DrWho

I just reread my two posts and I think there's some confusion there....I was focusing on the nuances of difference, not trying to imply that nobody believes in them altogether. One interesting thing to note though is that most of the blackhole images we've seen tend to be artist renderings. The stock footage looks totally different: http://chandra.harvard.edu/photo/category/blackholes.html (Make sure to note when it's showing an artist rendering or computer simulation - they don't point it out necessarily. Gotta read the text).

So what courses have you taken?

Can you substantiate that? I am not picking, but I would like a bit of validation. There are multiple mathematical descriptions posited, and they're always in flux. I believe the basic tenant is founded in an extrapolation of spacetime principals: Can there be a mass so large that light can't escape the gravity well? It depends on the math equation that is used to describe the scenario. So what then is the correct equation? This is where the theoretical guys go off and find equations that are consistent with as many already existing ideas as possible. The lack of consensus on mathematical definitions is really what I was trying to get at. Lots of theories, lots of reasons to support different theories, and an extremely small set of observational data. It's been several years since I was studying this stuff in college. The recent gravity wave announcement got me revisiting notes and brushing up on the subject, and I'm realizing how much I've forgotten, and how much has changed since then. My profs at the time didn't spend much time on Hawking...they presented him in a much different light back then.

It shows some of his work in applying mathematics to solve some of the problems that himself and other theoretical physicists were having using conventional techniques. Absolutely agreed on that front....the dude is a math genius. I just think there is a difference between "solving the math" and "offering new insight". Demonstrating new insight requires solving the math, but solving the math does not necessitate a new insight.

I'm not implying a local seismic event here.... I'm saying any event measured at two points in space with a specific time difference results in a solution set that constitutes an entire plane. That plane could be one-dimensional I suppose (a line), but this is just straight up linear algebra.

I'm familiar with the first link. Nothing of meat there. That second link is a good example of what I'm looking for. I don't know how any of his philosophical conclusions are derived by the "conclusions" of that paper: "We extend the holographic formulation of the semiclassical no-boundary wave function (NBWF) to models with Maxwell vector elds. It is shown that the familiar saddle points of the NBWF have a representation in which a regular, Euclidean asymptotic AdS geometry smoothly joins onto a Lorentzian asymptotically de Sitter universe through a complex transition region. The tree level probabilities of Lorentzian histories are fully specied by the action of the AdS region of the saddle points. The scalar and vector matter proles in this region are complex from an AdS viewpoint, with universal asymptotic phases. The dual description of the semiclassical NBWF thus involves complex deformations of Euclidean CFTs." Remove the fancy words and what do we have here? Two different "functions" smoothly align under certain conditions. That's like saying y=x has the same slope as y=x^2 when x = 1. Certainly way more involved of a calculation, and really cool stuff.....but let's keep this in perspective. He's describing the shape of functions. That's a lot different than describing the shape of observations.... How does this put him on the same page as Einstein or Newton? Am I missing a nuance here?

That there are no harmful effects whatsoever of marijuana use. Don't get me wrong, the political history of that was full of crazy propaganda and lies, but it's not completely harmless the way the article implies.....especially for younger people. Brain development in the early years is certainly impacted, and it goes until an average age of 25. It's related to the same chemical changes that causes 25 year old males to start thinking about consequences that allows insurance rates to go down.

A bit more agreement now that gravitational waves have been detected that confirm Einstein and support Hawking. Well what we really have are two plates in America that moved with the same chirp frequency......and then a lot of mental jockeying to convince ourselves that it was triggered by the orbiting / crashing black hole scenario. Have two sites record the same event limits the source of the event to an infinite plane. I'm not sure we're able to observe that much space simultaneously. We definitely want to hype it up though so we can get some more funding to create better analyzers. That 3 point system they want to put into the gravitational null between the Earth and Sun is a natural next step. Having three points limits that future event to a line, which again makes it hard to analyze what was the original source. Btw, I have a hard time believing such massive objects could be rotating around each other so quickly. That's why I'm looking for some more details - maybe they frequency scaled it to make it more relate-able to the public.

