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I probably will give one an AVSForum BEQ try at some point. I just need to take the time to pick a movie I own (and have already seen) that needs BEQ, and see if the BEQ looks like something that won't obviously overload my system. It'd be nice to know which ones are the better ones, so I don't waste my time with mediocre stuff. This isn't just a matter of quality of the BEQ of course, because many soundtracks simply can't be improved much. Some day I may make my own BEQs, but I don't have the equipment I need for it right now and it's a lower priority than so many other things. I do want to say that I appreciate what @3ll3d00d has done with the software, which is definitely helpful to anyone doing BEQs. My preference isn't about levels per se. It's about balance. And in so far as I do give more "weight" to low/mid bass vs. ULF, it's because the former is much more audibly important than the latter. In fact, I'd also give more "weight" to bass above 100 Hz than to the sub region for the same reason. I'd argue that about half the tactile sensation of bass comes from frequencies above 100 Hz. This became much more apparent to me when I upgraded from my Hsu subs to my D.O. Funk subs. I have 4 x 21" sealed and a quite generous house curve, and the stuff below 30 Hz is completely different. On those Hsu subs, Kong SI would have been like a wild ride with lots of shaking and loud bass. On my current system, it was kind of meh, even though I probably pushed past 120 dB SPL on some of the bigger effects. When I got these subs up, I was confused and frustrated that I could hardly hear them at SPLs that would bring the house down with the old subs. Fortunately, I've got lots of headroom (~130 dB SPL for 20-70 Hz) and have figured out how to get great sound in the mid-bass and up. This makes me wonder about very near-field (VNF) subs. One side-effect of placing the sub very close is that the distortion performance is a lot closer to what one measures outdoors. That's because room gain is basically removed from the picture. So even if a VNF a sub is low-passed to only handle ULF, it will still produce quite a bit of higher frequency content and do so in a way that's largely free from room influence. To get back to the part about balance. In my opinion a lot of the problem is that mixes are being done with bottom heavy spectral balance. Generally speaking, the more bottom heavy the spectral balance, the lower a HPF has to be to avoid audible ringing. The idea is that the HPF has to be low enough for the ringing to be beyond perceptual thresholds. Most music isn't as bottom heavy, so the typical filter at 30 or 40 Hz isn't too big of a deal. (Sometimes it is though, on bottom heavy music mixes!) When there's a steep bass ramp in the spectral balance, one needs a lot more extension to avoid ringing. There's no way around it. Cool yeah. Wasn't the latest Mission Impossible also extended? I have high hopes for Aquaman and Mortal Engines. :) Disney lately seems to be rather consistent as far as filtering around 25-30 Hz. And of course the "dynamics management" (or whatever Disney does) has messed up some recent Marvel films rather badly.

Making the vents longer will lower the tuning. The rough scaling is square-root of 1 divided by length. So increasing the length will counteract the effect of making the vent wider. I doubt you'd be making them 1.4 times as long though, so its effect will probably be less than from widening the ports. My guess is that shifting the tune up 1/4 octave or less around 30 Hz won't be noticeable most of the time, but I'm sure counterexamples can be found. For example music with strong sustained tones at 27 Hz or something are probably going to sound quite a bit different. I guess that could be a thing with some music genres. On the plus side, I reckon the wider ports will give you another dB or so of low-end output without port compression.

Assuming I understand the dimensional drawing, the ports are 3" (76 mm) wide, so adding 30 mm to each side would make the ports 140% bigger in cross-sectional area. Vent tuning frequency scales with square root of port area, so tune will be ~118% or around 1/4 octave higher. That's like 35 Hz vs. 30 Hz. This assumes a pure vented alignment, and I'm not sure how the 6th order aspect will come into play.

