Many of our sound reinforcement installations contain a High Definition 31 band equalizer for improving system gain before feedback as well as improving the general intelligibility of the sound. With the assistance of our Test Equipment we locate and attenuate bands of frequencies that are prone to feedback and excite the acoustic environment with boomy unwanted sounds.  Below is the description of a good quality equalizer.  

ART HD 15, HD 31 High Definition Graphic EQ's (This is an older EQ but the basics are the same for most EQs)

The HD-15 (stereo 2/3 octave) and HD-31 (1/3 octave) High Definition equalizers are professional quality, low noise units designed for use in sophisticated recording and sound reinforcement applications. Reliable and rugged units, the HD series is the product of 10 years of research and development.

The HD series offers the best in electronic components housed in an 18 gauge steel chassis for the ultimate in shielding and component protection. While exceptional design and automated assembly keep these equalizers competitively priced, A R T always offers the features one would expect in a professional unit. Faders are center-detented, sixty millimeter, high resolution type. All faders are equipped with large fader knobs. Signal Present/Clip, Power and Active/Bypass status LED's are employed for user c onvenience.

The most innovative feature of the HD series equalizers is perhaps the accuracy of the filter networks. Featuring constant Q active combining circuitry, there is virtually no center-point frequency drift regardless of the position of adjacent filter settings. The HD series offers a new level of precision equalization and may be the most transparent and accurate equalizers available.

From major rock & roll albums and tours to church installations, A R T HD Series equalizers have become the industry standard.

Specifications:

Input:
  Impedance    			10K ohm (balanced)
  Max. Input Level		(+)24 dBm
Output:
  Impedance			100 ohm (balanced)
Max. Output Level:
  Balanced 600 ohm		(+)23dBm
  Balanced no load		(+)27dBm
  Unbalanced			(+)23dBm
  Dynamic Range			118dB
Signal/Noise Ratio:
  (R.E.+20dBm)			115dB
  Equivalent Input Noise	(-)95dBm
  THD..005% 20-20kHz (+)15dBm Frequency Response: 10-50kHz. (+)0. -5 dB 02-153kHz (-)3dB 

Wayne and I are putting together some famous war stories about coming across the dreaded "smiley curve" equalizer setting. This is when the equalizer is set so the extreme frequencies are boosted and the mid range frequencies are attenutated. The equalizer controls look like a smile. So stay tuned and check back.

Gabriel Stores

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