AVM-20 calibrated bass sounds wrong

Discussion in 'Archived Threads 2001-2004' started by Brian Gentry, Dec 10, 2002.

  1. Brian Gentry

    Brian Gentry Agent

    Joined:
    Sep 22, 2002
    Messages:
    36
    Likes Received:
    0
    Trophy Points:
    0
    Shortly after getting my AVM-20, I went out and bought the trusty RS analog SPL meter. I used it to set the levels of all of my speakers, including the subwoofer.

    Every time I changed a parameter, I recalibrated and made sure that all channels were at the same level. This produced pretty good results with movies, although I found that the surrounds didn't seem quite as prominent as I expected them to be. I chalked this up to my surrounds being dipoles and the physical characteristics of my room working against me.

    So, a few weeks ago, I read an article about bass management and decided to change my mains to be "small" in the AVM-20 and cross them over at 60 Hz. My mains are Paradigm Studio 100s, so their bass performance is quite capable. I set them up as small, ran the test tones and recalibrated. I made only some very minor adjustments (less than 2 dB).

    A few days later, I started listening to CDs on my system. ... and I hated every CD I listened to. As I listened to CD after CD, I thought "these are simply *horribly* recorded. They are nearly unlistenable." After I got to the 4th or 5th CD, I put two and two together and checked the configuration of my speakers. I had forgotten about having changed my mains to be "small". I adjusted the configuration to large mains and listened to another CD. Low and behold, I had *great* sound again! The missing bass, that was making every recording sound thin was back in spades. The fatiguing, beatless, lifeless sound I was getting was the sole result of not nearly enough bass in the reproduction.

    I was puzzled by this, as I carefully calibrated the subwoofer levels with the AVM-20 internal test tones and the RS SPL meter. This made me wonder about DVD movie sound as well. After all, even with mains set to large, the level of the subwoofer controls the level of the ".1" bass channel.

    So, I changed the mains back to small, put in a CD with fairly intense bass that I am *very* familiar with and started adjusting the sub level. I did this, not from the "levels" menu, but from the subwoofer "tweak" button. I adjusted it to +7 dB and did some listening. That was a little bass heavy. Back down to +6 dB provided a much closer to "real bass" level. Music now sounded fairly well balanced, compared to the mains being set to large.

    So, on to movies. I played a variety of bass heavy scenes, including the opening sequences of AOTC. The bass is now pretty impressive; much more than I've heard from my system in the past. This is no surprise of course; I'm sending four times the power to the sub compared to what I've been sending it for months.

    I'm left with a dilema though. I *know* how music should sound. I've listened to countless "stereo" systems over the years and I have a very good feel for tonal balance among other traits. So, I'm pretty confident that my settings of the subwoofer are approximately correct for music. For movies though, I don't have a great frame of reference. The vast majority of information below 60 Hz in movies is special effects. It's much harder for me personally to calibrate, by ear, to the sound of gunfire, or simulated explosions, than it is to calibrate with timpani, kick drum, bass guitar, and other "known" instruments.

    I'm left with some nagging questions: Why is the SPL meter calibrated configuration so obviously wrong for stereo recordings? This effect isn't subtle; It's *glaringly* obvious. Does the AVM-20 have some different behavior with stereo sources than with 5.1 sources? I.E., is the SPL meter based calibration reasonably accurate with 5.1 channel sources, but way off for 2 channel sources? Is my SPL meter simply broken? Is the AVM-20's bass management broken in some way?

    Any insight into this will be greatly appreciated.

    Thanks for reading.

    Brian.
     
  2. Michael Mohrmann

    Michael Mohrmann Screenwriter

    Joined:
    Dec 30, 2001
    Messages:
    1,394
    Likes Received:
    0
    Trophy Points:
    0
    Brian,
    Okay, where to start? This could be happening for a lot of different reasons. Here are some suggestions.
    • Make sure that the batteries being used in the RS meter are fresh. I know, it sounds rather obvious, but some people have miscalibrated their systems because of an old/defective battery.
    • When initially calibrating your system, make sure that the individual speaker levels are all 0.0dB before using the test tones. These are what you referred to as the "tweak" settings and can be adjusted either by remote or with the small buttons near the Master Control knob. These levels also can be different by DTS, DD and the stereo DSP modes, so make sure they are 0.0dB for each type of source.
    • Switching the mains to "small" means that the subwoofer is playing the low bass. If the sub is not in an optimum location, you could be losing bass compared to your mains only (Studio 100s are good at bass output).
    • I believe you are using software version 2.0x. If so, you may want to check the subwoofer phase and polarity settings in the Advanced Settings Menu, 4h, items f and g, described on page 48 of the AVM-20 owner's manual. With the subwoofer active, these settings may be affecting the output to the subwoofer with respect to the mains.
    Be aware that the bass in DD5.1/DTS movies is not a good calibrating point because the special effects tends to be overblown, IMHO. Your interests are similar to mine and my wife's. Calibrate your system for music, adjust it (via the "tweak" levels) for the movies.
    Maybe one of my ideas will help out. Good luck. [​IMG]
    Michael
     