I don't think I'll have that problem when I get Atmos, being that both my BEQ and bass management processing are downstream from the Atmos processor. Or am I missing something? Everyone needs more DSP. I don't think reference really exists, at least in current practice. I think it's important to distinguish between hearing (1) what the director/mixer heard; (2) what the director/mixers *intended*, which is essentially what goes onto the track; and (3) what the director/mixers would have done *if* they could accurately hear what they were doing. Ideally, we want to hear (3), but cinema monitoring systems are not really accurate at all, both because of flawed calibration standards and limited bandwidth. (A good home mix probably can close the gap wrt (3) quite a bit.) Achieving (1) is also impractical. We can try to get close, but should we? Some experimental evidence (i.e. blinded listener preference studies comparing cinema content with X-curve vs. neutral response in cinema) suggests that listeners prefer (2) over an approximation of (1). I spent at least a few months coming to similar conclusions. With that said, I believe BEQ is a kind of thing that ideally can get one closer to (3) also. The ULF content is intentional, not as an artifact but as an integral patr of the sound design. The filter(s) were also intentional, but the consequences of that filter were probably not what was anticipated. I see mixers often claim that they filter the soundtrack to remove content that they can't monitor. Logically, this seems like a sensible things to do, but it doesn't work that way. Sounds with ULF are almost always present with higher frequency content that is much more audible, so removing just the ULF doesn't really remove any unwanted sound. On the other hand, the filter *adds* ringing around the cut frequency, and unfortunately, this aspect of sound will not be rendered accurately by the monitoring system because it is likely already ringing in that area due to its limited bandwidth. Sure, the additional ringing introduced by the filter will be noticed, but it will difficult to impossible to assess how that filter sounds on another system. Even if "reference" is specified to be 30 Hz ported, different monitor subs will have different characteristics including different internal HPFs. So not only does the HPF largely fail to remove content that the mixers are unable to monitor, it actually adds content that the mixers can't adequately monitor. They can try to tweak the sound to balance the "deep bass" (30 Hz boom) with the rest of the spectrum, but what they hear is not likely to translate well at all vs. if they just left it alone. The only real argument in favor of HPF is for headroom, yet ... There is one subtle point I want to make about filters and where they are introduced. A lot of filtering may be happening implicitly, as a built-in function of the sound and/or subharmonic synthesizer(s) being used. This is one of those things that may be enabled and set by default in the software packages being used for this stuff. So the filtering could be "part of the sound design" in that sense, being that it was never actually heard without the filter. Of course, it also likely never gets heard by either sound designers, director, or mixers on a full-band bass system anyway. So again we go back to whether the unfiltered reproduction is likely to be preferred by the creators if their monitors were faithful. My guess is that no-filter would win almost every time. (To be clear, some broad stroke EQ may be an essential part of the creation, but a high pass or steep shelf below a fixed frequency like 30 Hz is much less likely to be part of that essential character.) I appreciate everything you do either way, and prefer quality over quantity any day. Per above, a lot of films may not BEQ well if the filtering is happening in the sound design. Different sounds might come from different synth software/plugins with different default filter settings. A lot of these are kinda weird and inconsistent even without BEQ. (I again note that filtering doesn't help with this nearly as much as mixers seem to assume.)

There's no question that the BEQs posted to AVSForum cover a wide range of content, which also includes films that IMO didn't need them to begin with. I have a few reasons for being less than enthusiastic about them. For one, headroom requirements are a total unknown, and many appear very aggressive and likely to overload my system. For another, I strongly believe "first, do no harm" as far as the soundtrack is concerned. Ideally, filters of any kind should only be used when they are fundamentally part of the sound. The point of the BEQ, IMO, is to precisely reverse the degrading filters in place, which is not at all the same as making the PvA look perfectly smooth down to 5 Hz. Along these lines, the AVSForum BEQs appear to be to have been EQed quite aggressively for a straighter/smoother, and I strongly suspect that this has degrading consequences. People forget that the PvA data is aggregated and often reflects the contribution of many different effects which may only appear smooth "on average". So trying to make it look perfectly smooth, especially using peaking filters, is likely to screw up the sound. Related to this is the fact that the BEQs are usually made based on a sum of channels PvA, and many mixes have very different PvAs for each channel. I think only a couple BEQs posted here specify the same filters on all channels. The issue with doing this is that it won't really "correct" anything at all. Every channel will be wrong in a different way. Each is likely to come with new resonances that weren't on the soundtrack before. I don't want new resonances. The main reason I like BEQ is because it gets rid of the annoying resonance at the filter cut-off. The experience with a truly neutral bass spectrum is simply marvelous. Transient response is impeccable, and the bass delivered is simultaneously tight and firm. It moves the listener. Any resonances spoil that magic to a great extent. I also appreciate that @maxmercy does a kind of quality check and doesn't post BEQs that didn't improve anything. Very often the sound design just isn't good enough or consistent enough to make it worth it. Often the problem may be inconsistent use of filters in the sound design itself rather than anything to do with how the film is mixed. Related to this, it's possible for a mix to use dynamic filtering that respond to available headroom. Such a mix might be full-band for lower level sounds but cut off at 30 Hz for louder sounds. I suspect this may have been done in Jurassic World but don't know.

