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  1. Today
  2. KRK Systems 12S2

    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.
  3. Yesterday
  4. KRK Systems 12S2

    All discussion of this 12" commercial unit and its measurements should go here. Thanks.
  5. The Data-Bass Member Equipment List

    A new addition for my space, Nathan's new 21.0LX, based on the UH21 driver.
  6. Bulding the Room2 listening room

    Just wanted to mention a side-effect of having a true full-range system, something the typical data-bass reader can relate to; You sit down in the carefully located listening chair, put on some quite ordinary music - jazz with vocal, acoustic instruments, perhaps some classical with a small string quartet ensemble. Sounds nice, the ears warm up a little, and you increase the volume slightly, usually end up keeping it at 0dB. Then - suddenly, out of nowhere, this string quartet makes the whole world kind of shift as a very powerful pulse of ulf noise makes your heart stop. You don't really hear it, you feel the air blast and the movement . Like in a well-done action movie - except that in the movie, it is expected, appropriate and part of what makes the experience better - and you are don't get scared. It is obvious that not only movie production studios lack low frequency reproduction capability, music studios have the same limitations, and they don't need it either for the string quartet. Except when someone stomps the floor, or touches the microphone housing, and a microphone picks up this and creates an earthquake on the sound track. If the recording is processed full-range, and no one checks for sub-20hz noise using a spectrum analyzer, this will go unnoticed. Until I play it on my system. At 0dB. Lots of recordings have ulf noise that is audible, and some have these occasional potential heart-attack inducing monster transients.
  7. Last week
  8. Questions about othorn,keystone, Xoc1 th18, DSL118 and others

    Here they are!
  9. Ricci's Skhorn Subwoofer & Files

    I am running with one vent blocked. Getting good extension to 20hz in my room. Haven't tried with two blocked yet.
  10. JTR Speakers Captivator 212Pro Discussion

    Cone flexure occurs at lower drive levels too, but it should remain linear at low drive levels. Many materials with elastic properties (metals, polymers, composites) exhibit some mild non-linearity at higher stresses, but this should manifest as a gradual increase in distortion with drive level. Where the stress-strain relationship changes abruptly, the material is usually permanently damaged. This is could involve elastic deformation (i.e., bending of metal, which does not return to its original shape afterwards) or fracture. You say that the driver is not hitting suspension limits, but if it's being pushed "close to Xmax", maybe it actually is, even if you don't expect that it is based on simulation data. Let me suggest a mechanism for why this could occur even if one believes the driver is being operated within its limits. More typically, driver excursion is only high at low frequencies. At frequencies well below resonance, the motor force primarily acts in the direction of the driver motion and is primarily opposed by the suspension (including box air spring, in a sealed box). When pushed to the extremes, the drop off in motor force tends to limit the excursion vs. power applied. In contrast, at high frequencies the motor force acts opposite to the direction of driver motion. It acts in conjunction with the suspension forces to slow the driver down and reverse its motion. As excursion increases and BL drops, this part of the opposing force also drops, and depending on the suspension properties, the driver is likely to exhibit *more* excursion than expected for the power input. This does not mean that the output increases because output depends on acceleration, not excursion. Physically speaking, acceleration describes both rate of increase in velocity (positive) and rate of decrease in velocity (negative). Sound comes from oscillation (positive and negative) of the cone acceleration. So paradoxically, increased compression and distortion will be observed at the same time that excursion increases. At some point, the coil can literally fly out of the gap, and it's up to the suspension to restrain its motion, or else. It's likely at that point that the sound may abruptly change from mildly or moderately distorted to very heavily distorted. As I discussed in previous posts, if driven hard at resonance, it may exhibit very little distortion right up to the point that it suddenly bottoms (soft or hard). This occurs because at resonance, motor force has only minimal effect on the driver motion at its extremes, so any BL distortion may be inaudible even if the coil is flying out of the gap. This is especially true for high Qtc alignments.
  11. JTR Speakers Captivator 212Pro Discussion

    I think the noise we are hearing is a form of mechanical non harmonic noise. At the end of the stroke, in a well designed driver, the suspension has to stop the voice coil or any other part to hit another part of the driver. It is doing this by getting harder and harder to stretch until it stops completely. Before it does, some mechanical clipping noise can be heard but it's not really a square wave because the diaphragm is bending a little also at those displacements. In the image one can see what one Powersoft X8 channel can do to a pair of 18TBX100 drivers in an 340 BR enclosure where the maximum excursion allowed was 1.5 mm more than the maximum Klippel recommended protection of 15.4 mm, which is already 4.4 mm over XVar (50% KMS) and where the people using it completely neglected that powerful noise
  12. JTR Speakers Captivator 212Pro Discussion

