How do you configure the volume of the SUB? Used SPL for speakers.

Discussion in 'Archived Threads 2001-2004' started by elMalloc, Jan 22, 2002.

  1. elMalloc

    elMalloc Supporting Actor

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    I notice a little better balance now that I've configured my receiver with the SPL I got from radio shack.

    Now what do I do about the subwoofer volume level?

    How do I get this thing configured to the correct level?

    Or is it subjective?

    -ELmO
     
  2. Steve_Ma

    Steve_Ma Second Unit

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    Some people play with it for movies vs music after calibration. I do not (anymore). I set my sub's volume level before I calibrated (at about 1/3), then I calibrated with the SPL and ch levels in the rec. Now, I still have a mild boom with loud musical bass from my sub, but until I EQ it out...it's staying. The reason: Adjusting down and etc to try to reach my own personal "Bass Nivana" seems to involve more compromises in the material and I always end up less satisfied than when I had "alittle boom."

    My suggestion: Leave it alone for a few weeks or so. Get used to hearing the material as it is intended before adjusting for personal preference. Of course, if you don't like the way it sounds, that's different. Do what you need.

    Listening to a calibrated system and re-training my ears alittle really enhanced my listening pleasure.

    --Steve
     
  3. elMalloc

    elMalloc Supporting Actor

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    Thanks for the reply Steve, my question was how do I set the SUB level though? I was using my receiver to output the test tones and no subwoofer tone comes out. I have video essentials but I don't remember if that gives a test tone for the subwoofer.

    Do you somehow manually adjust the sub until you think it sounds good? Or can I use my new SPL meter to adjust it somehow?

    Thanks,

    ELmO
     
  4. Jude Faelnar

    Jude Faelnar Stunt Coordinator

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    I, too, am curious as to the answer to this question.

    JUDE
     
  5. John H

    John H Second Unit

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  6. Jason Wolters

    Jason Wolters Stunt Coordinator

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    Avia has a better sub matching test. It takes into account your receivers bass management setting. You can use the internal test tones or VE but these don't allow for certain variables that will alter what actually happens during a DVD playback.
     
  7. Steve_Ma

    Steve_Ma Second Unit

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  8. elMalloc

    elMalloc Supporting Actor

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    Thanks, couldn't figure out a way to get the stupid signal to keep on hold for me so I had to run the test 3 times. I got it to about 75db at the same level as my speakers. Now movies seem to be a lot bassier than I had them, I think I'll give it time or turn the bass down a bit.

    -ELmO
     
  9. ling_w

    ling_w Second Unit

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    I generally don't like the idea of calibrating based on pink noise since too many inaccurate, with factors that will lead to errors including:

    1. Ratshack's meter rolloff at low freq that is uncorrectable with wide band noise signal.

    2. Room peaks and/or nulls that skews the whole reading

    3. Rolloff of the sub which affects the whole reading.

    In 1, you could compensate for the ratshack's SPL meter's error if you are measuring spot freq, but if you are doing wide band noise, you would have to do some avg SPL decrease for the bandwidth you are measuring.

    In 2, room peaks of 10-15dB is not uncommon, especially with corner placement. A few of those peaks are enough to throw the reading off enough, even if the peak spans a very narrow range in freq.

    In 3, the reading has tom compensate for the lack of output below the sub's rolloff freq. If your sub has a rapid rolloff below 40hz, then you are in effect measuring the accoustic energy across 1 octave (40-80hz) as opposed to 2 (20-80hz) Your setting automatically becomes 3dB too high.

    Now combine the above 3 problems together, and you not knowing the f3 of the sub and how much to compensate the SPL meter based on the f3, not including the room peak's intensity, you end up with too many unknowns to get an accurate adjustment.

    The ideal way is to measure the f3 of the mains and f6 of the sub (assuming they are 12dB/24dB rolloff) (this is assumed to be at the crossover freq) and try to set the mains 3dB higher than the sub. You would probably have to measure seperately 1 oct above and below the crossover freq just to make sure your f3 and f6 did not reside on or near a room mode where it would affect the reading, and then measure the summed output to ensure a smooth transistion.
     
  10. BruceD

    BruceD Screenwriter

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    ling,

    Can't say I agree with your dissertaion on measurement methods as it relates to most HT rooms and equipment of forum members.

    My MLS & FFT measurement sessions don't necessarily support your stated errors being that much of a problem.
     
  11. ling_w

    ling_w Second Unit

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    BruceD,

    How can you say these problems does not affect one's measurement. Unless the peaks from room modes compenssates for SPL meter's decrease in sensitivity and the sub's early rolloff by the same dB. The error could be less than 1dB to something much higher than that, depending on room/sub/placement/crossover freq/SPL meter

    The pink noise method is specified in most HT application because of its general simplicity w/o getting overly complicated. You go tell a general HT guy to do a spot freq or 1/3 oct warble tone sweep, get anachoic f3 or f6 depending on crossover type/slope, match or offset by 3dB level between sub/main, measure the combined system with freq sweep, listen with freq sweep for integrtion, listen with variety of music. They will go mad.

    When spk mfg integrate their drivers in their product, they don't use pink noise and try to match the level, instead they do most of their work at the crossover point to ensure a smooth transistion between drivers.
     
