Automatic loudspeaker equalizer

A method for generating a set of second order filters to equalize a loudspeaker, comprising the steps of:

• providing first digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeaker;
• providing second digital data for an actual response curve of sound level versus frequency for said loudspeaker;
• comparing said first digital data to said second digital data and determining whether said actual response curve is within said tolerance range;
• and
• if said actual response curve is not within said tolerance range, generating a set of filters to equalize said loudspeaker by performing the following optimizing steps iteratively,
• digitally processing said second digital data to determine an nth set of initial parameters for an nth peak in said actual response curve where said actual response curve is not within said tolerance range, including a frequency, and amplitude and a bandwidth for said peak, where n is the number of an iteration of said optimizing steps,
• digitally generating a compensating nth filter from said nth set of initial parameters,
• applying said nth filter to said second digital data and modifying said nth set of initial parameters to determine an nth set of optimum parameters for said compensating nth filter, to generate third digital data for an nth interim compensated response curve of sound level versus frequency,
• processing said third digital data to determine whether said nth interim compensated response curve is within said tolerance range,
• if said nth interim compensated response curve is not within said tolerance range, performing another iteration of said optimizing steps until said interim compensated response curve is within said tolerance range or a predetermined limit on the number of filters has been reached, whichever occurs first.

A method for generating filters for equalizing a loudspeaker, comprising the steps of:

• providing first digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeaker;
• providing second digital data for an actual response curve of sound level versus frequency for said loudspeaker;
• comparing said first digital data to said second digital data and determining whether said actual response curve is within said tolerance range;
• and
• if said actual response curve is not within said tolerance range, generating a set of compensating filters by performing the following single filter optimizing steps iteratively,
• digitally processing said second digital data to determine an nth set of initial parameters for an nth peak in said actual response curve where said actual response curve is not within said tolerance range, including a frequency, an amplitude and a bandwidth for said peak, where n is the number of an iteration of said optimizing steps,
• digitally generating a compensating nth filter from said nth set of initial parameters,
• applying said nth filter to said second digital data and modifying said nth set of initial parameters to determine an nth set of optimum parameters for said nth filter, to generate third digital data for an nth interim compensated response curve of sound level versus frequency;
• if n>1, performing the following joint filter optimizing steps iteratively and cyclically,
• generating fourth digital data for interim computed response curves in which for each joint filter optimizing iteration one of said n filters is absent, and then performing said single filter optimization steps utilizing said fourth digital data to generate fifth digital data for an updated interim response curve,
• digitally processing said fifth digital data to determine whether the most recent of said joint filter optimizing iterations has resulted in a change in said updated interim response curve greater than a predetermined amount of change, and if so continuing to perform said joint filter optimizing steps;
• processing said fifth digital data to determine whether said nth interim compensated response curve is within said tolerance range,
• and if not,
• performing another iteration of the foregoing steps until said interim compensated response curve is within said tolerance range or a predetermined limit on the number of filters has been reached, whichever occurs first,
• but if so, ceasing performance of further iterations.

A method for generating filters for equalizing a loudspeaker, comprising the steps of:

• providing a source of first audio digital data;
• providing a digital audio processing unit for processing said first audio digital data and providing processed audio digital data, including applying digital audio filters for equalizing said loudspeaker characterized by coefficients in algorithms applied to said first audio digital data to effect said digital audio filters;
• providing a digital to analog converter for converting said processed audio digital data to an analog audio signal for provision to said loudspeaker;
• providing a sound field measuring device in the vicinity of said loudspeaker to generate second audio digital data representing sound produced by said loudspeaker;
• providing a digital computer connected to receive said second audio digital data, and programming said digital computer to determine said coefficients for digital filters for equalizing a loudspeaker and provide said coefficients to said digital audio processing unit by
• providing third digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeaker;
• providing said second digital data, wherein said second digital data represents an actual response curve of sound level versus frequency for said loudspeaker;
• comparing said third digital data to said second digital data and determining whether said actual response curve is within said tolerance range;
• and
• if said actual response curve is not within said tolerance range,
• iteratively generating digital audio filters by iteratively generating coefficients for said digital audio filters, applying said digital audio filters determined by said coefficients to said second digital data to generate fourth digital data for a compensated response curve, and
• automatically optimizing said coefficients until said compensated response curve is within said tolerance range or a predetermined limit on the number of digital audio filters has been reached, whichever occurs first.

