Jamo C 809 Catalog - Page 7

Jamo Tech platforms Jamo C 80 page 0 Motional Feedback (MFB) C 80 SUB features a Motional Feedback circuit. When a large woofer has been abruptly driven by a strong sonic impulse such as an explosion or a timpani, the woofer continues moving after the impulse stops. The MFB circuit compares the impulse to be reproduced with the actual movement of the woofer. If the woofer moves unnaturally in relation to the input signal, the MFB circuit corrects the error before it becomes audible. Furthermore, the MFB makes it possible to equalize the subwoofer to go deeper without losing any precision. The result is incredibly accurate, deep bass, full of punch and dynamics. Motional Feedback (MFB) Impulse response [V] 0 Time - msec.  Without MFB With MFB Boundary Gain Compensation The Boundary Gain Compensation filter in C 80 SUB compensates for the room influence at low frequencies, as any room amplifies the lowest frequencies. The magnitude of the room's amplification depends on the room size and where the sub is positioned in the room - normally it increases the closer the sub get to a wall. This can result in too high a bass level from approx. 60Hz and increasing downwards - in the range between 20 - ­30Hz it peaks up to 5­ - 10dB in an average room! At first this could sound really impressive, but the sound quickly begins to sound 'boomy', especially when listening to music, and rather annoying. So the Boundary Gain Compensation ensures a very linear in­-room bass response and gives you more flexibility when it comes to placement and choosing your favourite listening position. Boundary Gain Compensation SPL/Volts [0.33 oct]  Off On 10.0 100.0 Frequenzy ]Hz] Active Impedance Control (AIC) All C 80 mid/woofers feature Active Impedance Control (AIC), an innovative extension of existing techniques to reduce distortion in electrodynamic loudspeaker drivers. The AIC makes the impedance more linear in the mid and high frequency range. AIC also increases the sensitivity and total SPL in the upper range of the driver. AIC - Active Impedance Control: Impedance [Ohm] 30  driver with AIC 25 driver without AIC 20 15 10 5 0 200 500 1k 2k 2k 10k 20k Frequenzy ]Hz] The effect of AIC is a clearer midrange with a markedly reduced 'roughness', especially noticeable on vocal reproduction. In figures, this amounts to a reduction of third-order harmonic distortion of around 6dB (ie a 50% reduction). Harmonic distortion [dB] -35 -40 -45 -50 -55 -60 -65 200  driver with AIC 500 1k driver without AIC 2k Frequenzy ]Hz] When a voice coil is moving in and out of a magnet gap, it changes induction. When the coil moves inward, the induction increases and vice versa. This causes the current from the amplifier to be modulated, creating very audible distortion. Furthermore the current flowing in the voice coil modulates the magnetization of the magnet assembly which also causes distortion of the current. By using an extra coil, placed inside the voice coil with opposite polarity to the voice-coil winding, the inductance variation and the flux modulation can be significantly counteracted. Compared to the conventional conductive rings in a magnet system AIC has the advantage that it is significantly better at higher frequencies i.e. in the midrange (on voices) where distortion is most audible to the human ear.