A bit inaccurate and one-sided but whatever. I've been following the Marijuana debates on C-SPAN. A much different light is painted there, but then a balanced perspective doesn't make for a good news article. That said, I'd rather see marijuana legalized before alcohol and cigarettes....

Btw, the majority of the scientific community doesn't even agree on the idea of black holes / singularities in the first place. We really know very little about the black dots we see in the sky. I mean, really consider what exactly it is we're observing. I am also reminded of all the wild conclusions that were drawn as a result of some speck on the Hubble telescope. Again, not discrediting the application of logic - just an honest observation about what is actually understood. All of the science surrounding string theory, singularities, etc.... needs to be held with an open palm because it's a highly volatile field right now. Lots of crazy math, but very little observation. That to me is what defines "fanciful".....especially when the proponents are so sure about the "truth" of which they speak.

What is practical about relativity? Einstein was very playful, and Hawking can't even speak. It's hard to imagine how 'fanciful' and 'sensational' are being applied here. I realize those at subjective, but I've never heard anyone inside or outside of science use those words for Hawking.Sent from my SM-T330NU using Tapatalk Rather than discuss semantics, I could summarize the above with a question: Where are the equations Hawking has presented? What are the testable ideas? Literal question btw. Here is an excerpt from Hawking demonstrating some further insight into my criticism: "If a black hole was in contact with thermal radiation, it would absorb some of the radiation, but it would not give off any radiation, since by definition, a black hole was a region from which nothing could escape. If the thermal radiation was at a lower temperature than the black hole, the loss of entropy down the black hole, would be greater than the increase of horizon area. This would be a violation of the generalized Second Law, that Bekenstein proposed. With hind sight, this should have suggested that black holes radiate. But no one, including Bekenstein and myself, thought anything could get out of a non rotating black hole." This is a subtle thing, but note how he started with the assumption that "nothing could escape a black hole". He spent years intellectually masturbating through all sorts of theory because he started with an assumption. Assumptions themselves aren't a bad thing - and in fact often lead to much better intuition since it becomes easier to understand one sliver of a system. However, my criticism is how confidently he speaks on conclusions that are derived on assumptions based on non-existent observational data. Heck, Hawking himself claims that he prefers abstract thinking over observational analysis. I am very skeptical of guys with that kind of approach because I know how a logical conclusion can be entirely false because it was based on false assumptions. Some say that this is just the scientific process at play, but I think there is something more subtle and more fundamental here. Would you base your fundamental understanding of the Universe on such an approach? Holistically speaking, I disagree with a lot of Hawking's philosophical claims, and I get extremely skeptical when he openly takes pride in circular reasoning. I've never had a problem with the holistic philosophical perspectives of all the historical greats in science. Of course, I also disagree with a lot of your philosophical claims too Makes discussion interesting though. Btw, I personally use love as my metric of trust. When two people smarter than me disagree on a topic, I usually side with the person that demonstrates a more loving demeanor, or really the conclusions that result in a more loving world (the two usually coincide). Hawking doesn't meet that criteria - not even close.

Does anyone have the actual paper related to the gravitational wave measurements? I'd like to learn more about their sensor configuration and all that.....the super nitty details, not the high level stuff. Back to Hawking - I have always found a stark contrast between Hawking and Einstein....in that Hawking is very much sensationalized and focuses on the fanciful. Einstein seemed way more grounded in reality. Perhaps that's the way Hawking is portrayed by the media, but I simply don't consider the two anywhere close to being in the same category. Has Hawking presented us with anything practical? I honestly don't know (that wasn't a rhetorical question). A quick glance through Wikipedia makes it sounds like all of his ideas have been contradicted by others? And lots of debates and challenges about things? Btw, don't forget that Einstein introduced us to the idea of "space-time" - which is to say the dimensions and time are one and the same (or intrinsically related). I've been meaning to sit down and run the special relativity mathematics to see what idea we can derive about how "fast" things were moving during a "Big Bang" or "Creation Event". The thing that surprises me is how similar the two mechanisms would manifest themselves. Why couldn't they be the same thing? I want to see what the different relativistic observation points would observe in terms of time elapsed. Perhaps someone has already conducted that analysis?

