Method and apparatus for adjusting a cross-over frequency of a loudspeaker

• US 9,955,261 B2
• Filed: 01/12/2017
• Issued: 04/24/2018
• Est. Priority Date: 01/13/2016
• Status: Active Grant

• Current Assignee: VLSI Solution Oy
• Original Assignee: VLSI Solution Oy
• Inventors: Ojala, Pasi, Liitola, Toni
• Primary Examiner(s): Bernardi, Brenda C
• Application Number:
  US15/404,835
• Publication Number:
  US 20170201830A1
• Time in Patent Office: 467 Days
• CPC Class Codes: H04R 2430/01 Aspects of volume control, not necessarily automatic, in sound systems
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04R 29/002 Loudspeaker arrays
• CPC Class Codes: H04R 3/04 for correcting frequency response
• CPC Class Codes: H04R 3/14 Cross-over networks
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone

Abstract

A method and apparatus for adjusting a cross-over frequency of a loudspeaker system. The loudspeaker system includes at least a first loudspeaker for frequencies below the cross-over frequency and a second loudspeaker for frequencies above the cross-over frequency. A level of the first loudspeaker is matched with the second loudspeaker using a first test signal and a room response is compensated in the loudspeaker system on the basis of the first test signal. The compensated room response is measured using a second test signal. A maximum frequency for the first loudspeaker and a minimum frequency for the second loudspeaker are determined. A cross-over frequency that results in a minimum cumulative total harmonic distortion energy at one or more sound pressure levels is searched between the minimum and maximum frequency.

Claims

1. A method for adjusting a cross-over frequency of a loudspeaker system, the loudspeaker system comprising at least a first loudspeaker for frequencies below the cross-over frequency and a second loudspeaker for frequencies above the cross-over frequency, wherein the method comprises:

matching a level of the first loudspeaker with the second loudspeaker using a first test signal;

obtaining a room response on the basis of the first test signal by;

sweeping a frequency range of the first test signal;

providing the first test signal to the first loudspeaker and the second loudspeaker to produce audible signals sweeping the frequency range;

receiving the audible signals; and

computing an estimate of summed total harmonic distortion on the basis of the received signals;

compensating the room response in the loudspeaker system;

measuring the compensated room response using a second test signal;

determining a maximum frequency for the first loudspeaker by examining a frequency response of the first loudspeaker and determining a roll-off point of the first loudspeaker;

determining a minimum frequency for the second loudspeaker by examining a frequency response of the second loudspeaker and determining a roll-off point of the second loudspeaker; and

searching a cross-over frequency between the minimum and maximum frequency that results in a minimum cumulative total harmonic distortion energy at one or more sound pressure levels by simulating a number of frequencies between the minimum and maximum frequency and measuring the cumulative total harmonic distortion energy at each of the frequencies.

2. The method according to claim 1 further comprising adjusting the frequency response of the loudspeaker system to compensate the room response.

3. The method according to claim 1, wherein the matching level comprises:

generating the first test signal;

providing the first test signal to the loudspeaker system to form a first acoustic signal;

receiving the first acoustic signal by a microphone to form a first electric response signal;

using the first electric response signal to obtain level information of the loudspeaker system; and

wherein the method further comprises adjusting the level of at least one of the first loudspeaker and the second loudspeaker.

4. The method according to claim 1, wherein the matching level comprises:

generating the first test signal;

providing the first test signal to the loudspeaker system to form a first acoustic signal;

receiving the first acoustic signal by a microphone to form a first electric response signal;

using the first electric response signal to obtain level and phase information of the loudspeaker system; and

wherein the method further comprises adjusting the level and phase of at least one of the first loudspeaker and the second loudspeaker.

5. The method according to claim 1, wherein the measuring the compensated room response comprises:

generating the second test signal;

providing the second test signal to the loudspeaker system to form a second acoustic signal;

receiving the second acoustic signal by a microphone to form a second electric response signal; and

using the second electric response signal to obtain frequency response of the loudspeaker system.

