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differences between svs subs/drivers

Discussion in 'Subwoofers' started by pfote, Feb 22, 2005.

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  1. pfote

    pfote
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    Hi there :hiya:

    have asked that question in germany but no one could answer it, so i try here, assuming the SVS community is substantially larger:
    i wonder how big the differences between the drivers in the SVS Subs is, especially as even the smallest SVS (PB10-ISD) is reviewed as beeing linear down to 20Hz and produces sharp, clean bass sound.
    my room is rather small (20 square meter) so i don't need any high level output, probably a PB10 would do just fine but i hate the idea of sitting in my room with a excellent PB10 and wonder what i might have missed compared to a PB12-ISD, -Plus or even -Ultra :rolleyes:

    so how big are the quality differences between these beside sheer power ?

    i hope my english has'nt become to rusty :D
    greets from germany
     
  2. Diamond

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    10" ISD is closer to Plus or Ultra than ISD, SV-crew have said. I've got 16m2 apartment/room, and it does shake things well. Some have said it fills even 30m2 room, but it depends on you. If you have more money, then invest on a bigger cylinder/ box, my next upgrade couldn't be lesser than PC-Ultra, the differences are pretty small. Can you live with a 10", it's pure psychology. It depends so much on your room also, and if you can blast it with full potential. Some use even PB12-Ultra/2 in those rooms..

    Buy the biggest you can afford, includes buying a BFD (Thomann) for eq'ing it, Bettercable and an RS-meter. Those are minor purchases, but they improve the bass a lot. AVIA-dvd is also recommended for setup. I'd guess that well calibrated ISD sounds better than poorly set Ultra. ;)

    P.S. PB10 goes 18Hz flat in my room, now before I've eq'd it. The more expensive ones do the same with greater headroom.
     
  3. pfote

    pfote
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    oh if it's psychology .. i can live with a 10" driver :D

    room is a bit of a problem, allready have a SPL meter (and used it :)), i have to much SPL in the 30-40Hz area (about 10dB), but i'm unsure if thats room gain or my current sub (velodyne vx10), right now i have no possibility to do a free field measurement of the sub

    also i have a -15dB hole at 37Hz which corresponds nicely to the 1st-order room mode of one wall (4.7 meters) and still no clue how to get rid of that as space is limited and i have only a few postions where i can place a sub :(
    and yes, next purchase will be a BFD to see how much i can tweak the velodyne to become somewhat flat
     
  4. eviljohn2

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    Diamond,
    Where have you seen the 10" ISD driver compared to the PCU driver? There's a big difference between the PC+ driver and the PCU driver. I know that Tom Vodhanel says that the 10" ISD driver is closest to the PC+ driver but hadn't heard the other comparison.

    pfote,
    A 10" driver should be plenty for your room. You'll lose the ability to move huge amounts of air around the room but the sounds will still be produced.
    I wouldn't worry about free-field measurements since you'll only be using your sub in your room! They're useful when reviewing/comparing several subs but no good in a normal home environment. The even worse news is that there isn't really anything you can do about your 37Hz dip so just ignore it, it's not going to show up under normal listening conditions, :)
     
  5. Nimby

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    It might be possible to move yourself (and your listening chair of course) to a point in the room where the dip (or a peak) isn't present. Since room modes consist of fixed positive and negative pressure points. Or in-phase and out-of-phase points on standing acoustic waves. This is always an option to moving the subwoofer. Though neither tactic is guaranteed to succeeed. Fortunately dips are much less noticeable than peaks. :)

    Nimby
     
  6. pfote

    pfote
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    @nimby
    moving listening position is also not possible :( i have a big leather couch that fills the room, allready shifted it a bit into the room to have my rear speakers at least a bit behind me, but thats it. bought it before i even discovered the hobby HT, but i start to regret it ..
    but that 37Hz dip isn't that important .. as you guys said, better a dip than a peak that makes everything shaking ;)

    did i get you guys right, from the sound quality perspective you would rate a 10" ISD over a 12-ISD, more like a 12-Plus ? interesting ;)

    oh and btw, what does "headroom" mean? translating via dictionary didn't give any sense

    anyway, tnx for your advices so far :smashin:
     
  7. Ian J

    Ian J
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    It is slang. Headroom in the subwoofer sense refers to the power in reserve
     
  8. Ian J

    Ian J
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    I have both a PB-10 and a 20-39 PC plus and find it difficult to tell any difference unless I am driving the smaller one very hard.

