MEASURES
-
Rails: +/- 24VDC under load
-
DC offset at speaker teminals: +/- 2mV
-
BIAS: 1.3A (0.61V on R13/R14)
-
Voltage gain: 10 (20dB)
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): 0.08%
-
THD (at 1 Watt into 8 Ohms at 1kHz): 0.04%
MEASURES
-
Rails: +/- 24VDC under load
-
DC offset at speaker teminals: +/- 2mV
-
BIAS: 1.3A (0.61V on R13/R14)
-
Voltage gain: 10 (20dB)
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): 0.08%
-
THD (at 1 Watt into 8 Ohms at 1kHz): 0.04%
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NOTES
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R7 changed to 52.3k to remove excess negative DC offset at the output of the amp
-
R4 changed to 8.2 Ohms and 220uF bipolar capacitor added to remove DC offset at Edcor input (pin 1)
-
Boards, Edcor transformers and MOSFETs from TeaBag
-
Harris IRFP9240 MOSFETs
-
Matched Toshiba JFETs from FET Audio
-
Dual mono implementation
-
2 x 250VA transformers from Toroidy - 230V primary, 2x18V secondary
-
8 x 22000uF KEMET PEH200 in power supply
-
Deluxe 4U chassis from Hi-Fi 2000
RESOURCES
-
Manual: First Watt M2
-
diyAudio: Official M2 schematic, M2 Clone boards with 120mm UMS spacing
-
Other: Edcor
Last update: 10.03.2019.
NOTES
-
R7 changed to 52.3k to remove excess negative DC offset at the output of the amp
-
R4 changed to 8.2 Ohms and 220uF bipolar capacitor added to remove DC offset at Edcor input (pin 1)
-
Boards, Edcor transformers and MOSFETs from TeaBag
-
Harris IRFP9240 MOSFETs
-
Matched Toshiba JFETs from FET Audio
-
Dual mono implementation
-
2 x 250VA transformers from Toroidy - 230V primary, 2x18V secondary
-
8 x 22000uF KEMET PEH200 in power supply
-
Deluxe 4U chassis from Hi-Fi 2000
RESOURCES
-
Manual: First Watt M2
-
diyAudio: Official M2 schematic, M2 Clone boards with 120mm UMS spacing
-
Other: Edcor
Last update: 10.03.2019.
The Loudspeaker 3
Designed by Troels Gravesen. 3-way semi-active loudspeaker, Hypex FA 501 version, level 1 kit.
SPECS:
-
Sensitivity: 92 dB/2.8V/1 meter
-
Impedance: 8 Ohms for MT section, minimum 6.3 Ohms @ 1250 Hz
-
Dimensions: 45 x 50 x 100 cm, W x D x H
-
Power requirement: 15+ watts/channel for MT section
-
Drivers: 18 SOUND NSD1095N-8 compression driver and XT1086 horn, Faital 8PR210-16, 18 SOUND 15W700
NOTES:
-
Separate midrange and bass/tweeter cabinets
-
Midrange cabinets built from 24mm Baltic Birch and 19mm Valchromat
-
Bass/tweeter cabinets built from 24mm Baltic Birch and 27mm Valchromat (19mm and 8mm glued together)
-
Bracing, crossover box and Hypex box built from 19mm Valchromat
LINKS
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Troels Gravesen's website: The Loudspeaker-3, Tips and ideas, Cabinet damping, Testing high-efficiency midrange drivers
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Speaker kits: Jantzen Audio
-
Faital and 18 Sound drivers: Lean Business Audio
-
Electronic components and loudspeaker accessories: HiFi Collective, Willys Hifi
-
Cabinets: Peter Rawlings videos, Wood Finishes Direct
Last update: 10.05.2025.