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radulescu_paul_mircea

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Everything posted by radulescu_paul_mircea

  1. Because I have the job to check sound systems in different venues, I often check the subwoofers at high volume to see if there are any problems. Most of the times I use protection, sometimes even earplugs and headphones on top, but there are times when I forget some of my equipment and i have to do it without protection. I can tell you for sure one can have really big problems with his hearing after checking a stack of 4 double 21" subs, flat to 26 hz, for a few minutes. even with my ears covered with my hands, sometimes I feel my ears hurt and hurting is never a good sign. So yes, bass can damage your hearing!
  2. I want first to know what is the audible spectrum of humans, ear and other senses. I cannot find any new study where they test the auditory system capacity , to get rid of 20-20k Hz , to make a difference where the cochlea stops functioning and other sesory inputs tend to be more important in the perception of those frequencies. I have a professor that states the ear stops functioning at 200 hz hand hands over to other sensory inputs. I know he is not right but I have to proove him so if you know of studies please link them here. Paul Edited: This is what I found up to now http://oto2.wustl.edu/cochlea/romesalt.pdf
  3. Post anything you find interesting about acoustics, hearing and audio reproductions. It can be any type of study new or old as long as it is veridical and it is not common knowledge. I mean we have to keep things interesting.
  4. So taking that much power even in a very high efficiency system the heat will accumulate very fast. Using the metal wings attached to the motor one can increase the heat transfer but it is not as efficacious as forced air. And using the TruePower counter from Powersoft K10 generating around 1.2-2 Kw per channel drawing on average 3.1 Kw from the wall, to see how quick and how high 4 BC 18PS76 per channel will heat up, in 45 minutes of bass heavy music I ended the test because I got around 35 degrees Celsius increase. So putting only that power in 8 vented drivers I could get that temperature increase. Now imagine 2 KWh in a single 22 kg motor.
  5. I believe the problem is the lack of active cooling . In a normal driver the moving of the coil creates air currents and that exchanges the heat between the driver and the medium but here they use only convection. In the F32 from Funktion one I believe they use the driver as per the image attached with a small chamber of air and in a horn enclosure using 8 of them which behaves more like a full horn.that raises the impedance for a good bit. The thermal inertia is very high so even though it is hard to increase the temperature, it is also as hard to decrease it . The M-Drive can generate around 5000 watt long term and 2000 watts thermal equilibrium so in 2 minutes you increase the temp with 20 degrees Celsius
  6. Here is another sub using the M-Force/drive combo. Cool looking, fairly compact and probably LOUD. I wonder if it is a bandpass, transmission line or a TH...
  7. I wonder if that app also takes measurements like the Elac one?
  8. I am now playing with these babies and I have a SVS fan client with 3 Ultras installed and we listened to both of them for days now. He will probably end up buying the speakers but also will probably be the first PB16 client. As for the dimensions, could the 16" be in fact an 18" but measured only from the suspension edges?
  9. From the image there it seems its ferrite magnet. The spider could be good enough. It doesn't look to be 15" ,more like 12. But when you look at the Ipal driver's spider you can see it is not that huge but it can allow sufficient excursion and control for the application.
  10. Hi guys, It appears to me that Ricci has another cool sub to test. https://www.svsound.com/products/sb16-ultra 8" edge wound voice coil ! That said something!
  11. I don't like to hijack your thread, cause it is not related to testing procedure you use, but this datasheet has some serious measurements and they even describe whats signal they used http://www.audiocore.co.uk/wp-content/uploads/2015/10/APA-Detailed-Power-Specs-Jan-2016.pdf It deserves a look at least
  12. The room is 4*4 meters in an apartment building. The level I can get with those subs is formidable, using the amp bridge to drive them both but I took out one of them because it gets scary very quickly and I stay with rent :-D With some processing I got flat from 21 hz, and I try not to exceed sane, normal levels
  13. It seems now I can also put my system list here: -2 monitor audio rx2 -2 xoc1th18 with 18SW115 -1 Teac AR-650 -1 Crown xls2002
  14. Hi, I wonder how this looks inside? It uses Ipal driver-amp combo on the active version. I appeared around 2008 but never heard or seen one. I wonder if it has a bit of horn in one of those vents? the numbers and mumbo jumbo marketing doesn't reveal anything, a graph would show us much more http://www.outlinearray.com/images/box/lab21/lab21.pdf
  15. I would love to see a clone tested this way
  16. As with the hatches, they would need to be as big as the diaphragm on her side. The other parts would come after. One can make the driver "basket " as it feels suited so it can be build from wood or custom Al or steel parts from the beginning,mounted inside and then trough the hatches to put the other parts.in fact, the membrane could be punted trough the horn, with only small hatches to screw it in place. Because is modular, it is much easier.
