Lowpala Posted May 2, 2016 Report Posted May 2, 2016 I am in the process of laying out the dimensions on a T line for a JL 12W7. Everything was good until trying to come to an accurate conclusion of the SD. JL claims the SD to be; 84in2 When I measure it myself I am getting 9 in from inner surround edge to edge. Using that, 4.5 x 4.5 x 3.14 is; 63.5 in So what gives? This is a huge difference in what the port area would be, what do I do? I would think to go from my personal measurements unless I am missing something. Help please!
Joe X Posted May 2, 2016 Report Posted May 2, 2016 Include 1/3 to half of the surround to your radius calculation and see if it gets closer.
Lowpala Posted May 2, 2016 Author Report Posted May 2, 2016 About to the middle of the surround is 10.5" end up with 86in2. So that is the proper way to measure SD?
Joe X Posted May 2, 2016 Report Posted May 2, 2016 No, what I said is just closer to the true number which is harder to measure and is usually done in a lab, I think you can just trust JL on this one.
Triticum Agricolam Posted May 2, 2016 Report Posted May 2, 2016 Like Joe X said, the standard way to measure Sd is to include 1/2 a 1/3 is the surround. Keep in mind that if you set the line area equal to Sd you will probably get a fairly significant peak in output around tuning. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds:
Lowpala Posted May 2, 2016 Author Report Posted May 2, 2016 I am hoping to have a low end monster. W7 FS is 27.2 hz, that will be my tuning frequency. I have read to go slightly smaller for the line area than the SD, I haven't found an exact suggestion but was thinking around 10% less. Thanks for the answers regarding the SD.
kirill007 Posted May 2, 2016 Report Posted May 2, 2016 its also a dish not a flat plain. That has no effect whatsoever on cone area. Thinking is the root of all problems... You ALWAYS get what you pay for.
Lowpala Posted May 2, 2016 Author Report Posted May 2, 2016 its also a dish not a flat plain. That has no effect whatsoever on cone area. I actually did measure the "dish" thinking the same thing lol but the results were very similar.
Lowpala Posted May 2, 2016 Author Report Posted May 2, 2016 I thought I had the design set and ready to go so I could start the build log and get to jammin. But ive been reading pretty much for the last 12 hours straight on tline theory and have thoroughly confused myself. I was going to tune to the Fs because it is <30 with line length being 10.38ft. With it being a large U shape to take out any of the sharp corners/bends. My truck (single cab) is already cut for the blow through @ 16"h x 48"w, so I have got the room to do pretty much whatever here (8ft bed). But like I said, the more I read the more I don't want to do it just because I feel like its going to turn out sounding less than excellent. Sd; 84" Vas; 2.33ft3/66L Fs; 27.2Hz Could you guys steer me in the right direction here? Otherwise I've came up with a 4.5Ft3 @ 29Hz that modeled really nice.
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