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SME

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SME last won the day on April 13

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  1. Othorn - HT capable?

    To be clear, @lilmike 's horn designs appear to be very good. I just wanted to point out that there's a lot more to good sub performance and good integration than what type of alignment is used. As I detailed above, you might want experiment with different (higher) crossovers. You emphasized integration with the mains as a high priority, and I'm arguing that good integration with mains has more to do with working around room effects. I didn't explicitly mention it, but phase match between the mains and subs is also crucial. This is partly addressed by optimizing the sub delay, but that only insures a good match at one (usually the crossover) frequency. Phase match can be tricky to get right when the mains roll-off rapidly near the XO frequency as yours do. I believe front-loaded horns like your mains exhibit 24 dB/octave roll-off below their lower limit, similar to vented cabinets. A lot of people try to cross vented mains at least half-an-octave higher than the point that they roll-off. So for example, you might consider crossing at 90 Hz instead of at 62 Hz. I personally cross at 100 Hz, even though my vented mains are tuned to ~45 Hz, because anything lower than 100 Hz just sucks in my room. Yes. Sealed subs are expensive for the headroom. How horns factor in depends on how much it costs to build the cabinets. They are complex enough that they could be a substantial part of the overall cost. For home theater, I think flat response with strong output to 15 Hz is a good sweet spot, and it's not difficult to achieve in most instances. While 15-20 Hz is not as substantial as the content above 20 Hz, I believe it still contributes a lot. Below 15 Hz, returns diminish rapidly as price and/or complexity also rises rapidly. Below 10 Hz seems to be hit or miss as perception of that content seems to primarily depend on how the floor responds. A 20 Hz TH can maybe make some sound at 15 Hz, but it won't play flat to 15 Hz unless your room has a big bump there. A 25 Hz horn has no business even trying. Keep in mind that unlike FLHs like the F20, a TH *requires* a high pass filter to protect it from unloading and avoid heavy distortion and/or permanent damage.
  2. Thanks for the offer, but it'll be some time before I'm ready to do serious testing on other systems, at which point I'll need to be present to listen to the results myself. Of course, if I move to Europe or something, it could happen sooner. A flat in-room response will probably not give the best sound. At the very least, you'll probably want 5-6 dB of bass boost centered around 80-160 Hz. You may also want a more gradual slope (i.e. 1 dB/octave) a ways above and below that point. Feel free to experiment, of course. I'm not aware of any online samples from Floyd Toole's book, but if you are curious, I highly recommend buying it. In my opinion, it's the best book on the subject of sound reproduction, particularly for small room systems. A lot of stuff in there seemed counter-intuitive to me when I first read about it, but my experience over time as led me to change my mind and conclude it was correct.
  3. Those look interesting. I'll definitely read them when I get the chance. The first article I opened (most popular) is dated 1998. Surprise surprise. This is hardly a "new" problem. The latest edition of Floyd Toole's Sound Reproduction book also has an entire chapter dedicated to discussing cinema sound where he remarks about the 2 kHz knee among other issues. Toole is consulting with an industry group that has recently been studying the problem with the aim of eventually establishing new SMPTE standards to address the problems with the X-curve. Toole's and Harman's recommendation seems to be to calibrate smoothed in-room response to a target that looks more like the Harman curve was is optimized (at least in theory) for "anechoic flat" speaker response cinema rooms and listening distances. While I think this approach would lead to an incremental improvement, it's still less than ideal. For starters, when people talk about frequency response, they don't bother to specify *how* the response was smoothed and *what form* was smoothed. These details actually matter a lot as far as the end result is concerned. For starters, one can choose a smoothing kernel which can be a flat-top ("moving average"), which is easiest to implement. Or it might use some kind of curve, for example a gaussian, which provides a smoother looking end result. As for what form, one can smooth the magnitude, the power, log-magnitude (i.e. the dB value), or the complex amplitude (where magnitude and phase are treated together as a composite 2D value). Power smoothing yields results most consistent with RTA and other continuous averaging instruments. Complex smoothing is actually mathematically equivalent to frequency-dependent window (!). FWIW from my testing, REW appears to do log-magnitude smoothing with a kernel that's similar to a gaussian. While it makes the data look prettier, it has a substantial effect on the end product. Furthermore, I have 99.9% confidence in the fact that fitting in-room response to any kind of target (even a room variable target) is suboptimal. Smooth in-room response should never occur in practice where any reflections are present, which means that in the process of EQing in-room response to be smooth, one actually introduces harmful resonances. How ironic! While I am a ways away from definitely solving this problem, I get the feeling I'm further along than anyone else at this point. It sure sounds like it.
  4. Othorn - HT capable?

