radulescu_paul_mircea

If you look at the measurement I posted since I built these 2, youll see they all are a bit different, especially between 32 and 45 hz. The first ones are with the drivers in parallel, the last ones are with drivers in series. A different Q behavior... Look also at the response of one enclosure vs 2 of them, the ports get better with 2, a higher Q and at least 1 hz lower extension. Off course some of them differ because the space where I measured them is different and no matter what post analisys I use, some reflections will get into the final impulse response, otherwhize I loose resolution and accuracy down low. these differences account for about +- 0.5 to 1 dB sometimes.

I put my camera inside many times. it does appear to have a problem there. Also the behavior is different when drivers are in parallel, the response between 32-39 hz is 1 db higher in sensitivity, but this I still need to verify again. when the hatches are open and i pass a sine wave anywhere under 50 hz, the drivers excursion is visible and the difference can be very big, like double somewhere under Fs. I'll instal the Ipal modules on them loaded with ID and I have decided shorten the ports to go to 32 Hz instead of 28 Hz as it is now. I wanted them to be 30 hz, I thought they ended up at 29 but 28 is definitely too low, especially for the 18Sound ones. I need to cut 16 cm out of them to be able to get close to where I want them to be but I have a vertical brace in my way. from the experience with the BR with RCF and from sims, going to 32 Hz will increase the output by about 3 db under 45 hz, the output at 30 will be the same and under that it doesn't matter anymore, because the place where they will be installed doesn't need anything that low. Again, I'll have to say about the sound of it, it is absolutely fenomental. The impact that 2 of these have is awesome. I'm in the process of designing and building another set of 2 slightly modified but the same dimensions. I can't wait to hear them together. I took a measuerement between front and back. Unknown voltage, 2 subs one on top of the other, equitemporal distance, so the distance are matche in impulse delay, not in ruler. very good directivity!

I did the measurements again to directly compare the 21ID Vs 21IPal Measured at 4 meters, normalised to 2 meters CEA2010 2 m K20 bridge BPH221 ID 4 ohms 20 Hz 104.6 25 Hz 126.2 28 Hz 132.2 30 Hz 133.4 31.5 Hz 133.1 35 Hz 133.1 40 Hz 137.0 50 Hz 141.2 63 Hz 140.1 70 Hz 142.0 80 Hz 143.2 100 Hz 144.5 BPH221 Ipal 2 ohms 2 meters 20 Hz 105.8 25 Hz 126.9 28 Hz 134.5 30 Hz 136.6 31.5 Hz 137 5 35 Hz 135.4 40 Hz 138.6 50 Hz 140.7 63 Hz 142.8 70 Hz 144.0 80 Hz 144.6 100 Hz 145.1 I love these tests. The amp asked for huge amounts of power at 28 Hz where the port is tuned. I've seen 720 V peak to peak and 110 amps on the output with series IPal before the 20A breaker dropped. I can say that the drivers in series are a problem, a big one IMO. Very different excursion at 35 Hz between them, that's why the output is lower there

It was the 451. The suspension is more linear and a bit softer. But the glueing seems way better applied and engineered

All the measurements were made outdoor ground plane. One space where I measured the TH and F121 , a wall of the building was 14 meters away but the rest of the space is a lake and a field. I truncated the impulse response to eliminate as much of the load as possible. 17 meters the reflection came 100 ms after so I had very good resolution and clean response down to 10 Hz. The space where I measured Stasys XV2 that I will not publish, the BR with RCF , the SKhorn XL and others is a very large space where the building behind and on one side was at 25 meters and the other 2 sides were empty for more than 100 meters. I switched from MC2 to clone and X4 because I own a clone, a K20 and I have 2 X4 for an install that I could use but the MC2 was installed in a fixed place where Funktion and TH are installed. I am using REW for generating and measuring the output, Focusrite soundcard, earthworks M30 calibrated mic , a class 1spl calibrator , a Behringer calibrated mic for comparison purposes. Unfortunately one of the RCF drivers kicked the backplate with the coil former and it isn't in the perfect shape right now. I will soon test the SKhorn XL with 21ID , each driver on a K20 channel to see the numbers. Probably next week.

