the flat response - Hificritic.com

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FIG.2 The vertical marker is placed at 12.5kHz, and graphically demonstrates the declining final octave, even when measured directly on-axis, with the mic on the “hottest” angle. Down 3dB at 12kHz, it was -10dB by the 20kHz 1/3-octave band. This graph also shows the output of the bass driver and its excessive level when interfaced with the tweeter, typically 6-8dB too high. (Note that this curve will encompass some significant nearfield effects, particularly in the bass.) FIG.3 Fig.3 is a composite of the axial response, plus the output at 10 degrees above axis, and 30 degrees off the horizontal axis (dashed curve and toward the centre stage). This shows that the output off-axis is pretty well maintained in the desired manner. At 30 degrees to the horizontal, the 12kHz region picked up a little but with no significant improvement in response extension. On driver integration alone, the
Duetta can be rated well enough . Finally, we come to the computer-averaged response assessed in the listening space (fig.4), a summation of some 64 responses. In my 80m³ room, the 30Hz and 25Hz bands were clearly excessive in level, with the 30Hz rising 12dB above the computed median. Note that the bass rise was part of a rising curve and not an isolated “boom”. From the response it is clear that the general energy trend is rather rich, with the midrange broadly weighted to a maximum in the 400Hz to 1kHz sector (the marker is at 1kHz). Above 1kHz, the output declined some 5dB, though in a fairly controlled manner. The average output held up to 10kHz with a desirably smooth roll-off thereafter. The dotted curve shows the effect of the 1.5-ohm bass resistor - a mild improvement in balance. FIG.4 Larger rooms would definitely improve the Duetta's bass-mid balance, though the low bass would remain over powerful down to 30Hz. For the benefit of those readers not familiar with these room-averaged responses, I can assure you that it is possible to obtain a room curve using this method which runs within ± 3dB 25Hz to 200Hz, ±2dB 200Hz to 8kHz, with a gentle roll-off thereafter. (This latter effect is due to the finite directivity of almost all commercial tweeters at higher frequencies.) Blind listening tests have shown a consistently good correlation between perceived response and the room measurement. Technical Test Results: Martin-Logan CLS Looking at the amplifier load factor, the impedance curve (fig.5) is typically “electrostatic”. Low at low frequencies, and with no visible signs of the 50Hz diaphragm resonance, it climbs steeply to a harmless 33 ohms by 1kHz. Above this level, the load is almost purely capacitive, falling with frequency at 6dB/octave, reaching 2.5 ohms at 10kHz and finally bottoming out at a value of 1.6 ohms at 20kHz largely capapcitance. Wide-band synthesizers played at high level will not do
Page 1 and 2: _____________________ THE FLAT RESP
Page 3 and 4: in a true ribbon form. The magnet s
Page 5 and 6: lossy foam-plastic mounting is used
Page 7 and 8: I shall leave sound quality rather
Page 9 and 10: This CLS was better balanced than b
Page 11: For the record, the Quad ESL-63, wh
Page 15 and 16: 50Hz, and, in my view, showed exces
Page 17 and 18: FIG.10 The CLS offered a below-aver
Page 19: * Provisions have been made for the

the flat response - Hificritic.com

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