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Ricci's Skhorn Subwoofer & Files

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2 hours ago, Ricci said:

Ok.

What were the driver specs used? Different for each driver I assume? That is a large difference in voltage. This would likely be caused by differences in the drivers performance rather than the wiring type unless there is a big difference in the amount or type of wire used between each driver. It makes me wonder how well matched the drivers are. If it isn't too much trouble flip the polarity or wiring on the drivers when you do this and see if it stays with a driver.

Perhaps I'll investigate on mine next time I have a chance.

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.

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Are these DVC drivers?  I believe manufacturing variance, possibly amplified by the loading of the cabinets, could play a role in unexpected differences in series vs. parallel performance.  I don't believe such difference will only one voice coil.  It is when there are multiples that you get a series connection between two VCs instead of between a VC and the amp, and that is where I can imagine some unusual electromechanical behavior to arise if manufacturing variances are significant.

Just an idea.

Edited by SME

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5 minutes ago, SME said:

Are these DVC drivers?  I believe manufacturing variance, possibly amplified by the loading of the cabinets, could play a role in unexpected differences in series vs. parallel performance.  I don't believe such difference will only one voice coil.  It is when there are multiples that you get a series connection between two VCs instead of between a VC and the amp, and that is where I can imagine some unusual electromechanical behavior to arise if manufacturing variances are significant.

Just an idea.

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.

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Do you have any real world examples of this kind of positive feedback loop occurring, causing unexpected bottoming or failure due to uneven power dissipation?  Or maybe just really bad sound?

I'm skeptical, but I'm also paranoid.  I'm also a bit paranoid about having multiple drivers share the same air space.  I opted for a solid barrier between air spaces within my dual-opposed sealed subs.  You might want to consider that too if these kinds of interactions between drivers are really a problem for you.

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This is why I am also skeptical that this is an issue worth worrying about. Its not like running drivers in series in a cabinet is new. This is very common practice going way back. Any drivers and cabs will exhibit differences and drivers never behave exactly the same in any scenario. That is known.

What is interesting here is whether series wiring amplifies the differences vs parallel wiring. It really shouldn't.

Paul B&C does have a 2ohm variant of the 21ipal. It has less motor force but would be easier to run 2 off 1 amplifier.

I'm not really that impressed with the power of the Ipal module. Have you thought about the Speakerpower 6000? 

 

 

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6 hours ago, Ricci said:

Paul B&C does have a 2ohm variant of the 21ipal. It has less motor force but would be easier to run 2 off 1 amplifier.

I'm not really that impressed with the power of the Ipal module. Have you thought about the Speakerpower 6000? 

 

 

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.

 

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18 hours ago, Ricci said:

What is interesting here is whether series wiring amplifies the differences vs parallel wiring. It really shouldn't.

While within their limits, amps are essentially voltage control devices, so the loads in parallel won't interact via an electrical path.  There may still be mechanical interactions from shared air space or external proximity/boundary/acoustic loading effects but from an electrical standpoint, the two drivers don't "see" each other.

In a series  configuration however, it is possible for power to be transferred between the drivers unless they're exactly the same.  Any electrical or mechanical differences between the two drivers may cause energy to flow between the two, which can complicate their behavior compared to systems with all drivers in parallel.  It's also possible that this interaction could couple with another interaction (say acoustic or mechanical interaction due to proximity or shared air space) in a way that leads to a feedback loop that causes unstable behavior.

In reality, the differences involved are probably too small for this to be a problem most of the time.  However, I believe there are always opportunities for exceptions.  Some manufacturers may be more consistent than others with regard to parameters that matter.  Loading drivers into a tuned enclosure (especially one with higher pressures like a horn) could amplify certain problems.  Running the drivers harder where non-linearity becomes a big factor is probably likely to accentuate such problems too.

But this is all really just theoretical speculation.  I have no idea if any of these effects are really strong enough to cause serious problems.

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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 !

IMG-20181111-WA0002.jpg

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On 11/10/2018 at 5:08 PM, radulescu_paul_mircea said:

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.

 

Hey Paul I understand sourcing the SP amps would be expensive but more so than the IPAL mods? Those are very expensive here. More than double the price without a heatsink or the dsp interface. 

