{"id":2242,"date":"2012-06-02T08:08:12","date_gmt":"2012-06-02T08:08:12","guid":{"rendered":"http:\/\/www.audioexcite.com\/?page_id=2242"},"modified":"2019-04-24T14:46:39","modified_gmt":"2019-04-24T14:46:39","slug":"seas-h1499-27tbcdgb-dxt","status":"publish","type":"page","link":"https:\/\/www.audioexcite.com\/?page_id=2242","title":{"rendered":"SEAS H1499 27TBCD\/GB-DXT"},"content":{"rendered":"

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

 <\/p>\n

\"\"<\/a><\/p>\n

The 27TBCD\/GB-DXT is an aluminium\/magnesium alloy dome tweeter with a DXT\u00ae (Diffracton Expansion Technology) lens.<\/p>\n

The DXT\u00ae tweeter addresses the major issues regarding directivity control in traditional loudspeaker designs. DXT\u00ae solves several well-known issues regarding; directivity control, off-axis response, integration with midrange units and baffle diffractions.<\/p>\n

From approximately 7 kHz the diffraction edges begin to work. At the very high frequencies the DXT\u00ae uses up to 3rd order diffraction to expand the sound \ufb01eld. At lower frequencies the DXT\u00ae tweeter operates as a waveguide to narrow the mid-band dispersion.<\/p>\n

Stiff and stable rear chamber with optimal acoustic damping allows the tweeter to be used with moderately low crossover frequencies. A \ufb01ne mesh grid protects the diaphragm.<\/p>\n

Seas spec. sheet:
\n27TBCD\/GB-DXT (H1499)<\/a>
\nDXT Technology<\/a>
\nDXT Website<\/a><\/p>\n

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

 <\/p>\n

\"\"<\/a>Lower resonance frequency than the official SEAS specification and showing a 5% variation between the two driver unit samples.<\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

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

 <\/p>\n

\"\"<\/a>The DXT tweeter doesn\u2019t use ferro-fluid in the magnetic gap. The double peak in the impedance plot indicates some sort of cavity resonance. The impedance plot shows a slight variation between the two driver unit samples. Overall a good consistency between the two samples.<\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

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

 <\/p>\n

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

The tweeter is measured mounted in a 14 liter Dayton Audio enclosure (PartsExpress part #302-721) baffle with the following conditions:<\/p>\n

Baffle size (WxH):<\/strong> 21,59\u00d735,56cm (8,5\u2033x14\u2033)<\/p>\n

Driver position:<\/strong> Mounted on center-line with driver unit center 8cm from the top of the baffle.<\/p>\n

Mic position:<\/strong> 1m distance, on tweeter-axis.<\/p>\n

Smoothing:<\/strong> 1\/24 octave smoothing applied.<\/p>\n

\"\"<\/a><\/p>\n

0deg tweeter-axis:
\nSample 1 = Blue
\nSample 2 = Red<\/p>\n

Virtually the same frequency response between the two samples except for some sort of cancelation for sample 1 at 21kHz. Between 1.5-4kHz the baffle diffraction is noticed as dips and peaks in the frequency response. This is reduced in the off-axis measurements.<\/p>\n

The tweeter has a sharp peak centered at 27kHz which is caused by the hard dome cone break-up. This cone break-up behavior is very common among hard dome tweeters and is often noticed as increased odd-order distortion between 5-10kHz, depending where the cone breakup occurs. Many people refers this as \u201csounding metallic\u201d, while others claim it can\u2019t be heard.<\/p>\n

\"\"<\/a><\/p>\n

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

\"\"<\/a><\/p>\n

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

Thanks to the DXT lens the tweeter has a remarkable controlled off-axis response and frequency dispersion!<\/p>\n

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

 <\/p>\n

\u00a0Measurement setup:<\/strong><\/p>\n