Jump to content


Popular Content

Showing most liked content since 09/17/2017 in Posts

  1. 8 points
    Final quarter of 2017 update. JTR Speakers Captivator 212Pro results have just been posted. KRK Systems 12S2 subwoofer testing is done. Should be posted next. WW Speakers / Mark Seaton designed X21 cabinet loaded with B&C 21DS115-4 driver testing is done. Will be posted ASAP as well. This was tested with both vents open and with a vent plugged and with both the Powersoft K20 and an Inuke 3000DSP. That's 4 full measurement sets. We're killing a lot birds with one stone on this one. We have some information on the Inuke 3000DSP amp driving a real load. We have the 21DS115-4 driver itself, which a lot of people are interested in and lastly we have the X21 vented cabinet which is available off the shelf to fit a variety of pro 21's. I tell you the cab is built solid and of course Mark designed it well. It is not cheap but it certainly offers an easy button option. Next up is a set of 3 subwoofers from one of the commercial vendors. I'm not totally sure these will be public on the site since the MFG reserves the right to decide whether the results are public or private. I believe they will be though as so far their behavior appears to be well designed. And...After that...I have a couple of cabs from a pro audio company that will be on deck. Not sure these will be public yet either but I suspect so. I'm trying to get this all tested and posted by the end of the year. That's the goal. I have more DIY type driver tests sitting in the wings too.
  2. 2 points
    So after reading this thread over the past year and amazed and the technical depth and extreme attention to detail paid to the tuning of this system and going "man I really want to hear this!", I flew and went to check out this system. And boy what an amazing system to listen to! My mind was blown as I was amazed by one thing after the other. All the work put into getting the tonal balance of this speaker correct really paid off big time. The whole system just sounds really "correct", and the more I listen to it the more I'm amazed by it. I brought my Reference Mini's with me as a comparison, and there was a very obvious difference in sound quality. I thought my speakers sounded really great, but it sound noticeably "off" when compared to this system. The speakers had a fantastic amount of detail, and the transients are awesome! It felt like I'm listening to a pair of really good headphones (and few people realize how hard and impressive it is to achieve this), but I also get the enveloping sound that makes speaker listening so pleasurable. It's the best of both worlds. What's even more impressive is the bass. I don't think I've heard bass so tight and full sounding in a room, which is clearly due to the complex integration efforts of multiple subs and individual EQ's to get such flat bass over a large number of seats. The clarity and tightness is seriously impressive. Again, just like a headphone, and that is actually something I've never heard before from a subwoofer. It is straight up the best sounding bass I've heard in a room. Now when you also get the whole body physical sensation from bass, addictive is an understatement. One thing that is unforgettable and blew my mind is how great the speakers sound in the kitchen! I don't think SME has ever mentioned this, but it was indeed one of his goals. It was remarkable hearing a correct tonal balance with almost no treble roll off in a different room! I still can't believe this is achievable. It must be the combination of controlled directivity speakers and properly placed diffusers pulled this amazing magic trick of a feat. I've heard a lot of amazing home theaters, but this is the first time I heard imaging from surrounds. It was trippy to be able to pinpoint the location of the sound going across the rear stage. I really wish we watched an action movie and be able to so accurately track the position of the sound effects. This is even more impressive as I seem to clearly have less ability to hear imaging compared to other people. Speaking about imaging, the speakers reproduced phase manipulated music tracks far more accurately than anything I've heard so far. It must be the room treatments that are preserving the phase accuracy of the speakers. It was like "oh this is where it is supposed to sound!" I was also exposed to the dark secrets of the time domain in room correction. That was a revelation to me to be exposed to so much more information and tools to analyze room acoustics. Now it makes sense why and how the room is mucking up the sound. It's all in the time domain! Now I am able to correlate measurements and subjective judgment of how good (or bad) the room sounds. I have so much to dig and play around with now. Measurements really can tell you about how good something sounds if you look at the right things and how to interpret it properly. Thank you SME and his wife for being such amazingly gracious hosts. That was one hell of a weekend! Oh, and did I make it clear enough that your system sounds good?
  3. 2 points
    Just made all of the good stuff for this visible. Please discuss here.
