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shadyJ

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Everything posted by shadyJ

  1. 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.
  2. I don't think anyone on this forum is in danger of buying some Beats headphones, but thanks for the heads up. I too would be looking at AKG, Sennheiser, JBL. I have some Denons at the moment that are quite good.
  3. It is sad that this subwoofer meant for recording is a much less linear device than many home audio subwoofers in its price range. You would expect the opposite to be true. It looks to me like it was meant to just plug and play with some active monitors, and was never really intended for a system with more than rudimentary bass management. It is only meant to give the low end of monitors some bass and who cares how accurate it is. I have to wonder how much prosumer gear is this mediocre.
  4. Magico already has their aluminum subwoofer. The cabinet is a 500 lbs aluminum block. Concrete wouldn't be 'exotic' enough. I am thinking.. marble. Make that sucker weigh a full ton. Say the marble has "micro-resonance diffusion properties" and charge $50k for one.
  5. Sure there are lots of speakers over 30k, but subs alone? Although I am sure any of these companies are willing to cook you up a super expensive sub if you asked.
  6. I don't know of a more expensive subwoofer than that Magico sub. There is the Wilson Thor's Hammer, but that is only $25k. What other subs cost north of 30k? That can't be a long list.
  7. There aren't too many subs that cost over 30k. The only one I can think of off the top of my head is the Magico one that uses two Aurasound NS18 drivers. I wonder which sub you are referring to?
  8. shadyJ

    B&C 21DS115

    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.
  9. shadyJ

    B&C 21DS115

    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.
  10. shadyJ

    B&C 21DS115

    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.
  11. shadyJ

    B&C 21DS115

    Wait a minute, are you saying the subjective and ambiguous term 'sound quality' can't be absolutely defined by a single number?! Heresy!
  12. 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!
  13. 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.
  14. I think that your understanding here is largely correct. But what will cause the most distortion is the room itself, ie linear distortion of the frequency response. The audibility of THD is not much compared to what the room acoustics do to the response. I would say yes, its good to do overkill with the subs, but take measures to achieve a flat response as well. In fact, you might want three subs instead of two. I would rather have three 15"s than two 18"s, since the former will go further towards getting a flat response (so long as the subwoofers are intelligently placed).
  15. IMD in subwoofers has not been the subject of extensive research, but Ed Mullen and Ilkka Rissanen did a study on it and found that the amount of IMD correlates to the amount of THD: the more THD there is, the more IMD. The obvious takeaway from this is that if one is concerned with IMD in subwoofer bands, then just get subs that are low in THD.
  16. I would say the difference between harmonic distortion (and also IMD) is that it is inevitable, unlike the types of distortion you listed (excepting compression). It will crop up no matter what, except if the driver is very underpowered. The other types of distortion, like cabinet vibrations, flutter noise, etc., may or may not be there in any significant amount. Harmonic distortion also gives one a good idea of when the cone is at the edge of linear excursion. For example, the CEA-2010 distortion thresholds seems to be more tied in with maximum linear excursion than it is with the audibility of distortion. The distortion of CEA-2010 thresholds are easily audible, but the subs don't usually have much left to give after surpassing those thresholds.
  17. From what I understand, PPSL designs can reduce even-order harmonic distortions. However, for all the sealed subs I have dealt with, the even-order harmonics weren't the worst offenders. Nonetheless, less distortion is better, so if one were to mount two drivers on a sealed enclosure, why wouldn't anyone want a PPSL design (aside for maybe aesthetic reasons)? Is there some other performance trade-off for PPSL designs? What is the catch?
  18. Yes. Near port tuning, the moving parts do not travel far, although there is great pressure on them. Since the moving parts are in the 'comfort zone' and well within linear travel, they do not generate much distortion. The further the moving parts (cone, voice coil, former) have to move, the more tension they put on the soft suspension parts, and the further away the voice coil gets from the magnetic field that it is designed to operate nicely in. That all adds up to distortion. In a sealed subwoofer, cone travel has to increase four times to achieve the same SPL for dropping one octave. That isn't the case at all with ported subwoofers.
  19. You are comparing the distortion of sealed subwoofers to a ported subwoofer, and that is an apples-to-oranges comparison. Sealed subwooofers will always have much more distortion at the lower frequencies. Another thing is you are using SVS subs to compare them against, and SVS is very strict with their limiters. Most manufacturers are more permissive of distortion quantities than SVS. If you placed a Ultimax 18 or SI18 driver in a ported box, you would very likely end up with less distortion for the same output level than SVS, so long as the ported enclosure is semi-competently designed and built. About the SI24 driver, in order to achieve that low distortion level, Josh used a very large cabinet: 43"x36"x23". If you can not handle a cabinet that large, you will have more low-end distortion. That said, the distortion measurements for the SI24 are really terrific, and, in that enclosure, do resemble that of a ported subwoofer.
  20. shadyJ

    v2 update

    Loves my shooters. Looking forward to hearing about this new project!
  21. I don't think the rotary subs are able to be comparatively measured against other subwoofers since they are basically home installations. It would be interesting to see what they can do though, even if in-room.
  22. That is really cool stuff, thanks for sharing! I'm not sure if you are interested, but THE classic text on audiology can be read here: On the Sensations of Tone by Helmholtz. A few of the pages are a bit garbled but it is very interesting to look through nonetheless.
  23. As I recall, the original study saw temporary threshold shifts for exposure to loud bass. The type of threshold shifts that they saw makes it easier for upper frequency sound to cause permanent threshold shifts. The researchers also speculated in the conclusion that exposure to loud bass may also be able to cause permanent threshold shifts in its own. The takeaway for me is that loud bass is not as harmless as some bass heads have claimed in the past.
  24. Here is a very interesting survey of the perception of infrasonic frequencies: Hearing at low and infrasonic frequencies Yes, people do hear below 20 Hz, well below 20 Hz, and yes, hearing is the operative word, not tactile skin body sensations. One other article I will link to later (I have to run right now), a study that suggests that, despite bass aficionado claims, bass can actually contribute to hearing loss. EDIT: here is the article on how low frequency sound can damage your hearing. Bass enthusiasts always thought that bass was harmless, and, while it may not be as harmful as frequencies we are most sensitive too, it turns out not to be true that it has no effect on your long term hearing.
  25. 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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