Multimedia speakers

The Dutch magazine Audio & Techniek once published an article about one-way loudspeakers that were based on Audax units. Although speakers using just a single full-range unit per audio channel were disregarded in audiophile circles due to high intermodulation distortion, they could also have important advantages such as 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. 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. The price was only 30 Euros (for a single unit, 60 Dutch guilders in 1995). Based on the Boxcalc simulation, two speaker cabinets were built 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). Only wood glue was used, no screws. Parameters of the SPH-60X are shown in the right column of the following table: free air resonance 60 Hz, power rating 30 W, Sensitivity 89 dB (1 W / 1 m), Suspension compliance 1.19 mm/N, moving mass 5.9 grams, mechanical Q factor 2.17, electrical Q factor 0.53, total Q factor 0.42, Compliance Equivalent Volume 9 liters, DC Resistance of Voice Coil 6.2 Ohms, Inductance of Voice Coil 0.4 mH at 1 kHz, Effective Cone Area 75 square cm.

The construction of a one-way loudspeaker system using Audax units emphasizes the importance of cabinet design and driver selection in audio performance. The chosen dimensions of the cabinet, specifically 400 mm in height, 180 mm in width, and 312 mm in depth, are critical for achieving the desired acoustic properties. The wall thickness of 18 mm provides adequate rigidity to minimize unwanted vibrations that could color the sound output. The reflex port, strategically placed at the back of the enclosure, facilitates bass response by allowing the rear sound wave of the driver to interact with the front wave, enhancing low-frequency performance.

The positioning of the drive unit, centered 120 mm from the top of the baffle, ensures optimal sound dispersion and imaging, critical factors for achieving a wide soundstage. The inclusion of a reinforcing lath running from front to back serves to further stiffen the cabinet, reducing resonance and improving overall sound clarity. The use of polyester wadding as damping material is essential for controlling internal reflections and standing waves within the enclosure, contributing to a more accurate sound reproduction.

The selected SPH-60X driver parameters indicate its suitability for this application. With a free air resonance of 60 Hz, the driver is capable of producing adequate bass response. A power rating of 30 W allows for compatibility with various amplifier types, including both valve and solid-state options. The sensitivity of 89 dB (1 W / 1 m) indicates an efficient driver that can produce a significant sound output with minimal power input, making it an ideal choice for budget-conscious audio enthusiasts.

Overall, the design and assembly of this loudspeaker system reflect a thoughtful approach to achieving high-quality audio reproduction while balancing cost and performance, demonstrating the enduring appeal of full-range drivers in the audiophile community.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. 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 resonance 60 Hz, power rating 30 W, Sensitivity 89 db (1 W / 1 m), Suspension compliance 1.19 mm/N, moving mass 5.9 grams, mechanical Q factor 2.17, electrical Q factor 0.53, total Q factor 0.42, Compliance Equivalent Volume 9 liters, DC Resistance of Voice Coil 6.2 Ohms, Inductance of Voice Coil 0.4 mH at 1 kHz, Effective Cone Area 75 square cm.

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