CN1767696A - Method for measuring loudspeaker unit resonance frequency temperature drift characteristic during high power work - Google Patents

Abstract

This invention relates to a method for testing the temperature shift property of resonant frequencies of a loudspeaker unit working on large power, which utilizes the temperature shift formula of the resonant frequency of a loudspeaker unit working under large power and uses a lumped parameter analog circuit to describe the thermal run-away channel in the unit and gives the relation formula of a centering bearing plate surface temperature and the voice coil temperature so as to derive a formula of a resonant frequency along with the temperature variance of the voice coil and uses a conventional temperature test device and electro-voice test device to test the temperature shift property of the resonant frequency along with the variance of the centering bearing plate and the property along with the voice coil temperature variance to further predict the resonant frequency under different temperatures and the centering bearing plate surface temperatures.

Description

The loudspeaker unit resonance frequency temperature drift characteristic during high power work assay method

One, technical field

The present invention relates to detection, be used to estimate and the performance when improving the loudspeaker unit high power work loudspeaker unit resonance frequency; Especially the model formation of loudspeaker unit resonance frequency temperature drift characteristic, mensuration and prediction.

Two, background technology

＜one〉meaning of the temperature drift characteristic of loudspeaker unit resonance frequency under the measurement high power work condition

Resonance frequency is the basic parameter of loudspeaker unit, and the performance and the effect of loudspeaker unit played a decisive role.Resonance frequency is by the equivalent force and the decision of equivalent oscillating mass of loudspeaker unit vibrational system, and wherein equivalent oscillating mass approximately constant, equivalent force then can change with voice coil loudspeaker voice coil displacement, change of external conditions.Up to now, the research about the vibrational system mechanical compliance is limited to the linearity that mechanical compliance changes with the voice coil loudspeaker voice coil change in displacement more.When considering the influencing of external condition, mechanical compliance is determined jointly by centring disk and ring, it has been generally acknowledged that the coefficient of elasticity of these two is influenced by the temperature and humidity of atmosphere all, can measure under different environmental conditions.Under playback small-signal, loudspeaker unit internal temperature and ambient temperature differed very little situation, the mechanical compliance of vibrational system can be thought the value that equals to measure under the ambient temperature.But in a lot of practical application, loudspeaker unit works long hours under relatively large signal, at this moment the loudspeaker unit internal temperature raises, the centring disk coefficient of elasticity reduces, compliance increases, though ring is because less from the compliance variation far away of thermal source voice coil loudspeaker voice coil, marked change has taken place in the mechanical compliance of vibrational system, thereby causes the resonance frequency of unit that bigger skew takes place.Therefore the temperature drift characteristic of measuring loudspeaker unit resonance frequency under the high power work condition is just necessary, can be used for estimating and the performance when improving the loudspeaker unit high power work.

Existing conventional electroacoustic measurement method and instrument all do not consider not have the function of measuring the temperature drift characteristic of resonance frequency under the loudspeaker unit high power work condition yet.

＜two〉prior art or method

The research of relevant loudspeaker unit centring disk mechanical compliance, the work of having carried out mainly contains: A) Steven Hutt. " Loudspeaker Spider Linearity " (the linearity of loud speaker centring disk, the 108th [world] Audio Engineering Society conference, The 108th Convention ofthe Audio Engineering Society, Paris, 2000.Preprint 5159) compared the centring disk of several different geometries and unlike material, the fluctuating ripple that proposes the employing gradual change improves the linearity of centring disk mechanical compliance.

B) Hiroshi Watanebe. " Improvement of Suspension Linearity in Loudspeakers byMeans of Biased Suspension " (utilize the offset structure to improve the linearity of loud speaker suspension, the 79th [world] Audio Engineering Society conference, The 79th Convention ofthe Audio Engineering Society, New York, 1985.Preprint 2283) proposed in loudspeaker unit, to adopt two centring disk angle mount structures, can increase the linearity of centring disk mechanical compliance, reduce secondary, third harmonic distortion.

