PSW505 vs. PSW505 x2

PolkThug
PolkThug Posts: 7,532
edited March 2004 in Subwoofer Hookup & Bass Management
My favorite movie for demonstrating the impact that a sub has on a HTS is Final Destination 2. The highway crash scene is the best I have ever seen in any movie. Anyway, the purpose of this thread is to show the difference between having one vs. two 505's.

Here are my Settings:
Onkyo 700 volume at 60.
Bass level on receiver set to 0.
Crossover set to 100hz.
Subwoofer volume knob set to 12 o'clock position.
Input to LFE (unfiltered), with Monster sub cables.

RadioShack digital meter, max, C weight. All meter readings are "as is" straight off the meter, not adjusted.

I picked 3 scenes from the highway wreck, not necessarily the 'best', but easy to reference.

One sub Two subs
Log falls off logging truck: 94db 101db
Semi hits Mustang: 92db 100db
Firebird hits gas tank: 94-99db 102-104db

So, in my scenario adding an additional sub added an average of +8db. Some of the car flips hit some really hard bass like the Mustang rolling, or the red SUV flipping with the blonde chick's head out the sunroof. ;) I would have got some more readings but the "Bass Police" came home.

Regards,
PolkThug
Never Forget
Post edited by PolkThug on
· Share on FacebookShare on Twitter

Comments

  • dorokusai
    dorokusai Posts: 25,577
    edited December 2003
    "Bass Police" :D Damn them!
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
    · Share on FacebookShare on Twitter
  • PolkThug
    PolkThug Posts: 7,532
    edited December 2003
    Originally posted by dorokusai
    "Bass Police" :D Damn them!

    aka "girlfriend" :D

    "Why the f_ck did you go and buy another sub!!! You're gonna crack the foundation!!" -PolkThug's girlfriend aka Bass Police
    Never Forget
    · Share on FacebookShare on Twitter
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    Stacking two subs (all other things equal) yields a 6 dB increase in SPL. That is a HUGE increase and one of the reasons I always suggest stacking when adding sub #2.

    If bringing the second sub on-line yields more than 6 dB, it is running hotter than the first, regardless of its apparent amp volume setting. Try to make sure each one is calibrated to exactly the same SPL.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
    · Share on FacebookShare on Twitter
  • Seaward
    Seaward Posts: 56
    edited December 2003
    Dr. Spec..

    You mention that you recommend stacking the second sub. I take it that that really only applies if both the subs are the same. Currently I have a PSW-202 (free through a promotion) and have a GOOD feeling that the wife is getting me a PSW-404 for christmas, so in my situtation would you still recommend stacking the subs or having them in different areas of the room aor don't even bother with the PSW-202

    Thanks

    Seaward
    · Share on FacebookShare on Twitter
  • petertkim
    petertkim Posts: 4
    edited December 2003
    Wouldn't a capable sub achieve the same result simply by turning up the gain/volume?
    Also, how does the set-up sound with music? Isn't the base region way overemphasized? My understanding was that regardless of how many subs there are, they should be calibrated for an even response with the rest of the system...
    · Share on FacebookShare on Twitter
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    Originally posted by Seaward
    Dr. Spec..

    You mention that you recommend stacking the second sub. I take it that that really only applies if both the subs are the same. Currently I have a PSW-202 (free through a promotion) and have a GOOD feeling that the wife is getting me a PSW-404 for christmas, so in my situtation would you still recommend stacking the subs or having them in different areas of the room aor don't even bother with the PSW-202

    Thanks

    Seaward

    Stacking different subs might result in a bizarre FR. I would not recommend it, but it can't hurt to try and run a sweep and see how it looks with them together.

    You will have to calibrate them to different levels, though, to prevent from either overdriving the 202, or under driving the 404.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
    · Share on FacebookShare on Twitter
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    Originally posted by petertkim
    Wouldn't a capable sub achieve the same result simply by turning up the gain/volume?
    Also, how does the set-up sound with music? Isn't the base region way overemphasized? My understanding was that regardless of how many subs there are, they should be calibrated for an even response with the rest of the system...

    It goes without saying the overall bass level with dual subs should still be properly calibrated.

    The sub is easily the most susceptible to being overdriven of any speaker in a HT rig.

    What dual stacked subs buys you is another 6 dB of clean headroom over a single sub. That can make all the difference between the single unit choking (farting/bottoming) vice the duals making an effortless clean hit on the same passage at the same Master Volume at the same overall calibration level.

    A 6 dB increase is FOUR times the output. This is the coupling effect from co-locating twice the power and twice the driver surface area. Split up the duals, and you will immediately drop to only a 3 dB gain.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
    · Share on FacebookShare on Twitter
  • PolkThug
    PolkThug Posts: 7,532
    edited December 2003
    Dr. Spec: "If bringing the second sub on-line yields more than 6 dB, it is running hotter than the first, regardless of its apparent amp volume setting."


    hmmm... The second sub I turned on was the older sub. The first sub is very new. Maybe the difference of 8db instead of 6db is evidence of the elusive "Sub break-in beast". The first sub isn't broken in yet, so its running a little under par.