Sorry, I meant for "Kong". It's no big deal. I didn't really like the movie enough to buy it or watch it again.

Did that BEQ end up not being worth it? I just watched this finally. Even though the hump around 15 Hz doesn't look that bad, I noticed a lot of annoying rumbly overhang on effects. I think it was as annoying as the usual 30 Hz hump sound, just an octave lower. Perhaps with BEQ, the sound tightens up, or perhaps not. I think it needed more mid bass, and I'm not sure the sound design was all that great to begin with.

The 4th order HPF sounds pretty conservative. I do know that @deepthoughts reported that driver excursion can be unexpectedly high (vs. simulation) in ported alignments at levels that cause a lot of port compression. I guess the port, when it's compressing, is not providing enough loading on the driver. Port compression can also be difficult to see in measurements because the output from the driver itself increases, helping hide the drop in output of the port. I don't know enough about tapped horns to be able to guess whether something similar can happen due to losses in the expansion, but I'd expect it'd be less of a problem if it is at all.

I'm curious as to what you were thinking of. One dead simple idea is to just take the double driver Skhorn, cut it in half and add a 3/4" wall where the center used to be along with maybe some extra bracing. An additional idea would be to make mirrored pairs of these along with tensioning buckles or other hardware to bind a pair together into a temporary D.O. sub. You'd want some soft material between the cabinets so that they can be bound together tightly without any buzzing or rattling. So basically a pair would get you a Skhorn that you can more easily move as two separate parts. What's not to like? I think the hard part would be finding what kind of binding hardware works best. Something ratcheting might be a good idea. Maybe nylon strip like for tying down loads? Ideas...

Thanks for the links! I sent you a private message so you can let me know when I can start downloading the files for the 5.1 album, unless you mean to post it publicly. Congrats on finding a good deal on used gear! At least these looks like they can help bridge between your existing mains and any Othorns you choose to build. Best of luck with those, and happy stomping!

Any amount of slope is enough to provide some driver protection compared to no slope, but how much is needed for "bulletproof" operation depends on the design and also on where the filter cuts. This case being a horn, the unloading of the driver may result in a more dramatic increase in excursion than a typical vented alignment. That would definitely explain why a 4th order is needed.

It's basically a perceptual emphasis of frequencies in that area and possibly a bit of overhang to the sound, whenever the content goes that low. If the content is filtered a lot higher, like > 30 Hz as is typical for music, you probably won't hear much difference. So it's probably more a thing with movies that extend to at least 20-25 Hz.

What you say about the quality variation with psytrance is so true. It applies to the musical composition for sure, but it also seems to apply to the technical aspects of the sound, particularly with older stuff. This has become especially apparent to me during my recent listening. My favorite outdoor experiences were in California on Memorial Day weekends for a few years. For a while, the event fell right at the end of my finals week and was the perfect way to finish out the school year. After stomping through a legendary midnight-to-midnight set (with all one DJ) a good night's rest, and a generous morning breakfast, I always felt upbeat, physically rejuvenated, and clear minded for days or weeks afterwards. I'm not surprised that music like that Aussie track is difficult to get right. A whole lot of pro subs and systems roll off steeply at 40 Hz, and this may perceptually accentuate content around that frequency including contribution of some ringing overhang on transients. That could definitely cause unwanted boom or sloppiness on a track with the bassline fundamental right at 40 Hz. Having sub extension that goes well below that point is likely to help. I noticed significant lossy data compression artifacts with all three samples. I think there's a max quality that YouTube will provide, and it's still not that good. The algorithms struggle more with content that's harmonically complex like stuff that's heavy on noise and distortion. Psytrance seems to need higher bit-rates than many other genres to not cause artifacts. I agree a lot of content is highly compressed and/or has a top heavy spectrum. Both of these have been used in the mastering processing since at least the early '90s to make content sound louder. Pumping is also often introduced on purpose to get a certain kind of sound. Along those lines, I've read that aggressive compression has been used almost universally in psytrance to tightly integrate the kick and bass parts. I don't know if it's true but don't doubt it. I'm also OK with it because it's part of the sound I like. What I don't like is when the rest of the sound pumps from kick or bass. I find that real distracting unless it's like an isolated effect or something. When you talk about software synths, do you include software simulations of analog hardware under that designation? I know that in days bygone, the software simulations didn't do such a good job of imitating the real thing. On the other hand, I've heard some pretty nice sound out of simulations in recent years, particularly in the form of standalone hardware devices that nevertheless use software to simulate the analog sound. A good friend of mine has a collection of such devices and sends me music once in a while (experimental, mostly chip tune). It's always completely raw with no EQ or other processing. I've noticed that the bass instruments really slam nicely, which makes me think that the best bass is often that which is least altered from the source during the production process. I am using Audacity. It has a simple spectral analysis feature in which you select a snippet of audio and see basically an FFT of the snippet. It's a bit ugly, but provides useful information about the spectral characteristics of the content. I don't think the link you meant to post came through. Can you try again?

