My struggle to harness the power of SVS

Discussion in 'Archived Threads 2001-2004' started by Jeff_M, Oct 26, 2002.

  1. Jeff_M

    Jeff_M Stunt Coordinator

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    First of all, I would like to thank SVS for accomodating me throughout my SVS purchase process. My initial preorder for 2 25-31 PC+ subwoofers (way back in July) was changed to a pair of 20-39 PC+'s without a hitch. They even through in a sexy SVS wall plaque! I have had one HELL of a time trying to get these things setup. First of all, I live with 7 other people, so finding setup time when most people are out of the house is difficult. As you could imagine, these things get the house shaking! I am posting this information with the hopes that: (A)I could shed some light on common SVS setup problems (B) Figure out how to squeeze even more performance out of these beasts. The following is a short history of my struggle to properly setup the twins:

    1) As with anyone who gets a new SVS, my initial setup settings were, shall we say, a little bit hot. I had the subs in the front left corner of the room as recommended. While the bass was powerful, the subs were easily localized and appeared to be really straining. As I moved them away from the corner they weren't as easily to localize, distortion decreased, but unfortunately so did the "punch". I wondered how state of the art subs could be distorting with so little output. Perhaps the front wall, which is constructed primarily of wood was rattling, causing the distortion? This would make sense, as the further I pulled the subs away from this corner, the less distortion I would hear. Unfortunately, I couldn't get the output I wanted with the subs pulled away from the corner. So I put them back and did a little experiment. During a particularly bassy scene in Monster's Inc (The boo crying in the aparment scene), I stood right by the subs and pushed down on them. NO DISTORTION! Let me explain why this happenened. The concrete floor in the corner of the room is slightly uneven. The subs don't sit flush to the floor there, and end up jumping around ever so slightly. The distortion and localization was caused by the bass plate rattling against the floor. I could have sworn it was the driver itself, but boy was I happy to be wrong! The subs sat flush with the floor when pulled away from the corner, hence the lack of "distortion". My solution was to put a couple of layers of speaker polyfill under the bass plate so that it no longer rattles the floor in its corner. Problem solved.

    2)I believe that my second problem is much more serious. I noticed the subs bottoming out during Monsters Inc. (the scene where the sock is blown up... Great bass!). I would leave the settings on my preamp alone, and back off on the SVS plate amp volume until the bottoming stopped. Both subs are always kept at equal volume on the plate amp. Whenever I would find the setting with the highest output level without bottoming, the resulting SPL level would be somewhat unsatisfying. Just today, I decided to try something different. I would turn on only one subwoofer and keep turning it up until it started to bottom, then back off. I ended up being at about 2/3 volume on the plate amp. Once this was done with the first sub, I turned it off and repeated the same process with the other sub. The crazy thing is, on the second sub, the bottoming would occur at only 1/3 volume on the plate amp! I am almost positive that this sub is defective. On the positive side, I can't believe how high I can turn up the good sub without any distortion or bottoming. It makes me shiver to think how much output two perfect PC+'s could put out! I'll have to contact SVS today and see what they say. Does this sound like a bum unit to you guys?

    3)My last problem is also very perplexing. Upon discovery of what seems to be a defective sub, I put it back in its box and left the settings on the other sub alone. The only difference now is that the functioning sub is fed directly from my preamp (Up until now, I had an interconnect going from my preamp to the defective sub, and then an interconnect from the subs output going to the functioning sub). With the functioning sub fed directly by the preamp, it bottoms like crazy with the settings that had been fine before. Just to make sure I wasn't going crazy, I put the subs back to the way they were before, with the volume on the plate amp of the defective sub turned all the way down. Wow! Now it sounds good again. What the hell is going on here?

    I'm approaching the end of my SVS trial period, so I'd really appreciate any help that you subwoofer buffs could give me before they're mine to keep. By the way, my room is quite large (20X30 ft with 8 ft. ceilings, solid concrete walls and floor). I can't believe how much bass I'm getting from running only one of the two subs in a room this big (But I'd still like more or course.... ha ha!). Your help is appreciated!
     
  2. Ned

    Ned Supporting Actor

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    Is your house built on an Indian burial ground [​IMG]
    You should think about adding the ART eq or a Behringer FBD so that you can set a highpass filter below 18-20hz. Most of the bottoming is caused when strong
     
  3. Dustin B

    Dustin B Producer

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    You can't daisy chain them. You need to get a Y adapter. The out on the plate amp is high passed. It's for running your mains through the sub, not for daisy chaining. In other words it will be seriously attenuating everything under 100hz.

    This is likely why you could turn the, what you are calling the non-defective sub, up so high. It was receiving a severely attenuated signal. The level control is not an absolute volume control. It is a gain control. It is possible to get all 525W out of that amp with the level control backed all the way off if the input signal is strong enough. 1/3rd of the way on both would likely produce close the appropraite levels of bass (this could even be too high).

    Also what do you have the sub sonic filter set at? Should be at 20hz. And do you have all the ports open or have you plugged any of them? Do you have all other speaker set to small on your receiver, sub set to yes on the receiver and the crossover switch on the SVS subs set to disabled?


    I strongly recommend getting a Radio Shack SPL meter and a calibration disc. I like Avia. It's pretty much impossible to get the subs level correct with out an SPL meter. And although the receivers test tones will do, a good calibration disk is far superior.
     
  4. Doug BW

    Doug BW Stunt Coordinator

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    Jeff, did you calibrate using an SPL meter and either Avia or Video Essentials as recommended by SVS? Also, I took a quick look at the online copy of the manual for the PC-Plus, and I don't see where they recommend daisy-chaining the subs the way you did. (They say you should use a "Y" splitter.) I'm probably way off base, but by any chance did you skip over the "read the manual" step? [​IMG]
    Seriously, if you didn't calibrate with an SPL meter, you may be way over-driving the subs.
    I'd suggest that if you do everything described in the manual and still get undesirable results, or if there's something in the manual that doesn't seem to make sense, you should contact SVS.
     

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