6. An apparatus configured to adjust a cross-over frequency of a loudspeaker system, the loudspeaker system comprising at least a first loudspeaker for frequencies below the cross-over frequency and a second loudspeaker for frequencies above the cross-over frequency, wherein the apparatus comprises:

a signal generator configured to generate a first test signal;

a level adjustment element configured to match a level of the first loudspeaker with the second loudspeaker by using the first test signal;

a room response analysing element configured to obtain a room response on the basis of the first test signal by;

sweeping a frequency range of the first test signal;

providing the first test signal to the first loudspeaker and the second loudspeaker to produce audible signals sweeping the frequency range;

receiving the audible signals; and

computing an estimate of summed total harmonic distortion on the basis of the received signals;

a compensating element configured to compensate the room response in the loudspeaker system on the basis of the first test signal;

wherein the signal generator is further configured to generate a second test signal; and

the room response analysing element is further configured to obtain a compensated room response using the second test signal;

wherein the apparatus further comprises;

a frequency determination element for determining a maximum frequency for the first loudspeaker and a minimum frequency for the second loudspeaker, wherein the frequency determination element is configured to;

examine a frequency response of the first loudspeaker;

examine a frequency response of the second loudspeaker;

searching a roll-off point of the first loudspeaker representing the maximum frequency;

searching a roll-off point of the second loudspeaker representing the minimum frequency;

a cross-over frequency determination element configured to find a cross-over frequency between the minimum and maximum frequency that results in a minimum cumulative total harmonic distortion energy at one or more sound pressure levels by simulating a number of frequencies between the minimum and maximum frequency and measuring the cumulative total harmonic distortion energy at each of the frequencies.

7. The apparatus according to claim 6, wherein the apparatus is further configured to adjust the frequency response of the loudspeaker system to compensate the room response.

8. An apparatus for adjusting a cross-over frequency of a loudspeaker system, the loudspeaker system comprising at least a first loudspeaker for frequencies below the cross-over frequency and a second loudspeaker for frequencies above the cross-over frequency, wherein the apparatus comprises:

means for matching a level of the first loudspeaker with the second loudspeaker using a first test signal configured to;

obtain a room response on the basis of the first test signal by;

sweep a frequency range of the first test signal;

provide the first test signal to the first loudspeaker and the second loudspeaker to produce audible signals sweeping the frequency range;

receive the audible signals; and

compute an estimate of summed total harmonic distortion on the basis of the received signals

means for compensating a room response in the loudspeaker system on the basis of the first test signal;

means for measuring the compensated room response using a second test signal;

means for determining a maximum frequency for the first loudspeaker by examining a frequency response of the first loudspeaker and determining a roll-off point of the first loudspeaker;

means for determining a minimum frequency for the second loudspeaker by examining a frequency response of the second loudspeaker and determining a roll-off point of the second loudspeaker; and

means for searching a cross-over frequency between the minimum and maximum frequency that results in a minimum cumulative total harmonic distortion energy at one or more sound pressure levels by simulating a number of frequencies between the minimum and maximum frequency and measuring the cumulative total harmonic distortion energy at each of the frequencies.

9. The apparatus according to claim 8, wherein the apparatus further comprises means for adjusting the frequency response of the loudspeaker system to compensate the room response.

10. The apparatus according to claim 8, wherein the means for matching the level of the first loudspeaker with the second loudspeaker comprises:

means for generating the first test signal;

means for providing the first test signal to the loudspeaker system to form a first acoustic signal;

means for receiving the first acoustic signal by a microphone to form a first electric response signal; and

means for using the first electric response signal to obtain level information of the loudspeaker system;

wherein the apparatus further comprises means for adjusting the level of at least one of the first loudspeaker and the second loudspeaker.

11. The apparatus according to claim 8, wherein the means for matching the level of the first loudspeaker with the second loudspeaker comprises:

generating the first test signal;

providing the first test signal to the loudspeaker system to form a first acoustic signal;

receiving the first acoustic signal by a microphone to form a first electric response signal; and

using the first electric response signal to obtain level and phase information of the loudspeaker system;

wherein the apparatus further comprises means for adjusting the level and phase of at least one of the first loudspeaker and the second loudspeaker.

12. The apparatus according to claim 8, wherein the means for measuring the compensated room response comprises:

means for generating the second test signal;

means for providing the second test signal to the loudspeaker system to form a second acoustic signal;

means for receiving the second acoustic signal by a microphone to form a second electric response signal; and

means for using the second electric response signal to obtain frequency response of the loudspeaker system.