Having spent a fortnight testing these ,they proved a difficult driver to get aligned with other SB drive units . The measured baffle FR looks nothing like the manufacturers nor for that matter as given by HiFi Compass but more akin to that tested by Troels Gravesen. A big reason for measuring your own FRD . . See below FR plot . Its not to say the actual FR could not be made to integrate for FR ( as there is plenty of headroom in the efficiency ) but more surprising than anything else when measured OA . The units were ordered to replace Peerless 821616 (M122 ) as used in the Krell Resolution 1 ( polyprop apparent quacking cone syndrome) .. The SB MD60N is not nearly as 'flat' as these but I fancied a change . There is a 2 db dip at 1k as noticed/measured by others but the rest of the FR dealt with relatively comfortably with LR2 ( apart from a 0.56 uf across the HF roll off inductor ) at 700 and 3800 . The issue found was phase .. No matter what was done phase became an issue at either end of the pass band .. It eventually measured great but without major alterations in the bass and HF ,it wasn't going to cut it for this project . The driver that eventually went in no issues at all .. But I will keep these for another brand new project . QA spot on ,,, gave virtually no difference in FRD nor ZMA between the two drivers delivered . Packing and turn around as usual top notch . Graph below Holm impulse at OA 500mm on a 530x 300 baffle 1/6th smoothed ungated raw driver. THD well below 1% in the pass band used .
