Got the SVS 20-39PC+, bottoming out?

Discussion in 'Archived Threads 2001-2004' started by Wendell, Oct 2, 2002.

  1. Wendell

    Wendell Stunt Coordinator

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    My brother got his pc+ on Monday. 20-39PC+

    His system is a H/K avr8000
    Axiom m80. vp150, qs8
    Fronts large and all other small crossed at 60hz

    Now we used the Sound and Vision calibration disc and all speakers are set up at 85db (volume at 0) with the SVS 3-4db hot using and radioshack db meter. Now on the THX intro, specificall the one that has the thunder and lightning effects, the sub bottoms out. Now if I turn the voulume to -6 it doesn't bottom out anymore. We usually listen at -10 which is equivallent to setting speakers at 75db. My concern is whether or not its ok for the sub to bottom out once in a while. Also, does anyone else have their sub bottoming out?

    I used the THX intro as a reference and tried to adjust the sub level by ear. NOw with the volume at 0 (85DB speaker levels), I kept playing the intro over and over while adjusting the gain on the sub. I turned it down so that it wouldn't bottom on the intro only later to find out that the bass was way to low during the movies. SO I went back to the original adjustment using the S&V disc with the sub 3-4db hot. Like I said we usually listen at the 75 db reference level and the sub doesn't bottom out as much.

    But to those people who listen at 85db, does your SVS bottom out?

    THe SVS is a great sub and it pounds and sounds excellent. But the bottoming out of the sub concerns me, I wouldn't want to damage it in any way. I guess it won't be to much of a concern listening at a 75db reference level, it sounded way to loud at 85 db anyway and I wouldn't want to go deaf. We do love to show it off though, just don't want to bottom it out during the process and possibly damage it which would really be embarrassing and stupid!


    Good Job SVS crew on the sub!
     
  2. Dustin B

    Dustin B Producer

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    I would not recommend bottoming a sub very many times.

    How big is your room and what do you have the sub sonic filter dial set at?

    Running a single PC+ sub 3-4 dB over full reference in a medium to large sized room doesn't seem like a good idea to me (potential of asking for almost 120dB at the seats from the sub, over 120dB if you set the mains to small). Calibrating the system to 10dB below reference with the sub 3-4dB above the other speakers does.

    What receiver are you using and have you tried running the M80 mains as small? Are you sure it isn't the M80 mains that are getting bottomed out?
     
  3. SVS-Ron

    SVS-Ron Screenwriter

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    Wendel,

    What Dustin said. If your room is large and or particulary difficult from a bass accoustic standpoint, something like the THX intro (which has low and loud bass that borders on the murderous in terms of LFE standards) you could simply be asking too much of a single sub. Even SVS's have their limits. I'd guess not much in the room isn't moving at that level??

    Of note at +4 dB measured you are actually set higher (the manual doesn't get into this detail) Depending on the exact nature of your technique -- (how it was held, where you stood etc) and the fact the RS meter will read as much as 3dB low on test tones, so your actual setting could be +7dB hot!. The only single subs that will "handle this with no problem" (as we sometimes hear) are the ones that simply engage a limiter of some sort and just stop going louder or lower (we use essentially none, YOU are the limiter in our way of doing things. We don't like speed or rev limiters on cars either in case you were wondering, for the same reasons, they get in the way! And just a bit of caution means you don't need them mucking up your sound).

    As Dustin hinted at, what is your setup of the sub? Your subsonic filter and port plugs are at what?? Remember that using a plug to lower tune will actually cause a slight loss of SPL capability up above the tuning point. So for semi-insane demos of THX intros as much as 7dB over reference level (with room an unknown factor) I'd actually recommend going with a stock tune (no plugs). Even so, you can expect to bottom if you run something that difficult that hard.

    As mentioned, you are OK if this happens ONCE IN A WHILE, but you either need to turn it down for reference level blasts, or eventually you will damage the driver (best if it never happens of course). If you are generally at -10dB on playback, then being set where you are is actually what we recommend for a fuller bass experience (see our manual for more). As you get more experience with the sub, keep trying your toughest DVD's to make sure your calibration and playback levels (for normal use, demos, whatever) are compatible.

