SVSub help needed

Discussion in 'Archived Threads 2001-2004' started by Jon_Liu, Sep 11, 2002.

  1. Jon_Liu

    Jon_Liu Stunt Coordinator

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    Well, the problem here might not even be a problem at all, but it's a concern that I would like cleared. As I've been fiddling with my sub's placement I finally found the best result directly in back of the main listening seat. It sits roughly 4 feet back from that seat. Every other place that I put it, either didn't put enough ouput out, or was too directional and easy to locate. But anyway, on to what I noticed. First off all let you know of my listening tendencies. I run my system roughly 10 db lower than reference level with my sub running about 3-4db hot.

    When I was going through the T-Rex scene and the first brachiasaur (sp?) encounter, I noticed at the what I would find the lowest frequencies or the loudest portion of the bass in that section, that I was getting some odd sounds come from the sub. Maybe because it's so close that I am noticing these sounds, but I am pretty sure that the sub is not bottoming out. Everyone says that you will "know" when a sub bottoms out with a big 'CLACK' or something of that sort, but that's not what I am getting (at least I don't think that's what I am getting). To 'attempt' to describe what I hear, I think it may sound like 'distorted' low frequencies, but I am not sure... It's not very noticable. My thought is that it is the sub and it's not broken in yet. I am hoping that is the case. And if that's the case, how long would it take 'roughly' to break in the sub? I watch at least 1 movie a day. How many hours/days/weeks does it usually take? Thanks for any info you can give me.

    Regards,
    Jon
     
  2. Chriss M

    Chriss M Second Unit

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    which model do you have? You may just be pushing the limits of the driver. 3-4 db's hot is actually closer to 6-8 db's hot, due to the innaccuracy of the radio shack meter at low frequencies. Running at -10db would actually be running the sub almost at full reference volume, which may be asking quite a bit of a single sub especially if your room is large.
     
  3. SVS-Ron

    SVS-Ron Screenwriter

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    Jon,

    Feel free to e-mail us on any such questions you have 24/7. I would say 75% of the time any odd sounds are actually something near the sub rattling/resonating. Wood floors are notorious for this, but it literally could be anything. Often you would SWEAR it's the sub but sound has a way to fooling you.

    Having said that it could be your room, the very demanding material, and your relatively hot calibration (as pointed out you are probably very close to reference levels) are finding the limits of the sub. The PCi's are incredible performers but they DO have limits. Port "compression" (where air can't flow out/in quick enough) could be what you are hearing. It typically will happen before a driver goes into over excursion.

    I can't recall what you used to calibrate your levels? A sound meter, and what for the calibration "tones"? Video Essentials is what I recommend, or Avia.

    I'd guess you are getting very high levels of bass when you start to hear this? Give us a bit more info (and refresh our memory) here or even better via e-mail (the latter is just more responsive for us).

    Keep us posted, we want to be certain your sub is working 100% right.

    Ron
     
  4. Jon_Liu

    Jon_Liu Stunt Coordinator

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    Well that's interesting to know, I didn't realize that the 3-4db meant I was actually running closer to 6-8db hot. That's good to know. The model I have is the 20-39PCi. I didn't think I could hit the limit of the sub that easily! Oh well, I ought to turn it down just a smidgen for the DTS movies anyway I suppose.

    After listening to it more, the sound seems to be coming from the actual driver area. Not necessarily from the driver itself. After reading you guys' postings it comes more apparent that it seems more like the driver pushing the air towards the bottom plate and the air is causing distortions. But after that, I'm gonna turn down the sub just a hair probably 1-2 db see if it still does it. Either that or I'll just try listening at a lower volume, since I seem to be close to reference levels! I'll post again with my findings after tinkering a bit. Keep the ideas and help comin though! I am definitely up for hearing more suggestions! Thanks!

