SVS PC ULtra arrived today. 1 question.... (1 Viewer)

[Joe Ferrari]

I have everything hooked up and used Avia to calibrate. The reference 85db was too loud so I used a reference of 80db. The sub was a tad hotter at maybe 82 possibly 83db. Anyway while watching the Matrix the suggested scenes were TOTALLY different from yesterday when I watched them with my old sub. Very good indeed.

My question revolves around the THX opening of the Phantom Menace. I'm not sure at my reference level if it's bottoming out or if it's the way it's supposed to sound. In theory if my reference is say 83db is it possible to bottom that sub at that volume? Could it be the way it's supposed to sound? It doesn't sound like a loud crack but it isn't "smooth" initially. I tried it again at -3db and the same effect.

Thoughts?

Joe

 

[Zack_R]

IIRC,this particular passage is recorded hot and low but the subsonic filter should keep that from being a problem.

Are you running mismatched tuning and subsonic filters by chance?

by dropping -3dB you have reduced the amps power requirement by 50% so I would think the way it's sounding is the way it's suppose to sound. Provided of course you are not running mismatched tunes.

Are you adding corrections into the spl for bass? 82-83 dB for subs is actually around 85dB. So if you are watching movies at your master reference level of -5dB then the sub is performing at reference levels.

 

[Joe Ferrari]

Hmm, I checked the subsonic filter and it was set at 16hz which is wrong for my tune. It should have been set at 20hz. I'm not sure how much this would have affected it. It may have been switched when I moved it around.

Since Zack is saying the actual spl measured by the ratshack meter is a bit pessimistic with low frequencies, maybe I should reduce the level a few db despite the fact the machine gun scene in the matrix gave me a wonderful back massage

I'm afraid to try it again. I don't want to damage the woofer......

J.

 

[ScottCarr]

Joe,

Congrats on the PCU. When I upgraded from the PB12/2 to the PCUs I had to completely rebalance/recalibrate my subs.

Rebalance meaning finding the best sub out level on the receiver and gain level on the sub. I had some awful listening experiences when I first connected the PCUs. When I went back and sifted through some of Tom V emails I discovered them.

A couple of things I discovered.
DVD player PCM was on.
Receiver bass limiter was on causing me to use the more gain to driver the PCU.
Sub to fronts - phase adjustment was required. I was overdriving the sub to overcome the cancellations. This was discovered during the recalibration.

The horrible clacking sound was disturbing. But after a careful detailed calibration I now enjoy some great bass.

The most important thing I found was calibrating the sub to the fronts to reduce the amount of cancellation. Once that was accomplished the PCUs simply roared.

Good Luck
Scott

 

[Joe Ferrari]

Thanks Scott. I am using a coaxial connection from my Pamasonic RP 91. I'm not sure how to tell if PCM is on or not.

I am also using an Outlaw 950 and all sub settings, midnight modes etc are off.

I played around with the phase a bit and found that "0" worked best. I have my ROcket 750's filtered at 80hz. Would the cancellation still be a big issue if they don't produce the sound?

FWIW, my amp gain knob is set at maybe 1/3

 

[Edward J M]

The Avia calibration tones are mastered at 20 dB UNDER reference level.

So an 85 dB level on Avia = 105 dB on a regular DVD. Then factor in the additional 10 dB boost the LFE channel sees, so you are at 115 dB. And to add insult, the THX Cavalcade trailer (which uses the LFE channel for the exploding globe) is mastered obscenely hot.

So even with you dropping 5 dB on the overall calibration (but still running the sub a tad hot), you could still be asking the sub to hit maybe 115 dB at the listening position at reference level on that passage. Don't believe it? Set the meter to c-weighted fast on the 110 dB scale and read the peak level when the globe explodes. Then add about 3-4 dB to that reading to compensate for the c-weighted filter in the meter.

With the mismatched tune configuration, I'm not surprised it sounded strained on that passage. Always match the port and tune switch; a mismatch will increase the chances of bottoming the woofer.

 

[Joe Ferrari]

Thanks Ed. I set "my" reference level to 80db, not that it will likely make too much difference. Any ideas on how to properly calibrate it so it doesn't bottom?

I have tried it at -20db, OK. -15db, Ok -10db and it bottoms out, at least that's what it sounds like. Remember my reference is -5db and I aimed for 80db output. I think it's just a track they put in there to squash all home subs. I think if I turned it down and adjusted it so it wouldn't bottom the rest of the soundtrack would be low on the bass.....

Thoughts?

 

[ScottCarr]

Joe,
Do you have a SPL meter? Just asking to be sure.

On the DVD menu check the audio settings.

Also, have you dropped SvS an email?

 

[Edward J M]

It is properly calibrated. It's the trailer - THX went a little wacko when they mastered that one. Just don't play it at -5RL - simple as that. You should be able to play the rest of the DVD at comfortably loud levels (near RL), and I have found PM to be mastered "about right". AOTC OTOH is mastered very hot - go figure. DVD mastering levels are all over the board. :frowning:

 

[steve nn]

(DVD mastering levels are all over the board.)

Ain't that the truth.

Quick question for ya Joe> What do you have your gain on the sub set to and what level is your SW gain on the receiver at? O, and are you using a Y?

I'm just trying to get a good idea on what your running at. I'm curious because I was quite surprised to be able to play the THX intro at -5/-8? myself with out bottoming with the PC-Ultra when I had it.

 

[Joe Ferrari]

The gain on my sub is set at 1.5 hashes below 12 o'clock. I am only using 1 input with no "Y" connector and my DVD player's audio section is flat. My outlaw is also set at zero with no gain. I had calibrated with Avia and an spl meter.

Joe