peniku8 Posted November 24, 2023 Report Share Posted November 24, 2023 1 hour ago, Lex breijs said: 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. 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! 1 Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted November 25, 2023 Report Share Posted November 25, 2023 Thanks Ill post more pics once i i get to it, and will upload measurements once im finished! Regards Lex 1 Quote Link to comment Share on other sites More sharing options...
klipsch Posted November 25, 2023 Report Share Posted November 25, 2023 Awesome! Well done. Looking forward to the results. Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted December 19, 2023 Report Share Posted December 19, 2023 small update, Added much needed grips and a couple simple corners. Also connected the speakon input using 6mm2 wires. Was gonna do some initial testing first and then complete the design with the front disk. Does anyone have some recommendations for setting the DBX drive rack im using? low cut off frequency aswel as top cut off point. As an amp i have the Powersoft Digam 7000. thanx in advance Quote Link to comment Share on other sites More sharing options...
klipsch Posted December 20, 2023 Report Share Posted December 20, 2023 20 hours ago, Lex breijs said: small update, Added much needed grips and a couple simple corners. Also connected the speakon input using 6mm2 wires. Was gonna do some initial testing first and then complete the design with the front disk. Does anyone have some recommendations for setting the DBX drive rack im using? low cut off frequency aswel as top cut off point. As an amp i have the Powersoft Digam 7000. thanx in advance With all of the vents open, maybe start off with a 24db BW at 30hz and 110hz respectively? A sharper slope could be used on the low end if really pushing the cab/driver. On the higher end, it really depends on your mains. Quote Link to comment Share on other sites More sharing options...
peniku8 Posted December 20, 2023 Report Share Posted December 20, 2023 13 minutes ago, klipsch said: With all of the vents open, maybe start off with a 24db BW at 30hz and 110hz respectively? A sharper slope could be used on the low end if really pushing the cab/driver. On the higher end, it really depends on your mains. I typically like to grab the HR sim and use the filter wizard so that the maximum excursion below tuning doesn't exceed the maximum excursion above it. With a 4th order Butterworth that typically lands a few Hz below the tuning point, which is around the same point as you suggest, for this cab's native tuning of 30Hz. Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted December 20, 2023 Report Share Posted December 20, 2023 Hi, Did initial measurements today to see if i have everything in place. the sweep is set 10hz to 150hz. The dsp was set 20hz to 500hz lower slope was BW12, hadnt seen youre suggestions yet. I live in a crowded place close to airport and highway. The measurement is too close to a building+-5 meter and my neighbours camper. Before the sweeps i tried some youtube bass tests on different frequencys searching for rattles but it is sofar very quiet. I may continue (weather allowing) tomorrow and set the DSP to your suggested settings. I used a firefly as a DAC and UMIK1 as microphone. Software is REW. Im very much open to interpretations and adjustment suggestions for the next measurements. greetings Lex Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted December 20, 2023 Report Share Posted December 20, 2023 heres the REW file can someone please explain what the "phase line" (dotted red) is for and what it tells us in this case? ckram Dec 20 op hout.mdat Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted December 27, 2023 Report Share Posted December 27, 2023 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 2 Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted December 30, 2023 Report Share Posted December 30, 2023 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 1 Quote Link to comment Share on other sites More sharing options...
Ricci Posted April 11 Author Report Share Posted April 11 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. Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted April 12 Report Share Posted April 12 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, Quote Link to comment Share on other sites More sharing options...
Ricci Posted April 13 Author Report Share Posted April 13 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! Quote Link to comment Share on other sites More sharing options...
Lex breijs Posted Friday at 08:54 AM Report Share Posted Friday at 08:54 AM Hello Josh, If i recall correctly the weighing was done with the driver installed. So afterall really not bad. I live in the Netherlands. Bike systems are more and more popular here, some people just prefer openair dancing i guess. Also its easy to move when authoritys disagree. Ill probably make the ckram into a bike cart and will upload pics of it. Unrelated question, do you know if anyone ever posted measurements of the gjallard horn #2 its very intreguing. Im considering building it aswell the ckram has gotten me appreciative of that low end information. Can you tell me how it would compare to the ckram? Quote Link to comment Share on other sites More sharing options...
Ricci Posted 20 hours ago Author Report Share Posted 20 hours ago The Gjallarhorn 2 was never built that I recall. It was designed around a very expensive and hard to find driver with parameters that were rare back then. It would've marginally improved the original GH performance and improved the cabinet bracing and solidity. I liked the horn fold I used on that one. It would've still had the response issues inherent to TH designs tuned so low. Ragged FR in the top of it's range and potential ringing. Also the performance would greatly vary based on the driver. It is a very large, heavy cabinet. However...Over a 1.5 to 2 octave range it is very potent and smooth. I'm not sure what current driver options would work well for it. Quote Link to comment Share on other sites More sharing options...
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