Been talking with a few guys about a thread for whatever audio/video related discussion happens to be the subject of the day. Bass traps, how to design a FLH, the state of 4K video products, amplifier/speaker matching. Whatever.
Here it is.
I'll start off with some points I wanted to make related to discussion in another thread that is getting way off topic. Each one of these subjects could be its own topic.
1.) Winisd or other modeling and simulations. Bench racing with questionable small signal parameters and highly incomplete or inaccurate sims. We've all seen it. It's all over the place at many forums. Has been for years. People base buying decisions on it because they don't know any better. Has jack to do with reality usually. Totally agree. As Bosso said driver in hand / in cab with measurement equipment is required to know what you really have. I said my piece on this years ago, a couple of times. I've had people tell me the measurements must be wrong because their simulation doesn't match it. LOL. This is a BIG part of how I ended up doing the testing to begin with. I started doing measurements and realized the simulations I and others were doing were fantasy land. Started with multiple old car audio drivers I had and trying to DIY a few successful builds using them, which mostly failed utterly to perform anything like the sims. That was beginning of the rabbit hole for me, after realizing that the TSP's and a quick sim do not predict what you will get with a manufacturers driver. Basic TSP's are inadequate to simulate modern, large coil, long throw drivers in most cases and most any driver type at high output levels. Power handling and xmax specs are all over the map. This is why I started buying and testing so many different drivers. Can't trust the specs or sims. Got to verify it myself. Might as well let everybody else know while I'm at it and help the other guys like me out.
2.) Klippel: It is not infallible. I have talked with a few different people in the industry who have said that the setup for a measurement can be screwed up quite easily. It can give data that is not accurate due to setup, operator or equipment errors. Now I'm not saying that has happened in any specific cases because I don't know of any for sure. I am told it is possible though and not that hard to do. Like anything else don't just assume.
3.)There has been a few remarks about not knowing whether the driver was pushed to the excursion limits during the max long term or burst tests here. EVERY driver has been. There is no question about this. The burst testing is only stopped when there is a clear indication of driver distress (usually mechanical noise) in the deep bass or the amp runs out. Below 30Hz the amp never runs out. The one case was the XXX overhung coil. The amp clipped right about the time the driver was done anyway. This was because the suspension had tightened dramatically and the motor had lost a ton of force with the coil that far from center in an undersized box. Same thing with the long term testing. That test is almost always stopped by driver excursion and bad noises indicating mechanical limitations are imminent. Severe thermal compression in the upper bass of 3dB or more is another good sign to stop but this almost always occurs at a point where the driver is out of excursion anyway. The CEA-2010 data may not be the maximum output of the DUT. That info is also available for nearly all systems though under the static charts section. The numbers in red are the maximum level attainable by the device limited by driver excursion. In the case of the XXX you could mount it IB and it will never put out more than about 111dB at 20Hz same as in the 4 cube cab. Power required will go way down as would distortion but that is the displacement limit. It is not going to put out any more maximum SPL in the deep bass. The 2-120Hz sweep used for the long term test covers the entire bass FR. While you may see slightly more output from a system with the CEA-2010 or MAX bursts broad band there will usually be one band or another that is very close. Note that the bursts are 1/3rd octave spaced. The sine sweep covers every frequency in the bandwidth and it will find the worst case frequency for induced driver excursion in the sealed cab. It may be a very narrow small area, but if the driver threatens to blow apart or smash itself to death there, that becomes the voltage limit for the long term testing. If the driver coil doesn't melt first of course. Some drivers like the XXX this occurs up near the impedance peak at 30Hz due to the high qtc and resultant excursion profile. Others such as the 19 with a very low qtc in the same cab are limited by excursion at 10Hz or lower rather than 20-30hz.
4.) Long term versus demanding music program material: DIYSG I have seen you and another poster make a few posts here and there about how the 2-120Hz sine sweep long term test signal here is not that demanding and how some demanding music material could be worse. I disagree. It is not as demanding as say picking the absolute worst frequency for heating the coil and dropping a square wave there, but it is much worse than almost any music content I know of other than a few fringe bass tracks or something that just happens to be sine wave like into the impedance/excursion minimums. As explained above this will hit the imp/excursion minimums every time and drop significant power. If you look at typical impedance curves and tunings of bass systems and consider the high and low pass filters involved, etc...Most music is above 25Hz and will have a high crest factor comparatively. The tracks that do have sustained sine like bass tones are almost always in the 25-50Hz octave. (I recognize outlier tracks such as Lone Survivor. I'm talking 99% of the rest of it.) Impedance is typically high over some or part of that range. The sweep signal only last 23sec roughly then it is over. Yes you may be able to kill a driver with the same voltage run for 20min solid with a music track on repeat but if the sweep continued on repeat the driver would die much quicker. That's why it is considered to be an accelerated thermal test as well as judging things like compression, excursion, vibration and mechanical noises. Comparing it on paper is one thing but running that sweep through a system pushed at the edge of its capabilities should remove any doubt about how demanding it is