Abbingdon Music Research LS-77 owner manual

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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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Contents LS-77 Reference Class Professional Monitor Loudspeakers Page Page Running-In PrecautionsContents Page Front Panel of the LS-77 UnpackingPlease check that all contents are present LS-77 Front Fascia Component OverviewContact with the chassis Connecting the loudspeakers SetupUsing AMRs OptiLink Speakon Cable Speaker R Speaker L Using Binding Posts Speaker Cable Stereo Amplifier Interconnect Cable Multi-channel set up Connecting the amplifierChoice of loudspeaker cable Symmetry and room modes PositioningDistance between the loudspeakers Distance to back and side walls Distance to the loudspeakersLevelling/Speaker Support Room and furniture influence Loudspeaker Toe-inCare & Maintainance Care and maintenanceRunning-in the loudspeakers Power rating LS- 77 Technical Features Troubleshooting Guide TroubleshootingSpecifications Table SpecificationsAppendix a Adjustment of tonal balan ce HF Level Placement Suggestions HF Level R1 Placement Appendix B Abbingdon Acoustic Setup Regime Page ~100″/254cm ~115 ″/290cm Page Page Appendix C Biamplifying the LS-77 LS-77 Speaker R Speaker L Speaker Cable AM-77 Control Center Edition CCE Appendix D The AMR Active SystemLine Level Connection Setting up the AMR Active SystemSpeaker Connection Scenario Testing and Troubleshooting the AMR Active System LS-77 Speaker L AMR Active System Configuration DiagramIntroducing AMRs OptiArray scalable acoustic system Appendix E LS-77 in OptiArray configurationsPage AMR recommends the following OptiArray Setups Epsilon/Zeta Iota/Zappa Omicron/Sigma Epsilon/Zeta System wiring Reverberation time Appendix G Acoustics Background In formationAcoustics Good acousticsPage Membrane absorbers DiffusersAbsorption or Diffusion ? AbsorbersPorous absorbers Standing WavesRoom modes
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