    As I said, the question of whether horn subs have a "unique sound" that can be heard indoors is debated. Actually, that discussion assumes quality drivers and a competent build to begin with. Ideally, a sub shouldn't have a distinct sound at all beyond that which can be adjusted using EQ, but it's not hard to get a distinct (bad) sound from a sub that's poorly designed or poorly built. That goes for sealed, vented, and horn subs alike. As for what integrates best with your horn speakers, the question of sound characteristic is not especially relevant here. The sound depends far more on the effects of the room on the chosen placements for the sub(s) and listeners, any EQ or crossovers that are used, and the linear response of the sub at its upper limits. As I said, horn subs have more limited upper frequency capability, which makes them less flexible in small rooms. This means that you may be able to achieve better integration with the mains by *not* using a horn sub. It's really a minor thing, but I believe it's a lot more important than sound characteristic. In terms of sub design choice, the relevant questions are how much SPL you want with what kind of extension, how much space you have, how much effort you are willing to put into the build, and much money you are willing to spend. A pair of decent sealed 18"+ subs will give you plenty of SPL and extension for the modest listening levels you indicated. It seems to me that you've already made up your mind that horns are the only way to go. If so, then there's likely nothing any of us can say to convince you otherwise. And to be fair, you'll probably do just fine with horn subs like the F20. However, if you are serious about getting best integration with the mains or with choosing a design that fulfills your needs while better fitting your budget for money and space, you should definitely consider other design types. FWIW, I'm running 4 x high performance sealed 21" cabinets which get pushed to 125-130 dB from time to time. I chose them because I was space constrained, wanted a lot of extension, and was willing to spend the money.
  5. Sadly, even a cinema that's "designed, implemented and maintained properly", seems to be a rare occurrence. While my memory may not be completely reliable, my impression is that cinema sound quality (at least here in the States) has trended worse over time. I recall being fairly impressed by new cinemas built in the 90s and early '00s, but newly built/renovated cinemas I've heard in the last few years since are meh at best. I believe a big part of the issue is the X-curve calibration standard and a shift toward stricter adherence to the target. The standard actually allows for a +/- 3 dB deviation, which gives a lot of leeway to a calibrator to allow more bass and treble and to smoother the knee at 2 kHz, all while remaining "compliant" with the standard. However, I suspect this kind of manual tweaking is not done much anymore as cinemas cut labor costs associated with setup and maintenance including calibration work. Many cinemas are probably calibrated entirely automatically. I'm not opposed to automation when it actually works, but for audio calibration, current technology is not up to the task. I'm trying to change the situation by working on better technology. I have a very novel approach that is showing enormous promise, but it'll probably be at least a year before I can test it outside my own room. It also remains to be seen how much tweaking it will need to work robustly in a variety of different rooms. I do have confidence that I could eventually adapt it to work in all kinds of rooms, which would be very exciting. Then the challenge would be to get the industry to actually update their standards, but in the meantime, it could probably be marketed to cinemas directly where it could provide substantial SQ improvements via download-able X-curve re-EQ meta-data.
  6. Inductance modelling

    IIRC, WT2 exports to ZMA, which REW can import. I just tried it on one of my saved measurements, but I can't make REW calculate the parameters because all I have is an impedance measurement of the driver in the box. To calculate the inductance parameters, it must also calculate the rest of the T/S parameters which requires a free-air baseline and another measurement with added mass or in a test box of known volume.
  7. You have a point. When I said "unfiltered", I left it vague. The context was ULF, which could be informally taken to be under 20 Hz. Extension under 20 Hz seems to be pretty rare these days, but there is a decent amount of stuff that reaches to 20 Hz or 25 Hz, as you pointed out. Of course studios have no obligation to deliver audio that's flat to DC (or 3 Hz?). Though it's nice when it happens. I wish they'd do it more often, for the tactile transducer users among other reasons. I know a number of cinemas have transducers now. Although they may be mainly of the "shaker" type with poor extension.
  8. X-curve compensation re-EQ

