A Possible Solution To "Low" LFE on 47Ai/45A

Discussion in 'Archived Threads 2001-2004' started by Ron Newsome, Dec 28, 2002.

  1. Ron Newsome

    Ron Newsome Stunt Coordinator

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    I ran some tests on the 47Ai using its internal test tones and the test tones from Cheskys Ultimate DVD Setup Disc. I also switched between combinations of Small and Large Speakers in the 47Ai and in my 49TXi, and Direct/Adjust Modes on the 49TXi. To make a long story short, I think the internal test tones of the 47Ai/45A is at fault. Anyway here it is:
    http://www.avsforum.com/avs-vb/showt...postid=1683221
    I hope this is of some help to the people here at the Home Theater Forum.
     
  2. Brian L

    Brian L Cinematographer

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    Ron,

    I did quite a lot of testing with the 45A, even measuring the actual voltage coming off of the inputs. With all speakers small sub on, using external DD or DTS test tones, the level is low relative to the mains.

    I would agree that there is an issue with the internal test tones, as they sure do NOT sound very bassy to me; I can buy into the assumption that you will not get a good match using them. In fact, I have an e-mail from Pioneer that pretty much says exactly that. (FTR, I am still in communication with then to fully explain what is happening, and would prefer to keep those e-mails confidential at this time).

    But, here's the rub; You are the 1st poster to use a real DVD-A test tone! Everything else I have done (as well as all others) was with DD or DTS tones (from Avia, VE, Ultimate, etc.).

    In my mind, you have proved what a lot of us have speculated: There is a missing boost in the 45A's BM (and other players) that is normally applied with DD and perhaps DTS. I would further speculate that the DD LFE test tones we all are using are 10dB down from the main channels, because there will later be a 10dB boost in the decoder.

    Further to this theory, many recent Denon Receivers actually ahve a swicthable boost (+15 dB, I think) for the LFE channel when using 6CH inputs.

    Putting this all together says to me that decoders used in universal players (be they SACD +DD/DTS, or like ours all formats) simply lack the boost needed for DD/DTS sources.

    I would further speculate (hey, I am already out on a limb; might as well keep going!) that the DVD-A tones are equal across all channels.

    My system had enough gain available in the sub channel (via the 6CH in Plus the subs level control) to get 85dB across the board. Not everyone can.

    Although I did not need one for this problem, I did buy a ICBM because I wanted my crossover at 80Hz, not 100Hz (I use a THX EQ which assumes 80Hz crossover, so that was the motivator).

    Of course, the ICBM has a +/- 9 dB level control on the sub channel, so that low LFE problem was corrected as well.

    So all that said, I don't think the internal test tones are the be all/end all of the issue. I think the Chesky tones are designed to take into account that the decoders does NOT apply any boost to the LFE/Sub.

    If you have access to Avia or VE, I would be VERY interested to see if you got the same results. If you have a digital voltmeter, you could go one step further and measure the LFE output of the 45A directly. I think you will find that with DD or DTS, the LFE is at about .2 Vdc, while the mains are over 1 Vdc. With the Chesky disc, I bet you will see they are all even.

    BL
     
  3. Lewis Besze

    Lewis Besze Producer

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    Question!
    Why would you need the "boost" if you not gonna use the built in decoders,provided that in DVD-A/SACD mode the sub out is in balance?
     
  4. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Brian, what does this "boost" have to do with DVD-A and SACD? For DD/DTS sources I would think you would be using the digital connections anyway.
    And eventhough I used a DVD-A test disc, the test tones were valid and they're the same kind of tones you find on any other test disc.
     
  5. Kevin C Brown

    Kevin C Brown Producer

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    There is no internal test tone for the sub, right? You have to use Avia, VE, S&V's disc, etc. That's how I did it anyway. I only ended up with a 5 dB difference for the sub volume setting between calibrating *through* my pre/pro, vs on the 45a or 47ai.
     
  6. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Kevin, assuming the 45A's Setup interface is the same as the 47Ai, in the Initial Settings->Speakers->Channel Level->Variable Menu, there are some symbols in a column to the right of the numbers representing the speakers level setting. If you highlight the symbol you get a test tone. Highlight the symbol again to turn it off.

    But If I were you I wouldn't you use those tones at all. I've been doing some more research and I think it's white noise and not pink.
     
  7. Brian L

    Brian L Cinematographer

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    I am not saying your test tones are invalid, in fact, they are perhaps more valid then the tones we all have used, since you are the first to use DVD-A test tones.

    I am saying, however, that they are NOT the same as the test tones that I and others have used.

    If you are able to test with Avia or VE, I would very much be interested to see if there is a difference between those and the DVD-A disc. That would answer a lot.

    Further to that, unless you actually measure the voltage output with a meter, as I did to confirm what my ears and SPL meter were hearing, then we are talking apples to oranges.

    Read up on DD decoders, and you will see what I am saying re: an internal 10 dB boost.

    And in my case, I am using the DD and DTS decoders in the 45A; my receiver is and older Pro Logic device.

    I do appreciate what you have done to advance the discussion, but there is still an issue and its NOT, IMHO, exclusively due to problems with the internal test tones.

    BL
     
  8. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Ok Brian, this time I used the Dolby Digital Test Tones on the DVD-V portion of the Chesky Disc. And the results are the same. Sorry. I'm watching Star Wars:AOTC and the Bass and overall sound wouldn't disappoint anybody. I don't need any voltmeters or such to tell me anything. My ears are all I need and they don't lie. I wish you were here to hear I'm what I'm hearing. My 47Ai is set to Small Speakers and Channel Level is Variable.