These work all only limit to study mechanical compliance how the to improve centring disk linearity with the voice coil loudspeaker voice coil change in displacement, and reckon without that centring disk produces the mechanical compliance variation under the high power work condition owing near air themperature raises.

C) (ambient temperature is to the influence of OEM auto loud hailer for Steven Hutt. " Ambient Temperature Influences on OEM Automotive Loudspeakers ", the 112nd [world] Audio Engineering Society conference, The112th Convention of the Audio Engineering Society, Munich, 2002.Preprint 5507) utilize Klippel distortion analyzer and insulating box to measure the influence of ambient temperature to the auto loud hailer cell parameters, having compared the cell parameters that records under the varying environment temperature, mainly is the resonance frequency of unit and the coefficient of elasticity of vibrational system (being the inverse of mechanical compliance).

This paper is considered be the temperature of loud speaker environment of living in to the loudspeaker unit Effect on Performance, and reckon without near the change that the temperature of air raises the unit performance is produced the centring disk under the high power work condition.

D) Wolfgang Klippel. " device that Dynamical Measurement of Loudspeaker Suspension Parts (dynamic measurement method of loudspeaker unit parts; the 117th [world] Audio Engineering Society conference The 117thConvention of the Audio Engineering Society; San Francisco, 2004.Preprint 6179) has proposed a kind of special use is measured the mechanical compliance of loudspeaker unit cone, centring disk and ring; Point out that the mechanical compliance that records usually is an effective mean value, approximately constant during small-signal, the centring disk mechanical compliance value during large-signal produces nonlinear change with the variation of voice coil loudspeaker voice coil displacement, also corresponding the changing of resonance frequency of this moment.

This paper has been noted that vibrational system coefficient of elasticity curve can increase or elongated generation of cell operation time " irregular variation " (Irregular Variations) with voltage, but only provide the conjecture interpretation, think to cause owing to material dilatation and reason such as aging.Content of the present invention can be made the explanation of qualitative, quantitative to above-mentioned phenomenon, and extrapolates the variation of unit resonance frequency thus.

Three, summary of the invention

The objective of the invention is to temperature drift formula according to loudspeaker unit resonance frequency under the high power work condition, utilize the temperature drift characteristic of resonance frequency under conventional temperature measuring equipment and the electroacoustic measurement Instrument measuring high power work condition, and predict the resonance frequency drift when voice coil temperature and centring disk surface temperature change in view of the above.

The inventive method is based on following mechanism: the vibrational system coefficient of elasticity of known loudspeaker unit is contributed jointly by centring disk and ring, the centring disk surface temperature near-space temperature degree of will enclosing raises and raises under the high-power condition, cause the centring disk deliquescing, compliance increases, coefficient of elasticity descends, so the coefficient of elasticity temperature drift formula of vibrational system is:

k _ms＝k _sp+k _su＝k _sp0+α _spΔT _s+k _su＝(k _sp0+k _su)+α _spΔT _s＝k _ms0+α _spΔT _s

In view of the above, unit resonance frequency with the formula that the centring disk surface temperature changes is:

$f_s=\frac{1}{2\mathrm{\&pi;}\sqrt{M_{\mathrm{ms}}{C}_{\mathrm{ms}}}}=\frac{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="k\; ms"\; filenames="A20051009451200091.png"\; state="\{\{state\}\}">k</figure-callout>}}_{\mathrm{ms}}}}{2\mathrm{\&pi;}\sqrt{M_{\mathrm{ms}}}}=\frac{\sqrt{{\mathrm{<figure-callout\; id="0"\; label="k\; ms"\; filenames="A20051009451200082.png,A20051009451200091.png"\; state="\{\{state\}\}">k</figure-callout>}}_{\mathrm{ms}}+a_{\mathrm{sp}}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T\; s"\; filenames="A20051009451200091.png"\; state="\{\{state\}\}">T</figure-callout>}}_s}}{2\mathrm{\&pi;}\sqrt{M_{\mathrm{ms}}}}={\mathrm{<figure-callout\; id="0"\; label="f\; s"\; filenames="A20051009451200082.png,A20051009451200091.png"\; state="\{\{state\}\}">f</figure-callout>}}_s\sqrt{1+{\mathrm{\&beta;}}_{\mathrm{sp}}\mathrm{\&Delta;}{T}_s}$

