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I modeled a CNCable version of the SKRAM fit exactly to the detailed plans provided by Ricci in post #1. Feel free to use them as a base. These are meant to be used with Adam Hall 3402 and Neutrik NL4MPRXX, so you might want to adjust the respective pockets and cutouts. I did not yet include pockets/holes for wheels. SKRAM 3D.step Assembled enclosure SKRAM PARALEL CAM.f3d - Fusion 360 File including programmed toolpaths. 12mm Sheet 1.step 12mm Bracings as optimized flatpack 18mm Sheet 1.step18mm Sheet 2.step18mm Sheet 3.step 18mm Parts as optimized flatpacks. SKRAM Individual Parts.zipIndividual Parts

Hey all, long time lurker, been using the Skram for about 2 years now and decided it's finally time to post some proper calibrated measurements. I’m an acoustical engineer at QSC, and run my own custom rig as a side hobby. I've only been in acoustics for 2 years, before that I was an amplifier engineer so I'm still learning some of this stuff. Been meaning to get this info for a while and finally had some outdoor measurements to make for work, so while I had things set up, I thought I would go ahead and get some comprehensive measurements for this build. I’m currently running them with the 21SW152-8, but we’ll be getting our hands on the new cost-effective Celestion TSQ2145 for evaluation soon, at which point I’ll get another indoor groundplane & impedance measurement. I haven’t added fiber fill/acoustic foam to mine yet, so that could be another interesting data point. Indoor ground plane measurements are done with our 1/4th space calibrated, scaled, & windowed measurement sequence that we use for all product qualification. Also got some measurements of THD and harmonics at 10v. The one downside is that the signal path has >100ms latency for phase response and there are minor reflections even with the windowing of the impulse response. Unfortunately I can’t post pictures of this setup due to product confidentiality. 1w1m looks to be about 94dB SPL. I am a bit surprised how different the "knee" at 30 hz looks compared to previous measurements in this thread, I'm not sure where that difference is coming from... Earthworks M30 measurement microphone used for all data. ARTA outdoor setup, 22C, 30%humidity: RME Fireface UCX QSC PL-380 Q-SYS Core250i Outline ET series turntable Indoor measurement data: Audio Precision AP2700 for impedance response Lynx Aurora(n) audio interface Grace m801mk2 mic preamp Measured with SoundCheck 15 Outdoor setup has hard walls ~16 meters on either side, so spatial IR responses are windowed to 90mS (2x 16m). Turntable setup to rotate about the physical center of enclosure. Outdoor SPL scaled to match calibrated indoor measurement. I took 2 polar data sets, one with the enclosure vertical, with ports at the bottom, and one on its side, and you can see the slightly asymmetric polar response. I’ve attached a .vacs file with all of the measurements, and I can provide all of the outdoor .pir files if someone was interested. This is an amazing subwoofer, many thanks to @Ricci for his work. Hopefully this information will be useful to you, let me know if there’s anything else you would like to see, or clarification, and I’ll do my best to provide. Skram Data.vacs

Sorry this took so long folks. I had to upgrade mongodb driver from v2 to v6. And nodejs needed to be bumped too. I think I'll move the code to github and make it opensource so more than 1 person can make pull requests Note: There are still some broken elements but thats all on the admin side.

I'm still around.

