Corner loading and max output....

Discussion in 'Speakers & Subwoofers' started by Craig Chase, Mar 27, 2004.

  1. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    This morning, we put the PB2+ into a corner... set the now calibrated mike at 2 meters from the subwoofer...

    We also put the previously calibrated Rad Shack at two meters... that $39 unit is excellent...

    The results for a single PB2+, with no regard for anything except max output on a pulse, mimicing the Keele review...

    16 Hz - 115.45 Db
    12.5 Hz ... 106.72 Db

    The subwoofer survived... thank goodness for ear protection....

    And WOW does a corner loaded sub add SPL's...

    And the Rad shack showed 116 and 107 Db... pretty good !

    pics of the sub are on the SPOT

    ...EDIT...If someone wants to compare it to what Keele measured... I think he used a single 1220... though I am not positive...

    and THAT is a test I won't be doing again... bypassing the protection on a sub you paid for is a scary thing...
     
  2. Rick Cohen

    Rick Cohen Agent

    Joined:
    Mar 7, 2004
    Messages:
    28
    Likes Received:
    0
    Trophy Points:
    0
    MY PB 2+ is in a corner and is working well except that I have a pretty distinct hump in the 30hz to 40hz range. I have used the phase to try and push the hump down. I can not move the sub do to the size this is where it must stay. Any ideas? Is this hump out of the ordinary? RICK
    FREQRAW SPLSPL (comp)
    137889.5
    1580.588.5
    178895.5
    208086.5
    227984.0
    257882.0
    287881.0
    318890.5
    359294.5
    399294.0
    448586.5
    507980.5
    567879.5
    598485.5
    668283.5
    707879.5
    758081.5
    798081.5
    848081.5
    897880.0
    947880.0
    1008082.0
     
  3. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Rick - Soon there will be several answers to your problem.... as it is just one rather broad peak, the Speaker City Subwoofer Optimizer System comes to mind... I have one, and it is really easy to use... and it will fix your problem, and is totally automated ... speakercity.com

    Also... You can look at Rane or Behringer for other, more elaborate/more hobbyist approaches
     
  4. Rick Cohen

    Rick Cohen Agent

    Joined:
    Mar 7, 2004
    Messages:
    28
    Likes Received:
    0
    Trophy Points:
    0
    Craig,

    Thanks for the quick response. How flat should the curve be??

    Do you have any experience with ART 351 equalizer SVS has on their site. I would actually prefer the manual intervention. (control freak)

    It looks like it goes in line between the receiver subwoofer out and the subwoofer amp?

    RICK
     
  5. Sebastian

    Sebastian Second Unit

    Joined:
    Apr 14, 2002
    Messages:
    361
    Likes Received:
    0
    Trophy Points:
    0
    Rick,
    I had that same hump at my old house. It made Jurrasic park sound awesome. Anyway may want to look into that BFD if it really bothers you.
     
  6. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Rick...The ART unit will work fine... Sebastion has a good point though... how does it sound now ? Are you hearing a bothersome bass "boom" ? Some guys actually eq their system like yours because they like it...

    That being said... the ART is inexpensive.... go for it
     
  7. Sebastian

    Sebastian Second Unit

    Joined:
    Apr 14, 2002
    Messages:
    361
    Likes Received:
    0
    Trophy Points:
    0
    Oh Wow, that Art351 looks real good! I recommend that over the BFD. I will have to run a freq sweep in the new house and see if I may need one[​IMG]
     
  8. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Sebastion... Do you mean need a new ART ? or a new House ?...[​IMG]
     
  9. Rick Cohen

    Rick Cohen Agent

    Joined:
    Mar 7, 2004
    Messages:
    28
    Likes Received:
    0
    Trophy Points:
    0
    Thanks for the input. I don't mind it on movies so possibly I should just leave it since that is about 80% of the use. It does sound very good on action flicks. I am not using much of the subs power however. My room is 16 by 38 and the sub has no problem.

