I am very happy with my new svs sub... but

Luis M · 04-20-2003, 12:26 PM

I bought the svs 20-39CS+ two weeks ago and I am very happy with it but I have noticed that as the volume goes up on my receiver the bass reduces itself(very noticable on music but also on movies), I can hear it but I can't feel it as I do when the volume is low. When I try the same material with my full range speakers as the volume goes up so does the bass and I can definately feel it as it moves everything around me including the couch. I have the 8200 Marantz receiver and all the speakers are set to small, the sub is powered by an Adcom 555-II.

What I am trying to say is that I expect the low and high frequencies to increase or decrease evenly as the master volume goes up or down.

Should I invert the polarity of the sub? The sub is located close to the left hand corner of my system behind the front left speaker. the sub has about six inches of breathing room around it and is about 2 inches away from the wall at the back.

Luis M · 04-20-2003, 12:31 PM

I should add that the system has been calibrated with a Radio shack level meter.

Bill Kane · 04-20-2003, 01:08 PM

...long shot here: in the receiver, have you assigned the SWFR to ON and not splitting it to the mains with something like MAINS/BOTH.

Rather than polarity, you want to check PHASE, and these tests are available on the Avia and Sound&Vision HT DVD disks. However, SVS says there's not much of a phase problem or disparity when sending all bass to the sub and only one sub is used.

I dont think your sub's position is "ruining" the response curve...

Luis M · 04-20-2003, 01:28 PM

Bill I have the sub to on and where it says SUBWOOFER OUT I can choose either THX or mixed and then there's the BASS PEAK TEST. That's all I can see as far as sub's tweaking.

Luis M · 04-20-2003, 01:34 PM

Maybe somebody with the 8200 marantz can give me some advise on the set up situation?

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Bill Kane · 04-20-2003, 01:53 PM

I can say if the BASS PEAK function is operating, it will limit the upper decibel output of the sub to preserve the driver. With SVS, peak limiter isnr needed.

Setting bass/LFE out of the receiver is found thru set-up in the remote. This is the SWFR Yes or ON to which I refer.

Luis M · 04-20-2003, 02:14 PM

The bass peak function can not be turned off it starts at -72 and it ends at god knows where. As I go up the bass is too strong and I am afraid I may bottom out the sub. maybe I don't know how this feature works, perhaps I have to put it at the lowest setting and I have been putting it where to me the base sounds the best without distoring and that is about -10, I am afraid to go any higher.

Jeremy Anderson · 04-20-2003, 04:37 PM

Quote:

Rather than polarity, you want to check PHASE, and these tests are available on the Avia and Sound&Vision HT DVD disks.

Actually, on a CS+ swapping the polarity is the same as reversing phase.

If you have Avia, do this: Run a bass sweep in any of the channels, paying close attention to the SPL meter as it reaches 80Hz. Then reverse the leads to the CS+ and run the same test again. If the SPL meter shows a higher reading at 80Hz with the leads reversed, leave it that way. If not, swap it back. Room acoustics can cause a reversal of phase, but if your sub is near one of your main speakers then that probably isn't the case.

If you find out that phase is a problem, then SVS' black box has a variable phase control that ought to let you fine tune.

Jeremy Anderson · 04-20-2003, 04:45 PM

Oh, and unless you have a major frequency null in your room or are running your sub very hot compared to the other speakers, it is very difficult to bottom that 20-39CS+. That Adcom puts a solid 325w to a 4 ohm speaker, so you've got enough power. Chances are you'll clip the amp before you get close to bottoming. I can push the Samson 1000 to clipping with Chapter 3 of SW:AOTC and never bottom my 20-39CS+

Edward J M · 04-20-2003, 08:07 PM

Quote:

The bass peak function can not be turned off it starts at -72 and it ends at god knows where. As I go up the bass is too strong and I am afraid I may bottom out the sub. maybe I don't know how this feature works, perhaps I have to put it at the lowest setting and I have been putting it where to me the base sounds the best without distorting and that is about -10, I am afraid to go any higher.

I suggest you research exactly how this control affects the bass. It may be a true electronic bass peak limiter, or it may be an LFE channel "trim" control.

Regardless, the owner's manual will tell you exactly how to set this control such that it has no effect on the bass.

After you do this, definitely recalibrate the sub. If you calibrated it with some sort of bass limiter activated, your initial calibration might be quite a bit off.

Once you are recalibrated and sending your SVS an unadulterated bass signal, try-out those passages again and see how they sound.

Regards,

Ed

SVS-Ron · 04-20-2003, 09:38 PM

Luis,

Another trick is to simply turn OFF the sub and set that "peak function" to its highest level. You are MUCH more likely to get a proper calibration if you ensure ALL processing modes are off (anything "THX" related especially!)including "mid-night mode" etc. AND this peak limiter is essentially off or out of the way at least.

Then calibrate using a test disk like Avia or Video Essentials and a SPL meter. This will keep things honest with DD processing anyway. Music is best done by ear in my experience, but make sure you can set different bass signal levels for "CD/Stereo" modes versus "DPL/DD/Surround" modes. Nearly all better receivers allow for this. Do NOT look for a magic setting that sounds good for both movies and music.

I've only been at this hard for 5 years or so and haven't managed it yet. ;^)

Let us know (here or via e-mail) if any of this helps. It certainly sounds like a processor issue and not a subwoofer issue but that doesn't diminish our interest in helping you solve it!

Ron

Luis M · 04-20-2003, 10:06 PM

Thank you guys, I'll get to work on the things you've just mentioned to see what works best.