    Some more time playing with the sub's location might be worthwhile too. I've seen swings of 9dB's in measured performance during calibrations simply by moving a sub a few feet!

    Ron
     
  4. Matt Meyer

    Matt Meyer Stunt Coordinator

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    I have a CS20-39+ and have not been able to bottom it out I have it 3db hot. Although I didn't try to bottom it out, but I do like the bassy movies at reference when the kids aren't sleeping[​IMG]. Also I thought the S&V disc was a 75db level? Like what Dustin said I would try to verify that it is really bottoming, I have had odd noises in the past which I ended up tracking down to something else moving(blinds, etc.)
    Matt
     
  5. steve nn

    steve nn Cinematographer

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    The intro you speak of is to much for me at reference. I will knock it down to -20 then back up to -15 or -12 after the intro. Asking one sub to handle such a task is asking for allot. I run a duel set for just this reason. You sound like a very good candidate for a duel SVS config. At your command, unleash hell.
     
  6. Ned

    Ned Supporting Actor

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    Pull out your meter and measure the actual SPL when the intro plays. 75 or 85db is irrelevant, what you are actually getting is probably in the area of 105-110db.
     
  7. Wendell

    Wendell Stunt Coordinator

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    Dustin and ROn,

    The room is 20'x24'. I'm sure it wasn't the m80 bottoming out, I was listening right next to the sub while my brother kept replaying the scene over and over.

    The sub has 1 port plugged and the ss filter is at 16hz.
    What the function of the ss filter?

    We usually listen at the 75db refernce mark and it's still very loud. My brother is looking at getting another pc+ in the future. And I came to the same conclusion that maybe we were asking for too much with just 1 sub. The only time we crank it is to show off the subs ability, we will play with more reference scenes and placement.

    What do you folks think about using the high/speaker level inputs to take off the load from the sub. The m80 seem to be good down to 32hz. I have my set up this way and feel the sub sounds better for some reason, it seem to integrate better.
     
  8. Mitch E S

    Mitch E S Stunt Coordinator

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    Wendell,
    Although that is a pretty big room I don't think your sub bottoming out during the THX intro is a real problem. I just upgraded from a 16-46CS+ to an Ultra running off a 660 watt Crown amp and it bottoms out during those intros and my room is only about 14' x 24'. I think THX has some deal going with the SVS guys to put some bullshit sound in there just to get me to order another Ultra[​IMG] I've watched all the LFE movies (Blade II, LOTR, the Haunting, Das Boot, JPIII, etc.....) and neither sub EVER bottomed out!!! I think we all spend to much time calibrating and not enough time enjoying HT. Other than the sub bottoming out during THX I'll bet a million he's pretty happy with the sub... On the other hand your brother's room might warrant a second sub. In fact I wonder if I could run my CS+ and Ultra together? Ever been done Ron, Tom???
    Thanks, Mitch
     
  9. steve nn

    steve nn Cinematographer

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    Mitch--"I think we all spend to much time calibrating and not enough time enjoying HT". That sure rings true in my ears. Here I am on V-K and I have spent way more time on the forum than HT.
     
  10. SVS-Ron

    SVS-Ron Screenwriter

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    Wendel,
    Again, given the large room (20x24 is big! Does it open to other rooms??) and the fact you are potentially in the +7dB hot range on the sub, it's no surprise at all really.
    We're talking near reference level bass to 10Hz and BEYOND (Tom's trace ended there but you can see there is significant energy trailing below that point). As your tuning sheet points out, plugging one port (and ratcheting down the subsonic filter) does give you deeper bass but it actually compromises total SPL capability some. You would give up a few dB's down low but you would probably have less problems with bottoming if you ran NO port plugs, and the 20Hz filter.
    For a room your size, with bass this loud/low, and running your mains as small, AND running +7dB hot, one PC-Plus (as fantastic as they are, and trust me nothing at this price point can touch a PC-Plus) twin subs... or a lower level for demos are in your near future.
    Contact us when you have the extra beans in your wallet, maybe I'll make you a deal you can't refuse.
    THX INTRO FROM THE PHANTOM MENACE
    [​IMG]
    I'm sure the THX engineers are still chuckling about putting the above on disk. Never mind most commercial subs simply start lopping off most everything on the left side of the scale. If you want ALL of this chart reproduced at above reference level, I'm afraid you'll need to dig into your piggy bank a bit deeper. The PC-Plus line is IMHO a world-beater. It does not defy the laws of physics however. We're still working on a model to do that ;^)
    Ron
     