Heya, I wanted to update this thread with my recent findings comparing straight ports with shaped ones from two 21" subs. I build two cabs of identical size and tuning loaded with 21DS115-8 drivers, where one cab has a straight port and the other one has a port with continuously changing area. The shaped port has a moderate ratio of 2.5 (largest to smallest area). I put both cabs up for compression sweeps at 2m half space and the results are quite interesting. Port compression is visible at around 20V for both cabs, but I don't care much for fractions of a dB of compression. It starts getting interesting at 64V, where the shaped port went 0.5dB into compression and the straight port was at 1.5. The difference remains 1dB at 90V, but now we see power compression starting to kick in as well, centered at around 75Hz. Here are both cabs at 128Vrms input: The difference is still around 1dB at tuning, but now we see a stark difference of around 2dB near 70Hz. The cab with the shaped port behaves much better overall producing a smooth curve, which would still sound excellent at those levels, while the straight ported one starts being kinda all over the place. The difference at tuning is easily explained: the aerodynamic port reduces 'air resistance' so the cab is more efficient there. The expansion at 45Hz I can explain too, or at least speculate: This is where impedance and particle velocity is high, which means no power compresison in this region and vortices forming along the surface, reducing friction with the cabinet walls. The dramatic difference at 70Hz I have no clue. The port does nothing at that frequency... Interestingly, the sweeps at 181V look similar, because both drivers are heavily into power compression at that point, but the shaped port wins out by 1dB on average. Distortion looks pretty similar across all levels, except for the 128V sweep, where the cab with less compression also has quite a bit less distortion (around that 70Hz). So, conculusions.. It looks like overall a shaped port can extract 1-2dB more out of a subwoofer of a given volume, depending on which frequencies you need for your application. The cab with the straight port performed almost identically from 40-60Hz, but for other frequencies, it might be the difference of bringing 6 to bringing 8 cabs to a show. On another note: hornresp predicted this subwoofer's max output at 44Hz to be 124dB (1m full space), limited by Xmax. But I measured 129dB (2m half space) with just 7% THD... 5dB is a pretty big difference, especially since hornresp doesn't factor in any sort of compression...

vent tuning lids added to the skrams. dsp settings are LR 24dB at 10Hz. bass is more exciting even at listening levels. fun times.

If you have an air compressor, buying a brad-nail gun is a better investment than buying clamps imo and it makes building the cab way easier. If your cuts are clean and you don't have to use construction glue, that is the best solution. Danley does it like that. If I didn't buy a large press to put the whole speakers into, I'd do the same. If you really want to use clamps, I can recommend to buy extruded aluminium to spread the clamping force over the length of the edges like I did in my Bordeaux build:

