PB2-ISD Calibration

monkeyphant

I've had my new PB2-ISD for about a week now and I am having problems calibrating it. The bass response is not very good. I have been working with SVS. It was suggested I try a couple of bassy scenes at say 10dB under RL and record the SPL at the key seating position and other alternative locations around the room. (Marked with an 'X'). The drawing is in the test area
http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=17758
According to SVS, "my HT layout is one of the worst case scenarios for bass performance at the primary seating position. I have the opening to the room directly behind the listeners and the subwoofer is approximately five meters away." I took some measurements at three locations: Left Rear, Right Rear and Right Front. I used LOTR, Iron Giant and U571 as test material:

LOTR: The Ring Drop
Iron Giant: Iron Giant fires on Battle Cruiser
U571: German Sub under depth charge attack after destroying
merchant vessel (highest SPL)

..........Primary..............................................Front
..........Seating..............................................Right
..........Position.....Left Rear....Right Rear......Next to Rack

LOTR...94db..........92db...........98db .............95db
IG.......96db..........95db..........102db..............99db
U571...95db..........99db..........102db..............98db

Avg.....95db..........95.3db.......100.6db...........97.3db

These measurements were taken at -10db below RL with the AVR at -6 and the PB2 calibrated at 75db, Phase at 0. With LOTR and U571, I turned the gain on my surround channel power amps all the way down; -10RL was simply too loud.

I'm sure I would get even better performance at the right rear if I adjusted the phase and increase the PB2 calibration by a factor of +2 to +6, which seems to be the normal "hot setting" for SVS users.

The question is if I relocate the PB2 to the right rear location between the loveseat and bookcase, should I be concerned about localization problems. Should I plug one port or leave all three open?

MP

Airplay355

pics would greatly help if u can do that

PolkWannabie

See drawing in forum testing area.

monkeyphant

Thanks, PolkW

http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=17758

PolkWannabie

So any way ...

What's behind the TV/Projector and Towers ? A large window ?

Given where the rooms only opening appears to be, does it make sense to organize the room with the front sound stage being at what is the top or bottom in the drawing ?

tryrrthg

what are you using for calibration? If it is Digital Video Essentials then your sub may be calibrated too low, as that disc has some problems. Other than that you may be sitting in a null, try checking the bass through out the room. The other thing might be your sub's phase. Try rotating the phase knob until you get the loudest bass.

monkeyphant

What's behind the TV/Projector and Towers ? A large window ?

No, there is a wall. The front soundstage consists of two tower
speakers, a center speaker, the rack, the PB2 and the projector
screen.

Given where the rooms only opening appears to be, does it make sense to organize the room with the front sound stage being at what is the top or bottom in the drawing ?

You're right it doesn't. The screen and projector were added last. I need the distance from the sitting position to the front wall because of the projector. Even though it has a short throw, I need to be about 15 feet from the screen.

what are you using for calibration? If it is Digital Video Essentials then your sub may be calibrated too low, as that disc has some problems. Other than that you may be sitting in a null, try checking the bass through out the room. The other thing might be your sub's phase. Try rotating the phase knob until you get the loudest bass.

I used the old VE for calibration. Changing Phase didn't seem to
help.

Looks like I may have to seal off the entrance...

pjdami

MP,

Per the good ole Doc (as he suggested to me) I would start off with no ports plugged (all open) and the subsonic filter set at 25 hz. 0 deg phase is okay to start off with. In this configuration my PB1+ actually digs nicely down to 20 hz and has plenty of room to breath.

Sounds like something in your calibration isn't correct. What DVD disk are you using for calibration?

Also what are the dimensions of your room.

One other thing you can try is to take the sub out of the corner (although you should be seeing room gain there).

Move the love seat to the opposite side of the room, move the chair to the opposite side as well (where the love seat currently is), and move the sub along the middle wall closer to your gear rack (where the love seat currently is).

You might also want to burn a sweep test disk since you have a decibel meter and take some in room FR and graph it.

You can download the 1/12 octave test tones here and burn a disk:

http://beyond_gomer.tripod.com/

Send me a PM w/ your email if you want a copy of the excel spreadsheet I made with the interpolated correction factors.

