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Thanks for the link to Limiter guideline. My active version of the Skram's is done. I just need to load the Eminence's and setup the limiters.

OOPS I DID IT AGAIN, and built 2 more SKRAMS making this 4 SKRAM's in my collection. I decided to do this because I upgraded my tops to Meyer Sound UPQ's and needed more BASS. Now I just need to find a amp and more money to afford it. B&C 21SW152's cost 950$ each, 200$ more than pre-covid. My QSC PL380 amp is 700$ more now and backordered.

I don't know what your definition of "useful" is, but if you are space constrained, then I think you will find SKRAMs to be much more useful than the usbv2s. As a broad generality, the total space requirement of your cabinets will be dominated by the low-end elements. If this is not the case, then it almost certainly means that the system is unbalanced and that the low-end is relatively insufficient. This is true even for a "balanced" vs. intentionally bass heavy system. If the particular form factor of the SKRAM does not stack well in your truck, you can consider other designs like the CKRAM or a custom BP6 and/or vented cabinet with a more "useful" form factor. You really can't get away from the total space (enclosure volume) requirements however. Also, combining multiple acoustic sources is not merely a matter of dealing with phase issues. To oversimplify, separate acoustic sources don't really play together. A crossover is a fudge. Some XOs are better than others, but unless they are extremely precise, they are imperfect and the effects on sound quality are very degrading. Of course, one cannot reproduce the full audible spectrum (especially with high bass output) from a single type of driver, so crossovers are a necessary evil. I believe crossovers should be avoided where possible. Also keep in mind that you'll likely want to substantially bass-boost the frequency area under the last crossover, regardless of where it is. I'm not going to get into my hypothesized reasons why this is preferred, but I doubt anyone here will argue with me about this point. If you need a stack of mid-bass bins to achieve your output requirements, you're gonna need an insane amount of bottom-end to really deliver that "deep sound" you're looking for. In reality, you probably don't need that much mid-bass, and if your deep bass needs are sufficiently met by an array of BP6 or vented cabs with high quality pro-style drivers (not too heavy---with controlled inductance), then what you need in the mid-bass up to 100 Hz (or whatever the cabs can do cleanly) will be more than adequately provided by such cabs. Overall, most people here would agree that the Othorn is largely superceded by the BP6 designs because of their wider bandwidth capability and much better looking upper-end response overall. (The construction is also simpler!) I don't doubt that there are exceptions, but these will tend to be very niche.

Heres the cutlist for 2440x1220 ply Skram 12mm cutlist.pdf Skram 2440x1220x18mm cutlist (1).pdf

Based on the TH118's spec sheet I'd guess it's giving up some low end (its F4 is at 37Hz) for a bit of added sensitivity at higher frequencies, which might mean that in its passband, the TH118 would be able to keep up with the Skram, but below 40Hz the Skram will outrun it pretty quickly. I didn't look at cab volumes and the best data point would be CEA2010 ratings for both made by the same person, so take this with a grain of salt. Any horn-kind of design doesn't lend itself well to going deep while being space-efficient, I feel. The Skram is a hybrid, which kinda gives it the best of both worlds.

My pair of Danley sh46 are a pretty good match for 6 skrams, but they still outrun them a bit. I think 8 skrams would be the perfect balance. I've got another pair of skrams in the cutting phase, and another pair of sh46 on the way. Lots of skrams popping up in my area, there will be 12 in my city pretty soon, as well as 8 or 10 on the island. Been some planning discussing how to get them all in the same place sometimes soon I'm planning an after summer report soon, was hectic busy with lots of great gigs

Hello, If you ever use this setup again, you shouldn't use the mini scoops and just cross your Skrams way higher. If those BPHs are ES18, you can (and should) probably cross them at 80hz directly with the Skrams. Using 3 boxes for the 25hz-220hz seems counterproductive to me, especially if you didn't put them properly in phase. If you build 2 more Skrams, even if the boxes don't have the same drivers inside, let them play together, the phase should be pretty similar, you will win more than using them crossed separately

Hello ! Took me a while but I finally remembered to save my measurements to share those with you. They are worth what they are, I'll try to get unfiltered ones the next time. So here is an uncalibrated measurement of 2 Skram units, 21DS115-4 loaded with a 2nd order BW filter at 24hz and a 4th order LR filter at 108.8hz. (No correction EQ). The subs were 8 meters away. Considering how flat it is with the LR filter, you can imagine how the curve is rising after 50hz.