    Regards,
    PolkThug
    Never Forget
    · Share on FacebookShare on Twitter
  • walk
    walk Posts: 178
    edited December 2003
    Well it's gonna depend heavily on your room and listening position.

    If Sub A alone is measured at +3db at the listening position but Sub B alone is measured at +5db, then you're gonna get +8db with both, naturally.

    Or, you could be getting some standing waves/reflections, where the sound waves from Sub A are additive to Sub B's - that could easily amount to much more than a doubling of the SPL.

    Also, +8db measured == +6db, +/-2db.. I mean, how sensitive is your meter? The standard Rat Shack meter isn't that great. 2db is nothing to sweat over..
    - Sony 50"A3000 SXRD; Onkyo TX-SR 805
    - Polk RTi150 mains; CSi30 center; FXi3 surrounds, R15 backs
    - Velodyne CHT-12 subwoofer
    · Share on FacebookShare on Twitter
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    The +6 dB gain only applies to co-located subs. Co-location assumes the woofers and vents are so closely located that the difference in room position is negligible with respect to phase, standing waves, nulls, cancellation, etc.

    If you split up the subs into different corners/locations, all bets are off. When you bring that second sub on line, you might see +3 dB (that is typical), but if you are getting cancellation or funny room acoustics, it could even be less.

    Also, dB are log10 functions and cannot be added in the fashion you described above, but I think I know what you were getting at.

    And I agree, the RS meter is questionable in its ability to accurately reflect bass peaks. Clearly though, he is getting a "solid" 6 dB gain (and possibly a bit more if the second sub is running a bit hotter than the first), and that jives with what he should expect when co-locating.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
    · Share on FacebookShare on Twitter
  • walk
    walk Posts: 178
    edited December 2003
    Yeah I meant, if they measure differently, independently, then naturally they won't add up to exactly double the sound when both are used. He didn't mention measuring them independently, but that might be a good idea if he's curious.

    Even if they are "stacked", they might measure differently. I mean you can't *exactly* co-locate them, there's going to be a non-trivial difference in position, especially with the large cabinets these subs have. As you know, moving a speaker as little as 6" from a wall (or floor) can affect the sound quite a lot, especially where bass is concerned.

    Anyway, 2db on a Rat Shack meter I'd consider practically "down in the noise". I calibrate my system with one, using sine waves generated with my computer (SPDIF output), and if it's within 1.5db I call it a day. I certainly can't hear the difference. (Incidentally, most of the time I calibrate my system, I do it by-ear first, then check it with the meter - 9 times out of 10 it's within 1-2db ... I guess I either have good ears, or the RS meter ain't that great :) Maybe both :)
    - Sony 50"A3000 SXRD; Onkyo TX-SR 805
    - Polk RTi150 mains; CSi30 center; FXi3 surrounds, R15 backs
    - Velodyne CHT-12 subwoofer
    · Share on FacebookShare on Twitter
  • PolkThug
    PolkThug Posts: 7,532
    edited December 2003
    The third 505 for the stack should be here in a couple days. Hopefully I will see a 9-12db gain. just kidding ;)

    Thanks for all your input, its a lot of fun to experiment with these things. Without this forum I would not be enjoying my Polk's to their full potential. I am extremely happy with this setup.

    I still need to crash Henry's place and hear an SVS though....

    Regards,
    PolkThug
    Never Forget
    · Share on FacebookShare on Twitter
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    Originally posted by PolkThug


    I still need to crash Henry's place and hear an SVS though....

    Regards,
    PolkThug

    If you like your set-up, maybe you shouldn't............:p
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
    · Share on FacebookShare on Twitter
  • kberg
    kberg Posts: 974
    edited December 2003
    Uh-oh. I'm sensing that yet another poor soul may be craving an SVS in the near future. :)
    Mains: polkaudio RTi70's (bi-wired)
    Center: polkaudio CSi40 (bi-wired)
    Surrounds: polkaudio FXi30's
    Rear Center: polkaudio CSi30
    Sub: SVS 20-39 PC+
    Receiver: ONKYO TX-SR600
    Display: JVC HD-56G786
    DVD Player: SONY DVP-CX985V
    DVD Player: OPPO DV-981HD 1080p High Definition Up-Converting Universal DVD Player with HDMI
    Remote: Logitech Harmony H688
    · Share on FacebookShare on Twitter
  • J9_ls1
    J9_ls1 Posts: 20
    edited March 2004
    I have two 505's stacked in a corner, I gained right at 6db bringing the second one online. They match very well with my lsi15's.
    · Share on FacebookShare on Twitter
  • PolkThug
    PolkThug Posts: 7,532
    edited March 2004
    Originally posted by J9_ls1
    I have two 505's stacked in a corner, I gained right at 6db bringing the second one online. They match very well with my lsi15's.

    Cool! I thought I was the only crazy **** that did this.

    Regards,
    PolkThug
    Never Forget
    · Share on FacebookShare on Twitter