Abbingdon Music Research LS-77 owner manual

While one can (and should) add acoustical treatment to large spaces, these are only effective to a certain degree and not at really low frequencies. To effectively damp the reflection of a 350Hz tone the layer of damping material applied to the wall would have to be at least 25cm thick! Instead of damping the reverbrations, using speakers that exhibit a significant increase in directivity at all frequencies over traditional systems attains an equal or greater improvement.

Thus the larger the room the more closely must the speaker control directivity to retain the same ratio between the actual recorded sound and that produced by the room reverberation at any given frequency.

The AMR OptiArray® system provides a speaker system that can be expanded from a single pair, which is appropriate in terms of directivity and acoustic output for rooms up to around 35m2 (with normal ceiling height), via a dual pair system that covers up to 70m2 and scales through intermediate configurations of four and eight pairs of speakers finally up to sixteen pairs in a 'focused dual line array' configuration, used to cover cavernous listening spaces of up to 480m2*.

Due to the carefully considered directional properties of the single LS-77 and its seamless integration into larger arrays. Each larger size array extends the tight (40o) vertical and wide but controlled (120o) horizontal radiation angle to lower frequencies, counteracting the room’s tendency to have increasing reverb times at a given low frequency with increasing room size.

A 2m tall vertical array of eight LS-77s manages to control the sound radiation down to 80Hz, whereas a single LS-77 provides controlled directivity only down to 360Hz (which is still much lower a frequency than most high fidelity speakers manage and entirely appropriate for moderate sized rooms).

*Note - A room of 480m2 is a small concert hall around 28m long and 17m wide!

The modular nature of the LS-77 OptiArray® system allows AMR’s setup to be scaled to almost any size listening room. As the numbers of speaker pairs are increased in the Opti-Array configuration, the power handling and SPL capability increase ever more dramatically over a single pair of LS-77s.

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