PB2-ISD Calibration

pjdami

One more thing faster. that spreadsheet will only work with the BeyondGomer website 1/12 octave test tones starting at 100 hz.

Not sure which test tones you are using. You only have to go to track 36 out of 41 which is 13.3 hz. I didn't bother going all the way down to 10 hz on the spreadsheet.

monkeyphant

After you calibrate to 83 dB with all ports open, up the sub level 1.5 clicks at the AVR when you plug a port. This will mostly compensate for the volume lost above the tune point

I calibrated the PB2 to 83 db, plugged the 3rd port and re-calibrated the PB2 using the AVIA Disc. I had to adjust the AVR sub-level one click (from -7 to -6) to get the PB2 back to 83db (my AVR range is from -15 to +15). I also dropped the tune switch, like you recommended.

The PB2 plate amp volume is one click before 1/2, the phase is at 80 degrees, not 45 like I originally thought. I had a better view of the Phase pot when I moved the PB2 away from the wall to plug the port. The AVR RL is -15. The FR sweeps were taken at -20RL.

It should troll deeper than sin with a port plugged.

I didn't have a chance to test any film material. My day starts at about 3:30 A.M., so I generally sack out at around 9:00 PM. or so.

Even with the sweep tones, it trolled deeper...

MP

tryrrthg

for anyone interested I have an excel spreadsheet that works for 1 hz increments from 10hz to 125hz and automatically graphs your results. The test tones come from this site:

http://www.snapbug.ws/sinewaves/

Problem is I'm at work and shouldn't email it too much. I can email it to one person and they can distribute from there if they wish...

Dr. Spec

I calibrated the PB2 to 83 db, plugged the 3rd port and re-calibrated the PB2 using the AVIA Disc. I had to adjust the AVR sub-level one click (from -7 to -6) to get the PB2 back to 83db (my AVR range is from -15 to +15). I also dropped the tune switch, like you recommended.

When you get to this level of sophistication in doing FR sweeps, rely more on the graph than on Avia. As you can see, even with a 1 dB increase in the sub level, you are still at a lower level across the board; that's why I recommended 1.5 clicks and even then it might not be enough.

I'd go up another click at least if you want to nearly match your 25 Hz tune mid bass output levels.

You'll lose a bit of that pounding power at 25 Hz with a port plugged, but the overall curve is actually better looking with still decent room gain, and you really picked up a TON of low end.

It might not seem much until you realize a 10 dB gain at 20 Hz is more than twice the amplitude and actually 10X the sound pressure. And the gain at 15 Hz is even more dramatic; about 15 dB - WOW. You will definitely feel that on certain DVDs. I would play Revolutions again and certain scenes will have noticeably more infrasonic "feel" (pants waffling and room pressure) to them.

There will be a limit to how much air the twin 3" ports can flow without port noise, but it's still pretty damn high. After all, Ron-P uses twin 3" for his 15" DIY Tempest tuned to 17 Hz.

Bottom line, SVS gives you the choice, If you want to crush your face in with major 22-27 Hz impact, leave all ports open. If you want a bit more sedate (but still killer) sonic presentation with a huge infrasonic boost, then run the 20 Hz tune.

The 16 Hz tune will actually be flat to about 13 Hz in-room, but the trade-off in port area isn't worth it IMO. It's cool to run the graph, though.

faster100

sorry for not getting back last night.. "something" came up, and it was late, So Doc what ya think of that stinky curve i have posted?? I have to work on this today if i ever get a spare moment from my kids....

Dr. Spec

The curve looks bizarre, faster. I would make sure the data and equations are good before you continue. Something doesn't feel right about that graph.

faster100

me at the controls is not right ... maybe my disk tones were messed up? i mean the meter dipped to nothing when it was going through a good portion of the disk freqs.. the first several werent even registering, hence the 55 db readings... where should i really start the test? at like 15hz? if so, what number tone is that ie: 5,10, or somewhere close


edit: let me start my own thread so i don't derail this one, sorry

monkeyphant

Doc:

...that's why I recommended 1.5 clicks and even then it might not be enough. I'd go up another click at least if you want to nearly match your 25 Hz tune mid bass output levels.

Raising the sub level another click nearly matches the 25Hz tune mid bass output, but not enough, especially at a moderate listening level (-20RL). You are correct, one port plugged is a little more sedate, but I prefer all ports open at lower volumes.

Thanks DOC and PJ for all your help.

MP

Dr. Spec

Yes, all rooms are different. In your room +3 clicks on the sub level is probably perfect when you plug a port in order to match the 25 Hz tune level.

I have found the same thing at lower volumes - the sub "breathes" better with all ports open and has a richer and more effortless sound which I prefer for music, particularly.

At higher volumes on DVD, it doesn't matter as much and you will definitely see much better super low end with a port plugged. Your choice.

So - in the end - was all the tuning worth it? And how does the sub sound now? By the looks of that curve, I have a good idea of your answer. :cool:

monkeyphant

So - in the end - was all the tuning worth it? And how does the sub sound now? By the looks of that curve, I have a good idea of your answer.

Hmmm...+3 clicks, huh. I thought I was finished. Let me put the plug in and try it again.

MP

monkeyphant

I have found the same thing at lower volumes - the sub "breathes" better with all ports open and has a richer and more effortless sound which I prefer for music, particularly.

Even after wicking up the PB2 +3 with one port closed, I still came to the same conclusion: all ports open seems to work well for lower volumes....but, then again, it's nice to know I have the option to re-tune the PB2 if I ever desire to....

So - in the end - was all the tuning worth it? And how does the sub sound now? By the looks of that curve, I have a good idea of your answer.

I would say a definite yes--it was worth it! IHMO, you can't full realize the potential of the PB2 unless you run FR sweeps and calibrate...sure it can be time consuming; sure it can be a little tedious, but, oh yeah, it is worth it.