Good luck. These things take a lot of patience sometimes but eventually will reward you for your hard work.

tryrrthg

Well Doc may know for sure but if the old VE is anything like the new DVE then the sub calibration tone is too low. I believe doc said with DVE you have to calibrate your mains to 75 and then calibrate the sub to around 88 dB's to be flat...

My only other suggestion would be to try putting the sub near your listening position and then walk around the room listening for the best bass, then put your sub in that spot.

pjdami

I used the old VE for calibration. Changing Phase didn't seem to

Oops. Sorry I missed that. Yeah the new DVE is about 10 db too low for the bass calibration. Doc had a nice writeup about it over at HTF. Not sure about the older VE disk.

pjdami

MP,

Your setup really doesn't look too bad to me.

The other thing that can be going on is that you are in a big null on your calibration test tone for the sub. This is usually around 45 - 50 hz. The only way to know for sure is to run a sweep test and plot the in room FR. The other thing you can try is leave the gain on the plate amp alone and move the sub to where I told you (where the love seat is now near the gear rack) and run the calibration test tone again and see how much higher the db reading is at that location.

monkeyphant

Thanks guys for your responses...
PJ
The room is 15 x 17 with 8 foot ceilings which is about 2000ft3.

The other thing that can be going on is that you are in a big null on your calibration test tone for the sub. This is usually around 45 - 50 hz. The only way to know for sure is to run a sweep test and plot the in room FR. The other thing you can try is leave the gain on the plate amp alone and move the sub to where I told you (where the love seat is now near the gear rack) and run the calibration test tone again and see how much higher the db reading is at that location.

I never considered moving the one loveseat and chair to the other wall. I have a Stryke Test Disc. Do I need to really run the sweep test at reference level? I want the best bass response at moderate listening levels (WAF).

MP

pjdami

MP,

I was running the first test tone at 100 hz at 83 db to start off with (+2 db for correction factor = 85 db actual) but found that using 73 db at 100 hz gave me very similar results and was not as loud.

Actually, if your sub cable is long enough you might try moving the sub out of the corner and place it along the top side wall in that diagram. Run a sweep test in the corner first to see what you got. You will be looking for a null at 45 - 50 like I had here:

pjdami

I could never get the corner to work out in my setup. I eventually moved it to a side wall and got this overall flatter response.

The corner is usually the best place to try first but doesn't necessarily that it will be the best place (for me at least). I couldn't control the huge room gain there even with the PEQ. This was okay for HT but not okay for music.

Doc told me that any hump below 30 hz is fine because little music actually goes that low and its "free" oomph for HT.

Here's what the FR looks like for me along the side wall. I am very pleased with this for both music and HT applications. the corner may be revisited again but I have to get my learn on those Behringer equalizers to do that.

Dr. Spec

The bass response is not very good.

Could you explain this a little better? Does the sound quality of the bass disappoint you? Or is it simply a matter of not enough volume/pressure/power?

If the SQ is poor, I agree a FR sweep is needed to see what is happening in the room Paul spent a HUGE amount of time tuning his sub and experimenting with placement and it paid off - he has a nice looking curve.

If the volume/pressure/power is insufficient, then simply turn up the gain at the amp until you are satisfied. Keep all 3 ports open and the tune switch to 25 Hz. It's pretty hard to hurt a PB2-ISD in that size room in the 3/25 tune. You could probably safely run it another 4-5 dB hotter if you keep the overall Master Volume at -10RL or lower (and that sounds like the case).

Doc

monkeyphant

Thanks PJ for your replies and posting the graphs. I really appreciate it...

If the volume/pressure/power is insufficient, then simply turn up the gain at the amp until you are satisfied. Keep all 3 ports open and the tune switch to 25 Hz. It's pretty hard to hurt a PB2-ISD in that size room in the 3/25 tune. You could probably safely run it another 4-5 dB hotter if you keep the overall Master Volume at -10RL or lower (and that sounds like the case).

So I could run the PB2 at +6 to +11 (81db to +86 using OVE) at moderate listening levels and still hear and feel the bass? At 4-5 db hotter than RL is where I seem to have the problem. On some bass-loaded DVDs, there is definitely insufficient pressure.

