{"id":3614,"date":"2013-04-01T14:44:50","date_gmt":"2013-04-01T14:44:50","guid":{"rendered":"http:\/\/www.audioexcite.com\/?page_id=3614"},"modified":"2013-11-21T15:22:04","modified_gmt":"2013-11-21T15:22:04","slug":"kef-sp1632","status":"publish","type":"page","link":"https:\/\/www.audioexcite.com\/?page_id=3614","title":{"rendered":"KEF SP1632"},"content":{"rendered":"

Overview:<\/span><\/h3>\n

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The KEF SP1632 co-axial Uni-Q driver unit is a 5\u201d 4\u2126 mid-range driver paired with a 4\u2126 1\u201d tweeter placed in the centre of the cone. The SP1632 is used by KEF<\/a> in the \u201cR Series\u201d loudspeakers. It has a very sturdy and nice build quality, but this driver can\u2019t be used for mid-woofer duties, since it\u2019s a pure mid-range driver and consequently it has to be used in a three way loudspeaker design.<\/p>\n

The stiff magnesium\/aluminium mid-range cone has special molded braces in the cone in order to control and suppress the mid-range\u2019s cone break-up. The tweeter is mounted in the throat of the mid-range driver and has a “tangerine” wave-guide in front of the dome.<\/p>\n

The shape of the mid-range cone, Z-flex surround and driver design ring together with the \u201ctangerine\u201d technology makes a wave-guide for the tweeter, which in turn gives a super smooth tweeter frequency response with a very wide dispersion.<\/p>\n

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Here\u2019s how KEF R Series<\/a> describes the new \u201cR Series\u201d Uni-Q driver unit:<\/p>\n

“The new Uni-Q MF\/HF driver array is a masterpiece. Midrange response is amazingly fast and clean, thanks to a braced magnesium\/aluminium alloy cone, with KEF\u2019s Z-flex surround smoothing the transition to the front panel and a sturdy die-cast aluminium chassis that prevents resonance being transferred to the cabinet. <\/em><\/em><\/p>\n

At the acoustic centre of the midrange cone is the sophisticated vented tweeter that endows KEF Blade with such startlingly pure HF response. With a large neodymium magnet and a computer-optimised dome structure so stiff that it operates pistonically over its entire working range, the upper registers are articulated with flawless precision \u2013 and to capitalise on Uni-Q\u2019s point source characteristics, KEF\u2019s \u2018tangerine\u2019 waveguide helps to disperse the higher frequencies evenly across a wider angle to flood the room with an intricate and refreshingly natural soundfield. <\/em><\/em><\/p>\n

Operating together as a single, perfectly integrated voice, the array as a whole delivers a sweet, accurate sound of unprecedented clarity.”<\/em><\/p>\n

KEF certainly has the market lead in this segment and by using cutting edge technology it has for a co-axial driver \u201cworld class\u201d performance.<\/p>\n

Note!<\/strong> The KEF SP1632 driver isn\u2019t generally available to DIY:ers. Either it has to be stripped from a loudspeaker in the \u201cR Series\u201d or ordered as a spare part, but this requires a valid \u201cR Series\u201d serial number in order to be able to obtain the driver.<\/p>\n

T\/S Parameters:<\/span><\/h3>\n

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A fairly sensitive mid-range, mainly because of the low Dc resistance.\u00a0 About 8% difference in Fs for the mid-range and about 5% for the tweeter, but overall a good consistency between the driver unit samples.<\/p>\n

Impedance:<\/span><\/h3>\n

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(click on picture to zoom)<\/p>\n

Left:<\/strong> Mid-range free-air impedance sample 1 vs. sample 2.<\/p>\n

Right:<\/strong> Tweeter free-air impedance sample 1 vs. sample 2.<\/p>\n

Slightly different impedance profile between the tweeter samples. Based on the impedance response, it looks like the tweeter uses ferro-fluid in the magnetic gap.<\/p>\n

Frequency:<\/span><\/h3>\n

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Frequency measurement conditions:<\/strong><\/p>\n

The mid-range is measured mounted on a baffle in an 2.5 liter (net volume) closed mid-range enclosure with the following conditions:<\/p>\n

Baffle size (WxH):<\/strong> 22,86\u00d755,88cm with 12mm round-over on the baffle edges (r=12).
\nDriver position:<\/strong> Mounted on center-line with driver unit centered in the middle of the baffle.
\nMic position:<\/strong> 1m distance, on mid-range\/tweeter-axis. Measurement valid down to 275Hz.
\nSmoothing:<\/strong> 1\/24 octave smoothing applied.<\/p>\n

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Mid-range:<\/strong><\/p>\n

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(click on picture to zoom)<\/p>\n

Left:<\/strong> Frequency response on-axis (Blue=sample1, Red=sample2).
\nRight:<\/strong> Frequency response 15deg off-axis (Blue=sample1, Red=sample2).<\/p>\n

The two mid-range samples measures virtually the same, which indicates good consistency in the manufacturing process.<\/p>\n

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0deg = Blue
\n15deg = Red
\n22.5deg = Green<\/p>\n

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30deg = Blue
\n45deg = Red
\n60deg = Green<\/p>\n

Summary:<\/strong><\/p>\n

Very smooth frequency response up to 2kHz where it gradually starts to smoothly roll-off. No visible sharp cone break-up effects due to the hard stiff mid-range cone.The mid-range has an usable frequency response up to about 3kHz.<\/p>\n

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Tweeter:<\/strong><\/p>\n

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(click on picture to zoom)<\/p>\n

Left:<\/strong> Frequency response on-axis (Blue=sample1, Red=sample2).
\nRight:<\/strong> Frequency response 15deg off-axis (Blue=sample1, Red=sample2).<\/p>\n

The two tweeter samples measures virtually the same, which indicates good consistency in the manufacturing process. Note the sharp aluminium cone break-up around 39kHz. This break-up is about 10-15kHz higher up in frequency than usual for this size\/type of dome tweeter. The break-up influence is well outside the tweeters usable frequency range.<\/p>\n

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0deg = Blue
\n15deg = Red
\n22.5deg = Green<\/p>\n

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30deg = Blue
\n45deg = Red
\n60deg = Green<\/p>\n

Summary:<\/strong><\/p>\n

The \u201ctangerine\u201d waveguide works as advertised and the tweeter has a very extended smooth frequency response, well above 30kHz with great dispersion. It has no signs of any sharp dips in the frequency response between 10-20kHz, which is very common for waveguide mounted tweeters. For a co-axial driver unit, this is simply an outstanding performance.<\/p>\n

Distortion:<\/span><\/h3>\n

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Measurement setup:<\/strong><\/p>\n