    Where I find it a bit of a problem is with some music. I was listening to some big band music (change of pace and kind of nice) and the boom on the bass and trombones was a bit much. I also had the Dave Mathews DVD from a Central Park concert on and that was real nice. I want the deep base without the boom on the big band stuff.

    I was thinking about trying the crossover on the sub and pushing the sub down to 50hz as an alternative for some music with the mains set to large. They will go down in the 35-40hz. I will try a few more sweeps. RICK
     
  10. Sebastian

    Sebastian Second Unit

    Joined:
    Apr 14, 2002
    Messages:
    361
    Likes Received:
    0
    Trophy Points:
    0
    Craig,
    I mean I just moved into my new house and need run freq sweep to see if I need an EQ
     
  11. Edward J M

    Edward J M Cinematographer

    Joined:
    Sep 22, 2002
    Messages:
    2,031
    Likes Received:
    0
    Trophy Points:
    0
    Craig.....the RS meter is notoriously inaccurate at both high SPL and at super low frequencies.

    Without going into great detail, it will read progressively lower than the actual SPL as you go deeper in frequency.

    The meter also has some inherent inaccuracies that cause it to read even lower than the C-weighted curve would suggest. Provided below is a table with the frequency, the theoretical correction factors for the C-Weighted curve, and the commonly used RS Correction Factors. As you can see, there is a difference between the two and it grows larger as the frequency drops.

    Whether each RS meter will display the exact same offsets is up for discussion, but my hunch would be no. If you really want to know what the meter is reading at any particular frequency, you'll need to get it professionally calibrated.

    Bottom line - your reading at 12 Hz is probably about 118-122 dB in reality. The RS meter cannot be used to compare against Keele's data; he uses an unweighted and calibrated mic that is flat to at least 10 Hz.

    Regards,

    Ed

    Frequency / C-Weighted CF's / Common RS CF's
    10.0 / 14.3 / 20
    12.5 / 11.3 / 16.5
    16.0 / 8.4 / 11.5
    20.0 / 6.2 / 7.5
    25.0 / 4.4 / 5.0
    31.5 / 3.0 / 3
    40.0 / 2.0 / 2.5
    50.0 / 1.3 / 1.5
    63.0 / 0.8 / 1.5
    80.0 / 0.5 / 1.5
    100.0 / 0.3 / 2
     
  12. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Ed - The Rad Shack has a port for calibrating it... and it was done by T (the engineer that works with my brother... he likes anonymity)... The results I posted were for the ECM8000/TrueRTA setup (sorry if that was not clear... my head may have been ringing still, even with the hearing protection) ... I just thought it was really cool how close he got the Rad Shack to being accurate...

    We only hit each frequency four times, as I did not want to lose a driver... and the PB2+ seemed to have hit its max output at (the 106.72 and 115.45 Db levels)...That was the third "pulse" (1 second)... the fourth we added 2 db of gain, and got the same result... and that was enough !

    He (T) also cautioned me that regardless how well calibrated any system is, room gain, differences in the microphones.. etc... will have an effect. So (I agree) Keele's setup was different even though We used two meters from the sub, and corner loaded the subwoofer. He still used a different room and test gear... but Artie had mentioned this several times (a comparison at 12.5 Hz), and this was the best I could do in an SVS that was fairly close to the price of the 1220. Hopefully this will answer his questions...

    You and I are now using comparable setups... but even they will not be identical. (even the ECM8000's will be a bit different) I ordered the TrueRTA because you already had it, and someone could look at either of our data and get a pretty good idea between several different subwoofers...

    By the way... You are quite correct on the over 30 HZ stuff... once a subwoofer shows it can handle the 20 Hz stuff... 40 is pretty easy...[​IMG]

    Oh... For our $600 shootout, we are adding the Aperion S-12... the VTF-3 (in max output... pretty much what you tested in the STF-3) ... and a Rocket UFW-10...
     
  13. Edward J M

    Edward J M Cinematographer

    Joined:
    Sep 22, 2002
    Messages:
    2,031
    Likes Received:
    0
    Trophy Points:
    0
    Didn't know you were using the EM8K......who calibrated it?

