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In Reply to: RE: Replacing capacitors in 2.7 QR posted by pictureguy on June 10, 2015 at 10:34:38
You should be able to compensate for the drop in R with a different L calculated to compensate to keep the same XO pole but the small difference in overall DC resistance will up the lower freq output slightly and that would not be a bad thing for most maggies, perhaps an improvement for many tastes.
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Pictureguy - thanks for the advice. But I'm afraid this indicates that I'm just out of my depth. I thought I could just replace stock parts with BETTER parts of the same specification. But this sounds like there's more to it than that.
Bummer. I might not have the know-how to pull this off...
You can choose commercially available values for the inductor to come close to what you need with the bigger gauge and lower DC R.
Find the commercial inductor of the original value in the new heavier gauge and take its R spec as Rnew_inductor
A sufficient approximation can be had with R1 = Roriginal_inductor + Rdriver
and R2 = Rnew_inductor + Rdriver
You want to preserve f_c = R / (2PiL) so R1/L1=R2/L2
Solve for L2 and use that value to find a close .inductor (or combo of two inductors to place in series) among standard values.
Recalculate L2 with the actual Rnew_inductor to make sure you are close enough with your selection.
This is an approximation, for precise specs you should run it on Spice but it is not likely to give a significant enough difference to end in you buying a different standard value inductor.
The difference should be around 10% and the increase in low freq output relative to before should be about 0.8db which is subtle but audible. Definitely nothing you would want to fix if you thought the speaker could use some more bass or warmth.
I used a different technique based on my goal.
Using an online calculator and only standard PVC dimensions for the core, I did several itterations until I saw which way the numbers evolved.
I than zero'd in on my goal which was to duplicate within 5% the DCR of the issued inductor using heavier wire than stock and having the same number of turns per layer as layers.
My best effort used about 150feet of #14 and had 14 turns per layer and 14 layers.
The core was 2.22" PVC which is the outside diameter of SOMETHING PVC. DCR was 0.37ohms and just outside my goal. But not THAT far.
This does the following: Doesn't mess with any frequencies. Maintains balance of drivers. Increases power handling. NO chance of saturation limiting.
Too much is never enough
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