OPEN BAFFLE SPEAKERS
This project was an experiment, as a way of finally using my Lowther DX3s and a pair of Fane bass speakers (found by the side of the road on hard waste day - they had been used in a bass amp speaker cabinet for twenty years, and then sat in a shed for another twenty years - nicely worn in).
Quite simply - an outstanding result - and that is with a rubbish Sanyo solid state receiver (also found by the side of the road - who needs to spend big dollars to get world class audio? Not me). I can't wait to hear them with a proper single ended triode amp. Mid-range detail and bass clarity I've not heard before - I will need to start listening to my entire record and CD collection all over again. I love it when an experiment pays off. These will be the last speakers I build for myself for many years - they are that good.
The specification is as follows:
Baffle height: 56"
Baffle width: 25"
20 mm marine ply.
Baffle sloped 10° to the rear to time-align the drivers.
Fane 18" speaker: centre 13" from floor.
Lowther 8" speaker: centre 34" from floor, offset 3" from centre line.
Tweeter 2" speaker: upward firing from the top of the baffle.
Acoustic shelf: 26" from floor, 9" wide and 6" deep, centre aligned with the Lowther.
Bass box sides: 10" deep at the bottom, 5" deep at top, 26" height.
Bass port shelf: fitted across the centre of the bass speaker.
Crossover: 6dB per octave
Bass turn-over frequency 120 Hz
Lowther roll-off frequency 240 Hz (high frequencies not rolled off)
Tweeter roll-off frequency 6,000 Hz 12dB per octave
Hand wound 16mH inductors, polypropylene capacitors for mid-range cross-over, paper-in-oil capacitors for the tweeter crossovers.
Thanks to the following for information and inspiration for this project:
G.A. Briggs - Chapter 17 Baffles
Great Plains Audio
Lampizator Projects (Endorphin P-17 and P-18; Open Baffle P-19)
Martin J. King - Designing a Passive Two Way Open Baffle Speaker System, 2007