MP

Pauly

Hmmmm... My room is 27' by 11 1/2' with 9 foot ceilings ( i might have thought the ceilings were 10' at 1st but just measured and they arent) and my pb1 does a kick **** job for the size of the room. (Its a 1930's Fl style Bungalo with solid walls) I havent done a sweep yet and of course there are nulls here and there but to be dissatisfied with your sub doesnt sound right in my head after hearing fasters pb2. I would go with running it on the hot side as sug. Let us know what your set ups and outcome is.


Spaz

Dr. Spec

You said you were using the older VE for calibration, but then you referenced DVE above.

If you are using DVE, you'll need about 88 dB on the sub for calibration to get a flat response. The disc has a major encoding error.

Regardless, if all you are missing is some pressure and impact and you are otherwise happy with the sound quality of the bass, leave it in the 3/25 tune and start increasing the sub level like 2 dB at a time until you are satisfied.

Let us know where you end up for an overall sub level in comparison to the surrounds on your calibration.

monkeyphant

You said you were using the older VE for calibration, but then you referenced DVE above.

Naw, I said OVE.

O.K, DOC, I'm going to take some time off from work and spend a day experimenting and I will let you know how things turn out.

MP

---

Doctor: She's in a coma.
Midget Patient: I am not, I'm in a bed!
Midget looks at the 3 Stooges.
Midget Patient: Jeez, the joint is haunted.
Moe to Midget: Why, how old are you?
Midget Patient: Why, I'm 35 years old.
Curly to Midget: Why you couldn't get that fresh in 35 years.
Doctor to the Stooges: You call yourselves Doctors. Why you don't even know how to deliver a proper anaesthetic.
Moe: Boys, give the Doctor an anaesthetic.
Doctor gets hit on the head with a mallet. Almost loses consciousness.
<Bell sound effect.>
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Midget hands stooges 3 cigars.
PA System: Calling Doctor Howard, Doctor Fine, Doctor Howard...

Dr. Spec

Originally posted by monkeyphant
Naw, I said OVE.

Sorry, I noticed the "O", but assumed it was a typo. Now looking at my keyboard, "O" and "D" are nowhere even close together.

Good luck with recalibrating. Tastes in bass and overall playback volume vary greatly. What is loud to one person, might be barely enough for another. Noted bass junkie and SVS co-owner Ron Stimpson runs his subs about 5 dB hot for HT.

Unless you have a nasty room null, I'm hoping this might be solved simply by wicking up the gain on the PB2-ISD a bit.

The PB2-ISD is a rugged sub; within reason I would put away the SPL meter and just playback some tracks at your preferred Master Volume setting (not necessarily -10RL) and keep increasing the gain at the sub until the bass is hitting hard enough to make you happy.

Give your ears a break occasionally to prevent fatigue and overcalibration, and try several different DVDs. You'll quickly fall into a sweet spot where you like the power/pressure, but it's not overwhelming or overbearing.

THEN go back and take a calibration reading with VE and see where you ended up. Sometimes just running 3-4 dB hotter can make a huge difference in impact and power.

You may find your HT setting is too hot for music, and that's normal; I have different settings in my AVR for HT and music and the music setting is about 3 dB cooler.

Doc

PolkWannabie

Originally posted by pjdami
You can download the 1/12 octave test tones here and burn a disk:

http://beyond_gomer.tripod.com/

When using something like this should measurements be take at the listening position ? or 1 meter out from the speakers/sub ?

tryrrthg

Originally posted by PolkWannabie
When using something like this should measurements be take at the listening position ? or 1 meter out from the speakers/sub ?

You can do both. the 1 meter out will give you more of what the sub's frequency response will be (without room interactions). at the listening postition will show you what the room is doing to your freq. response.

pjdami

PW,

I take the data to do the frequency response curves from the primary listening position. In this case, nulls and peaks in the frequency response will be evident. I use the primary listening position data to move the sub around for placement because that is what you will be hearing when listening to the sub.

