Svs pb2-isd setup problems

faster100

I decided to start my own thread as not to derail the other thread.. here is my awful curve ...

Airplay355

damn what a mess, i hope the doc can fix it for ya

Tour2ma

Faster, I know you're no novice, but has the look of a double filtered rig with the AVR crossing at 95 and the sub at 35.

I'll watch this thread with interest...

faster100

soon as the little one go's for a nap, in 5... im going to do another sweep.. and will post the results.. give me 30 minutes

steveinaz

Man, that's just plain cruel. Put the kids to bed, then test your subwoofer...LMAO!!!!

faster100

she sleeps through anything.. gotta teach em young...

PolkWannabie

Can you supply a few more details regarding how you've connected the sub, the settings on the sub, the related settings on the receiver/preamp etc.

faster100

The svs is connected via monster sub cable, plate amp set to -5.. avr sub channel volume 5, calibrated to 78-80 db... all ports open and tune switch at 25hz, corner loaded in front left corner (the only place for it) off to do some tests, I also just received my borrowed copy of avia from fed ex just now/.. Thanks

faster100

Ok i got it now... I just went ahead and started around 15hz because 10 and up werent even registering... ok hows this

faster100

I think this curve is much better with a weekness in the lower bass, Its tuned at 25 hz.. I'm going to tune it to 20hz and plug a port later and see what that brings me... will post the graphic then, any port that should be plugged?? or just the top port is fine..

monkeyphant

faster:
Have you tried adjusting the phase while you run a sweep at 70Hz?

MP

pjdami

Faster,

Are you starting off with the 100 hz tone, set the volume on the AVR till you get 83 db on the db meter? (to account for the 2 db correction to get to 85 db).

Start from 100 hz and go down from there once you have set the volume on the AVR. You may need to reburn your disk that way.

Your graph looks backwards to me. You should be getting some really good room gain with the sub in the corner.

monkeyphant

PJ
You know I thought about that the first time I saw Faster's graph...like its reversed or backwards.

MP

faster100

yes the first graph is backwards.. the second is correct... No i havent tried the phase yet.. but with the avia disk i did the sub/phase test tone w/ sub and left front./. and according to the instructions if the level doesnt change on the meter its in phase..

pjdami

Faster,

If the second graph is correct, and you are tuned at 25 hz, are you running the sub flat with the Avia calibration? Also what is your AVR LFE setting? I'm not seeing the characteristic "bump" in dbs at the tune frequency.

As far as the phase goes, what Avia tells you may not be the phase that gives you the flattest response (see Monkey's results over in his thread). This is a trick that Doc taught us.

I wouldn't plug any ports quite yet; somethings a little fishy with what you have right now. Almost looks like the sub is undercalibrated a tad. Do you have at least six inches between the back wall and the sub so that the ports can "breathe"? You don't want to restrict any air flow here.

faster100

I may have 6 inches back there, will have to look.. its close though.. The avr lfe setting is at -5, I will plot more tomorrow... thank you for all the help, just takes me longer to do things... I have 2 little girls full time so bear with me... be back in the am..

Dr. Spec

Nothing really to add here.......good advice thus far. I agree, play with the phase control and it might help knock out that hump at 50 Hz. And it looks undercalibrated a bit. He's getting decent extenstion to 23 Hz, which is correct for that tune setting. But the overall curve has a funny "feel" to it thus far. We'll get it right.

Maybe just add to check all your BM settings. All speaks to small, xo at 80, LFE channel at max, sub level at -5, bass limiters off, dynamic range compression circuits off in both AVR and DVD player, DVD player set to bitstream, and AVR recognizing DD and DTS including the LFE channel.

faster100

EDIT: what should the sub be calibrated to? I had all speakers to 75 db and the sub to just under 80 db on the rat shack meter.. am i undercalibrated??

Thanks Doc, I will check those setting today, they may have gotten messed up while i was messing with the setting for the dvd-audio player and disk i had, Thanks a bunch, and i want to get some peaks where thier should be peaks... so i'll work on this today...

monkeyphant

EDIT: what should the sub be calibrated to? I had all speakers to 75 db and the sub to just under 80 db on the rat shack meter.. am i undercalibrated??

Faster:
I set my speakers to 85db and the PB2 to 83db using the AVIA
calibration disc. I used the Subwoofer Volume segment where
the sub alternates with the Left Front Channel.

I didn't use the AVIA to do the Phase adjustments. I would use
the disk you are using now to do your FR sweeps. Like DOC said, start with a 50Hz sweep. Experiment with say 0, 90, 180 degrees and when you see an increase in volume at one Phase setting, go to the left and right in small increments until you get the highest reading. I didn't have very much time in the evening, so I would concentrate on a particular frequency and keep running the sweep and adjusting the Phase pot until the reading came close to the adjacent numbers, for example:

45Hz.........82db
50Hz.........78db
56Hz.........72db
63Hz.........81db
71Hz.........83db

I would run a sweep at 56Hz and adjust the Phase pot in small increments until the 56Hz reading came close to say 80db or so. Then I would move the Phase pot a little to the left, take a sweep when I saw the needle go below 80db, I know I had gone too far. Then I moved the Phase pot to the right in small increments. When I saw the needle go down again, I knew I had gone too far to the right.

DOC or PJ might have a better idea.

MP

faster100

wow, cool.. you guys are really getting into this and it will "help" me alot... I'm about to kick the kids off the 46" and start plotting...

Dr. Spec

Yeah, I have a better idea - TrueRTA QuickSweep. Hit one button, and boooweeep - she's done. :-)

Anyway, don't rely on just one channel for Avia calibration. Try them all. One channel is sometimes much higher or lower than all of the others due to phase and cancellation or reinforcement issues, and its proximity to the subwoofer.

monkeyphant

Anyway, don't rely on just one channel for Avia calibration. Try them all. One channel is sometimes much higher or lower than all of the others due to phase and cancellation or reinforcement issues, and its proximity to the subwoofer.

