radulescu_paul_mircea

Nice! Different port dimensions too?

The picture is from B&C Facebook page, posted by Bennett, from what he responded in the comments of a closed group. So it's a legit pic. Almost every speaker manufacturer works with non magnetized motors because it's safer, easier to work with , easier to center , cheaper to transport. It seems already attached but I cannot know for sure.

In case you didn't know, in the B&C21Ipal drivers there are 4.1 Kg of neodymium. A huge 6 Inch chunk of magnet, so big, it could be made of ferrite and used as other 18" drivers motors haha.

The basket seems to be like the one from thympany but the diaphragm and motor looks different. https://www.tymphany.com/transducers/sbs-300f38cp01-04/

https://m.facebook.com/story.php?story_fbid=2382026038508193&id=100001024606404

RCF LF21N551 arrived and tested. The driver is extremely well built, it is more powerful and efficient than my 21SW152 and the parameters better matches the SKHORN XL enclosures. The BL is pretty close to the specs, the excursion capability is excellent, with 18 mm gap and 39 mm dual layer inside outside coil, better but noisier cooling strategy. The triple point joint is reinforced with epoxy resin and the leads are glued to the spiders . The mechanical noise doesn't really appear even at 5.5 cm peak to peak excursion in free air but the turbulences are loud. I recommend it in these enclosures with all my heart.

The noise was present right out of the box, at any level in free air. Breaking in didn't help, as a matter of fact it made things worse. Enclosures had nothing to do with this, the other drivers behave excellent in there. The solution was recone , but the delivery terms are way too big for what I can handle. I sent them and they repaired them all, but after a long time...

The company is big, the other drivers work very well and very hard with no problems. Bennett was very helpful with me, but this problem keeps appearing. I reevaluated my settings, the enclosure, measured temperature, working conditions, changed enclosure , all sorts of things. I have 2 working well right now, they have played for over 150 hours at very high levels on all sorts of program, including having ATB and Lost Frequencies playing on them. No issues so far. 2 21ID drivers were used in the other SKhorn XL enclosure with no issues for the same amount of time. Settings and limits were identical (relative to each other's impedance)

@Crashpc thanks for the quick reply. All the drivers were sent back to the factory and repaired under warranty. The problem is they didn't recognize there is a problem with the driver. It happened to me just with the Ipal, none of the others had that problem. The noise is a strong ticking sound coming from the spider suspension and a rumble like that of a diesel engine, in tandem with excursion. It is present no matter what level and it increase directly proportional with it.

I have a question regarding the 21Ipal driver failures. Is there any of you guys having any problems with them? I had some problems with my drivers in the past year. 4 of them had a strong noise in the suspension, 2 had them right from the beginning, 2 developed it after 5-10 minutes of use. 2 others had one of the two layers unglued and unfortunately it was the one underneath so I had to sent them back. Another one had the suspension not glued straight , one could clearly see a 2-3 mm difference on one side . Please tell me about your experiences.

https://m.facebook.com/story.php?story_fbid=2368478136529650&id=100001024606404 They are all getting a place in those SKHorns XL

I might not be the first because after all, it will be at least one month from now until I'll get them.. but when I'll have them, I'll test them in every way I can.

Today was the delivery term, but because of the holidays, it will be a small delay. I'll post some pics and my opinion when I get them.

Going back to my issue with the drivers in electrical series, I can say there is absolutely no difference between them linked like that or parallel. All my tests and measurements showed me nothing changes, a small voltage difference is present, but only 1-2 V at 60 V sines.

A K10 is more powerful and efficient than an FFA10k. On a pair of SKhorns 16A will be enough on the long. But you will see a voltage drop for sure and also you will see lots of amps drawn on the short term. On the K10 and K20 I have I've seen 47 amps at 225 V on display for large peaks. That's on the power supply, not the output stage. There I've seen 100 Amps and 220 V peaks on the K20 meaning 11KVA reactive power.

