SVS Pb2+ Calibration and SPL Meter bouncing around

malikarshad

When I calibrate my system with AVIA and RS Analog meter for subwoofer the meter fluctuates a lot about anywhere for 2 to 10 dbs.
I have Denon 3803 and I set the master volume to 0 db and the meter to 80 db slow (C weighted). When I calibrate the F, R, C, SR, SL the meter needle correctly stabilizes at 85db. But for my sub SVS Pb2+ it fluctuates anywhere from 87db to 97db. Its like for a second it stays at 87 then goes beyond 95db and keep doing back and forth. I have tried adjusting the gain control on the sub but I does not help much. For some channels it fluctuates a few db more than the others.
Is this the problem of room gain?
I live on the first floor in an apartment building and the floor is carpeted. There is nobody living below me.
How do I calibrate my SVS sub correctly?
Thanks in advance for your help.

ninerbj

I have the same problem...my readings bounce all over the place!
I hope someone chimes in on this one.

sowen010599

Pink noise, subwoofers, and room modes.

Your "in-room" sub response is going to be lumpy unless you tune it out with a parametric eq. At certain frequencies, the shape of your room, your walls, etc. add to, or take away from, the output of the sub. That's normal. What's happening is the random "full bandwidth" tones move across these frequencies, they are louder, or quieter, because of this room interaction. You see this on the SPL meter.

malikarshad

So how should I calibrate it. For e.g. the AVIA disc has a sub calibration for each speakers that alernates the pink noise btn the speaker and sub to check if the level matches both. In my case the speakers correctly shows 85 db and when the sub plays it keeps on dancing anywhere for 87db to 96db+. and for each speaker the level of fluctuation is different.
At what the point in the meter i should calibrate the sub?
What level in the meter indicates the the sub is calibrated to 85db?

faster100

Just switch your meter to slow, instead of C weighted fast.. and it will stop bouncing,

malikarshad

Originally posted by faster100
Just switch your meter to slow, instead of C weighted fast.. and it will stop bouncing,

I always set the meter to slow for calibration. any other suggestions

sowen010599

Average the high and low readings.

malikarshad

Do you guys think placing a granite/marble stone under the sub plate would help.
I'll try the average level to set the sub.

sowen010599

If you have the sub on a wooden floor, like a peer-and-beam home, or a second story floor, then sure. But if it's on a concrete and carpet floor, then no.

dave shepard

Do you have your reciever sub setting at -5 and the xo setting at 80. if the sub setting is too high then you could be getting distortion comming through. Do you have it hooked up through the speaker wire or sub out? Try to reposition the sub even the slightest move can make a differance.

Dave

EricH

I saw the same thing when I got my Avia disc last week. All other pink noise tests are fine, but the pink noise SUB test sounds kind of like random low frequency warbling. And yes, that needle is still moving around quite a bit C-weighted slow. However, you can find a middle point in the needle fluctuations. That's what I do.

More importantly, I use the test only as a reference. I think it's better to set your sub output level to your preference, then see how that level tests out.

malikarshad

Originally posted by dave shepard
Do you have your reciever sub setting at -5 and the xo setting at 80. if the sub setting is too high then you could be getting distortion comming through. Do you have it hooked up through the speaker wire or sub out? Try to reposition the sub even the slightest move can make a differance.
Dave

The sub level is -5db on the receiver and XO is 80Hz on the Denon 3803. The Sub is connected via sub preout of receiver to the Left Channel input of Pb2+. The gain control is about little less then 1/2 about 75 degrees from 0 position with half position being 90 degrees.
I don't have a lesiure of sub placement in different location given my living room size (16 x 14) and the size of Pb2+. The sub is about 2 feet away from the back wall and 6 inch away from the left wall. I guess I don't have a choice of sub placement.

GregBe

The needle will always fluctuate a little on the sub frequency, but 10 dB is quite a bit. Since you already own Avia, run some of the low frequency sweeps with your meter. Do you have huge peeks and dips? If you do, I would recommend either moving the sub around (which it appears you can't), or go with some sort of equalization. When I flattened out my freq. resp., it was the biggest improvement to my system I made. I did three thing to flatten mine out. 1) moved the sub a little 2) I have a one band parametric equalizer on my sub 3) I created a cascading crossover using both the crossover on my sub and my receiver to flatten out a huge peak at around 75 hz (this was my biggest improvement).

Greg

EricH

I'm running a corner loaded PB2+ with Rane PE-17 PEQ. My FR is fairly flat, and the needle still moves around quite a bit. I wouldn't worry about it, just set your level to your personal preference.

Dr. Spec

3) I created a cascading crossover using both the crossover on my sub and my receiver to flatten out a huge peak at around 75 hz (this was my biggest improvement).

You can thank the dissimilar slopes in your pre/pro BM circuit for that peak at 75 Hz. Nice work - cascading can work in the right hands and if you can evaluate the results. Otherwise I recommend against it - too much potential for disaster.

GregBe

Originally posted by Dr. Spec
You can thank the dissimilar slopes in your pre/pro BM circuit for that peak at 75 Hz. Nice work - cascading can work in the right hands and if you can evaluate the results. Otherwise I recommend against it - too much potential for disaster.

Well, I don't have the most sophisticated testing methods, but when I run the frequency sweep on Avia, there is a distinct visual and audio jump when it hits 75 hz. I think it was in the neighborhood of 10dB. When I put the crossover on the sub as well as the receiver to 80, the sweep through the crossover region is as smooth as a baby's bottom. More important, the bass is tight now, and not boomy.

I agree with this not being for everyone. I almost didn't post it, but if it worked for me, it may work for others.

Greg