STF-2 & PB12-isd, 2 locations, 2 FR Analysis

Discussion in 'Speakers & Subwoofers' started by JasonCI, Jan 10, 2005.

  1. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0
    Hello all,

    I'm in the process of shopping for a subwoofer for HT use. I was first turned onto, and purchased, a SVS PB12-isd. It's a huge upgrade over my old DefTech 10" sub and I am impressed with its performance. However, I just couldn't get over how freakin' big it is! Since I was also considering an HSU sub I decided to try an STF-2 as well to see if I could get a good sounding sub in a smaller package.

    Both subwoofers have a high grin factor, but I slightly favor the sound of one over the other. I took SPL readings for each, at two separate locations, to determine whether one performs better based strictly on FR. I'm just not sure what the graphs are telling me.

    These tests were performed with Phase at 0 and main speakers disabled. Crossover was set to 120 Hz within my processor. Master volume was increased until 16 Hz tone read 80 dB on my Radio Shack Analog SPL Meter. The meter was placed on a tripod at ear level in the main listening position. Test tones were 1/6 octave sine waves copied from Snapbug's BFD site.

    The following diagram shows location option 1. Each sub (one at a time) was positioned so its cabinet was 6" from the west wall and 6" from the south wall. The corresponding FR in the 4 graphs below is shown in PURPLE.

    [​IMG]

    The diagram below shows location option 2. Each sub (one at a time) was positioned so its cabinet was 6" from the west wall and 5 feet from the south wall. The arrow shows the direction the port was facing. The corresponding FR in each of the 4 graphs below is shown in BLUE.

    [​IMG]

    The following is the FR Chart for the PB12 in each location. The values are based on raw SPL readings. The FR of the PB12 in Location 1 is drawn in purple. The FR of the PB12 in Location 2 is drawn in blue.

    [​IMG]

    This is the FR Chart for the STF-2 in each location. The values are based on raw SPL readings. The FR of the STF-2 in Location 1 is drawn in purple. The FR of the STF-2 in Location 2 is drawn in blue.

    [​IMG]

    The following chart again shows the PB12's FR at each location. However, the values were adjusted for RS SPLM low frequency innacurracy. The SPL-compensated FR of the PB12 in Location 1 is drawn in purple. The SPL-compensated FR of the PB12 in Location 2 is drawn in blue.

    [​IMG]

    Finally, the chart below shows the STF-2's FR at each location. However, the values were adjusted for RS SPLM low frequency inacurracy. The SPL-compensated FR of the STF-2 in Location 1 is drawn in purple. The SPL-compensated FR of the STF-2 in Location 2 is drawn in blue.

    [​IMG]

    Note - FR data is available here:

    https://home.comcast.net/~jcioffi6/pics/frdata.xls

    QUESTIONS -
    1. Based strictly on FR at both locations, is either sub a better performer?
    2. Based on FR, does either LOCATION pose an advantage?
    3. Are there any other locations/orientations that I should be trying? Please note that I share the East wall with my neighbors and would prefer not to crumble it. [/list=1]

      Thanks all!
     
  2. Max F

    Max F Second Unit

    Joined:
    Jun 26, 2004
    Messages:
    250
    Likes Received:
    0
    Trophy Points:
    0
    If you have to use that crossover (120 hz) on the receiver then i would have to go with the STF-2 in location 2. Just need the BFD to fine tune. Overall though, it looks pretty good to me. [​IMG]

    Actually, i didn't think the STF-2 could give that much below 25 hz.
     
  3. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0


    Thanks Max,

    I don't have to go with 120 Hz crossover. My receiver is capable of 60, 80, 100, or 120. I changed it to 120 Hz for testing purposes, otherwise the SPL takes a nose dive after its typical setting of 80 Hz.
     
  4. Wayne A. Pflughaupt

    Joined:
    Aug 5, 1999
    Messages:
    6,123
    Likes Received:
    40
    Trophy Points:
    6,610
    Location:
    Katy, TX
    Real Name:
    Wayne
    Well, something is really fishy here. The differences between corrected and uncorrected should be greatest below 40Hz, and all four charts reflect this.

    The problem is between the two STF-2 charts, especially the second one. Sorry, but there is no way a corrected curve will result in a 10 dB increase in SPL virtually across the board, as the purple line shows in the second chart.

    As far as a winner, it’s pretty much a draw, based on the charts. Same with location – probably because the two locations are so close together. I expect that both subs corner-placed and equalized would be excellent performers.

    If musical qualities are important to you, I suggest trying both with the selections from recording artist Basia I used in my recent $400 Sub Face-Off.