  4. 2 points
    A new addition for my space, Nathan's new 21.0LX, based on the UH21 driver.
  5. 2 points
  6. 1 point
    This is the first of it's kind objective measurement tool for comparing the bass in movies - it's totally apples-to-apples. (The measurement methodology AND content below 2.5 Stars is at the bottom of this post.) No longer do you have to rely on some website's review of the bass in a movie. Who can decipher what "aplomb" and "bombastic" and "incredibly deep" and "teeth-rattling" and "room-shuddering" really mean, anyway? Now you don't have to. The links below will take you to each movie's measurements. If a link doesn't take you to the right measurement, reload the browser by hitting F5 or just click on the address bar and hit "Enter." If you find a bad link, post about it and we'll investigate! Updated December 12, 2015 - Here's a Google docs spreadsheet with the current list. To sort, goto View-->List. 5-Star Films: 9 Edge of Tomorrow Everly Flight of the Phoenix Hellboy II: The Golden Army Pixels Ragnarok Star Trek War Horse 4.75-Star Films: All Is Lost Beowulf Captain America - The Winter Soldier Dredd Ender's Game The Golden Compass Hanna How to Train Your Dragon The Hurt Locker The Incredible Hulk Jupiter Ascending Kick-Ass 2 Live Free or Die Hard Lone Survivor Looper Mission Impossible: Ghost Protocol Olympus Has Fallen Phantom Pompeii Pulse Resident Evil: Apocalypse Serenity Skyfall The Terror Live The Three Musketeers (2011) Valkyrie War of the Worlds 4.5-Star Films: 28 Weeks Later 300: Rise of an Empire 5 Days of War Abraham Lincoln: Vampire Hunter After Earth The Amazing Spider-Man 2 Attack the Block Battle: Los Angeles Brave Cloverfield Conan the Barbarian (2011) Crank: High Voltage Daredevil The Dark Knight The Day After Tomorrow Drive Elektra Elysium Exodus: Gods and Kings The Expendables 3 Finding Nemo Gamer Getaway The Grandmaster (CHI) Harry Potter and the Goblet of Fire Harry Potter and the Order of the Phoenix The Iceman Insurgent Jurassic World Kon-Tiki The Man with the Iron Fists The Matrix Revolutions Ninja Assassin Oblivion Oculus Oz the Great and Powerful Percy Jackson and the Olympians: The Lightning Thief Sherlock Holmes Sky Captain and the World of Tomorrow (DTS) Solomon Kane Superman Returns Thor 2: The Dark World Trollhunter Underworld Awakening Walking With Dinosaurs (2013) X-Men 3 4.25-Star Films: 10,000 B.C. A Good Day to Die Hard The Admiral: Roaring Currents Adventures in Zambezia The Amazing Spider-Man Assassin's Bullet Avatar Batman Begins Black Hawk Down Bullet to the Head Captain America: The First Avenger Casino Royale Cat Run 2 Chappie Clash of the Titans The Conjuring The Dark Knight Rises Dead in Tombstone Death Race 2 Earth to Echo Evil Dead The Exorcism of Emily Rose The Expendables 2 The Grandmaster (USA) The Grey The Hitchhiker's Guide to the Galaxy Homefront Horton Hears a Who Hot Fuzz Immortals Inception The Incredibles Jack the Giant Slayer John Wick Jurassic Park III Legend of the Guardians: The Owls of Ga'Hoole LOTR: The Fellowship of the Ring (BR Ext Ed) Mad Max: Fury Road Maleficent The Maze Runner Monsters, Inc. Monsters University The Mortal Instruments: City of Bones Need For Speed Ninja Non-Stop Open Range Paranoia Pearl Harbor Piranha 3D Quantom of Solace The Raid 2: Berandal Ratatouille Resident Evil: Afterlife Rise of the Planet of the Apes Running Scared Rush Scott Pilgrim Vs. the World Seventh Son Shaun of the Dead Sin City Sin City 2 Snowpiercer Star Wars: A New Hope Total Recall Transformers Transformers: Revenge of the Fallen Triangle Tron: Legacy U-571 World War Z The World's End X-Men X-Men 2 X-Men: Days of Future Past X-Men: First Class 4-Star Films: 3:10 to Yuma The Bourne Legacy The Bourne Ultimatum Children of Men Commando Constantine Crank Death Race: Inferno Despicable Me 2 Escape Plan Fight Club GI Joe: Retaliation Gravity Hercules Inside Iron Man 2 Jack Ryan: Shadow Recruit Jarhead Kick-Ass Knight and Day Knowing Legends of Oz: Dorothy's Return LOTR: The Return of the King (BR Ext Ed) The Machine Max Payne Monster House Ninja: Shadow of a Tear (aka Ninja 2) Noah Pacific Rim (7.1 DTS-HD MA) The Railway Man Real Steel Resident Evil: Retribution Stalingrad Star Wars: Attack of the Clones Star Wars: The Phantom Menace Terminator 3: Rise of the Machines Terminator Salvation Thor Toy Story 2 Toy Story 3 Transformers: Age of Extinction Wall-E The Wolverine (7.1 DTS-HD Unleashed Ext Ed) 3.75-Star Films: 3 Days to Kill Alien Vs. Predator The Art of Flight Babylon A.D. Bears Bee Movie Bolt Bullet Captain Phillips Cars Don Jon The Fast and the Furious 6 Green Lantern Guardians of the Galaxy Happy Feet Hellboy Hitman Ice Age Ice Age: Dawn of the Dinosaurs Insidious Chapter 2 Interstellar Into the Woods Iron Man Jarhead 2 Jurassic Park Kingsman: The Secret Service Kung Fu Panda Limitless LOTR: The Fellowship of the Ring (Theatrical BR) LOTR: The Two Towers (BR Ext Ed) The Lords of Salem Machete Kills Megamind The Raid: Redemption Rambo (2008 Theatrical) Robocop (2014) Seal Team Eight The Simpsons Movie Sinister Star Trek Into Darkness The Watch Watchmen Wrath of the Titans X-Men Origins: Wolverine 3.5-Star Films: 13 Sins 30 Days of Night The A-Team Act of Valor Alien Abduction Australia Baraka Blue Crush The Croods Dr. Seuss' The Lorax The Equalizer The Frozen Ground Fruitvale Station Fury Godzilla (2014) Harry Potter and the Chamber of Secrets Harry Potter and the Prisoner of Azkaban The Hobbit: The Battle of the Five Armies Hulk The Hunger Games: Catching Fire The Hunger Games: Mockingjay Part 1 I, Robot Ice Age: The Meltdown King Kong (2005) The Legend of Hercules The Lego Movie The Losers Lucy Man of Steel Man of Tai Chi The Man With the Iron Fists 2 The Matrix Reloaded Mission Impossible III The Monuments Men Pain and Gain Paranormal Activity The Marked Ones Robocop Sherlock Holmes: A Game of Shadows Speed Racer Star Wars: Return of the Jedi (BR) Star Wars: Revenge of the Sith (BR) Sunshine Teenage Mutant Ninja Turtles (2014) This Is the End Titan AE (DVD) Transformers: Dark of the Moon Underworld: Rise of the Lycans Unstoppable You're Next Zero Dark Thirty 3.25-Star Films: 21 Jump Street American Sniper The Art of the Steal Avengers Avengers: Age of Ultron Batman: Under the Red Hood Black Sea The Book Thief Carrie (2013) Cowboys & Aliens Domino The Double Eragon Ex Machina The Family Frankenstein's Army Gangster Squad The Great Gatsby (2013) Harry Potter and the Half-Blood Prince The Hunger Games I, Frankenstein Into the Storm Iron Man 3 Knights of Badassdom The Last Days On Mars Marley McCanick Minority Report Out of the Furnace Planes Prometheus Reasonable Doubt Rio Runner Runner Star Wars: The Empire Strikes Back (BR) Taken 2 Toy Story Turbo Veronica Mars The Movie 3-Star Films: 2 Guns A Touch of Sin Battleship Big Hero 6 Blade Runner Brick Mansions The Cabin in the Woods Chronicle Dawn of the Planet of the Apes Die Hard District 9 Epic Frozen Haunter The Hobbit: The Desolation of Smaug Ice Age: Continental Drift The International The Internship Jumper The Lone Ranger The Lost World: Jurassic Park Man On Fire Master & Commander (BR) Red 2 Resident Evil: Extinction Riddick Ride Along Saving Private Ryan Vampire Academy 2.75-Star Films: 28 Days Later Blood Ties Cloudy With A Chance of Meatballs 2 Devil's Due Die Another Day Don't Be Afraid of the Dark Dracula Untold Grudge Match Harry Potter and the Sorcerer's Stone How to Train Your Dragon 2 I Am Number Four The Matrix Metallica Through the Never Paddington Percy Jackson: Sea of Monsters Planes: Fire and Rescue Resident Evil R.I.P.D. Whiplash 2.5-Star Films: The Babadook Bad Country Death Race Divergent The Fifth Element The Natural Rio 2
  7. 1 point
    Had not got T5 yet on video but will eventually. People love to poop on Michael Bay and T5 has serious issues but in a hobby for A/V..... T5 brings it. Interested in the Atmos track and if it is (better be) a remarkable improvement from T4's barely-Atmos track. And yes... let's bring back the days when 20hz was cool cuz it still is, imho.