Br221RCF 33hz bridge FP14000 clone 2 meters CEA2010 20 Hz 106 25 Hz 121.3 30 Hz 131.9 31.5 Hz 134.7 33 Hz 136.9 35 Hz 139 40 Hz 141 50 Hz 142.4 63 Hz 140.6 80 Hz 140.8 100 Hz 141.5

CEA 2010 measured at 2 meters F121 MC2 E45 bridge normalised to 2 meters 25 Hz 108 30 Hz 115 31.5 Hz 117.1 35 hz 120.8 40 Hz 127.1 50 Hz 132.3 63 Hz 134.5 80 Hz 136.2 F221 measured at E45 BRIDGE normalised to 2 meters 25 HZ 114.7 dB 30 HZ 121.4 31.5 HZ 123.5 35 HZ 128.9 40 HZ 135.2 50 HZ 139.4 63 HZ 141.5 80 HZ 141.8 100 HZ 142.9 1*TH18 xoc1 measured at 4 METERS MC2 E45 BRIDGE normalised to 2 meters 25 HZ 110.4 30 HZ 123.3 31.5 HZ 125.1 35 HZ 128.2 40 HZ 129.3 50 HZ 133 63 HZ 134.3 80 HZ 134.8 100 HZ 136.6 2*TH18 xoc1 measured at 4 METERS MC2 E45 BRIDGE normalised to 2 meters 25 HZ 116.8 30 HZ 130.3 31.5 HZ 131.9 35 HZ 135 AMP LIM 40 HZ 136.3 clip 50 HZ 139.2 63 HZ 140.2 80 HZ 140.4 100 HZ 142.7

2* TH18 xoc1 8 ohms driver at 28.3 V@4 meters Vs 1 SKHorn XL 14.1 V 4 m. And compared to F221

Another important fact are the distortions. For the same input voltage, 28.3V , between all 5 designs, 2*TH, 1*F221, 2*BR29hz RCF, 2* BR29Hz Ipal, 2*BR33Hz RCF and 2* SKHorn XL, the last one is the best one, with under 2.5 % distortion from 31-110 Hz. Compared to F221 that has up to 7%, or BR33hz RCF that goes to 5.8% at 40 Hz.. the proportion of the orders of harmonics are also very different and the ones with the drivers close to the surface have their own sound signature. I believe what I can hear is probably some very small air turbulences across the drivers diaphragms and suspensions and other things because of the fact that the acoustic impedance mismatch will always have a part of the air molecules wiggling over the surface, slipping away to the edges. Also any noise from the driver itself is not masked, but that is just it.

@Ricci I messed up the phrasing on that. I meant that the RCF loaded enclosure with 29 hz tuning lacked punch and depth. The enclosures with RCF and 21Ipal are the same. After I changed it to 33 Hz, increasing the surface with 30% and decreasing the length with the same percentage, it improved quite a bit, but still no comparison to SKHorn XL, which indeed is absolutely devastating in that category! New tuning in green. It makes sense what you said about loading. TBH I don't think the main problem lies with the port losses, but with the magnetic strength and damping. Off course, the performances of a reflex enclosure is in fact simple to deduce from measurements and Sims and also is pretty simple to design properly. How it will sound though based on that,you could never really know until.you build it. I found something interesting regarding group delay and linearity. If it is my feeling that a lower group delay is good, but it makes things sound thin. A higher and more even group delay will exacerbate the lower frequencies and it will make them jump into attention.