There is a 2 ohm 21ipal. Its not on their website. Bennett has told me they will sell it if someone asks at least here in the states. I have the pdf. I only mention it because it would be easier on the amps than the 1ohm. I don't know of an amp that will be happy with the 1ohm drivers in parallel. I don't like running half bridge amps for bass either. 2 modules per cab seems very $$$$!!!

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I have ordered 4 drivers 21SW152 8ohm to have a go at these , reasons it’s easier to run 8ohm drivers , and if I don’t like them easier resale, on the second hand market, Any disadvantages with using them drivers , same drivers we wil use for our Othorn , just added a setup we did last weekend with 8 of my ported BR boxes

link to Sp https://forum.speakerplans.com/pd2150-2151-in-br-bins_topic97769.html

25415D19-4B58-43FA-82F8-AC9E35A51983.jpeg

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7 hours ago, Father Francis said:

I have ordered 4 drivers 21SW152 8ohm to have a go at these , reasons it’s easier to run 8ohm drivers , and if I don’t like them easier resale, on the second hand market, Any disadvantages with using them drivers , same drivers we wil use for our Othorn , just added a setup we did last weekend with 8 of my ported BR boxes

link to Sp https://forum.speakerplans.com/pd2150-2151-in-br-bins_topic97769.html

 

The 21SW152's should be good. There's at least one guy already using those.

How do you like the PD drivers? Those are rare over here in the states.

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I love the Pd drivers, I use 1550 in our kick bins and 2151 in the subs  ,they can really take lots of power, we running 8* 2151 of one K20 , mostly important to have nuff power 

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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, 

 

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It looks alright, maybe there's something I'm not seeing

Not sure, why it did not make it to the recommended driver list

Just curious what it is...

 

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The 21SW115-8 might be ok...It doesn't look so good once the generic LE is added to the sim. The response gets a bit "humpy". 40Hz and 110Hz with a dip in between. I don't have the complex LE components measured for that driver so it is hard to say how it would turn out exactly. It's an approximation otherwise. This is why I hesitated to recommend it. I just don't know for sure. 

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I have only one of each drivers

21SW115-4
18SW115-8
18NW100-8

I'd like to build another SKHorn
Just wondering which I should go with and buy another of these 3 drivers.

Would you say the 18SW115-8 is my best bet?
 

 

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Only a question not asked is stupid. But this could still be a stupid question ☺️

While waiting for the other driver. What happens if I run both 18SW115-8 &
18NW100-8 in the same Skhorn cab?

Is there a risk of damaging the drivers?

It sims pretty close from what I see.

This will only be for home use. So I won't be maxing it out or hitting 125 dB with it.

 

 

 

 

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Jesal,

I do not know what would happen running the 2 different drivers. I expect that there would be some degradation of the response shape and perhaps a lessening of the output capabilities. Even though the 2 drivers model very similarly this will be a much greater difference than production tolerances or series wiring of 2 of the "same" driver. It would probably "work" at moderate or lower volume levels. If you wanted to get deep into the rabbit hole with it this could be simulated in Akabak. If you have the drivers and measurement capability it would probably be quicker to try it carefully. Long term I definitely wouldn't recommend it.

I would go with another 21SW115-4 out of those 3 options. Displacement is ultimately king.

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17 hours ago, radulescu_paul_mircea said:

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. 

You are the 1st person that I know of who has the 21NTLW5000's. They haven't shown up in the states yet. This is one driver I've been keeping my eye on. The back story on them and other potential drivers in development using what is essentially DD topology is interesting and may be getting more interesting in the future. At least that's what I've heard...

I'll be looking forward to your impressions of the 551 vs the 451 also. I don't know of anyone with the 551's either.

Next year I'll finally test the 21DS115's in the Skhorn and that will be followed by the 21NLW9601 and the 21ID's. I'll probably have a look at the Lavoce 21 too. Sadly all my audio related time lately is porting data over to the new DB site. Haven't had time for any new designs or investigations. :unsure:

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15 minutes ago, Ricci said:

I would go with another 21SW115-4 out of those 3 options. Displacement is ultimately king.

Perfect! Thanks a lot Josh, will get another 21SW115-4 and go ahead with the SKHorn build.

Go for that second SKHorn = Full Alumni Status ;)

The 18's will probably go in your Othorns.

Not sure yet how difficult a build Othorn is. 

I just found the SKHorn a pretty easy build. 

 

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