The Napoleons are a small DIY loudspeaker designed to deliver a natural tonal balance and clean loud playback from of a small box suited to both small and large rooms, at a reasonable price. This write up was in response to requests from the 2013 Ottawa DIY fest, where the speaker was first shown http://www.diyaudio.com/forums/clubs...2013-a-17.html
Driver Selection
Off axis response irregularities will detract from speaker tonal balance more in a small room than in a large room due to the greater relative strength of indirect sound, compared to direct sound. To help combat this, a tweeter was chosen with some mild horn loading, and a woofer with a well-controlled extended higher frequency response that could take advantage of it.
The Tang band W4-1720 (Tang Band W4-1720 4" Underhung Midbass Driver 264-872) provides powerful and clean mid to upper bass from a very small sealed box. A vented design was avoided to keep the box small and to avoid box/vent unloading which would compromise the high sound pressure levels desired for larger rooms. The mighty little W4-1720 plays ridiculously loud and clean in this application, and mid to upper bass is rich enough to give a pleasant tonal balance. Its smooth mid treble allows a higher crossover point so the tweeter can play loud without strain. This is a good sounding driver, but it can still be made to bottom when over driven by drum test discs. Still, it plays clean and loud enough to pass the I didnt realize it was playing that loud test.
The tweeter is the Vifa D26NC55-06. Its well-controlled off axis response near crossover and its drooping high frequencies off axis reduce splatter in a small reflective room. Its distortion is also very low. While this driver is officially NLA, examples can often still be purchased from on-line suppliers.
Box Dimensions
The sealed box is simple and was built using hand tools and a flush trim bit. Half inch mdf kept the box small which in turn keeps panel vibration under control. The box was made shallow to allow true shelf mounting. Woofer center is 3.5 from bottom, tweeter 7.5. Drivers are centered horizontally.
A different baffle shape (for example due to thicker wood) would change diffraction and affect the response. This could require a crossover change and this design is expressed for 0.5 wood only.
Crossover and Frequency Responses
The crossover is a 6 element second order electrical, in phase driver connection. Special attention was placed on smooth on and off axis response, and a smooth response when standing while listening.
Low pass
L1: 1.5 mH inductor, 0.7 ohms dc resistance (18 gauge air core).
C1: 15 uF cap (not electrolytic)
R1: 1 ohm power resistor (10W or greater)
High Pass
C2: 2 uF cap (not electrolytic)
L2: 1.1 mH inductor, 0.5 ohms dc resistance (18 gauge air core)
R2: 15 ohm resistor, high power (25W or greater)
The full project write up is attached and includes system box tuning, material plan, numerous measurements from 20 Hz to 20kHz, along with design rationale and more detailed build information.
Dave Dal Farra
Driver Selection
Off axis response irregularities will detract from speaker tonal balance more in a small room than in a large room due to the greater relative strength of indirect sound, compared to direct sound. To help combat this, a tweeter was chosen with some mild horn loading, and a woofer with a well-controlled extended higher frequency response that could take advantage of it.
The Tang band W4-1720 (Tang Band W4-1720 4" Underhung Midbass Driver 264-872) provides powerful and clean mid to upper bass from a very small sealed box. A vented design was avoided to keep the box small and to avoid box/vent unloading which would compromise the high sound pressure levels desired for larger rooms. The mighty little W4-1720 plays ridiculously loud and clean in this application, and mid to upper bass is rich enough to give a pleasant tonal balance. Its smooth mid treble allows a higher crossover point so the tweeter can play loud without strain. This is a good sounding driver, but it can still be made to bottom when over driven by drum test discs. Still, it plays clean and loud enough to pass the I didnt realize it was playing that loud test.
The tweeter is the Vifa D26NC55-06. Its well-controlled off axis response near crossover and its drooping high frequencies off axis reduce splatter in a small reflective room. Its distortion is also very low. While this driver is officially NLA, examples can often still be purchased from on-line suppliers.
Box Dimensions
The sealed box is simple and was built using hand tools and a flush trim bit. Half inch mdf kept the box small which in turn keeps panel vibration under control. The box was made shallow to allow true shelf mounting. Woofer center is 3.5 from bottom, tweeter 7.5. Drivers are centered horizontally.
A different baffle shape (for example due to thicker wood) would change diffraction and affect the response. This could require a crossover change and this design is expressed for 0.5 wood only.
Crossover and Frequency Responses
The crossover is a 6 element second order electrical, in phase driver connection. Special attention was placed on smooth on and off axis response, and a smooth response when standing while listening.
Low pass
L1: 1.5 mH inductor, 0.7 ohms dc resistance (18 gauge air core).
C1: 15 uF cap (not electrolytic)
R1: 1 ohm power resistor (10W or greater)
High Pass
C2: 2 uF cap (not electrolytic)
L2: 1.1 mH inductor, 0.5 ohms dc resistance (18 gauge air core)
R2: 15 ohm resistor, high power (25W or greater)
The full project write up is attached and includes system box tuning, material plan, numerous measurements from 20 Hz to 20kHz, along with design rationale and more detailed build information.
Dave Dal Farra