An apparatus for generating filters for equalizing a loudspeaker, comprising:

• a source of first audio digital data;
• a digital audio processing unit for processing said first audio digital data and providing processed audio digital data, including applying digital audio filters for equalizing said loudspeaker characterized by coefficients in algorithms applied to said first audio digital data to effect said digital audio filters;
• a digital to analog converter for converting said processed audio digital data to an analog audio signal for provision to said loudspeaker;
• a sound field measuring device in the vicinity of said loudspeaker to generate second audio digital data representing sound produced by said loudspeaker;
• a digital computer connected to receive said second audio digital data, and programmed to determine said coefficients for digital filters for equalizing a loudspeaker and provide said coefficients to said digital audio processing unit, said digital computer being programmed to determine said coefficients by
• providing third digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeaker;
• providing said second digital data, wherein said second digital data represents an actual response curve of sound level versus frequency for said loudspeaker;
• comparing said third digital data to said second digital data and determining whether said actual response curve is within said tolerance range;
• and
• if said actual response curve is not within said tolerance range,
• iteratively generating digital audio filters by iteratively generating coefficients for digital audio filters, applying digital audio filters determined by said coefficients to said second digital data to generate fourth digital data for a compensated response curve, and
• automatically optimizing said coefficients until said compensated response curve is within said tolerance range or a predetermined limit on the number of digital audio filters has been reached, whichever occurs first.

A method for generating digital filters for equalizing a loudspeaker, comprising the steps of:

• providing first digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeaker;
• providing second digital data for a first actual response curve of sound level versus frequency for said loudspeaker;
• comparing said first digital data to said second digital data and determining whether said first actual response curve is within said tolerance range;
• and
• if said first actual response curve is not within said tolerance range,
• iteratively generating digital audio filters to compensate said actual response curve,
• applying said digital audio filters to said first digital data to generate third digital data, converting said third digital data to an analog signal and providing said analog signal to said loudspeaker,
• generating fourth digital data for a second actual response curve of sound level from said analog signal versus frequency for said loudspeaker;
• comparing said first digital data to said fourth digital data and determining whether said second actual response curve is within said tolerance range;
• and
• automatically optimizing the frequency, amplitude and bandwidth of said digital audio filters until said second actual response curve is within said tolerance range or a predetermined limit on the number of digital audio filters has been reached, whichever occurs first.

A method for generating total log-integral metric digital data for characterizing the perceived performance of a loudspeaker, comprising the steps of:

• providing first digital data for N samples for a desired response curve of sound level versus frequency for said loudspeaker;
• providing second digital data for N samples for an actual response curve of sound level versus frequency for said loudspeaker;
• and
• generating total log-integral metric data according to the formula:
• M = ∑ i = 1 N - 1 ⁢ ⁢ log 10 ⁡ ( f i + 1 f i ) ⁡ [ [LeftBracketingBar] S ⁡ ( f i ) d ⁢ ⁢ B - D ⁡ ( f i ) d ⁢ ⁢ B [RightBracketingBar] + [LeftBracketingBar] S ⁡ ( f i + 1 ) d ⁢ ⁢ B - D ⁡ ( f i + 1 ) d ⁢ ⁢ B [RightBracketingBar] 2 ]
• where:
• M is the total log-integral metric,
• f is the frequency,
• D is the first digital data,
• S is the second digital data, and
• N is the number of samples of first digital data and of second digital data.

A method for generating digital filters for equalizing a plurality of loudspeakers, comprising the steps of:

• providing first digital data for a tolerance range for a target response curve of sound level versus frequency for said loudspeakers;
• providing second digital data for an actual response curve of sound level versus frequency for said loudspeakers;
• comparing said first digital data to said second digital data and determining whether said actual response curve is within said tolerance range;
• and
• if said actual response curve is not within said tolerance range,
• iteratively generating digital audio filters,
• applying said digital audio filters to said second digital data to generate third digital data for a compensated response curve, and automatically optimizing the frequency, amplitude and bandwidth of said digital audio filters until said compensated response curve is within said tolerance range or a predetermined limit on the number of digital audio filters has been reached, whichever occurs first.