    If I understand these new metric measurements that you are quoting, my room is slightly larger than yours and I have no problems with the PB-10 at reference levels
     
  9. bob1

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    I used to have a vx10 and it started to dropped at 40hz and did very little at 30hz, it was a good first sub though.The dip at 37hz will be the normal decline of the sub helped with a dip, any peaks below that will be room gain.
    I now have the svs pb-10 with a bfd ,i'm not looking forward to going to the dentist to have my fillings refitted. :eek:
     
  10. pfote

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    @Ian J
    man, you made my day ... "new metric measurements" :D
    bear with me, i'm german ;)

    @bob1
    that scares me a little what you say about the vx10
    these are the measurements i did last weekend with a cheap Voltcraft SPL (should be the same as the Radioshack recommended here, just relabeled), the important line is the red one (sorry for the german labeling, but i think you'll get the point)
    if all below 35Hz is room gain, then i have a real problem, because then a SVS will shake the walls :eek:
    [​IMG]
     
  11. Tom Vodhanel

    Tom Vodhanel
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    Hello,

    I addressed this qeustion a short time ago on a different forum. Here is a copy/paste of my text...


    First, remember that terms like “fast”, “tight” ,”musical” are subjective in nature. So by definition, what audio enthusiast A thinks is "fast/tight/musical"...audio enthusiast B may not. Also, human bias will enter into the equation at some point. for example, If a manufacturer goes into great detail about how “fast” their bass is...after reading enough about that...some folks will naturally have a predisposition to believe it. So when they get the product home...by god the bass IS fast.. (this is the same human workings that cause us to hear differences when painting the edge of your CD green---well, the website explained it in 5 pages with big words and they have a bunch of testimonials...so...)

    When talking about "fast bass", a famous subwoofer reviewer once said to me..."oh yeah, the bass was so fast it got out of the room before I could measure it". This is referencing the fact that often, what we consider "fast bass"...simply means no low bass.

    It is important to consider the length of sound waves in this context and how that relates to their decay in a typical room. A 20hz sound wave is about 55ft long. The longer the sound wave, the more time it is going to take to decay. This longer decay time is often interpreted as “slow bass” simply because the bass doesn't *snap* to a sudden stop(as it may with a subwoofer that rolls off in the 35-50hz range). It isn't a coincidence that the majority of subwoofers that claim to be “tight/musical” are small/moderate sized sealed designs. If you look for objective performance data on these units, you'll notice there is one definite trend...they all tend to have a frequency response which rolls off in the 32-50hz range. Tom Nousaine has a lot of good FR data on a ton of subwoofers. Audio magazine and Audio Ideas Guide both used to have a lot of FR data in all their subwoofer reviews too. (AIG might still, haven't had time to pick up a copy for a few months).

    Now, there is nothing wrong in preferring that type of sound...it is a personal preference after all. But the correlation between what you think is “fast/tight” often has little to do with any magic a given manufacturer knows...and more to do with the very basics of the units performance...the frequency response(and several other factors introduced below).

    Among SVS designs, the Ultra driver is definitely top dog. I'm not going to wax poetically about its design...it is just a very good unit(and very expensive). The dB12 (Plus driver) is also a very good design, just not up to the same standards. The same can be said for the ISD driver we use in the PCi/CS,PB-1 and PB-2isd subwoofers. At low volume levels, all three of these units are going to sound quite similar...only as the volume levels increase will the qualities of the dB12 and then the Ultra driver manifest themselves into grossly audible benefits. Just how MUCH the volume levels would need to increase depends on many variables...and just how audible the differences were...would depend on additional variables...including the listeners experience and insight into how these difference may present themselves during source material playback. Here is an example of how THD (total harmonic distortion) may present itself…

    Let’s use 25hz and 90/95/100/105/110dB levels (just an example remember…)

    The Ultra driver may produce <1% THD up to 100dBs, than 3% at 105 and 6% at 110.

    The dB12 driver may produce <1% up to 95dBs, 2% at 100dBs , 6% at 105dBs and 9% at 110dBs.

    The ISD driver may produce <1% at 90dBs, 2% at 95dBs, 4% at 100dBs, 8% at 105dBs and 12% at 110dBs.

    Now, you can say…”well, the ISD driver has 4x (!) the distortion at 100dBs…boy that would HAVE to sound just god-awful. Well, maybe. If you were listening to a sine wave. With source material…this difference will be inaudible in just about any imaginable scenario. (the difference between 1% and 4% THD at 25hz) Most folks will notice the difference between 1% THD and 10% THD. But anything <5% (<35hz) is going to be very tough to discern with source material (and practically impossible with the LFE on DVD-films).

