View source for Auto EQ and the L1

'''Q:''' I have been looking at a device called an Ultracurve, which is supposed to help get better sound.  How does that work with the L1?

'''A:''' I used to use an (older) Ultracurve with a conventional set of speakers (pre-L1 days) ... both with an "installed" system and with a "transportable" system.  I've also used a combination of an Ultracurve (Auto EQ) along with a "feedback destroyer" (automatically creating notch filters).

I have not had an occasion since use the L1's where I wanted to break out the Ultracurve -- especially since having the T1 available to create a notch filter when necessary.

The idea behind an auto-EQ is to "normalize", or compensate, for the idiosyncrasies of BOTH the room and the audio system in order to create an overall "flat" ''(equal)'' response across the frequency range.  This is typically done by using a high-quality "reference" mic, feeding in pink noise ''(which has equal power at all frequencies)'' and measuring how the speakers, amps, and the room emphasize or reduce various frequencies ... and then creating a "mirror image" of that response to  give ''(in theory)'' an overall audio result which is "flat".

This can work o.k., but is fraught with simplifying assumptions which can result in less-than-stellar results.  Here are some of them:

1. When you try to create a 'flat' EQ, you may be striving to eliminate the "good" acoustics of a particular room as well as the "bad".  Even the greatest concerts hall are not "flat" in their "room EQ" ... that is part of what gives them their "character", just as each person's voice has it's own distinctive character.

2. The "acoustic response" of a room changes as a result of a number of factors:

a) the overall volume at which the "reference" was taken.

b) the amount of people in the room ''(this "referencing" of EQ is rarely done with an audience, because it can be most irritating!)'' -- although some more sophisticated systems have attempted to do the same with subtle "chirps" rather than simple pink noise while an audience is present.  For example, in many rooms the "empty of people" room response may sound a bit "too bright", but once it is filled with an audience the sound can be "just right".

c) temperature and humidity changes.

d) placement of speakers and mics.  With "installed" audio systems, the speaker placement doesn't change, but variations in location of mics and speakers can be terribly significant.

3. The audio components may not be adequate to truly compensate for the "bad" characteristics of the room, which can lead to distortion or other generally weird effects.

Now, with L1 Systems as your "audio source", one of the major "variables" -- that of the speaker system -- has been already "tuned" to give a consistent, uniform sound.  All that ''(should be)'' left is the response of the room itself -- and I've not felt I needed to compensate for that room EQ in most cases.

I will say that for an INSTALLED system I would include a multi-band EQ and do some amount of "room EQ" ''(even using MA12's, which are sonically similar to L1's)'', although usually not for the purpose of making the room EQ "flat", but simply to minimize some of the narrow "problem frequencies" inherent in the room.


All that to say:

I've tried an Ultracurve with an L1, but didn't think it added enough value to be worth the bother.



See original discussion at: [http://bose.infopop.cc/eve/forums/a/tpc/f/6806048934/m/9311004063 Auto EQ at the Gig]

See also these wikipedia articles:

[http://en.wikipedia.org/wiki/Equalization#Graphic_equalizer Graphic Equalizer]

[http://en.wikipedia.org/wiki/Sound_reinforcement_system#System_testing Sound Reinforcement Systems]

[http://en.wikipedia.org/wiki/Room_modes Room Modes]