This is the long delayed single driver sub similar in design to the Skhorn. Overall the performance goals and criteria were quite similar. Big surprise there! The Skhorn works so well at what it does that I didn't feel the need to reinvent the sub for this one. This is primarily designed as a professional sound reinforcement or live sound style subwoofer. Big output and clean sound in very big spaces, while covering the typical bass heavy range of music, has always been the primary mission for this sub. Same as it was with the Othorn and Skhorn. It can and I'm sure WILL be employed for other types of situations, but it's a festival or club sub that just happens to be flexible and neutral enough to work in a variety of scenarios. The main differences between the Skram and the Skhorn are as follows. Optimize it more for the cost effective 21's like the 21DS115 and Lavoce SAN214.50 rather than the Ipal drivers like the Skhorn. The Ipal's still work of course, but I relaxed things a bit for the drivers that are a little easier to afford and power. Increased size: Originally I wanted to basically saw the Skhorn in half and slap a top panel on there with modded bracing. It would be a very compact 21" sub, which is great, but the driver would fire directly into an outer panel and even with bracing this is a lot of energy being beamed on axis into a large outside panel. I've never been a fan of high pressure loadings with big drivers that do this. I always want the direct on axis energy from the cone to act on internal panels that are going to keep this energy inside of the cabinet better. This required a rearrangement of the internals. I also added a bit of size while I was at it. I decided to stop at a size that was significantly smaller than the full Skhorn, but not as small as a true half. If this cab is too big or heavy you could always build the true half Skhorn, which would be 24x32x27.71. Increased vent area and slightly increased vented chamber volume. This should help the noise, compression and output near the vent tuning. Increased vent area and length means that the vent pipe resonance is lower in frequency than the Skhorn. I'm, expecting that the response will be less smooth above 150Hz, but that's the tradeoff made for bigger vents. The Skram has 4 vents instead of 3 like on the Skhorn. I decided to add one more for even more tuning options. Tuning with all vents open is basically the same. Being a single driver design, the Skram does not have the dual opposed drivers for mass induced vibration control like in the Skhorn. Other than these changes I would expect that this design behaves and sounds very similar to the Skhorn. I'd expect that the two could be used together without issue. They are more alike than dissimilar. Skram Dimensions: 24"x32"x36" (609.6mm x 812.8mm x 914.4mm) Weight: Cab=115lbs or 52kg projected (Driver will add another 25 to 55lbs (11 to 25kg) depending on the driver. Vent Tuning: All vents open = 29.5Hz / 3 vents open = 25.5Hz / 2 vents open = 20.5Hz / 1 vent open = 14.5Hz Each vent is greater in area than a 6" pipe. All vents open is equivalent in area to 4x 6" ports. All of the usual pro 21's should be a good match. 18Sound 21ID, 21NLW9601 B&C 21DS115, 21SW152, 21Ipal RCF LF21N551 looks decent Lavoce SAN214.50 Eminence NSW6021-6. NOTE about the prints! These are extremely detailed due to being designed in Solidworks and the plans from which my personal cabs would be built. The simplified layout drawing is really all that should be adhered to to build this sub. The bracing and hatch can be simplified to suite your own ideas or the tools available to build the cabs. Just make sure it is solid! Any or all of the hardware can be deleted or substituted or modified to suite your needs. Even outer dimensions can be adjusted within reason. Think of the plans as a chassis guideline that can be modified to taste. You don't have to put all of those holes in your braces or use the handles, a half inch roundover on the cab edges, add a cutout for a plate amp on the hatch, etc... Skram print.pdf skramcutlist12mm.pdf Skramcutlist18mm.pdf DXF files... Back Brace 1^Skram_TI x2.DXF Back Brace 2 ^Skram_TI x 2.DXF Bottom Braces^Skram_TI.DXF Bottom Brace^Skram_TI x 2.DXF Front Brace^Skram_TI x 2.DXF Mid Brace x 4^Skram_TI.DXF Top Brace^Skram_TI.DXF A^Skram_TI.DXF Back^Skram_TI.DXF Bottom^Skram_TI.DXF B^Skram_TI.DXF C^Skram_TI.DXF D^Skram_TI.DXF E^Skram_TI.DXF Front^Skram_TI.DXF Hatch Brace Small^SKHorn.DXF Hatch Brace^SKHorn.DXF Hatch^SKHorn.DXF MirrorSide^Skram_TI.DXF Double - Middle Two.SLDPRT Double - Middle Two.SLDPRT.DXF dxf_filelist.txt Single - Left or Right.DXF Triple.DXF Back^Skram_TI.DXF Bottom^Skram_TI.DXF E^Skram_TI.DXF Side^Skram_TI.DXF Top^Skram_TI.DXF Side_1^Skram_TI.DXF Top^Skram_TI.DXF

its finised. used the best quality multiplex for this part and its absolutely rock solid. its attached with pocket screws and theres foam in between the baffle and the cabinet. will update with test results soon, when the weather turns a bit. Greets

I couldn't help myself...

Using economy style plywood and some scraps for the 12mm parts i started construction here are some pictures of the process. First off thank you Josh the drawings are flawless! Sadly upon reaching this point my work shift starts again so will continue with the circular bit once i get back home. sofar everything is up to the millimeter exactly as drawn. Upon completion i would like to submit measurements. I think i have everything (software, calib. mic., mic, stand etc) Could anyone point me in the right directions on a step by step measurement process? I know theres a big chance this thread is dead, no one will be reading this but im trying anyway and like to thank Josh again for the nice drawings. Greetings Lex Breijs.

