Nexo PS 8 User Manual

Also see for PS10: User manual User manual Quick start guide

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Nexo PS 8 User Manual Manual pdf 12 page image

Page 12/82 A MPLIFIER S ELECTION FOR USE WITH PS-S ERIES3 AMPLIFIER S ELECTION FOR USE WITH PS-SERIESNEXO recommends high power amplifiers in all cases. Budget constraints are the only reason to selectlower power amplifiers. A lower power amplifier will not reduce the chances of driver damage due toover-excursion, and may actually increase the risk of thermal damage due to sustained clipping. If anincident occurs on an installation without protection, the fact that amplifiers only generating half theirrated output power (-3dB) are used will not change anything in respect of possible damage. This is dueto the fact that the RMS power handling of the weakest component in the system is always 6 to 10 dBlower than the amplifier rating.3.1 PS and LS recommended amplificationNexo recommends amplifiers in agreement with table below:RecommendedAmplifier#Channel 1LF in Active Mode orLF+HF in Passive ModeChannel 2HF in Active ModeLS400 300 to 700 W / 6 OhmsPS8 200 to 500 W / 8 OhmsLS600 1000 to 2000 W / 8 OhmsPS10R2 500 to 1250 W / 8 OhmsPS15R2 Passive Mode 1000 to 2000 W / 8 OhmsPS15R2 Active Mode 1000 to 2000 W / 8 Ohms 250 to 500 W / 16 Ohms3.1.1 Current ratingIt is very important that the amplifier behaves correctly under low load conditions. A speaker system isreactive by nature: on transient signals like music it will require four to ten times more instantaneouscurrent than its nominal impedance would indicate. Amplifiers are generally specified by continuousRMS power into resistive loads, however the only useful information about current capacity is thespecification into a 2 Ohm load. It is possible to perform an amplifier listening test by loading the ampswith twice the number of cabinets considered for the application (2 speakers per channel instead of one,4 instead of 2) and running the amps up to the onset of clipping. If the signal does not noticeablydeteriorate, the amplifier is well adapted (overheating after approximately ten minutes is normal butthermal protection must not operate too quickly after starting this test).3.1.2 Amplifier settingsGain valueGain is the key to correct alignment of the system. It is especially important to know the gain of allamplifiers used in your set-up. The tolerance should be about ±0.5 dB. In practice this can be difficult toachieve because:• Some amplifier brands have an identical input sensitivity for models of different power rating (thisinfers a different voltage gain for each model). For example, a range of amplifiers with differentpower outputs, all having a published input sensitivity of 775mV/0dBm or 1.55V/+6dBm, will havea wide range of actual gains – the higher the power, the greater the gain.• Various other brands may offer constant gain but only within a given product range, for examplethey may fit fixed input sensitivity only on their semi-professional amps.• Even if a manufacturer applies the constant gain rule to all models, the value selected will notnecessarily be the same as that chosen by other manufacturers.