Any great speaker design starts with the best drivers and the Alesis' custom drivers are exceptional. The woofer has a cast frame with an 8" Kevlar-Carbon cone and oversized magnet assembly. The Kevlar-Carbon cone has outstanding stiffness to weight ratio to minimize distortion, extend bass response and provide excellent transient response. The magnet assembly provides high linearity and good efficiency. In the 820 DSP cabinet, the woofer is flat down to 39hz (-3db, anechoically) with harmonic distortion typically below .4% above 50hz.
The tweeter is a 28mm silk dome that has a very flat frequency response with a low resonance to reduce harshness. The tweeter is ferro-fluid cooled to provide good power handling and well-behaved response. Distortion is typically below 0.3% over its operating range. The tweeters computer designed waveguide was optimized for nearfield placement but provides excellent imaging in most other placements.
Both drivers are shielded and allow the user to place the speakers within a few inches of a CRT.
Since the 820 DSP cabinet is larger than the 720 DSP, heavy bracing was included to minimize any cabinet resonances. In addition, a coating of bitumen was applied to the inner walls to further deaden the cabinet. Venting was optimized to eliminate most of the vent noise or "chuffing" that can occur at low bass frequencies.
With Alesis' custom DSP processing, the crossover for the drivers achieves a linearity that is usually unachievable in analog monitors. This allows a smooth transition of the sound between the tweeter and woofer as well as providing proper time domain coherency. In other words, the speaker is as accurate as the drivers. The DSP also allows us to smooth out the frequency response far more effectively than with analog monitors. The response is typically better than +/- 1dB between 100hz and 20Khz.
• Level Adjustment:
One cool feature of the Prolinear DSP is the level adjustment, which allows the user to calibrate the input level to match other speakers. Simply invoke it by pushing a couple of the front panel buttons and the liquid crystal display (LCD) will display the input level into the speaker. To calibrate the speaker, input a constant test signal (e.g. pink noise, white noise) and adjust the rear panel pot to the desired level.
The internal processing of the ProLinear DSP provides external RS-232 serial ports that allow the user to connect the speaker to a PC or other speaker in a daisy chain (with the included serial cables). The functions that can be controlled through the serial port include setting of the 4 parametric bands, level control and selection of the 16 stored programs. Via a single PC, any number of speakers may be controlled. Each speaker has a channel ID number (from 1 to 16). Any speaker with the same ID will be controlled at the same time. This means that you can have 16 speakers addressed individually, or an unlimited number controlled the same.
The ProLinear is bi-amplified with typically 80 watts for the woofer and 40 watts for the tweeter. (In actuality, the woofer and tweeter are both powered at 80 watts, but because of the higher efficiency and lower power content to the tweeter, only about 40 watts is needed to match the 80 watts to the woofer.) The amplifiers are low distortion, wide band devices that are self-protected to prevent damage to the drivers. Inputs are either analog XLR or " TRS, so digital mixers and sources are not required. The power supply is a high efficiency switching supply used to provide optimal power at a low weight, as well as being usable over a wide range of AC voltages without reconfiguring the speaker.
The front panel/display of the speaker allows the user to control all the functions of the speaker if a PC is not available. Multiple speakers can also be controlled from a single speaker. The LCD provides a readout of all parameters and flashes red to indicate that the speaker is being overdriven.
Nominal input level: +4dBu (-15dBFS). Maximum input level: +20dBu (7.0 Vrms)
Input impedance: 10k?
Sound Pressure Level (SPL): 113db at 1 meter at max input below clipping.
Low Frequency (LF) power: 80 watts RMS, 120 watts peak.
High Frequency (HF) power: 40 watts RMS typical, 120 watts peak. Frequency response: 50hz - 20kHz +/- 1.5dB. Bass level -3dB @ 39hz typical,
Signal To Noise ratio: > 90 dB A-weighted, Analog In to Analog Out,
• Power Requirements:
Input voltage: 100v - 230v
Input frequency: 47 - 63 Hz
Power consumption: 20 W (idle)
130 W (typical, at maximum volume)
• Environmental Requirements:
Temperature range: 0-40 degrees C. Relative humidity (non-condensing): 30-85%.
• Cabling Requirements:
Mixer to Speaker: Balanced or unbalanced, shielded; XLR or " TRS connector.
Speaker to PC: Standard 9-pin, RS-232 serial cable (male-female).
Speaker to Speaker: Standard 9-pin, RS-232 serial cable (male-female).
Size (HxWxD): 17" x 11" x 13.5" (440mm x 280mm x 345mm)
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