Put on your engineering cap Thebes..... Here's what the tolerance of a cap means: If the cap is rated for 13uF with a 10% tolerance, then that means the capacitor you purchase will have a value somewhere between 11.7uF and 14.3uF. A 13uF capacitor with a 1% tolerance will have a value somewhere between 12.87uF and 13.13uF. So what does that mean for your crossover? The crossover frequency is a function of the capacitor and inductor values. If you change the capacitor value, then the crossover frequency changes slightly. How much? Well it depends on the rest of the circuit. At the end of the day, the tighter tolerance capacitor is guaranteed to be closer to the original design intent. That said, the value of the capacitors are random - so it's quite possible that your 13uF 10% capacitors come in closer to 13uF than your 1% tolerance caps. It really comes down to the luck of the draw. In the case of a stereo pair of speakers, I would recommend sticking to 1% tolerance so that your Left and Right channels are more closely matched. Or you can buy a ton of 10% capacitors and then measure them with a cap meter and find a pair that match in value (one goes in the left speaker, one goes in the right). As far as the voltage. When you exceed that voltage, the caps explode into a glorious fireball. Keep in mind though that a high Q filter can see more voltage across the caps than what the amplifier is putting out. Also, higher voltage caps tend to have less dielectric losses (the mechanisms for loss are typically the same mechanisms for voltage derating). Dielectric loss is bad because it "can" cause distortion....how much depends on the topology of the circuit, the type of cap, the voltage present, yadda yadda *yawn*.

I would think the adiabatic properties of air would be the most significant whenever bandwidth is increased within the same size throat. Berenek gives us an easy calculation to approximate the distortion: % 2HD = 1.76 x sqrt(It) x (f/fc) / 100 (https://books.google.com/books?id=6UzaBwAAQBAJ&pg=PA90&lpg=PA90&dq=beranek+throat+distortion&source=bl&ots=s27fE9RBLZ&sig=1d-YD2o4-KrCOhEthnoosrJQnuU&hl=en&sa=X&ved=0ahUKEwjH-fznl9jKAhVL7iYKHdy6AvgQ6AEIHDAA#v=onepage&q=beranek%20throat%20distortion&f=false) The equation is for an infinite exponential horn, but Fc can be moved around to approximate the flare rate at the throat of a different expansion. What happens when multiple tones go through that system? Dividing the bandwidth into two different 2" throats cuts "It" in half because each throat is seeing half the total acoustic power. And is not Danley's argument that entering further down the horn path approximates a lower flare rate? A lower Fc increases distortion in this equation - and I think you gotta use the port throat opening for this equation, not the horn cross-sectional area at the port entry point. I'm calculating 1W creating 0.4% 2HD at 1kHz in this design. A 2" throat is 0.002 sq meters. Let's use 1W and assume an efficiency of 25% -> which gives It = 125 Fc = 500Hz'ish? (conical is faster at throat than exponential) F -> let's use 1kHz At 4kHz that's 1.6%....already above the level we call clipping in electronics world. Reduce the input level to 100mW and you're still looking at 0.5%. Normally I wouldn't care about 0.4% THD, but here it introduces modulation distortion since other frequencies are sharing the "same pressure". Also, cramming more frequencies at the same time through the same throat increases the total sound power. You can't just look at the level of a single sine wave. That "It" component in the equation becomes a factor in multiple entry designs whereas it's not a factor when using separate throats (total sound power is increased at the throat). I only bring it up because you're dismissing Mark for throwing away point source behavior in favor of nothing. Mark is a sane guy (for the most part, hah) and there are some equations to show that he is gaining something. Some more interesting articles on the subject: http://doc.utwente.nl/58981/1/Schurer94modeling.pdf -Compensating for the nonliearity with feedforward DSP - who's feeling like cranking some crazy math? http://heim.ifi.uio.no/~sverre/papers/2009_AES-126-horn.pdf -Effects of the rear chamber (at 99dB SPL) - maybe a larger rear chamber or a lossy rear chamber is something to consider?