    The interesting part about THD, since it manifests itself at multiples of the source frequency...a higher THD level can actually make the subwoofer seem more musical. A musical instruments sound is defined by its harmonics. A bass guitar playing a 42hz note will have it's THD at 84,126,168hz (ect). So a subwoofer having a higher 3rd order harmonic (126hz)...can actually give the audio presentation an "easier to follow" bass line. Since that 126hz harmonic is now louder (than it was with the subwoofer with less distortion).

    Another important issue is dynamic compression. A subwoofer that doesn’t suffer from much dynamic compression is often referred to as “effortless” in subjective descriptions. One way to test for this is to loop a bassy scene on a DVD and to turn up the system in 3dB steps. Set your SPL meter at any spot and check to see when the bass stops increasing the full 3dBs. At some point…it will only get 2.5dBs louder, 2dBs louder,1dB louder and finally…it will stop getting louder. I would only recommend raising the volume until it only got 2dBs louder because by that point…the subwoofer is already straining. Pushing it further will only increase any chances of damaging the unit.

    Another example, …say a 2500 cu-ft room, and a nice 26hz LFE scene(like the heart beats in the opening scene of The Professional…) Let’s say 1 meter from a corner loaded unit.

    A 20-39PCi may begin to show some compression at 110dBs. Impressive, but still 11dBs under reference level with all speakers set to small. A 20-39PC+ may get to 113dBs…and a PC_Ultra may get to 115dBs. So in this context(all other factors being equal), the PC_Ultra will have about double the clean output capabilities of the 20-39PCi…if dynamic compression is one of the factors used in determining that(clean output). The driver directly relates to compression in two primary ways…excursion capabilities and thermal compression. If the driver cannot move any farther in one direction…the nass will stop getting louder. Once the voice coil heats up to a given temperature, the driver won’t be as efficient in turning electrical power into mechanical motion. In this regard, the Ultra driver has a big advantage over the ISD. It isn’t that the ISD is a substandard unit…but with a 10 layer custom would coil…the thermal capabilities of the Ultra driver are incredible.

    So?

    On louder, sustained bass…it wouldn’t surprise me if someone felt the dB12 driver seemed “tighter” than the ISD. And, it wouldn’t surprise me if someone felt the Ultra driver seemed “tighter” than the dB12. (I know ,I know…all that and my answer is actually two sentences long.

    A quick comment about bias.

    No one really wants to believe how easily their senses can be fooled. For some it involves ego..."not MY golden ears"..

    There is tons of research on this of course. Listener bias can be sorted into three categories: sensory, psychological, and social. Psychological biases make us susceptible to cognitive errors in judgment. We tend to hear differences when none exist. When given the same exact audio stimulus and asked if we prefer either or hear no difference...over 75% of the time we prefer one over the other. Social bias and sensory bias are self explanatory I would guess? Some folks won't really like the way I attempt to put everything about their hobby(audio) into objective frames of reference. So when they hear a product from SVS, they will automatically feel it lacks something abstract. Nothing that can be named of course...just some silly type of un-measurable "magic" SVS doesn't know about.. Others may like my *style* and they may tend to hear advantages in our products that don't exist. Both are examples of "social bias"...and I think we have all seen examples of both at work.

    Tom Nousaine has said (during a review of a Velodyne HGS15)...

    "What? No long protracted subjective experience discussion where I wax enthusiastically(or vice versa)in eloquent poetry about how this product makes me feel? Nah. The worth of a subwoofer is determined by how deep it goes, how loudly it will play, and how smoothly it does both."

    Subwoofers should do just that, any poetry should be in the source material they are reproducing.

    Tom V.
    SVS
     
  12. bob1

    bob1
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    I have graphs of all the subs i have owned HERE.
     
  13. Mobster

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    I've read statements like this many times. And every time I stop for a moment and think "Loud - good, , deep - good, but where's the accuracy?!?".

    I think there's a bunch of subs that are loud and go deep but the bass is out of control and does not follow signal accuratelly. Impulse response, spectral decay, group delay... A loud and 'deep' sub can still give bad figures in all of those. AND sound slow.
     
  14. Smurfin

    Smurfin
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    That is one of the best comments I've read in ages. There's so much psychological bias out there, people are easily fooled. And yes, I've been one of them many a time:)
     
  15. pfote

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    tnx for the url .. your graphs tell a complete different story than my measurements, so there must be substantially room gain in there
    looks like i better get myself a BFD to be prepared :cool:
     
  16. pfote

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    @Tom Vodhanel
    got your points about the different SVS chassis, TNX :smashin:

    very insightful article, mind if i'm quoting that in a german forum as well ?
     
  17. Tom Vodhanel

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    Hello Pfote,

    It was only a post I made on a different forum a couple of months ago. ( Not a published article or anything like that). Feel free to quote it though.