    L: 2
    C: 1.5
    R: 2.5
    RS: 2.5
    LS: 3.5
    SW: 6

    Receiver is set to Multi-Direct. All BM is done in 47Ai.

    Now I will say this; the only differences I hear are between the Volume Levels of Multi-Ch Inputs and the Digital Inputs. My normal listening levels through the Digital Inputs are -14, but through the Multi-Ch Inputs I have to increase the Volume to -8. If I can increase the individual channels of the Multi-Ch inputs across the board by about 6db, would I be cheating?
     
  9. Kevin C Brown

    Kevin C Brown Producer

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    Well, I think I have figured 2 things out. [​IMG]
    There is no test tone for the sub on the 45a, but there is for the 47ai. (I did not know that.)
    I also figured out, that it seems to me, that the sub out test tone level on the 47ai is too low.
    Oh, also, I am using the analog out test tones even for Avia. I.e., I am using the 47ai's internal DD decoder and going 5.1 analog to an Outlaw 950. No BM in the 47ai, but I am using the 80 Hz analog crossover in the 950.
    I.e., if I set levels using Avia, I adjust my main L + R to 0, I need to set the sub to +5 dB.
    If I compare that to the main and sub test tones on the 47ai, the sub test tone is way too low.
    Ahh, so I reread the thread, and I agree with Ron's very 1st post. Coolness. [​IMG]
     
  10. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Thanks Kevin!

    I'm assuming the 950 does BM on its Multi-Ch inputs, because you say you're using the 80hz crossover in the 950. If that's the case you should have no problem with the 47Ai. And even if the 950 didn't do BM on the 6-ch inputs you still wouldn't have a problem.
     
  11. Brian L

    Brian L Cinematographer

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  12. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Brian said:
     
  13. Lewis Besze

    Lewis Besze Producer

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    Since everybody ignored my question,then let me re-phrase!
    How's is this boil down to the SACD and DVD-A sub out performance? Verdict?
     
  14. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Lewis I personally don't think there's a problem with just the Sub out. The output on All channels are down by about 6db and the internal test tones are crappy? Use a Test Disc (Avia, VE, Home Theater Tune-Up, or Chesky) when setting up this DVD player. That's my opinion.
     
  15. Brian L

    Brian L Cinematographer

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  16. Lewis Besze

    Lewis Besze Producer

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    Thanks I'm in search for a DVD-A/SACD player,but this issue makes me wanna wait and see what else will come out in this price range.The Yamaha,and Onkyo player all based on the 47A,so this could be an issue with'em as well.
     
  17. Ron Newsome

    Ron Newsome Stunt Coordinator

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    Brian said:
     
  18. Kevin C Brown

    Kevin C Brown Producer

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    I don't think the Yamaha is based on the 47a/ai. It has a different MPEG 2 decoder chip. Secrets says it doesn't have the chroma bug.
     
  19. Espen Braathen

    Espen Braathen Stunt Coordinator

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    Most DVD-Audio and SACD players seems to lack the correct LFE gain comparable to the main channels. This is true for the internal 5.1 DD and DTS decoders as well.

    In my experience the output might be as much as -15 dB to low. This is because LFE is missing the correct +10 dB gain as well as scaled down to avoid bass summed in from the main channeles to overload the subwoofer output.

    I.e. the goal is to keep all the six analogue outputs below the standard 2 volt signal level.

    The Denon AVR-5803/AVC-A1SR amplifier has a built in selectable correction for this missmatch.

    Espen
     
  20. Brian L

    Brian L Cinematographer

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    Another bit of anecdotal evidence that, for players that seem to have the low LFE/Sub problem, the cause is lack of boost for DD/DTS sources.

    Until today, I had no DVD-A test software; only DD and DTS. That changed with the arrival of a Telarc DVD-A title; Celebrating the Music of Weather Report. This disc has DVD-A test tones AND DTS test tones.

    My rig (Pioneer 45a with an ICBM, all speakers large + sub on) is set to 85dB across the board with DD or DTS test tones.

    I put the Telarc disc in and cued up the DVD-A MC mix and HOLY CRAP, the bass is ridiculously loud. I went to the DVD-A set-up tracks, and sure enough, the LFE was a good 6 to 8 dB louder then the main channels. I though perhaps they mixed this thing with very strong bass, but how to know?

    Well, I switched to the DVD-V layer, and cued up the DTS test tracks. Guess what? The LFE tone was dead-nutz equal to the main channels. This was without changing anything; just playing the two sets of test tones back to back with my rig set to its DD/DTS levels.

    So, in my way of thinking, this is pretty decent evidence that at least this player does NOT correctly set the DD and DTS LFE levels in the decoder. That's why those with the problem have had to run the gain up for their sub/LFE channels.

    FTR, I can't say that I observed the same behavior with other DVD-A titles. While I do adjust the sub level a few clicks one way or the other to suit the music, there was never as large of a difference as I observed here.

    I may e-mail Telarc and ask if they can offer any insight into why their is a difference but IMHO, its no fault of the software, its the player.

    So, in my case, if I calibrate to the DD/DTS tones, I will need to knock the bass down a ton when I pop in this DVD-A; or vis-a-versa. Thank goodness the ICBM has a sub level knob that makes this a simple matter to deal with.

    I do have a Chesky test DVD-A on the way. I will test with that as well and report the results.

    BL
     

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