    Those are different things. Breakup modes due to bending forces in the cone geometry and composition are basically resonances. These occur even at very low volumes and are a separate issue IMHO. Basically they are inherent to the driver. This is something that does not occur until the speaker is driven extremely hard. Usually harder than any user scenario would ever push it. If things are continually pushed harder and harder the forces on the speaker increase and eventually something will break or start to behave very badly. Have you ever looked at the forces involved to produce some of the burst output numbers recorded? Acceleration or velocity for example? The forces involved are way beyond the scope of normal use. Lighter more flexible materials will tend to give more. What happens to the mass at the edge of the cone when the voice coil acceleration at the center of the cone is constantly increased? I doubt it is IMD or flux modulation effects I just don't see them making the sorts of noises I've heard. In some examples a driver will go from producing a relatively clean pure sounding tone to a clearly mechanical almost bottoming out sound in the 63-125Hz bands with only a small increase in the input signal. However it is not actually bottoming out or hitting suspension limits and the amplifier is well below clipping. That is easily verified. The signal captured goes from a normal looking reproduction to a complete unnatural mess.
  13. I'm guessing someone will measure it 'officially' soon enough. Won't be me though. I've really cut back on my movie purchases this year (single income family situation), and I'm pretty sure this movie isn't worth my hard earned cash. It was funny reading the note that came with the theatrical distribution though. It gave explicit instructions of where the sound levels should be set (85dB reference). I asked the theater owner in my town is he followed it. He laughed and said 'no'. Smart man....... Judging by the previous movies and Bay's own penchant for excess I'm guessing the audio will be wall to wall racket with some heavy clipping. Look at the average on that graph. It's rare for it to get that close to the peak unless there's damn near constant bass.
  14. bmoney, I also heard it was awful. If you look, those numbers are for the first movie that was just called Transformers. That's why it says "it's a terrific film". This one is supposed to be horrible. I was just wondering if someone was going to put down measurements like they do for other films: Level: Extension: Dynamics: Execution You know, that kind of stuff. It is supposed to be really bad but it is a Transformer movie. But, if the audio is really good, then I might just get it for the visual and audio and hope the next ones are better. Sorry for the confusion.
  15. thats odd i heard although the movie terrible..i heard the audio was outstanding
  16. Has anyone done measurements and other tests that are done on this site for Transformers The Last Knight. I heard it was not good at all, but that chart does look pretty good. Hopefully it does not clip that much and I am wondering if I should pick it up just to complete the series. But you know I am looking for something like Transformers: Level: 4 Stars (111.57dB composite) Extension: 5 Stars (1Hz) Dynamics: 4 Stars (25.98dB) Execution: 4 Stars - This was a terrific film, and got many into the subwoofer realm because of Ironhide's flip. If it wasn't for a single effect, though, this would only be a 19Hz extension film, hence the 4 Star rating. The best part of this film is that most explosions that are wide bandwidth (and therefore do not contribute much to peak levels) extend down into the teens if not single digits, and it is easily palpable. And to know if it is clipped? Just wondering
  17. B&C 21DS115

    SO the first model is the 21DS115 vs SW152. It some areas the DS looks better. I pushed both to about 20mm but I was just doing a quick sim from what I had. Then I selected the lossey Le in Wizard and you can see the DS in black verse the Le in red. Not a huge difference but enough to make sure you simulate it is all. For me the DS115's are about the same price as the 18IPAL's. So thats why the DS's are very interesting. I am not ready to buy any more speakers for now since I still have to finish my Skhorn first. BUT I do want another pair of horns to build come January. I just keep forcing myself to make a reason to get the IPAL's.
  18. Questions about othorn,keystone, Xoc1 th18, DSL118 and others

    For me the option is the Alpine SWS 15 or 18IPAL. Amp wise I dont have an issue there because most amps can handle 2ohms. BUT when I find something I will build using the 18IPAL I am looking at just using a SP 4000 amp. PLUS I will be buying one for my Skhorn build anyways. Look to see real world how the IPAL does in the Xoc1 TH118. I dont have the plans on Toms design but dont mind building the clone.
  19. JTR Speakers Captivator 212Pro Discussion

    I kind of doubt it's cone flexure. That's what cone break-up is all about, which doesn't set in until much higher frequencies. As a guess, you could be encountering strong inductance or actual flux-modulation effects. Strong IM distortion may sound a bit like mechanical noise if it's bad enough. Being IM distortion, I guess it might not show up as THD, depending on the analysis being used.
  20. That looks pretty decent - 20Hz filter is better than a kick in the teeth and it may be a potential contender for BEQ...
  21. Questions about othorn,keystone, Xoc1 th18, DSL118 and others

    Oh, but they warrant the cost on their own. In anything you put them, that has increased performances. But only with the right amp. There's in fact the problem. Here we only have Powersoft amps that handle very low impedance and high reactivity subwoofers. SpeakerPower amps would be the others, but I can't really get my hands on them easily. Probably some Crests are also good and stable and also Crown amps. But not as good.
  22. JTR Speakers Captivator 212Pro Discussion

    I have a theory that some of the lighter cones start to flex due to extremely high forces placed on them during the burst testing. It is something I have noticed on those types of drivers over the years. At the 80 to 125Hz bands the driver may not be able to reach xmax or even the THD limitations for the testing before something starts to sound wrong. This will usually be noted as mechanical noise on the burst chart. I stop at that point because it is a clear indicator not to proceed further as damage may occur. It is just a theory and could be any number of things though. In this case it really doesn't matter that the cab wouldnt take more than 110v. It means a less powerful and costly amp can be used and get all of the available performance.
  23. Acoustics Studies

    He has some good articles on his site if some of you are unfamiliar with it.
  24. B&C 21DS115

    I woukd definitely use it when modeling any subwoofer. You have to remember that the final result will likely be a bit smoother due to losses and unaccounted for variations in the real speaker. I like to look at sims with and without both and make sure both look ok, but the LE model will be closer.
  25. JTR Speakers Captivator 212Pro Discussion

    A pair of 3" coils can handle as much power as a 6" coil. However, design goal was for max efficiency and output with 1200w (69v) which we need to add to the website (up to 1200w amplification).
  26. Questions about othorn,keystone, Xoc1 th18, DSL118 and others

    Will be interesting to see what your results are. I do like the IPAL but havent been able to make a design that warrants the extra cost yet.
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