”OD-111b” Omni directional book-shelf loudspeaker, improved low-frequency capabilities


The design idea

The speakers are easy to place in a home due to their small measures and multiple ways to be placed. They can be placed wall hanging, standing in a bookshelf or standing on the floor. This version however is designed primarily for placing in a bookshelf.
This three way version is, like the “OD-111a”, a more bass capable and larger version of the OD-11. The bass reflex port is placed on the backside facing the wall where the feet ensure the correct distance to the wall. Midrange and high range are tilted inwards and upwards in order to have a better stereo effect in the entire room. This design ensures small variations in sound in different listening positions.
The woofer is not angled in due to its low crossover frequency where there is no directional information in the sound. The midrange is angled inwards 30 degrees and the tweeter 36 degrees inwards. The angle of the mid- and high range affects mainly the level of direct sound and the first reflected sound from the ceiling in different locations in the listening room. The direct sound shows only small variations at different locations in the room. The first reflected sound from the ceiling has, in relation to the direct sound, a small difference in direction and will therefore be of approximately the same strength. Since the difference between the direct and reflected sound is small the speaker will in some aspects behave as an omni directional speaker. This explains the integrated and relaxed sound reproduction.

Measures, estimated
Box volume: 30 litres estimated
Measures W x H x D: 51 X 29 X 29 cm

Drive units, estimated
Woofer: 1pc. 20.5 cm
Midranges: 1 pc 13 cm (alternate version with 2” dome speaker NOT angled inwards)
Tweeters: 1 pc. 5 cm 8 ohms Peerless MT 20 HFC

Cross over frequencies: 700 and 3000 Hz.

Explanations to figure
4 Back side of speaker, with feet and bass reflex port
16 Woofer
17 Mid range
18 Tweeter
19 Baffle
20 Concave part of baffle for midrange and tweeter


Martin Dellstig – Co-Editor

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