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LS-77 Reference Class Professional Monitor
Full Frequency RangeDesign® (FFRD)

After 3 years of research and development, the LS-77 is based on AMR’s in-house developed Full Frequency Range Design (FFRD). FFRD truly extends the low frequency extension down to 26Hz and the treble response up to 40kHz, which is previously unimaginable in a 2-way bookshelf speaker design.

Figure 1 - Conventional 2-way Monitor (red) compared to LS-77 with FFRD (blue) LS77

Aerospace grade Magnesium-Aluminium alloy Enclosure

LS77’s front panel is sculptured from a 25mm (1”) thick aerospace grade Magnesium-Aluminium alloy billet, the rest of the cabinet use 10mm thick Magnesium-Aluminium alloy billets.

The LS-77 Magnesium-Aluminium alloy cabinet is 8 times stronger and hence cut the cabinet coloration by 8 times compare to the normal MDF cabinets.  Further, the sound loss from the cabinet is 1000 times less.  As a result, LS-77 delivers  extraordinary clarity and transparency that is unprecedented.
Custom Made Drivers - Isoplanar Tweeter
The LS-77 employs a custom-made Isoplaner tweeter, which applies a force uniformly across the whole radiating surface and completely eliminates the breakup resonances found in all cone, dome or ring radiator drivers.

The Isoplaner tweeter also has a radiating surface equivalent to 5 x 28mm dome tweeters, which result in completely unrestricted dynamic levels with remarkably low distortion levels, even better than those of the best dome tweeters available.

Figure 2 - High Frequency Driver Structure Comparison

Custom Made Drivers - 10” Low Frequency Driver

The LS-77’s 10” driver has an exceptionally large radiating surface area. This together with its 28mm displacement provides a low-frequency output capability that is equivalent to six 6” HiFi low frequency drivers. Hence, the LS-77 can produce exceptional deep bass, incredibly clean and clear to a thunderous sound level.

Figure 3 - Low Frequency Driver Structure Comparison

100mm Voice Coil

The LS-77’s 10” driver uses a unique extra large 4" voice coil, allowing the use of a cone structure with the rigidity and low weight of an excellent 5” or 6” bass/midrange driver. As a result, the LS-77 has the same speed, midrange clarity and articulation of an excellent small monitor.

Figure 4 - Driver Frequency Response Comparison

Inverted Magnet System

The LS-77's unique magnet system places the magnets inside the voice coil. This vastly reduces eddy current induced distortions and power compression. At rated input power, the LS-77 exhibits as much as 6dB less power compression when compared to conventional HiFi speakers, which means the LS-77 only requires 25W instead of 100W to drive to the same sound level as conventional high-end speakers during passages of music climax.

The OptiSlope is a unique and highly specifically crossover developed by AMR’s in-house filter calculation and optimisation software. Compared to 1st Order Filters commonly found in many high-end speakers, the OptiSlope cuts the interference between the drivers by 93%.

Figure 5 - Comparison between a 1st order filter and AMR's OptiSlope® Filter


LS-77’s OptiPort design, made from solid Magnesium Aluminium alloy, completely eliminates the usual shortcomings of (i) traditional reflex port designs, which cannot be tuned sufficiently low to extend the bass response and (ii) transmission line designs, where the resonances of the transmission line structure will unavoidably muddle the upper bass frequencies.


For every speaker and crossover design, there will be a single spot in the listen room which the speaker sounds the best. In order to provide a much wider optimum listening area, both the LS-77’s high and low frequency can be fully adjusted from one extreme to another: close to walls vs. free field placement, small room vs. large lounge etc. Above and beyond the role


The unique LS-77 OptiGuide is an unique design using curvilinear cast Magnesium Aluminium alloy waveguide. The OptiGuide equalises the difference between on and off axis response by mechanical means. It focuses all the sound across an identical radiation pattern for the widest range of frequencies and also matches up with the off-axis response of the low frequency driver. As a result, LS-77 may use its OptiSlope crossover to linearise the high frequency response for both on and off axis and reach a performance which before could only be achieved by dedicated super-tweeters.

OptiArray® scalable acoustic system

Above and beyond the role of an exceptional quality midfield monitor, the AMR LS-77 was designed to form the main element of the AMR OptiArray® scalable, modular loudspeaker system. 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 30m2, while a dual-pair system will cover up to 60m2, finally up to 16 pairs in a "Focused Dual Line Array" configuration, which is capable of covering listening spaces the size of a small concert hall (480m2).
Premium components

All premium components used were chosen after extensive evaluation, lengthy and comprehensive listening tests. These include all air-coil copper foil inductors, German metal foil crossover capacitors and FEP Teflon insulated cable with silver-plate conductors for all internal wiring.


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