I did worry a bit that my suggestion would require processing you don't have. I kind of feel like we all could use a bit more audio processing (of the good kind) in our lives. I am an engineer, and I designed my own custom processing because I couldn't buy what I wanted. A 5.1 psytrance album? That sounds like something I'd love to hear. Can I buy it somewhere, on a DVD or as a download? Well first, I wouldn't really do anything different for psytrance vs. other genres. My specific focus would be on sound quality over quantity, call it semi-pro if you like. I'm thinking it'd do well for small churches, small cinemas, etc. in addition to stuff like you're doing. To be honest, my idea is far from fleshed out, in part because there are a lot of mundane considerations to settle: size, form factor, HF driver height, etc.. Lacking real world live sound experience means I don't have a good grasp of best practices for that kind of stuff. What I do have is strong theoretical knowledge and experience designing and building the system in my living room along with a kind of working hypothesis about what happens in larger rooms and outdoors. For mid and high frequencies, I am a big fan of the SEOS waveguide design, which provides highly consistent frequency response at multiple angles. This is a beneficial property in small rooms because it makes the reflections more similar to the direct sound. It seems logical that this property would also be excellent for covering a wide listening area like a dance floor. The pattern is nominally 90 degrees (i.e., -6 dB @ +/- 45 degrees), but sound really doesn't change much at steeper angles, it just kind of gets quieter. To my knowledge, the SEOS waveguide has not been used in a pro speaker design. This is probably because the waveguide is physically large relative to their low frequency limit and output capability. I don't think that would be a problem in this kind of application though. My home speakers use the 15" wide SEOS, but for this purpose, I would probably go for the 24" wide. Forum member @lukeamdman used the 24" for his speakers. I'd probably use the same coaxial compression driver, the BMS 4594ND which contains two drivers in one package and extends up to and beyond 20 kHz. I'd probably cross it a bit higher than he did, at like 600-650 Hz, but the details would depend on what I used for the lower part and what the measurements looked like after I got the equipment. As for the lower part, I'm not sure what I'd do. I'd probably look at horn options for the bottom, but I don't know enough about horn design to know whether it's practical to cover a wide low frequency range, like e.g. 80 to 800 Hz without it being too large. I don't think a horn with folds would work. I would have to research it. One possibility that puts the HF driver at ear level (maybe much too low?) is to use a 2x2 array of 12" drivers, probably in sealed cabinets. The array would be adjacent to the ground and would couple well with it. The 4 x 12"s would have lots of headroom too. A single 18" or 21" would probably save some money, but not many drivers that big play well up to the c rossover. And furthermore, I think I'd want more headroom than a single 18" offers, which complicates the design in ways I don't like. As for whether to do sealed or reflex, it would really depend on the driver and what my low frequency needs were. Sealed is smaller and simpler and more likely to work with Skhorns that go higher. Reflex is larger but can play lower to mate with Othorns. It's not that simple though. I'd really need to look at different drivers, do simulations, etc. to reach a decision. Finally there is the processing. At the least, some high-shelf EQ is needed to correct the downward tilt in the treble which naturally occurs, in addition to crossover filters. The SEOS doesn't need as much boost to the top as some horns do though. In my case, I have my own processing and I have been working on novel methods for speaker sound quality optimization. I would use that to get the best possible sound out of the whole system. I don't actually have all this processing capability yet. My home system is the prototype, which I'm still working on perfecting before I move to testing on other systems and rooms. Like I said this project is basically fantasy right now, but if it were to happen there's a chance of me getting to it in a couple years.