  3. Tom Camlioglu

    Tom Camlioglu Stunt Coordinator

    Joined:
    Aug 2, 1999
    Messages:
    145
    Likes Received:
    0
    Trophy Points:
    0
    I would agree with Michael's post along with one more thing to add:
    If you set the THX Setup - THX-Ultra2 Sub to "On" - you will notice a difference in the bass output as either a boon or bane.
    Placement (and capability) of the Subwoofer is crucial.. "if" you have turned this option on!
    Tom[​IMG]
     
  4. Brian Gentry

    Brian Gentry Agent

    Joined:
    Sep 22, 2002
    Messages:
    36
    Likes Received:
    0
    Trophy Points:
    0
    Thanks for the replies. To Michael's points:

    1. The battery meter on the SPL meter is in the "red" zone of the meter, so I'm pretty sure the battery is ok.
    2. I'll have to double check this with some experimentation, but I don't think the tweak controls are active when you are in the levels calibration menu. In any case, I normally keep all of the tweaks at 0 dB.
    3. I think this suggestion has a lot of merit. More details below.
    4. I'm using advanced settings, but the phase is 0 and the polarity is normal. This should only affect bass at or near the crossover frequency, but it could make a difference.

    I did more listening last night using music (Alice and Chains "Jar of Flies" to start with) and solidified a feeling I had in my initial testing. Namely, the bass output from my subwoofer is quite lacking in the upper bass range from about 40 Hz up. This is with mains set to small, xover at 60 Hz, sub at "calibrated" level, and sub tweak at +6 dB.

    With these settings the bass sounds a little "slow". It lacks punch, has lots of very low output, and seems to be missing middle bass guitar notes and the impact of kick drum.

    I'm guessing that my subwoofer placement and/or the interaction between my mains and my subwoofer are the culprit. I'm hoping to correct this either by changing the xover settings, or moving the sub. Now the challenge is to find out what the response really is. I'm either going to use test tones, the meter, a spreadsheet, and the correction table, *or* a computer program like EFT.

    EFT looks really good, but it also looks like it's going to require some serious effort to set up and use. This weekend I'll devote some time to one of these methods.

    Anyone here have a suggestion on how to best find out the response of the sub and mains, so I can change the xover and levels to make it as good as possible?

    Thanks,

    Brian.
     
  5. Dennis Oblow

    Dennis Oblow Stunt Coordinator

    Joined:
    Apr 26, 1999
    Messages:
    143
    Likes Received:
    0
    Trophy Points:
    10
    Real Name:
    Dennis
    Try setting the crossover to 80 (THX setting) instead of 60 and see if that improves your bass response.
     
  6. Douglas_H

    Douglas_H Stunt Coordinator

    Joined:
    Nov 29, 2000
    Messages:
    183
    Likes Received:
    64
    Trophy Points:
    110
    I guess my question is why do you feel it's necessary to set your main speakers to small?
    Studio 100s are designed as full range speakers and should be configured as such.
    I'm not surprised that it sounded weak.
    The whole small vs big thing is for movie soundtracks.
    Are you running cables from your L/R pre-outs to the sub in addition the LFE out?
    I'm guessing you just have the LFE out running to the sub.
    Is your AVM-20 configured to send ALL low frequency from ALL inputs to the sub or is it just working on X.1 soundtracks.
    My suggestion would be to optimize your system for music and the rest will take care of itself.
    But I think you have already realized this.
    Remember, Dolby & DTS use lossy compression and are not in the same league as well recorded music.
    Sounds like you have a nice system.
    I'm saving for the AVM-20 myself.
    HTH
     
  7. GregLee

    GregLee Stunt Coordinator

    Joined:
    Aug 13, 2002
    Messages:
    103
    Likes Received:
    0
    Trophy Points:
    0
    I've been reading postings on bass calibration for several months now, and I've noticed quite a few accounts of going through the SPL meter procedure which wind up with a sentence to the effect: "Then I turned up the sub until it sounded good."
     
