Murmel

On 9/29/2021 at 6:47 PM, Ricci said:

The Eminence NSW and the Beyma drivers are a little better match for the SKRAM cab due to the extra air volume behind the driver. 

Impedance for the SKHORN with dual Ipal's is available in the measurements section for it. 

I do not have experience with the clone amps but I do not think it would like dual Ipal's in series on sustained bass notes near tuning. It's a 2ohm load with those drivers. That's why I use the SP6000

I can find a ferrite (21QLEX1600FE) and neo (21LEX1600ND) 21" in beyma site, are both suitable or one better than the other? The ferrite seem to like a little bigger enclosures and a few other parameters are a little different. Do you mean they (or one of them?) are a better match than lavoce & B&c aswell? Also for ckram and Skram if so? I've not seen them recommended here before, interesting. The ferrite version is attractively priced in Europe.

31 minutes ago, LSC said:

I'm not sure if I don't understand but the figures you calculated are way higher (not lower) than 700w?

Am I missing something? Are we talking about sines coming from the amp?

Sry for being confused and thanks for caring and elaborating! 

I'm not overly confident in explaining the differences but my guess is has to do with duty cycle and crest factor. When testing amps and voicecoils many use a test signal that somewhat reassemble music which is 33% duty cycle, where 100% duty cycle has much more power density hence the long term tolerable VC wattage is much lower. If you use VERY conservative calculations you use a very high duty cycle signal to measure tolerable long term limiting but the output will suffer and subs not reach their max potential is my take on it.

I'm not sure under what conditions b&c came up with the 400w figure for the ipal, what I do know is that by simply measuring the output voltage of the amp with a sinewave and dial the limiter accordingly I use four times the wattage probably due to much lower duty cycle signals.

Let's assume for a second that the 21ipal is as robust of a driver as the 18sw115 within it's given specifications (I'm not sure whether it is or not, it's an older design).

I'm considering limiting the 18sw115 to 67% of the nominal powerhandling to be safe for very heavy techno, as I've been running them with these settings for many hundreds of hours. I've even limited them to 81% of the nominal powerhandling for two hours and they did not sound strained during peak hour, would it survive that for more extended periods of use? I don't know. One of the reasons I'm not very keen on trying is that some aspects of the cabs are not very good built by me and they already dance around abit on the floor already at the 67% setting. 67% of 21ipal nominal handling is 1675w, or about 43 volts into it's 1.1 ohm minimum impedance. This it should be able to handle like a stroll in the park if it's as robust as 18sw115.

My guess is that this is a bit lower than the 700w rating Josh is talking about above, what the amp is permitted to give the driver and how much juice the amp draw from the outlet are two very different things

I've got a pair of keystrones with 18sw115-8 drivers, I'm generally running them with a driverack pa+ for filters/limiting and a sae pxm 1450 amp which, when paired with a robust power source, is quite a performer. I've been running very demanding techno music (Enrico Sangiuliano, Joseph Capriati and the likes, low crestfactor and continuous basslines) for hours to an end with appropriate filters, 30-100hz for that box, and a limited setting to 87 volts. I've even run them at about 95 volts long term limit for two hours during peak hour at full throttle. That would be equivalent of about 1150 respectively 1388 watts into that driver(when using the Volt x Volt / impedance minima formula) if I understand it correctly the 700w for the ipal21 Josh mentioned above are based on a much more conservative calculation method so these figures won't necessarily clash, there are many ways to calculate powerhandling, and they never complained or sounded bad, quite the opposite actually, and LOUD. I've run bfm t30 cabs very hard but within recommended limits for a few thousand hours aswell never blown a vc in them either..

The 21ds115-4 or 21ds115-8?

They have the same vc diameter as mine, and powerhandling on paper. The 8 ohm has the same impedance minima as my drivers(6.5 ohm) so I would use these long term voltage limiter settings with them that I use, but I've not been confident running them at 95 volts 99% of the time I set them to 87. The limiter resolution of my drpa with that amp is in 8 volts steps if I recall correctly.

That would be equivalent of approx 60 respectively 65 volts for the same power applied to the 3.1 ohm impedance minima of the 21ds115-4. Take it for what it's worth, I've always had the intention of extracting every bit of performance from my drivers and they never failed me:) but actually I'm a bit surprised I've never blown anything.

Not to say these settings will work for you, I guess limiters can work differently in different LMS for example, just giving my perspective of things.

How big is the risk of skram dancing around in a high powered club situation? They have bigger piston area/sqft of cab volume compared to my keystrones, which move around on all floors I've tried them on if nothing significantly weighty is strapped onto them.

Dual loaded or two single loaded? Ricci is in the design process of a single driver version of the Skhorn, don't know when it's gonna be(or if, but probably from the very generous person he is) it's gonna be available, last time I read something about it it was rather close to being finished tho.

Skhorn with one or two ports blocked. Do you have an amp already?

12 hours ago, radulescu_paul_mircea said:

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.

Thanks a lot for that detailed answer!

One thing I have in concern, a lot of the venues we tend to work in rarely provide stable 32A feeds, which possibly could favour the ffa10k (seem to be compared to somewhere between a k8/k10 in power) in that regard, if you have good 32A feed I presume k20 is very hard to beat.

Hi Josh & All. I wonder what would be appropriate amp power to justify using most of the potential of 21ipal in this cab, for example if the k20/ffa10k could drive two 1 ohm models wired in series on each side of the amp good enough for it to be worth considering 21ipal, or if it would be considerably better to try and find 2 ohm models(maybe complicated) wired in series and a bridged k20 per cab.

I read the cab makes quite a bit of noise with only about 500w of power each driver so I figure it could work rather fine?

Thanks!

Possibly. I'd expect 2 Othorns with Ipals to have a slight advantage right near 25 to 35 but that's about it. Of course two Othorns is 50% bigger than one of these cabs too.

 

The 21ds115s should be more of a straight up comparison to the 21sw152 loaded Othorns so we will see. I did run some music through it with the SP amp last night in the warehouse space and the amount of headroom and slam is unreal.

IPAL loaded that is I presume? Does it dance around in it's own footprint or do the dual-driver-config cancel the forces out?

Hi Josh! Very interesting design thread to follow. Thank you for that

With drivers more similarly priced to the 21sw152(21ds115, 18xl1800?) Would there be any benefit using skhorn rather than othorn?

Will be interesting to read your notes!