  17. I would have a way to get my hands on them if I can get a sponsor here.I would probably need to build 10 to get past some minimum requested order if I decided to do it but we have a good distributor here with a good reputation in Powersoft company that could get them for me for tests. The price being what it is, it's also a barrier.
  18. The processing is a must in this design. As you probably saw I put the amp resistivity at 0.03 Ohm and that smoothed the response especially at port resonance. Probably that is the correct way to change RE in the adaptive parameters and sim it in HR, without having to calculate the parameters if I would change the driver's. The Xmax of the driver is given by the linearity of the motor force and of the magnetic suspension but even if the motor has only 30%force at 25-30 mm, it still has over twice the power of an Ipal driver. But not just that. The fact that this driver has a very reactive load, it stores a large amount of kinetic energy. The amp will deliver a HUGE current at the start of the motion ,then less is needed to keep it going. At the end of the stroke, the DPC processing will tell exactly what signal to generate to stop it because the magnetic brake is very strong at large excursions, so again, the energy consumption is much smaller than in a normal driver. It wil not hit 35 mm but it will be close. Also, it is quite immune to nonlinearities even at those strokes because of that magnetic centering. The more it exits the 0 point position,the more powerful that centering gets. In one of their white papers they compared a single 30" short transmission line vs a dual 18 and they measured up to 147 dB at 40 hz or so,and when I tried to see what the excursions would be needed, the number is huge! It is a large enclosure but if a contractor has to use 4 of these instead of 32 of another brand it would be in fact quite compact! Another cool thing about this system is if you simulate multiples (2,4,8) in HR keeping the amp res at 0.03, it will not scale as it shout, but if you then change it to 0.02 or 0.01, then the response improves.I bet the DPC system would sense the boundary change and would modify the damping accordingly.
  19. Here these dudes say they use 13 Kg of new N48 on their single 32 sub, 8" voice coil. Sick! http://alphard.audio/general/product/id2793
  20. It could also be made smaller, a lot smaller because of the possibility of changing parameters, but it would then use smaller vent and it's main purpose is efficiency down to lower 20's, so no compression is allowed. Look at the F132 from Funktion 1 and there you will see how large a horn has to be to get those numbers with this driver
  21. I was thinking about them being to big, but that is the size of a BC218 from Danley. They are not that practical, but they as fun and interesting and it get people impressed. It could probably cut in half to be more manageable.
  22. Damn, the design is cool to work with if one has the right drivers. I know probably now I sound like I am trying to promote the M-force design (which I am not) but for now, in these types of applications, I cannot find something to beat it if you know how it really behave in use. Using a simple fold like the one in the picture bellow, in large box, 60*60*35.5 " (not quite double the volume of the MAUL) one could put 2 M-force with custom 34 " drivers.Why custom? Because they produce this driver with whatever parameters one wants, even diaphragms with SD up to 6500 sq cm made on specs. The vent would be tuned to around 21 Hz so the efficiency would get much better. Also the vent surface would be huge so the compression would be reasonable even at huge SPL. The port inlet could be guided so the air flow to be right over the motor assembly so that at very high power levels the turbulent air would cool it down. Also, the driver has a very large inertia and an Xmech of 35 mm and right over the port fs, one can use a bit of eq to flatten out the FR, easily with only a small amount of power asked from the amp. Considering also the DPC tech, the distortions and accuracy would be fenomenal. Because it would use only 2 M drivers which weigh less than one RF T3 19, Using 18mm Ply and extensive 15mm bracing, this would weigh around the same as a single MAUL, but would output the same as 2 of them from 19 hz up. then, if you add the cost, a driver + module is around 4.5k, so the factory retail price for an active would be around 12-18 k. 4L-acoustics KS28 with amp would be north of 30 K and this would be smaller and would go 5-10 hz lower. Cool for touring or instals, even for pro Cinema's.
  23. Keep up with these test! Your test, Ricci's and some others from the DIY community helped me to convince a client to get the best possible. I know it is not directly related with Luke's measurements, but I wanted to share a review with you about the Powersoft X4 (and for X8 at the same time, being 2 of htem in a single package) http://www.powersoft-audio.com/en/docman/1012-x-seriestestrevieweng/file That is a resonably way of review-ing amps IMHO
  24. In a sealed burst test, I think other important factors besides excursion and thermal compression,are the break-up of the diaphragm, the softness of the adhesives and other small factors that doesn't have an effect at small signals but once you push ove a threshold, those effect starts to accumulate with other nonlinearities.
  25. The Alpha B3 sub is an already obsolete product from that brand. It's a company known only in Europe, more precisely Germany and Romania. I don't know the correct term for the alignment but the sub port is inside that straight horn. Big, heavy and expensive kicksub. Nothing under 40 hz really,because of drivers with only 7 mm xmax
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