| 3 Pi Build [message #62972] |
Sat, 29 May 2010 22:27  |
rkeman
Messages: 78
Registered: March 2010
Location: Florida
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Having just completed a set of 3 Pi speakers with 8 ohm AE TD12S woofers and B&C DE250-8 drivers, an important issue has come up. The sound is fairly bright and forward and the speakers show a 5-7 db plateau above 2kHz or so. The speaker is reasonably flat over the band from 40Hz to 1kHz and above 2kHz using 1/3 octave pink noise and 1/10 octave warble tones. Both speakers have essentially identical response curves and other quality speakers have not shown similar behavior using the same measurement techniques in this room. The crossovers are fabricated to specifications using Mills 30 ohm 12w resistors as R1a-d, 28 ohms for each R2 leg (8 and 20 ohm values), and Erse PulseX caps (20 mF, 6.8 mF and 0.47 mF), and Erse 14 gauge coils (1.5 mH and 1.0 mH). Checking everything but the coils with a multimeter yields the expected values. R13 insulation covers one wall, rear, top and two shelf braces as recommended. The polarity of the tweeter is reversed as called for in the design. The front panel configuration, port placement and size and internal volume are all to specification. Is the 3 Pi simply voiced with a prominent high end or is something amiss?
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