Calibrate Subwoofer with Other Speakers

Discussion in 'Speakers & Subwoofers' started by Joel McIntosh, Sep 25, 2003.

  1. Joel McIntosh

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    I'm having a bit of trouble calibrating my HSU VTF-2 subwoofer with the rest of my system (receiver-Marantz 7300; fronts Polk RTi150; center Polk CSi40; surrounds RTi38; and back CSi30). I've set all speakers to "Small" in the Marantz receiver's set-up menu and set the crossover to 80 Hz. Using a digital spl meter, I've used the Marantz calibration menu to adjust all of the speakers and the subwoofer so they are outputting 75dB when the receiver's volume is set at 0. I've also used the Avia DVD to double check to see that the subwoofer and the front speakers output levels match. Ok, now here is my trouble. First, and this just seems odd, to get the sub to match the other speakers at 75db, I have to turn the volume knob on the VTF-2 to something like 10%-15% of its potential. This doesn't seem right to me, the VTF-2 only has a 10" speaker, and I'm in a 14'x14' room with lots of openings into other rooms. Does this situation sound right? Second, to my ear, the bass isn't strong enough. However, the spl meter is saying the subwoofer is cranking out bass at the same level as the other speakers. Am I doing something wrong?
     
  2. John Garcia

    John Garcia Executive Producer

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    Sounds very similar to what I have going on with my 8300 and my VTF2. Nothing wrong with this. I find that I run the sub a few dBs hot, set to maximum extension. There is another thread discussing almost the same issue. Turn the sub's gain up a bit, say 1/4, and calibrate using the receiver's trim.

    Also, if you find yourself knocking down the main speaker's levels a lot, don't calibrate at "0". That seems quite high.
     
  3. Edward J M

    Edward J M Cinematographer

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    The Avia DVD is a true Dolby Digital disc. As such, the subwoofer test tone is not discrete like the internal one from an AVR.

    With an 80 Hz xo, the surround channel in question will contribute more than you think to the subwoofer test tone. This is even more exacerbated if you are using bass capable L/R mains and are using the L or R from main channel for comparison/calibrating the subwoofer level. If you don't believe me, run the tone and power off the VTF-2 and take a SPL measurement. I'll bet you're seeing at least 70 dB from the RTi150 in question (if you are using 75 dB as your overall calibration level).

    This phenomenon can lead to a "weak" sub calibration as compared to the discrete method using internal AVR test tones. As such, calibrating the sub 7-8 dB hot using Avia usually yields about the same overall sub level as calibrating 3-4 dB hot using the internal AVR test tones. Give it a try and see what happens.

    Also remember the VTF-2 only has a single 10" driver and a 150 watt amp. It isn't going to move mountains in that size room, especially if the room is open to other spaces. Try running the sub in Maximum Output Mode with both ports open.

    You may also want to consider running the 150's on large and the other speaks set to small. The 150's are power hungry but are quite bass capable so if you bought the bass you might as well use it. If they suck the life out of the Marantz, consider a separate external amp for them.

    If you still can't get decent bass, experiment with placement; maybe there is a null where you are sitting and perhaps the sub isn't optimally placed.

    Regards,

    Ed
     
  4. John Garcia

    John Garcia Executive Producer

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    My room is quite a bit larger than that, and the VTF2 has no problem exciting the whole room at less than ~25% gain.
     
  5. Mike Nep

    Mike Nep Stunt Coordinator

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    I have a 71hz standing wave in my room that is immune to any changes I make on my BFD. It's really bothersome. Any suggestions to get rid of it?
     
  6. AndyDC

    AndyDC Agent

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    J.M.,

    Sorry about the basic question but could you explain this a bit more? You say "The Avia DVD is a true Dolby Digital disc. As such, the subwoofer test tone is not discrete like the internal one from an AVR."

    Do you mean that in the Avia test tones, the "subwoofer" test tone is not the same as the LFE channel? Or that the LFE channel signal also goes out to the mains, subject to the low-pass crossover at 80Hz? I thought dobly digital was in fact discrete?

    Let me ask the questions a bit differently.

    If I use a set of test tones from a CD I've burned myself, this is a normal stereo CD. In this case, I suppose the base goes to all the speakers subject to the settings and cross-over of the receiver. In this case, I thought it made some sense to calibrate the subwoofer with the mains plugged in. If the cross-over is working well (and depending I suppose on the natural rolloff of your mains, surround and center) you should get a flat response through the crossover frequency (assuming no room modes etc.)

    Now, this would be the proper setting for stereo music layed through the same receiver setting you used to calibrate the sub (be it stereo mode, dolby surround for music, etc.)

    What happens then if you play a Dolby Digital 5.1 DVD? Or suppose you switch from stereo to dolby surround. Would the subwoofer still be calibrated correctly?

    Thanks,

    Andy
     
  7. Mike Nep

    Mike Nep Stunt Coordinator

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    I have a 71hz standing wave in my room that is immune to any changes I make on my BFD. It's really bothersome. Any suggestions to get rid of it?
     
  8. Edward J M

    Edward J M Cinematographer

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    Hi Andy:

    When the subwoofer test tone is run in the Avia disc, it consists of a rumble tone with a bunch of frequencies grouped from about 40-80 Hz.