tried out 8 skrams cardioid outside setup, cancelling in the back was incredible. also the beam was very narrow, perfect for the situation. walking in and out of a zone of massive bass adds to the overall experience of the guests as well. i followed the MichaelCurtisAudio instructions for this setup and they worked like a charm. crossover was a bit higher at 100Hz ato go a bit more relaxed on the tops, and the skrams punch in the higher bass as much as the kick in the lower. also i was wondering how it makes a difference to stack the subs with the openings closer to each other compared to what we did, when the wavelengths are so long. i didn't notice anything weird the way we stacked them. i even considered stacking the top ones upside down, to space the stack. wouldn't that improve the beam pattern even more? we had no time for measurements. the skrams produce a super dry bass, ludicrous levels achievable even with a lesser efficient cardioid setup like we did. my guess is you could have a 1000 people audience with 8 skrams. (these are IPAL ready, just imagine the output!) two skrams fit on a europallet, a skram is possible to stack with two guys, the height of two skrams is perfect to stack a top on... they fit through any standard door, the driver is savely protected and a splash of beer won't do any damage either. a very convenient design.

Plans are in the beginning of this thread. Send Ricci money anyway

Filter out below the tuning frequency and room EQ. Maybe start with a high pass 4th order Butterworth at 20hz. Looks like there are other woofers to tune with in your picture - time alignment and eq should account if that is the case - phase alignment can be a challenge

I should have Dune pt1 measured next week. JSS

Jami, Thanks for the cnc files and sharing them! I'm sure it will be a huge help to some other builders. I know it probably took some time to put those together.

My first exposure to DataBass and I can honestly tell you this thread is a game changer! Thank you!

JAMI, you rock !! thanks for sharing your CNC work with us! For convenience I packed al your CNC files on a rar archive (for the couch potatoes like me ) SKRAMCNC_JAMIPACK.rar

So TDKR was kind of a mess, fidelity-wise. Lots of clipped tops make for a harsh soundtrack. Watching the movies back-to-back and with a surround system (down-mixing to 2.1 unless your AVR is doing it from an LPCM source will introduce dynamic compression by your AVR) is enlightening. I think TDK is one of the best soundtracks around, and TDKR could have been, if someone didn't just turn the gain up until every loud effect clipped. Another reason TDKR got such bad reviews here is this: This is the entire PvA for TDKR. But if you isolate the first 10 minutes: You can see it is a full bandwidth presentation with effects into the single digits. The rest of the film, however, is different: With a significant rolloff under 30Hz. The difference was easily heard and felt in a system that can reproduce under 20Hz. It is as if the ultra low bass knob was simply turned down. If you remember when TDKR was initially in theaters, a special 'Prologue' was released in IMAX theaters 6 months before the movie was released. It is my theory that this prologue was mixed independently and that mix was kept for the final film, and the rest of the film got highpassed when mixed. Unfortunately ALL of it is clipped. One of the worst cases of clipping in a movie I have seen, and heard. The first time I became aware of clipping was in Tron:Legacy, when I saw the BluRay and it was definitely different compared to the theater presentation. The effects dug deeper, but the sound was clipped in many places, confirmed by looking at the waveforms. JSS

You can see here that TDK only clips in one channel, at only two points in the movie: This is the entire movie, all channels, L/R/C/LFE/SL/SR in order 1-6. Just after the one hour mark, the center channel clips in one place (marked in red), and once at the end. TDKR, however, is a different story: As you can see, the screen channels clip nearly throughout the film, followed by the surrounds, then the LFE. It is an utter disaster, and the soundtrack is very loud because of it (one of the loudest I have measured). JSS

Christopher Nolan definitely has the 'wall of bass' sound design pretty well worked out. Ever since The Dark Knight Rises, he has used the technique a lot, especially for Interstellar and Oppenheimer, but he does clip the sound at times, sometimes as an effect. The only thing that was strange about The Dark Knight Rises was the fact that the opening has a completely different and unclipped sound signature compared to the rest of the film. With your LF setup, Nolan and Ridley Scott films will be very impressive. That is a lot of SPL capability there. JSS

Nice horns!

