SVS 20-39PC+ In Room Frequency Response

Discussion in 'Archived Threads 2001-2004' started by Edward J M, Dec 22, 2002.

  1. Edward J M

    Edward J M Cinematographer

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    Hello Everyone:

    I figured it was time to verify the in room frequency response of my SVS 20-39PC+.

    I burned a CD using a 1/12 octave frequency generator downloaded off the Shiva Sonotube webpage. Each tone is 10 seconds long, and the sweep ran from 10 Hz to 71 Hz.

    I am using a factory certified professional-grade Bruel & Kjaer Model 2205 SPL meter which I just calibrated. This SPL meter is accurate down into the subsonic range, and does not need a "Rat Shack" type correction factor for bass tones. Meter settings are C-Weighted, Slow.

    I mounted the B&K on a tripod at the listening position, about 11 feet from the sub, pointed toward the front of the room, and tilted about 40 degrees up toward the ceiling.

    I set the master volume on my receiver to give me about an 80 dB average volume. I am not using any type of equalizer or feedback destroyer. This is the real deal in my HT room at the couch.

    For the purposes of the test, I set the SS filter to 12 Hz, just to see how low this thing can really go.

    I ran Test #1 with all three vent ports open, and Test #2 with two vent ports open and one vent port plugged with the factory supplied foam port plug.

    I plotted all of this in an Excel spreadsheet which looks really neat, but I can't attach it here, so here are the test numbers. The first column is the frequency, the second column is Test 1, and the third column is Test 2.

    Test 1 All Ports Open:

    As can be seen from Test 1, the sub holds a nice flat +/- 4 dB from 70 Hz down to about 30 Hz, and then begins a gentle rise, cresting at +10 dB at 24 Hz, and then dropping back down to -3 dB at around 16 Hz. It hangs in there suprisingly well checking in at -5 dB at a staggering 11 Hz.

    Test 2 Two Ports Open, One Port Plugged:

    As can be seen from Test 2, the sub holds +/- 4 dB from 70 Hz down to 11 Hz. Read it again folks - an essentially flat line from 70 Hz to 11 Hz with no major peaks or dips - in my HT room, without EQ, or a feedback destroyer.

    My Preference and Summary:

    Although the in room response is obviously more accurate with one port plugged, I actually prefer HT playback with all three ports open. The flat response from 70 Hz down to 30 Hz gives me accuracy with no boom, and the gentle rise and peak at 24 Hz provides reinforcement right where most LFE effects are at their most impressive.

    Nonetheless, the accuracy and flatness provided by plugging one port is quite simply amazing for ANY sub at ANY price. But for an $800 asking price - this in room frequency response is almost beyond belief!

    Regards,

    Ed Mullen

    Freq.Test 1 SPLTest 2 SPL

    10 65 68
    10.6 69 73
    11.2 75 81
    11.9 76 82
    12.6 74 81
    13.3 75 80
    14.1 75 81
    15 75 82
    15.8 76 83
    16.8 78 84
    17.8 80 84
    18.8 84 83
    20 87 83
    21.1 88 81
    22.4 88 80
    23.7 90 82
    25.1 88 82
    26.6 86 81
    28.2 82 79
    29.9 80 77
    31.6 81 77
    33.5 80 75
    35.5 79 76
    37.6 78 76
    39.8 77 76
    42.2 77 76
    44.7 78 77
    47.3 79 78
    50.1 80 79
    53.1 80 79
    56.2 82 82
    59.6 84 84
    63.1 84 84
    66.8 84 84
    70.8 80 80
     
  2. Andrew CM

    Andrew CM Extra

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    Thanks for sharing the info Edward. Awesome FR in your setup - I envy you.
    Could u provide a link to the Sonotube site - was it easy to copy it to your disc.

    Thanks.
     
  3. Edward J M

    Edward J M Cinematographer

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    The Sono Tube site is currently down - I'll link it when it's up again. The download was easy - 41 zipped MP3 files. It actually goes up to 100 Hz, but I cut my test at 70 Hz. Unzip them and burn the CD and it plays fine in the DVD player.

    It would only be a slight exaggeration to state that the FR from 70 Hz to 11 Hz for Test 2 could have been drawn with a ruler - it's THAT flat!