Don't rely on just one channel is right. You really have to do them all. I was just giving Faster an example of how I did one frequency. I used a Styke Audio Test CD to do my FR sweep.

Yeah, I have a better idea - TrueRTA QuickSweep. Hit one button, and boooweeep - she's done. :-)

I must have made 50 trips from the seating postion to the PB2 and back because I didn't have an assistant. This was over a period of several one to two hours evening sessions....by all means do every channel.


MP

steveinaz

So it appears proper subwoofer calibration is not only beneficial to your sound, it's beneficial to the cardio-pulmanary system as well...LMAO!:D

monkeyphant

So it appears proper subwoofer calibration is not only beneficial to your sound, it's beneficial to the cardio-pulmanary system as well...LMAO!

That's right. If you use the Stryke CD you only have about 20 seconds or so for each FR sweep. A simple procedure: play the tone, measure with the meter, put it down, run 17 feet to the sub tweak the Phase, run back to the meter, hold it up at a 45 degree angle, take a reading and write it down. All this in about 20 seconds! That's why it took me so long!

MP

kuntasensei

All of this is why I encoded my own custom DTS CD with 1/6 octave tones from 20-120Hz. My tones are encoded only to the LFE channel, ruling out any cancellation from other speakers. It also lets me test to see if a particular receiver's crossover is also affecting the LFE channel (and believe it or not, a lot of consumer grade receivers do). Once I get as flat a meter-corrected response as possible, I calibrate my sub 2-3dB lower than the other speakers to account for the Radio Shack meter's C-weighting. Works like a charm!

Shizelbs

What did you do to encode your own dts disc?

kuntasensei

There's a program called SurCode DTS that lets you encode any mono .WAV file to any channel of a DTS bitstream, in .WAV format. So you use a tone generator to create .WAV files at the frequencies you need, then use SurCode to encode them to the LFE track of a DTS bitstream. Then you take the resulting DTS-encoded .WAV files and burn them to CD as audio, just like you would any other audio CD. If you play this CD in a regular CD player, you'll get silence or noise... but if you play it in a DVD player with a DTS decoder, it will read as a DTS CD and play back in DTS.

Shizelbs

Thanks. I'm gonna check that out. It sounds really cool. I am sure I could waste a lot of time with something like that.

Dr. Spec

By virture of excluding the mains in your sub sweep, you will never know if have any phase issues.

While it certainly can't hurt to use the LFE channel only, it's also a good idea to use both main channels and the redirected bass to evaluate phase issues.

If the main speakers are set to large, evaluating phase interaction becomes even more important.

Unless your pre/pro has a separate xo function for the LFE channel, it will sum the LFE channel and the channels of any speakers set to small, and low pass them at the selected xo frequency.

Some pre/pros can set the LFE channel xo separately. In theory the LFE channel contains content to 120 Hz (at which point it is brick walled). In reality, there is very little content in the LFE channel above 80 Hz.

If you set the xo for the redirected bass to anything lower than 80 Hz (say 60 Hz for example), you risk lopping off some LFE channel content (again, unless you can set the LFE channel separately).

Ostensibly, the whole reason for setting an xo lower than 80 Hz is to prevent localization of the subwoofer on redirected bass. This would also necessitate lowering the xo for the LFE channel too, otherwise what's the point?

In the end, I never saw much utility in having a separate xo for the LFE channel for HT applications; 80 Hz works great for all RB and the LFE channel.

If anyone wants to evaluate the proper functioning of their BM circuit, Vince Maskeeper over at HTF professionally mastered/developed a set of 7 Dolby Digital test tones:

40 Hz - right channel
40 Hz - center channel
40 Hz - left channel
40 Hz - right surround
40 Hz - left surround
40 Hz - LFE at -10 dB
40 Hz - LFE at same level

If all your speakers are set to small and your BM circuit is functioning properly, the subwoofer will play every tone at the same exact amplitude except the "LFE same level" tone. Since the pre/pro automatically boosts the LFE channel 10 dB, this tone will play 10 dB louder than all the other tones.

This is a free download right from one of Vince's posts in the Speakers and Subwoofers section, and is a big confidence booster for anyone checking their BM circuit. Do a search for it, because I don't have the hotlink.

Probably 8 months ago at least.

Doc

kuntasensei

By virture of excluding the mains in your sub sweep, you will never know if have any phase issues.

Absolutely, but getting the response of just the sub by itself gives you a baseline from which to assess cancellation/phase issues for each speaker. In other words, you can get flat response from sub only, then take frequency response readings for each individual speaker with bass management active if you wish (by encoding those identical tones to each of the 5 other channels in a DTS bitstream). This lets you see which individual speakers are causing frequency cancellation so you can play with placement/time alignment to correct them. It's a handy tool to have, and it was free to create.

Or maybe I'm just really anal and like to tweak.

Dr. Spec

Originally posted by kuntasensei
Absolutely, but getting the response of just the sub by itself gives you a baseline from which to assess cancellation/phase issues for each speaker. In other words, you can get flat response from sub only, then take frequency response readings for each individual speaker with bass management active if you wish (by encoding those identical tones to each of the 5 other channels in a DTS bitstream). This lets you see which individual speakers are causing frequency cancellation so you can play with placement/time alignment to correct them. It's a handy tool to have, and it was free to create.

Or maybe I'm just really anal and like to tweak.

I agree 100% - on both counts. I'm the consummate anal tweaker; I spend more time testing and measuring than I do listening. Assbackwards when you think about it, but fun for us tweakers nevertheless.