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"never Buy A Downward Firing Sub!" (1 Viewer)

Tim Hoover

Screenwriter
Joined
May 27, 2001
Messages
1,422
I've never experienced the so-called "pants flapping" effect with my 20-39PCi, but in my 15x25 listening room, it definitely pressurizes the room very well. It's more than enough woofage for my needs, and if cranked will cause my entire house to groan in agony :D
 

Phil Iturralde

Screenwriter
Joined
Oct 7, 1998
Messages
1,892
Thanks John, very well written! Your explanation about my HT/Family room is not really theory since it provides reasonable facts that contributes to what we've felt, ... the tactile 'pant-leg' moving LFE sub-sonic impacts encoded in my blockbuster DVD's!

Maybe, the following Product Review "SVS 25-31 PCi Powered Subwoofer" (December, 2002) by John E. Johnson, Jr. explains much of the tactile pant-leg(s), couch, floor, chair, and wall air-moving LFE effects ...


Steve, very impressive! As a semi-professional musician that protected his hearing during the 7 years of part-time gigs, high SPL was never my goal. My goal was to reproduce the Sub-Sonic Impact FEEL and Cinema Theater BALANCE, that a few of the better (JBL equipped) local SF Bay Area Theaters had, ... and I've attained that and beyond, ... with my little, nearly 3-year old, $549 + SH SVS 25-31PCi!!! :D (yep - the SVS Grin!)

Phil
 

WayneO

Supporting Actor
Joined
Nov 10, 2003
Messages
625
OMG...........the mileage outta this thing..........:D

There's another member of these forums, MikeLi I beleive, who uses the "make my chest hairs stand up" note quite often when describing his SVS. Now that I'd like to see.............
 

Jed M

Senior HTF Member
Joined
Oct 2, 2001
Messages
2,029
I own two SVS 20-39CS+ and my friend owns one. For some reason my system gets just as loud, but his causes pant flapping and mine does not. Very similar size rooms so I don't know what the cause is but it is real in some rooms.
 

steve nn

Senior HTF Member
Joined
Jan 12, 2002
Messages
2,418
quote:
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My daughters told me their windows were bowing out-stiars during that one 127 db test.
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Steve, very impressive!
__________________________________________________ _______


Admittedly that was back in the day. I don't go there any more and my ears are better off because of it. Lets just say my goals have changed over time as they do with most.

Phil I have always thought the 25-31 has been under-rated by many though. I see members come along and want the most slam for the $$ in a largish room and the 25-31 wont even be mentioned. The impression I get, is they think the 16-46 is bigger and more expensive, so thats the way to go or the 20-39. Sure the 25-31 wont play the loudest in the lowest FR, but imo it'll do justice on 95% of the material out there and do it well. With the EQ benefit the on-board bash amp carries, it'll do better than what I experienced with my CS+'s. I really noticed this with the 10-ISD PC-Ultra and the PB12-Ultra/2. Im basically flat down to 20 Hz or so with the PB12-Ultra/2 in it's stock 25 Hz tune as opposed to a steep roll-off at around 23 Hz with the out-board QSC amp running the 25 CS+'s.

I don't know what got me to ranting on about the 25-31 but maybe it's something I needed to get off my chest:D

Who wants to share next?:)
 

EdwinK

Agent
Joined
Oct 29, 2004
Messages
38
In rooms around 30-40 feet you will experience huge gain in the 14-19Hz region with corner placement, ideal for subs like my PB12-Ultra/2 with zero or one port plugs.

Currently I have it placed near the "virtual center" of my 16x16 room - with open kitchen, to prevent all the unwanted gain around 20 and 35 Hz.

My ideal room would be about 30 by 40 feet, with maybe even a single PB12-Ultra/2 doing all the work, placed much better (in the corner). I bet it would perform much more impressive under those circumstances, not that it isn't VERY impressive at the moment. ;)
 

ChrisBee

Stunt Coordinator
Joined
Mar 4, 2004
Messages
195
EdwinK said:

"In rooms around 30-40 feet you will experience huge gain in the 14-19Hz region with corner placement"

Thats interesting! I hadn't ever heard of "large-room gain" before.

In my 30 foot attic listening room my 16-46PCI is +10dB at 15Hz(!) That's when calibrated perfectly 'flat' with my 38Hz floorstanders.

A smooth rising ski jump into infrasonic limbo and a remarkable built-in house curve! No wonder the house shakes when my wife adds another +6dB on rock music! The sub is eight feet from the corner! :D


Regards
ChrisBee
 

EdwinK

Agent
Joined
Oct 29, 2004
Messages
38
"16-46PCI is +10dB at 15Hz(!)"

Whow! At best I can make it flat at 15Hz, with both port plugs fitted. I guess you really didn't need to buy the 16-46 sub, and could have gone for a more 'mainstream' SVS. :)
 

Ryan Tsang

Second Unit
Joined
Sep 23, 2000
Messages
372
Why don't we all decide on a common testing protocol to determine how capable our subs are in our respective rooms? The purpose is not to brag about who has more muscle or cash, but eliminate the subjectivity. When someone quotes, "that explosion brought my house down!", I want to know exactly how loud that is. Some newbie might think 100db at 35hz is the best thing after sex, but someone like EdwardJM or Mitch is yawning at the same scene.