  11. Dustin B

    Dustin B Producer

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    Edit: Grr, composing while Ron posted :p)

    Using the high level inputs won't take any load off the sub. That signal is converted to a line level one, run through the low pass filter in the amp (if turned on) and then reamplified to power the sub's driver.

    I'd try unplugging that port and turning the SS filter dial to 20hz.

    SS stands for sub sonic. That dial selects between 4 high pass filters I believe. The number on the dial being the corner frequency (or where it starts rolling off the bass). With the port unplugged you'll be tuned to 20hz and below 20hz the port no longer protects the driver. So having that sub sonic filter in place will attenuate the really low stuff protecting the driver from bottoming out.

    I'm not positive, you'll have to ask Tom to verify, but I think the sub sonic filter is setup so that in either this config, or the one you are currently using (port plugged and set at 16hz), it shouldn't be possible to bottom that sub. Can you describe what the bottoming sounds like. I'm wondering if maybe what you are hearing isn't port noise. In which case unplugging the port and changing the SS filter to 20hz should solve the problem.
     
  12. GrantM

    GrantM Stunt Coordinator

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    I've got a single CS ultra. After calibrating it using Avia and the RS meter the only thing it bottoms out on is the THX intro on SW: the Phantom Menace. I don't know the name of the trailer, it's the one with the "liquid ball" and the lightning and thunder. I haven't heard it bottoming out on LOTR, Blade 2, Titan AE, or anything else, including any other THX trailer.
    I'm glad to hear that the rare bottoming out won't harm the sub.
     
  13. SVS-Ron

    SVS-Ron Screenwriter

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    Dustin,

    Sorry about that!

    Grant,

    That's exactly what's posted above (I made this clearer now). With near ref. levels to 10Hz and deeper, and bass flat out off the chart (see the flat "anvil" around 30Hz) this is just about worst case scenario for a sub.

    Plugging a port will actually push driver excursion to extremes just about where the bass is at its highest peaks.

    Basically, this is one of those corrective action situations; such as: "Add a sub", "lower your current sub" ... "optimize subsonic filter and porting", and/or "optimize the sub's location" (or the ever-popular "all of the above ;^). Some receivers have "peak limiters" too that might be engaged but generally we're as eager to advise you do that as we are to recommend watching VHS tape. Who knows just what you are limiting, or not after that?? Don't go there we say, get your calibration right instead.

    In short, don't muck up the sound for a .0001% incidence of over excursion. As long as you keep your demo exuberance in check for that brief THX intro the other 99.999% of your calibrated viewing should be OK. Now if you find bottoming on other demanding scenes you might be back to the corrective actions above ;^)

    Tom Vodhanel (head of SVS R/D) might be along later with some more insight into how this demo material compares to only slightly less insane material from other movies emerging today. Suffice it to say the above chart is in at or near the top of subwoofer torture tests, one that will expose, as Wendel found, a slightly too hot calibration in a split second, (or alternatively, a sub that instead just lops off both amplitude and extension to compensate for excessive levels).

    Ron "beee the sub" Stimpson
     
  14. Heath Wade

    Heath Wade Auditioning

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    Slightly off topic...but one of my favorite things to do since receiving my new 16-46 PC+ on Monday is to play the THX intro scene from TPM with the two port blockers on top of the grill. When the globe explodes, the port blockers fly several feet away from the sub. It's like having my own sonic rocket launcher. If I could better direct the projectiles I might just have a nice weapon.

