Stephen300 Posted July 30, 2019 Share Posted July 30, 2019 After reading about the Ripole design I've decided that I would like to give it a try for myself. I would like to use the same design that I have seen by Jazzman but I would like to make one modification. I want to get away from the magnet sticking out the side of the enclosure so I'm thinking of using a shallow mount subwoofer. Specifically the Infinity Reference REF1200S. Would you agree that this seems to be a good replacement driver for this project? The following are the specs of the 1200S with the matching specs for the SLS 12 used in Jazzman's design in parenthesis. Fs - 23Hz (31Hz), Qts - 0.54 (0.54), Sens.- 92dB (89dB), Sd - 78 square inches (82 square inches), Xmax - 7.63mm (8.3mm) The part I don't get is the math explained by Jazzman in his project notes. According to him the area of the front chamber's opening should be 1/3 of Sd if Xmax is greater than 10mm and 1/4 of Sd if less than 10mm. The rear chamber should have an area of 1/2 Sd to 1 Sd With the Sd of the SLS 12 being 81 square inches with an Xmax of less than 10mm it should have a front chamber opening area of (81 x .25) 20.25 square inches. The rear chamber opening area should be (81 x 1) 81 square inches. According to the dimensions given for his enclosure the front chamber has an actual opening area of (3.625" x 14.125") 51 square inches and the rear chamber has an actual opening area of (3.3125" x 14.125") 46.8 square inches. Unless I've made an error in my math and am missing it something just doesn't jibe here. Your thoughts? Link to comment Share on other sites More sharing options...
robmid Posted July 31, 2019 Share Posted July 31, 2019 I had the same problem using calculations from different sources so I ended up measuring the photographs and scaling up from there. I think I was close enough to be within specifications. I abandoned the project in the end because it seems the driver model and figures are critical and I really wanted to audition one before committing myself to new drivers. Link to comment Share on other sites More sharing options...
Nada Posted July 31, 2019 Share Posted July 31, 2019 16 hours ago, Stephen300 said: Your thoughts? Why dont you PM Jazzman directly about your math queries? He's super helpful and uses this forum. The usual Ripole design with the magnets sticking out will allow nice air cooling. With your plan to use shallow mount drivers and box them in will you need an air gap behind the magnet for convection cooling? Is there room? Construction wise there might be a case for using threaded rod and nuts to tie the side walls and drivers directly together. Link to comment Share on other sites More sharing options...
Stephen300 Posted July 31, 2019 Author Share Posted July 31, 2019 (edited) I think I figured out what’s going on with the area of the center chamber. Since there are two drivers firing into the center chamber I doubled the amount of piston area to do the math. So the combined Sd for the two drivers becomes 162 sq. in. (81 x 2) That times .33 comes to 53.5 sq. in. This places the amount of area needed for the center chamber in the neighborhood of the chamber’s measured area of 51.2 sq. in. (3.625” x 14.125”). For the outer chambers the measured area is 46.8 sq. in. (3.3125” x 14.125”). So the specified Sd of 81 x .5 comes to 40.5 sq. in. Tweak the math a little to 81 x .57 and you get 46.2 sq. in. Since the multiplier for the outer chambers can be from .5 to 1 this makes the math for the outer chambers work. Since the magnets are not vented and the chambers are not sealed I don’t think there’s any need to be concerned about magnet cooling. The open chambers and the amount of air being moved by the subs should provide plenty of cooling. I’ll try contacting JM. Since the posts regarding his build were so old I figured I’d post this for starters and if he’s still around maybe he would chime in if/when he saw my post. Edited July 31, 2019 by Stephen300 Link to comment Share on other sites More sharing options...
jklow888 Posted August 3, 2019 Share Posted August 3, 2019 You could also try the former Yahoo Groups for OB which is now moved to https://www.facebook.com/groups/212651322618383/ where some members have discussed/built ripoles. Link to comment Share on other sites More sharing options...
Stephen300 Posted August 3, 2019 Author Share Posted August 3, 2019 (edited) Thanks! I'll give it a look. Edit: Too bad I don't fool with FB Edited August 3, 2019 by Stephen300 Link to comment Share on other sites More sharing options...
davewantsmoore Posted August 12, 2019 Share Posted August 12, 2019 (edited) On 31/07/2019 at 1:42 AM, Stephen300 said: but I would like to make one modification. I want to get away from the magnet sticking out the side of the enclosure so I'm thinking of using a shallow mount subwoofer. My strong advice is .... Find a well documented design, and build it exactly. If you want to do anything else.... then you will need to become proficient in designing dipoles. If I said you would need to design, build and measure .... more than 5 boxes to even get started, I wouldn't be being flippant. (They are difficult to model well .... so there's more "build and find out" involved than other simpler boxes) ... but if you want to go down that path, then Edited August 12, 2019 by davewantsmoore Link to comment Share on other sites More sharing options...
davewantsmoore Posted August 12, 2019 Share Posted August 12, 2019 On 31/07/2019 at 1:42 AM, Stephen300 said: AFs - 23Hz (31Hz) Sensitivity is half an octave lower. That's not insignificant.... it might work ok though. Build it and see. The pertinent question is: "How will you know?" Link to comment Share on other sites More sharing options...
Stephen300 Posted August 26, 2019 Author Share Posted August 26, 2019 In case anyone was wondering the sub turned out GREAT! The Infinity REF1200S subs sound fantastic and blend extremely well with my Magnepans. 2 Link to comment Share on other sites More sharing options...
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