  8. 1 point
    Is no one going to talk about the audio in Transformers "The Last Knight" whenever Megatron is on camera? The audio has been lightly brushed on Data-Bass but I don't recall anyone going into detail. I SpecLab'd a few scenes last night and when Megatron lands in the salt flats the hottest spot is centered at 20 Hz. Sure it's no 7 Hz WOTW, but the sound in the movie makes it worth watching and also using for demo's. I haven't seen much talk about it so I'll go out on a limb and say that I love the proper audio in this movie.
  9. 1 point
    Yes, I did generalize for a tapped horn, and now that I think about it, I might not be correct even for that case. Several 10s of milliseconds sounds very high for "room acoustics" effects. A full cycle at 60 Hz is 17 ms. If you are delaying more than that (in addition to distance and "internal" effects), then you are probably adding unnecessary group delay, which likely impacts transient response sound quality and slam. FWIW, I've been studying this problem quite intently lately, trying to improve integration between my speakers and subs. Unlike most people, I have practically unlimited DSP resources to throw at the problem, where the only real practical limit is latency. I would say that the processing capabilities built into AVRs and most processors are woefully inadequate for achieving an optimal outcome. The"THX "LR4 sub/sat crossover" is largely fantasy that rarely occurs in real world conditions. The best that most people can do is a brute force evaluation of different XO frequencies and sub delays, where typically response is only optimized on one channel and at one seat. Yet even this effort requires more sophistication than most users are capable of. (Readers of DataBass and some of those who read AVSForum are obvious exceptions.) No wonder a lot of people prefer bass from 2 channel full-range speakers vs. subs. While the in-room "placement" of the LF drivers in such speakers is non-optimal, the XO is (ideally) optimal for that placement. I've noticed that good anechoic-flat full-range speakers, when pulled far enough from walls, can deliver impressive slam; whereas many sub systems including many with big horns or many large drivers struggle in this respect. My recent experience suggests that phase (or rather group delay) effects are more important than most people realize. And it's not what people think. I.e., a ported sub isn't necessarily sloppier than a sealed sub, though that obviously depends on the competence of design. Such effects are largely minimum phase. (A good thing.) Rather, it is the excess group delay, which arises from crossovers and distance differences that appears to be important. Pre-ringing in particular seems to really kill tactile slam, and it should be noted that FIR filters are not the only way to introduce pre-ringing into a system. Pre-ringing can arise merely from placements and/or delay settings. Any situation in which sound from a sub may reach the listener before sound from a speaker potentially involves pre-ringing. Rooms with rear subs are likely to exhibit pre-ringing for rows behind the one used for calibration. What's not at all clear is where the perceptual thresholds lie for hearing and feeling of pre-ringing effects. Anyway, I still have a lot of work to do here, and at some point, I may try to do some more formal testing of excess group delay effects, including pre-ringing, as this information would be very useful for optimizing sub systems for multi-listener environments.