The object of the present invention is achieved like this: the method for measuring the temperature drift characteristic of resonance frequency under the loudspeaker unit high power work condition, temperature drift formula according to loudspeaker unit resonance frequency, temperature measuring device with routine detects the temperature drift characteristic that centring disk surface temperature and electricity consumption acoustic frequency and power measurement instrument mensuration resonance frequency change with centring disk surface and voice coil temperature, obtain the temperature drift characteristic that resonance frequency changes with voice coil temperature, and then the resonance frequency under measurable different voice coil temperature and the centring disk surface temperature.

The temperature drift formula that the loudspeaker unit resonance frequency of institute's foundation changes with above-mentioned centring disk surface temperature:

$f_s={\mathrm{<figure-callout\; id="0"\; label="f\; s"\; filenames="A20051009451200082.png,A20051009451200091.png"\; state="\{\{state\}\}">f</figure-callout>}}_s\sqrt{1+{\mathrm{\&beta;}}_{\mathrm{sp}}{\mathrm{\&Delta;T}}_s}$

Temperature measuring equipment and electroacoustic measurement apparatus measures, The Fitting Calculation with routine go out the temperature drift coefficient that resonance frequency changes with centring disk surface temperature and voice coil temperature.

And the resonance frequency that records when resetting small-signal at ambient temperature of the temperature drift coefficient that draws after utilize measuring, calculating is calculated the loudspeaker unit resonance frequency under different centring disk surface temperatures of prediction and the voice coil temperature.

Utilize infrared radiation thermometer and conventional one group of Δ T of electroacoustic measurement apparatus measures _s～f _sData, The Fitting Calculation can draw the temperature drift coefficient β that unit resonance frequency changes with the centring disk surface temperature _Sp

Set up lumped parameter analogous circuit such as Fig. 1 of loudspeaker unit internal heat dissipation path, regard centring disk and near air thereof as isothermal, so the centring disk surface temperature is only relevant with voice coil loudspeaker voice coil amplitude and speed with the ratio of voice coil temperature when inside, unit reaches heat balance:

$\frac{{\mathrm{\&Delta;T}}_s}{{\mathrm{\&Delta;T}}_c}=\frac{R_{\mathrm{ts}}\left(x\right)}{R_{\mathrm{ts}}\left(x\right)+R_{\mathrm{tc}}\left(v\right)}=\frac{R_{\mathrm{ts}1}\left(x\right)\left|\right|R_{\mathrm{ts}2}}{R_{\mathrm{ts}1}\left(x\right)\left|\right|{\mathrm{<figure-callout\; id="2"\; label="R\; ts"\; filenames="A20051009451200091.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{ts}}+R_{\mathrm{tc}1}\left(v\right)\left|\right|{\mathrm{<figure-callout\; id="2"\; label="R\; tc"\; filenames="A20051009451200091.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{tc}}}={\mathrm{\&lambda;}}_{\mathrm{sc}}(x,v)$

For the replay signal that size is fixed, spectrum component is fixing, λ _Sc(x v) is a constant, utilizes direct current adjunct circuit and infrared radiation thermometer to measure one group of Δ T _c～Δ T _sData, The Fitting Calculation can draw λ _Sc(x, v).

