Leaderboard
Popular Content
Showing most liked content since 08/26/2017 in all areas

6 pointsFinal 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 21DS1154 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 21DS1154 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 pointsA new addition for my space, Nathan's new 21.0LX, based on the UH21 driver.

2 pointsThat would be the Katz recording, here (registration required): https://www.digido.com/portfolioitem/wehaveliftoffnowinsurround/ Make sure you get the 4.0 version without the music. The recording at the public viewing area peaks in the 120s. Of course, that's like 3 miles away from the actual launch site.

1 point

1 pointThat looks pretty decent  20Hz filter is better than a kick in the teeth and it may be a potential contender for BEQ...

1 pointI 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.

1 pointSoon 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

1 pointVery 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?

1 pointLooking at some comparisons, in the music range (above 45hz):

1 pointhttp://www.avsforum.com/forum/113subwoofersbasstransducers/2763785ultimatelistbassmovieswfrequencycharts86.html#post54824590 I bet no one was expecting this

1 pointadmittedly 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 ~1415Hz in the NF position whereas I now have a pair of high xmax 18s so that yields something like 56x 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 CEA2010 signal for that test at 16, 20 & 25, the only distortion product visible (at that ~112dB level) was 4050dB 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.

1 pointhttp://www.audioxpress.com/article/testbenchbcspeakers21ds11521inchwoofer 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.

1 pointAn 18" behind your couch? That's a joke compared to what two Skhorn's will do. IIRC, @Beastaudio is running *one* Skhorn these with together with 8 x 18s to handle the ULF. If you are using these for home theater, you could probably just plug a port or two for more extension. If you make them easy enough to remove, you could even switch back and forth depending on content.

1 point

1 pointhttp://www.avsforum.com/forum/113subwoofersbasstransducers/2763785ultimatelistbassmovieswfrequencycharts77.html#post54770610

1 pointThis is what it looks like if anyone wants to see,

1 pointI read through this article from 1982, and find that it largely covers what we know today about hearing, all was known back then. There are some things left out, such as the fact we can hear well below 20hz, and perception also depends on tactile information from skin and body resonances. The article concludes  "Future"  that performance of sound reproduction systems matches our hearing performance quite well, though improvements can be done, and that the big remaining challenges are related to acoustics and localization. The technical limitations of 1982's equipment has now been overcome  we have can have full dynamic range, no audible distortion, no noise. Back then, there were very real audible differences between amplifiers, tape machines, vinyl playback. Those differences live on in our day in the highend world, but they are no longer part of psychoacoustics, it is pure psychology. Recent advancements in audio reproduction has been seen particularly in the reproduction of lower frequencies  full range systems with response well below 20hz, and full dynamic range exceeding 120dB, with awareness to tactile sensory effects. A big, capable bass system really makes a difference. Awareness and knowledge about acoustics has improved how well a 3Drendering of an event can be reproduced faithfully and realistic. But here, we still have to choose what we can have. It has yet not been achieved to be able to reproduce an event so that it sounds realistic with correct rendering of scene and room from the recording, when you move around in the listening room. With directive patterns and early reflections removed it all falls apart when you move away from the sweetspot, or if you choose wide radiation in a lively room the whole scene is diffuse and does not render each object precisely regardless of position.

1 point

1 pointKvalsvoll, have you tried any of the Danley Sound Labs recordings? http://www.danleysoundlabs.com/tomdanleysmicrecordings/ A friend of mine who has spent many hours behind the handlebars of a shovelhead was downright shocked at the realism afforded by the recording of Donny's Harley. You could 'feel' the individual cylinder pulses from ~ 4 meters away. I tried uploading the zipped file, but it exceeds the attachment limit.