A steeper slope will ring more. This is likely to be noticed much more with movies because most music is filtered higher up.

They are boosted to be flat (or rather optimized to target response) to about 6 Hz. I'm not sure how to answer your second question. The living room is open to the rest of a modest sized 3 bedroom ranch. If I only include the commons areas, which are connected by large openings, I'm at around 45 m^2, all with 8 foot (2.44 m) ceiling. It's probably a good idea, even though you may not play them hard enough for it to matter. A 48 dB/octave filter is extreme though. You can probably get away with like 12 or 18 dB/octave. I suggest going back and look at what's recommended on the build thread. The filter is probably a lot more important for movies than for music being that movies are more likely to have < 20 Hz content and at a high enough level to be a potential problem. That RP1 scene is pretty crazy, especially considering how long it lasts. Of course I'm running with BEQ, so no steep filter at 20 Hz. I don't know if that matters much though. Even if there is ULF, it seems to hit harder across the rest of the bass range. Going by my level indicator display, the effect seems to consist of a rapid, chaotic succession of short bursts that goes for several seconds. The voltage output peaks are pretty high, but it doesn't ever blink the yellow lights like King Kong does. Assuming it's mostly in the 20-60 Hz range, my subs probably aren't seeing much power there, but that suggests the SPL is pretty high, easily well into the 120s dB SPL.

Thanks for the music selections! I got seriously into the music around 2001 after Solipse Africa but kind of lost track of stuff after 2010 or so after it had splintered into so many directions. Your selections remind me a lot more of the sound of that era, though obviously these tracks are very recent. Here are some comments about my impressions of the sound of these tracks on my system: The Sentient track has a deep powerful sound, driven by a bassline with an unusually low fundamental frequency (39 Hz?). The bass rhythm is articulated very well, but sounds more smooth than punchy, probably on purpose. The kick has a strong treble bite, which I think emphasizes its bass contribution but gives it contrast. For both kick and bass, the upper bass / low-mid content is there but doesn't seem strong or composed enough to really "hit". For me, the melodic/atmospheric part of the sound is on even footing with the bass, although it sounds like it's a bit brighter than it needs to be. I find excess brightness in a lot of tracks that are sub heavy. I believe it's done to try to keep the sub sound from burying everything else. I like this song but would probably like it more with more mid-range. The African Jungle is my least favorite. The balance seems slanted towards upper mids and highs for a more aggressive sound, and the treble sounds harsh and distorted in a way I can't blame on YouTube. Both the kick and bassline are very prominent but neither seems that weighty. The articulation of the bassline rhythm seems to be dominated by upper mid and low treble. It's very tight sounding and has a strong tone, but I don't feel it at all. I feel a bit of 100 Hz ish resonance from the kick, but it's sloppy. To me the kick is more prominent than the bass, partly because I actually feel it, but also because it noticeably pumps the rest of the sound. The pumping makes the kick seem bigger than everything else, and I presume that was done on purpose. Apart from my complaints about the sound quality, the music is still fun --- just not as fun as the other two tracks. The X-Noize & Sonic Species track was definitely my favorite and was also the most tactile and punchy for me. It's a little bright and maybe bass shy, but that seemed to fit the uplifting "morning trance" mood of the song. Otherwise, I thought the balance was very good and conveyed the complicated oscillating synth effects real well. I was hearing and feeling them with clarity. I would say this is a great test track with because of the spectral variety. The trouble with testing audio performance using psytrance is that you often only get to hear what one note sounds like. () This track doesn't have that problem. My only want is for maybe a bit more overall bass power. Out of curiosity, I went and played some of my older stuff from like 2004 and earlier, and I noticed differences in tonal character compared to the tracks you posted above. For one thing, my older stuff doesn't seem as bright or hyped sounding in the highs. For another, the bass seems better. Even at fairly low levels, I can feel a warm, subtle "dun---da-da-dun---da-da-" in my core with a lot of them. Have you noticed any significant tonal differences between older vs. newer tracks? Perhaps the 100-500 Hz range is being suppressed in a lot of modern mixes in favor more more sub and treble. If that's the case, it's unfortunate because it's a lot harder to undo that kind of shaping with EQ during playback. Anyway that third track has a lot of effects similar to one which impressed me a lot when I first experienced it with really good bass. The version of the song I have is part of a mix by DJ Analog Duck in a Quizinart, but all I can find online is the original track. I think I liked the sound of the mixed version better, but anyway, near the beginning and the end there is a wonderful oscillating bass effect. I think it's a pitch that's warbling very slowly (over several seconds) from like 120 Hz down to 40 Hz and back that's been amplitude modulated using a 10 Hz square wave. It just sounds and feels amazing to me: This got me curious, so I went and peaked at the spectrum with Audacity which revealed a high-pass filter up at around 45 Hz and content going down to 10 Hz. Indeed, I'm now a bit curious as to what it sounds like with no filter and with reproduction all the way down to 10 Hz. If you really want to go nuts, trying building a pair of M.A.U.Ls which can go down to the low-teens outdoors. 😵 Or don't, being that subsonic content at a high enough level to matter is so rare in actual content. Almost every mastered recording gets a subsonic filter somewhere, usually at 30 Hz or above. I treasure the rare exceptions. Here's a track (not psytrance, but "bass music") with a little subsonic surprise, right at the beginning: The low bass note in the intro has a subharmonic that touches 16 Hz, just barely. (It's filtered below there.) The funkybassline through the rest of the track grooves around throughout the low 20s Hz. It's like the one track I have to prove that I can make "tight bass" at 20 Hz.

