The 2.5 clone papers - CCRMA

100.0
dBSPL
MLS - Frequency Response 15-02-03 21.44.47
90.0 108.0
80.0 36.0
70.0 -36.0
60.0 -108.0
50.0 -180.0
300 1k 10k Hz 20k
CH A dBSPL 1/3 Octave 51.2kHz 16K Rectangular Start 2.81ms Stop 5.45ms FreqLO 379.26Hz
blue=left speaker red=right speaker sensitivity 2.83Vrms
Fig.45. Freq. Response left and right speaker.
Sensitivity at 1 meter, 2.83 Vrms, ~ 83 dB.
For comparison here are fresh Rogers LS3/5a (11
ohm version) frequency response curves, with and
without front grille. A legendary loudspeaker with
phase problems in the crossover region that today
would make any home constructor ashamed of
himself. I keep these shoeboxes to remind myself of
not overemphasizing any single parameter in
loudspeaker construction because they sound so
good.
100.0
dBSPL
CLIO
MLS - Frequency Response 15-02-03 21.31.53
90.0 108.0
80.0 36.0
70.0 -36.0
60.0 -108.0
50.0 -180.0
300 1k 10k Hz 20k
CH A dBSPL 1/3 Octave 51.2kHz 16K Rectangular Start 2.87ms Stop 5.53ms FreqLO 376.47Hz
LS35A red:+front blue:-front
Fig.46. Rogers LS3/5a, 11 ohm version, 1989.
100.0
dBSPL
CLIO
MLS - Frequency Response 15-02-03 21.51.31
90.0 1.000
80.0 0.600
70.0 0.200
60.0 -0.200
50.0 -0.600
300 1k 10k Hz 20k
CH A dBSPL 1/3 Octave 51.2kHz 16K Rectangular Start 2.81ms Stop 5.66ms FreqLO 350.68Hz
red=0 blue=10 green=20 purple=30
Fig. 47. CO v3 horizontal response,
0(red),10(blue),20(green)30 o (purple)
CLIO
180.0
Deg
180.0
Deg
1.400
ms
21
Well, whether you choose v2 or v3 crossover you
will get a great speaker in any case.
Be sure to use the right component values in either
case. The most important components are the
capacitor in the LP section, 7.4 uF for v2 and 6.8 uF
for V3, the coil in the HP section, 0.25 mH for v2 and
0.22 mH for v3 and finally the capacitor in the LCR
circuit, 3.3 uF for v2 and 2.2 uF for v3.
I am very happy for the evaluation given by Darryl in
Australia and with his permission, here are his
comments:
I finally got around to experimenting with resistor
value increases in the notch filter, which you
suggested might restore some of the "life" or
"technicolour" sound to your latest (final?) crossover
version.
Increasing the resistor to 12 ohms does do this to
some small extent I guess, but any greater value
begins to re-introduce the upper midrange glare
quite audibly (to my ears, anyway). All things
considered, I still prefer the sound with the 10 ohm
value, i.e. an optimally flat response in the 2 KHz
area.
I did find that reducing the resistor on the tweeter
from 5.6 ohms back down to 5 ohms produced quite
an improvement - I should have tried this before -
and restored much of that distinctive Proac sound,
more so than I would have expected. (With the
standard (Jacq) crossover + notch filter, I preferred
the 5.6 ohms you recommend.) Increasing the tweeter
output in your latest crossover makes it a lot harder
to choose between the two versions. Even with
increased tweeter level, sibilance is still better
controlled and the midrange sounds more realistic
than it does with the Jacq version + notch filter. I
think I'll stay with your latest version for the time
being, albeit with slightly increased treble. That
change has swung things the other way for me. It
seems a good compromise in my system, and 90 per
cent of the time it sounds wonderful.
Incidentally, the listening tests I've been carrying out
have been with a Dynaco PAS3X/Stereo 70 valve
preamp and amp. I also have a Sugden C51/P51
solid state combo, but it's off for repair at the
moment.