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radulescu_paul_mircea

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Everything posted by radulescu_paul_mircea

  1. Improve collateral heat transfer from the coil directly to the environment instead of coil to magnet assembly. With M-FORCE is really easy, but with a moving coil, it is really complicated. I really like a more open assembly, like those made by the car audio sub manufacturers. DD Z series comes to mind. Add a cooler and you're done! I own 2 Ipal modules. They are powerful and really good match for a 21Ipal driver. One could get the other into thermal limit of either one of them , depending on situation. The DPC sensor position has to be in the Apex of the horn
  2. In my SKhorn XLs I put them on the inside, to keep the design . They are absolutely needed in pro use, I found anything from sweaters, bottles, shoes, screws to napkins, purses and all kind of things inside
  3. http://www.atelier-der-tonkunst.de/produkte/pol-ddi This is the link to the product. Really good and very low distortion. Capable of taking 200 Vrms at under 1% THD is super useful. I tested it for limiter settings and it works as it should. I will try to get my hand around on how to use it for live Impedance monitoring. That would help me a lot
  4. Found a solution. Instead of using an oscilloscope to look at the voltage, I got a device with -40 dB of voltage gain reduction, with galvanic separation to be used directly with a sound card. I can now use it to get measurements for sound output in paralel with voltage output. I can even use the output of the amplifier as an input reference for transfer function of the speaker alone, with any nonlinearity of the amp eliminated . But I can also measure the amp dynamically, in use, which is a nice feature
  5. This cabinet is tricky. The sound is absolutely stunning, but the thermal behavior is not best. It is best used in a low bandwidth and techno is to be avoided. Even though a dual 18TBX100 sub is from -6 to-10 dB in maximum output compared to my dual 221 Ipal Skhorn XL subs, half the dimensions, on techno the are as loud when limiters intervenes. They do not sound nowhere near as good, but they are quite close in output. This is because the impredance minimum from 45 Hz to 85 Hz is dead centered in the band where that kind of music is centered
  6. He's K10 doesn't have DSP I suppose, otherwise why wouldn't he use the internal DSP? In a SKhorn or Skram subwoofer, with 8 or 4 ohm drivers , one wouldn't have to use a peak limiter with any amp except K20. Engage clip limiter in K/X series or soft clipping on any other amp and then use a really long term limiter. If the limiter is not a gain reduction system, but a normal limiter, take care with the voltage values , because if there is more distortion than it should, it will increase the average power and decrease the crest factor. A 21SW152 coil without moving can get burned even with 200 watts ( meaning continous current or sines at frequencies where excursion is really really low. In use, you can use 500 watts as an excellent protection strategy if you don't stay in limit permanently.
  7. I am reposting a line of comments I made about this subject on a group on Facebook The limiters are very safe but you have to take care! I use the clip limiter as a 0 time attack, infinite to one ratio peak limiter, sometimes I let soft clipping disabled. This is a voltage limiter and it should be set a bit higher than the peak power of the speaker, or about 6-8 dB over AES RMS power. You will have to use V=✓(P*I ) to find what voltage you need. Next, the peak limiter is set with a time constant high enough to let the transients pass without problems, but low enough to protect the drivers from over excursion. Take notice that this is working as follows: if a signal is stronger than the Threshold, the limiter is engaged instantaneous and the attack time is the time it passes until the signal is reduced from it's original value to the Threshold value. I am setting this one with a time constant =1/2 of a single oscillation at the frequency where the excursion is the greatest in the bandpass. So if the excursion is max at 50 hz, I put 1/50/2=10 ms. Some are using the frequency at the loads but sometimes this is not good because for example in a reflex enclosure, the peak excursion I'm the octave above port tuning is exactly one octave from High pass frequency and this means it will let it go over once before engaging. The release is a multiple of the attack , 10-20x for lows, 4-8x for mid etc but you'll have to play with it cause it will sound good on some types of music but not on the other... The voltage for this one is based on the way the driver is loaded in the enclosure and the maximum excursion allowed, but if you don't know that, you'll need to put it between 3-6 dB over AES power.. The TruePower setting is for thermal protection. Depending on the type of music you are playing the settings are different. For long duration bass lines ( dubstep, trap etc) , put 1/4 of the AES power with a