The 1 meter readings you are talking about are called "near-field" measurements. Doc told me once I could take my sub outside or in a large garage to do this (if practical) and this tends to eliminate the room nulls / peaks. Near field measurements are good for seeing what the sub can do without room influences.

Monkeyphant,

Taking off of work to play with the sub:D Very cool you are able to do that. Sounds like fun and Doc's come to the rescue with some good advice. I know what you are after. PWC membership. Should be very attainable in that sized room that you have. Remember though ... patience.

Paul

pjdami

Originally posted by tryrrthg
You can do both. the 1 meter out will give you more of what the sub's frequency response will be (without room interactions). at the listening postition will show you what the room is doing to your freq. response.

Yeah, good call tryrrthg.

PW, like tryrrthg said you can also do the "near-field" in the room with the sub instead of moving the sub outside. I think the point of moving the sub outside or in a large garage was to mimic an anechoic chamber. But for moving the sub outside this may not be very practical.

PolkWannabie

Nearfield measurements and comparisons are I suspect are what product reviews are made of but listening position measurements are where the rubber meets the road in terms of a particular set up.

monkeyphant

'

Taking off of work to play with the sub Very cool you are able to do that. Sounds like fun and Doc's come to the rescue with some good advice. I know what you are after. PWC membership. Should be very attainable in that sized room that you have. Remember though ... patience.

Thanks, pj....it's a shame DOC doesn't make house calls.

I take the data to do the frequency response curves from the primary listening position. In this case, nulls and peaks in the frequency response will be evident. I use the primary listening position data to move the sub around for placement because that is what you will be hearing when listening to the sub.

Just out of curiosity, I 'm going to do a FR curve from the primary listening position...maybe at about -20RL using a Stryker Disc. I want see where the peaks and nulls are with the PB2 in its current location.

MP

Dr. Spec

Thanks, pj....it's a shame DOC doesn't make house calls.

LOL! Actually I've made more than my share of them.

An FR sweep at the listening position is a great idea. I do both near-field and in-room to see how they differ, but in-room is really what counts.

Just make sure to use the RS correction factors. Paul can fix you up with a graphing spreadsheet that includes them.

Doc

pjdami

Just out of curiosity, I 'm going to do a FR curve from the primary listening position...maybe at about -20RL using a Stryker Disc. I want see where the peaks and nulls are with the PB2 in its current location.

Very nice. That would be great to see the in room FR of your sub. I think the only FR sweeps I have seen here have been Hbomb's, Doc's, Gatemplin's, and my own. Sorry if I missed any others.

Always cool to see what other people's in room FR looks like. The real world and how people go about resolving anomalies in response with positioning / controls / equalization / etc. A lot of things to be learned here for tweakers.

Sounds like a pretty good new thread actually. "Mug shot of your sub's In Room FR."

PolkWannabie

Sent you a PM for Excel Spreadsheet ...

tryrrthg

Here's my "mug shot" it's VERY UGLY! but it was pretty much me putting my DIY sub into place and turning it on. The graph is of my mains and sub running together. the mains are running full range, the sub's low pass crossover is set at 40hz. Test tones are in 1 hz increments from 90 to around 20hz. The SPL meter was about 8 feet from mains and 9 feet from sub. Room is 12' x 15.5' and pretty much open to the whole one bedroom apartment.

The curve would be real nice for EQ (if only I had one)! I haven't messed with the sub and settings much since I'm moving in two weeks.

monkeyphant

I did a FR sweep at the listening position last night with the PB2-ISD in the left corner using only the subwoofer. Thanks to Paul for his spreadsheet and graph! The AVR Master Volume was at -20 RL. I am wondering if the dip in the curve between 63 Hz and 80 Hz is a problem:

SPL (comp)
67.5....15Hz
77.0....17.5Hz
88.5.....20Hz
94.5.....22Hz
98.0.....25Hz
99.0.....28Hz
98.0.....32Hz
94.5.....36Hz
85.5.....40Hz
83.0.....45Hz
85.5.....50Hz
83.5.....56Hz
78.5.....63Hz
72.5.....71Hz
74.5.....80Hz
89.5.....89Hz
86.0....100Hz

MP