By "lack of cone control", do you mean non linearity in the translation from electrical to kinetic energy or do you mean cone flex? The former can be remedied by a stronger motor, the latter through a stiffer cone. Both problems are challenges to the designer, not to the end user. Any properly designed driver will play predictably based on the Klippel graphs. For B&C drivers I think it's the Xvar value, which is a general rule of thumb for when the driver behaviour will transition into non-linear territory. If this was a huge issue, big drivers wouldn't be so popular.

Just unloaded the wood for my 2 SKRAMs, starting the build on Thursday... oh boy 😻 Unfortunately I don't have access to a CNC router so I have go with lamellos instead. When it's finished I will probably reinforce some critical edges with glass fiber fabric & epoxy resin. That has to do for now...

PM90 by Peter Morris is a well designed and well reviewed DIY top cab. If you are looking to build something. Not cheap but you know how that goes.

pm sent

Start with 2 skrams. Then sell 4 of existing 'old' subs. Then do 2 more skrams with raised funds. Then sell remaining old subs.

Or buy a lot of pa460s - put them in a sealed cube enclosure - with dual, dual opposed boxes (4 sided with drivers). They'll be light, easy to stack, and go deep, but will take a bit more space. Or just build SKRAMs and toast a few with Ricci for sharing an excellent design.

I can just echo the others here. Once you get proper subs to supply the bottom end you're looking for, these cabs will also be able to replace your current subs. And if I was space limited, bass horns would be the last thing I'd load into my truck. IPALs it would get, in tiny vented cabs.

Maybe you can build some SKORNs or SKRAMs (see other threads on this forum) and plug one of the vents to get down into the 20s? Though again if you do this, you won't need the USBv2s at all anymore as those cabs run up to 100 Hz or higher.

By the time you have enough Othorns to keep up with the midbass of the other horns, you can get rid of the USBv2s entirely. Beisdes that, the Othorn isn't an infra design, they will probably not add as much as you'd hope for. If you want infras, you might want to look into a custom vented cab tuned to ~20Hz or so, but you will need a lot of juice (and a lot of cabs). And then ask yourself, do you even need them?

I have similar thoughts based on the design work and simulations. In a lot of ways they do seem to be a vintage type of design, but taking advantage of modern driver advancements. Big, leverages a lot from one driver, should be loud and efficient over a narrow band, cabinets do not lend themselves to going low especially considering the considerable size, potential upper response phase and ringing issues could limit the upper range usefulness. Note: I've not actually seen good measurements on a top end example and have not heard or used any examples my self yet. YMMV.

Where can I find measurements of these subs? They seem to be as big as a double 18 while only having one driver, looks pretty oldschool to me when amps didn't have the power on tap than they have today.

What would the sonic differences be, if both amps produce the same frequency response and produce less distortion than the speakers do (which they do, unless they're defective OR clipping)? If this listening test was a DBT with perfectly matched gains (with a voltage meter) and ONLY the amps were swapped (ideally via switch in rapid succession), then the comparison is fair, but as soon as it involves sighted bias or any other uncontrolled variables the test is invalid.

I second going for the better driver, more of an investment upfront but it will never leave you wondering what you are missing. Good luck with the build! I'm currently piecing together another pair.