longer time constant, soft knee disabled (3-6 seconds atk, 12-15 s release for 4.5 " 1700 Watt voice coil) .it will be louder for longer but then it will limit harder. For techno, trance , dnb etc, you need to put a higher threshold 1/3 - 1/2,5 but with a lower attack time (0.5-2 s atk, 2-4 s release). It is important to know that the limiters are safety nets, not meant to be engaged all the time. The are there to save your equipment when a part of a song is a tad too loud, or you need a moment where you increase the level for Dynamics. But if they get engaged all the time, you need more equipment. The gain topology you choose has to be set so the limiters are not interfering with the music too often. The TruePower limiter is a setting which is using the real power transferred to the driver by measuring the real voltage and current ( disregarding the reactive part) so it has to be set in relation to the number of drivers linked in parallel on the same channel. If you have a 1 KW AES driver you will set it at 250 W, if you put two of them on the same channel, you set it at 500. The peak limiter is a voltage limiter and it is independent of the number of drivers linked in parallel. The same applies to Power vs V@ 8Ohms. When I am setting the TruePower Threshold, I am usually also measuring the magnet temperature and voicecoil reference impedance and I try to keep the temperature rise under 150°C and the magnet under 80 degree after 2 hours of low crest factor music. Another thing I am doing sometimes , especially when I have the time , space and conditions (so not many times now) is to measure the acoustic power a subwoofer is generating. I am putting pink noise in band with all filters and processing activated and I turn the gain until the TruePower is measuring 10-20 Watts on the output. Then I measure the acoustic power of the device with a method , I compare it to simulations in Hornresp and Akabak and I calculate the Input/Output mean efficiency. If it has a mean efficiency of let's say 10%, I'll add that power to the True power Threshold , because that energy will not be transformed into heat ,but in Sound. Another thing is that when you couple more subs , they increase in efficiency so less power is turned into heat. This means I can increase the threshold once more. I got my hands on a some Klippel LSI reports from some drivers made by some well known manufacturers and there Delta Tv is the voice coil temperature rise from base which can get as high as +180 °c . So the drivers voice coil temperature can easily get to 200° C but not the magnet's temp. That one I like to keep it under 80° . If the temp is of the coil is kept under 170 ° at all times , the Re of the driver is kept under a certain variation and the power compression stays under 3 dB . There is something I would love to see more in the processing units: a limiter with a frequency dependant Threshold. A limiter with an output Threshold and given attack and release constants that are not engaged ,even if passed, if the frequency is not in the right band. Powersoft does have this, I think Linea Research has something similar and I've seen this behavior in Eminence D-Fend. This type of limiting is letting one to better protect the drivers from over excursion in subwoofers. If you know the impedance graph (which correlates to the excursion vs frequency) one can set the limiter to trigger earlier in a certain band. In the previous example, a reflex enclosure has its second impedance peak at 50 hz, where the excursion is the greatest, the FS is at 38 and at 33 is where we need a crossover to keep the excursion under FS at the same maximum level as it is at 50 hz. If there is this type of limiter, we can increase the crossover frequency and we can put a higher sensitivity/lower threshold in the 50 hz band. If the amp allows it and the driver doesn't melt, one could increase the level in the rest of the band a lot. Off course, the frequency response equilibrium would be a problem but that would be another topic. This same type of limiter helps the Powersoft amps to be louder and safer than anything else on speakers with passive crossovers.
  8. Try and limit your graph axis to 10-300 Hz and 45-115 dB. It will show us better details. Do you have a way of measuring the Impedance? Maybe create a Google drive folder to share the measurement data from REW. When you save the data, you can find it in your computer and you can upload it to a shareable folder in your account
  9. A K10 is able to deliver everything a pair of 21SW152 per channel can take and them some more. It will burst more than 8.5 Kw at 2 ohms , it will sustain 1600 w for longer than the driver's can take it. So for sub duty, K10 and K20 are the best you can find anywhere on the market. Take care with the DBX limiters , they work a bit different than people are used to and the drivers could suffer paired up with a K10. Moving the prolites on the tops will be a good choice. Take good care with limiters, the peak power Danley is suggesting for those enclosures is a total calculated sum with pink noise.
