PB2+ owners: What is maximum peak SPL your sub has pumped out?

Discussion in 'Speakers' started by Khai, Jan 31, 2004.

  1. Khai

    Khai Extra

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    Hi,

    I'm from the UK and I've had my sub for over a week now and even though I'm still fine-tuning my sub to try and gain every last ounce of performance from it, I am truly amazed by this sub's performance - and this is coming from someone who has owned the mighty THX-Ultra II certified Velodyne HGS-18.

    The sub resides in my 12 x 15 x 9 feet living-room and although some may see this as overkill, I think that it is better to have a sub that can over-perform in ones room than one that under-performs. I have my sub calibrated using Avia so that it reads exactly 85dB on my SPL meter and although I have experimented with tuning the sub at different frequencies using every possible combination on subsonic movies like Titan AE, LOTR, SW: TPM/AOTC, I find that leaving the sub at 25hz with all three ports open yields the best results.

    Regarding the subject matter, I tried out my new subsonic dvd tittled 'Solar Max' DTS by Imax and there is a chapter on there called (surprise, surprise) 'Solarmax' and I was not anticipating the sheer brute force of the subsonic bass that was soon to follow. It literally shook the house in a way I thought was not possible other than if there was an earthquake. Needless to say I had my Radioshack SPL meter handy and got a peak reading of 122dB (un-corrected) at -05dB. [​IMG] [​IMG] [​IMG]

    I was then brave enough (or stupid lol) to replay the same chapter but this time sticking my head right up close to the sub so that I got a clear view of the driver-cones to see just how much the driver was moving by. I could not get a precise measurement but it seemed as though the cone was moving no more than 15mm. I had a feeling that I might be able to get away with playing the same chapter at reference level without bottoming the driver but quite frankly I was far too frightened of what the outcome might be or the complaints I might get from my neighbors.

    What is the maximum peak SPL your sub has managed to pump out and do you have an idea of how much the driver/s from your sub was moving by?

    Btw this is slightly off topic but I have read PB2+ owners stating that on 'The Matrix' when Mopheus is fighting Neo and does his infamous flying knee-drop and lands into the ground, some people are getting around 115dB? Well I have played that scene with the HGS-18 and the PB2+ (tuned to 25hz/20hz/16hz)at reference level and I can't even get close to hitting 105dB let alone 115dB!

    Am I the only PB2+ owner not able to reach 115dB from that knew-drop lol? [​IMG]
     
  2. steve nn

    steve nn Cinematographer

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    The next time the house clears out I'll see what I can hit on the knee-drop at -5 or reference for you Khai.

    I run three 25-31CS+ in a 2880 cf HT which equates to 12 X 24 X 10 with one very leaky wall. 124 db uncorrected is the highest I have ever hit and I wont be going back there again. I can gain 2db by placing a 1/4 sheet of plywood ocross a entrance that is right next to my subs but is not warranted and looks ridiculous.

    I definitely agree on headroom. Never need to worry about bottoming out and never feel like your abusing your subs allonge with enhancing the sound/performance.

    Triple Threat
     
  3. Edward J M

    Edward J M Cinematographer

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    It depends on where I am in the room. At my normal listening spot 11 feet from the sub, I've hit about 120 dB (corrected) during testing, but that is far too loud for normal playback.

    If I go to the diagonal rear corner about 16 feet from the sub, I've hit about 125 dB (corrected) simply due to the room acoustics.

    I 100% agree the stock 25 Hz tune is the best/safest for maximum playback levels and testing.

    I wouldn't characterize any of those DVDs as "subsonic" as the majority of the bass in them is in the 22-35 Hz region. If it were truly subsonic (below 20 Hz), you wouldn't hear or feel much from the PB2+ in the 25 Hz tune as it ramps down the response pretty sharply below about 22 Hz. To get truly subsonic response, you need to plug a port and lower the tune switch to the 20 Hz setting.

    I would say your inability to hit a high level on the Morpheus "knee drop" is probably more of a room acoustics issue than anything else. Move the mic around and try it in a few different places - you might be surprised at the differences you observe.

    Finally, the resonators (vents) in the PB2+ couple with the woofers down around the tune point and reduce woofer excursion considerably by design. So at 23-28 Hz (where most of those big bass hits are occuring), you won't see "extreme" excursion levels from the woofers in the 25 Hz tune. The maximum woofer excursion actually occurs somewhere around 35 Hz in the stock 25 Hz tune.

    The following is general advice, and not directed at you in particular:

    If you ignore SVS' advice and leave all three ports open and drop the tune switch to the 20 Hz or worse yet the 16 Hz setting, and playback DVDs at maximum levels, you are flirting with disaster.

    Lowering the tune switch not only lowers the point where the subsonic filter kicks in, it also boosts the response in the 15-20 Hz region. With all ports open, below about 22 Hz the woofers "decouple" from the vents and the enclosure lacks the restoring force to control woofer excursion.

