Question re SVS subwoofer output measurementss

Discussion in 'Archived Threads 2001-2004' started by PhilS, Dec 22, 2001.

  1. PhilS

    PhilS Stunt Coordinator

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    I just received my SVS 16-46PC, which I added to my M&K 7.1 system, including an M&K 125 MKII sub. First, let me say what everyone who has an SVS sub already knows - it is awesome. I am astounded at what a difference it makes in my setup. The addition of the 16-46 to my system is like the difference between having no sub at all and then adding one. I have only played a few demo disks so far, but the tank scene on SPR and the pod race on TPM blew me away. Is it silly to be a little bit afraid of a subwoofer? Also, once I calibrated the levels and played some music, I was also amazed at how much better music sounded on my system. There was much more bass, but without any boominess. I feel like I have to listen to my entire CD collection again, and watch all my DVD's over again. Way to go SVS! (I'm not going to mention anything about SVS customer service, as anyone who has dealt with them knows they are great to deal with and any compliment hardly does them justice.)

    Now to the questions. First, the output of the 16-46 is such that, to calibrate my system, I had to turn down the subwoofer output level on my TAG pre-pro to -9.5 db. Does this seem unusually low, and is there any problem with lowering the subwoofer output on my pre-pro tha much? The SVS manual seems to say that this is the best way to control the overall subwoofer volume, as opposed to turning down the volume control on the SVS sub itself. (The volume control on the SVS is at about 6.5 on the 10-line volume control. The volume control on the M&K sub is +3 db, which was needed to balance the system.)

    Second, I used a test CD and a Radio Shack SPL meter to take readings at various levels. I adjusted various things until I came up with the following readings, after adjusting the RS meter. (I have set my Tag to crossover at 80 Hz.) I'm wondering whether these readings are such that I should not really need to tweak much more, or whether someone thinks that I need an equalizer or one of those Beringer units. Here's the measurements. Are these good, bad, so-so?

    20 Hz = 70.2

    22 Hz = 75

    25 Hz = 79

    28 Hz = 82.5

    32 Hz = 78

    36 Hz = 85

    40 Hz = 82.5

    45 Hz = 84.2

    50 Hz = 85.5

    56 Hz = 80

    63 Hz = 84.8

    71 Hz = 81.6

    80 Hz - 73.5

    Thanks in advance for any help.
     
  2. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    That FR would be OK for HT, but for music its real lumpy. In 2 octaves, you've got a 15 dB swing with 4 peaks: 28.35.52 and 63 Hz. Go listen to some strong bassy music. Did you notice that some bass notes kind of jump out of the soundstage and others kind of recede back into the music ? I thought so. Thats the bass track running through your 4 hot spots. A BFD would easily flatten that out and also solve your other problem. To get the SPL back that the BFD trims off your peaks, you would need to trim the receiver up 5 or 6 db. Another way of looking at this is that the equalization required to flatten the response of these interacting subs will eliminate the headroom advantage that the 2 subs give you.

    I bet you have the subs separated in position. This will add sub-sub cancillation to your room modes. If there is any way to get the subs side by side, the FR will improve. But there will still be 1 or 2 peaks left because of the room. Some other tweaking that may help a little is to play a tone in one of the troughs like 32 hz and make changes in the sub's phase. There is a chance that you could boost a trough a little more than the adjacent peaks. Another thing that might help is the deep boost on the PC amp may do a little to help the rolloff below 36 Hz. The only way to be truely rid of those is an equalizer like the BFD or room treatments (plus side by side placement).
     
  3. SVS-Ron

    SVS-Ron Screenwriter

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    Phil,
    Thanks for the thumbs up! I've lost count of the number of folks that thought they had "the bomb" of subwoofers, but upon adding a big SVS realized they had a totally new defintion of what bass is supposed to sound like.
    Not sure from your note if you got onto the fact that the RS SPL meter is a bit insensitive down low? You need to add the following to your measurements if you didn't already (you mentioned "adjusted" so maybe that's what you meant you did?).
    Anyway, to have the most accurate readout of how flat (or not) your subs are running look to this chart .
    I don't think running your processor bass setting that low is an issue at all. You DO have lots of sub power now after all. If you haven't already though, you might find that running your subs (the SVS anyway) a bit higher than the mains sounds very good. Especially if you listen to more moderate levels, a 2-5dB "bump" on your subs can sound fantastic.
    Just leave SOME downward adjustment (I like to leave 6dB at least) is desired. This way you can tweak the subs up OR down on the fly, from your chair.
    Ron
     
  4. PhilS

    PhilS Stunt Coordinator

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    Just to post a follow-up, I tried turning off my M&K sub and just checking the FR with the SVS. I found that I had a few peaks and valleys similar to what I had with both subs running, and a real nasty peak at 50 Hz with the SVS by itself, and I had trouble eliminating it. In fact, although the SVS and M&K sub are located in two different locations (a necessity given certain room constraints), if appears that the addition of the M&K evens out the frequency response. I also lowered the subwoofer output on my pre-pro about 2db, as the output was a little high before, and that helped the FR also. It's not perfect, but I think it sounds great for movies, and it also seems to sound fine on music. (I'm not as picky as your true audiophiles. This tends to happen as you get older and you don't hear so good no more.)
     
  5. Wayne A. Pflughaupt

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    Get a parametric EQ, Phil. You will be amazed at the improvement once that 50Hz peak is eliminated. You will notice that the lowest notes come out much better. The fact is, every sub need equalization for optimal performance.

    Happy Holidays,

    Wayne A. Pflughaupt
     

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