Perhaps some of the experienced ones here can devise a simple protocol that is cheap, easy to use, and widely accessible. No fancy mics, RTAs or computer programs that need a laptop. I'm no pro so feel free to poke holes in my idea, I'm sure it's far more difficult than I'd like to think it is:

-test tones, sine waves, maybe download from common source
-describe your calibrated level. How hot are you?
-make sure everybody playback at a certain level. This would depend on the source material, cuz it if you played a cd at
-5db ref, something will break, either your ears or your
gear
-use RS meter cuz everybody has one.

This way, Phil and John can say "Look guys, we can hit 110db at 25hz at -10db on the dial in Phil big-ass room with a single SVS!" And then Mitch can say "I hit 115db but I sit only two ft from my B4." You would have numbers to back up your claims instead of measuring how much flappage there is.
 

ChrisBee

Stunt Coordinator
Joined
Mar 4, 2004
Messages
195
"Whow! At best I can make it flat at 15Hz, with both port plugs fitted. I guess you really didn't need to buy the 16-46 sub, and could have gone for a more 'mainstream' SVS."

Now you tell me! :D

Nobody on another AV forum could believe my reports on my sub. They called me biased and said I was exaggerating. Now I know why! A completely free subsonic SVS lunch. Thanks again for that info on big-room gain. :)

Regards
ChrisBee
 

Seth_L

Screenwriter
Joined
Apr 5, 2002
Messages
1,553

Room gain kicks in once at the frequency where 1/2 a complete wavelength fits in the largest dimension of the room. A room where the largest dimension is 30 feet won't start to have gain until about 18Hz. At 40 feet you don't start to get gain until 14Hz. Keep in mind you get 12dB per octave, so that room where the gain starts at 18Hz, is 12dB up at 9Hz. So, in rooms that large I wouldn't count on a lot of gain to be helping out the sub's low frequency output.
 

Mitch Stevens

Supporting Actor
Joined
Apr 27, 2002
Messages
581
Disconnecting ALL speakers except for the B4+ (no ports plugged), I am able to hit 118 dB (uncorrected) on the first track of Noelia's new album "Melao."

I hit 121 (uncorrected) dB Playing Christina Aguilera's "Stripped Into" as well as the 2nd song, "Can't Hold Us Down" all at my sitting position (2 feet away). This is of course with all speakers disconnected, and just the B4+ playing the the only bass in the room. I have no idea what hz these songs have encoded in them though.

Even at these "extreme" Sound Pressure Levels, my clothes don't "flap" around. I feel air pass THROUGH my shirt, but it doesn't make it "flap" around.
 

Lewis Besze

Senior HTF Member
Joined
Jul 28, 1999
Messages
3,134
Like it's been said your aproximation to the sub will be just as important if you want to reach any where near reference levels, at any given fr.[provided you sub's fr is flat]
 

frank manrique

Supporting Actor
Joined
Sep 15, 1999
Messages
798
My son and I have experienced the pants legs flapping effect during the 1812 Overture's finale (Telarc) with low bass wavefronts produced by the SVS 16-46 octet.
We were standing about 14 feet from where the subs are located. The sound pressure level output was fairly high. I did not recorded any numbers; I was merely showing my son what "that many" tubed subs could do, one of the SEVERAL reasons I bought them (however, I might as well state that this is not a matter of course practice I would recommend for serious music listening ;) ).

The pants legs flapping effect may not be a scientific way to describe what high output infrabass wavefronts can cause, but it sure is lots of fun!... :D

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."
 

EdwinK

Agent
Joined
Oct 29, 2004
Messages
38
I disagree, unless you were talking about huge sound stages or listening outside. In real-world rooms it is the size of your listening environment that determines how much energy it takes to reach a certain SPL at low bass frequencies. That, and of course the position because of local cancelations/peaks.
 

brentl

Senior HTF Member
Joined
May 7, 1999
Messages
2,921
I really wish I could feel the "pant flap", but in my 50'-50' unfinished basement(with a concrete floor!) I"m usually pretty dissapointed.

Brent
 

Lewis Besze

Senior HTF Member
Joined
Jul 28, 1999
Messages
3,134
You're mistaken, the original poster didn't inquired about infrasonics at all, only the orientation of the driver.
 

EdwinK

Agent
Joined
Oct 29, 2004
Messages
38
For lower bass the sound you hear is the sum of many reflections, not the sound that reaches you directly (unless you put your head inside the sub :D). It is higher harmonics that makes bass sound snappy and gives it direction. There are many places with interesting reads about this subject on the net.
 

Lewis Besze

Senior HTF Member
Joined
Jul 28, 1999
Messages
3,134
Why don't you get an SPL meter and start to play a test tone[prefferably a filtered pink noise],and then move away from the sub slowly in a straight line, while you read the meter[don't need to search the net on this one], is the level dropping? There you go, and guess what, this will happens in every room, shape/size.
 

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