It literally 2 comments above yours lol

I think the combination of SH46 and Skram is just simply a great pairing sound and power wise. The horn loaded upper bandwidth of the Skram really compliments the sound character of the SH46, together they sound very clean with well defined impact, some would describe it as having "fast bass". For an example, If there is a genre of music that I've heard sound shit on a lot of sound systems, its psytrance. Something about those fast upper bass notes just seem to show the warts on many sound systems. The Sh46 Skram combo sounds better on psytrance than anything else I've ever heard, F1, Void, Turbo etc etc. On top of that, one of my biggest rental clients is a long standing local crew that specializes in bass music, dubstep, drum and bass etc. They like the Skrams so much they are now building their own. For reference, this same crew was previously a heavy renter of PK sound, which some people say is the yard stick for bass music subwoofer's. So yeah, the Skram is an exceptionally flexible cabinet, it really can do all the things well. To your original question, I would add that when my 6 Skram's start touching limiting, the Sh46's still have a few db of headroom to go. Personally I'd say the appropriate sub to sh46 ratio would be 6 to 7 skrams per pair of sh46. I've got another pair of SH46 on the way, with a couple more Skrams in the cnc cue, if I have another successful summer next year maybe Ill cut up another 4. Th118 vs Skram, I think Josh would be a better person to answer that one... they must be fairly close in output overall, but I'm just speculating

Welcome to the Rabbit hole of BASS! Correct me if I am wrong with any of this....... I use the B&C 21SW152's at 4ohm with a QSC PL380 amp. This amp drives 2 SKRAMS, with room to melt the coil if you turn the clip limit switch off.(I know from accidental experience) I have thought about running 4 x 8 ohm drivers with this one amp in series as well, but figure that would be pushing the amp alot and I typically use the amp at Burning Man and it was %*&#^@ hot this year so it prolly would not be the best idea as the amp would be turned all the way up instead of running at 50-60% like I currently am. I pair the 2 SKRAMS with Meyer Sound UPJ's and run the tops at -6db for most outdoor venues and -10db for most indoor venues (unless it gets really crowded, then I go to -4db outdoors for the tops and -6db for indoor.... Otherwise the tops are Too Bright). I have Meyer Sound UPQ's on order and will need to double my SKRAMS to keep up with the UPQ's output so I plan on building 2 more of these unless I just go straight to the Powersoft 30" M-Force subs but they are 12,000$ a pair with amp and you have to wait a year to get the drivers. If you are going with 6 SKRAMS you will need quite the tops to compete as these Bass Bins output some serious BASS!!! Jay on here has quite the system with I think it was Danley tops, he might be one to DM. I would always cut in the grooves to build these boxes, serious forces going on here and you need the cabs to be rock solid, make sure you use the best Baltic Birch you can find, PU Glue and lots of pre-drilled screws. One option if you do not have access to a CNC router is to find a local makers space that has one, I used the TRUCKEE ROUNDHOUSE shop bot to make mine. GOOD LUCK AND MAY THE BASS BE WITH YOU!

Hello DJimbo and welcome. As far as assembling the cabs go. Clamps and more clamps are your friend. Other options that help are a brad nailer, or a pocket screw kit. If using the 21SW152 drivers best results will probably be with 2 to 4kw of amplifier rating per driver. Any more might get sketchy over long periods of time. Less would leave some of the dynamic capability on the table. I prefer to run fully bridged amp channels on bass when possible. Smoothing out the corners might help with airflow in an ideal scenario but it has drawbacks. It reduces the internal volume utilized by the driver. With bass size (air volume) is king. The Skram is a vented cab on the back side so it's a traditional ported arrangement there. Large flares and circular vents would be beneficial ideally but would greatly increase the size of the cab and its complexity. The front is a short horn/expanding slot. The same applies here. Ideally it would be a totally smooth, straight path, but packaging it into the cab dimensions requires compromises. At best these would be small gains in output / noise reduction, even if it was built ideally with a totally different (much uglier and unwieldy) form factor. I hope this explains why most bass cabs do not bother with dramatic smoothing of the air path. It comes with other tradeoffs.

If you have a CNC at hand you can route some grooves which should help with assembling and gluing process. I did not have one so I used lamello joints for easier assembling and increased stability. This was my gluing order: 1. Baffle and horn 2. Base with ports 3. Braces 4. Outer sides It was a pain in the ass though. I am glad my friend -a master carpenter who owns the workshop- helped with the gluing and I never knew that you can get sore muscles in each and every finger. You are going to need a lot of large and strong vices, too! Gonna post some pictures later on how it went. From the fluid mechanics perspective i would say that you are moving large amounts of air back and forth repeatedly in different frequencies all at once. There will be turbulence all over the place no matter what you try. Even though I was also tempted to round of "F" I ultimately went with the original design (well almost...) Good luck!

