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Discussion Starter · #1 ·
I just recently got an SVS PB2-Plus for my dedicated HT room. The room measures 19x20. The sub is currently set to 16Hz with 2 ports plugged and is properly calibrated with an SPL meter. I have the sub corner loaded and broke it in with a few of my demo discs.


It had no problems with any of the movies (LOTR, SW Episode II, Toy Story II, Monster's Inc...), but thanks to the new sub, I now have found parts of my room that I will need to go back and "nail" down a little better to get rid of any extra unwanted vibration...and I may no longer need my Buttkicker...almost.:D


However, when I threw in my Telarc DTS demo disc and played Jurassic Lunch I ran into a bit of a problem. I was playing at about -10 on my Halo which is calibrated to 75dB at 0. From my seat I could hear port noise and it wasn't subtle. It was strong enough to sound like a bicycle with a card in the spokes. I then went back and removed a second port plug and the noise dropped but was still audible. When I removed all three, it almost sounded like the sub was straining or close to bottoming out, so I turned it down. I plan to try some more listening with the sub tuned to 20 and 25Hz soon.


In the mean time I was wondering if others have tried this DTS CD with a PB2 plus or other similar subs and noticed if this CD is just way overcooked or if I need to set my sub up differently?Do I need to move my sub out more? Am I too close to bottoming out with this CD because it actually has a lot of info that my old Hsu VTF-2 simply could not produce? Either way, I should never hear that much port noise.
 

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weird, ...i have almost exactly the same setup as you in terms of main components...that is, the C2, A21, A51 (i realize you have the A52), and PB2+. I have experimented with it tuned to 16, 20, and 25hz along with 1, 2, and no ports blocked. I've tweaked the gain on the sub, the level on the C2, and the phase control. However, I've NEVER heard port noise, ESPECIALLY the level in which you described. I really don't know what that could be...maybe placement? Maybe a faulty driver? Maybe the BASH amp is malfunctioning? I'm sure Ron or Erik at SVS could help you very quickly if you hit them up.


By the way, I just wanted to tell you how awesome your home theater looks. My god, you put the THEATER in home theater.


BTW - why did you choose to go with the A21 and A52? Is there a reason you chose 5 of your 7 speakers to be less powered than your mains?
 

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Check out mingL at the HTF forum. He has some waterfalls of that passage and I believe that some of the footsteps go down to 5Hz with their peaks at 10Hz.


This may be pushing the PB2+ limits quite a bit. How close are the vents from any boundry? It may be the air hitting the boundry.


Tom V or Ron S will probably chime in soon but I am of the thought that it is that the sub is straining to produce sounds that most speakers can not even attempt to produce.
 

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Discussion Starter · #4 ·
Quote:
Originally posted by nicholtl
weird, ...i have almost exactly the same setup as you in terms of main components...that is, the C2, A21, A51 (i realize you have the A52), and PB2+. I have experimented with it tuned to 16, 20, and 25hz along with 1, 2, and no ports blocked. I've tweaked the gain on the sub, the level on the C2, and the phase control. However, I've NEVER heard port noise, ESPECIALLY the level in which you described. I really don't know what that could be...maybe placement? Maybe a faulty driver? Maybe the BASH amp is malfunctioning? I'm sure Ron or Erik at SVS could help you very quickly if you hit them up.


By the way, I just wanted to tell you how awesome your home theater looks. My god, you put the THEATER in home theater.


BTW - why did you choose to go with the A21 and A52? Is there a reason you chose 5 of your 7 speakers to be less powered than your mains?
I am guessing it is the DTS CD. This thing bottoms out my buttkicker as well. However my buttkicker also starts to bottom out with the openning scene of Lord of the Rings and Star Wars Episode II, but the PB2-Plus handles these fine with no port noise.


Thanks for you comment on my HT room. It is still a work in progress and new pictures will have to be taken with the SVS. The only reason I went with the A52 was money. I figured that the A52 can power my center and 4 surrounds. Since all are set to small and since the surrounds (especially the rears) usually do not get as much info, more power is left for the center. However, I wanted to give the mains as much clean power as possible, since they will double up as full range speakers for stereo music.
 

