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SME last won the day on October 16 2019

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About SME

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    Super Bass Overlord

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  1. My counter would be that the bandwidth is too large and too smooth to be a TH. The EQ might help with smoothing response, but what about overall bandwidth?
  2. Occasionally when watching movies with heavy ULF during the day time (often for critical evaluation), I notice motion in the corner of my eye coming from the flexing of the large, nearly floor-to-ceiling living room windows on my left wall. Yeah, the Hi Def Digest graph looks like it's probably "wrong", at least in terms of level normalization. Just comparing the peak levels between the two at 30 Hz, they are too far apart for lack of dialnorm compensation to be the only fault.
  3. Is that a sealed alignment or something else? It sure does drop like a rock below 20 Hz.
  4. The short answer is that different windows were likely used for each piece before averaging. There is no universal PvA. Different windows types and sizes change the emphasis of certain aspects of response.
  5. The design looks OK. The ports definitely exit close to the cabinet wall, but I think that will be OK as long as you don't go any closer. The wall will help lower the tune a bit more than the flared pipe alone would. However if that's your cut-sheet list, you are missing something very important: bracing. Bracing helps stiffen up the cabinet walls so that they don't flex as much which causes some bass to be lost and causes the enclosure to resonate at somewhat higher frequencies, coloring the sound. The bracing design is a little tricky being that you have to clear the driver as well as the vents while trying to avoid letting any panels have more than a 6-8" span unbraced. You might also want to build in some extra support for the vents, near the rear, being that they are quite long and presumably only attached at the front baffle. (You might also want to put foam or cloth between the tube and brace to avoid buzzing sounds if they vibrate against one another.) Ensuring no more than 6-8" of panel is unbraced is a good rough target, but often some compromise is necessary. Either way, some bracing is much better than none. You will also want to add a light amount pf absorptive material (polyfill / pillow stuffing is popular as are denim scraps) around the inside panels to try to reduce resonances in the air cavity, which can also transmit through the panels. After accounting for bracing, the cabinet volume will probably be a tad smaller, maybe 6.5 cuft (?) depending on design. That should still tune at around 20 Hz.
  6. Sorry I can't help there, but ... I love the playa pyro pachyderm! I did a couple burns, last time in '06. That year it felt like it was just a huge event, especially on Friday and Saturday nights when there were so many people everywhere who were so frelled up that I could have convinced myself I was in a raver zombie apocalypse. Also, I've been to places like Washington DC National Mall, NYC, and (gasp) Boston, and no other place has a greater proportion and variety of law enforcement agents than Burning Man. The event is a kind of a psychedelic fun house in the middle of an alien, post-apocalyptic police state planet. I understand the event is now roughly *twice as big* as it was then. It's amazing to me that it still functions, which is kind of a marvel of its own. Have fun with that car! Is there going to be a bar on top?
  7. I had the problem of spinning the bit too fast with *hand-held* routing in my speaker builds. I broke a couple 6 mm bits that way before I learned about RPMs and feed rates from the CNC forums. So I dropped my speed setting to "2" out of "6" (about 10k RPM I think) and sped up my manual feed rate. That helped a lot, but I still needed to make very shallow passes (like 3 mm or less) to avoid problems. That's what I did with my subs. Unfortunately the compression bit I used caused nasty tear-out because the tip of the bit is designed to be on the *other side* of the work-piece where it pushes chips up and towards the piece instead of away from it. So I think for my next project I will use a down-cut bit with very shallow passes and hopefully be able to keep it sharp long enough to use on more than one project. BB plywood just seems to be the worst enemy of cutters. Maybe the material I'm getting is just particularly nasty? It builds some damn good speakers and subs though.
  8. Hi @maxmercy, I'd like to request that you post the BEQs you did. You can post them in the private forum instead if you want. My wife has requested that we screen these films over her Xmas break, and I figure this would be a great time to evaluate your candidate BEQs. I can give honest feedback including sharing any tweaks I make myself.
  9. I'm sure that rings like crazy! And it's got only "3 Stars" dynamics to boot. I haven't seen that movie yet though. I think a lot of people have floor or wall resonances around 25 Hz, and so a track like that is likely to shake things like crazy, especially on vented subs with a similar tune. I've been mostly slacking a bit on movie watching lately, but I did watch "MI4:Ghost Protocol" tonight (for the first time) and thought the bass and overall sound design was very solid. I wish more movies had bass like that.
  10. My SP2-12000 is still on 120V, on the same 20A circuit as all the rest of my gear including: a 55" LCD TV, 2 Emotiva XPA-5 gen2s, a Motu 16A, a Denon 3313CI AVR, two (fairly low power) PCs, a BD player or PS3, and a couple routers. Loud movie bass passages with ULF lasting several seconds can be tickling the clip lights, but I've still never tripped the breaker or even heard any sign of distortion suggesting voltage sag. The mains run from the panel is only about 15 feet, which might make a difference. Also, my subs are crazy efficient at 30 Hz and up, so the amp doesn't have to pull much current unless there's a lot of ULF.
  11. Shall I take it as a positive indication that you aren't selling any of the other stuff?
  12. To add to this: Hornresp reports acoustic power output as a normalized value such that if radiation is omni-directional (throughout the solid radiation angle chosen for the simulation, e.g. 2-pi) it matches direct sound SPL that would be measured. However when there are directivity effects, it's normal SPL to be quite a bit higher than what Hornresp shows, simply because there may be a lot more sound radiating along the ground than say vertically above the sub. Another potential cause of higher output (albeit over a fairly narrow region) that I don't see mentioned is port resonance. The Hornresp simulation doesn't seem to show that, but the impedance and measurement data suggest that could be going on here also.
  13. Just to double check some things. The 7 cuft should be the *internal* volume left over after subtracting stuff like the internal bracing and *especially* the port. Also the driver takes up some space, though probably not more than 0.25 cuft or so. The port dividers reduce the cross-sectional area of the port slightly, so you are right that this will drop the tuning a bit more than without them. It shouldn't be hard to calculate how much area you lose ... For 2 dividers of 3/4" thickness in a 3" tall slot port you lose (2 * 3/4 * 3) = 4.5 in^2. It's that simple. There is one more important consideration worth mentioning. Vents have a "pipe resonance" (like an organ pipe) at a certain frequency depending on its length. Your 40" pipe is likely to resonate around 150 Hz. That's a bit lower than we'd like but is "do-able", especially if you are crossing over at 80 Hz and not higher. Certainly we wouldn't want a vent that's any longer. As you can surmise when trying to make a low-tuned cabinet as small as possible, there is an inherent trade-off between getting vent area large enough to not overload at high levels while keeping the length short enough to fit into the cabinet and to avoid making the pipe resonance too low. This is a trade-off that vented system designers have to routinely make, and it gets worse when either tuning lower or trying to use a driver with more output. Your final design looks pretty good as far as balancing trade-offs. For the length, area, and volume you specified, Hornresp indicates a tune of around 22.5 Hz. A 3rd order high pass filter at 18 Hz appears to control excursion well and gives you a response that's roughly -6 dB at 20 Hz and -10 dB at 18 Hz. Depending on what your room is doing, you may get useful output quite a bit lower than that. If you plug a vent and use the same HPF, you lower the tune to 18.5 Hz, which gets you -6 dB at 17.5 Hz and -10 dB at 15 Hz. Again, your room may help things get a bit lower. In both cases, vent velocities are very reasonable, so you're not likely to see much compression. While plugging two vents will technically get you a 13 Hz tune, you don't really gain any usable output or extension this way, so I wouldn't recommend using it this way. Anyway, good luck with the build! We look forward to hearing of your progress.
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