It is a super tough build if you've never done something similar before. Was my first speaker project and I'm glad I got a little assistance from a friend who is a carpenter master, even though I did most of it myself after he told me what to do. Cutting huge plywood panels without a properly sized saw sucks. I am just building another pair of Skrams, this time alone and I also moved so I can't use the shop from my friend. This time the saw was too small though so I could not use the lateral fence. A real pain in the ass. Measure 10 times, cut once... next time I would probably just use a track saw with guiding rail instead. More work with measuring and drawing but probably a better quality after all. But there won't be a next time, 4 Skrams are enough for me to handle and transport :-O The frequency response should improve after some time. You can also break the driver in with a white noise signal at moderate volumes for some hours. Cheers, Domme

IV now finished my first skram. It was a really tough build since I'm not a woodworking expert. My biggest mistakes are badly cut top, bottom and side panels. I need to find a way to accurately cut 4x8 plywood. Suggestions are welcome. The internal pieces were good as my table saw did the job just right. Initial sound testing is ok so far with a brand new Lavoce SAN215.30. It seems the deep bass(35hz and lower) could only be heard right up close to the enclosure. 20 feet away and I heard nothing under 35hz. I figure multiple enclosures would solve this anomaly 🤷🏾‍♂️. In any case it sounds good, I hope to paint it soon and then build a second enclosure by Easter. And I'm probably the first person in Jamaica to build a skram 😁 Many thanks to Ricci for this project 👍🏾👍🏾👍🏾 btw would you guys mind sharing your EQ settings?

So.. here are some measurements with front plate installed and up to 3 ports blocked with grain sacks (quite tightly) Measurements were done in an mostly open area, the speaker was sat on a few tonnes mill stone on some paper bags to make it very stabil. The cobble stones were too uneven. there is a highway nearby but during spl calibration the noise of the cars didnt surpasse 68 dB. the microphone was sat 360cm from te center of the cabinet. It was sat close to ten meters away from the building wich is round so we felt that maybe it would be less visible in the measurements. Please comment on the plots so i know what to look at. And thanks again to Josh Ricci for sharing these plans Regards Lex ckram Dec 30 molen meting volledig.mdat

Thanks for the advice, it worked out easier than I thought. I should have my first skram in time for the new year!

Dude. You're nuts. Haha. Definitely keep us updated on your journey.

Blu-ray is dead. Long live Blu-ray.

Oppenheimer: Level - 4 Stars (111.3dB composite) Extension - 5 Stars (8Hz) Dynamics - 5 Stars (28.9dB) Execution - 3 Stars by poll. Very powerful sound, very reminiscent of the great rumbles in other Christopher Nolan films, but at the expense of clipping in every channel except the surrounds in both the 4k and 2k tracks, which appear identical. Overall - 4.25 Stars JSS

Thanks Ill post more pics once i i get to it, and will upload measurements once im finished! Regards Lex

Here is a small guide of what you need to obtain accurate measurements of a subwoofer: Equipment: Microphone with a known frequency response (ideally an omnidirectional mic, something like a UMIK for example, but technically for this purpose any microphone with a calibration file for on-axis (free-field) sound will work) Audio interface Amplifier DUT (Subwoofer) A computer with REW, ideally something portable Measurement process: Calibrate your electrical chain (I'd personally not recommend this step to beginners as it's possible that you'll be making things worse. So if you don't know how to do this you can omit this step, since it's likely not gonna make a huge differency anyways if you have decent gear) SPL calibrate your mic (not needed if you just care about frequency response) Find a suitable open space to obtain your half-space measurements in. This means outside on a flat surface with no objects within a certain distance to your DUT (say ~10m or 30ft; parking lot for example or your backyard if it's large enough Place the subwoofer in the intended configuration with the radiating source (aka reference axis) towards the microphone Place the microphone one the ground and at least 4 times the widest dimension of the baffle/frontal area (typically diagonal) away from the cab, which would be about 4m in your case Take a measurement sweep in REW. Start with a low level to avoid mishaps and define a sensible sweep range (for example starting two octaves below the expected tuning point and ending two octaves above the intended maximum usable frequency, which would be something like 10Hz-500Hz in this case) Interpreting sweeps is an entirely different topic, but I hope I didn't forget anything here so you can obtain some high quality data!

