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<blockquote data-quote="Art Welter" data-source="post: 217274" data-attributes="member: 52">The BMS 4594 has a 90mm (3.5&quot;) voice coil, the diaphragm is slightly wider than the DCX464&#039;s.At 400Hz, the rating drops from 1kw peak to 150W RMS.[ATTACH=full]209681[/ATTACH]The reduction in diaphragm area between the 100mm of the B&amp;C DCX464 vs the B&amp;C DCX354 76mm voice coil is significant, the smaller being about half the Sd (diaphragm surface piston area) of the larger. Assuming the same Xmech, there should be just under 6dB difference in displacement limited output.The difference in Sd is similar to that between an 18” and a 12”.The hole in the center of an annular diaphragm reduces the Sd in comparison to a dome diaphragm, but larger diaphragm to phase plug spacing is possible with reduced high frequency.The 100mm diaphragm appears about 14mm wide, an Sd of 3.4 square inches (22 square cm).The 76mm diaphragm appears about 10mm wide, an Sd 1.84 square inches (11.94 square cm), just over half the displacement assuming the same excursion.The above computations assume a flat Sd, while the annular diaphragms have&nbsp; a “V” shaped diaphragm cross section, so the Sd would be larger than indicated, but by the same ratio assuming similar “V”&nbsp; angles.The BMS 4594 drops at around 6.8kHz, slightly higher than the B&amp;C DCX464.The DCX464 may have more excursion than the BMS 4594’s +/-0.8mm,&nbsp; so could still have more displacement.Art2/26/23 edit-the Sd of the B&amp;C DCX354 is larger than the estimations above, so displacement assumptions made are incorrect, sorry for the errors!</blockquote>

[QUOTE="Art Welter, post: 217274, member: 52"] The BMS 4594 has a 90mm (3.5") voice coil, the diaphragm is slightly wider than the DCX464's. At 400Hz, the rating drops from 1kw peak to 150W RMS. [ATTACH type="full" alt="DCX354 vsDCX464vsBMS4594.png"]209681[/ATTACH] The reduction in diaphragm area between the 100mm of the B&C DCX464 vs the B&C DCX354 76mm voice coil is significant, the smaller being about half the Sd (diaphragm surface piston area) of the larger. Assuming the same Xmech, there should be just under 6dB difference in displacement limited output. The difference in Sd is similar to that between an 18” and a 12”. The hole in the center of an annular diaphragm reduces the Sd in comparison to a dome diaphragm, but larger diaphragm to phase plug spacing is possible with reduced high frequency. The 100mm diaphragm appears about 14mm wide, an Sd of 3.4 square inches (22 square cm). The 76mm diaphragm appears about 10mm wide, an Sd 1.84 square inches (11.94 square cm), just over half the displacement assuming the same excursion. The above computations assume a flat Sd, while the annular diaphragms have a “V” shaped diaphragm cross section, so the Sd would be larger than indicated, but by the same ratio assuming similar “V” angles. The BMS 4594 drops at around 6.8kHz, slightly higher than the B&C DCX464. The DCX464 may have more excursion than the BMS 4594’s +/-0.8mm, so could still have more displacement. Art 2/26/23 edit-the Sd of the B&C DCX354 is larger than the estimations above, so displacement assumptions made are incorrect, sorry for the errors! [/QUOTE]

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