PB-2plus Help

Discussion in 'Speakers & Subwoofers' started by Ernesto_G+, Sep 11, 2004.

  1. Ernesto_G+

    Ernesto_G+ Extra

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    Every since I got this sub something has always sounded like its missing. It just doesnt sound right to me, occastionally It would surprise me in certian scenes of a movie but thats it. I dont think its that great of a subwoofer. What Im trying to figure out is if theres something im missing thats making me loose out on hearing great bass this sub should be playing. For example my sub. cable isnt of good qaulity, or my reciever could be to blame but what ever the case I want figure it out.


    Right now My set-up consists of:
    Kenwood Generic Reciever
    Polk 7200 set
    pb2 plus subwoofer

    Im thinking of buying the outlaw pre/pro special
    upgrading the speakers,(axioms or rockets)
    and getting a better sub cable.
    The first thing on my list of upgradeing is the receiver. I plan on getting it sometime this month. Hopefully that will do a major improvment on channel seperation and help the sub. If that doesnt work Ill order Better Cables from SVS thinking the wire is to blame. And last but not least upgradeing the speakers. Im not trying to bag on svs just want to figure out what im missing. I notice when I get farther away from the sub it sounds better. My room is an L shaped room with 4 oppenings. The sub is placed next to the couch next to the main entrance. Thats the best postion I found for the sub but I could be wrong.
     
  2. SethH

    SethH Cinematographer

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    I would put all those upgrade plans on hold for a few moments. I think your problem is calibration. Have you calibrated the system at all? It sounds to me as though you probably have a pretty deep null at your seating area. This happens frequently in odd-shaped rooms. You probably need to play with the placement of the sub and the calibration. Also, make a call to SVS and talk to them about your problems and I'm sure they'll be able to help.
     
  3. steve nn

    steve nn Cinematographer

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    >>or my receiver could be to blame but what ever the case I want figure it out.
     
  4. Doug McBride

    Doug McBride Auditioning

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    Ernesto - I would agree with Seth that it could (and probably is) a calibration issue. You didn't mention that you had done any basic calibration - e.g. setting the sub level with the mains. However, if you were to plot the FR of your room you might be surprised at what you see and it may point out the source of your problem.

    I've got a PB2+ and it has never sounded lacking. However, with some work on calibration and EQing for the room, it shakes the fillings out of your teeth. And, just like you, I can still move around the sweet spot of the room and hear significant variations in the sub level. 'Tis the nature of the beast unfortunately.

    If you were to do a search on calibration and/or frequency response, you will find a lot of good material on how to go about checking and correcting your room. You'll also see how critical having your sub calibrated is to get the most out of it. There's also instructions in your owner's manual as part of the set up instructions for the sub on how to do a basic calibration

    Doug
     
  5. George_W_K

    George_W_K Screenwriter

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    Unless your expectations are unGodly high, something is amiss here! I'd like to throw in another vote for calibration being the culprit, and possible placement too. I say possible because it sounds like you only used your ears. Which isn't necessarily bad, but there have been many threads on this subject where just moving the sub a couple of inches has made a world of difference. What I did to place mine, I put the sub on the couch where I sit (heavy sucker, isn't it?) and then crawled around on the floor with my Rat Shack meter until I had the best readings of the playing test tone.

    This is a back and forth thing too, you have to calibrate, move around, re-calibrate, etc.

    Another thing to consider is how do you have your gain set? If the sub has too large a signal, there's a safety built into the amp to avoid ruining the drivers. I noticed this with Matrix Revolutions, during the Waterball explosion scene. When I played the scene at -5 reference, it shook the heck outta the room. However, when I bumped the volume up to reference, there wasn't any kind of impact whatsoever. This is another reason why calibration is so important.

    It's nice to see you coming to the forums for help as there are a ton of guys here who can be very helpful. Also, SVS has a really great CS department and will help you too, no problem.