That's good! If you said you wanted it loud, I would have suggested higher SPL numbers. If it's very clean, then subwoofer bass is not really loud at all until the SPL gets crazy high. That 115 dB SPL is probably nowhere near as loud as you think it is, especially when you are outdoors. With that said, I did assume you might sometimes want to push the volume higher than usual for a short duration, maybe not for psytrance but for the climax of a live show or for genres with some macro-dynamic swings. The 115 dB SPL figure is for moderately compressed content (e.g., mostly analog) played at an average A-weighted level of around 85 dBA, which *is* on the loud side. A more reasonable level for up to a few hours is in the high 70s dBA. That's about where most music is mixed and mastered. For an all-day / all-night affair, you might want to aim for the low 70s dBA, which is healthier for the ears over the long-term and is easier to converse over, if that's important. Note that even 85 dBA is still pretty reasonable as far as live music events go (unfortunately, in my opinion). Even if you plan to stay in the low 70s dBA all the time, you may want the extra sub capability. First, your system will be spending most of its time > 10 dB below its capacity, which will help it sound its best. Second, it's nice to have more dynamics for live performances and live tracking where bass and kick can be mixed hotter than it would be on a record. This can give more impact without increasing loudness or compromising intelligibility of the rest of the mix. You're welcome! To be clear, my suggestion to delay the left and right channels only applies if you have a dedicated center channel. Otherwise, the left and right channels should be delayed relative to the sub so that the crossover response is accurate over as much of your listening area as possible. I'm also inclined to agree with @Ricci that it's better to cover that range with tops, if possible. I think sound quality and capability of the tops should be a key consideration when you upgrade them, and you would be amazed at how much even upper mids and treble affect how the "bass" sounds when it starts and stops. (Bass can start and stop 10X per second with psytrance. ) Unfortunately though, I don't know pro equipment well enough to give any specific brand or product recommendations. I can at least make educated guesses about what particular designs are capable of and what their strengths and weaknesses are. I designed, built, and optimized my own home audio speakers and would do not hesitate to the same for PAs if I needed some. I know I personally can probably get better sound quality that way. If you do opt to build dedicated mid-bass cabs, keep in mind that the type of cab may not be as important as where they are located. By moving 80-160 Hz to dedicated mid bass bins at the center, you are consolidating reproduction of that bass to a single source, which is beneficial in and of itself. You'll still have spatial variation and interference problems around the crossover at 160 Hz and above though. Furthermore by consolidating 80-160 Hz from both L and R and sending it to mid-bass bins at the center, you actually lose any out-of-phase content in that range. This may reduce warmth from stereo reverbration in those frequencies, especially outdoors where there is very little natural reverb. Another nice thing about the dedicated center channel for L+R is that the out-of-phase content still gets sent to L and R so you don't lose that warmth.