  8. AaronBatiuk

    AaronBatiuk Second Unit

    Joined:
    Aug 23, 2002
    Messages:
    333
    Likes Received:
    0
    Trophy Points:
    0
    Speaker calibration can be a painful experience. Unfortunately, as you have discovered, just picking up an SPL meter and turning on the test tones provided by the receiver, will not give good results. Here are a few tips:
    1. Set the crossover for all speakers to the same thing initially. I use 120 Hz. This is regardless of whether the speakers are large or small, or even if you don't use a sub (as I don't). Also, make sure the sub is set to on/yes in the receiver, and turn off or unplug the sub while doing level matching for the other speakers. Doing this ensures that the same signal (read: same level of bass!) goes to all speakers, so that more/less bass output from any given speaker will not skew your SPL measurements. Only after measuring and matching all speakers, can you adjust the crossover (or even disable it), at your discression. Note that if you take another measurement after adjusting the xover, the SPL readings may be quite different. Don't worry... it's just the extra (or lesser) bass that is skewing the measurement; all the other frequencies are untouched, and are still matched in level. When done, turn-on/plug-in the sub, or set it to "no" or "off" as appropriate for your setup.
    2. Use the equalisers to match the tonal characteristics of your speakers. Some receivers (e.g. high-end Pioneer) have automatic equalisation, using a microphone, to do this for you. Others (e.g. Sony) have a very flexible EQ to allow you to do adjustments yourself. In either case, you should (almost) always make use of it. Since the speakers themselves are almost always different, and speaker placement of various speakers in the room is by definition always different, you will need to adjust the tonal character of each speaker to get a seamless transistion in the soundfield. Note that speaker levels need once again to be matched after making adjustments to the equalisers.
    3. Set the subwoofer level with a stereo source, not DD/dts. You may have noticed that a good subwoofer level for DD/dts sources is not necessarily a good level for 2 channel sources (music). Set the sub level using a 2 channel source, making sure that the receiver is in a mode that will use the crossovers on the mains and will use the sub ("analog direct" mode on Sony's for example will not). After setting the sub to the approriate level for a smooth bass transition from main speaker to subwoofer, you can adjust the LFE channel level for DD/dts sources. This will allow you to tailor the bass in DD/dts movies vs. other sources. On Sony's this is a parameter called "LFE Mix", on other receivers it should be somehting similar. If you don't have such an adjustment available, well, your receiver/prepro is somewhat less flexible that it could be.
    4. Get a good Test CD/DVD. Try to get one with Pink Noise in 1/3 octave bands, useful for adjusting subwoofer placement, crossovers, and equalisers. Using (bandpass filtered) pink noise instead of discrete tones gives better measurements as it helps to reduce the resonances and standing waves that can occur when using discrete tones. Make sure the test disc also has a number of multi-channel (DD and dts) test signals.
    5. Trust your ears. If it just plain sounds wrong to you, then you should trust that instinct. All this theory and measurement and tweaking is great and all, but what we are really after is something that sounds good. SPL meters and Test discs are good tools, but so are your ears.
     
  9. Brian Gentry

    Brian Gentry Agent

    Joined:
    Sep 22, 2002
    Messages:
    36
    Likes Received:
    0
    Trophy Points:
    0
    Douglas,

    I set the mains to small for a few reasons. It wasn't designed to be a permanent solution; just an experiment. The main reason I decided to try this was the fact that my sub has bass response that is lower and louder than my mains are capable of. Initially, I had set up my system with mains set to large, center and surround set to small, sub on, C and S crossed over at 60 Hz, and sub crossed over at 40 Hz.

    By using this unusual arrangement, I was hoping to send all bass below 60 from C and S to the sub, get full range sound (and bass) from my mains, and augment the bottom end of my mains with the sub, since it has response (according to the literature) down to 14 Hz.

    After reading Brian Florian's article on bass management, I realized that my logic was flawed, and that I'd miss anything in the LFE channel between 80 and 40 Hz with this configuration. At the same time, I wanted to see if my sub would do a good job on bass from the mains and again, potentially extend their response to 14 Hz with greater output than my Studio 100s are capable of. So, I then set all crossover points to 60 Hz and set the mains to small.

    Next, you ask about my connection to my sub. Yes, I've only got the sub out running to the subwoofer. However, the AVM-20 will send all bass from the mains, below the mains crossover frequency (60 Hz in my case), to the subwoofer output. That's what bass management is all about; directing bass from speakers that are "small" to a subwoofer that will play it for them. In case anyone wants to get technical about this, yes, I know that the crossovers have individual slopes and that not strictly *all* bass below the crossover frequency is filtered out. Just trying to keep it simple.

    Believe it or not, you can get audiophile quality bass from a combination of mains and a well set up subwoofer. I've previously always done it by ear, and never had such sophisticated crossovers in a home system to work with. I guess I'm finding that getting really excellent sound requires more work than in the "good old days", when I didn't have equipment this nice.

    Finally, the two reasons that I'm bothering to pursue this any further:

    1. If two channel music that I'm familiar with sounds very lacking in bass, then isn't my subwoofer level "off" for all sources? I.E., don't I have the subwoofer level set way too low for movies as well?
    2. Since I've seemingly got a dip in response between about 40 and 60 to 80 Hz with music, aren't I missing that area with movies as well? I think I'm probably missing a lot of the bass that the center and surrounds should be getting (if they were large) and a lot of bass in the ".1" LFE track of 5.1 DVDs.

    Given these two things, I'm going to do some measurements and hopefully be able to correct this by changing crossover settings. If not, I'll try moving the sub around as well.

    Thanks again for all the input.

    Brian.
     

Share This Page