SME

It looks like the amp and/or driver is completely out of gas below 16 Hz or so with the sweep at volume 70. What volume do you normally listen at and what level (dBFS) was the sweep at? You don't seem to be getting much room gain at all and may want to dial back the bottom-end boost a fair bit more to clean up the sound and avoid stressing the driver.

But do they repel spiders?!

I listened to the new Tool album on Friday night, but it was heard in the dining room quietly while friends played board games. The kick drum definitely rolled well on that album though. I think I'll listen with a friend at proper volume late next week.

Did ya put the other two Skrams in the rear corners of the room?

I think I may try re-doing the FOTP:EE comparison, maybe with proper A/B this time. This may sound wacky, but I discovered that the speaker terminals to both HF sections of my L and were bridged with spider webs. I am suspecting that problem may have contributed a skrunky sound to the very top-end, and the extra top-end in the BD version may have been reproduced badly and corrupted my judgment of the rest of the spectrum. I wish I'd known about SpeakOn before I built these speakers. I guess SpeakOn could be considered to be an audiophile accessory now.

And now for a random post about sound quality between home-remixes, specifically concerning "The Followship of the Ring: Extended Edition" on BD vs DVD. It's been years since I've watched the movie or even selections from it. I had kind of planned to play the whole trilogy after upgrading to a projector + screen, which still hasn't happened yet. But today I got the urge to run through some scenes to hear how it sounds on my current reference quality system. FOTR:EE in particular was a favorite of mine since it came out. So I did, and it was --- OK. So then I realized that I kept the DVD versions after reading here that the soundtracks may be different. Let me just say: Wow, what a difference! To be specific, I compared the BD with DTS-HD 6.1 vs. DVD DTS-ES 6.1 tracks back-to-back, using the Balrog scene starting back at "drums in the deep". A more fair comparison would use rapid A/B, but the differences were substantial enough that I'm confident in my conclusion without A/B. IMO, the DVD soundtrack is superior in every way. Both are mixed rather loud with clipping scattered throughout, but the BD is louder and the clipping much more apparent. The BD also seemed to have hyped treble vs. a much more natural (if still grainy, analog sound) in the DVD. The BD had plenty of boom and rumble from its 30-40 Hz emphasis, but the DVD revealed all that was lost from this treatment. While it was not clear whether the DVD had more extension than the BD (it certainly had *less* 30-40 Hz bass), the mid-bass on the DVD was far superior. Transient clarity was far better with a lot more detail experienced in the tactile dimension on almost all effects. This was especially apparent with the pieces of the bridge clashing together. Bass instruments in the score (drums, male vocals, low string notes, trombones, etc.) were both more tactile and had much more mid-range clarity. Even the dialog sounded better in the lows and mids. Clearly, the BD mixers were overconfident in the quality of their monitoring system and probably also naive as to the consequences of their changes. By the time Gandalf had been dragged into the underworld I was feeling annoyed and disenchanted with the BD sound and turned it off. On the DVD the sound compelled me to keep watching beyond that point. All this isn't to say that the DVD track is somehow flawless. I was actually surprised at how many problems I heard throughout, some of which were quite embarrassing. In hindsight, it's kind of remarkable that this was treated as a reference in its time. Even the score recording left a lot to be desired compared to music recordings going back decades. Either way though, the DVD is IMO a much better track, and if I ever watch these movies again, I'll be inclined to try to rip both discs and see if I can stitch together the DVD audio with the BD video. At least the BD video was mostly better, albeit with some de-saturation and greenish tint compared to the DVD (as reported in reviews at the time it came out). If they ever do a UHD release for LOTRs, I hope they throw out the BD audio and start with whatever they used for the DVD DTS-ES track. And of course, don't boost the bottom only to put a steep shelf or HPF at 20-30 Hz! We can always hope. Anyone else have both DVD and BD versions of LOTR:EE? Try the comparison (don't forget to select DTS-ES 6.1 on the DVD), and post your thoughts.

