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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.

Open Baffle Speaker

 




















Open Baffle 18" Speaker

 





















Speaker Crossover
















Thanks to the following for information and inspiration for this project:

 

G.A. Briggs - Chapter 17 Baffles
http://members.myactv.net/~je245/obriggs.htm

 

Great Plains Audio

http://www.lowther-america.com/page2/page12/page19/page19.html 

Lampizator Projects (Endorphin P-17 and P-18; Open Baffle P-19)

http://www.lampizator.eu/SPEAKERS/PROJECTS/html

 

Martin J. King - Designing a Passive Two Way Open Baffle Speaker System, 2007

http://www.quarter-wave.com/OBs/OB_Design.pdf

 

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