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DM-7b, Dreams Wideband AMT Driver



© Advance features of the DM-7b AMT Driver

         The modular DM-7b Dreams tweeter is a compact, integrated, wideband AMT audio driver newly created by Mark & Daniel® using the latest, most advanced technology and craftsmanship. The AMT (air-motion transformer) configuration, in spite of its production difficulty, has proven to be the most ideal true sound reproducer compare to conventional tweeters, and based on the successful development to the DM-6 and DM-7 series AMT drivers; M&D has therefore built a solid foundation to create a second generation (the MK-II models) for our hi-end speaker systems.

         When the earlier Dreams AMT drivers were utilized for M&Ds speaker systems, a dedicated sound chamber and fine-tuning equalization crossover network were required in order to achieve optimized wideband reproduction; differing from our previous DM-1 through DM-5 models, this new generation DM-7b AMT driver has been designed for the most compact installation, featuring a 5-octave wideband sound module responsible for frequencies from 700Hz up to 22KHz within its compact dimensions, without the need for an extra chamber and can compliment the speaker system by a simpler crossover network.

         DM-7b is a high quality, integrated AMT module. All the details of its construction and materials have been reviewed and significantly improved over M&Ds previous models. In respect to its performance, the innovated DM-7b tweeter is reliable and durable, capable of sustaining high dynamic sound output to produce true wideband sound reproduction.

         The compact yet powerful DM-7b driver has a sealed, air-tight structure so it can be easily mounted on the speaker panel without being affected by the influence of deep, powerful bass output during audio reproduction. Its impedance characteristics are totally resistive and flat from DC up to 30KHz range that simplifies the crossover network design. The inner wiring of the driver is also concise, only banana post connections are required at the tweeter. 



©  How does DM-7b Work

         Most commonly used by hi-fi industry today for making the ribbon tweeters (also used by M&Ds pleated Dreams AMT drivers), the etched aluminum circuitry is laid on a very thin 0.025mm (1.0 mil) polyimide (also known as Kapton) film as the substrate to constitute the voice diaphragm; due to the outstanding characteristics of polyimide such as light weight, high temperature-resistance (180-250oC), excellent durability, and so forth.
         However, from M&Ds own study, we found that the attached mass and hardness of the present polyimide substrate could still amount to certain obstruction for perfect diaphragm movements during sound reproduction. In order to further cut down the substrate moving mass and enhance the pleated diaphragm compliance, after long research, M&D has developed the unique technique and craft to further reduce the substrate to only one-half of its original thickness. This successful development allows us to apply the rare, super-thin 0.0125mm (0.5 mil) polyimide material in formulating our new Dreams AMT voice diaphragms.
         Not only this 0.5 mil super-thin polyimide itself incurs much expensive production cost, the higher level of skilled craftsmanship throughout the entire manufacturing process of the Dreams AMT diaphragm are painstakingly time consuming. However, this innovative breakthrough has been proven worthwhile; the newly developed, DM-7b wideband AMT driver has significant improvement transient response, and sound quality characteristics.
         Constructed with 36 micro elements, forming a 15 micron (0.0006) aluminum ribbon in thickness, attached onto the super-thin 0.5 mil polyimide diaphragm and pleated into shape, then meticulously fixed onto the acoustic frame; this symmetrical ribbon array directly pumps out (or draws in) a sufficient quantity of air driven by the musical current signal, responding to high dynamic, acoustic power, pushing wideband frequencies down to 700Hz and the Dreams AMT DM-7b driver yields a high frequency and high transient response up to 22 KHz.

         This integrated DM-7b AMT tweeter is therefore, a true over 5-octave wideband driver responsible from 700Hz to 22 KHz, and has a large composite diaphragm that constitutes over 38 times the driving surface of the conventional 1 dome tweeter folded into this slim-shaped AMT sound reproducer. This unique driver is therefore, allowing for high power handling, high SPL output with low FMD pollution throughout the entire operating bandwidth, under such a compact size.
         DM-7bs diaphragm is sunk into an extremely strong magnetic loop with large NdFeB magnets creating a sophisticated and expensive structure to ensure proper operation of the driver, thereby yielding an outstanding 30 degree horizontal dispersion characteristic within a 700Hz to 10KHz (-5dB) bandwidth. Vertical dispersion is low, effectively avoiding undesirable reflections from ceilings and floors for better clarity and imaging under all listening conditions; this sharp vertical dispersion characteristic may also be beneficial for building the line-array tower to cut down sound interference between the drivers.
         DM-7b has a typical DC impedance at 4.0 Ohms (0.2 Ohms) and is completely coherently resistive throughout the entire audio band, without resonance, and without inductive or capacitive contributes. This perfect impedance characteristic provides a highly stable operative platform for the power amplifier; it also facilitates much simpler and more efficient crossover network design. DM-7b has a very steep roll-off slope at the low frequency end. While input signals are lower than 700Hz it will not cause distortions nor click noise; it simply does not respond in this fashion due to its mechanical attenuation.
         Each compact-sized DM-7b sound module measures 120mm x (D) 36mm. Its iron frame is rigid and heavy-duty in construction with each module weighing up to 960g (2.1 lb); the DM-7b has an average efficiency around 85dB/2.83V/1m; for 2-way speaker, set a crossover point not to lower than 700Hz is recommended. 



         Different from an assembly line produced product, the manufacturing process of the Dreams AMT module is both time and labor intensive, requiring extensive hours and hours to assemble and test. Rather than just a simple, mass-produced, assembly line manufactured tweeter, the Dreams AMT driver requires utmost dedication in both precision technology and artistic craftsmanship throughout its creation.


© General Specifications

Model Name: DM-7b Dreams AMT Driver
Frequency Response700Hz - 22KHz
DC Impedance: 4.0 Ohms (0.2 Ohms)
Average Efficiency: 85dB/2.83V/1m
Matching Power Amplifier: 100 Watts, continuous
Front Panel Options- mirror shine Stainless Steel (in Silver) 
                                  - French made Gravoply® (in Black)
Connection: by the Banana Posts
Overall Size: 120mm x (D) 36mm
Net Weight: 960g (2.1 lb)






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