Ricci

I wanted to see just what these big horn / CD combos are capable of so a bunch of increasingly loud measurements were taken to capture output compression and distortion. I used 512m length sweeps. Even with earplugs and shooting phones this got to be really annoying. I stopped with the JBL's at 16 volts. I quit at 22.5 volts with the AXI2050, before I got to 28.3 volts (100W nominal). They would've survived at 28.3 volts, if the sweep was limited to above 500Hz I'm sure, but 130dB in the 500-2.5kHz region is brutal!  Burst testing to look at dynamic capability, would've gotten really ridiculous. I decided to forego that. 

First up the 2445H on 2360A.

Increasing drive levels. 

2445H on 2360A. The same data as above presented normalized as output compression. Note the expansion near 10 and 12kHz likely due to shifting of resonances. 

JBL 2445H on 2360A. THD from the same measurement set. 

Distortion makeup at 2.83V

Distortion makeup at 15.9 volts.

Horizontal response. 

Vertical Response.

This is all taken in a LARGE warehouse room with a fairly high background noise level and I wasn't super strict about the minimizing mic reflections,  so take that for what it is. The measurements are taken at 1m and gated below 150Hz. Ideally the measurements would be made at a further distance from these huge horns and in an outdoor setting to get into the far field. This is the best space I could get and what I had to work with at the time. I figured I'd note this lest someone thinks this was an outdoor test, or a lab grade endeavor. 

JBL 2445H on 2360A frequency response. Comparison of both drive units. 

AXI2050 on 2360A frequency response. Comparison of both drive units. 

AXI2050 vs 2445H...Both on 2360A Horn

AXI2050 on K402 frequency response. Comparison of both drive units. 

AXI2050 on K402 vs 2360A comparison

Impedance measurements of both JBL 2445H CD's. Overall the matching of the drivers isn't bad considering their age. Unfortunately Mounting the 2445H to the K-402 would've required cutting into the mounting bracket to clear the magnet diameter. I didn't feel like taking that step. 

Impedance of both 2445H CD's loaded on 2360A horns. 

Impedance of one of the 2445H CD's without a lens and loaded to the 2360A.

Impedance comparison of AXI2050's. 

AXI2050 impedance with no lens vs loaded onto 2360A

AXI2050 impedance with no lens vs loaded onto K402

AXI2050 impedance on K402 vs on 2360A

2445H vs AXI2050 raw impedance

2445H vs AXI2050 both loaded onto 2360A horn

As some of you probably know I switched out the top end of my big warehouse system a long time ago. I went from JBL 2445H's on 2360A's to Celestion AXI2050's on Klipsch K-402's. I took a bunch of measurements but never got around to posting any of it. 

I'm not going to devote too much time writing up a big break down of all of this. 

The short version is the K-402 horn is an overall improvement over the old JBL 2360A in most ways. The JBL does offer better loading down to deeper frequencies, but has more acoustic issues overall. Resonances etc...Physically the K-402 is slightly, smaller, lighter and less deep too. 

The old 2445H CD is not a cutting edge design any more but it is surprisingly viable still. 

The AXI2050 is considered cutting edge and it does offer some intriguing benefits, but it isn't all wins against the relatively ancient 2245H (or other more conventional 4" CD's).

My short take on the AXI2050 is this: It offers excellent lower midrange performance with the possibility of really using it XO'd down to 350-400Hz (with less than full out pro use SPL and duration), or 500-600Hz at full on pro / arena use levels and depending on the horn/ waveguide used with it of course. Coupled with large horns such as these, the SPL and distortion results in the lower midrange are impressive. This driver does technically make it up to 20kHz but it requires a really healthy dose of EQ, even more than with most large CD's. The old 2445H kicks the AXI2050's ass in the top octave. The AXI2050 sensitivity and response above 10kHz is serviceable, but not great. Where it shines is in the 400-8kHz bandwidth. It measures well and sounds stellar in this range. Other options cover >10kHz much better with greater sensitivity. Even after EQing the top octave into shape it only sounded adequate. It wasn't bad but it wasn't anything to write home about either. The midrange on the other hand sounded great. Also this is a really robust CD. It will handle border line abuse that I'm not sure some other CD's would. 

