically? Do you think it is possible that with my setup, quite possibly the only way to match the two is to raise the other channels? I don't know what other bass management tools I have at my disposal. My receiver only has settings for large and small and also provides for turning the sub off and on. I can also obviously adjust the sub level, I just can't get it low enough to "pass" the test on the Avia DVD.

Think, yes, that's what I mean. If you boost the other channels for a match, but then reduce the overall volume by the same 10 dB, you will be back at the desired level while having the match you're trying for.

By relative, I mean that the matching at any level is more important than attempting to hit a specific dB rating.

Referring to the last few of posts, I meant to check that you have the sub output IN THE RECEIVER'S BASS MGT. turned on. Unless I'm mistaken (hey, it could happen! :-)), the test tone for the sub channel should only come out of the sub output, and not be heard at all when the sub ITSELF is turned off.


About the speaker settings in bass management:

With the sub output on, the LFE track (.1) should only be heard through the sub, period.

Any speaker set to 'large' should have its entire range played through that speaker, bass and all.

Any speaker set to 'small' should have its bass redirected to the sub, UNLESS the sub out is set to 'off', in which case the bass from that channel AND the LFE track will be redirected to, in this order, the mains, the center, or the rears. (some may try mains, rears, center)

If there is NO sub, and ALL speakers are set to 'small', the LFE track and the rest of the bass will not be reproduced at all.


My point is: If you're getting the LFE's test tone through the mains, it sounds like the sub output is being sent to the mains instead.

Larry
www.fineelectricco.com

This message was edited by Larry Fine on 12/13/01 11:30.33.

What they said..... ; )

Thinkly,

Sorry to take so long to post this. After eight futile hours of trying to post, I finally realized that my account had gotten blown away. So now I've rebuilt it, hopefully this post will be accepted...

I said I would dig out the SPL meter.

I ran the Avia disc against my rig last night. First I adjusted the master volume so that the left main calibrated at 75db when the reciever's channel adjustment level for that channel was at zero. Then I balanced the other channels' individual adjustment levels plus or minus until all channels were delivering the test tone at 75db.

Finally I switched to the Left Main & Subwoofer test tone. Drum roll, please... Ta Da! The high tone from my left main was delivered at 85db. Avia comes through again: If you match your subwoofer's low tone to that high tone, it will be 10db louder than the other speakers were calibrated to. Always assuming you can keep that low test tone away from your mains, of course. :)

-Bruce

Here is some info from Guy Kuo of Ovation Software that may help you understand the AVIA DVD....I found it very helpful:

Quote: I've been reminded that the subwoofer calibration in AVIA is more complex to use than VE and thus more time consuming to recommend. I think it's time to revisit the reason and advantages afforded by the approach chosen.

AVIA intentionally carries its low bass test signals on each of the five main channels independently instead of the LFE channel for the express purpose of making main channel bass reproduction more accurate. Understanding why this is important means knowing the difference between three different concepts.

a. The signal going to the subwoofer

b. The low bass which is on each main audio channel (left front, center, right front, left surround, right surround).

c. The low bass on the LFE channel.

Most newbies (and I think a lot of pretty well experienced home theater buffs) get confused and think that the subwoofer is used purely for LFE when it actually should also be used to help the other channels reproduce the low bass in the main channels. Indeed, it is possible to have low freq effects carried completely on the mains and nothing on the optional LFE channel.

AVIA is designed to get the highest fidelity out of the main channels - the channels which carry the vast preponderance of sound. By placing the low bass test information solely on the main channels, one is able to isolate and check the bass management of each channel and ensure that all are being appropriately handled in a system.

The setting of speaker size and bass management tremendously affects how bass is handled for each channel. Speakers set to "small" have their low bass routed to the bass output channel (s) which can be either just the subwoofer , the "large" speakers or some combination of subwoofer and large speaker depending on how the receiver is set up.

We highly recommend setting all speakers to "small" because the very very low bass content down to the 20's Hz simply is not as well reproduced by most main speakers as a dedicated sub. Even if one has powered subs inside the main speakers, room placement of those speakers is rarely if ever the best location for bass reproduction. By setting the speakers to "small" you give each speaker a chance to excel in what they do best.