  10. Caution! "This image contains large amounts of beef!"
  11. Well, that settles it... the far grater excursion capability and lower power compression than any other pro driver except 21Ipal. The Copper coil has less thermal inertia because speciffic heat is half that of alluminum , the efficiency is a bit lower than Ipal because the magnet is not as huge, but the normal impedance is high enough to use 2 of them easily in parallel on a K20 channel or even X4L with extreme results. This RCF LF21N551 need to be tested by you @Ricci. It will really surprise you!
  12. It seems that 21ID can take a tad more thermal input with a bit less power compression than 21NLW9601. 20% more power and 1dB less power compression. But it has higher distortion doing that, something I noticed. We need 21NTLW5000 tested here for a complete package
  13. Thank you @Ricci for the response. I didn't get the phrasing right, because in fact I know the results are good and verifiable. What I wanted to know in fact is if we could make a correction curve to get the amp out of the way completely, or a variable compensation curve. I am thinking of using a Rigol oscilloscope to record voltage and current over time in sweeps and then create a power compression file to add to the measured response so that the only result is the drivers PC.
  14. How can we verify that the power response and compression for the loudspeakers tested on DB are really correct if all of the amps limit way before 23 seconds sweeps used ?
  15. GP in which enclosure? The single sealed? Or did you managed to try it into Skhorn?
  16. It seems Eminence went for a different chassis. The old one probably was too similar to those from B&C
  17. It does have over 3 dB higher sensitivity at 1.41 V across the band from 28 hz up, 1 vs 1 but it doesn't get a lot more maximum output, at least not between 28-45 hz. The Ipal drivers can take +4dB more power so they compensate.
  18. Good work guys! Attacking the subject from so many angles. Regarding a piston in a sealed enclosure. It will never be a good Idea. The efficiency of a piston in an infinite baffle is dependent on the force^2* SD^2/ MMS^2*Re and some constants in the fraction like speed of sound and density. This means that any increase in force squared/mass squared will give an increase in efficiency. But also having bigger radiation surface. Also, there is a relationship between mass and reactance which will change the behavior quite a lot and will make the system non linear. So a hugely powerful piston would be very good only if attached to a huge light weight surface and an amp made for constant current instead of constant voltage to be able to properly work with huge reactance. But a horn system is a way of making this behavior change. Higher compression ratio with long enough path and big enough mouth will improve efficiency and could make use of a higher force. But at the cost of quality, having higher distortion and nonlinear behavior, like power compression, mechanical noises. I feel that for pro audio and my own goals , a dual coil dual 21Ipal enclosure, with 4 times the thermal capability and twice the excursion, with an amp capable of delivering enough sustained power for enough time in a 150*100*70 cm enclosure, tuned to do 30-150 hz full and flat, having 3 dB more than Skhorn XL with K20 bridge maximum burst output at 50-100 hz and 6-8 dB more from 50 hz down. This year I was able to play with Danley BC218 . They were stunning, fully flat and hugely powerful from 26 hz up! More output than my pair of Skhorn XLs, cleaner, deeper, less compressed, huge directivity. They are made with good but normal drivers, 18SW115 so we can see here how the enclosure contributes to the end result as much or more than the driver's capability. But way too big for anything else than a huge stadium or a funny outdoor festival. And if a better driver was being used , the enclosure would be better? If the answer is yes, how much could you increase the drivers performance until you reach the limit of the enclosure?
