Domme Posted January 2 Report Share Posted January 2 15 hours ago, lawbadman said: 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? 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 1 Quote Link to comment Share on other sites More sharing options...
jay michael Posted January 19 Report Share Posted January 19 Cant stop, wont stop. Quote Link to comment Share on other sites More sharing options...
chrapladm Posted January 19 Report Share Posted January 19 3 hours ago, jay michael said: Cant stop, wont stop. Probably mentioned before but which CNC do you have? And is that a fancy ATC? Very nice either way. Quote Link to comment Share on other sites More sharing options...
peniku8 Posted January 20 Report Share Posted January 20 23 hours ago, jay michael said: Cant stop, wont stop. Whoa those edges look rough. No compression bit used here? Quote Link to comment Share on other sites More sharing options...
Apade Posted February 9 Report Share Posted February 9 Thank you for the effort of designing this cabinet Ricci! We are looking forward to hopefully build some SKRAM’s soon! We are going to start off with two and build another two to the end of the year. 21DS115 seems like the cheapest option here in germany at the moment. Do you have amplifier suggestions to power 2 and later 4 of these beasts? We dont care if it‘s one amp to power all four, two amps per two cabs, or even one amp (Bridged?) per SKRAM. Also, do you recommend 8 or 4 Ohms? Quote Link to comment Share on other sites More sharing options...
Jami Posted March 14 Report Share Posted March 14 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 6 6 Quote Link to comment Share on other sites More sharing options...
nightingale Posted March 21 Report Share Posted March 21 Hi, my name is Peter and I'm living in Austria. 4yrs ago I built 2 ported subs with 18NLW9601 for the outdoor marriage party of my daughter. So far they work quite well (powered by a Proamp 3000). However, I'm always eager to satisfy my affinity for new designs. From what I've read in this thread - thanks so much to all contributors, especially but not limited to Ricci - the design works pretty well. Hence, I'm interested to build 1 SKRAM to compare it with my existing design. Would it be possible to shrink the cross-section area of the enclose to reflect the smaller footage of the 18NLW9601 compared to the 21NLW9601? E.g. reduce the width of the enclose? Gr Peter Quote Link to comment Share on other sites More sharing options...
Sushi Posted March 22 Report Share Posted March 22 Not a great fan of downsizing designs to fit different size drivers, i honestly have to say.. but anyway, if you really need to do it, i would rather change the volume of the enclosure by reducing the height (giving up the air in the top part in particular) and i tell you briefly why: reducing cab width would mean to change reflex width, therefore altering cab's tuning and low end performance. No point in building this specific cab at that point, it would sound quite different from what others have studied, designed, and tested. Same thing if we talk about cab depth/ port length. In any case, remember this cab have been designed to hold inside a 21' woofer and tuned to the low freq IT would reproduce, so a 18' would probably have slightly less low end extension and other differences in parameters that you need to consider if your aim is to get as near as possible to the actual Skram's performance. Quote Link to comment Share on other sites More sharing options...
Sushi Posted March 22 Report Share Posted March 22 On 3/14/2024 at 9:53 PM, Jami said: 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 👏👏👏👏👏 Great job! This will defo come handy when i will finally get to build my first pair.. hope i'll make it this summer. Quote Link to comment Share on other sites More sharing options...
rolo95 Posted March 22 Report Share Posted March 22 On 3/21/2024 at 4:56 AM, nightingale said: Hence, I'm interested to build 1 SKRAM to compare it with my existing design. Would it be possible to shrink the cross-section area of the enclose to reflect the smaller footage of the 18NLW9601 compared to the 21NLW9601? E.g. reduce the width of the enclose? Gr Peter Changing dimensions to an existing design is a big no, what you can do however is to build the cabinet as it is and add an extension reducer ring so you can mount your 18" driver in to the 21" baffle, that way later on you can swap the 18" for the correct driver. i wish Ricci published the HR screen of this design, that way you can sim different drivers in it. but i think there is no much leeway as this cabinet need a very strong motor driver with military specs cone so there are not many 21"s that fit the bill, and the ones that fit are already listed on post#1 My 2 cents. Quote Link to comment Share on other sites More sharing options...
rolo95 Posted March 22 Report Share Posted March 22 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 1 Quote Link to comment Share on other sites More sharing options...
rolo95 Posted March 22 Report Share Posted March 22 ok, there are other drivers that maybe FIT on the SKRAM is the HR screen for the SKRAM available ? if not i guess we need to wait till Ricci chime in to see if they fit BEYMA 21LEX1600ND , RCF LF21X451 , LaVoce SAN215.30 , 18Sound 21LW1400 Quote Link to comment Share on other sites More sharing options...
nightingale Posted March 23 Report Share Posted March 23 For the Othorn design Ricci mentioned that both, the 21NLW9601 and the 18NLW9601 would fit, although the design was also made for 21" chassis. I guess I'll wait if Ricci is jumping on my post. Quote Link to comment Share on other sites More sharing options...
klipsch Posted March 23 Report Share Posted March 23 Pretty sure 18" options were talked about for skrams and skhorns at some point - might even be in this thread. Design stays the same, but you sacrifice output based on the lesser driver. Quote Link to comment Share on other sites More sharing options...
