shadyJ
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Posts posted by shadyJ
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I would love to participate in a blind test group. Whether it be speakers, subs or even amplifiers. I think it would be a fun way to find out how good my listening skills really are or aren't. Something like a large AT screen setup to hide the equipment in a quiet outdoor setting would be great to eliminate room acoustics. Have a test group take notes and apply ratings on a 1-10 scale in a variety of subjective categories. Take measurements of each setup to match up with the listener notes and scores afterwards. It would be great if someone did a serious GTG just for this purpose.
This has been something I have always wanted to do as well. A real qualitative subwoofer comparison would have to be done outside (or in a room as large as an indoor stadium). Also, as you say, the equipment would have to be hidden. That is the only real way to fairly compare subwoofers, at least with human ears. They would have to be compared using fast A/B switching between the subs as well, at least for complex signal content like regular movie or music content. The problem is, GTG's are all about having fun, not rigorous testing. I wouldn't want to ruin a GTG by insisting on rigorous adherence to a strict testing regimen. GTG's are usually about drinking a lot of beers and seeing how loud some speakers get, and that is fine, but this kind of testing wouldn't work for that kind of gathering.
I would want to see if these subs can be distinguished when they are operating well within their linear ranges. SME seems to think that there would be a difference. I don't think there would, but such a test, if conducted appropriately, would certainly serve as good evidence one way or the other. Neither SME or myself would be able to properly participate, because we already have predispositions that a blind test could not overcome. Still, I would love to hear it for myself.
I need to secure some kind of grant to do this with.
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Ilkka Rissanen and Ed Mullen did a study of IMD in subwoofers and found that subs with low THD also have low IMD. You can read about it here, if you don't already know about it. It is not a surprising result really.
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Obviously power handling and displacement are important factors when one is pushing the system toward its limits. And from your description, using 50% of available travel for peaks is "pushing it". I.e., maybe peaking at 25% is preferable.
But, what if one is not pushing things at all? If operation is kept below 10% of peak excursion and 1% of power handling capability, presumably displacement capability and power handling are not important. Are there differences in sound quality between drivers that are still apparent under these conditions? Let's assume that the driver is otherwise "competently implemented" enough that there is no audible noise or buzzing under such conditions.
My impression is that such differences do exist and can be substantial, but I admit that it's hard to prove.
Look at the subject from the perspective of sound pressure waves. As long as the driver is turning the voltage signal into sound pressure waves at a 1:1 relationship, it is a perfect reproducer. Anything else is distortion, whether linear or nonlinear. If you have no linear distortion and you have no nonlinear distortion, you have perfect accuracy. Of course, that is the unattainable ideal, but a very good system can get close. With effort, you can get a very flat response that has insignificant distortion quantities. What difference does it make if that is achieved through a $5k super driver or a $30 buyout driver from parts express? A good driver, when it is operating at nominal levels, can have distortion quantities of 1% or less and so is inaudible. If the frequency response is flat, and it isn't making any mechanical noise like flutter noise, there is nothing else that can distinguish these units, so long as they have the same dynamic range.
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That's one way to look at specs and make a judgment.
The missing critical factor is displacement and power handling. All of my experience has taught me that systems with greater headroom sound better. IMHO it is one of the biggest factors to consider and this goes against the old-school audiophile or "SQ" wisdom that loud & big = Not as accurate . Some of the drivers high up on the list such as the JBL 2242, AE TD15M or Faital 18HP1060 have limited xmax for making bass and lower headroom unless using many drivers. They are better woofers or mid-woofers than they are <100Hz devices.
In an ideal world the signal coming out of the subwoofer and delivered to your ears / body would be exactly what is being sent into it electrically or alternatively exactly what you want that to be that fits your listening tastes. There are so many ways that it can be distorted. It can be smeared in time through room related nulls and resonances, system group delay, ringing, resonances etc. The frequency response can be skewed in a number of ways. By the room, the system design, EQ, signal shaping, etc. There is harmonic distortion. There are non harmonic distortions and noises: Air noise through the motor, port noise, cabinet buzzes or rattles, driver related taps or ticks or other mechanical sounds, objects buzzing or rattling in the environment etc. These types of noises from the driver or cabinet may not show up in a frequency response or distortion measurement. Also the signal delivered to you not only needs to match the shape of the electrical signal but also the amplitude. Dynamic distortions occur too. Amplifier clipping, thermal compression, loss of driver linearity due to high excursion, rounding off or squashing the peaks of the signal, port compression, etc. Dynamic distortions are a big deal to me.
Invariably drivers more accurately reproduce the signal and behave better when driven at 10% than they do 50%. By the time they are being driven at 75% (Let's call this xmax and starting to get some heat buildup in the coil) they have degraded significantly. The last 25% to the limits of the driver (xmech, extremely non linear behavior at the extremes and significant thermal effects due to coil heating) result in exponentially worse reproduction. The closer the driver is to being pushed towards it's full operational envelope the less accurate it will be. You will see increases in virtually ALL of the types of distortion above and more. Having more total headroom available will make improvements in all of the above. If you need to EQ the system to reach the desired FR you need the headroom to comfortably do that. You need the headroom to maintain that response shape, limit thermal shifting and track the dynamics of the signal at any playback level you might use. IMO having an extremely powerful system is item #1 towards good sound. I'm also of the opinion that the various types of distortions, added all together, become audible as sound signature differences between systems, earlier than would be expected from just looking at one aspect or the other alone.