1 pointToday I listened to some albums I found yesterday, when it was too late to play at realistic volume. First some brassband music, that I would normally never listen to. But the experience makes it so captivating, I just have to listen to one more track. Is it like the real thing? Honestly, how can I know. The individual instruments are here, placed on a scene in front of me, inside a room much larger and with very different acoustics from the Room2 I am physically sitting in. The recording renders instruments and room from the recording in a way that does not sound like it comes from 2 small speakers. So, this must be a very spectacular recording, with very special qualities? Fact is, most recordings share many of those properties  individual instruments rendered with true physical size, lots of space and room from the recording. They are different  tonal balance, clarity, dynamics, bass character, room, instrument image. The presentation takes on the character from the recording. Why is it so. Room acoustics and speakers. The radiation pattern of the speakers and the acoustic treatment in Room2 together makes this. Early reflections are suppressed across most of the audible frequency range, while later reflected energy is allowed to contribute. It is the removal of early reflections that creates the clarity and separation, while the later reflections contributes to amplify the room information from the recording. To be able to move on, to improve things further, this is a starting point. How long does the ISDgap need to be, is it enough to suppress reflections below around 35dB within the gap, what about frequency range for the gap? Do we need horns? How large horns do we need? What radiation pattern should we choose? What about the reflected energy after the ISD  how strong, how fast should the decay be? Then there is transient response. We often call it dynamics, but that is strictly not the same as being able to reproduce percussive instruments with realism. This is where, in my experience, all typical hifispeakers fail most. A bigger speaker, with more capacity and more directivity control, with drivers that has much better transient response, is in a different league. In this context  how do we compare and rate speakers. How can we set up a controlled (which implies at least blind) listening test to evaluate and compare speakers. It may be necessary to do tests focused on a very small subset of properties, so that a complete evaluation needs several listening tests, which then after can be combined to make some kind of overall measure of sound quality.

1 pointYeah, that one is a mess, and it has almost no deep bass either. What's causing all that clipping are transient "crackles" with enormous bass energy that extends all the way down to the single digits. The above recording doesn't capture that at all.

1 pointI'm back to work on plans for a single driver version of this. It's going to lose 6dB maximum output and 3dB sensitivity of course but I think it'll be ok. If I chop this cab exactly in half it would be a 24x27x32" enclosure. I'm thinking I might upsize it just a bit to get a little more vent area and airspace for the driver. Perhaps 24x30x32 or I might go all of the way to 24x32x32. That's still 4" smaller in 2 directions than the Othorn. I'm debating on it because the smallest size / weight possible is a big plus but so is maximum performance.

1 pointThis statement sums you up perfectly, and is probably why you find so much contention on countless boards. In this hobby, subjective preference is everything. Neither you nor anyone else can tell someone what they should like in their system.

1 pointIt occurred to me why aren't active bass cancellation techniques employed more? A driver or 2 in the right spots tuned to target and absorb or cancel excess energy could be very effective.

1 pointOh damn that's just what we need! A few pebbles scattered about the room. What are we thinking with bass traps, measurement systems and modern dsp? Simply strategically place a few minerals and instantly get that last 1%. Only $99 too. What a steal.

1 pointI've been wanting to weigh in here for a while but have been busy. First, I think a halfspace to fullspace transition is very unlikely. Second, THD vs. excursion is not constant at all constant with frequency. THD during sine sweeps is a consequence of nonlinearity 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 nonlinearity 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 nonlinearity 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 oddorder 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 rewritten 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 2550 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 nonlinearity 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 backEMF 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 nonlinearity 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 nonlinearity 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 nonlinearity 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 xaxis is what might be called reduced frequency. It's the ratio of the frequency to the box resonance frequency. The yaxis 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 rolloff 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 nonlinearity. As such, it's not entirely clear that lower Qts = lower distortion as far as Kms nonlinearity 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 xaxis 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.

1 pointM, As you've discovered, the Aud mic needs a preamp. As you've also discovered, the C weighting needs to be defeated. What it looks like the problem might be is a high noise floor at low frequencies. Try raising the level of the sweep to 105dB or 110dB with the close mic measurement and see if it changes when exceeding the noise floor. This is a good practice anyway when measuring subwoofer range frequencies. BTW, the AVS thread that showed the Aud mic to be accurate against other measurement mics was BS. I measured it against my ACO Pacific rig and it certainly is not accurate. Common sense should tell you that a 50 pence mic is not as accurate as a 1000 guinea mic. The Aud mic starts to roll off at 30 Hz and is down 10dB by 5 Hz, assuming a good mic preamp and power supply.

0 pointsI 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