No, it would be minus 7.5 mm since the simple formula for short gap under hung designs is (VC wind height - gap height)/2, but with longer gaps it's not so simple. It's my understanding that > ~16 mm gap heights must be measured to find either its 10% distortion or a 30% drop in drive force point depending on whether you prefer the traditional or DUMAX way.
GM
GM
Based on the averaged measurements of hundreds of actual Fe126e drivers posted upthread, I've performed some surgery on my BIBs to bring them into line with what the BIB spreadsheet says for a driver with these revised parameters. (Fs = 94, Vs = 6.26, Qt = 0.4) (ish, can't remember exactly)
They end up being quite small, with a line length of 75, Zd of 16 and Sm of 65. I converted my existing BIBs by chopping off 4 inches of the peak, and cutting the mouth down about a foot from the former top, at an angle to achieve the necessary Sm.
I put a very little stuffing in the peak, and a very little at the fold.
I have to say, I like them a lot better. There is less bass in absolute terms, but the sound is now balanced and smooth, and the driver seems to be "happier" in its new home. Before I was adding and removing stuffing to try and cure boominess or stuffiness, and I could not deal with that shout. They are now very "fast". "Hey Joe" just came on and caught me by surprise with that opening lick.
I'll post some pictures - the surgery gave them a pretty neat shape.
They end up being quite small, with a line length of 75, Zd of 16 and Sm of 65. I converted my existing BIBs by chopping off 4 inches of the peak, and cutting the mouth down about a foot from the former top, at an angle to achieve the necessary Sm.
I put a very little stuffing in the peak, and a very little at the fold.
I have to say, I like them a lot better. There is less bass in absolute terms, but the sound is now balanced and smooth, and the driver seems to be "happier" in its new home. Before I was adding and removing stuffing to try and cure boominess or stuffiness, and I could not deal with that shout. They are now very "fast". "Hey Joe" just came on and caught me by surprise with that opening lick.
I'll post some pictures - the surgery gave them a pretty neat shape.
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