    Regards,
    Wayne A. Pflughaupt
     
  5. Adil M

    Adil M Supporting Actor

    Joined:
    Nov 21, 2001
    Messages:
    922
    Likes Received:
    0
    Trophy Points:
    0
    The STF2 has higher output and linearity. The only other important measurement we are missing is a distortion amount at different frequencies.
    Wayne's observation needs to be addressed. It's not right.
     
  6. Ilkka R

    Ilkka R Second Unit

    Joined:
    May 19, 2004
    Messages:
    270
    Likes Received:
    0
    Trophy Points:
    0
    Here are the correct graphs. Jason, say thank you.

    [​IMG]
    [​IMG]
     
  7. Max F

    Max F Second Unit

    Joined:
    Jun 26, 2004
    Messages:
    250
    Likes Received:
    0
    Trophy Points:
    0
    I still like the STF-2 here and it's cheaper.[​IMG] Although i really thought that the STF-2 would have a sharp dropoff below 25hz - must be some serious room gain.

    If you get a BFD you can bring those peaks down at 56 and 90 hz. And possibly bring up the 40 hz if its not too much of a void (or just move the spl meter 1 foot in either direction [​IMG]).
     
  8. CurtisSC

    CurtisSC Screenwriter

    Joined:
    Jan 28, 2003
    Messages:
    1,412
    Likes Received:
    0
    Trophy Points:
    0

    Why would the STF-2 experience the room gain and not the PB12....especially if the PB12 is suppose to have better extension?
     
  9. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0
    Ilkka - Thank you Jason.[​IMG]

    No really, Thanks.

    I accidentally applied an 11.5 dB correction to all values in one column of STF-2 SPL data. I fixed my formulas, took a screenshot of the revised graph and overwrote the file.

    However, I was hesistant to plot both the PB12 and the STF-2 on the same chart because I used an 80 dB at 16 Hz benchmark for both subs. Since the STF-2 doesn't play as loud as the PB12 at 16 Hz I assume the STF-2's SPL at higher frequencies is inflated.
     
  10. CurtisSC

    CurtisSC Screenwriter

    Joined:
    Jan 28, 2003
    Messages:
    1,412
    Likes Received:
    0
    Trophy Points:
    0


    Try picking a higher frequency to level match....or pink noise from Avia...and see what you get.
     
  11. Ilkka R

    Ilkka R Second Unit

    Joined:
    May 19, 2004
    Messages:
    270
    Likes Received:
    0
    Trophy Points:
    0
    Jason, I updated those graphs, just refresh and you should see them. I believe now they represent more of their true performance.
     
  12. kevin tate

    kevin tate Stunt Coordinator

    Joined:
    Jul 2, 2003
    Messages:
    182
    Likes Received:
    0
    Trophy Points:
    0
    The graphs indicated PB10. Shouldn't it be PB12?
     
  13. Ilkka R

    Ilkka R Second Unit

    Joined:
    May 19, 2004
    Messages:
    270
    Likes Received:
    0
    Trophy Points:
    0
    Oops, my bad. Now they are corrected. [​IMG]
     
  14. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0
    So is it still a toss-up?
     
  15. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0
    Ilkka,

    My guess is that you offset all of the STF-2 data points by the difference of the PB12's SPL at one frequency and the STF-2's SPL at the same frequency. Correct?
     
  16. Ilkka R

    Ilkka R Second Unit

    Joined:
    May 19, 2004
    Messages:
    270
    Likes Received:
    0
    Trophy Points:
    0
    I just dropped STF-2 values by 5dB, so that 50-60Hz is about at the same level with both subs, so yes correct.
     
  17. JasonCI

    JasonCI Stunt Coordinator

    Joined:
    Dec 29, 2004
    Messages:
    59
    Likes Received:
    0
    Trophy Points:
    0
    Thanks. So is there anything compelling in the graphs? Will one sub or location be more EQ friendly?

    It appears as though the PB12 is more balanced at both locations. The STF-2 appears to benefit from the corner reinforcement in location 1. No lightbulbs are going off otherwise.

    By the way. Can room vibrations effect the SPL reading?
     
  18. Ilkka R

    Ilkka R Second Unit

    Joined:
    May 19, 2004
    Messages:
    270
    Likes Received:
    0
    Trophy Points:
    0
    I would propably choose PB12 and location 2. You should also measure with your mains on. That 50-160Hz range will change a lot then. Use ~80Hz xo.

    Yes, room vibrations can effect, thats why ~80-85dB is good level to measure. No more than that.
     
  19. Adil M

    Adil M Supporting Actor

    Joined:
    Nov 21, 2001
    Messages:
    922
    Likes Received:
    0
    Trophy Points:
    0
    If price was not a factor I would assume that the SVS is higher output w/ less distortion in the bottom end.
    However, it appears to be 400 HSU vs. 600 SVS.
     

Share This Page