Altec 515 on field-coil sens higher then 110

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GM

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Joined 2003
News to me, though going from very dim memory, the only T/S specs I've seen calculates a near 107 dB/m max mid band efficiency for a real one, which is near the limit of a single 15" compression expo horn. Doesn't get much better than this!

Its breakup mods BW can be up to +6 dB based on mine and some others 515Bs, so a dual driver expo or hyperbolic horn could in theory top out at ~114 dB/m, but more likely were adjusted to be somewhat lower, so probably not much greater than an AlNiCo 515.

Regardless, maybe this is the one: Field Coil conversion for JBL, Altec, and Western

Then again, totally forgot about this 515 FC, which calculates right at 96 dB, a bit lower than my AlNiCos, though not maxed out: Field Coil 515 enclosure suggestion

Maybe some more useful info than just these first two: altec 515 field coil conversions - Google Search

Bottom line, I'd like to see a bone fide mid band 110 dB/2.83V/m conversion as I don't see how they can top an original by that much unless measuring its breakup modes.

GM
 
A field-coil magnet structure could potentially provide more flux density than the 515's permanent magnet, which may result in perhaps a dB or 2 more sensitivity, but to achieve 110 dB 1/w/1/meter in half space down to Fs would require (large) horn loading.
 
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Maximum SPL for alone 515 FC is possible a only - 107 dB/W, this correct, yes? Without big horn or TL enclosures sure.
Maybe my memory really brings me down, or I pulled the number out of context, I remember my surprise (110 - just wow) - that's why I remembered.
 
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