Harwood Acoustics LF8 MK5.9 Polypropylen Membrane (bass-midrange of the BBC LS 5/9)

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-8 %

RRP 249,00 €

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Harwood Acoustics LF8 MK5.9 Polypropylen Membrane (bass-midrange of the BBC LS 5/9)

We already know the LF8 MKIIITief midrange driver with the transparent polypropylene diaphragm since the mid-80s, when we purchased it directly from H.D. Harwood in England together with the LF5 MKIII. This original LF8 still consisted of a sand casting basket and was "state of the art" for many years. Over the years, the basket was changed to solid aluminum die casting and they were subsequently installed MKIV and MKV until the end of the 90s in the Monitor-DIY- speakers from Harwood. Basically, with all the different MK versions, however, the Navi polypropylene membrane and the black rubber surround as well as the TSP had never changed significantly.

In many BBC trials from the early 80s, the advantages of the polypropylene membrane were confirmed, but it was felt that the beading material should follow the membrane to achieve a homogeneous oscillating body. This resulted in this MK5.9 special type, which was developed for BBC use as monitor LS 5/9 in combination with the Audax HD13D34 (today TWO34XS with grille).

We can now again offer this LF8 MK5.9 with its excellent sound properties of the "unfilled" polypropylene diaphragm in Navi form and of course in the aluminium die-cast basket, as it was originally developed by the BBC.

By the way, it is also suitable as a replacement woofer for many tried and tested kit combinations with the LF 8 MK III to V types or with the original BBC monitor speakers LS 5/9 - where it is used again today.

Short data

Usage as Bass-Midrange
Power Handling 60 Watt
Impedance 8 Ohm
Max. Frequency 4 kHz


Overall dimensions 220 mm
Baffle cutout 185 mm
Depth (Total) 90 mm
Front material Aluminium diecast
Frame Material Aluminium diecast
Membrane Type Cone
Membrane Surround Soft-PVC
Membrane Material Polypropylene
Voice coil Ø 25 mm
Voice coil material Aluminium
Magnet Ø 100 mm


Resonance fs fs: 45.3 Hz
Mechanical Q Qms: 3.82
Electrical Q Qes: 0.57
Total Q Qts: 0.49
Equivalent Air-Volumen Vas: 48.5 Liter
DC-Resistance Re: 6.3 Ohm
Coil Inductance Le: 0.40 mH
Mech. Compliance Cms: 0.86 mm/N
Moving Mass Mms: 14.4 g
mech. Resistance Rms: 1.1 kg/s-¹
Max. Excursion +/- Xmax: 4.8 mm
BL Product Bl: 6.7 N/A
Membrane Area Sd: 50.24 cm²
Sound pressure dB: 90.8 SPL
Efficiency Nref: 0.77 %



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