    It's going to be a while before I do any more work here as I am *still* working on perfecting my system. My new calibration approach is much superior to the old, but I don't have a well-defined systematic approach yet. Different modifications lead to different different sounds, and I've listened to enough variations and developed enough intuitive awareness to know that I'm still not quite there. I'm getting very close though. It's getting better with each iteration. The detail I'm hearing in music is just crazy, to the point that many albums sound almost unfamiliar despite having listened to them on a variety of systems for years. I'm also leaning more toward waiting until I can make on-the-fly EQ adjustments before trying to do this. It's just very hard to evaluate changes with 30 second gaps in between and very time consuming to iterate repeatedly. I do want to make an interesting note. A couple weeks ago, I watched the BD re-release of "Monsters Inc". We started with 3D, which was fun until the PS3 choked (sadly, it has issues reading some discs), and because the PS3 doesn't deliver a TrueHD soundtrack and 3D together, I listened to the included 5.1 track. After switching to the other BD player (no 3D) to play the rest of the movie, I opted to continue the film with the 7.1 mix instead. The 7.1 mix was very different, and not just in terms of surround use. It was louder, and had quite a bit more mid-bass and treble (too much in both instances, IMO); whereas, the 5.1 had a bit of upper mid push. I'm fairly certain the 5.1 was a home mix with re-EQ. I'm not sure if the 7.1 was re-EQed from cinema or not. In any case, both my wife and I thought the 5.1 mix sounded better. The one benefit of the 7.1 mix was a bit more top end extension, but treble was definitely too hot. The 5.1 sounded more dynamic, had much better slam (by virtue of the mid-bass being better balanced with the low mids), and rendered ambiance much more faithfully. (FWIW, my experience is that the quality of ambiance rendering is a *major* clue as to overall tonal balance and sound quality!) Considering that ambiance is a *big* part of the appeal of surround, the 7.1 mix was quite a let down, IMO. By pulling back the upper mid just a hair, the 5.1 likely would have be nearly perfect. So if anyone wonders whether EQ is applied during home remixing, the answer is yes, at least sometimes. If anyone gets bored and wants to compare the 5.1 and 7.1 on "Monsters Inc", I'd be curious about others' impressions, but it's not a big deal.
  9. You'll be surprised once in a while. Some TV shows do have some good ULF, albeit it can be spotty and inconsistent sometimes, and it's rarely as loud (relative to the dialog) as in movies.
  10. I can agree to your first statements, but I'm confused by what you mean in bold here. Do you mean to say that there are many more unfiltered movies than it appears because many movies are not measured here? Yes, good surround mixing is a big plus too, as well as is overall better tonal balance, which also has a big impact on the perception of both bass and ambiance.
  11. I think "How to Train Your Dragon" should be near the top of the list for ULF as well, and it's also a pretty good movie if you like family / animation. Some would argue it's tilted toward the bottom a bit too much. The movie is full of ULF, but one noteworthy scene is maybe 1/3 of the way through in a large hall with a lot of thunder and a big door slam. That door really gets the air moving and is very noticeable because it is an isolated effect. Another animated movie with great overall bass and plenty of ULF is "9". It has many good effects. Among my favorites are the scene about 1/4 of the way through which bombs being dropped and huge mecha stomping around. A good one-off effect is the firing of the artillery near the end. The Dolby Atmos trailers I'm familiar with don't have a lot of ULF, but there are a few minor moments. In "Amaze", the "thundering bass" scene has some 14 Hz. I think it also has some 16 Hz at the very end. IIRC the leaf demo also has some 16 Hz at the end but nothing else. The "Horizon" demo has a few moments with moderate ULF, but it's completely inconsistent. The "Unfold" demo actually has good extension but isn't especially loud. Unfortunately, the trend with newer movies seems to be more filtering. A handful of us are able to work around this issue by re-EQing the soundtrack before bass management. Other than "Hacksaw Ridge", another recent Atmos mix that has ULF is "Wonder Woman". Even though most of the content is above 20 Hz, there's enough below 20 Hz to matter and the bass overall is top notch IMO.
  12. Woofer for 40-250Hz?

    You might reconsider talking to AE. They claim to have shorter lead times than they used to. The TD15H mounting depth is 8" and does not require any clearance for vents. The TD18 is 10". The website says they have TD18H-8ohm ready for immediate shipment. Too bad you probably prefer 4 ohm (?)
  13. Woofer for 40-250Hz?

    I wouldn't worry. I think the torture test would be to put on a concert BD with heavy mid-bass, crank it up to "call-the-cops" level for a few songs in a row, and then immediately due a sine sweep measurement. Compare to a measurement when cold. I bet you won't see any compression at all. I've done the same sort of test with my TD12Ms, albeit with them crossed at 100 Hz but nevertheless driven hard enough by kick drum and electric bass to average several watts and repeatedly hit RMS peaks in the 50-100 W range. Right afterwards, I touch the phase plug where most of the heat is radiated from, and it's completely cold. They are rated at 500W RMS, so I shouldn't be surprised.
  14. Sundown ZV4 18D2 - sealed enclosure

    If you can, just measure one channel at a time, like the center, but with all the crossover(s) and subs active.
  15. Sundown ZV4 18D2 - sealed enclosure

    Are you not able to remove the driver? Most of us glue the cabinet completely before stuffing it and only install the driver at the end. If something need to be changed, then we'll remove and reinstall the driver. If the enclosure was leaky, I don't think you would know for sure if there was enough stuffing. However, I think you'll be fine with what you show in your picture, plus "a bit more". Then you may want to cross a bit above there, like 45-50 Hz so that the overlap is better. You can use the physical length of the horn as a starting point. Are your mains processed by the same electronics as the different subs are? Electronics can add delay too. Either way, for the best performance, you'll want to measure frequency response with different delays and choose the one that gives you the most / smoothest output.
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