In summary. AXI2050 = Killer midrange / so so top octave. I ended up switching to and keeping the AXI2050 because the midrange is way more important to me than top octave treble. 

I was using STEPS at the time and using a really tight frequency interval. I once had an LMS5400 that the motor got so hot you could fry an egg on it afterward. That driver survived probably due to the extra heat sinking of the metallic former and cone, shorting rings etc. Lesser ones did not. 

The rotary has been around a long time. Old news. Some guys have tried to DIY it with varying success. The main reasons it isn't more popular is it's expensive as hell, It requires some sort of isolation because the operation is a little noisy, it requires a large airspace / IB for the back wave and it really only operates well below 30Hz. 

With that said I've heard from industry vets that it sounds amazing when done right. 

Anyway...A little off topic for the Skram thread. Unless you are planning to install 2 to operate under Skram's?

I searched a bit for the notes accompanying note "1" but couldn't find it either. 

Needless to say context matters. The details behind the 1% distortion claim accompanying the 136dB at 20Hz is what really would be of interest. I'm assuming they have active feedback in the subs but even still...Having measured a number of Velodyne, Rhythmik and other subs with feedback, it helps, but it can't clean up things at near maximum output by that much. 

I used to use stepped sine tests for distortion testing of subs. Quickly realized that's a bit too brutal at the maximum drive levels I was using. Cooked a few learning that the hard way. 

What Magico aren't saying is under what conditions that was measured or simulated. I looked but not exhaustively. The sub might do it in a car or a closet. 

4000w = 36dBw 

Average sensitivity of sealed 18's I've measured is about 79-82dB at 20Hz. With 2 drivers in double the airspace it's maybe 85dB tops. It will increase a little with a much larger cabinet, but theirs isn't that large. 

They look to be using Aura based 15's and 18's judging by the pics. They may be modified but those are definitely Aura based drivers at minimum. Decent drivers for sure but no way in hell they maintain 1% distortion with any sort of real excursion being used. Even with active feedback. No way a sealed cab can make loud 20Hz noises without tons of excursion because physics. Unless...they are in a tiny confined space like a closet or measured extremely close to the cone, or both. 

When I measured the Aura 18 it would burst about 107.5dB maxed out at 20Hz with horrendous distortion. This is basically everything it has before something breaks. Add 6dB for a second identical unit on double the power. Call it 114dB rounded up. Subtract a couple dB to clean the output up and pass CEA-2010 thresholds and my estimate for Magico's Q Sub at 20Hz under DB style ground plane testing (2m groundplane, rms) is in the neighborhood of 112dB. Assuming the amp can push it that far. Definitely not with 1% distortion. 

Add 3dB for peak SPL. Add another 6dB for 1 meter results. The remaining 15dB must be from the particulars in the way the sub is measured. 

On 12/4/2021 at 8:21 PM, peniku8 said:

Yea, seeing how the results on the Hypex amp are barely any different at all, I guess we can safely classify and dumb down application types by a single frequency. 60hz for mid-bass, since that's where the kick drum will sit in most non electronic modern music, 10Hz for the HT ULF crowd and 1khz as general full range guideline, but I'm not sure if 16khz is of any value at all. Music is typically mixed to drop off by 3db per octave and then even more when approaching the last octave, so 16khz demands will already be only a fraction of even just 1khz, unless you're talking long-throw line array applications where you need lots of distance loss compensation, in which case you're most likely using specific system amps anyways (or you somehow need maximum power into a super tweeter!??).

You can call the segments 'Full range performance', 'Bass performance' and 'Deep bass performance' I guess.

Sounds like a solid plan to me. K.I.S.S.

On 12/4/2021 at 7:12 PM, m_ms said:

Thanks for this rundown, @Ricci.