  10. 1 point
    The Yamaha CX-A5100 will do a little over 24 dBu (13 VRMS) on its subwoofer output. However, its bass management will clip the signal on worse case real content unless the subwoofer trim is set to -7 dB and master volume control isn't above 0 dB. I've checked 3 Marantz 7702 MKII's in the past two weeks and they all clip when using bass management unless the master volume control was at -3 dB and the subwoofer trim was at -7 dB. With the master volume control at 0 dB and the trim at -10 dB, they still clipped. I tested with How to Train Your Dragon and White House Down. I don't really like Marantz or Denon processors because they are limited to 20 ms of delay. You can't integrate a horn subwoofer properly, use them in large home theater, or add additional external subwoofer DSP (depending on latency of the DSP). Yamaha allows for 72 ms of delay. I am a Denon and Yamaha dealer.
  11. 1 point
  12. 1 point
    I didn't ever say that I thought the movie had bad audio or visuals. Technically the movie is very well done and nearly flawless. I just didn't always agree artistically with the choices Villaneuve made regarding the visual and audio design. That's purely subjective to my tastes. Of course it goes without saying that my taste in movies is perfect. By that measure everyone else should finally come to terms with the fact that Titanic is a great movie
  13. 1 point
    Ya'll crazy. This was wonderful A/V all around (saw in Dolby Cinema) and I can not wait to get it on UHD/BD to watch at home. This will probably rate well in bass too. It's time will come.
  14. 1 point
    I don't think anyone has but you could. I wouldn't advise it for actual touring use but if they won't be moved that much it should be ok.
  15. 1 point
    That looks pretty decent - 20Hz filter is better than a kick in the teeth and it may be a potential contender for BEQ...
  16. 1 point
    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.
  17. 1 point
    Soon to come , report about cardioid directivity trough interference from Merlijn Van Veen. I will check it frequently to see what news we will get https://m.facebook.com/story.php?story_fbid=2537646626376057&id=1871382083002518
  18. 1 point
    Very impressive results for such a small cabinet, driver size, and low cost. Of particularly noteworthy aspect of the performance, which Jeff kinda pointed out already, is how little difference there is between the long term output and burst output. I've never seen a passive system driven by a K10/K20 report such small differences. I wonder what's going on. In one way it can be seen as excellent design that maximizes long term output, in another one could wonder what's going on with the drivers that they can barely handle 100V during burst testing. Anyone wanna chime in?
  19. 1 point
    Looking at some comparisons, in the music range (above 45hz):
  20. 1 point
    http://www.avsforum.com/forum/113-subwoofers-bass-transducers/2763785-ultimate-list-bass-movies-w-frequency-charts-86.html#post54824590 I bet no one was expecting this
  21. 1 point
    admittedly I haven't reduced the capacity in my system at any time yet but I think I must be at the point where moar genuinely is overkill (at least without changes that allow me to put more subs in the room anyway). I did have a pair of low teens xmax 12s behind me which gave solid response down to ~14-15Hz in the NF position whereas I now have a pair of high xmax 18s so that yields something like 5-6x the Vd. This is quite a large uptick. Admittedly part of the reason is to get a larger radiating area so even that impact across the sofa but it remains to be seen whether my wife appreciates that anyway back to the subject of this thread... I ran some quick tests today to check for port noise, I went to ~112dB (at the LP) with no noise at all & you could just about feel the air if you put your hand on the port. I used REW's CEA-2010 signal for that test at 16, 20 & 25, the only distortion product visible (at that ~112dB level) was 40-50dB down so basically non existent. I'll push that some more another time just to see what happens. I haven't had a chance to properly run through some listening sessions yet so will leave any subjective commentary til later.
  22. 1 point
    http://www.audioxpress.com/article/test-bench-b-c-speakers-21ds115-21-inch-woofer Bench test review. The factory can provide also their own LSI Klippel results that can be compared to these ones and adding that to the tests Ricci did, I can say this is a very interesting driver at a very good price IMO.
