The next driver measurements to publish for the Sequence Three \u2013 Grand Reference<\/strong> loudspeaker design is the AudioTechnology 15H 52 12 06 SDKM. This is the pure mid-range version of the 15cm AT driver.<\/p>\n The mid-range is an over-hung version with a special mid-range surround for optimized frequency response. Measurements for the under-hung mid-woofer can be found here: AudioTechnology C-Quenze 15H 52 06 13 SDK<\/a><\/p>\n If we compare the two different versions we can see that the mid-range version both have a more linear frequency response as well as lower distortion throughout the mid-range drivers usable frequency range.<\/p>\n <\/p>\n Blue<\/strong> = 15H 52 12 06 SDKM (mid-range) Note!<\/strong> The SPL is normalized. They don\u2019t have the same sensitivity.<\/p>\n The dip in the frequency response at 1.25kHz for the mid-woofer version caused by the cone-edge resonance is completely eliminated with the specially constructed surround of the mid-range driver.<\/p>\n To be honest, this dip in the frequency response is more of a cosmetical nature rather than technical, since it doesn\u2019t have a large impact on the sonic performance of the mid-woofer.<\/p>\n The mid-range is perfectly usable up to about 3-3.5kHz and my goal is to use it up to 3kHz +\/- 200Hz, where it\u2019s crossed-over to the RAAL 140-15D ribbon tweeter.<\/p>\n Simulations, measurements and listening test will determin which filter topology to use, LR2 or LR4? If it works I would like use a shallower sloped filter e.g. a second-order LR, since I often think such filter topology sounds better if it can be done properly.<\/p>\n Time will tell what\u2019s possible and feasible. \ud83d\ude42<\/p>\n <\/p>\n Left:<\/strong> = 15H 52 12 06 SDKM (mid-range) @ 1m 90dB As can been seen the distortion is higher for the mid-woofer version when tested at medium-high levels. This mid-range driver from AudioTechnology delivers top notch measurement performance without any surprises as nasty cone break-ups, odd frequency response or distortion problems.<\/p>\n I think the mid-range will complement the RAAL 140-15D perfectly!<\/p>\n![\"\"](\"https:\/\/www.audioexcite.com\/wp-content\/uploads\/2013\/09\/AT15H-SDKM-vs-SDK.jpg\" "\\"AT15H")
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\nRed<\/strong> = 15H 52 06 13 SDK (mid-woofer)<\/p>\n![\"\"](\"https:\/\/www.audioexcite.com\/wp-content\/uploads\/2012\/09\/15H521206SDKM-1L-15cm-90db.jpg\" "\\"15H521206SDKM-1L")
<\/a>![\"\"](\"https:\/\/www.audioexcite.com\/wp-content\/uploads\/2012\/02\/15H520613SDK-1L-15cm-90db.jpg\" "\\"15H520613SDK-1L")
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\nRight:<\/strong>= 15H 52 06 13 SDK (mid-woofer) @ 1m 90dB<\/p>\n
\nTo sum up!<\/strong><\/p>\n