 Every indication so far is for the Skram's being "tight, punchy/impactful and very clean sounding" 

(Tidbit) Initially, prior to having my MicroWrecker's built, I actually favored the Othorn's, but the rather expensive 21SW152 was a deal breaker. So far though I've been very happy with the MW's. 

 

I've not actually tested or listened to the Skram yet. I do have a pair of Skhorns which should sound very similar in character. I sold my Othorn's awhile back. I do prefer the Skhorn / Skram sound. To me it is slightly more clean, more flexible, easier to build, smaller and can avoid some of the resonances that show up in TH's. I spent a lot of time trying to clean these up in the Othorn design. TH's can sound very good and the Othorn was the best I've heard or seen measured. 

Every sub I design has priority #1 of low distortion, high headroom, high damping. Those aren't always complimentary goals. They aren't always easy to accomplish with high order designs either. 

As far as drivers go the best ones are expensive. Most of what I design requires them due to the priorities and attributes chosen. Any old driver will make noise in any cab but there's a reason I only recommend ones I'm confident will perform like the sub is intended to. 

Excellent Victor. Welcome to the forums. I look forward to your build. 

How about removing the 15, 30 and 100Hz results. 

Report something like 8Hz ULF, 60Hz Bass, 1kHz Mid?

Maybe 16Khz Treble?

On 11/24/2021 at 1:51 PM, nerdoldnerdith said:

How does the efficiency of the SKRAM compare to the Devastator (25%)? I'm very new to the world of horns, but am looking at them to achieve visceral, impactful bass that I can't get with sealed designs. I think the pant-flapping, chest-destroying insanity I am trying to achieve has something to do with efficiency.

With bass size is king. 

Comparing the Skram or any other cab to another random bass cab is really not that useful...Unless the data is good for both and other factors are taken into consideration. Size, weight, cost, complexity, intended frequency bandwidth, etc...

All I know about the Dev style cabs is that they seem to have been inspired by my designs like the MAUL, Skhorn, etc...That's fine. No big deal. I was in no way the first to do this style of cabinet either. There is plenty of prior art in professional designs for sure. It is really difficult to have a genuinely new development in speakers unless it's in the digital domain. Anyway. They seem to be popular and there's a crap ton of flavors of the same basic thing. Most of them are MUCH bigger than the Skram. I have no idea how refined these are, or which one you are comparing to. Are there good quality GP measurements available? 

PK CX800 is really popular. It's just a vented sub that uses good drivers (18Sound 18NLW9601 units). Nothing ground breaking there, just solid components and design. Regular old vented still ticks a whole lot of boxes when done right. Especially if you start looking at output vs size. Vented will give maximum output at the LF corner in most scenario's, but will give up output in the rest of the frequency bandwidth against other types of designs of the same size. Output vs output I'd hesitate to speculate on too much, but if I had to guess I'd say they will be fairly close. The CX800 might win near the vent tuning depending on the port geometry and the Skram may win in the kick drum region but without measuring both at war volume it's hard to be definitive. CX800 should have more thermal handling just due to 2 drivers vs 1. This cab is bigger, heavier and more expensive than a Skram though. The biggest difference may be in the character of the sound rather than just output. Direct radiating sounds a bit more dirty generally speaking and a lot of people like that. 

People love to bench race subs but there's a whole lot more to it than output on a simulation. Hell this is part of the reason DB exists, was to show just how flawed a lot of these simulations and assumptions were. 

Nice setup Fink! Welcome to the forum. What drivers are you using in the Skrams? 

Also that Linea amp is supposed to be really good and beastly from what I hear. 

On 11/21/2021 at 4:24 AM, chrapladm said:

I was looking at building 2 skrams and 2 submaximus builds. I have a collection of 4 21SW152's and was going to order another pair of 21's depending on what I am lacking. I originally thought four Skrams would be enough for anything but wondered about 5-20hz. Nothing settled yet but my only other option outside of BC 21's are a pair of Harbottle 24's or a bunch of Sundown 18U's.

 

@klipsch Do your pair of Skrams keep up with the sealed 18's?