Hello Shayne. That is a lot of power. Whether it is too much depends on a few factors. I'd suggest doing a bit of experimentation before running it wide open for long periods of time. Remember doubling power is only 3dB in an ideal case.

Only in the DS3 configuration but they do it for a reason Announced frequency response -3db (we can suppose these are once EQed) : - InfraBass 218 : 25Hz - 80Hz - DS15 : 90Hz - 270Hz - F215 : 50Hz - 280Hz They couldn't cross the InfraBass218 directly with the DS15 so they added some F215 in between. But that doesn't mean it was the best solution, they are just offering what they can with their range of products. In your case (and without any marketing EQ) : - Skram : 26hz - 150hz - 18" BPH (estimation) : 55hz - 220hz You don't need the mini scoops as you can cross the 18 BPH directly with the Skram. You can add them if you want for sure, it's your system, if you want to take more bins, more amps and have a harder time to put everything in phase, you can, it's part of the fun 😁 I'm just unsure about the "real" gain you'll acquire from this.

Hello again! I don't know what the weather is like in your place, but it's still hot here in Croatia. A week ago we took the sound system out to the festival, but unfortunately we didn't have 4 SKRAM as planned. Otherwise, what I would try is that the lower SKRAM work from 25HZ to 60HZ and the upper two from 60HZ to 110HZ.. Why is that, since in one box we have 21B&C SW152 which would be for the lower range and 21RCF N551 which would be for the upper range(personally). Normally, we'll try how it would be if both boxes worked at the same frequency range and one more thing we didn't try is to close two more output ports from the lower SKRAM to get the depth, even though they still go quite low and sounds nice. Currently, as you can see in the picture, instead of SKRAM, we put mini scoops that did a great job. I can't wait to do it , listen and measure the boxes to see what happens with the phase between the different drivers and how its sound overall with 2 more but I think it will be much better because as Ricci said, it is better to have more same boxes like this that work the whole range from 30 to 110HZ than for example like in the picture with mini scoops. I need to hear that combination to be able to make a comparison but I think it will better w SKRAM since there are no different boxes although this was very mellow tight and clean Other two almost finished ! SKRAM 21' RCF N551 (25-55) "MC2 E45 Bridged" MINI SCOOPS 18' 18SOUND LW2400 (55-105) MC2 E45 Bridged BPH 18' 18SOUND LW1200 (105-220) "MC2 E25 Bridged" F1-DS210 (220-18K) "MC2 E15"

That's my bad PC. My inbox was full. I've cleared out some space. It should work now.

Hello everyone, first time posting here and I'd like to thank Ricci for the putting the Othorn plans out in the world. Living in Denver I have have been blessed to listen to the world renowned Basscouch Soundsytem (by Jeff Bailie) at The Black Box wich features 8 othorns and 4 Tannoy iq10/18b. Now the time has come to build ourselves a "small" but robust stereo stack for house/warehouse/renegade parties. Othorns are a no brainer for 27-80hz (already started on our first cab) and we are leaning towards the Peter Morris PM90's for our Mid/High down to 100hz leaving a hole from 80-100hz. I have been searching around for some midbass designs but apart from the HD15 from speakerplans im not too sure what to fill the gap with that can match the quality of our other choices. Is there any midbass designs that people have ran with Othorns and would recommend for a 1 box per side stack? If our goal is not sheer output from the PM90s could we get away with running the Othorns to 90hz and letting the PM90s take over from there slighlty lower than recomended? I am at the beginning of my DIY/pro audio journey and any help would be much apreciated, thank you for your time.

Hello Ricci, I had the opportunity to get some fresh measurements this week-end. The 2 skrams, 21DS115-4 loaded, were superposed horizontally, mic on the ground at ~3 meters. I did measure one cab (the one sitting on the floor) and two cabs. No LPF, my HPF was set at 19.7hz (as low as my processor was able to go, I think it was a -24dB BW but looking at my precedent curve I may have put a -24dB LR by inattention which would explain the slighty higher -3dB point on those) These are still uncalibrated btw ! Green : 1 cab | Red : 2 cabs