    The triple threat (no offense, Steve!) combination of a lower subsonic filter point, a boosted response, and a lack of enclosure restoring force can conspire to bottom out and damage both woofers before you can say "whoops" and reach for the remote.

    The mismatched (non-conventional) port and tune switch combinations (2/16, 3/16, 3/20) are for moderate playback levels. It's fun to experiment, but common sense is the order of the day when running mismatched tune configurations.

    Regards,

    Ed
     
  4. Rogelio D

    Rogelio D Agent

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    I can't wait till my SVS get here this week after reading some of the posts above. The max my current subs are putting out is around 100db at the listening position.

    Just hope all the snow doesn't slow down the truck!!!
     
  5. Richard_M

    Richard_M Second Unit

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    Hi Khai

    Congratulations on your new toy.

    Are you using a R1 or R2 release of The Matrix, sometimes soundtracks can be recorded at different levels, I have struck this with some R4 releases compared to R1, but I am not sure about The Matrix though.
     
  6. Khai

    Khai Extra

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    Hi Richard_M,

    Thanks, I'm very much enjoying my new toy.[​IMG]

    Regarding the region version of the Matrix, I actually have the R4 version because of the 'alledged' superior picture it has over the other versions so this might be the reason why I'm unable to achieve a 115dB on Morpheus's knew drop. Or it could just be my room accoustics as Edward J M has stated. I believe my friend has the R1 version of The Matrix so I'll borrow it off him and give it a try.
     
  7. Khai

    Khai Extra

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    Bob Cranwell,

    128dB must have quite literally knocked you off your seat lol. [​IMG]

    Did the PB2+ show any major signs of strain reaching that SPL and do you think you could have pushed it further - I assume that the PB2+ was tuned to 25hz with all three ports open?
     
  8. Khai

    Khai Extra

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    Hi Edward J M,

    Can you name me a few passages from dvd's which contain subsonic frequencies so that I can test out the lower tuning frequencies of the PB2+?

    PS. Sorry, I forgot to mention that The Haunting DTS 'Coming Mother' chapter was included amoung the dvd tittles tested when experimenting with tuning the PB2+ at different frequencies.
     
  9. Khai

    Khai Extra

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    Does anyone know what the region of frequencies contained in the chapter 'Solar Max' are or can they find out?

    Is there someone out there brave enough to play that chapter at reference level lol? [​IMG]
     
  10. Khai

    Khai Extra

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    Bob Cranwell,

    Due to the fact that you weren't in the same room as the PB2+ when you measured 128dB, wasn't there a strong prospect that the two driver's could have bottomed-out and that was also measured by the laptop hence creating a massive 128dB?
     
  11. Edward J M

    Edward J M Cinematographer

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    One that springs to mind is the barfight scene in Daredevil (dts).

    During that scene, there are bunch of short duration, fairly high amplitude spikes centered around 15-16 Hz.

    The 20 Hz tune on the PB2+ should capture those subsonics peaks better than the 25 Hz tune.

    Go here for a look (thanks RudiB):

    http://bass.jawmail.org/index.php?p=daredevil&c=2

    Regards,

    Ed
     
  12. Khai

    Khai Extra

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    Bob Cranwell,

    It is quite amazing you were able to achieve 128dB with the PB-2+ set-up with 3 ports open and the subsonic filter at 20hz AND without bottoming the driver.[​IMG]

    Does anyone have an idea how much more the driver's from the PB2+ is moving by, at this unconventional tuning method versus the conventional 2 ports open with the SS set to 20hz?
     
  13. Khai

    Khai Extra

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    Also, can someone post the Radioshack SPL meter correction values for the following frequecies please?

    16hz
    18hz
    20hz
    22hz
    25hz
    31.5hz
    36hz
    40hz
    45hz
    50hz
    55hz
    63hz
    71hz
    80hz
    89hz
    100hz
    111hz
    125hz

    Thanks
     
  14. Edward J M

    Edward J M Cinematographer

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    This is an educated guess based on modeling, but at maximum playback volumes, woofer excursion at 20 Hz in the mismatched 3/20 tune is probably about 10-15 mm more than it would be in the conventional 2/20 tune.

    Tom V could give you a more precise number, but suffice it to say, allowing a ported sub to play 1/3 of an octave below its tune point while at the same time boosting the response in that region will definitely result in much greater woofer excursion, possibly exceeding the suspension travel limits.

    If the sub reaches a point where it starts to sound compressed and won't play any louder despite increases in the Master Volume, that is a huge warning sign you are starting to exceed the linear excursion limits of the drivers.

    Go here for the standard RS correction factors:

    http://members.tripod.com/~terrycthe...um/page11.html

    http://www.hometheaterhifi.com/utili...load-page.html

    Regards,

    Ed
     

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