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radulescu_paul_mircea

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About radulescu_paul_mircea

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  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 ?
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