Add 6 dB for 2 meter results. CEA 2010 4 meters 1*F1218 ohms MC2 E45 bridge 25 Hz 102 30 Hz 109 31.5 Hz 111.1 35 hz 114.8 40 Hz 121.1 50 Hz 126.3 63 Hz 128.5 80 Hz 130.2 1*F221 4 ohms E45 BRIDGE 25 HZ 108.7 dB 30 HZ 115.4 31.5 HZ 117.5 35 HZ 122.9 40 HZ 129.2 50 HZ 133.4 63 HZ 135.5 80 HZ 135.8 100 HZ 136.9 1*TH18 8 ohms 4 METERS MC2 E45 BRIDGE 25 HZ 104.4 30 HZ 117.3 31.5 HZ 119.1 35 HZ 122.2 40 HZ 123.3 50 HZ 127 63 HZ 128.3 80 HZ 128.8 100 HZ 130.6 2*TH118 8 ohms 4 METERS MC2 E45 BRIDGE 25 HZ 110.8 30 HZ 124.3 31.5 HZ 125.9 35 HZ 129 AMP LIM 40 HZ 130.3 clip 50 HZ 133.2 63 HZ 134.2 80 HZ 134.4 100 HZ 136.7 The results I got with one and 2 F221 this summer were not ok, something was absorbing a lot of power under 60 Hz. I got +6 dB now from them today in comparison at 25 and 30 Hz. But still no match for a single SKHorn XL. It seems that it is very close to 4 TH18 at 30 Hz and 3 of them under 100 Hz.

635 Liters net reflex enclosure, 1680 sq cm port, 40 cm length measured in the same place, same mic, same calibration, same windowing. I am very surprised that the Bandpass SKHorn XL loads the driver that low. The enclosure is very big and I don't like how it sounds on music, it lacks the real kick. But the deep end is very powerful and clean.

The new sub design in grey vs this one including some power compression effects added as eq , 140*140*70 cm so 40% larger. I put 2 vs 2 because from my experiments with subs the response doesn't go lower when multiples are used but they can take more power with less excursion and distortions, so it is a bit closer to real world results. I'll use 7075 alluminum braces to save volume, add stiffness and decrease weight. The drivers will have 2 additional ways of cooling so in normal full power usage, it will closer to 2 SKH larger, but the same number of drivers and amp channels as one.

The idea behind this build is to learn. I started my company to sell subs, because here in this part of Europe, there is a very deep lack of powerful high quality bass Mostly I wanted to see people's reactions, the power density, the extension, to see if the weight and dimensions are a big problem. They are now installed in a basement where we got them by hand. I wanted to see about the power compression, port noises, chuffing, I have learned how and why to install protection grilles, handles, wheels, I wanted to see if I can improve their performance in any way without any other compromise except cost and complexity. I wanted to learn about braces, hatches, accessibility. These gave me a good insight on all of these These subs will be loaded with 21ID and Ipal modules and will permanently stay in rent in a small club where people love good sound. Based on what I learned, I'll continue my other designs and after all 4 designs will be ready and I'll have a stock of 4 of each, I'll publish the specs, measurements, graphs , technical details , pictures and videos and I'll start selling those.

From what I can figure out from the output prediction on Direct from Danley, this sub is on par with TH812, including efficiency, impedance graphs, response and SPL

The sound is the best I have ever heard, including F132+F221 combination. It lacks the 40 Hz punch a bit, there is a slight issue with that area when the drivers are in series. I need to take them out again and get some impedance measurements series and parallel to see if there is any difference at very small signals. I felt that 4 TH18 would match the output of two of these between 37-47 Hz. But yes, absolutely no match at 30 Hz. I get about 4.5 dB of compression on very long sines , 0.3-0.6 sec but no noises and the chuffing is pretty much absent. I would love to compare them to a set of KS28 from L-acoustics, Gravity 218 and 30 from PK sound and other subs that say they go down to 30 Hz. I don't like that the hatches are not as solid as I would like and the bracings inside are very ineffective, I need to rethink them altogether. I'll probably change the whole thing to see what improvement I can make disregarding cost. Some aluminium braces, some very well rounded port ends, playing with driver position, some different new ways of cooling the driver even at excursion minimums to increase the life expectancy of the coils , thinking of some kind of net for safety on ports because now someone could throw a bottle inside an that would not be very helpful. I am now very much interested in a larger version with the horn loading the driver lower and better . But the weight is already high, 165 kg , so we'll see.

