SVS Bottoming Out And Strange Crackling On JPIII

Discussion in 'Archived Threads 2001-2004' started by PhilS, Dec 23, 2001.

  1. PhilS

    PhilS Stunt Coordinator

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    I just recently got a SVS 16-46 PC, and tonite I played JPIII. I think the sub bottomed out on scene 12, just when the huge dinosoar attacks. I heard a sharp, deep clack or smack, and it came from the corner where the SVS is located. I'm wondering if this is a particularly taxing scene for a subwoofer, because I have not had a problem with the pod scene on Phantom Menace, U-571, SPR, etc. In fact, I was playing the movie at 7.5 db below my reference level of 75 db, and my subwoofer setting on my TAG pre-pro is already at -9.5 db, so it seems kind of strange that the sub would still bottom out. I tried it twice and it happened both times, but when I turned the volume down a little more, it did not bottom out. Has anyone else had a problem with their SVS handling this scene?

    Also, throughout the movie, there was crackling sound coming from the main speakers (M&K 150THX) on various scenes. When I played the movie through another system I have (M&K 750's), I could not hear any such sound. I have never heard this sound on any other DVD's. When I played parts of the movie again, it appears that only certain scenes have this problem. I assumed at first it was a bad DVD, but I don't understand why I only heard it on one system. Does anybody have an idea of what this crackling sound might be caused by?
     
  2. KevinHunt

    KevinHunt Stunt Coordinator

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    Phil, I'm not real sure just reading through what you have posted, but I played JP3 through my system(M&K S150THX, and dual SVS 16-46CSs and Samson S700) with no crackling and/or bottoming of the sub. How big is your room and how is your sub calibrated relative to your mains? Ron and Tom say your sub headroom will dissipate fast if you are running your sub hot(i.e. 6-10dBs over your mains) and especially so if your room is quite large. You could try bringing your sub back down to about 72dB, which would be about 75dB actual considering the low frequency rolloff of the RS sound meter. This would give you a little more headroom and allow you to play at roughly the same volumes you like w/o the bottoming. This is a suggestion I saw posted from Ron or Tom, can't remember which. As for the crackling in your mains, I'm not sure what that could be. Maybe your mains amp clipping? What are you powering your mains with?
     
  3. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Phil,
    Kevin's correct.
    the preamp's subwoofer volume leveler display doesn't mean a whole lot. You need to run a speaker calibration setup menu.(either built into your preamp,or using AVIA or VE).
    Using a SPL meter...set all speakers including the subwoofer to the same output levels(while holding the meter in your key listening seat).
    If you have any more problems with the subwoofer...be sure to let me know(either in this thread....or by emailing [email protected])
    Get it calibrated ! [​IMG]
    TV
     
  4. PhilS

    PhilS Stunt Coordinator

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    I did calibrate using the test tones in my subwoofer. The mains and surrounds are at 75 db, which matches up precisely to 0 on the TAG's main volume control. I was running the sub hot at about +4db per the recommendation in the SVS manual. I'm not an expert, but I don't believe that the subwoofer tone from my pre-pro is so low that a 3db adjustment is approproiate on the RS meter. It sounds like it's in the range of 55-65 Hz, which on the charts I have seen would mean about a 1 db adjustment to the RS meter. In any event, as I said above, I had the TAG's main volume at -7.5 db, so it was -7.5 db below 75 db. That's why it struck me as odd that I had a problem.

    As for room volume, I have about 3500 cubic feet, I think. And I am running a second sub also, which is an M&K 125 MKII, so the SVS has some help.

    I suppose I will try calibrating with the Avia disk to see if that changes anything. Perhaps I will not run the SVS hot either to see if this makes a difference.
     
  5. Lewis Besze

    Lewis Besze Producer

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    Phil the test tones aren't a single frequency,but rather a "wide band" tone,and in case of the LFE[sub] it could be from 20hz up to the crossover point you have selected 80hz(?).

    So the 3db deduction is about right,and yes JP III is a sub "killer".
     
  6. ChrisSk

    ChrisSk Extra

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    What software version do you have in your Tag? The AV32R had a bug regarding DD soundtracks flagged as EX encoded before version 3.40.10, version 3.5 is due for release later today BTW. JP3 and Pearl Harbour* are among the first titles encoded with a flag indicating an EX track and are causing problems for some decoders and recievers, thankfully the Tag's software can be updated [​IMG]
    Of course, that's a moot point if you were listening to the DTS track!
    *Pearl Harbour's EX flag is a mistake, it's flagged as such on some of the soundtracks (R2 English, R1 French and others) but it was never recorded as EX.
    Edit:
    For your bottoming out problem you could try using the sub limiter setting in the subwoofer setup menu of the Tag. I think there's a test tone output when you change this in the setup wizard if you're having trouble finding the right level.
     
  7. Ariel

    Ariel Stunt Coordinator

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  8. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    >>>I did calibrate using the test tones in my subwoofer. The mains and surrounds are at 75 db, which matches up precisely to 0 on the TAG's main volume control. I was running the sub hot at about +4db per the recommendation in the SVS manual.
     
  9. PhilS

    PhilS Stunt Coordinator

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    Thanks for all the replies. After further testing and calibration, here's what I found out.

    First, the crackling is only on the Dolby Digital track. The DTS track plays fine. Second, I recalibrated and lowered the subwoofer level so it is only 2db above the level of my mains and surrounds. This time the SVS did not have any problem with the scene on JPIII that it had a problem with before, even after I turned up the volume on my pre-pro from -7.5 db to -5 db. And there was still plenty of bass to go around, which I confirmed by also checking it on the pod scene in TPM. I think Tom's explanation about how close the sub is to reference when it is run hot at +4db at close to reference listening levels explains the earlier problem. On the other hand, the problem I had with the sub bottoming out was only on the Dobly Digital track that has the crackling, so who knows if that was part of the problem.

    In any event, after turning down the subwoofer output 2db, I found that I still have plenty of bass, and I also found that the few peaks and valleys I had in my subwoofer frequency range evened out bit. I have listened again to several music selections (which I listen to at 2db lower than movie level) and several movie scenes and everything really sounds great. There's nothing like feeling bass from your listening position in a movie like TPM or JPIII, as opposed to just hearing it. It really makes the whole movie. Thanks again Tom and SVS.
     
  10. SVS-Ron

    SVS-Ron Screenwriter

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    That's great news Phil.

    Still, with gear with so many adjustments like you have, I strongly recommend you get a test disk like Video Essentials, or Avia. Using a sound meter (the meter is CRITICAL, you simply can't do this by ear) and the disk as your source, you can be sure your system is calibrated from begging to end. I'll bet a few minutes of this and you'll be even more pleased with the results.

    Internal test calibration tones are a good start but they really should be verified with actual program material on these disks.

    Happy holidays!

    Ron Stimpson
     
  11. PhilS

    PhilS Stunt Coordinator

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    Ron, I did use Avia to double check the settings with my pre-pro, and everything checked out. The one problem with Avia (unless I'm missing something) is that it only has test tones for one pair of surrounds. So I need to use the pre-pro test tones for my surrounds, because it has separate tones for the side and rear surrounds.
     

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