    Heath
     
  15. Wendell

    Wendell Stunt Coordinator

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    Thanks for everyones input! I don't really have a problem with the bottoming out since it only happens at demandindg scenes and extreme listening levels which is way too loud IMO. The room is once again 20'x24' with 10' ceilings and it's open on the left side to the kitchen and a hallway.

    Another scene in which the sub bottom out is in the MOnsters Inc. film where Boo is in the restaurant and the CDC/CDA comes to do their job right after the flee from the scene there is an explosion on their way to Mike's apt, this was also at extreme levels. At normal listening levels, 65-75db there is no bottoming out detected.

    My brother does plan on getting another sub in the future and will get back at your offer, Ron.

    I also agree with Steve's comments about calibrating and not enjoying.

    Anyways, thanks everyone and I look forward to enjoying more of my brothers' SVS at his home until I get my DIY sub finished up!
     
  16. SVS-Ron

    SVS-Ron Screenwriter

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    Good deal Wendell.

    Don't forget to experiment (when you are over there drinking your brother's beer ;^) with the port plug and subsonic filter. You might try running the same uber-hot calibration with NO plugs and the 20Hz filter switched in and see if just those two things help. You would loose some extension, but greatly ease the stress on the driver in terms of EXCURSION, especially in the critical 25-35Hz range.

    You might find this combination actually works to get the bass jones working better (i.e. higher undistorted SPL, with less deep bass). Anyway, keep us posted. As long as you avoid excessive bottoming the sub will last a long time.

    Ron
     
  17. Edward J M

    Edward J M Cinematographer

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    The Star Wars PM THX Exploding Ball Intro is mastered SO OBSCENELY HOT that anyone who tries to play it at reference levels is simply asking for trouble.

    I will even go so far as to say it was completely irresponsible on the part of THX to master the ball explosion so much hotter than the actual PM soundtrack.

    The actual PM soundtrack is mastered just about right with respect to overall volume levels and bass peaks and I play it at reference level (-15 on my receiver) with my 20-39 PC+ and I have recorded SPL peaks of 110 dB at the listening position during the pod race and have never bottomed out the sub - not even close.

    If I left my volume at -15 and played the THX intro, I am absolutly positive my sub would bottom. I click it down to -23 or so for the exploding ball and I STILL recorded bass SPL peaks of around 110 dB at the listening position.

    This tells me the explodng ball intro is mastered about 8 dB louder than it should be - kinda like the ENTIRE sountrack of LOTR-FOTR.

    If you are ALREADY at reference level on your HT receiver and you play that THX intro, you can expect really REALLY bad things to happen when the ball explodes.

    Be sensible, ratchet the intro back about 8 dB, and enjoy it - it really IS quite awesome. And just admit the THX sound engineers played a bad joke on us.

    Ed Mullen
     
  18. Dustin B

    Dustin B Producer

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    A bass peak of 120dB would still be within Dolby's reference spec.

    My Tempest doesn't complain at all when I play that intro at 5dB under reference with the sub 2-3dB hot :p) Although the rumble filter on the plate amp and 16hz tune surely help this a lot.
     
  19. Mark Zimmer

    Mark Zimmer Producer

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    Huh, I've played the THX intro a couple times on my driver-upgraded 16-PC46 at reference, a couple dB hot, and never had it bottom at all. I must be lucky or my room acoustics are good. Either way, the PCi--not even a + or an Ultra--has taken everything I've thrown at it with flying colors, without straining---even LOTR:FOTR Last Alliance battle at full reference (though not for long before my ears began to bleed). [​IMG] Color me extremely satisfied.
     
  20. Duvall

    Duvall Agent

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    The globe explosion on the THX intro to Phantom Menace is the only thing that's bottomed my dual PCPlus', but a little twist on the sub output knob takes care of that. The strangest thing sometimes happens....The first time I play the intro, the globe can bottom the sub if running a little hot, and then subsequent runs through it using the chapter replay button, not accessing it from the DVD menu, it may not bottom. Go figure?

    See ya. Dave
     

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