I got myself a Powersoft K20 for these and tested them at full power for 20 hours,the amount of power and the stability that amp has is way way higher than what the clone or the Crown could ever dream off. I set the limiters and processing and I installed them in a small club for further long term tests. The deep end is imense. I have a pair of xoc1 TH18, we got 2 Vs 2 with their own processing and limiters on a K10 and the 2 large SKHorn got +10 dB on a 2 minutes average pink noise dBz and +18 dB at 30 Hz .

The drivers used are 21Ipal , yes . The drivers in F221 are an OEM combination from Fane with Precision Devices, neo driver. The subs are extremely loud , but not on their own . I did some tests regarding the frequency response of a single vs double F221. The tests have revealed me something really cool. The magnitude response stays the same, it just goes up with 6 dB ,double the sound pressure, but the maximum clean output CEA bursts results go higher. Practically a better acoutic impedance will give better load and lower excursion. Plus, the electrical impedance goes a bit higher on average so the real sensitivity for 1 W is increasing CEA-2010 max burst, 2 m ground plane , measured at 4 and 8 meters to avoid mic clipping 1*F221 1 channel of ffa10000 25- 107.9 30-116.1 31.5- 118 40-133.1 50-135.7 60-137.1 80-143.2 100-142.6 2*F221, 2 channels of FFA10000 25- 116.8 30-125.5 31.5-128.5 40-141.5 50-143.6 60-144.7 80-147.9 100-148.1

Sensitivity referenced at 1W/1 m measured at 4 meters, 2.83 V in 0.5 ohms on BPH221 vs 28.3 V in two 8 Ohm F121subs

This is the excursion of two 21Ipal in series in the same enclosure, with the CMS having a difference of only 10% between them. The place where I did these tests is a parking lot from an old factory where we have the workshop. It is surrounded only by other workshops and some offices that were closed at that moment. The parking lot is big, around 50 by 60 meters and if I go as close to the middle as I can, the frequency resolution is very good and I can get good accuracy down to 20 Hz.

@Ricci Thank you for the reply. I am a bit concerned about that behavior, it is not related to the loading in the horn,but the behavior of two reactive loads linked in series, that see different voltages based on the difference in impedance and electrical phase. Anyway, the subs are extremely potent, the content below 40 is so present and clean! I wouldn't be afraid to put them next to Funktion One F132. Unfortunately the clone power supply was not up for the task and after less than an hour with a sub on each channel, it died. Then I tested them with 2 Crown 5002VZ in parallel mode, each sub on a channel and the deepest bass was achieved , it could sustain 85 volts in impedance minimums without any sign of backing up, but the punch and headroom was smaller than with the clone. The next step is to completely change the bracings, build another pair, load them up with 21ID and IPal modules, buy a K20 and then compare them 2 vs 2 and see what happens, whichever is best. I bet on the K20+ 21Ipal combination but one could never be sure until I get the tests results. I would love to use these with SpeakerPower modules, each driver on its own amp, with 4-6 kw, because IMO , that's when the party is really starting. Unfortunately it's hard to buy them from the states.

@Ricci Did you have any problems linking the drivers in series on a single amp? From what I get in sims and in free air tests, the excursion goes mad if the parameters are just a bit different on the 2 drivers. Also the loading can change the behavior

So after all, the CEA-2010 from REW is showing the peak pressure level of the frequency tested, not a mean, so one one shouldn't add another 3 dB to get a peak.

This is the final measurement before painting and adding some damping materials