If a speaker is set to "large" its low bass content will not be sent to the subwoofer output. Remember this! AVIA's subwoofer tests are on the main channels. If a particular channel is set to large, then that channel's AVIA test tone is not routed to the subwoofer (just like low bass on that channel is not routed to the subwoofer). This means that the AVIA subwoofer test behaves exactly the same way as live material to be played back on that channel and you can examine that behavior to learn how real material behaves. This also means that playing AVIA subwoofer tests for a channel set to large produces nothing on the sub.

Speakers set to "small" have their low bass routed to either the sub and/or "large" speakers depending on how you have set up the processor to handle bass. AVIA subwoofer tones in channels set "small" behave exactly the way regular bass material in that channel does.

So keep track of how you set your speakers and bass management. AVIA's signals will be routed exactly that way.

It is frequent for people to find that low bass in their various channels is not routed in ways they previously expected. Listen to what the AVIA tones do and you'll discover what is actually happening.

During calibration of your subwoofer level, you usually don't have an ability to independently adjust the strength of bass coming from each main channel. This can mean that you find the SPL reading of subwoofer tests vary depending on which channel is being tested. The most common reason for this is a difference in how the bass is being processed (one channel is large while the other is small). Since you can't independently adjust each, it is reasonable to either average for the front three channels or simply concentrate on getting the front channel right since that one carries the most work in a movie soundtrack.

If nothing comes out of the subwoofer during AVIA tests, it's most likely because all the speakers are set to "large." That prevents routing of low bass in all the channels to the subwoofer. Only the LFE channel would play out of the subwoofer.

The LFE channel is normally not independently calibrated. Some systems allow you to set things between -10 dB and 0 dB (normal). Ordinarily, leaving the LFE at 0 dB gives good results once the main channel bass has been calibrated.
If LFE must be independently calibrated, use the Low Freq 6 Channel Sweep in AVIA (Title 6 chapter 29). This test has a discrete LFE channel signal to verify that LFE level is correct relative to the other 5 channels of bass content. All should read the same SPL.

(For the overly knowledgeable ... the LFE signal is already pre-compensated -10 dB in intensity so it yields the same SPL as the other channels if LFE gain is at 0 dB. No need to worry about the 10 dB playback boost, it's been accounted for)

Getting the subwoofer to main channel sound pressure levels correct is only the beginning. There is a critical overlap frequency range for each channel which is around the crossover frequency. At those frequencies both the main and subwoofer are involved in creating sound simultaneously. Proper blending of the mains and subwoofer requires that the sound from both subwoofer and main speakers be in phase. Otherwise the main speaker and sub cancel each other out in that frequency range and one creates a hole in overall system frequency response.

AVIA allows detailed testing of response at the frequency crossover range for both phase adjustment and frequency selection. This can be done for each of the main channels, but usually getting it right for the center speaker is sufficient if you have already correctly positioned the left and right front speakers to be in phase with the center speaker.

The low frequency phase tests in AVIA have acoustic energy throughout the usual bandpass region. If the subwoofer is out of phase with the speaker channel being tested, partial cancellation of some frequencies will occur and the sound will tend to deemphasize some frequencies in the test tone. Set phase of the subwoofer to make the sound have the widest audible range of frequencies. It is impossible to do this alone. An assistant is required to flip the phase control while you listen for this to work correctly. It simply takes too long to walk up to your sub, flip the phase, and return to your seat. Instant A/B comparison is needed.

Lacking an assistant, you can use your SPL meter by positioning it at your normal head position. Note the SPL reading as the test tone is played in each phase. Select the phase with the higher reading as that is the one with the least overall cancellation of sound between the two speakers (main and subwoofer). If your sub has a variable phase control rather than a 180 degree switch, slowly adjust the phase to maximize the SPL reading. At that point the sub and main speaker are at best phase coherence.

If you note little or no change as phase is adjusted, make sure that the delay or distance settiings for all your speakers are correct. If they are grossly wrong, the system may be delaying one signal so far that it will never come into phase.