  23. 1 point
    I watched "Thor" with BEQ tonight. It's the first time I've watched "Thor" on the new system, and I'm glad I waited. This was a very loud track with a lot of wide-band upper mid / high frequency effects. And of course there is clipping in a lot of places. However, I was pleasantly surprised by how good it sounded at my usual "-4" playback level and without any roll-offs applied, even at the top. The loud effects were never uncomfortable or harsh. In some sense, this was a great mix for the mixers, but not so much for those with inferior systems, which would tend to not handle the harsh, overdriven waveforms as gracefully. Certainly the last time I watched this on mere "92 dB/2.83V/1m" speakers, I found it to be uncomfortable at "-7". The bass here with BEQ was a lot of fun. I think a lot of sequences in this are demo-able. At one point, I noticed very slow sweep down in the infrasonic range. Very subtle, but very effective for the scene it was in. I also noticed some nice ULF ambiance (wind) in the some of the desert scenes. Perhaps this was just "noise" picked up by the mic, but it fit the picture very well. In fact, nothing sounded out of place with the BEQ. I think about the people on AVSForum who argue that extra extension is worthless because "the director didn't hear it that low" on the stage. True enough, but that doesn't mean that it isn't a great track with full extension. I'd argue that I heard it the way the director would have wanted it to be heard, if he/she had known better. Big thanks again to JSS for putting this together. I have to say that I've enjoyed the ULF in BEQ films more than in just about any of the naturally extended films I've watched. Your work is high quality.
  24. 1 point
    I've been wanting to weigh in here for a while but have been busy. First, I think a half-space to full-space transition is very unlikely. Second, THD vs. excursion is not constant at all constant with frequency. THD during sine sweeps is a consequence of non-linearity in various system parameters. AIUI, the Klippel system measures linearity of the driver suspension stiffness (K), the magnetic flux (B ), and the inductance (Le) with respect to cone displacement. Because the relative influence of these parameters on the overall system behavior varies with respect to frequency, the distortion that results due to non-linearity of these parameters will also vary. With respect to the trends observed here, I believe that what is happening is that a lot of drivers have better BL linearity than K linearity. I've mentioned in a few other places already, system stiffness/compliance (note that these quantities are merely inverses of one another) has a very strong impact on ULF efficiency. The same is true of BL, but unlike BL, stiffness has less importance as higher frequencies. An area where things get interesting is the resonance frequency. The resonance frequency is determined by stiffness and mass. However, while the woofer is near resonance, the effects of the stiffness and mass essentially cancel. (Edit: This isn't really the best description of what is happening at resonance. See below for the interesting results with respect to stiffness/compliance.) I've been doing some mathematical analysis to try to better understand the extent to which non-linearity of system parameters influences distortion. I started with just system stiffness and assumed it took a form like: k = k1*(1 + k3*X^2) Edit: Typo corrections here. "k1*(1 * k1/k3*X^2)" has been corrected to "k1*(1 + k3*X^2)" Edit: This shape is plotted below for various k3 values: We define X as the fraction of peak displacement. In other words, X=+/-1 when displacement is at the peak. By doing so, we can let k1 be the stiffness without distortion and k3 be the fraction by which the stiffness increases at the peak of excursion. The X^2 is a parabola, so this models a suspension that gets stiffer by an equal amount with inward and outward displacement. This form for k is very useful because it is a simple model that will produce odd-order harmonic distortion similar that that exhibited by a real driver. Note that this model ignores mechanical damping, which is often very small anyway. Chugging through the math (and hopefully not goofing anything up), I got the following results for the ratio of third harmonic relative to the fundamental. It is helpful to define a useful quantity, om0 (the "om" is traditionally symbolized by a lowercase Greek omega), which is related to the resonance frequency of the undistorted system (fb). We also define om in terms of the frequency of interest (f). To be clear, om0 is a property of system while om is a variable that changes with