I mean, these are all problems that can be solved. If you pay me a bit extra I'll modify the cab to your liking and then you can compare my price to the CNC quote you get Shipping would be around 100€, looking at a quick google search. I would just prefer to not have to paint it (the vinyl wrap can just be ripped off). But you'll have to get yours painted too, so either way you'll have to figure that out.

Well just think about it.. the port is how wide? 600mm? Now you increase bracing thickness by 18mm total (three braces iirc). So you lose 18mm of port width from your 600mm which is 3%. Make your port area 3% smaller in hornresp and see how much the response changes (hint: no).

The thicker wood will decrease volume internally, of the horn, and the ports. Will it have a noticeable impact? I am inclined to think it will not, but doing the math is the only way to be sure if you will care about the change for your time, effort, and cost.

Two weeks ago I hosted my second public soundsystem show along with a friend. The pair of Skrams I built (loaded with NSW6021-6s and powered by a K20) played super loud and clean. We received a lot of gratitude from the crowd and other local soundsystem crews praised the clean sound of the system. Unfortunately we had power issues (to be exact, there was no power at all coming from the designated socket... ouch!) and after we fixed it there was not much time to do a proper soundcheck but you could easily tell that most of the bass was coming from the Skrams, and we're not even talking about low-end performance. It was such a difference when I went to a quite popular local techno club last weekend. I could have cried about what is thrown at you after you have to pay 15€ entrance fee... I decided to upgrade to 4 Skrams this winter. That's all my van can handle and it will already be super cramped... my friend is selling his horns and wants to upgrade to Type O paraflex cabinets with 21" drivers. I tried to persuade him to bulid 4 Skrams instead but he prefers the more classic/roots look of the type Os. Anyway, once we are done building them I will drive on a field and compare them. Two cabinets, one measurement method.

Glws! Wish I could get it across the pond!

Hi Again, I have my 4 Skrams coupled together laying on there sides. Supposedly I get a 6db gain having the subs coupled the way I do. https://www.instagram.com/p/CxHiRfTORnW/ https://www.instagram.com/p/CxBrd97yXa9/ https://www.instagram.com/p/Cxrt5nxLvu5/?img_index=1 BC21SW152 4 ohm drivers I am using 2 QSC PL380 amps in Stereo My generator is a gov surplus Onan Quiet Diesel HDKAV 6000 watt. I am starting to max this genny out, and when I add my lasers I have to put them on a differnet generator. I do not use any Dampening because I don't want the Playa dust having a media to cling to inside. I am Running Meyer UPQ tops with a 15" drive and 4" horn for my Mains, and Meyer UPJ's with 10" drive and 2" horn for my Fills. This System is OFF THE HOOK!!!! Thanks again Josh, This years Burning Man was fantastic because of your design!!!! Edna is starting to get a big following of BASS HEADS!! YOUR DESIGN KICKS ASS!!! THANK YOU!!!

THANK YOU for sharing the skram! after making an initial two skrams, i`ve just finished another six. eight skrams in total, loaded with lavoce 214.50 1700W/8ohm http://www.loudspeakerdatabase.com/LaVoce/SAN214.50 i`m running two channels with four skram cabinets each at two ohms from a single crest pro9200, 8sqmm cables instead of breaking the woofers in freeair i had them broken in last weekend with a live analogue acid tekkno set and tekkno DJ. there was too much sub, so i rolled off at 40Hz which is typical for tekkno sound systems, and reduced my low shelve boosts i use for bassmusic and personal listening preference to 0dB, and everyone was happy with the bass tone. anyhow... in september i will have D&B and bass music, techno, schranz and an eighties events. these beasts will move alot of air! next step is making vent shutters, so i can flexibly tune the skrams, an initial test showed promising infrasonic results. the idea is to use a subharmonic syntheseizer so i can fiddle around a bit during the parties. plenty of headroom to tune to the infrasonic... also i will venture into outdoor cardioid setups now i have enough cabinets. i`m looking for volunteers to haul cabinets. if i ever have the chance to do outdoor measurements i will post those here as well. btw. the grey cabinets will still get a finishing paintjob

YouTube or your choice video feed will help. Start with understanding how to rip sheets of ply and using a plunge router. You'll want to invest in a lot of clamps. A quality surface area to enable precision and comfort will go a long way as well.

