radulescu_paul_mircea

I have a version of SKHorn that is larger than the original, it's extremely close to a pair of Skrams in dimensions and it's loaded with a pair of 21" Ipal drivers. I tested it with CEA bursts and recorded the max level of a few more subs, including TH118. Usually, the tests were done with a bridged K20, an ISEmcon mic or earthworks M30, at 4 m and every time the system was calibrated with a B&K calibrator. 2*TH118-8ohm versions on a FP14000 bridged 25, 28, 31.5, 40, 50, 63, 80 Hz values 116, 130.3 , 132.0 , 135.0, 136.3, 139.4, 140.2 dB at 2 m You can compare to SKhorn measurements from data-bass and you'll see it's just about the same level difference as the difference in drivers and enclosure dimensions, meaning about 3 dB overall. You loose that when you go for a more normal 21", but I gained about 2 dB from the larger enclosure in the deep end and larger ports, which I believe will be the case with SKrams. That's the thing, they made the TH118XL that can get you about 6 dB more at 30 hz compared to the smaller version, at the expense of the max level at 45 hz where you get into excursion limit. I believe a Skram loaded with 21DS115 or similar will be a bit lower in output at 30 hz and on par everywhere else wtih TH118XL. another very important aspect is the fact that the sound is so much different! Tapped horns have an extremely clean sound at LF tuning, they have so much more surface than a port so they tend to be cleaner down there , but they don't feel as tight and as punchy as BPHs . in my experience, for very deep bass music, I tend to like TH a lot more, they can keep up better with heat and they sound so smooth! Very large horns are even better, like BC218 but those are just for installs IMO. For all-round use, I'd go either with my dual 21BPH or with simple well designed reflex subs. because right now, reflex with L-Ports like L-Acoustics , but loaded with NTLW-5000 series from eighteensound, tuned to 27 hz, is something one should hear to believe!

I finally got my hands on this driver. The coil is so huge , the wire thickness seems to be 0.45 mm and 4 layers, it's coil is twice the wire amount of B&C21Ipal (of course, not the same efficiency) . It will take loads and loads of power. The excursion reached is probably over 8 cm peak to peak in this video, using a K20 at 16 hz

I believe you will always get a smashing win when going diy vs commercial bang for buck! There's no competition. I went that way too. You need 3 SKhorn to meet 2 BC218 over 30 hz , but under 30hz it will be more of a 2 to 1 ratio. If you went lower, the ports would need to be a lot bigger in length and noise would go down. f132 goes just up to 60 hz. The new Powersoft designs go to 100. I think best bang for buck is SKhorn, best smashing output density and wow factor is EDMSub from Powersoft with dual 30" drivers , which is 2 or 3 times more powerful long term than 1 SKhorn. Ipal drivers don't go that low even though they are beefed up. Eminence is a bit better that low because of the lower fs IMO

Hi! I have some questions for you before I can answer yours. First of all, where are you from ? What is the main purpose you need these subs? Rental, Live events, DJ, club, or home use? what type of music are you mostly working with? yes , I heard BC218 , a pair, they are tremendous subs! But very very large. Really full power at 25 hz I also heard M-Force drivers in F132 from Funktion one and some prototypes from Powersoft before launching. F132 goes as low, at 25-26 hz if I would compare BC218 to F132 I would say they have the same extension, same cleanliness, but F132 is louder and BC218 goes higher,it's easier to integrate without kicks . SKhorn is not tuned as low in native mode. Tuned at 30 hz, the ports are pretty noisy, but the sound is really good. I felt like the sub could benefit from a larger enclosure with larger ports and a bit higher tune, at 32 hz , and that's why I chose to make it that way. In essence it's the same sub, if left at 29 hz tuning, it was maybe 1 dB louder which is nothing. I would go for the original design. If you need it for dance and techno etc, then larger is a bit better but not worth the added weight and volume. but when used with 1/3 of the port closed, it does extend as low as the other two. I think BC218 is 3 dB louder under 30 hz but infinitely more clean . F132 is probably 6 dB louder or so and probably even cleaner. min skhorn I tried lots of drivers, best was RCF LF21N551 but that's not available anymore. I liked it more than 21Ipal, similar power but sounded deeper. Next choice would be Eminence. the new M-Force designs are promising but they are pretty much same as a dual 21" sub, except of EDMsub with dual driver. That's a malefic beast

I was just wanting to post it! They've been working on them for a while, changed the motor a lot

Yes, it happened to me with B&C drivers . You will find my video on YouTube

In the last 2 editions of Voice Coil magazine they measured the Eminence drivers, the 18" and the 21".

Extremely interesting idea about this amp? Are you limiting it to 110V-16A it will you go to 230 V and even more, like 32 A ?

This is not M-Force , it’s a chinese A&D audio driver. Neo motor and 8” coil. I heard the M-Force more than once and it is absolutely amazing. Unfortunately the users had some unlucky situations with them but they indeed perform extremely well! that Funktion one sub is the loudest sub out there !period ! and it digs deep enough to be extremely impressive. It goes louder under 50 hz than 2 SKhorns XL loaded with Ipal and used with other subs from 60 hz up they will have enough headroom. There are a few companies who have 6 and 8 of them in use constantly with great results.

It is in fact a modified version of 18SW100. Slight difference, mostly in suspension

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

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

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

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

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

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.

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.

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

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.

Caution! "This image contains large amounts of beef!"

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!

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

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.

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 ?