Mmm psytrance! It's been a long while since I've been to a party, but I listen to my fair share here and there. That trademark fast bassline requires good broadband performance to properly nail. A lot of bass sound/definition comes from the 200-500 Hz range, which also helps tighten the punch sensations. Even though the output requirement is not nearly as high above 180 Hz, you want good accuracy for the whole bass range if possible. At the same time, lots of psytrance goes to 30 Hz and below, so 30 Hz capability won't be wasted. How much SPL do you want? A lot of psytrance recordings are extremely bright, compressed and harsh to listen to at high level. I'd probably be happy with 115 dB RMS short-term (at the audience) in the sub region for that content. For stuff that's more dynamic including anything that's being tracked or performed live, I could see wanting 120 dB or more. At that point, it's really a matter of what you can afford and how tolerant your neighbors are. FWIW, these numbers are based on my preferences in my home but are probably a decent ballpark to aim for. Again this is for sub and requirements for higher frequencies are lower. I think the best choice for mid-bass augmentation depends substantially on the tops and on the overall system design. I would be very concerned about being able to integrate the different units while getting the best possible coverage. Using separate mid bass units gives you more headroom there but at the cost of another crossover at a higher frequency where interference can create new coverage problems. Have you considered using a dedicated center channel speaker? I don't know how well it would work, but for psy-trance I like the idea of extracting L+R and sending it to a dedicated center channel. If possible, I'd vertically stack the subs right next to the mid-bass units and put the center speaker a short distance in front of the stacks. After extraction, the L and R would mostly be surround/ambience, which is the other critical component of the psytrance sound. I'd consider adding enough delay to the L and R channels to ensure sounds always arrive from the center first no matter where you are on the floor. If you got it right, you would have superb top-to-bottom accuracy for L+R over a fairly wide coverage area. I realize this suggestion may be completely impractical, but most alternatives involve some kind of compromise. I do think your plan to go with 4 Othorns is reasonable for hitting the lower (115 dB) target. If more dynamics are desired, you might want more than the 4 Othorns. It's a shame the Skhorn doesn't work because its top end is a lot nicer. I think that would allow you to either forgo the mid-bass capability or mate with something that goes higher than 200 Hz. Anyway, your project sounds like a lot of fun. I have a kind of fantasy of building a couple SKhorn's specifically for psytrance in the Denver area, even though I'm not currently involved in live sound. Most of my interest has been in home audio, which comes with a very different set of challenges.

Interesting. Does the AVR do bass management on those channels or just pass the content through? Or can one choose between "small"/"large" to enable/disable bass management for Atmos speakers? It'd be weird if they just let the content go through. I'm sure that'd cause a lot of distortion, wouldn't it? I hope they at least provide the "large" option being that all my bass management is done downstream of the AVR with the matrix processing to optimize the crossover EQ and delay of each channel across the available subs. I'll also be feeling the pain of only 16 output channels on my 16A if I push to Atmos. My front stage speakers are 2-way active, and I am using 4 different sub channels. I'm thinking I may end up doing 7.x.2 with 6 outputs used for the fronts, 4 used for the surrounds, 2 for the ceiling speakers, 3 sub channels and 1 channel for the Crowson. That's a painful compromise to make. At least I don't need 4 ceiling speakers. It just doesn't work with the room, and with only one row of seats and the quality of phantom imaging I am able to get after optimization, 7.x.2 will probably be great. Thanks, but my point was actually that I *can* compromise deeper extension, and I want to because that's the only way to really get the most efficiency in the upper bass / low mid frequencies where I typically need headroom for EQ boost. These speakers go up near the ceiling, which provides a lot of extra boundary gain below the suckouts. All of my speakers, which are placed near walls, are EQed down quite a bit below 120-150 Hz or so. I don't like spending $$$ on amp power, so I want a coaxial with high efficiency, low mass, and moderate displacement capability. Most coaxials are designed to be used as full-range speakers, and therefore give up efficiency for extra displacement and/or bass extension that I don't need. Some others are strictly mid-range drivers and don't have enough displacement. The T/S specs on that 15" look real nice. AVSForum appears to be broken for me ATM. OTOH, I was looking at a 10" with similar efficiency, albeit less extension. I think it was the B&C 10CXN64. Hopefully I'll be able to find someone who sells it when the time comes.

