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In Reply to: Supravox 2 way OBs: Please comment on this idea (Duke: please don't laugh at me!) posted by xcortes on February 9, 2007 at 08:21:53:
what Fs are your woofers @ 8 volts?
You are daring to be great with a Qts of 5 ...... :)
Follow Ups:
nt
here ya go ..... Fs 23Hz, Qt 5, 45cm baffle
?
I don't know anything about the field coil drivers
(the graph is relative only)
but as Q goes down you loose the bump @ 23 Hz and
a little extension as the bump tries to pull
the response near it up.......
still -3db @ the same point....
when "we" add a series resistor to a permanent magnet speaker, qes goes up, efficiency goes down and theres a frequency dependent voltage divider effect with least impact at driver's fs as that's the highest Z point. With a field coil, qes goes up, efficiency down but negligible divider involved (assuming low Z solid-state amp) -?not too long ago (like Wizard of Oz time :^), field coil were more plentiful than permanent magnet type. Field-coil woofer should be no more expensive to produce than permanent - if there were high demand and market. Some years back Angela Instruments had clone of f-c Jensen for ~$140 and those may have been built by Eminence (?)
what's the art of making practical large field-coil coaxial? - that seems tougher to visualize
Yea. They used to use the magnet coil as also the filter choke for the power supply on some radios.....
nt
with a permanent magnet woofer , as Qes is raised via series resistor (or amplifier with high output impedance) the speaker's midband efficiency will fall.for example here's Hawthorn's Silver Iris on a 2'x3' baffle outdoors driven by a solid state amp and I added 4ohms series resistance raising qts to about 1.66 vs a nominal 1 or so
Green = On Axis no resistor; Violet = on-axis adding series 4 ohms resistor
Cool chart. I'll download the program. Is the chart the anechoic response? If so the room should help a lot.
Yea no room gain. 1/2 space ? I think.
You can use any sealed box program with the ability
to add a first order high pass filter:
Set alpha to ~ 0 (infinite baffle)
Set HP (Hz) to (in feet) 360/shortest baffle diameter
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