Well if you use the single vent open mode the tuning is around 15Hz if I recall. With 4 of them in a home with room gain below 30Hz, I'd expect strong output to 12 or 13Hz. You should have firepower to spare to use the lowest tuning. You would never do this in an outdoor PA type setting but in a home I'd likely run with only 1 or 2 vents open myself. As usual experimentation is key. YMMV. 

Chasing much below 15Hz is best handled by sealed/IB/shakers IMHO.

On 11/17/2021 at 1:53 AM, Tahoejmfc said:

 

This is freakin awesome LMAO. I'm jealous of this setup. 

9 hours ago, Rivilee said:

I just finished A/B'ing a Skram with a LaVoce and the Eminence. There is a slight difference in the sound quality to my ears but it could be just as much a placement issue as timbre. I didn't keep track of the cabinet placement when I swapped out drivers. That's how slight the difference is to me. I say go for it with the cheaper drivers.

I also picked up some more plywood from my supplier (Nashville Plywood) yesterday. Supply is back on track and prices are down slightly. They were of the opinion that eventually the price will come down almost to where it was before all the crazy started.

I like your setup. I just finished my version of a 4 12" driver MEH and I find myself just sitting in my shop listening. Going 2 way from the Skram to the MEHs. 

Nice setup. Do you have a link to the MEH build? 

I'm not surprised at the listening impression. The response differences aren't that big and unless pushed to the point that the Lavoce is starting to run out of gas the performance advantages of the Eminence won't come into play. That's going to be quite deep into the volume knob when that would happen. Really only comes into play if you need another clean 3dB out of the cab. 

18 hours ago, m_ms said:

That's exactly what I'm going after. 

I'd be surprised if they wouldn't be able to either, but that's only based on the feedback I've heard from others. Seems I won't be disregarding the 21SW152's after all if were to find them at a fair price!

The only real hold-back right now is the crazy sky rocketing of prices for plywood (I'd have these built in 13-ply Baltic birch, just like my MW's). The prices do appear to have reached their upper limit by now, so we'll see how it develops from here.  

Should work out well then. 

Yes foam is perfectly fine. Cut to shape but oversized and stuff it in there. Yes it will be a tiny bit lossy. It doesn't matter. No need for wood blockers unless the foam makes your OCD trigger.

My top pick for these is still the NSW6021-6 Eminence, but the Lavoce should do fine. The Eminence gives some advantages in response smoothness, ultimate headroom, distortion and compression performance but at increased cost. Unless you run them hard enough to start straining the Lavoce or 21SW152-4 driver most of that will not come into play though. In a home? Not so sure the extra guts are necessary. 

Hahaha. Use the volume control fellas. I say go for it and run 2 in the house. Plug a vent or two for deeper tuning since you will not be using all of the headroom. May as well go for lower extension. I would pick these over the Othorn.

Yes if you let a pair rip in your home it will be a bit much. 

What I often find is this type of sub sounds clean at volumes most others don't, so you end up turning them up higher than usual because it just sounds good/effortless/fun compared to a typical home sub. This gets out of hand quickly in a small enclosed room. 

I tend to like going way overkill and use <50% because it ends up sounding so clean. Plus if I ever want to get stupid it's there on tap. 

Disagree a bit on the 21SW152 or other big pro drivers not being able to do nuance.

Very cool Chris. I hope this event turns out well. 

Too bad I'm a little far from Germany to attend!

An FDM machine with a large enough frame to do a 40x25" horn is going to cost a bit. I guess you could print in multiple pieces and assemble but the discontinuities in the horn will affect the results. 

Sounds like a plan and I agree. Save the time and the wear and tear on all of the above. There simply aren't any common scenarios where the content calls for 100% duty cycle signals for any length of time. Perhaps an SPL competition for a few seconds.

I do not have DXF files developed for this. Your CNC provider would need to roll their own. This is the simplest design though. It shouldn't be very difficult. 

On 10/12/2021 at 12:50 AM, Tahoejmfc said:

Hi Everyone, I am looking into building the EDM version of the design that Powersoft has released for my art car.

Definitely keep us updated on this!