    Avia is a DD disc, and the subwoofer calibration section uses any of the 5 surround channels. It generates some pink noise for the surround channel, and then generates a deeper rumble tone for the surround channel. Since the two tones are always processed through the same surround channel, the bass management circuit automatically starts to redirect the rumble tone to the subwoofer. But the BM circuit typically consists of a 12 dB/octave high pass filter and a 24 dB/octave low pass filter, so the surround speaker in question will still "see" and play part of the rumble tone if the xo is set at 80 Hz (which is common for HT applications).

    The only Avia test that is discrete for the subwoofer is the LFE reverse sweep (but this cannot be used for calibration per se, it is more for evaluating room acoustics). That LFE reverse sweep does use the ".1" LFE channel, which is the exclusive domain of the subwoofer if the other speakers are set to small and the sub is set to on/yes.

    In comparison, the test tones generated by the typical AVR are discrete and the subwoofer test tone is not passed through the surround channel and the BM circuit. It is passed directly through the subwoofer output jack. The surround speakers do not contribute any volume to the AVR subwoofer test tone at all. That is not the case with Avia and this can result in a significant difference in subwoofer calibration level between the two methods.

    I have never used a set of test tones to calibrate the subwoofer level per se. I use them to perform a frequency sweep on the system and yes, it is appropriate to leave the mains on to evaluate the transition between them and the subwoofer at the xo frequency.

    Regards,

    Ed
     
  9. Steve_Ma

    Steve_Ma Second Unit

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    I have the Marantz SR7000. I also calibrated my speakers with the volume knob set to 0. Using an SPL meter and a 100hz x-over, my sub's volume is also only at about 20% of it's max setting. I think the sub's ch level is at something like -6 or -7 or something.

    Bottom line: Who cares? Neither my AVR or my sub are getting stressed and the sub blends nicely with the mains. I wouldn't worry about it unless you start to experience some performance issues.

    --Steve
     
  10. Joel McIntosh

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    Thanks for all of the help. Based on a few suggestions (both here and at the HSU forum), (1) I shifted my receiver to subwoofer output to -7 dB and (2) recalibrated the system so that the subwoofer runs about +2 to +3 dB louder than the other speakers. The former let me turn up the volume on the subwoofer to a solid 15% of its max (up from around 10%), and the latter resolved my sense that the bass was not powerful enough when my system was playing at low to moderate levels of volume (90% of the time it is playing in this range for me -- someone at the HSU forum suggested that at these lower volume levels it is harder to experience the bass). So, things are sounding better now. However, it still strikes me as weird that I've got the subwoofer's volume at only about 15% with the receiver to subwoofer output at -7 dB in a 14' x 14' room. When in the world would someone have the occasion to jack the subwoofer up to 100%? At that level, plaster would start falling from my ceiling!
     
  11. GregBe

    GregBe Second Unit

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    Ed,

    If you don't use the test disc to callibrate your sub, do you use the avr tones or do it by ear?
    Also, what do you use the frequency sweeps for?

    Thanks
    Greg
     
  12. Edward J M

    Edward J M Cinematographer

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    Hi Greg:

    I actually have used Avia to calibrate my sub, as well as the AVR discrete sub tone (and more recently the new Digital Video Essentials).

    I was merely pointing out the differences between the two methods and how using Avia might have explained Joel's weak sub calibration.

    I use the 1/12 octave test tones for manually plotting in-room frequency response of the sub from 10-100 Hz.

    Ed
     
  13. Zack_R

    Zack_R Stunt Coordinator

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  14. GregBe

    GregBe Second Unit

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    Thanks Ed,

    I am thinking of upgrading my VE to DVE. Have you found the sub calibration to be accurate (some people in the software forum have said it is off)? Also, are the frequency sweeps on DVE good enough for manually plotting in-room frequency response?

    Thanks
    Greg
     
  15. Edward J M

    Edward J M Cinematographer

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    I'll compare the sub calibration tone for Avia to the one for DVE at the same Master Volume and tell you if they are anything but exactly 10 dB apart.

    I think Avia is mastered at -20 and requires 85 dB, and DVE is mastered at -30 and requires 75 dB. If there is more (or less) than a 10 dB difference between them at the same Master Volume, I'll note the results and post them.

    The 15-300 Hz DVE sweeps I have run thus far are way too fast for plotting the FR. Even the Avia reverse sweep is much slower than the DVE. You need a spectrum software package and a mic, or you can do it manually (like I do).
     
  16. Joe Szott

    Joe Szott Screenwriter

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    Joel,

    You never know with subwoofer setups, room acoustics and the hardware itself can give great variations to the proper setting. Ultimately, what sounds good to you is what is important.

    Through Avia I calibrated the sub and mains at -20 and came out with a sub level of 0. Much less than what I had it set previously on a different receiver. After listening for a week or so I realized that was actually the right setting for bass balance to main speakers, but we set the sub to +1 anyway. My wife and I love bass even if it considered slightly overweighted by the SPL meter. So when it sounds right to you, consider it calibrated [​IMG]
     
  17. Edward J M

    Edward J M Cinematographer

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    Well, the DVE subwoofer calibration tone is obscenely hot. I calibrated all 6 channels (7.1 two rear surrounds) to 75 dB use the high band (>500Hz) pink noise.

    Then the subwoofer tone hit and I had to jump two scales on the SPL meter! It checked in around 92 dB - a full 17 dB hotter than the surround channels.

    Something is amiss here. Avia is not nearly that hot, and my AVR discrete test tones show the sub running about 3-4 dB hot.

    Ed
     

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