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Discussion Starter · #5 ·
Quote:
Originally posted by jdhdiggs
Check out mingL at the HTF forum. He has some waterfalls of that passage and I believe that some of the footsteps go down to 5Hz with their peaks at 10Hz.


This may be pushing the PB2+ limits quite a bit. How close are the vents from any boundry? It may be the air hitting the boundry.


Tom V or Ron S will probably chime in soon but I am of the thought that it is that the sub is straining to produce sounds that most speakers can not even attempt to produce.
Wow, thanks...Can you supply me with a link, since I am not a member of that forum and am not very familar with their setup. I have tried moving it out and that does not help much. It is just that the drivers are trying to push sooo much air through the port that it is making all this noise. It sounded like Hurricane Isabel. :D Even with 2 ports open it was making some noise. I think the sealed ports are helping to keep the drivers in check, by not allowing them to go up and down all the way. With all three open I would be afraid that the drivers would be able go all the way without any resistance.


Last night I went back and openned 2 ports and set the sub to 20hz. This eliminated virtually all of the port noise. This is probably because the slope drops off more rapidly and it is no longer trying to produce the 5-10Hz signal. I would love to see the waterfall for this disc!!!
 

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Heya Max. I don't know what their ports are made of now but I had a similar noise with my old school 20-39CS. After some inspection of the port tube, I noticed a small piece of paper/cardboard/whatever was vibrating. I ripped it off and all is fine now. For a little piece of 'paper', it made a hell of a noise...


Sean
 

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Discussion Starter · #7 ·
Hmm, I will have to go back and inspect the back of the sub a little closer with a flashlight...if I can pull it back out. I could barely get this beast out of the box and I had to call a friend over to help me carry it upstairs! But do you think it odd that it only has port noise with this disc?!?
 

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Discussion Starter · #8 ·
bump....
 

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I've been playing with the Jurassic Lunch track off the "The Great Fantasy Adventure" album...


I haven't tried the 16Hz tune, but in the 20Hz tune with one port plugged, I am unable to produce any port noise, just crazy door banging... :)


I'll most probably play with the tunes more as soon as I get a receiver - should be here in a week or two... Calibration with regards to tuning points is a bit impossible when the sub is connected via high level inputs - the gain knob is too sensitive.


Otherwise, PB-2+ rocks, no doubts about that...
 

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Discussion Starter · #10 ·
The Jurassic Lunch I have is from:

http://www.telarc.com/dts/title.asp?...H3AU0PD9XQ0AX9


I can produce port noise when tuned to 16Hz one port unplugged, or 20Hz two ports unplugged, but I have not tried tuning to 25Hz yet. I switched port plugs just in case it was something in or just behind the port making the noise, but it still does this...LOUDLY.


My friend came over and it scared him. He had never heard port noise before then. He has made some DYI subs and suggested that either it is a bad design (hope not) or possibly that the amp is not bypassing the lower frequencies correctly even when I switch from 16 to 20Hz, but I let him borrow the DTS CD to rule that out by seeing if he could any port noise out of his sub.


Hopefully Tom or Ron could chime in with some words of wisdom about the sub or personal experiences with the DTS CD.
 

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When you said "calibrated to 75dB @ 0" on your Halo processor, does this include the subwoofer?


Remember the RS meter needs a correction to the response curve, about 3dB for a subwoofer to be accurate. As such, you actually need to calibrate to 72-73dB on the RS meter.


If not, you're running the sub 3dB hot, and this could be pushing the sub to its limits. Although 3dB isn't perceptually huge -- ~10dB (depending on frequency) is required for a perceived doubling. However, the 3dB equates to 2x the power/excursion.


Regards,
 

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Hi Max,


With high output bass in the 5hz range...port chuffing wouldn't be a total surprise..:) If it is reduced by tuning the enclosure higher...than chances are the subwoofer is fine(nothing loose in the inside of the port)...and 5hz at high volume levels is just a bit much to ask of it. Some of the DTS demo discs were recorded very hot too....but I don't think I have had a chance to measure this particular disc yet.


How large is your listening room and does it have any large openings to other areas of your home? Where is the PB-2 located(in/near a corner) and how far from the key seating positions is it?