A typical THD versus Level plot will look something like this: The negative slope on the left is dominated by the noise floor of the measurement. As we increase the signal level, the signal to noise ratio improves, and the THD+N level gets better. At some point, the non-linearities in the system kick in and the distortion has more energy than the noise. Eventually we get near the clip point where the non-linearities become much higher order and we see a steep increase in distortion with a small change in input signal level. I've seen systems where the minimum looks more like a plateau, or maybe there are multiple plateaus in a design - the shape of the curve is usually dominated by the architecture. Plateaus are extremely interesting when it comes to distortion because it means the non-linearity is non-linear.... I'm usually dealing with circuitry at work, but speakers have their own complex distortion mechanisms. Usually there will be multiple slopes of distortion in a design (this example has 3). The relative magnitude of distortion is level dependent, and at a system level we're seeing the culmination of all those mechanisms summing together. Everything else in your signal chain is part of that equation too. Anyways, all that to say a distortion plot is really hard to read to understand what's happening in the system. I've been spending a ton of time trying to understand how two similar distortions can sound different - a large part of that is definitely the harmonic structure, but I don't think that's the entire story either. There are time domain effects that aren't readily apparent in steady state measurements, and then there is the complexity of asymmetric source material. A very low level signal can easily be riding into a heavily non-linear region. I'm starting to think them DC coupled fanatics are onto something....

I believe the total radiating surface area increased when he went from the coaxial BMS to the BMS Mid + K69 tweeter. The coaxial diaphragms also need to deal with the air pressure generated by the MF driver showing up right in front of the HF driver. This causes modulation of the HF unit's coupling, which is a form of modulation distortion. When the two drivers are separated into separate horns, then you don't have that effect. One other somewhat related comment.... The ring radiators suffer from a distortion where the radiating surface area changes with excursion. The BMS designs are excellent in this regard, but the resultant distortion is still there. It's a minor thing, but you can definitely hear it. Moving to a K69 on the tweeter will have removed that ring radiator distortion and replaced it with all the "beauties" of the K69 diaphragm. I personally wouldn't replicate Mark's setup for my own listening environments, but I don't think it's entirely without merit.

Hmmm, I've never seen EQ increase distortion when measured at the same SPL. Are you saying the harmonics increase because the SPL at the frequency you're measuring has also increased? I have definitely seen that. As far as room / boundary gain, that has always lowered distortion in my experience. That's free energy that otherwise wouldn't be arriving at the listening position. One could argue that harmonics are benefiting from the gain too, but that would net an equal relative level, not increased. Are you keeping the SPL the same when measuring? I think this is partially why distortion is so hard to compare. What variables do we hold constant to represent true apples to apples? One of the realities of our systems is that their frequency responses aren't ruler flat, and we listen to them with these "voiced" curves. Comparing same SPL distortion may not be truly representative because in practice they won't be matched. It then comes down to which design decisions we're trying to inform. A couple dB ripple here and there is quite normal / acceptable, but sometimes 1dB can be the difference between 0.05% THD and 10%.

I was using the K31 since that's what is in the Jub LF. I was trying to do a model comparison between Jub LF and Crites K402 to see if anything popped out in your real world comparisons between the two. I have no idea how accurate Edgar's hornresp model is, and we know hornresp has its own issues too, but overall I think the model comparison is interesting. Speaking of drivers, that Crites woofer is surprisingly good at keeping up the LF energy. I've been cranking a lot of drivers through your K402 model in hornresp and a lot of them exhibit really early rolloff....even though they may model similarly in a sealed or vented alignment. I'm trying to figure out a variable to look for that indicates that kind of behavior to help narrow the driver search (right now I just pump everything into the model). I actually haven't found anything that does better in the low end than the Crites woofer (or K33). The K31 performs really well on the 12" side of things. At the end of the day the driver excursion will be the same between all these different drivers, but I like the idea of not minimizing the amount of EQ needed to bump up the low end - which ultimately comes down to power handling and thermal non-linearities. I agree with you wholeheartedly here. I've come to the point where I don't even bother with surround sound unless all the speakers are identical....including the surrounds. I think there are several factors there, but I'm with you on not limiting bandwidth solely for the sake of MD. I think a big part of that is phase coherency on sounds that pan around the various channels.

Looks like KP-3002. K48 woofer with essentially a full range version of the midrange from a Chorus II. The ceramic resistors in the xover are the first to fatigue, which will make them sound shrill with a ton of midrange. In good shape these speakers sound really good and play loud. I'd never use them at home though - definitely a PA speaker.