How boring! I wonder what my neighbors would think if I tried to do something like that? On the evening of July 4th and at Midnight on New Years, my neighbors shoot off fireworks. Those are louder than subs for sure, albeit for brief moments.

Thanks for the clarification. The obvious lesson here is that the worst-case scenario for long-term power with no ventilation is *very low*, and potentially lower than the numbers above because the calculator is very likely assuming free convection with an unlimited source of air at the given temperature. For those following along, free convention occurs when warmer, more buoyant air begins to rise and pulls cooler air in from the sides or below. Convection makes air cooling *much more effective* than it otherwise would be because *pure conduction in air is very poor*. This is something that occurs much more readily when there is room for the rising air column to develop sufficient velocity. A tiny sealed box fill with stuffing that increases air resistance, won't anywhere near as much convection compared to an open-air installation. I'm thinking the temperature monitoring may be a very good idea for subs used in pro settings with EDM with potentially high duty cycle signals near tune. One might need a lot more capacity than anticipated if reliable long-term operation at high levels is required. Another thing that could help would be to purposely tune a bit lower than the lowest anticipated content. A 30 Hz tune might be OK for music that's mostly 40 Hz and up, but stuff that hits at 30 Hz hard, it may not be a bad idea to tune a bit lower, to try to avoid the deadly combination of high level high duty cycle signals at minimum impedance and low excursion.

Do you know what assumptions are involved? Particularly concerning the air? The situation is very different if the air is stagnant than if it is allowed to convect freely. My guess is that a heat-sink calculator would assume free (natural) convection under some particular mounting configuration (say installed onto an infinite slab). A sealed box stuffed with insulation may not allow much if any natural convection, so the situation may be worse than this calculation suggests. On the up side, if the coil is mounted in very close physical proximity (on the order of one millimeter or less, by my rough calc) to other metal parts of the driver, enough heat could travel them through the air to make a difference.

That is most definitely key. If not just compensating for frequency response, I think you'd probably want a closed-loop system (i.e. servo), which depending on design can practically compensate for "everything at the same time". Well, that's still oversimplifying a bit. If you want to try to reduce high order distortion, you need a very tight loop, i.e. DSP that can respond with extremely low latency. OTOH, frequency response issues alone can be enormously important to sound quality. It's also hard to distinguish FR from (non-linear) distortion issues with listening tests because human perception is very non-linear. FR issues often do not become audible or annoying until one pushes the volume up high enough and may therefore be mistaken for non-linear distortion.

I meant it as more of a thought experiment, but if someone with the right amp wants to do it... Actually rather than doing 50W increments (which may be too big if the driver cooks at, say, 150W), a better idea might be to monitor the resistance of the coil in order to estimate likely thermal power compression at different true RMS levels and to inch closer to the actual limit.

Thanks for your input re humidity vs speaker parts. I don't see a rubber surround being too happy at -40 deg. Expensive how? A servo controlled woofer is likely to rely on (re)active DSP. The Apple HomePod uses a servo woofer in addition to adjusting its room EQ in realtime using data from built-in mics. I believe many cars already use active noise cancellation. Some cars also play fake engine noise through their speakers. I think Harley may do something like this on the outside for its European bikes, in order to provide a "Harley-like sound" while staying within EU noise restrictions. I could definitely implement reactive capabilities with my current PC-based DSP system, if there was a good justification for it. I live in a climate that has fairly large humidity fluctuations. It's reasonable to assume that indoor relative humidity will correlate with outside dew point temperature, given enough time for the air in the house to equalize. A/C usage is likely to affect things a bit too. I now casually monitor dew points published by NWS here. In the last week, I've seen multiple jumps from 58 deg F (14.5 deg C) to 28 deg F (-2 deg C) and back, each in less than 24 hours. Humidity changes have a very measurable effect on absorption in the air of ultra high frequencies. It's probably reasonable to assume that human listener adapt to these changes when listening to "normal sounds" but audio reproduction systems typically have flaws, and the humidity changes could affect the relative audibility of said flaws, leading to intermittent changes in apparent sound quality.