Cone flex can be a problem but only in drivers not designed adequately for high pressure applications. It has not been a problem with any of the cab designs I've made/tested/used with 18" or larger drivers. There is a reason that modern high power sub drivers have a heavy mms and stiff suspensions. It is required for strength, control and power handling. The cone on a larger diameter driver must be stronger / thicker than a smaller diameter unit, the voice coils are massive to handle large power inputs, the suspensions are stiffer and heavier to keep things centered and prevent overshoot, fight against gravity over time, etc. Most pro audio and car audio subs are built to take a lot of abuse. This is why a pro audio 15" woofer might have a MMS of 80g but a true subwoofer might have an mms >250g. Even though the 2 might have a similar FS and Xmax rating or even power handling, they are still suited to different jobs. The 80g 15" woofer is not going to fare as well in a FLH or other high output high pressure loading.

Interesting experiment for sure. My personal take away is use 240v if available. If you don't have access you can still get solid performance from 120v plugs, just ensure you aren't overloading your amplifiers with too many speakers. On 120v I run 1 amplifier per 2 skrams on a 4ohm load and can achieve likely 90-95% of what can be achieved using 240v. don't expect to get the most of tough 2ohm loads from 120volt. Of course with 120v you will draw twice the amperage, deal with more heat and that may but extra strain on your gear.

Finally spent some sheckles to have a proper power panel build to run my amps on 240v which isn’t super common up here in most venues. While subtle, things felt a little cleaner and tight and amps ran noticeably cooler. We knocked some bottles off the wall of the bar which was a first so it seemed to have helped https://youtu.be/rqMiTLL15s8

Starving to see your construction pics 😻 hope you can share some audio measurements when you finish the cabs !!

I love how many people have built these subs! Also, I just love these subs as well. https://www.instagram.com/tv/CalY8Y1Bi6D/?igshid=YmMyMTA2M2Y=

You mean dado joints like on this board? I use them mostly to make the assembly easier, since it's hard to get the position wrong when everything slots right into place. It doesn't help much with structural integrity unless you do like 10mm or so I'd say. I do 3mm too. Doing this without a CNC is a massive waste of time imo. I only drew a sketch on to the floor board when I built my Skhorn and went from there.

I'm pretty happy with my 21ds115 powered subs (similar to the Skrams I guess, just a bit smaller) and l-acoustics ARCS wide tops. PM90 components are obviously top of the line, but I personally prefer scalable solutions (the ARCS wide can be used as single 90x30° loudspeaker or in a fixed curvature line array with ARCS focus (15°) speakers). PM90 won't achieve uniform audience coverage over a large area, but it'll do exceptionally well for small clubs or small outdoor shows. Or when you just want higher SPL closer to the stage.

The PM90 would be my go to choice if I was doing PA for a living on a budget. Other than Peters Line Array I would say its the best sounding speaker I have heard in a PA lineup. I got to hear it compared to a 10ft tall Krix pro cinema speaker and it sounded quite similar at 1/4 or less the size. PM90 only goes down to about 120hz but that is a lot of fire power in a small package. Sadly I havent started building my Skrams yet due to pricing of lumber and divorce. Hopefully will start towards the end of this year.

No, even the Skram won't make a 21" driver sound like four 18". Looking at the specs it should outperform or be on par with a single 828 though, as long as the Skram has an adequate driver with adequate amping. That depends on your subs, your tops, the location and the kind of show you're producing. But I guess 2:1 is a good ratio for these kind of shows. Also, the guy you're describing had 4 18" drivers for 2 tops, so it's 2:1, isn't it? No, not really. Indoors, setting up subs in different locations will make for a better spatial average across the room. In wide rooms or outside, where some of the audience stand at the sides at a heavy angle to the PA, you'll run into lobing issues unless you stack your subs (you'd stack them center). But since your room isn't that wide and I suppose the subs were set up rather close to the side walls, you won't have to fight lobing. Also putting tops on your subs means you won't have to bring stands Even more of a reason to get high efficiency PA drivers over a bunch of cheap car audio ones. It means you'll get a few more db out of the subs within your available power.

the worst is that in 2022 prices skyrocket high and salaries have not. that su.... big time. how many watts you need to feed the skram's, and what is the headroom you need to have .

