Some thoughts...might have something set wrong. (SVS)

Discussion in 'Speakers & Subwoofers' started by ShaunVanSkiver, May 2, 2006.

  1. ShaunVanSkiver

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    ok, so I have been enjoying my SBS-01 with the pb12-nsd for 2 weeks now and i have a quick question about the gain setting on the sub. SVS recommends a 1/4 - 1/3 setting and when I check my speaker setting with a spl thats about where i have it set. I'm also running it a little hot, about 4-5db over. When I'm actually using the system for other media besides test tones and pink noise the sub seems a little weak. More so with music but even with dd5.1 it still seems like it should be louder. Now this is in a small room 13x20 and it does open up at one end into a decent size den, I think it's a 15x15. But the opening is just a door size entrance and I have the sub placed in the left rear corner opposite the opening. Even with me setting the bass/treble on the receiver up around +4 for bass and 0 for treble it's still not much of a difference. I have the speaker levels at about -3 to +1 and the SW level about a -2 this setting puts the SW at 5db over. Now when I turn the gain on the sub up to 1/2 it's like flipping a switch. It will rattle stuff in the garage!!! but when i turn it back down even to the 11 o'clock position it goes into hibernation mode and really doesnt want to react to anything i give it. With music i need it set to about 1 o'clock and movies/tv about 12 o'clock. is there something I'm missing? I have all speakers set to small and x-over at 100, no dif at 80. I'm using the pioneer vsx-72txv. I really would just like a little reassurance that i'm not going to blow the sub with the gain set at 1/2. When I get right down beside the box the bass sounds tight and clean so i dont think I'm pushing it to hard but i dont want to abuse it either....
    One happy SVS owner, Shaun
     
  2. SethH

    SethH Cinematographer

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    I would guess that you have either a null or a deep valley in your FR around a common frequency. You'll want to plot your frequency response using your SPL meter and a calibration disc. Or, if you have a computer with a good sound card, you could use the Room EQ Wizard software which is freely available online.

    If I'm correct about the problem, then your solution could be as easy as moving the sub to a different corner, or a slightly different location. Or, you could end up buying a BFD to equalize the subwoofer.
     
  3. ShaunVanSkiver

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    i have done that too there wasnt any big nulls, nothing more then 5db all the way up to 100hz the problem isn't FR it's the fact that the sub will not play anything with the gain at 1/4 -1/3 setting. the driver will barely move let alone make any sound. do you know where i can get a electronic copy of a FR chart where i can input my data? I'm not that familiar with excel to make my own.
     
  4. SethH

    SethH Cinematographer

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  5. ShaunVanSkiver

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  6. douglas-b

    douglas-b Stunt Coordinator

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    SVS recommends you "start" your calibration at 1/3 and adjust from there. My receiver is at -6 on the SW and the gain on my sub is almost at 1/2 When I was finished.

    (When I started I had it at 9:00 position and turned it to the right.)
     
  7. John Garcia

    John Garcia Executive Producer

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    1/2 gain is pretty much normal. I had to run my PB-10 at 60% also. You may need to adjust the sub's level in the receiver also; you may have it set too low. The two are interactive, and you need to adjust each to find the right blend between the two adjustments that gives you what you are after. I start with the receiver's sub level at zero and see what ref cal requires the sub to be set at. If it is a lot higher or lower than 1/2 gain on the sub, I adjust the receiver up or down to get what I'm after. I normally advise against using the bass and treble adjustments.
     
  8. ShaunVanSkiver

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    ok so the 1/2 setting is normal. I really only use the bass/treble setting for music...kinda takes the brightness out of it. anyway here is my FR. it seems to be alright any opinions?

    [​IMG]
     
  9. SteveCallas

    SteveCallas Second Unit

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    Well you're 30db less at 90hz compared to 50hz, and a 6db difference equates to twice as loud [​IMG] This means you will be missing almost all of the bass that is "punchy", while you will have plenty of the bass that is room shaking. I have heard of this complaint with the PB-Ultra, so it may be inherent in the design of their drivers, but I'd experiment with moving the sub in other locations. If that doesn't work, get a BFD and apply cuts to the frequencies below 75hz to even them out to your 90hz output.

    The reason your chart looks flat now is because your db range is 0-120db. Compress the range and you will get a better picture.
     
  10. SethH

    SethH Cinematographer

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    At what frequency does your system cross over to your sub? That's a pretty nasty dip there from 70-95. That's probably where you're missing so much. At 85Hz you're down almost 26dB from your level at 55Hz.

    If you can swing a BFD, you might really benefit by cutting back on the 50-55Hz range and giving a little boost between 75 and 95.
     
  11. ShaunVanSkiver

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    with this run i had the x-over at 80. my receiver has 3 filters for the SW level. If i could make heads or tails out of the owners manual i might be able to play with it. From what i can tell i can change the db at three different levels low mid high. what your saying is i should lower the mids (i think it's 55-65 on my receiver so it matches the upper freqs say around 65-75. so if i have this right the db reading shouldnt start dropping off until 80hz or what ever my x-over is, right?

    your right about the chart compression...that looks terrible.i think i have some more tweaking to do
     
  12. SethH

    SethH Cinematographer

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    Try running it again with your crossover set at 100 before you adjust other settings. That could possibly flatten it out in the upper region.
     
  13. TimJC

    TimJC Stunt Coordinator

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    And if what Seth suggests works to flatten the FR, then it points to a phase issue when using the 80hz crossover. This is because the dip shown above ranges between about 75-90 hz, squarely in the 80hz crossover region.

    Using the variable phase control on your SVS, you should be able to address this and keep the 80hz crossover.


    Tim
    [​IMG]
     
  14. SteveCallas

    SteveCallas Second Unit

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    I feel kinda silly now - if you're crossover is at 80hz, no need to apply cuts below 75hz......your subwoofer level is just too high, way too high. Turn your bass adjustment to 0, turn your sub down a few levels, and take another measurement.
     
  15. Johnal

    Johnal Stunt Coordinator

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    bookmark!
     
  16. ShaunVanSkiver

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    well i think this is as good as i can get it without something more drastic. it seems that at 45 and 70hz im having a little dip and it didnt seem to chage not matter what setting i was playing with. here is the before in white and the best i could get it in red. i also posted this over at avs forum. thanks shaun
    [​IMG]
     

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