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Agreed. We essentially just got a flash and low boom/rumble. Not the ST warp-boom blastwave I was expecting. One of the best movies I have seen. JSS

I voted 3 stars. This was primarily a slow burning dialog driven movie as expected. I wanted LFE effects to end all LFE effects when the bomb was finally detonated. It didn't quite deliver that to say the least. Good movie though.

Hello Lex, I'm glad that you like the design and that the front plate appears to be solid enough. The modeling for it only ever indicated a modest amount of gain in the kick and upper bass region. Does look cool and provide driver protection as a bonus. Unfortunately a 21" cabinet can only be so small / light. Physics grrrrrrr. Did you happen to weigh the finished product with the driver installed? It looks like you measured the weight as about 52 kg without the driver. 70kg with the driver? This should be about right. A little big and heavy for a one man lift. You could add wheels or a dolly system. The 18" design you are thinking of is probably what I tested the BMS 18N862 in. It is much smaller and lighter but that cab is tuned a little lower and was intended for a heavy duty bass guitar rig using AE TD18H+ Apollo's. Traditional BR designs aren't that difficult. You could probably design your own. What country are you in? The bike systems seem interesting and fun. This would be a lot of sub on a bike!

I may have to check this one out. BTW - I got most of the links fixed from the first post. Still need to fix the 3-3.75 star films' links, will hopefully get to it soon. If anyone notices a missing graph on a post, let me know. We lost all of bosso's scenecaps at some point, unfortunately. If anyone has any film requests for measurement, let me know. JSS

Picked up this Bluray for cheap and really enjoyed this film! Same writer as The Quake and The Wave. You aren't kidding, massive bass in this one. Definitely worth a buy on disc, especially while it's so cheap.

Hello Josh, 8 ohm 21sw152 is the driver that i used, driven by a Powersoft Digam amplifier. The front plate looks cool and as far as i can see raises the plot a little between 40 and 50 Hz. The plip around 150Hz is no problem for me as i am testing the sub currently underneath Art Welters Syntripp's. These are crossed at 80 Hz to minimize sense of direction in the sub (not sure this is the right word but at this moment its difficult to locate the sub by ears alone). The Syntrips Themselves have a way of dissapearing (diffucult to locate blind) audibly if that makes sense. I am very pleased with the result i have tortured it quite little with some sub tests and there is no noises from the cabinet other then a poorly sealed speakon socket (very minimal). Building it, i made sure the front plate is not touching the cabinet on the sides. I still have to play loud music over it but sofar to my ears CKRAM has a very clean and accurate sound, revealing a lot of information in the lowest frequencys. Deepeer modern house tracks are truly a joy, but also recent music for instance billy eilish and for instance beonce. Even at higher levels (sofar) it doesnt sound boosted like with some commercial BR designs i find. The only minus is personal. I hoped it would be more portable. You cant have everything and to have impressive volume down to 30Hz obviously comes at a cost. For this setup to be a solo operation is not as easy as i hoped. its just a little to much weight x size, to comfortably load alone. That being said it matches the Syntrips very well i think. As in some occasions i am looking to transport the sub by bicycle, i am considering building another smaller sub cabinet. I saw a design allegedly by you😀, wich would match my project. single 18" BR with a square port in one of the corners of the front plate. I cant find it at the moment (Diy audio forum rabbit hole syndrome). Does this sound familliar at all? Thx again for the great drawings and calculations wich i am sure have costed a lot of attention. If there is anything that you or anybody else want me to measure or test please let me know. Currently i am using a focusrite Dac and Umic measuring mic. combined with REW. Lex,

I'm much in the same boat MM. Behind on movies. I've been watching mostly docu series and sports lately. I did watch Godzilla Kong and Minus One, both in the theater. There was plenty of bass for sure but whether either truly dug deep or not I can't tell at the local Plex.

Excellent job Lex. The cab looks solid and well built. Nice pictures of the process too. What driver are you using? The 4 ohm or 8 ohm 21sw152? Give me a day or two and I'll go through the measurements and formulate a reply. Apologies for the extra extra late reply. I've been on hiatus from audio for quite a spell. Overall the measurements look about as expected with the vent pipe resonance causing the blip at about 150Hz. Looks like the tuning may have come in a smidge lower than the target, but that isn't unexpected given the size of the vents and the cramped space inside of the cab. Any thoughts on the sound and structural solidity of the cab? The driver cap plate? Are there issues with vibration or noise from it during loud playback? That's been a concern since day one of the design. Secondarily I'm not sure if the acoustic effects of it are worthwhile. At least it's a glorified driver grille if nothing else.

I should have Dune pt1 measured next week. JSS

Hey Ricci! I have not really been watching films as often as I used to the last few years, partly in fact because I have yet to rebuild the HT since I moved. I have a decently capable temporary HT outfitted with crowson transducers so I can monitor the Infrasonics, and the plan is to be reviewing a few films every month. If anyone has any suggestions for movies of the last few years that you would like evaluated, post the requests in this thread, I'll try to get everything updated so the thread works as it used to. Also now that Mandalorian is out on BluRay, I may get around to measuring it, as some of the episodes sounded like they may have had some great sound design. JSS

I'll have to give this a watch John. Haven't seen it yet.

I'm really out of the loop on the latest bass movies. Have there been many solid 4 to 5 star films in the last couple of years? Most everything seems to be lacking in the really deep stuff lately.

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.

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.

4 Star films now have correct links, and Transformers - Rise of the Beasts is up for voting. JSS

Let us know what you think of the bass in Transformers - Rise of the Beasts

Thanks! I have updated all of the 4.25 star rated films links in the first post. JSS

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

If using screws VS inserts for bolts, spax construction screws work great - highly available in the big box stores if in the States.

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!

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

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.

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.

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

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