@Ricci send me a message!

Sealed subs are not suited for live sound applications. They won't have enough headroom down low

What you're talking about is compression and expansion. There are a lot of factors that can cause compression in subwoofers (a change in input gain results in a *smaller* change in output change), like the voice coil getting hot (impedance rises, so the same amount of voltage generates less power; also known as power compression), air velocity in the port getting too high (port compression), the driver reaching excursion levels where the magnetic field strength gets lower (over excursion) or simply the amps' limiters kicking in, to protect the drivers from destroying themselves. To express the effects of compression with your wording it could be something like: -volume change from 70% to 75% is very large -volume change from 75% to 80% is small -volume change from 80% to 85% is imperceptible Since you describe the opposite effect, if I undersood you correctly, this doesn't apply, since you're seemingly describing expansion. There is only one cause of expansion in subwoofers that I am aware of and it is minute. So, if expansion doesn't happen inside a speaker, what's the thing you're hearing? I think the explanation is fairly simple: it's the lack of compression. You're not used to hearing capable systems that can reproduce content with their full dynamic range, in which case the SKHorn would be one of the worst choices, since it's one of the most capable subwoofers out there. Another explanation would be bad deployment and what you were hearing at "75% volume" wasn't the subs being super loud, but everything distorting badly (which will be perceptually louder, since our hearing is more sensitive at higher frequencies and distortion will mostly produce frequencies higher than the stimulus). Most venues and festivals I mix have underdeployed systems and/or are badly set up. The last festival I mixed at had a stack of 3 2x15" subs on either side of the stage. All three cabs were different, which was the first point of concern, but the biggest issue is the physical deployment: you get terrible lobing and super uneven bass response across the audience (see my recent post on AudioScienceReview on this topic). I haven't experienced the effect you're describing. Most of the time I'm fighting compression and uneven response across the audience. The issue you're describing can have many causes, but "subwoofers being overly dynamic" it is not. My answer to that question would be "source content" as per the explanation above (lack of compression; habitual). The difference between 1000 watts and 4000 watts will be 6dB in theory. In practice, some compression will have set in at 4000 watts of input power and it will be less than that at certain frequencies.

Kyle let's have a conversation soon. I can take over the payments for some time. I'd really hate to lose everything at either the main site or the forum, but since I've been spending times with other endeavors for a few years and don't have time to post like I used to the traffic has gone downhill. Perhaps there is an interested party at another website or forum that would be interested in taking over? Unfortunately for the future I don't know if or when I'll have time to do testing like I used to. I have far too much on my plate. I have no web developer or programming skills and no time to learn it either so that's another piece of the problem.

Some carpentry sins have been committed due to time constraints and lack of both quality tools and experience, but nothing I don't expect PL and Bondo to hide. It's an intimidating build to do by hand, mostly due to the bracing, but I wanted to do it "right" and I expect the cabinet is going to be stiff as hell. Got some 21DS115-4s on deck and if all goes well they'll be at full flex at an event last weekend in June.