    Keep us updated or ask more questions if needed. Good luck.
    George
     
  6. Edward J M

    Edward J M Cinematographer

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    There are common set-up errors that could be causing some problems. Double check all of these things before you try to recalibrate:

    In the AVR:

    1) All speakers set to small.
    2) Crossover set to 80 Hz.
    3) Sub set to on/yes.
    4) Subwoofer Remix (a Kenwood classic) set to off/no.
    5) Dolby Dynamic Range Compression Circuit set to off/no.
    6) LFE (0.1) channel level set to maximum (i.e., unattenuated) value (if the AVR has the capability).
    7) THX (or any other) bass limiter circuits set to off/no.
    8) Subwoofer channel level to -5.

    In the DVD player:

    1) Output set to bitstream (digital output via the digital coax).
    2) Dolby Dynamic Range Compression Circuit set to off/no.

    On the subwoofer:

    1) PB2 to all ports open.
    2) Tune switch to 25 Hz.
    3) Crossover switch to off.
    4) Set the phase to 0 degrees unless you have the capability to evaluate the FR of the system.

    Subwoofer placement:

    1) First try corner loading away from any permanent openings.

    During Calibration:

    1) Calibrate with Avia.

    2) Don't use DVE; it has a 10 dB subwoofer calibration tone encoding error.

    3) Since Avia relies on redirected bass, I have found that the amount of bass each speaker contributes to the sub tone is highly dependent on its room location, its inherent bass capabilities, its proximity to the subwoofer, and the xo frequency you have selected.

    For example, the left main channel in my system is several dB higher than any other channel on the subwoofer test tones. If I selected the left main channel for sub calibration, it would result in undercalibration of the sub.

    The best way is to run the Avia sub test tone for each speaker channel and note the results. Pick the one that seems most representative of the average and go with it for final sub calibration.

    While bass tastes will vary, most prefer the sub 2-3 dB hot for HT, and flat for music. Because it is C-weighted, the RS sound meter reads about 2 dB LOW on the typical subwoofer rumble tone.

    So an average reading of 85-86 dB on the meter is about 87-88 dB in reality - or 2-3 dB "hot". This would be a good starting point for HT.
     
  7. Kevin C Brown

    Kevin C Brown Producer

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    Ed- Good list! You might want to keep evolving that and put it in your signature too. [​IMG] (Maybe even include a section on how to set the phase correctly.)
     
  8. MikeNg

    MikeNg Second Unit

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    I agree with Kevin, Ed, Nice little checklist.

    Nothing new to add - it's all been said already. Let us know how it goes.[​IMG]
     
  9. Edward J M

    Edward J M Cinematographer

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    It's tough, even with Avia. Say for example:

    1) the subwoofer is placed near the left main
    2) the left main is vented tower with an F3 of 40 Hz
    3) the pre/pro BM circuit uses a 12/24 filter network @ 80 Hz

    The user runs the Avia subwoofer rumble tone (which sends bass to both the speaker and the sub) for the left main channel. He adjusts the phase until he gets the highest SPL reading on the rumble tone.

    What has he just acomplished? He probably created an emphasis in the 50-80 Hz region because the shallow 2nd order roll-off of the left main tower in the 50-80 Hz region is now maximally reinforcing with the subwoofer's response.

    Is maximum SPL with the phase control necessarily a final objective?

    Or is obtaining the flattest FR, even if it means using the phase control to induce some cancellation with the subwoofer in the 50-80 Hz region?
     
  10. Kevin C Brown

    Kevin C Brown Producer

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    Ed- Here are my three *different* ways of checking for phase:

    1) The Chesky DVD-A/V test disc. This is the easiest disc I've found for tests by ear. (I never liked Avia for phase to the sub.) You can also use a sound level meter for optimization. It plays tones in phase and out of phase back-to-back for really easy comparison.

    2) A discrete test tone disc CD. Play the tone at the crossover, then adjust the phase for max SPL. (And slightly above and slightly below.)

    And... to address your concern about flat freq response vs the best phase:

    3) A PC, ETF5, and a Radio Shack meter. You can plot freq response through the crossover. And ironically, I have the phase *not* set to the theoretical best setting, but to the setting for best, flattest, freq reponse. [​IMG]
     
  11. Edward J M

    Edward J M Cinematographer

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    You're cooking with oil, Kev. [​IMG] IMHO, that IS the best setting for the phase control.
     

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