  19. Graphene drivers already are out there. MAGICO is using them.
  20. Are you talking about TH50, aren't you? Those were my thoughts also
  21. I have noticed you said about using a "8002" amplifier.which one is that ?
  22. I will state my idea of this "perfect" pro audio driver for the most powerful subwoofer one could make in a given volume. The enclosure volume is maximum 1000 liters, weight is 175 kg max, frequency response should be -6dB at 25hz and +3 dB at 120Hz from the 40-50 hz output. This driver might already exists, but it is not readily available, it is the 24" driver from the new Funktion one F124. It is dual 8 ohms 6" coils, BL is 50 Tm but that is the only thing I really know about it, I didn't even get the chance to hear it. But now, going back to my idea of it, I know that any driver will in fact be just the engine part of a sub and it has to be matched to the enclosure for really good performance. Also , some of the qualities I will state about that driver might be negated or might be improved by the specifics of the enclosure design, but I will still play this game. The best driver IMO is always big. This means heavy most of the time. A 21-24 inch driver, with dual 8" diameter differential drive 1 ohm coils each. Length of each should be 70 mm , copper clad alluminum or just Al, flat wound ribbon wire, with inside and outside turns. The coil former made from a better conductive material than fiberglass and also a better thermal inertia, I am still searching for one with similar hardness/density with those properties. magnetic gap should be 30 mm, but with the proper extension on the pole pieces to decrease magnetic losses and to keep the magnetic lines perpendicular over the coils for the whole length. overhang should be 30 mm a side plus 10 mm the other, giving it a perfectly flat BL curve for the first 10-12 mm for maximum impulse response accuracy on the higher end of the spectrum, but this will also give a lot of excursion capability, good low end response and also cooling. This means it will need a smart magnetic circuit design, and the way the guys at Digital Design are doing it looks like a winning strategy IMO but it could be improved. Using radial magnets on the inside and outside of the coils, fixed in place by iron bars in anodised alluminum casings on the faces opposed to the coil (inside and outside of the motor toroid with the coils in the center), but with iron pole pieces shaped for conducting all the field perpendicular to the coils, The bar design with the visible coils are making the cooling easier if smart port positioning is used, and from the inside, there are a number of ways one could use the diaphragm displacement to cool the coils. From my calculations, about 6-8 kg of neo and 12-16 kg of iron and 2.5 kg of anodised Al would be needed to make it close to the M-Force motor strength but with way lower Le/Re. It will have much lower thermal inertia and it will still be harder to cool down, but the lower moving mass would make it more efficient. Diaphragm made from a laminated carbon fiber/aramid honeycomb/ carbon fiber sandwich, low mass , huge strength, W shape with the dust dome and cone in a single piece. The centering of the driver in the magnetic gap could be made with a spider separation ring that could be screwed into the chassis directly with all the parts already glued, like A&D Audio from China is already doing. Spider materials and shape should be similar to that of the new NTLW5000 drivers but probably at 12-15" diameter for enough excursion, dual layer separated by a ring with enough distance to ensure the very long coil stability. The total weight will be somewhere between 30-35 kg if the whole chassis is made of aluminum, encasing the whole motor like Faital pro are doing with their drivers. I would make a single driver enclosure with this one and it would finally satisfy my stupid wishes. With smart cooling it could take 2.5 kw of real power indefinitely with 6dB pink noise in band inside the enclosure with all setting needed. It might still not be exactly where M-FORCE+M-DRIVE are, by using a 30" diaphragm, but not too far either. What's your opinion?
  23. The ports are the corner iteration from their own 2*15" version, the VTX V25. I've seen that one in real life and I've heard another version of the VTX with single 18" driver, but with their nice dual flared tubes and they really really work way better than a similar surface square vent. I bet they went for a higher motor force , higher moving mass with lower Q, increasing sensitivity on the upper end.
  24. Looking at the cutout of the 2269, it seems that the design for NTLW5000 driver is pretty much the same. The pole pieces are the same shape, the magnet inside is single 2 cm thick ring of about 4" external diameter with a center whole inside of 2 cm, meaning about 1.1 kg of neo. The external metal ring is also closing the magnetic circuit, but not having a similar heat sink, it might not dissipate the heat as well. All my tests show that the driver behaves absolutely stunning up to 50 mm peak to peak, after which it starts to become noisy. Klippel results show flat BL until +-10 mm, similar to that of a split coil design, but then it dropps with a very low slope, remaining at 75% at +-17.5 mm.
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