Here's my random thoughts. Shorting sleeve is mentioned but the 1kHz Le rating is way up there at over 2X the Re. Also the shape of the impedance curves shown indicate a very sharp increase in impedance vs freq above the minimum imp above resonance. Indicates a lot of inductance also. Heavy 5" coil and a huge motor with lots of steel. They have not posted the Zma data for download yet, which would allow it to be analyzed with Bolserst's semi inductance excel program to back out the semi Le specs for modeling. Shipping weight is listed at 115lbs. I suspect these drivers are in the 90-100lb range. Two or 3 times as heavy as the pro 21's. Can't see anyone using the Vortex 21 for pro audio work with that kinda weight. Drivers that heavy are a PITA to deal with especially in multiples. Imagine a double 21... Both drivers seem to be nearly identical. They model almost exactly the same except that the Vortex has slightly higher efficiency and upper bass due to the lighter mms. Most of that is probably just from switching surround types and perhaps the cone or dust-cap. The rest of the spec comparison and specs lead me to believe that the motor, frame, coil and spiders are identical. It's possible that the roll surround is much better behaved at high excursion than the traditional pro type (less noise more linear). If not I don't see a reason to pick the Kraken other than if you want that type of look. The Vortex is higher sensitivity and efficiency with apparently the same amount of excursion and it's a tiny amount lighter. Judging from the cutaway pics it looks like the top plate is about 15mm and the coil is about a 45mm wind height. Coil overhang would give 15mm overhag with no adder. 1/3rd gap adder would put it at 20mm one way which is close to the claimed spec. The coil would leave the gap at 30mm one way. Unless there is a lot of fringe field and overshoot the maximum excursion is done there and also sound horrendously distorted by that point. Of course I'm speculating based on an un-detailed drawing but this should be close. Spiders don't appear to be mirrored. There is mention of a warning system to prevent damage. I believe this is the ring shown under the bottom spider sticking up above the top plate. Looks like the bottom spider will contact this a few mm before the bottom triple joint would contact the top plate. This will probably sound very bad but not be immediately damaging. It looks like the bottom spider triple joint would contact the top plate around 30-32mm in. I'm guessing the spider will contact the ring around 27 or 28mm incursion based on that. Since the coil would leave the gap completely at 30mm I don't think it will be easy to push these drivers that far anyway. Spec wise I think these look good. They have a low Qts and high efficiency. EQ is used on everything these days and the goal is usually more bass from less space. The pricing also looks good especially in multiples. My biggest gripe would really be the 100lb weight followed by the question mark of how bad the inductance is.

I haven't heard any Danley speakers, but I hope to some day. I expect they sound quite good. Using EQ you can change the sound of the Skram, for better or worse. The Skram response simulated in Hornresp and exhibited in your measurements has a bit of a hump around 95 Hz, which is likely to dominate the character of the sound. EQ down that hump, and the bottom may come alive. Ideally this can be achieved while retaining (and hopefully enhancing) the punch, but finding the ideal EQ ideal may be tricky. If you apply such EQ to the subs only (instead of the whole signal), you may find that a different crossover frequency works better. For example, crossing at 75 Hz reduces the emphasis from the 95 Hz hump (it's still there, but less) compared to a higher crossover frequency, but if the hump is EQed out, the system might sound good crossed a bit higher, like 90-100 Hz.

Here is a 3D Sketchup file for the Skram if someone is interested. Bracing is missing. It's rounded for metric units but it should not change that much compared to the original one : Became : 610mm x 813mm x 915mm Skram.skp

Played around a bit with some frequency sweeps at high volumes, the boxes sound really solid, no rattles or vibrations from the caster wheels. They sound clean and powerful, cant say I think the low end sounds any better or worse than the othorns and the measurements seem to show that they are clean much higher. All 4 playing together are damn loud, I don't hear any real reduction in volume intensity until they drop below 27hz or so, but still have pretty solid output down to the low 20's before they really start to fall off. I've sold off my old rcf tops but my danley sh46's are supposed to be here monday or tuesday, ill get them playing together shortly after that and give you guys some impressions with some music played through them.

OK. I'm Now decided to build the amazing SKRAM. Like always you're so helpful Ricci, Many thanks Mr. designer speaker genius. 😉

For anyone who might find it helpful. Attached are cut lists to build 2 skram cabinets. I tried many combinations of 4x8 and 5x5 to find the route with the least leftover waste. Factoring in cost of materials for me in Canada, $73 per 18mm 5x5, and $105 per 18mm 4x8, this was the cheapest route... your mileage may vary depending on material costs. Will require 6x 5x5 of 18mm and 1x 5x5 of 12mm costing about $487 Canadian. I used the Cutlist optimizer app. All pieces are accounted for as rectangles, some finish cuts will be required after the fact Skramcutlist18mm.pdf skramcutlist12mm.pdf