Monacor Cobra-Horn floorstanding loudspeaker in Hobby HiFi 1/2013

Kit without housing price per speaker

Cobra Horn is an inexpensive 2-way horn loudspeaker with a full-range speaker, which is replaced by a piezo tweeter above approx. 5kHz. Piezo tweeters were mostly used in inexpensive PA loudspeaker boxes. They have the property that they can be connected directly without a crossover. Bernd Timmermanns uses this box to show how piezo tweeters can be used in a tonally balanced manner using a crossover. The piezo tweeter is controlled by a 3rd order high pass. A resistor is parallel to the tweeter so that it has a simple impedance behavior. The crossover contains a second order low pass for the full-range speaker. The frequency response of the loudspeaker box is wavy, as is typical for a horn, but overall it is balanced and without any significant exaggeration. The non-linear distortions are very low and the waterfall diagram largely fades away quickly.

Technical data:

• Impedance: 8 Ohm
• Sound pressure level (2.83V/1m): 93 dB 
• Dimensions (HxWxD): 1078 x 338 x 500 mm 
• Frequency range (-8dB): 50 - 33000 Hz
• Crossover frequency(s): 4800 Hz
• Principle: Horn

Highlights

• Monacor SP-200 X broadband loudspeaker
• Monacor MPT-025 piezo tweeter
• PE foam sealing strip, 5x2 mm
• 2.5x Sonofil insulation material 100 x 35 cm for 20 liters
• 2 pole terminals PK31, pair, gold-plated, red+black
• 3m speaker cable 2x1.5 mm2, transparent
• Pan screws 4x20 black, 12 pieces
• Construction plan for the kit the crossover components, to be built on wood:
• Audaphon MKP CAP Superior 0.33 μF / 400 Vdc
• Audaphon MKP CAP Superior 1.0 μF / 400 Vdc
• Audaphon MKP CAP Superior 1.5 μF / 400 Vdc
• 0.5 mm air coil, 1.5 mH/1.85 0hm
• 1.0 mm Air coil, 0.47 mH/0.32 Ohm
• Metal oxide resistor MOX5 47 Ohm (yellow-violet-black)