True RMS would be a very useful number to have from manufacturers, albeit still highly dependent on mounting and ventilation conditions. I wonder what happens if you take the driver with the highest rated power on the market (assuming it's not too exaggerated) and install it into a barely-big-enough box stuff with insulation. Then test it by passing DC current (so it doesn't move) for 2 hours on each power increment. How much power is that thing gonna take? Maybe we should pool together to buy one and take bets.

Definitely agree about not really knowing what to test in drivers. I think it's fascinating that some of the most audible "distortion" is often the hardest to directly measure. An example of a weird thing I worry a bit about these days is how humidity changes to driver suspension might affect stability of sound quality in a very tight in-room bass calibration. It may not really matter, or it could have rather profound effects. I don't really know. Perception is extremely sensitive to certain aspects of sound and seemingly completely ignorant of others. Which stuff matters?

I bet it sounded great! I don't think I've ever heard a system with serious bass output that can do 30 Hz --- outdoors. I know that indoors the extra extension really adds a lot of weight to that kick, and psytrance and other bass music seems like it very often goes below 40 Hz. If the transient response is good and the kick is tight, the weight just smacks you all at once. Did you end up tweaking the EQ I suggested or did you just use it verbatim? I'm glad whatever it was you did worked out for you.

Well, for subs measured by Data-Bass, there are the max long-term output, power compression, and harmonic distortion plots. For DIY systems there're also impedance and raw driver response plots which offer at least some hints as to how inductance effects may impact sound quality. Of course none of these things can be conveniently distiled down into one SPL "output" number, but so what? If you want the best, you're not going to find it by looking at a single chart or a single metric. That kind of "make everything quantifiable" BS is a major error, perhaps even at the root of some of the major problems facing our society right now. (Serious!) BTW I say this as an engineer who specialized in study of computational science. Also, why CEA at 20 Hz? Many small rooms have a lot of room gain by then. My room in particular dramatically boosts sub efficiency there. The air starts noticeably rippling before the "signal present" lights even come on on the amp. Tell me what the sub can do at 10 Hz, and then I'm interested. But of course for someone who need something small to fill a large room, maybe 30 Hz is the money spot. Hoffman's Iron Law can be overcome with brute (motor) force. The limitation then is how much magnetic flux you can ultimately focus on a coil, and whether the end result is remotely affordable. FWIW, I spent an excruciatingly long time deciding on which subs to buy for myself. I had a very specific location and space budget, and wanted the best I could possibly get with that space. I had to make a custom design. There was no chart that told me which driver would work best. I had to consider all the possibilities individually.

Honestly this seems like splitting a lot of hairs. The CEA scores use a fairly arbitrary distortion thresholds that are only maybe approximately at the limit of the actual usable output of the sub. The CEA score won't tell you how fast distortion drops as level is decreased, or does it tell you how much additional travel may be present in the driver in which distortion continues to rise but not as rapidly as another sub. The decision to buy a JL vs. a JTR sub should come down to a lot more than just CEA scores. Seriously, 3.5 vs 4.6 cubic feet? If they are the same 3D shape, this is going to be a tiny difference. In reality if space is very tight, one may fit the dimensions of the room better than the other.

I believe these group delay shifts are pretty modest. IIRC, an ideal LR4 at 80 Hz has excess delay in the 5-10 ms range. I used to think that getting more energy in the first arrival is important for the most intense slam, but I now believe that the experience of tactile slam is actually a very high level perception. My thinking is that the brain samples information from both ears and vibro-tactile receptors and then applies sophisticated "room correction" processing to this information in order to reconstruct an accurate estimate of the actual time-frequency aspects of the original sound. In my own room, as I tighten up the bass response accuracy, the sound and tactile sensation I perceive become remarkably more uniform throughout the room, despite what the localized measurements suggest. If accurate enough, one can get an extremely tight "thump inside the body" effect that is more like what one experiences with a powerful system outdoors. I'll hopefully be soon exploring this in other rooms and am particularly interested to see what I can do in tiny pathological rooms.