And then can derive formula that unit resonance frequency changes with voice coil temperature, be the temperature drift formula that the loudspeaker unit resonance frequency of institute of the present invention foundation changes with voice coil temperature:

$f_s={\mathrm{<figure-callout\; id="0"\; label="f\; s"\; filenames="A20051009451200082.png,A20051009451200091.png"\; state="\{\{state\}\}">f</figure-callout>}}_s\sqrt{1+{\mathrm{\&beta;}}_{\mathrm{sp}}{\mathrm{\&lambda;}}_{\mathrm{sc}}(x,v)\mathrm{\&Delta;}{T}_c}$

So according to two above loudspeaker unit resonance frequency f _sThe temperature drift formula and known f _S0, β _Sp, λ _Sc(x, v), promptly measurable different voice coil temperature and the resonance frequency under the centring disk surface temperature.

Characteristics of the present invention are: according to the temperature drift formula of loudspeaker unit resonance frequency, the temperature drift characteristic that changes with the centring disk surface temperature with the temperature measuring equipment of routine and electroacoustic measurement Instrument measuring resonance frequency, calculate the temperature drift characteristic that resonance frequency changes with voice coil temperature, and then change of resonance frequency situation under the inner different operating temperature in measurable unit (voice coil temperature and centring disk surface temperature), convenient and swift.Can calculate the resonance frequency under different voice coil temperature of prediction and the centring disk surface temperature.All extremely meaningful to speaker design manufacturing and quality control and powerful working condition and condition control.

The present invention proposes temperature drift phenomenon and model formation thereof that loudspeaker unit works in high-power condition resonance frequency of following time, provided and utilized conventional temperature measuring equipment and electroacoustic measurement Instrument measuring and predict the method for resonance frequency with voice coil temperature and centring disk surface temperature Changing Pattern.

Four, description of drawings

The lumped parameter analogous circuit of the loudspeaker unit internal heat dissipation path that Fig. 1 the present invention sets up for the relational expression of calculating centring disk surface temperature and voice coil temperature.P among the figure _ReBe the thermal power of voice coil loudspeaker voice coil, P _EdBe the pairing thermal power of vortex heat, R _Tv, R _TmBe respectively the entire thermal resistance of voice coil loudspeaker voice coil, C to magnet and magnet to surrounding air _Tv, C _Tm, C _TsBe respectively total thermal capacitance of voice coil loudspeaker voice coil, magnet and centring disk, Δ T _c, Δ T _m, Δ T _sBe respectively the temperature that voice coil loudspeaker voice coil, magnet and centring disk change, T _aBe ambient temperature, R _Tc1(v), R _Tc2Be respectively voice coil loudspeaker voice coil to the forced convection heat radiation of centring disk and conduction, the pairing thermal resistance of heat loss through radiation, R _Ts1(x), R _Ts2Be respectively that centring disk arrives the forced convection heat radiation of surrounding air and conduction, the pairing thermal resistance of heat loss through radiation;

Fig. 2 change curve Δ T of the loudspeaker unit resonance frequency of the inventive method match with the centring disk surface temperature _s～f _sAnd measured data: (a) full range speaker unit a; (b) woofer unit b;

Fig. 3 the loudspeaker unit centring disk surface temperature of the inventive method match and the relation curve Δ T of voice coil temperature _c～Δ T _sAnd measured data: (a) full range speaker unit a; (b) woofer unit b;

Fig. 4 direct current adjunct circuit figure is used for the Δ T with infrared radiation thermometer measuring unit a, b _c～Δ T _sData

Five, embodiment

Specific embodiments of the invention:

With actual measurement of the present invention the temperature drift characteristic of the high-power condition of loudspeaker unit resonance frequency of following time of two different sizes, unit a is that (14cm * 4cm), unit b is the woofer of diameter 16cm to the rectangle full range speaker.

Resonance frequency f when at first utilizing conventional electroacoustic measurement instrument to record unit a, b to reset small-signal at ambient temperature _S0, see Table 1.

Utilize infrared radiation thermometer and conventional electroacoustic measurement apparatus measures unit a, the Δ T of b again _s～f _sData, The Fitting Calculation can draw the temperature drift coefficient β of the resonance frequency of unit a, b with the variation of centring disk surface temperature _Sp, see Table 1.Actual measurement Δ T _s～f _sData and matched curve are as shown in Figure 2.