I would recommend 2 drivers in series with a K20, one sub per channel. Or a SP12000. Or a driver per channel on SP12000 if you want to melt the coil in the first song. It works well with any amp capable of driving 2 ohm subs. The average and minimum load are higher than what one would get if one would use a pair of 4 ohm cabs per channel like a Stasys X, DBH218, F221 etc that would drop lower on minimums.

Why did this disappear?

I just bought a pair of B&C 21SW152-8, a pair of RCF 21N551 and a pair of 18Sound 21NTLW5000-4 and I'll load all of them in my XL version to see how close the sims get to the real deal and why.

Nice!! SW152 is the best choice except IPal. I worked with PD2151 in some different alignments. Huge efficiency, even higher that the IPal drivers. Low MMS and very high BL. They can take a lot of voltage I low order alignments , they are very well suited to 4th order bandpass. They are conservatively rated at 1000 ( in comparison to other well respected brands) but they can really take 400 watts thermal dissipation, but they cannot dissipate that much heat as one IPal driver and the excursion is limited. Very linear, better than most in craftsmanship,

It seems Danley is using electrical series on their TH812 subwoofers

I wanted to post this picture from last night. They are way more powerful under 45 Hz than 6 Electrovoice Xsub. I used them all in a configuration where I had a null in the DJs spot and a good spread across the venue. With any song that had serious content under 45 Hz, if I turned mine off, the 6 dual 18 were at least 10 dB lower than the whole setup. I love their sound !

I don't have 2 ohms 21Ipal drivers. They do not exist for now. The power of the IPal module is exactly what a 21Ipal driver is able to handle in a well ventilated enclosure. I'm not that impressed either. But I don't have access to SpeakerPower amplifiers in Europe, especially with the taxes we have around here . It wouldn't really be a good competition for the price I can get the modules or other amps.

No, they are single voice coil drivers. But there are 2 drivers in the same enclosure. The difference in resistance gives a small variation. That variation will change the electromagnetic parameters a bit. The variance in the magnetic field intensity adds to that. Then the mechanical parameters of the soft parts will change the general impedance curves between different drivers in identical enclosures. If this drivers are linked in series, being reactive loads, they go haywire even with small variations, because they ask for different voltages and amperages but also with different electric phase angles and this way the variance increases. Then at the onset of large nonlinearities in KMS and BL , the difference can increase quite a bit or decrease if you are lucky. But the difference in load is a difference in temperature, a positive feedback occurs in a worst case scenario. I work with my subs in a pro audio environment and they get used to the limits often. I need to get rid of this problem and the only way is by using them in parallel, with one amp per driver. This sub loaded with 2 21Pal presents a 2.25 ohms minimum load, 3.7 average in series so I would need an amp that can be stable at 1.1 ohms minimum at very low frequency and high power, meaning I'm left with 2 IPal modules per unit. From an economic point of view, it is not very good, I would be better with 2 separate single driver enclosures, where I would gain efficiency, output and portability at the same time. But a dual 21 dual IPal module ultrasubwoofer sounds very fun for fixed installations.

Off course I did flip the Voltage meters to take them out of question, I changed the polarity, I changed the frequency, I put them in parallel on the same channel or different channels. The voltage difference exhibits only when linked in series. It is way way worse when they are free air, when they are not loaded by the enclosure like under port tunnig. The excursion difference is pretty obvious when I have the hatches open. I never tested their TS parameters. 2 of the drivers are not with me for now , they went to warranty, one of the remaining will go soon. The same thing happens with the ID drivers, the voltage is extremely different when measured but in this enclosure one driver had 1 hour of break in before loading, the other didn't. After 10 hours of high level music, the difference diminished but it was present still, at about the same level as with the IPal drivers.

I am referring to electrical series not acoustical. I confirmed my theory by Akabak first and then I measured the voltage at the drivers connectors and they differ by up to 6 V when driven with 80 V. So one driver gets 37 V and another 43 V at the same time measured at 38 Hz where driver excursion is maximum. I'm going to test them as you said Sunday. Outdoors with drivers in series and parallel impedance and magnitude.