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How I calibrated my new SVS sub...

Discussion in 'Archived Threads 2001-2004' started by Steve Zimmerman, Jan 10, 2002.

  1. Steve Zimmerman

    Steve Zimmerman Second Unit

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    I just received my new subwoofer. It happens to be an SVS CS-Ultra with S1000 amplifier, but that's not really essential to this discussion. Here's how I calibrated it... I invite feedback from those in the know.

    (1) I placed the sub in the only place my wife will allow: in the corner of our family room behind a chair. The room is rectangular, roughly 20x15x18 (yep, 18-foot ceilings) with an open adjoining kitchen--i.e. no doorway--that measures about 20x15x8. So there's a lot of air to move.

    (2) I set my main speakers to small; my Denon 2801 receiver crossover is hard-coded at 80 Hz; using the internal test tones, I calibrated my other speakers at 75 dB and the sub channel (for now) at 80 dB by setting the internal subwoofer level to -6dB and then backing the S1000 amp down from the max output position until I got to 79 dB. The S1000 was at about 90% max when I got the desired reading.

    (3) Using my CD player in 2-channel stereo mode (with frequencies below 80 Hz being routed to the sub since my mains are set to small), I measured a 507 Hz Warble tone from the Stryke CD as the reference point and increased the volume until my SPL meter read 80 dB. I then measured every Warble tone from 15Hz to 12.9kHz and added the requisite SPL adjustments to the lower frequencies. What I found was that even with the SPL corrections and the fact that I had set the sub 5dB hot on my receiver, the frequencies below 80 Hz were uniformly about 4 dB below the other readings! What could be wrong? I measured and remeasured but still got readings in the 75-76 dB range. All other readings on the scale were within 2-3 dB of my 80 dB reference point.

    (4) I whipped out the AVIA DVD and measured the channel volumes by increasing the volume on my receiver until the left front channel read 80 dB (full 85 dB is too loud for me). As I cycled through the channels, they were all at 80 dB. But when I got to the subwoofer measurements--suprise, suprise--the subwoofer only read 75 dB! Hmmm. I noticed that the frequency for AVIA test tone was much lower than the frequency used by the receiver, but even adding a dB or two would not account for the whopping 10 dB difference.

    (5) Based on past searches and the fact that I had two "real-signal" tests that conflicted with the receiver test tones, I concluded that perhaps the receiver test tone for the subwoofer is bogus--something on the order of 10dB too low. I would assume the AVIA tones were correct and forget about the receiver tones.

    (6) Using AVIA and the volume knob on my amp, I increased the subwoofer to about 1 dB beneath the other channels to account for my assumption that the RS SPL meter reads about 2-3 dB low at the AVIA frequency (anyone know what that frequency is?). I tested a few clips of music to test and the bass sounded *really* good--much more prominent than I was used to, having always used the receiver test tones to calibrate my previous budget sub.

    (7) I played my old standby music CD for testing bass (Flim and the BBs "Tricycle") and it reminded me of a friend I had in college who played the drums. Sometimes I used to go over to his house when he played. I remember feeling the air move--not just hearing sound--when he smacked the foot pedal. That's the same impression I got when listening to the new sub.

    (8) Nobody was home, so I whipped out the Toy Story 2 DVD and played it at 5dB below reference. I would never ever in a million years turn it up that loud for regular viewing, so I figured that if the sub could play at 5dB under reference then I would have plenty of headroom. Well, during the TS2 intro scene, the sound level reached a corrected 110dB at one point and the house felt like it was shaking. No joke: a picture on a shelf on the other side of the room from the subwoofer was blown off the shelf and (luckily) landed onto a couch beneath it. The only damage was that my jaw hurt a bit from dropping into my lap. After anchoring the photo, I played this scene a couple of times, watching to see if the amp was OK. I did notice that the "Clip" light on the amp flickered yellow at one point but there was no buttoming out of the sub.

    (9) Just to make sure I wouldn't cause any harm, I decided to back the subwoofer level down to 2 dB beneath the other channels--which means that after correcting for SPL meter error it's just about flat. Not too hot, not too cold. At more modest listening volumes (we *rarely* exceed 10 dB below reference around here), I might bump it up just a bit on occasion.

    Fun stuff indeed. Any thoughts on the 10 dB discrepancy between the receiver test tones and the AVIA DVD?

    --Steve
     
  2. Bhagi Katbamna

    Bhagi Katbamna Supporting Actor

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    I have an Onkyo 989 and had a similar experience with the internal tone and Video Essentials so it isn't just Denon that has this problem.
     
  3. Steve Zimmerman

    Steve Zimmerman Second Unit

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    Can anyone else with a Denon confirm or refute what I'm seeing, specifically: that the internal test tones appear to set the subwoofer channel about 10 dB less than the AVIA DVD?

    --Steve
     
  4. Clinton McClure

    Clinton McClure Casual Enthusiast
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    I am running a Yamaha RX-V995 and the internal test tones are at a different volume than when I play the test tones on my VE DVD. I always use the VE tones because that's the source unit where the audio originates, so I figure why use the receiver's tones? (Am I making any sense here?)
     
  5. Nick P

    Nick P Second Unit

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    Steve, my 3802 does the same thing. Also interesting, the Avia test tones for the sub play lower than my Video Essentials DVD tones. I can't remember exactly how much but I think it was at least 5db.
     

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