The choice of crossover frequency is often fixed at 80 Hz. Some pre/pro's or subs have an adjustable crossover. The warble test tones in AVIA help you find a good crossover point. The tests waver up and down in frequency but not in amplitude. They sweep through the crossover range and well below. The warble effect allows the signal to act as its own comparison level. Bass response is often spikey in a room with small changes in frequency making a large change in response. The warble lets you detect unevenness more easily. If you hear a big appearance/disappearance of the test tone, then the warble is sweeping through a frequency range with a large inequality in response. Play the warble tone and adjust the crossover freq to make overall response as flat as possible during the first (higher freq) portion of the test. That should be the portion which is affected by the crossover.

It may be necessary to redo phase after adjusting crossover frequency. The two controls will interact. Once crossover freq and phase are adjusted, go back and redo the subwoofer level adjustments. They will also be affected.

As you can see, AVIA was designed to accomplish a much more comprehensive subwoofer adjustment than previous calibration discs. The end result is better integration of the subwoofer with the main speakers and reduction of the "separate" subwoofer sound. Unfortunately, many users expect a quick and dirty method. You can indeed do that with another disc, but should you short thrift your hard earned equipment that way?. We chose to provide a more complete tool, and the end result is better subwoofer integration, but it takes time and forces users to discover what truly is happening to their bass.

I hope this helps people realize why we didn't oversimplify and duplicate the test tone on both the LFE and main channels at an arbitrary ratio. Doing things the way we did in AVIA requires greater understanding about your equipment, but ultimately yields more accurate calibration and enlightening information than other means.


------------------
Guy Kuo
www.ovationsw.com
Ovation Software, the Home of AVIA DVD

[Edited last by Guy Kuo on September 06, 2001 at 02:46 PM]
Unquote

Hope this helped!
SP

Sonnie,

Wow, great stuff! Time to get the disc back out and play with some of the tones I didn't bother with initially...

Reference Mr. Kuo's general recommendation to set all speakers to small because "most" mains can't reproduce the lows as well as a dedicated sub, I couldn't agree more. But the key word is "most." Thinkly's mains have 12" woofers, and mine have 15"! They have no problem reproducing better bass than any sub my budget could handle (grin).

Which leads to my next comment: Since my setup currently uses no dedicated sub, all my low frequencies are going to my Large speakers (the two mains and the surround two satellite-sub combo). This set me squarely on top of Mr. Kuo's general remark that "you usually don't have an ability to independently adjust the strength of bass coming from each main channel." But that's an easy situation to fix. As I keep preaching, buy an equalizer! Piece of cake.

Thinkly, check out the section of Sonnie's post about phase alignments. Note where it mentions specific drop-outs of certain freqencies? That's another possible cause of your frequency sweep question in your initial post. I still tend to think my original guess about your room's acoustics is the culprit, though, since the differences appeared between the left and right channels rather than across all speakers.

-Bruce

Bruce,

I had a pair of Snell B Minors (which I just sold) that had non powered side firing 12's. I could never get the bass I needed no matter what I did. The big subs in mains are sometimes hard to locate in the room for the best response (especially in my case where I could not move them around). I really have no choice but to use a powered sub due to the fact I have to have narrow mains because of space limitations.

In several reviews I've read (from the more reputable reviewers IMO) on large mains with large powered subs included in the mains it appears that in many instances with good mains they state the mains can handle the low end without a separate powered sub, but they also stated that adding a separate powered sub, they could tell a difference. Of course that might be a matter of opinion.

I would strongly recommend the BFD(Behringer Feedback Destroyer) equalizer at a street price of $130 or so. It has 24 bands of equalization and is the most flexible eq I have found. I don't own one but will very soon. Do a search on reviews for this eq and you should find it is the eq of choice for many home theater systems. Keeping in mind that a "dip" in response "due to room acoustics" can usually not be tamed with an eq but rather only by moving the speaker to a different location ...sometimes only inches at a time. "Peaks" are easier to remove with the eq though. If you can position the sub or mains where you only had peaks then the eq would be a great tool. Unfortunately the BFD only comes in silver, but you could hide it possibly, that is if the rest of your system is black.

SP