Small speakers have come a long way, especially with regard to bass performance. I believe the Apple Homepod offers usable extension in a residential room to 35 Hz or so, especially if it's near a corner. The servo-controlled (IIRC) internal woofer probably doesn't compress much at all unless the volume limits are being approached, which probably aren't that high. (A lot of small speakers adjust the EQ with the volume control or may rely on some kind of bass-selective compression to allow louder sound without overloading on bass). The Homepod won't play the lowest bass that loud, but a lot of customers are OK with that. To be clear, I'm not endorsing Apple or the Homepod product, which I've never even listened to myself. I just want to point out what's technically possible with current technology (and big R&D budgets). My opinion is that a great speaker can be made very small, but where size ultimately comes into play is how loud the bass gets. Furthermore, this trade-off can be partially mitigated by spending a lot more money. This assumes active designs. In passive speakers, good bass extension from a small space requires severe compromise, usually poor woofer efficiency. Poor efficiency means a lot more power is being drawn from the amp and dissipated in the coils (and maybe crossover) for the crucial 100-400 Hz range, just so that the speaker can be "flat to 45 Hz". You said the F2 extends to 60 Hz, which means it's not only using a larger woofer but one that doesn't give up as much efficiency in order to play lower than it needs to. Another detail I think worth mentioning that I don't see in your write-up concerns speaker linear response and voicing decisions. Passive speaker designers rarely know where the speaker will be placed relative to room boundaries, except maybe the floor in a floor-standing design. Many designers likely voice their speakers with deficient 100-400 Hz output to try to accommodate being placed near walls or corners and also because resonances there can be quite offensive sounding. Resonances in this "mud range" can bury/swallow voices, so many designers probably err on sacrificing punch for clarity in poor placement scenarios. It is true that speakers with larger baffles/cabinets interact less with nearby room boundaries, often at the expense of worse baffle/cabinet diffraction effects. The size of woofer alone (assuming <= 12") has less effect on the radiation pattern than the baffle and cabinet at these frequencies. For wall/corner placements the benefit of increased directivity of a larger baffle and cabinet probably outweighs the increase in diffraction problems. Most of the above discussion may be rather moot with good in-room EQ optimization. I suspect that with good EQ optimization, differences in speaker size can be made largely irrelevant for low frequency sound quality at low levels. On the other hand, I've noticed that speakers placed near walls and corners almost always have a suck-out somewhere in that 100-400 Hz range, which needs EQ boost to compensate for. So at higher levels, capacity becomes an issue much sooner than without EQ. The bottleneck region ends up being 100-400 Hz, not < 100 Hz which I find usually needs cuts rather than boosts. So sadly, most passive consumer speaker designs sacrifice efficiency in the range that it's badly needed in return for bass extension that's not actually needed. To be fair, they are designed to work well when placed away from walls, but who really has room / spousal approval for that kind of thing? Not to mention how much better the sub bass is if reproduced from near a wall or corner. So as I see it, the discussion should be more about the merits of active designs in general (including any system using powered subs) along with in-room optimized EQ and based on high efficiency, low mass, pro-style drivers. Size does still matter, but for many listeners who only need low or moderate levels at home, a well designed active small speaker (with or without separate subs) can do the job very well. It's got to be active though. Really I think it's time for passives to just die, except in custom / specialty systems where there's likely to be some kind of active processing anyway.

Each cabinet has two subs in dual-opposed configuration, and I have two cabinets.

Wow! Those are a lot bigger than my D.O. 21" subs (800mm x 700m x 600mm). Now I want to know how big the MegaWrecker is. 😵

Dedicated subs for each Atmos output channel? That's pretty ambitious! I can't recall, but I thought Atmos heights were specified to be limited bandwidth? Assuming they were, I also don't recall if the bass management was supposed to be done by the playback processor, the authoring tools, or by the mixers themselves.

^ I almost wrote something very close to that. I used Festool equipment to build my speakers and subs, and its reliance on metric was a big plus for me to invest in it. I hate fractional inches and all the inane conversions of the Imperial system with a passion. While we're putting the Imperial system of unit to rest, can we also abolish Daylight Savings Time? It is a pointless bi-annual exercise that literally kills people, but it seems that the U.S. isn't the only country unable to wean itself away from this vestigial ritual. I must admit though that all this sounds like a lot of whining in light of current events in the UK, and I dare say things are looking a bit shaky in a number of other countries too.