Bottoming Out/Calibration of Sub (16-46PC+)

Discussion in 'Speakers' started by Richard Little, Jun 20, 2003.

  1. Richard Little

    Richard Little Stunt Coordinator

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    I am a bit confused with the process of calibrating my SVS 16-46PC+. I Emailed Tom who replied very quickly bringing up the main point of "How hot do I have it set?" I took my SPL meter and tried to find out. I found there to be a hole at around 80hz-90hz, no matter what my sub crossover or phase was set at. Using AVIA, all speakers set to small, sub set to 80hz or 90hz, the reciever has a crossover at 100hz. So when I try to get the responce curve flat at the crossover point/area I have to realy crank up the gain, but then at around 60/65hz, with the gain cranked up,the SPL meter realy starts to go up, WAY up. Is this normal? Will this cause my Sub to bottom out at low and heavy frequencies? When I turn the volume up (-30 to -27 under refrence) and play the globe explosion on AOTC, it makes a funny thunder/rip sound at the end of the explosion. Did I bottom it? Am I doing this right? Thanks from the new guy.
     
  2. Lee Bailey

    Lee Bailey Second Unit

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    Sounds like you bottomed it out. First off, don't try boosting a low frequency to bring it up. Set up the level using the Avia test tones, not the sweep tones. Make the sub equal to the fronts. On your sub, be sure to disable the built in crossover, let your receiver control it. If you are still getting a low output at 80-90Hz, try moving the sub more into the room, or, move closer to the sub and take readings. See if the SPL goes up or not. You could be experiencing a null. Though from your text above, it looks like you are using both the sub's crossover and the receiver's crossover. This will definitely cause problems in the frequency area you are testing.
     
  3. Zack_R

    Zack_R Stunt Coordinator

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    Richard, I would do as Lee suggested.

    Also, you can do a simply down and dirty phase adjustment by using the Subwoofer set-up option. With SPL meter (set to C-weighting and Slow) in hand at your seating position, play the first Left-front and subsequent Subwoofer level burst. Note the sub reading. Then dial the phase to 180 (if it was previously at 0) redo the test and note the subs response. The higher of the two readings on the sub is what you want.

    According to Guy of Avia, the sub pink noise sweeps between 35-70 hz. There are maybe 10 or more left front to sub level burst that have a varying combination of the sweep and could give you a different sub spl level. But in my experience, if you set your levels to match just the first tone then you're probably where you need to be.

    Note also that if you level match the sub to the read 85 on the spl meter and the left-front also reads 85 you are actually 1.5 to 2 dbs hot on the sub. This is due to the Radio Shack meter being less sensitive to the lower frequencies.

    The spaceship scene you are referring to is pretty intense and you may not be able to go any more than -5 db below reference without clipping the amp. If you set the subsonic filter to 16, I don't think you'll bottom this sub on that scene. You certainly won't bottom the sub -25 to -30 db below reference if it's calibrated properly.

    I have an Ultra calibrated pretty flat and at -4db below refence the red clip light on the Sampson is making itself known when I play this scene. I have a fairly large room so you may be able to actually get to reference without clipping the amp. Just calibrate and up the volume slowly until you learn the capabilities of your sub in your room.
     

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