Utilize the Δ T of direct current adjunct circuit and infrared radiation thermometer measuring unit a, b again _c～Δ T _sData, The Fitting Calculation can draw unit a, the b centring disk surface temperature under this replay signal and the proportionality coefficient λ of voice coil temperature _Sc(x v), sees Table 1.Actual measurement Δ T _c～Δ T _sData and matched curve are as shown in Figure 3.

Shown in Figure 4: for the replay signal that size is fixed, spectrum component is fixing, λ _Sc(x v) is a constant, utilizes direct current adjunct circuit and infrared radiation thermometer to measure one group of Δ T _c～Δ T _sData, The Fitting Calculation can draw λ _Sc(x, v).

The relevant parameter of loudspeaker unit resonance frequency temperature drift characteristic under the high-power condition of table 1

The unit	f s0(Hz)	β sp	λ sc(x，v)
				a	189.2	-0.0022	0.330
b	58.0	-0.0061	0.111

So drift characteristic that resonance frequency changes with the centring disk surface temperature under the measurable loudspeaker unit high power work condition:

Unit a: $f_s=189.2\sqrt{1-0.0022\mathrm{\&Delta;}{T}_s}$

Unit b: $f_s=58\sqrt{1-0.0061\mathrm{\&Delta;}{T}_s}$

And the drift characteristic that resonance frequency changes with voice coil temperature under the loudspeaker unit high power work condition:

Unit a: $f_s=189.2\sqrt{1-7.26\&times;{10}^{-3}\mathrm{\&Delta;}{T}_c}$

Unit b: $f_s=58\sqrt{1-6.77\&times;{10}^{-3}\mathrm{\&Delta;}{T}_c}$

Claims (2)

1, the assay method of resonance frequency temperature drift characteristic during the loudspeaker unit high power work, temperature drift formula according to loudspeaker unit resonance frequency, temperature measuring device with routine detects the temperature drift characteristic that centring disk surface temperature and electricity consumption acoustic frequency and power measurement instrument mensuration resonance frequency change with centring disk surface and voice coil temperature, The Fitting Calculation goes out the temperature drift coefficient that resonance frequency changes with centring disk surface temperature and voice coil temperature, obtain the temperature drift characteristic that resonance frequency changes with voice coil temperature, and then the resonance frequency under measurable different voice coil temperature and the centring disk surface temperature

The temperature drift formula that the loudspeaker unit resonance frequency of institute's foundation changes with above-mentioned centring disk surface temperature:

$f_s=f_{s0}\sqrt{1+{\mathrm{\&beta;}}_{\mathrm{sp}}\mathrm{\&Delta;}{T}_s},$ Utilize infrared radiation thermometer and conventional one group of Δ T of electroacoustic measurement apparatus measures _s～f _sData, The Fitting Calculation can draw the temperature drift coefficient β that unit resonance frequency changes with the centring disk surface temperature _Sp

The unit resonance frequency of institute's foundation with the formula that voice coil temperature changes is:

$f_s=f_{s0}\sqrt{1+{\mathrm{\&beta;}}_{\mathrm{sp}}{\mathrm{\&lambda;}}_{\mathrm{sc}}(x,v)\mathrm{\&Delta;}{T}_c},$ For the replay signal that size is fixed, spectrum component is fixing, λ _Sc(x v) is a constant, utilizes direct current adjunct circuit and infrared radiation thermometer to measure one group of Δ T _c～Δ T _sData, The Fitting Calculation can draw λ _Sc(x, v).

2, the resonance frequency that the method for the temperature drift characteristic of resonance frequency under the mensuration loudspeaker unit high power work condition as claimed in claim 1, the temperature drift coefficient that draws after utilize measuring, calculating record when resetting small-signal is at ambient temperature calculated the loudspeaker unit resonance frequency under different centring disk surface temperatures of prediction and the voice coil temperature.

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