Floorstanding loudspeakers — Linkwitz LX521-The Reference

The LX521-The Reference is an active four-way open-baffle loudspeaker designed by Siegfried Linkwitz at Linkwitz Lab and now built as a finished product for LINKWITZ.store. The first LX521 appeared in 2012 with a three-way analogue active crossover and a passive network between the two midrange drivers. The LX521.4 of 2015 moved to a true four-way layout, the ASP crossover followed in 2017, and ASP V2.0 arrived in 2021 together with the magnesium-cone LX521.4MG. The ASP.4 is described as the last version completed before Siegfried Linkwitz died, and the drivers and baffle geometry have stayed unchanged since the original design. In Europe a pair costs from about EUR 20,111 to EUR 30,821 including VAT, depending on finish and options.

Key specs that matter

Each speaker carries six SEAS drivers. Two 27TFF 1 inch textile dome tweeters face front and rear, a 4 inch MU10RB-SL woven cone covers the upper midrange, and an 8 inch LINKWITZ22MG magnesium cone handles the lower midrange, replacing the earlier U22REX/P-SL polypropylene unit on all turnkey systems. Two 10 inch L26ROY aluminium cone woofers work in the LXsub4 V-frame bass sections, which weigh 33 kg each. A complete speaker stands about 125 cm tall, 38 cm wide and 38 cm deep, and the pair with woofers weighs about 130 kg. Amplification requires five channels per speaker, ten in total.

Engineering and use context

All drivers radiate from an open baffle, so output leaves the front and the rear in a figure-of-eight dipole pattern instead of being enclosed in a box. The design target is a flat frequency response on axis and off axis across the horizontal plane and the frontal hemisphere, which means the direct and reflected output reaching the listener share the same response. The ASP V2.0 crossover is an analogue line-level unit with cascaded, phase-compensated filters, which keeps the whole signal path analogue. Finishes include American Walnut over a black HDF core or over Panzerholz, high-gloss walnut, a transparent acrylic top, an aluminium and Panzerholz sandwich top, and custom woods on request. The maker asks for a room of at least 25 m2, and Linkwitz Lab gives a minimum room volume of 65 m3.

Pairing

LINKWITZ.store offers PowerBox 6pro NCore units based on Hypex NCore modules, all with the same 26 dB voltage gain, and supplies 0.7 m SpeakOn cables. In that configuration the tweeter channels receive 100 W, each midrange channel 125 W and the woofers 500 W. Linkwitz Lab states the general need as eight to ten power amplifier channels of 50 W to 200 W, and any source or preamplifier with a line output drives the crossover.

Alternatives

The Linkwitz LXstudio places a smaller LXmini upper section on the same LXsub4 dipole woofers and needs only eight amplifier channels.