  12. Bruce N

    Bruce N Second Unit

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    C'mon guys! ELmO is just trying to calibrate his subwoofer. This esoterica is not going to help him with a basic calibration, only confuse him more.

    ELmO said:
     
  13. BruceD

    BruceD Screenwriter

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    BruceN,

    That was my point. ling's details are more appropriate for the DIY section where people can debate what he is saying. I just wanted Elmo to know he didn't have to worry much about what ling was referring to.

    Thanks for your more clearly stated point.
     
  14. Bruce N

    Bruce N Second Unit

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    [​IMG]
     
  15. Jason Wolters

    Jason Wolters Stunt Coordinator

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    I agree as well. Calibrate all speakers to the same SPL. Match the sub and go have fun. BTW, I don't understand this "rolloff" business. The Radio Shack meter manual does not state that it has a "rolloff" on low frequencies. Set the meter to C as it says to. The only "rolloff" I can see is when the meter is left of A weighting.

    BTW, Avia doesn't use Pink noise. They use a test signal that is supposed to compensate for all of the things ling speaks about in his post.
     
  16. BruceD

    BruceD Screenwriter

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    Jason,
    Here is some info you should know about the RS SPL meter;
    RS SPL meter does not have a flat response curve in "C"
    This means the preamp inside the meter that feeds the needle and the RCA output port on the side has a specific reduction in sensitivity to lower frequencies (lower meter needle response than it should=rolloff) - specifically those below 200Hz even in "C" mode. It also has inaccuracies on frequencies above 10kHz, but we won't get into that.
    As stated, with pink noise for bass testing which is normally a composite signal of 20Hz-80Hz, these multiple frequencies cause the SPL meter reading to be 2-4dB lower than actual.
    But none of this really matters that much if you are just trying to calibrate the sub with all speakers (it maybe gives you a slightly hot sub which many like).
    For AVIA (I own VE), I think they still use shaped pink noise but just output it through the receiver's bass management system to both mains and sub, I will check.
     
  17. Jason Wolters

    Jason Wolters Stunt Coordinator

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    Thanks Bruce.

    I will take your word for it. As far as the pink noise thing...this is stated in an often posted thread from Guy Kuo. I can't find the actual thread right now, but I will look.
     
  18. BruceD

    BruceD Screenwriter

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    Jason,

    Here is what Guy said, "For this reason, test tones for setting channel level are usually not pink or white noise. Instead, a shaped noise whose spectral distribution is centered at a frequency which most speakers can reproduce is used. "

    What he doesn't actually say is that the "shaped noise" is most likely a "shaped" pink noise signal. This means it's not a standard pink noise signal.

    I think in most cases the "shaped noise" for subs is 20Hz-80Hz and the "shaped noise" for mains, center and surrounds is something like 500Hz-3kHz? (not sure about mains frequency range).

    The whole point is that it's not a single tone frequency, but multiple frequencies.
     
  19. ling_w

    ling_w Second Unit

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  20. Doug_B

    Doug_B Screenwriter

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    A couple of related questions, if I may.

    I'm in the mode of determining which location will be best for my sub. I don't have many realistic locations from which to choose, but I'm wondering if my strategy is sound. In my situation, I think the most important criterion is finding a location that provides the smoothest response across the relevant frequencies and avoiding any major dropouts. I think that sheer output volume is not as important.

    I have a CS Ultra, and my room is only 2100 cubic ft., fully enclosed. Even though I plan to have all 5 speakers set to small (let's say 80Hz xover) for HT (I currently only have mains and sub, waiting for other 3 channels), I don't think the CS Ultra will be driven too hard for the highest volume level at which I'm likely to listen. Thus, as long as the overall output level difference between locations is not great, then the freq response curve for each location appears to be the most critical factor. I do understand that it's not so easy to even assert which location is better for output volume when different freqs respond differently when comparing locations.

    Anyway, I've used a few AVIA tests with the SPL meter for a bunch of sub locations. I've used a couple of the pink noise tests, and I've used the low freq sweep to measure different frequencies (the latter is somewhat difficult due to the sweep rate). At this point, I did not calibrate the sub at each location relative to the main speakers for these tests, as I wanted to get "raw" levels, even though I do understand that the mains become more of a factor around the xover freq. I guess I can take measurements in both calibrated and uncalibrated modes to see if there are differences, as I'm down to two locations anyway (the other locations were all away from the corners and showed similar response curves but at lower volumes than the associated corner). I will defer to the "simpler" calibration method mentioned above of using the Avia composite pink noise test.

    I would like to get a test tone CD to measure the curves more accurately. I suspect I'll eventually get an EQ, as I already see bumpy curves.

    Any thoughts on my strategy?

    One other question. The sweet spot is away from both side walls and 25% into the room from the rear. I'm concerned about the response at other seats in my room, which are against the long wall (I have an L-shaped modular sofa). Generally, the response curves are a number of dBs higher at these locations. Fortunately, most movie viewing will be just me and my wife, but this could be a problem with a larger crowd. The only things I can think of doing with alot of folks in the room are 1) turn down the sub output, 2) sit on the floor instead of side of sofa, or 3) move sofa (temporarily) to improve bass response for those bad seats; the sofa is modular so detaches into 3 pieces. Thoughts here?

    Thanks.

    Doug
     

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