SVS PB10 Question(Port Noise) (1 Viewer)

[Bejoy]

Hi All,

I received my PB10 on Wednesday and has been playing with it for some time. This weekend, I popped in Dr. Chesky surround show DVD and it was awesome (great Demo stuff). There is a track in there with heartbeats at 40 thru 20 Hz. But when the 20 Hz track was playing (at -20dB), there wasn’t much effect and a lot of loud port noise. So my questions are
1. What should I be feeling at 20 hz? I was expecting to feel it more than hear it, but neither happened.
2. What’s with this port noise? Is it a defect or is it a limitation of this sub?

Bejoy

Note: My room is pretty big 15 X 18 with 18 ft ceiling and opening up to one side. I have corner loaded the sub and is driven by a Pioneer 1014 in an Athena ASF2 based system. I haven’t calibrated the system other than the Auto MCACC and a little bit of tweaking. The sub gain is at ½ way mark.

 

[John Garcia]

My room is ~19x20 with high vaulted ceiling (about 12'-14'), 50% gain, and I haven't heard any port noise at all.

 

[Mike^S]

When running test tones, I get port noise on my PB10 if I go above 95dB at 20hz. I thought this was pretty good, but now that I think about it, shouldn't I be getting better than that? My room is about 15x20x8.

 

[Mike^S]

If I do a sweep instead of a constant test tone it seems like I get better performance. What is the proper way to test a sub? Sweep or constant tone?

 

[David Mueller]

I have the same "problem" with my Front speakers,when they go down below 35Hz the make port noises(but also bass(a lot!!!)!!!) They go down to 28Hz@-3dB but there i have sooo much port noise But this is only with constant sine tones.

When I run through a THX-Bass Test(at really heavy output!!!)
there are nearly no port noises and it seems to play even deeper than 28Hz!!!

Tomorrow my PB10 will arrive . . . I hope he hasn't the same problem! I hate those port noises!



Does everyone of you have port noises with your PB10?

And there is no shaking @ 20Hz??? :frowning:

Greetz from Austria ,David

 

[Mike^S]

Oh no, there's definately things shaking in my room. In fact I live in a small studio, so everything in my kitchen is rattling. Still it seems like I should be able to hit 100 dB with no port noise.

 

[David Mueller]

At which frequenc?
Only with sine tones or even with movies and music?


Does it not play louder than 100dB?

David

 

[David Mueller]

My room is also very small . . . Only 5 x 3 meters . . .

Do you have bass @ every freq.?

 

[Mike^S]

I have not heard any port noise during movies or music. The only time is when I was running a constant 20hz test tone.

p.s. I just did a test at 40hz. Got 107dB, no port noise. My whole apartment was shaking violently. I'm afraid my neighbors will come pounding on my door. =)

 

[David Mueller]

Was it louder than the 20Hz tone?

 

[Mike^S]

Read edit.

 

[David Mueller]

At 40Hz I also have no port noises with my front speakers and I get 105dB with them @ 40Hz

Canton ERGO RC-L:b

I hope the PB10 will perform well with those really good speakers!

The sub will be corner loaded and only 3feet away

Tom V. appreciates that I could get 112-118dB at this position

 

[Mike^S]

I wonder how Ed was able to measure 110dB at 20hz. Was it a sweep? Was there port noise?

 

[David Mueller]

Probably with the help of room gain

We'll see...my HT is smaller than ED Mullen's so i should hit the same or even more . . .

No...I can't believe that it was a constant 20Hz tone,that's nearly not believeable...

How many dB do you have @ 20Hz?

Do you hear or only feel 20Hz???

David

 

[Edward J M]

The sweep that tests for dynamic output is short duration (about 1000-1500 ms). The amp will allow this type of signal to pass with limiting.

I know that SVS has tested the PB10-ISD for power compression with a much slower sweep (about 30 seconds 200-10Hz) and the amp still allowed the signal to pass and the sub showed no compression up to about 103 dB, which is consistent with my findings (104 dB across the pass band before the onset of dynamic compression).