Fraser Alexander Posted April 5 Report Share Posted April 5 Hi @Ricci I'm glad I stumbled upon this amazing design - thank you! I'm very very new to this world, so apologies for the basic question. I'm just wondering if you had links to certain screws you'd recommend for both the enclosure and fixing the driver to the BB? I saw you specified the type of screw for the driver, but I'd love to see images of all the screws to make sure I'm picking the right ones. Cheers! Quote Link to comment Share on other sites More sharing options...
klipsch Posted April 5 Report Share Posted April 5 If using screws VS inserts for bolts, spax construction screws work great - highly available in the big box stores if in the States. Quote Link to comment Share on other sites More sharing options...
andyman3k Posted April 9 Report Share Posted April 9 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 5 2 Quote Link to comment Share on other sites More sharing options...
Ricci Posted April 11 Author Report Share Posted April 11 Hello Andyman3k. Nice work and thanks for the measurements. QSC eh? I've used my share of QSC amps and speakers over the years. The impedance plot suggests that the tuning of the vents is near 30hz or so. That's right about where it should be. The corner drooping a little is probably due to the 8 ohm 21sw152 having a little lower motor force than some of the other drivers used. That's one effect is that the vents aren't loaded as aggressively which results in a little bit of a roll off before the tuning. Not the end of the world in the scheme of things. In general you'll get a sharper more aggressive low corner with drivers having more motor force ( BL^2/Re) / lower qts. My cabs are usually a bit undersized vs extension and thus require extra energetic drivers. That indoor measurement rig sounds intriguing. Too bad it's not for public consumption. Am I correct that the polar work was conducted outside but the FR and Imp were on the inside rig? Nice measurement rig. Again thanks for sharing your info. More data is always welcome. 1 Quote Link to comment Share on other sites More sharing options...
Ricci Posted April 11 Author Report Share Posted April 11 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. 2 Quote Link to comment Share on other sites More sharing options...
Father Francis Posted 21 hours ago Report Share Posted 21 hours ago Question for anyone running four plus skrams, last weekend we were running 4 cabs standing strapped together with 2*215 , and a pair of F1 res3 sh , anyway after the gig the two cabs in the middle were pretty hot, the cabinets plywood like very warm , cabs are loaded with B&C Sw 152 8ohm running all four off a K20 Quote Link to comment Share on other sites More sharing options...
peniku8 Posted 11 hours ago Report Share Posted 11 hours ago 9 hours ago, Father Francis said: Question for anyone running four plus skrams, last weekend we were running 4 cabs standing strapped together with 2*215 , and a pair of F1 res3 sh , anyway after the gig the two cabs in the middle were pretty hot, the cabinets plywood like very warm , cabs are loaded with B&C Sw 152 8ohm running all four off a K20 Are they painted black and some strong lights were pointed at them? Quote Link to comment Share on other sites More sharing options...
jay michael Posted 6 hours ago Report Share Posted 6 hours ago 15 hours ago, Father Francis said: Question for anyone running four plus skrams, last weekend we were running 4 cabs standing strapped together with 2*215 , and a pair of F1 res3 sh , anyway after the gig the two cabs in the middle were pretty hot, the cabinets plywood like very warm , cabs are loaded with B&C Sw 152 8ohm running all four off a K20 Hey Father Francis. Heat happens for sure, on gruelling bass music shows I can feel the heat on the metal of the hatch handles, and if you put your hands in the vents you can feel the warmth coming off the drivers. I've rolled mine out to the trailer in cold Canadian winter nights and seen heat causing a bit of fog to come out the vents haha. There was some mention in previous pages regarding the potential for heat to be a problem for this cabinet. While you should be careful with your limiters, in real life I don't think its turned out to be as big of a concern as was warned against. I've been using a pair of thermocouplers to pull temperature data off the magnet, if I'm working them hard I can get temps up close to 70-80 degrees or so when I'm tickling my limiters during heavy bass music shows. Bennett Prescott from B&C stated that the 21sw152 should survive 100 degree magnet temps reliably, but I've made it a point not to run them that hot. I only really see that high of temps for dubstep or modern bass music shows, for most everything else temps never seem to build up when I push them to the verge of limiting. I've actually found this a bit interesting, as it was stated earlier in this thread that one should avoid pounding techno with this cabinet but that hasn't been my experience at all. I specifically use this guide to set my limiters and I haven't burnt one up yet, its written by XTA but can be applied to any amplifier. Start at page 5 and follow the instructions closely. https://www.xta.co.uk/wp-content/uploads/2018/05/XTA-Application-Note-DPA-Amps-Limiter-Settings.doc.pdf 1 Quote Link to comment Share on other sites More sharing options...
Father Francis Posted 2 hours ago Report Share Posted 2 hours ago 8 hours ago, peniku8 said: Are they painted black and some strong lights were pointed at them? Yes they are painted black, they gained 3db’s and no strong lighting around 3db is a joke Quote Link to comment Share on other sites More sharing options...
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