So whos going to bite the bullet, buy a whole set, and then get "clumsy" and require several new horns? Haha, I was thinking the same thing

Mark, by doing this, you have further separated the acoustic centers of the drivers beyond 1/4 wavelength, thus negating any point source effect that might have even partially have existed. It is that point source effect that is the subject of this thread. I'm aware that there are different tastes in music reproduction. In this case, I can definitely say that my tastes strongly diverge from yours. YMMV. Chris He's also more than halved his IMDs. I get the impression that Mark really likes dynamic music - and also wanting things to be huge and in your face like a live concert. He even stands up with a beer in hand while listening. I think there's a photo somewhere showing that Separating the acoustic centers like that is certainly going to make the sonic image "taller" or "bigger" or whatever. Different goals perhaps, but I think some of the benefits that he's getting in the tradeoff are universally experienced.

Just for clarity, you're talking about THD here? Not IMD? The 15" drivers start off with ~1.7x more Sd, which means a 12" driver needs 4.5dB more gain from the horn for matched SPL with the same cone excursion. Of course there are the motor linearity differences between the drivers too. Below are some interesting plots. The amplifier voltages are set so that the drivers are receiving 1W into their Re (the Crites woofer has a lower Re than the K31). This one shows Edgar's Jub LF model with K31 versus the Crites woofer offset on the K402: Here are two K31s as direct radiators versus two Crites drivers as direct radiators: Also of interest is the SPL of the system with 1mm of Xmax...Jub LF with K31: Max SPL with 1mm of Xmax: K402_Crites: (Note that Hornresp forced the scales to change between the two Max SPL plots.) And then 1mm Xmax SPL of the sealed systems.... K31: Crites: Granted these are simulations, but I think some general ideas here are applicable. We're seeing the expected 4.5dB difference between the 15" and 12" drivers in the sealed 1mm Xmax SPL. On the horns, the Jub LF is very comparable to the K402 at 100Hz (both 127dB). 200Hz and above the K402 is 5dB better. Below 100Hz, the Jub LF is ~5dB better (ignoring the peak at 65Hz). In terms of the loading provided by the horn, the Jub LF is providing 10dB more gain below 100Hz than the K402, 5dB more at 100Hz, and then they're the same above 200Hz. In other words, the Jub LF is a "better horn", but the 15" driver on the K402 is providing an equal excursion advantage over the 12" on the Jub LF. Theoretically we could put 15" drivers in the Jub LF (if they fit) and be 5dB better at every frequency. All that to say, I'm not entirely surprised that the THD numbers are similar. However, it is interesting to me that the distortion below 70Hz is better on the K402 system. We do see that the measurements of the khjub are ~3dB down lower than the model when we get below 100Hz. (https://community.klipsch.com/forums/storage/3/761352/khjub.PDF) However, we see a similar drop in output on the K402 model too - which seems to be a common theme with hornresp. Is the Crites woofer really that much more linear than the K31? Would impressions change if there were a better K31 replacement? It's really interesting to me that Roy said he tried this approach but didn't like the compromises. Perhaps it's a MaxSPL thing for Cinema? What else is left to measure between the two? Maybe the Jub LF intermods are better? I'd be interested in seeing a two-tone measurement with 60Hz and 400Hz since that seems to be a good range in favor of the Jub LF and keeps the sidebands within the bandwidth of the system.

Is there a reason you're considering bi-amping the coaxial BMS driver? You know there is a passive xover option for it, right? I remember the acoustic summing was so good I couldn't tell where each driver stopped/ended in the measurements, but then I'm not sure if I was looking at phase back then or not.

Ya, at that price it wasn't worth trying to make my own horn....guess it's back to the drawing board.

I think the best answer to that question is "it could". The thing is, if you EQ the response back to flat before implementing the xover, then the acoustic xover effects get nulled out and you're back to dealing with a classic filter response. You can also design the ports such that they're aren't introducing an acoustic filter near the xover frequency. Here's another interesting article: https://www.trueaudio.com/st_mr2.htm The last section talks about "constant-voltage" filters - definitely an interesting idea.