On 20 Hz sines, the amp will limit the output, and I could only manage about 94 dB (ground plane) from the PB10-ISD before the amp limiter kicked in.

Anyone will be able to induce port noise at/near the tune point with sines if you push them loud enough. I use sines to measure distortion, and I only run them long enough to stabilize the display and grab a reading and then I allow the sub to cool between runs.

Sines are not found in music and movies, and it is unlikely you will hear port noise under actual normal use (as Mike^S stated above). If you are pushing the PB10-ISD with sines just to see how loud it can play, or to see if you can induce port noise at 20 Hz, this is being abusive and you risk cooking the VC; the subwoofer is not a continuous output device.

You should only be using sines at moderate volumes (like 80-85 dB) to determine the in-room FR. And make sure to use the RS correction factors (the meter is about 7-8 dB low at 20 Hz).

Bottom line: Focus on placement and proper calibration and obtaining the best FR at the listening position. Playback movies and music at any reasonable level, and I seriously doubt you will find the PB10-ISD making audible port noise or lacking in extension or output.

 

[Mike^S]

So when you did your in room dynamic output test, the whole sweep from 200 to 10 hz was only 1.5 seconds? Or did you do individual test tones and each one was 1.5 seconds? My FR looks like this:

nike.cecs.csulb.edu/~msisk/PB10-b.jpg



and I'm trying to make it look more like yours. My room is about 15x20x8 and the sub is in the corner of the room. I'm measuring from 1 meter away because that's where I sit. I used 2 second test tones for each frequency. I don't know why I'm getting peaks at every half octave.

 

[Wayne A. Pflughaupt]

Bejoy,
You said you have the PB10 corner loaded. I assume you have it so that the back of the cabinet is in the corner and the driver faces out?

In my room (which is also large) I found the PB10 sounded noticeably better when I flipped it around so that the driver was firing at the wall. I can’t explain why except perhaps that the output from the port had been obscuring things, and facing it away me reduced the effects of any “chuffing” that might have been happening.

The PB10 is pretty deep – when I turned it around I kept the driver the same distance from the wall as it was before. In other words, the distance between the driver and the wall would be the depth of the sub cabinet.

I found this placement sounded significantly more detailed, and it still has the benefits of corner loading. Give it a try.

Regards,
Wayne A. Pflughaupt

 

[steve nn]

In my room (which is also large) I found the PB10 sounded noticeably better when I flipped it around so that the driver was firing at the wall. I can’t explain why except perhaps that the output from the port had been obscuring things, and facing it away me reduced the effects of any “chuffing” that might have been happening.
__________________________________________________ ____

In my 12 X 24 X 9' the PB10-ISD was loaded normally but in my 12 X 12 X 8'> I found loading was optimal like your described method Wayne. My seating is close to the middle of the room.

Be carful with the Sines Bejoy. My disk must be 15db hot! Adds up to a sub cooker if a guy isn't careful.

 

[Edward J M]

The TrueRTA Quick Sweep is a digitally generated log sine sweep that runs from 10 Hz on up. You can vary the duration of the sweep to some extent by altering the input sampling frequency of the software. In the 8 kHz mode, the entire sweep takes about 1.5 seconds, so it does not spend a lot of time at each frequency. The resolution is set to 1/24 octave.

All testing for FR, dynamic output limits, and THD was done outdoors, at 2 meters, using ground plane methods.

The Quick Sweep is a good measure of the dynamic output of the subwoofer, since it mimics the duration of most music and movie transients. For evaluating power compression, I have adopted a slow reverse sine sweep that runs from 100-20 Hz in about 30 seconds. In my experience thus far, power compression will typically set in a few dB earlier than the dynamic output limit.

 

[Bejoy]

It seems not many has the port noise issues. I'll contact SVS and see if there is anything wrong with my unit.

The only place where I noticed the port noise was on this Chesky DVD and that too for the 20Hz heartbeat. Since this is my first "real" sub, I've never heard anything this low before and didn't know what to expect.

As for placing this backward, don't think I can get away with that. This is sitting in my family room, which is already crowded with Athena AS-F2/C1/B2 and with PB10 joining, my wife has started to complain .

Bejoy