frequency: om0 = 2*pi*fb = sqrt(k1/m) om = 2*pi*f |H3| = 9 * k3 * om0^2 * sqrt{ 1 + 9*om^2*(Le/R)^2 } / sqrt{ [om0^2 - 9*om^2]^2 + 9*om^2*[om0/Qtc + Le/R*(om0^2 - 9*om^2)]^2 } (Edit: This formula and those that follow have been completely re-written into "simpler" forms.) Ugh! Lots of math. Well, the math getting there was much worse. One way to simplify is to assume zero inductance, which is probably not a bad approximation at low frequencies and may be a good approximation at fairly high frequencies for some drivers with very low Le/R: |H3| = 9 * k3 *om0^2 / sqrt{ [om0^2 - 9*om^2]^2 + 9*om^2*(om0/Qtc)^2 } (assuming no inductance) That's a lot better. We can simplify things further by considering some special cases. First, consider very low frequency, so low that 3*om is much less than om0 (we're well below 1/3th of the resonance frequency): |H3| = 9 * k3 / sqrt{ 1 + 9*[om/(om0*Qtc)]^2 } (assuming no inductance and frequency well below 1/3 of the box resonance) |H3| = 9 * k3 (assuming no inductance, frequency well below 1/3 of the box resonance, and frequency well below 1/3 of the box resonance times Qtc) These assumptions are pretty restrictive considering that typical box resonances are in the 25-50 Hz range, but they give insight into 3rd harmonic distortion for the lowest of low frequencies. (Low single digits in most cases). In this situation, the percent change in stiffness at the peak is related directly to the 3rd harmonic distortion of the displacement. However, the third harmonic distortion in the output is 9 times greater than the third harmonic distortion of the displacement. Let's look at high frequencies now, where om is much greater than om0. We'll consider the results both with and without inductance. Where we consider inductance, we'll go ahead and assume the frequency is high enough that the inductance rise is fully established, or mathematically that 3*om is much greater than R/Le. Let's assume that it's much larger than R/Le, R/(BL)^2, that we're well above the resonance frequency, and that 2*pi*f^2*m is much larger than (BL)^2/Le: |H3| = 9 * k3 * om0^2 * Le/R / sqrt{ 9*om^2 + [om0/Qtc - 9*Le/R*om^2]^2 } (frequency well above resonance and fully developed inductance) |H3| = k3 * om0^2 / om^2 (assume frequency well above resonance, fully developed inductance, and frequency well above 1/3 of resonance divided by Qtc) |H3| = k3 * om0^2 / sqrt{ om^2 * [om^2 + (om0/(3*Qtc)]^2] } (assume no inductance and frequency well above resonance) |H3| = k3 * om0^2 / om^2 (assume no inductance, frequency well above resonance, and frequency well above 1/3 of the box resonance times Qtc) As frequency goes up, the influence of k3 diminishes to nothing. What about at the system resonance? At the resonance, om = om0. Let's see what happens: |H3| = 9 * k3 * sqrt{ 1 + 9*om0^2*(Le/R)^2 } / sqrt{ 64 + 9*[1/Qtc - 8*Le/R*(om0)]^2 } (at resonance) |H3| = k3 / sqrt{ 64/81 + 1/(3*Qtc)^2 } (at resonance and assuming zero inductance) When ignoring inductance for simplicity, we obtain a fairly simple expression for the third harmonic distortion. To get an idea of how this compares to the third harmonic distortion in the low frequency limit, let's look at |H3| for some values of Qtc: |H3| = 0.624*k3 (at resonance with zero inductance and Qtc=0.25) |H3| = 0.900*k3 (at resonance with zero inductance and Qtc=0.5) |H3| = 0.994*k3 (at resonance with zero inductance and Qtc=0.707) |H3| = 1.05*k3 (at resonance with zero inductance and Qtc=1.0) We can see that the third harmonic distortion due to stiffness non-linearity will be much smaller at resonance than for lower frequencies, and lower Qtc alignments have less distortion than higher Qtc alignments. Let's look at one more case. Suppose we use a frequency that's 1/3rd of the system resonance, om = 1/3*om0. This is a pretty low frequency, but it happens to fall right in the area that is of interest in many ULF applications. It is physically relevant because the harmonic that's produced is at the system resonance: |H3| = 9 * k3 * Qtc * sqrt{ 1 + om0^2*(Le/R)^2 } (at 1/3 of resonance) |H3| = 9 * k3 * Qtc (at 1/3 of resonance and ignoring inductance) |H3| = 2.25*k3 (at 1/3 resonance with zero inductance and Qtc=0.25) |H3| = 4.5*k3 (at 1/3resonance with zero inductance and Qtc=0.5) |H3| = 6.36*k3 (at 1/3resonance with zero inductance and Qtc=0.707) |H3| = 9*k3 (at 1/3resonance with zero inductance and Qtc=1.0) This is a very interesting result. It again suggests that Qtc has an influence on distortion. And in fact, if Qtc is greater than 1, the distortion at 1/3 of the resonance will actually be *higher* than it is for the lowest frequencies and a 3rd harmonic distortion peak will appear in this