peniku8 Posted April 6, 2020 Author Report Share Posted April 6, 2020 Got an impedance sweep outside today. And gave them some music. They have lots of headroom for a cab this size for sure. Quote Link to comment Share on other sites More sharing options...
kipman725 Posted March 25, 2021 Report Share Posted March 25, 2021 I liked this port so much I'm basically copying it for my 12TBX100 sub. The height wasn't listed so I guessed it as 44mm from the pictures (3*18mm boards with 10mm of rebate). Tuning came out at 38Hz. How close did I get? I'm also guessing from how your Hornresp response compares to mine that you used complex inductance parameters? Quote Link to comment Share on other sites More sharing options...
kipman725 Posted March 25, 2021 Report Share Posted March 25, 2021 ah ok I have only used 1/2 of the port here so I guess the height is less than I expected? Quote Link to comment Share on other sites More sharing options...
peniku8 Posted March 26, 2021 Author Report Share Posted March 26, 2021 I did use complex Le and my vent area are more than yours, even if you double the numbers to combine the two ports. I will PM you my HR inputs, but I usually manipulate the inputs there in a way to get results closer to real-world expectations. My thoughts on the design after a while: -I've used them at a few weddings and the performance was great. I have a sub-octaver on the cajon, which adds a nice 40-45Hz low end to the kick drum, which would be hardly achievable with run off the mill 12" PA designs tuned to 55Hz and what not. -They can take a lot of power and I've never noticed port noise, but theres some early compression creeping in, which is just natural for a design this size -The expansion of the port towards the outside is too much I think. It might cause separation (and turbulence) there, which could be remedied by an extra element to guide the air, but I'd maybe just make the expansion less logarithmic... I'm learning a bit from a youtube channel called Kyle Engineers, which is an ex-mercedes F1 engineer -A bigger port gives you more performance of course, but the goal here was space-efficiency obviously, and it needed to be a one man setup which won't break my back. The design is lacking a bit of punch compared to my 21ds115 cabs, but I guess that's only natural since those are front loaded and.. well 21" Quote Link to comment Share on other sites More sharing options...
kipman725 Posted March 26, 2021 Report Share Posted March 26, 2021 Thanks for the info! I had already designed a sub with just pipe ports to try and get something built quickly, however I needed to redesign it as my model would break on changing the material thickness parameter and it was overweight for the application (ultra portable human carried ~5km) resulting in a change from 18mm to 12mm (yes I know 12tbx100 is heavy, but I got them cheaply and this is the easiest thing to change). But then I realized how much output at tune I was potentially giving up (JBL HLA port design information indicates around 9dB at tune). In the future I would be interested in a even more port optimization but its a bit outside my area of expertise as I'm an electronic engineer and my only physics is in electromagnetics. From the off the shelf options ( https://www.l-acoustics.com/en/product/ks28/# ) it looks like your on the right track. If you wanted to try lots of port designs the best approach for testing would be to have a box that allowed attaching ports to the outside so that each test only required building the port and not a whole box. Size is very constrained for these subs as they have to go on someones back and also fit under my desk at home. Quote Link to comment Share on other sites More sharing options...
kipman725 Posted June 2, 2021 Report Share Posted June 2, 2021 https://www.comsol.com/paper/download/679311/bezzola_paper.pdf might be of interest for a 'fully optimized' design Quote Link to comment Share on other sites More sharing options...
peniku8 Posted June 3, 2021 Author Report Share Posted June 3, 2021 Thanks for the paper, I've been looking for some more info the topic! If you had access to a flow sim software, you could probably get some decent info out of that, even if it works with (non compressible) liquids. Quote Link to comment Share on other sites More sharing options...
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