Velodyne Acoustics HGS-12X Distortion in Loudspeakers, Volume control, Phase adjustment - 0/180

Volume control

This control allows you to balance the output from the subwoofer to the main speakers/amplifier in your system. This control should be set to achieve similar output level from both the main speakers and subwoofer when listening to music. A good starting point for the volume control is 4 or 5 dots from minimum.

Low-pass crossover - 40 to 120Hz

The line-level inputs sum the left and right channels together, with the resulting signal passing through an adjustable low-pass crossover before being amplified. The crossover control allows you to adjust the upper limit of the subwoofer's frequency response from 40 to 120Hz. The subwoofer's output will be reduced above the frequency you set this control to. You should set the crossover frequency to obtain a smooth and seamless transition from the subwoofer to the main speakers in your system. If your mainspeakersaresmallerunitswithlimitedlowfrequencyoutput,youmay wish to choose a higher frequency (such as 100-120Hz) than you would with larger speakers which have greater low frequency output. With larger speakers, you might start with this control set lower, such as 80Hz.

A bypass switch is also provided if you wish to use an external crossover.

If you are not using an external crossover, we recommend that you use the one provided within the unit for optimum performance!

Phase adjustment - 0°/180°

This control allows you the "reverse" the phase of the subwoofer's output signal 180° to correct for any possible mismatch and resulting cancellation between the subwooferandyourmainspeakers/amplifier.Toadjust,simplylistentothesystem with music playing. Then move the switch from one position to the other and listen forachangeinlowfrequencyoutput.Thecorrectpositionwillhaveagreateramount of apparent low frequency output.

Subsonic - 20Hz/35Hz

This adjustment alters the low frequency limit of the subwoofer. In certain movie theater installations which suggest that the extreme low bass be limited, move the switch position to 35Hz and the response will be attenuated below this frequency.

The unit is protected against:

1)Overdriving the speaker or amplifier.

2)Overheatingtheamplifier.

3)Excessive drop in power line voltage.

The first type of protection circuitry which prevents overdriving of the speaker or amplifier operates constantly without being audible under most situations. Insome extreme situations (sustained high output levels such as pro sound usage), the unit may shut down momentarily. This indicates operation of the thermal or undervoltage protection circuitry. If this should happen,youshouldreducethevolumesettingorshuttheunitoffuntilnormal operating conditions return. You may also want to plug the unit into a differentwalloutlet,asdroppingpowerlinevoltagewillbemostnoticeable under strenuous conditions.

Distortion in Loudspeakers

Nonlineardistortionisaproblemwhichplaguesallspeakers.Thisparticular type of distortion is a common problem in subwoofers, which must move large amounts of air to produce adequate levels of deep bass. Nonlinear distortion is defined as any form of distortion that moves energy from one portion of the audio frequency spectrum to another. When a single tone is applied to a nonlinear system, the result is harmonic distortion. In which some of the energy leaves the system at multiples of the original frequency. When multiple tones are applied, intermodulation tones are produced, usually as simple combinations of the input frequencies. Generally, 3% distortion is considered a reasonable amount for speakers. This means that 3% of the total energy leaving the speaker is at frequencies other than the intendedinputsignal.

Most subwoofers on the market today however, produce much more than 3% distortion at common listening levels. Many models we have tested produce greater than 20% distortion @ 20Hz when driven to 100dB. This isatypicaloutputlevelobtainedinmanysystems,particularlyhometheater

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