Multimedia speakers

The Dutch magazine Audio & Techniek once published an article about one-way loudspeakers that were based on Audax units 1. Although speakers using just a single full-range unit per audio channel were disregarded in audiophile circles (high intermodulation distortion), they could also have important advantages (excellent imaging). The editors of Audio & Techniek were enthusiastic about the Audax sound; they claimed that the single driver flaws were minor and the advantages were huge. We never heard so much soundstage for so little money” was their comment. Audiophile convictions are subject to fashion like every other human opinion.
Multimedia speakers - schematic

In the 1960s, speaker builders considered full-range drivers from Philips (9710M, 9710AM) a best buy”. Such speakers were efficient and could be used with valve amplifiers. In the 1970s, bextrene woofers, soft dome tweeters and complex filters became popular. Because of the low efficiency and heavy load of such speakers, powerful solid-state amplifiers were required to drive them. But history tends to repeat itself. In the 1990s, valve amplifiers and full-range speakers reappeared. The published frequency response is exceptionally smooth (100 Hz to 18 kHz within 3 dB) and free of major dips (see above). The price was only 30 Euros (for a single unit, 60 Dutch guilders in 1995). Based on the Boxcalc simulation, I built two speaker cabinets from MDF. Outside dimensions: height 400 x width 180 x depth 312 mm, wall thickness 18 mm, reflex port on the back (diameter 50 mm, length 150 mm, equal distances to cabinet sides, center of port 115 mm from cabinet bottom), drive unit on the front (equal distances to cabinet sides, center of cone 120 mm from top of baffle). One reinforcing lath (50 mm wide, 18 mm thick), running from front to back at the center of the front and back panels, to stiffen the cabinet. Enclosure stuffed with polyester wadding, amount as specified by the manufacturer (Monacor). I used only wood glue, no screws. Parameters of the SPH-60X are shown in the right column of the following table: free air...

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