Item #2 is getting the room/space and system to work well together. Outdoors is one thing, but in a building...The amount of distortion imparted on the sound wave by the time it hits your ears, cannot be overstated. Once you have plenty of headroom to easily cover your listening needs and avoid dynamic tracking, thermal compression, harmonic distortion and operational noise issues...The next big hurdle will be the room acoustics.
On a related note to the discussion about those minor intangible things not captured in a sine wave sweep measurement...The program I use for the burst tests captures both the drive signal and the captured acoustic signal from the speaker. Ideally they would look identical. Of course they never do. Some look downright atrociously distorted while still passing the distortion thresholds as a "clean" pass result. If I get time I'll post some examples.
Wait a minute, are you saying the subjective and ambiguous term 'sound quality' can't be absolutely defined by a single number?!
Heresy!
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This took something like 12 to 14 hrs in a single day.
I was thinking when I looked at all the results that must have been a brutal day of testing or spread out over many days of testing. Heck, I think just testing all the modes of a variable tuned sub is a pain in the ass, and what you tested took many times that amount of work. I hope you wore sunscreen. Anyway, great job, and incredible sub. 130 dB at 30 Hz is insanity! bravo!
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I watched a movie recently that had some passages with lots of energy in single-digit frequencies: Hidden. An interesting little movie with some tense scenes. Here is a spectrograph taken at the 51 min mark:
My spectrogram only shows down to 10 Hz, but you can see there will be a lot of energy under that point.
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If we took a page from SVS's new marketing strategy we could list our HST and HS series drivers at 76 mm Xmax and 130 mm Xmech. I wonder how this forum and other forums would take that adjustment vs. what SVS has done? I could tell you but it would piss people off and start finger pointing towards us and not SVS.
Xmax is, has been, and always will be one-way linear excursion unless stated differently. Even then, stated differently is skating around the true meaning and definition of Xmax wether you adhere to 70% or 82% BL.
Agreed, SVS is inflating numbers with marketing gobbledygook. Still, even 41 mm and 32 mm xmax, which is what I take that they are implying, is not bad, but we don't know what they really mean by Xmax. What would be interesting is if someone took the driver out and measured its bare performance without the processing of their amp.
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It's in the owner's manual. It says overhung for both.
Huh, I have it directly from SVS that the PB16-Ultra uses a underhung design and the SB16-Ultra uses a overhung design. Also, that is a monster Xmax. If that is correct, I think the 16-Ultra subs will be a huge jump over the 13-Ultras in performance.
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Good questions!
Motor power is not really what the right factor it, its a contributor to the Q and its the Q that's what matters for system design. That's a big topic...
In general, underhung usually has less motor force, but not always. A lot of things can effect this. Another big topic, but the primary reason underhung cuts BL is because you're reducing the coil across the effective gap so you're leaving B directly uncoupling with wire at all times to create the xmax geometry. It is true as you reduce the size of the coil you reduce the relative Re so you also gain BL^2/Re that way, and you reduce moving mass too (but only a little). Those two things sound like a big gain, but generally not as much as the BL loss you already incurred. This is all of course assuming the same motor for both coils options.
Interesting stuff, thanks for the explanation, I will have to read up on this.
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Did you guys notice the PB16U driver has 41mm of Xmax when the SB16U's driver is only 32mm?
Why is the sealed version getting the lower Xmax and lower motor force driver? The ported one should be the one getting the lower excursion driver with the port managing the excursion levels down low. It doesn't need as much motor force either since the enclosure is so much bigger. The sealed version should be getting the ported driver. It needs that extra excursion and motor force in that little sealed enclosure.
Where did you get those Xmax numbers? I don't see them. All I can find is peak to peak.
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The PB16-Ultra is underhung and the SB16 is overhung. I thought that sealed designs have a greater need for motor strength than ported? And also that underhung motors tend to be not quite as powerful as overhung?
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I wonder if you can dim that thing or just turn it off!
Important stuff here!!!!
You can actually. It has adjustable brightness, and also an adjustable timer that turns it off after x many minutes.
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lol, you mean to tell me you're not caught up in how you like or dislike the front LCD panel like they are over on avs?
Unbelievable how picky some people are. Reminds me of this classic Louis CK bit.
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Maybe have the coil rest in some ultra-low viscosity, thermal-conducing fluid, sort of like Ferrofluid tweeters. What we need is Ferrofluid subwoofers!
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Those measurements look to be quite good. One unusual thing is they go out to 180 degrees off-axis instead of 90 degrees or so, that is a bit weird. That might be Harman's own measurements? They do 360 degrees by 10 degree intervals in their own anechoic chamber on both the horizontal and vertical plane.
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Here are a couple computer sound interfaces if anyone cares:
MOTU UltraLite mk3 Hybrid:
Behringer U-Phoria UM2:
Not bad for a $30 USB sound interface!
New SVS Ultra 16"
in Bass Gear
Posted
If you think the PB16 Ultra sounds bad, you are very lucky never to have been exposed to a truly bad subwoofer. The fundamental performance of it is pretty good, and it's amazing how much clean deep bass they manage to get out of a 15" driver. In conclusion, you are out of your mind.