    Ed
     
  4. Edward J M

    Edward J M Cinematographer

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  5. Ryan DC

    Ryan DC Agent

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    Very impressive review! I am considering this sub or possibly the PCi version (anyone have a fr. response of this sub like ed's review?) What size room was the pc+ tested in? My room size is 15x13x8 ft. with sloped ceilings on both sides (1300cu.ft.) and was wondering if the PC+ would be overkill? Thanks and happy holidays!
     
  6. Andrew CM

    Andrew CM Extra

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    Edward

    You got mail
     
  7. Edward J M

    Edward J M Cinematographer

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    Ryan DC:

    My HT room is 12x18x8 - about 1,700 ft3. The sub is located near the front left corner.

    Above 30 Hz, the PC+ betters the PCi by about 3 dB in max output, on average. Below 30 Hz, the PC+ outguns the PCi by about 5-6 dB in max output. Up to their respective limits, they will sound about the same, though.

    How loud do you like HT playback? If you really push it hard (in your size room that would be 115 dB+ bass peaks), I think the PC+ would not be overkill at all, and gives you a little "insurance" over the PCi on those killer LFE passages so common in today's DVDs.

    If you like it more sedate (107-110 dB bass peaks), I think a PCi would do just fine. My buddy has a 25-31PCi and it's no slouch - very powerful and great sounding in his 1,500 ft3 HT room. It has fluttered my pants legs before sitting near it!

    If you suffer from buyer's remorse, the PC+ is one hella deal for the price difference. You get the better TC Sounds dB-12 driver, the 525 W amp with 4 position SS filter and infinitely variable phase, and the better endcaps and triple vent with tuning capability.

    For me personally, I was not cash-strapped at the time, and it was a no-brainer to get the PC+.

    Ed
     
  8. Marcus Lewis

    Marcus Lewis Stunt Coordinator

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    This might be a silly question, but if you set the SS filter at 12hz how were you able to get readings below that point?? 10 hz, etc ...
     
  9. Edward J M

    Edward J M Cinematographer

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    The SS filter is not a "brick wall", it has a certain dB/octave sloping cut-off. I'm not sure what the actual number is, but I'd bet it's pretty steep - maybe 24 dB/octave.

    Nevertheless, it will still allow some frequencies to pass through below the set point, but it's pretty agressive. As you can see, it dropped 14 dB between 11.9 Hz (82 dB), and 10 Hz (68 dB) - this was clearly a function of the SS filter.

    Ed
     
  10. Ryan DC

    Ryan DC Agent

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    Edward,

    Thanks for responding!

    Did you happen to have a PCi version before to get those stats? I like to listen to most stuff loud, mainly music so I can feel the bass. What I currently have is a pair of 3-way 15"s made by KLH which is their performance series from a few yrs back. They get plenty loud and on my rat shack meter I have hit 108 db w/o correction factor and around -40 to 35 on my receiver volume setting. So it looks like it would be a better choice to go with the Pc+ version although I do have some limits on cash. Now I'm contemplating on whether to get the 25-31+ or the 20-39+?
     
  11. Edward J M

    Edward J M Cinematographer

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    I got the PCi vs. PC+ max output stats from Tom V and Ron S on other posts they have made. Always double check with SVS before making a final purchase determination - they know their products best, obviously.

    If you want to really pound with mainly pop/rock/techno music, then the 25-31 PC+ is the WTG. I don't think a lot of this music dips much below 25-30 Hz; a perfect fit for the 25 series.

    For HT, the 20-39PC+ is a better choice IMHO, since many new DVDs have significant LFE content into the upper teens; a perfect fit for the 20 series.

    Also be aware the 25 series plays the loudest (above it's tuning point) of the three sizes, in exchange for sacrificing a bit of deep extension. I think the difference in max output between each enclosure size is about 1.5 dB.

    So if a 25 series PC+ can hit 116 dB max on a 30 Hz LFE explosion, a 20 series PC+ might manage 114.5 dB on the same passage, and a 16 series might manage 113 dB on the same passage. That is why SVS often recommends dual 16 series if you have a large room - they're down a good 3 dB in max output compared to the 25 series at anything above 25 Hz.

    Of course, get down into the upper teens, and the 16 series really comes into its own - and runs away easily in max output over the 25 series on the really deep stuff.

    Ed
     

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