    Tom V.
    SVS
     
  18. Diamond

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    Did I say there was no difference.. I'm sorry if it came out that way. Maybe I've read wrong, but I remember so. (If Plus is closer to Ultra than PCi, then I guess PB10-driver is also closer to Ultra than PCi.) Nobody of us really knows these things, but the crew themselves. Have you asked about that steep infrasonic filter (?) in PB10 that you found?
     
  19. Ilkka R

    Ilkka R
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    PB10's woofer is called dB-10, so it's very close relative to dB-12 woofer which is used in PC+ series. Ultra's TV12 woofer is very different from both of them. ISD is also a different line.

    PB10 has a steep infrasonic high-pass filter at 18-19Hz, Edward's test clearly shows it.
     
  20. Tom Vodhanel

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    I'm sorry there is some confusion about our various drivers and how they may compare to one another. I suppose SVS should shoulder much of the blame for any confusion regarding this topic as we don't really like to get specific about a lot of the technology in each driver( esp the t/s parameters).

    The 10" driver that we are using in the PB10 was a "ground up" design. However, we have learned a great deal about driver design in the past 5-10 years and, naturally, we'll incorporate that knowledge into any new design. There are certain qualities about the PB10 driver that parallel the 12" ISD the 12" dB12 and the 12" TV12. However, if you had to pick one to consider its closest "relative"...it would be the dB12...or more accurately...the dB12.2. It looks the part...primarily because of the frame.(although the cone looks more like the ISD). And the actual "motor" is very closely related to the dB12.2. I'm not sure if we "officially" call the 10" driver the "dB10" on the website...but that is what we started calling it around the r/d labs a long time ago. We went thru...at least 20 different 10" designs...and we just have to call them something to keep things clear when we are testing hundreds of design variations over the course of months..:)

    If you were trying to gauge the performance gaps between the ISD, the dB12.2 and the TV12...the gap between the ISD and the dB12.2 is larger in most important considerations. While the TV12 is a definite upgrade over the dB12.2...you are really getting into the "law of diminishing returns" once you get to the performance level of our plus subwoofer/drivers.

    I hope this answers some questions, please, always feel free to let me know if there are other questions about our products.

    Tom V.
     
  21. Ilkka R

    Ilkka R
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    Tom, when did the dB12 change to dB12.2? What are the main differences?
    And don't try to hint that the dB12.2 and TV12 are somewhat close to each other, we know that they aren't. :D
     
  22. Rip

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    Are you saying that the TV-12 drivers in the PB12-Ultra/2 are superior to the dB-12's in the B12-Plus/4 sub ?
     
  23. Ilkka R

    Ilkka R
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    Of course they are. Superior is a difficult word to understand properly, I'd say they are much more better. PB12-Plus/4 uses the same dB12.2 drivers as the "cheap" PC+ line. I believe SVS/Tom has its reasons why not to make PB12-Ultra/4. :cool: (weight for example)

    PB12-Ultra/2 is their best sounding sub, Plus/4 is the loudest. :)
     
  24. Rip

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    Is that just your opinion, or the official SVS line on things ?
    also
    I cant belive weight would be a reason not to make a PB12-Ultra/4, i mean, once you get it into place, your not really going to be carrying it around in the park on your shoulder like a stereo are you.
     
  25. eviljohn2

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    Rather than one enormous PB12-Ultra/4 it would seem more sensible to buy a pair of PB12-Ultra/2's. A cabinet with 4 drivers like that would be quite difficult to construct and brace properly amongst other things plus then the amount of space needed for power would be huge. Maybe a design like that would have to be passive.
     
  26. Daneel

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    AFAIK the B4 is a completely different design to the other box subs, using a push-pull arrangement.

    The difference between the drivers is very clear if you look at them. The old ultra driver is quite close to the current plus driver.

    Over at Hometheaterforum and AVSForums this has been talked to death already. Run a search.
     
  27. Nimby

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    It's only another opinion, but when it comes to the ultimate output a pair of 2 x 12" subwoofers, placed side by side, is probably a better way to go than one huge 4 x 12" box. The 2x12's offer far more flexibility in siting and are more customer/wife friendly than one large 4x12".

    The panels of a smaller enclosure are naturally stiffer. Meanwhile it is easier for the cleaning lady to lift a 2x12" to brush the dust underneath. But don't try this at home children! :D

    Nimby
     
  28. Smurfin

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    The current B4/Plus is passive as it is:) I think they offer Crown amps as part of a possible package.
     
  29. Ilkka R

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    Yes B4 is different desing, but it uses the same dB12.2 drivers.

    Those drivers in that SPOT thread are old Ultra and new Ultra (TV12).
     
  30. Ilkka R

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    Lets see what Tom says? ;)
     
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