    But while we're on the subject of the RS meter:


    Yes, the two rigs will definitely differ somewhat in response - there are many variables. Despite using similar rigs, we both know there are myriad reasons which prevent even gross extrapolation of data (especially THD limited output) between two reviews/rooms/rigs. You can see in your own home how moving between rooms and even moving the sub or the mic within a room, drastically alters the FR and THD limited output.

    We both know it would be pointless (for example), to directly compare Nousaine's THD data on the VTF-2 to your data on the VTF-3 or my data on the STF-3; WAY too many variables - unless of course, you happen to be the KING of bogus extrapolation (who shall remain nameless). [​IMG]

    Have a GREAT time with your shoot-outs, I always have fun checking your threads. [​IMG]
     
  14. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Ed...My bud T handles all this for me... He is a riot.. drop things off... he tears then apart... calibrates... calls when done...and he won't charge me. Maybe the fact I fronted money to help with their factory helps... He stays out of the fray because of their pro-audio clients. We consumer audio types are consider the lunatic fringe by these guys ( can't imagine why...[​IMG])

    He took my laptop, microphone, Mobile pre... and did everything yesterday...

    He had me drop off The Rad Shack in January... his words when I picked it up "It works now"...and it sure does.

    To give you an idea... one subwoofer he designed uses dual 18's, and are Theile/Small port design... and will hit 135 DB at 32 Hz...OUTSIDE...
     
  15. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    If someone would point Artie in this direction, I would appreciate it. Maybe I should have put in the thread title that this was specifically about the 12.5 Hz max he had asked about. Oops... I just did not want to start anything...[​IMG]

    Artie... any questions ?
     
  16. Mark Seaton

    Mark Seaton Supporting Actor

    Joined:
    Oct 10, 1999
    Messages:
    599
    Likes Received:
    0
    Trophy Points:
    110
    Real Name:
    Mark Seaton
    Craig,

    With all this measurement effort, do you have an EQ in the system?

    Another thing to examine in the different placements is the response across different locations, most importantly at the listening position.

    So far as high levels, yesterday I swept 4 B-DEAPS in a small live performance venue and measured 45V across EACH sub. That's 1kW into each pair... Apparently there was a graduation held recently. Sweeping all 4, I was able to clean off the remainder of the confeti from the beams above! Fun stuff, very viceral.

    Cheers,
     
  17. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Mark - Currently I am not using any eq on the subwoofers... just placement and calibration...

    I am never introducing you to my brother... you guys would be dangerous. His company just installed a very large auditorium with a line array and subwoofer setups... to the tune of $40,000 in speakers alone...

    I posted on AV123 that they have one subwoofer that does 135 db at one meter at 32 Hz... outside... that sounds like your kind of stuff...

    Love the confetti clearing... [​IMG]
     
  18. Mark Seaton

    Mark Seaton Supporting Actor

    Joined:
    Oct 10, 1999
    Messages:
    599
    Likes Received:
    0
    Trophy Points:
    110
    Real Name:
    Mark Seaton
    There is a good chance he will or has come across our ServoDrive or Sound Physics Labs products at one time or another.

    This afternoon I plan to sweep all 4 subs in this room at full rated power of 1600W. [​IMG]
     
  19. Craig Chase

    Craig Chase Gear Guru
    Supporter

    Joined:
    Oct 21, 2002
    Messages:
    1,658
    Likes Received:
    66
    Trophy Points:
    1,610
    Location:
    Pennsylvania
    Real Name:
    Craig
    Mark... I will ask him about your company....

    Artie... Where are you ? I risked life, limb, and my house's structural integrity to get this done for you....[​IMG]
     
  20. Stephen_F

    Stephen_F Extra

    Joined:
    Feb 5, 2004
    Messages:
    15
    Likes Received:
    0
    Trophy Points:
    0
    Artie has lost interest and has moved on [​IMG]
     

Share This Page