    Also I am using the Radioshack meter with the avia disk to calibrate my system. will recheck my current settings again now
     
  5. Manny_S

    Manny_S Stunt Coordinator

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    Jon_Liu, I'm pretty sure you're hearing the same thing I heard when I first started playing my 25-31PCi at reference levels. I think what you and I are hearing is the air actually being compressed rapidly between the woofer cone and the bottom floor plate and being push out horizontally. I only heard this when I was very close to the sub. But, when I'm at my center listening position, the sub is 12ft away from me and I don't hear this "thing" we're hearing at all.
     
  6. Jon_Liu

    Jon_Liu Stunt Coordinator

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    You're right Manny, when I move further away from the sub, I don't hear this. Sadly, like I mentioned before, the placement for my sub is limited to this position. I've tried all 3 corners that I could possibly put the sub, but to no avail, directly behind the main seating area, 4-5 feet behind, is the only place where it sounds dispersed completely. Other than when I heard the "sound" coming from the sub, I couldn't tell where the sub was. Moreover, with the new sub placement I found that a big peak at about 35-30hz has been toned down dramatically, still there, but a lot better than it was with a corner placement.

    After listening to other materials where bass is very loud, I don't notice it being a problem. It is just mainly Jurassic Park. I think the reason why I can hear it when testing it with the T-Rex scene (Ch 11) at the beginning of the chapter before you make contact with the T-Rex, is because the other speakers are not really being used a whole lot to cover up the sound. Near the beginning of the chapter before you make contact with the T-Rex.

    If I AM having problems with other disks making the same noise, then I can't tell because the other speakers are covering it up very well.
     
  7. Manny_S

    Manny_S Stunt Coordinator

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    My first experience with this sound we're hearing was while watching JPIII's airplane crash scene followed by the dino fight. I don't think you have anything to worry about.
     
  8. DarrinH

    DarrinH Second Unit

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    I am a new owner of a 20-39Pci and have noticed localization with my placement as well. I thought that a good sub (like SVS) would not be localized that easily. Does this have a lot to do with the room itself?
    My room is approx. 12'X17'X7' and the walls and floor are carpeted.
    I am driving it with a Denon 2802.
     
  9. Jon_Liu

    Jon_Liu Stunt Coordinator

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    Well Darrin, For the most part it IS great at non-localization. With my previous positioning of the sub, in the corner I felt it was too localized and it's probably justified because all my HT equipment was blocking it from going anywhere else but straight out, towards the listening area. There was a 1-2 foot gap between my equipment and the sub, so the equipment, tv and such were probably reflecting any sound that it was trying to push out. Of course, when I moved it around to different corners, the corners nearest to the seating area were probably too close thus still making it localized. And like I said in an earlier post, once I put the sub directly behind the seating area, I really couldn't tell that the sub was back there. So room acoustics, including furniture and whatnot really plays the biggest role. (anyone who knows that I am wrong on some point here, please feel free to correct me!)

    Regards,
    Jon
     
  10. Lee Bailey

    Lee Bailey Second Unit

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    Jon, what crossover frequency are you using to your sub? Also, are the rest of the speakers set to small? The higher the crossover frequency, the more directional the sub will get. Generally, 100hz and below are not directional.
     
  11. Jon_Liu

    Jon_Liu Stunt Coordinator

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    Lee,

    I am using the crossover on my receiver at 100hz. Unfortunately it doesn't go lower than that. Been trying to fiddle with it between the sub's crossover and the receiver's crossover to see which one works better or what combinations would work better.
     
  12. Lee Bailey

    Lee Bailey Second Unit

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    Jon, you should be using only one of the crossovers. Using both can cause some unwanted effects on your sound. If you don't have seperate pre-amp outputs on your receiver, and are using the sub-out jack, you should disable the sub's crossover. I take it you have set the rest of your speakers in the system to SMALL? An option is to also use the speaker level inputs to your sub, but this would require you to move it back to the front of the room(unless you want some long cable runs). You could then set your receiver to NO SUB, your front speakers to LARGE, and use the variable crossover to get the sound you want.

    From the first post, it would sound like your seating position is in a null point for low frequencies in your room. Had you tried moving your seat forward or backwards?

    Just some suggestions.
     

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