By saving a few bucks on drivers you'll end up having to bring twice as many cabs to a gig. You'll end up spending more on wood than you saved on the drivers. Plus having to haul more subs around. Definitely not worth it imo, not even taking the difference in sound quality into account.

iirc the LaVoces were in a parts express deal for 400 flat or something, 3 years ago. I paid 410$ for my 21DS115's. Now they're around 650. That's up over 50%... Imo it makes no sense to build the Skrams if you intend on putting non ideal drivers in it. A good subwoofer is a good subwoofer, but that's the entire system of driver+cabinet. Even if the cabinet design is stellar, it'll make a bad subwoofer if you don't put the right driver in it. That's also how DIY got a bad name over here. And just outright bad designs of course. Build something else if you wanna use other drivers or design a simple vented cab if you have a specific driver in mind. Designing a vented cab with a slot port is really simple.

I finally got my hands on this driver. The coil is so huge , the wire thickness seems to be 0.45 mm and 4 layers, it's coil is twice the wire amount of B&C21Ipal (of course, not the same efficiency) . It will take loads and loads of power. The excursion reached is probably over 8 cm peak to peak in this video, using a K20 at 16 hz

Yes, a synergy type horn or for patent sake, a unity horn. I don't have a link to it because I didn't bother to make a build thread. It's my own mix of ideas based on Art Welter's SynTripP, B. Waslo's spreadsheet and the input of Chris A. on the Klipsch forum. I've built two cabs with 12" drivers and finishing up two more cabs with 10" drivers. I didn't port any of them. It seemed to me that 4 drivers would have enough clean output with moderate EQ without having to deal with ports. I'm very happy with the results. I'm using the Eminence TexTreme CD crossed around 850hz. It's certainly usable a little lower but to my ears it's a little less "honky" at high output.

Have a bit of an interesting field use report for my Skrams. I recently added new processing to my system using an XTA DPA 100. It’s a pretty interesting 4 channel amp, which I am using to bi-amp my Danley sh46 cabs. It also featured 4 channels of output control to add processing to my slave sub amplifiers. I used the information within this XTA/MC2 document on limiters to set up protection on my sub amps. https://audiocore.wpengine.com/wp-content/uploads/2018/05/XTA-Application-Note-DPA-Amps-Limiter-Settings.doc.pdf using the chart within this document it says to set up the 21sw152 at 86.9 volts for limiting, minus 1db for safety margin. Having always been a little hesitant on knowing just how hard I can safely drive my Skrams I added a 2 wire thermocoupler temperature sensing system to 1 of the cabinets to monitor magnet temperature. 1 wire is mounted on the external circumference of the magnet, the other right next to the vent on the end of the magnet body. last night I provided sound for a local dubstep crew, 7 hours of continuous deep sine wave bass. Peak volume was held for about the 3 final hours of the night, at maximum I was running about 2db down from where limiting would engage. Monitoring throughout the night, magnet temperature peaked at 44 degrees Celsius. This was also in a packed sweaty room that was raining condensation from the roof. pretty interesting to get some real Information about what the drivers are doing deep within the skram cabinets under real world conditions. I had previously come across a statement from Bennet Prescott who works with B&C saying that the 21sw152 can sustain 100 degrees magnet temperature without thermally damaging the coil. Previously I had been limiting these drivers to around 50 volts, it seems that in the Skram alignment we should be able to safely push them beyond that a bit without getting too much temperature build up. This of course may change for other types of music, I will continue to report back when I can speak to temps I’m seeing when doing other types of music shows. Data is beautiful. Always a pleasure getting to flex these cabinets, in a town where double 18’s rule, the Skrams are raisins eyebrows and making lots of new fans.

Blowing out the cobwebs today

Well, I finally got mine built! Lol took a while but life got in the way. I'm also just staring to do my fiber optic ceiling, so multiple things at once!. I should have the subs up and running next week. Drivers are DS115. Just getting duratex. Will be my nearfield subs lol.

Welcome to the forum. Impressive work! Thanks for the kind words. I'll check out your links when I get time. Looks like a cool project. I don't have any V-carve files. I don't own a CNC myself. All I can help you with is Solidworks files or other 3d cad file formats if that helps. Maybe one of the other guys will be able to provide some.