region. In a sense, the resonance of the system helps amplify the 3rd harmonic. A lower Qtc means more back-EMF and more damping for this unwanted harmonic. There's a lot more insight that could be gained with more analysis like this. I wouldn't be surprised if Klippel has outlined some of this in his papers. Looking at B non-linearity is a bit harder because it affect both the mechanical and electrical balances. It can also vary with the current as well displacement, which has been mentioned here already. So called flux modulation distortion occurs due to the interaction of the permanent magnetic field of the driver with the temporary magnetic field induced by the current in the coil. This could also account for a big increase in distortion relative to displacement in lower frequencies, but I still think compliance stiffness non-linearity is the most common reason for this trend. Why? Because flux modulation distortion should also affect frequencies well above the resonance unless inductance is extremely high. OK. Hopefully I won't have to revise any of these formulae, but I might after I review my work at a later point. Edit: Correction: the original formulae I made were for 3rd harmonic of displacement vs. fundamental of displacement. However, pressure relative to displacement scales with 1/f^2 (12 dB/octave). So since we really want to know the 3rd harmonic vs. fundamental for pressure, everything gets multiplied by 3^2 = 9. Because all the results are scaled equally, the trends are still the same. On the other hand, we see that for very low frequencies, distortion is extremely sensitive to non-linearity in the stiffness. Stiffness distortion of 10% 3rd harmonic will result in 90% 3rd harmonic distortion of the sound. Edit: I caught and corrected an algebra error I made in the formulas. The overall interpretation doesn't change much. The big change is that the Qtc must be greater than 1.0 rather than 0.33 for there to be a 3rd harmonic distortion bump at 1/3rd of the resonance frequency. Edit: I rewrote the formulas in terms of fewer variables to make them more useful. I also rewrote and improved the interpretation of the results. Hopefully in time, I'll be able to do some plots to make it easier to *see* the trends I wrote about above. Edit: Here is a plot that characterizes the third harmonic distortion behavior in this model for k for different Qtc alignments. These assume no inductance for simplicity. The x-axis is what might be called reduced frequency. It's the ratio of the frequency to the box resonance frequency. The y-axis is the factor that you multiply k3 by to determine the level of the distortion harmonic relative to the fundamental. What kind of high frequency roll-off do you think that is? It's 12 dB/octave. There is a subtle caveat to consider when looking at this plot. The "k" value in the model is for the overall stiffness of the system rather than the driver alone. It is not a model of distortion in driver Kms. What this means is that if you wanted to compare distortion for different Qtc alignments for a particular driver, you can't really use this plot directly. The k in this model is the sum of Kms and the air spring. To use a driver in a higher Qtc alignment, you necessarily shrink the box and increase the stiffness of the air spring. That actually makes the system stiffness more linear by overwhelming the deviation contributed by the Kms non-linearity. As such, it's not entirely clear that lower Qts = lower distortion as far as Kms non-linearity is concerned. With a small adjustment to the model, I may be able to resolve this without issue. Stay tuned. Edit: As a related caveat that I missed that may be more obvious is that changing the Qtc changes the fb as well. If you take a driver and build sealed systems with different Qtc values, the fbs change also. This has the effect of shifting the absolute frequency scale relative to the x-axis for each curve, thus visually shifting the curves relative to one another. Depending on the situation, it's possible that the curves could overlap in places. The reason the curves are presented this way is because it makes the plot more generally useful. If an absolute frequency scale were to be used, you'd also have to fix the resonance frequency or some other parameters to do the plot, making it less generally useful.
  25. 1 point
    Though I'm sure there are guys stateside that can do it, and are a lot better at soldering too. I just thought posting a guide was a nice gesture as these amps are so popular in the diy crowd. Modding them would make them less crappy for powering infrasonic subs
  26. 0 points
    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