Calibrating and Configuring a subwoofer

Discussion in 'Speakers & Subwoofers' started by EricDeB, Jan 16, 2006.

  1. EricDeB

    EricDeB Stunt Coordinator

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    Hey guys, I have almost all of my system calibrated except for my subwoofer. I have an SPL meter, and my first question is, how do I calibrate my subwoofer using an SPL meter? I have the rest of my speakers calibrated to 75 dB. Do I want my subwoofer also at that level?

    The other issue is how do I configure the crossover? I have 3 different knobs that have to do with crossover. There is a knob that says low-pass crossover and it goes from 40-120 Hz. Then there is a switch that says high-pass crossover. It can either be set to 80 Hz or 100 Hz. Finally, there is a switch that can be set to either "direct" or "internal X-over." There is also another switch labeled "phase" and it can be set to either 0º or 180º.

    Also, how do I configure the subwoofer's volume level. Do I want it turned up high on the receiver, and low on the actual subwoofer or the other way around?

    I know that subwoofer calibration is key, especially on my sub, since I have a Velodyne CT - 120 which is very sensitive and boomy.

    Thanks for all the help
    Eric
     
  2. SethH

    SethH Cinematographer

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    Your best bet is to do a search on this forum as there are some in-depth guides for doing this.

    Basically, you'll want to burn a CD with a frequency sweep and tones at different frequencies for your sub. This will give you an idea of how flat your response is. If it's too far off you may consider something like a BFD that will help you to level it off. Also, your calibration level for your sub will be different depending on the calibration disc you're using (Avia vs SVE).
     
  3. EricDeB

    EricDeB Stunt Coordinator

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    Thanks for the reply I will be getting one of those dvds shortly. If anybody could answer my other questions though that would be great!
     
  4. DarrenAlan

    DarrenAlan Stunt Coordinator

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    Also depends on your A/V receiver and what your main speakers are. Are they full-range running bass or little guys that don't put out much under 80-100 Hz? Do your speakers sound better running full-range or might they do better without bass information?

    Coupla things to think about:

    1) SPL meters, esp. Rat Shack's, is notoriously insensitive to bass. There's a chart somewhere on this forum that provides the db corrections.

    2) You want to avoid the dreaded "double crossover" problem. That is, if you're running your receiver's crossover, you want to set your sub's Xover at full or, in your case, disable it ("direct"). If using your sub's Xover, adjust it about where you know your main speakers' bass response falls off; probably just a tad higher (if the main's -3 db is, say, 50, you probably want to set the sub Xover @ 55 or 60 as those controls, too, are notoriously inaccurate.

    3) Phase, you just have to play by ear. Hadn't had much need for mine until my Orb Audio Super 8 arrived. Phase 0, bass was great; at 180, it practically disappeared. Sit in your favorite listening spot and have your wife/girlfriend/best friend/funny uncle flip the switch back and forth. If you hear a difference, go for the most robust bass; if not, don't worry about it.

    Hope all this helps!!!
     
  5. EricDeB

    EricDeB Stunt Coordinator

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    Hey thanks a ton. I think I'm getting it!
     
  6. Brian_cyberbri

    Brian_cyberbri Stunt Coordinator

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    Does your sub have a manual? I assume the direct/internal xo lets you bypass (disable) the sub's own crossover with "direct" mode. If you are using your receiver's bass management, that will be the way to go. Turn the high pass and crossover knobs all the way up, just in case, with the switch set to direct.

    Turn the subwoofer output level on the receiver to -4 or -5, and use some music with natural/acoustic bass to set the gain (should end up around 1/3 or a little higher. Music with natural/acoustic bass will help because you can tell if it sounds natural, boomy, bloated, etc.

    Placement is important, more than anything almost, so read up on audioholics.com and ecoustics.com about placement. Changing the placement of the sub will require you to go back through the volume settings, etc.

    You'll also need to check phase, because if this is off, it will create holes in your bass. This may be very noticeable on some songs, and not noticeable at all on others. Basically if the sub is out of phase with the speakers, the overlapping frequencies will cancel each other out, creating a hole in the sound at those frequencies. So if the song you are using doesn't have any bass in that range, you won't be able to tell.

    I highly suggest getting Avia as well, as it has a nice regimen of speaker and subwoofer calibration and verification tones. It also has plenty of test patterns to help you tweak your display, so that's an added bonus.

    Here are the setup articles at Audioholics, including this bit about bass management settings. Here are the articles on Ecoustics, many of which are links to articles on other sites. Check out the subwoofer section for tips on placement, calibration, etc.
     
  7. Sonnie Parker

    Sonnie Parker Second Unit

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    Check out the RoomEQ Wizard for your sub test tones, etc. It will do a sweep for ya and graph your sub response on top of giving you suggested corrections. Of course you'll need a parametric eq such as the BFD to do the corrections.

    As DarrenAlan stated... the RS Meter is notoriously inaccurate. Even with the correction values it's still inaccurate. Btw... those are available here if you want them. Over the last month or so I've found several people who have compared it with more accurate mics and it is off cosiderably. I compared it to my Behringer ECM8000 mic and there is quite a variation. My ECM8K is on it's way back from being professionally calibrated so I'll know more and will have a write up in the BFD GUIDE after doing more test between it and the RS Meter mic. Not only is the RS Meter mic inaccurate but they are different from one to the next... although you might find two very similar or almost identical, it is not always the pattern.
     

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