Also, we can send you a third port plug, or you can just stuff a towel in the third port. But I would suggest sealing all 3 ports for a minute to make sure what you are hearing is truly *port noise*. Port noise can be loud enough to be audible...but the way you describe it (actually scaring your friend for example) makes it seem like an unusually severe case.



Tom V.

SVS
 

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Discussion Starter · #14 ·
TV/ John K,


Thanks for the responses. I do have the sub calibrated to roughly 75dB with the SPL meter. I did not do the sub adjustment because I was not sure of the exact frequency of the sub test tone with the Halo. Do you know?...or what about Avia's?


My room is 19x20 with an 8ft ceiling. It is a dedicated room with a door as the only way in. The sub is currently corner loaded against a false wall I constructed for my screen. I was considering cutting a hole out and placing the sub half-way behind the wall since it sticks out soo much. You can click on my link to see pictures of the HT room. My first row of seats are about 9ft from the sub. The current picture has a Hsu VTF-2 however. :D


The noise is definately the port. I can put my hand back there, and it is forcefully enough to blow some serious wind on it. Shouldn't the various tuning frequencies reduce the amount of response below the tuned frequency? I would have thought that tuning the sub to 20 would almost elimate any usable 5Hz signal. When I have some more time I will try out more sub setups and more DVDs but so far the only problem I have found is with this disc.


I would love to hear from someone who has this disc and would love to see the waterfall chart if someone can provide me with a link! Would the more breaking in increase or reduce the port noise?
 

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Max,

Here is a waterfall chart for the CD version... (The site is a new idea of mine :)


And now I remember... A friend brought this particular DVD here two weeks ago, we did blow Jurassic Lunch thru... But it was in the 25Hz tune, so... Everything was OK... Expect the room :)


It really is impressive, even in the 20Hz tune... It just goes does a little *poof* and then a shockwave goes thru the room and the door goes *poot poot*... Aaaah. :)


Rudi
 

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Max,


It's equal energy distribution per octave (Pink noise).


If you average the correction for the 20, 40, 80 and 160Hz values you'll come up with something around 3dB for the correction. I'm not looking at the chart to be exact.


Regards,
 

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Discussion Starter · #17 ·
Well, I found the waterfall plot for Jurassic lunch, but this was the CD version, not the DTS CD.

http://www.hometheaterforum.com/htfo...hreadid=144887


I wonder if this DTS CD did not take into account the 10dB boost that Dolby Lab decoder adds to the LFE channel. This would mean that the LFE is getting 10dB louder signal than it should. I know some older DTS CDs did not take this into account. Do you know if this might be one of them?
 

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Max


Sorry I don't have a copy of the disc you are using. Sounds kewl though.


However I am curious if you have tried stuffing a towel in the third port as TV suggested?
 

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Discussion Starter · #19 ·
Not yet...(I'm still at work). I may try it tonight just for Jurassic Lunch, but I do not plan to keep it in there. Having the towel in would probably drop the maximum SPL response of the 16Hz tuning even more, and we can't be having that! :D
 

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Discussion Starter · #20 ·
UPDATE

Well, last night I did not get to try the towel, but I put in ATOC openning scene and turned off my two amps so that the only thing going was the PB2-Plus. My friend suggested that there might always be some port noise, but that it is just more audible in Jurassic Lunch since the only thing going during most of that demo is the sub. So this test was done to see how much port noise there is when no speaker is on.


What I could hear was nothing but clean bass. Even from a few inches away with my hand near the port I heard zero port noise. However, my room was shaking and with no speakers on, it almost felt like a thunder storm. :D


My friend now has the Jurassic Lunch disc to try with his sub. He was guessing that his sub's (tuned to 18Hz) subsonic filter would filter out most of the bass around 10Hz, but I reminded him that even with my filter set to 20 I was getting port noise. I still think that is a bit odd.


BTW....does anyone know the port length of the PB2-Plus? We have a basic program that determine's the port length/size needed to eliminate chuffing when tuned to a specific frequency. This program will not account for the specific driver, but I would like to see what the measurement comes to with generic drivers in the formula.
 
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