Thanks for creating and posting these samples. Can you explain a bit more about the reasoning that went into creating the particular filter response shape? Is this supposed to be group delay related to some kind of filter (e.g. crossover), an in-room acoustic effect, or something else? FWIW, I definitely notice a difference between the 100 ms and original with a clear reduction of impact. Between the 20 ms and original, I think I notice a very slight reduction in impact, but I'd want to do blinded A/B/X to be confident. Now having said this, there is a big caveat with your study because there's a big difference between GD applied electronically and GD that arises from acoustic effects. That's why I asked my first question above. Time and time again, engineers try to treat room acoustics as a "linear transform along a wire", when this is not the case at all. The ears and body are capable of sampling pressure at multiple locations (the ears and tactile), and the brain is very well adapted to parsing the content of the source (both time and frequency aspects!) from what could be a very messy sound-field with dramatic local variations in measured frequency response and group delay. So in general, electronic changes may be far far more audible than FR and GD features of similar magnitude that appear in in-room measurements. Another potential caveat here. You indicate that the frequency response of your filters "is reasonably flat, considered below threshold for audibility". I can't comment with certainty in your specific case, but in general, I would not be surprised if the frequency response changes you show were well above the audibility threshold on a system with strong accurate bass. This alone could have substantially affected the amount of perceived impact. Again, there is a big difference between filters applied electronically and influence of acoustics on measured sound vs. perception. Depending on the circumstances, I believe the brain can pick out excruciatingly small changes, likely below 0.01 dB for bass. These can be perceived most readily on transients. Regardless of the audibility of your filters, this experiment says little about the audibility of characteristics arising from room acoustics or whether it's necessary to "correct" the group delay deviations seen in in-room measurements. I can't emphasize enough how important it is to keep this distinguish in mind clearly when optimizing response. Also a comment about the sample material. The kick seemed a bit soft, diffuse, and fluttery to begin with, and it didn't really sound consistent between beats. Audacity spec analysis suggests that the kick has some high Q ringing at various frequencies, which also does not appear to be consistent between different beats. Differences in group delay might be a lot more apparent on tighter transients that don't ring so much.

Very nice! I experience a very tight thump on my living room system. It sounds bit shy below ~60 Hz, but that could be the particular music or a filter in the iPhone mic. I love the picture of the setup. It looks so compact, and yet I'm sure it can pack a wallop.

A quick Google on my end returns this: https://forums.prosoundweb.com/index.php?topic=72377.0 See around about post #7. Edit: My bad! Looks like those specs are for the 4580, not the 5840. An anagram, ehh? I think a good question at this point is what do you need the data for? Can you consider a more modern driver which, presumably has T/S specs published for it?

Nice. Maybe @Ricci can attach that to the first post as well.

Judging by the multiple out-of-context posts, I'm guessing it's some kind of AI spam-bot. Maybe it's some university student's pet project? I like to think of this as a preview of our robots/AI future. AI generally struggles to cope with "understanding" context, so in the future, we'll just do away with context entirely. Problem solved!

It's for a different project, a plain-vanilla vented cabinet. I'll probably start a thread for it soon. Either way though this discussion is relevant to the Skhorn. Vent round-overs certainly won't prevent chuffing, but I believe there's evidence that round-overs can improve flow characteristics at moderately high velocity, perhaps allowing an extra 1-2 dB before chuffing does become noticeable or before compression becomes serious. It's a minor detail but worth it IMO when vent area is a bit limited as it is with both the Skhorn and the design I'm working on. Also, I care more about avoiding/reducing compression, which sets in quite a bit sooner, than I do about chuffing. With compression, the spectral balance is distorted substantially as level is pushed higher. In use-cases where high accuracy/SQ is important, this is likely not acceptable, which effectively limited usable output to a level that may be much less than when chuffing because audible.

Thanks again for the suggestion. I am thinking along similar lines, though I do still need to be mindful of the round-overs. I'm also keeping the bracing dividers to 12mm. I'm trying to keep the weight down.