1. Cross-References to Related Application.

This application claims priority to IT Utility Model Application, Serial No. FO2005U000001 filed Gen 12, 2005.

2. Field of the Invention.

This invention relates generally to a dynamic loudspeaker with recycle system having a sufficient air movement.

3. Related Art.

To the actual state of technique applying to the clamps of a loudspeaker an high level electric signal causes damage due to thermal limits (components' overheating) and mechanics limits (excursion of the mobile parts elevated). Moreover the maximum power handle by a loudspeaker is proportional to the maximum temperature that its voice coil can reach. Overheating components loudspeaker also causes another problem: the power compression, that represent the reduction of power during the loudspeaker action in the time.

The power compression problem (as illustrated in CHART 1) describes the voice coil temperature and electric power plots of a loudspeaker under maximum power. Test period: 60 seconds. Type of applied signal: 120 Hz sinusoid. Applied power: 154 watts. - The electric charts values are measured with SpeakerLAB: automatic system of measure for loudspeaker thermal and power test, projected and built by the same author-

Test start at voice coil temperature of 18 °C, after 1 minute report 115 °C; in the same time the electric power start at value of 155 Watts, after 1 minute report a value of 119 Watts.

TABLE 1 shows the difference between final and initial value of temperature (ΔT) and power values (ΔP). VARIATION ΔT [°C] +97 ΔP [W] -36

CHART 1 represent the electric power compression while CHART 2 shows acoustic power compression of the loudspeaker.

Contemporarily the previous measure, microphone -at 1 meter on loudspeaker axis- records a 2.6 dB loss (TABLE 2). VARIATION PC [dB] -2.6

The loudspeaker used in tests is a standard woofer, with support 8 of the voice coil lengthened, it provided with holes 3 in the back pole plate 2 and in front pole plate 4, but without cap 1 (as illustrated in FIG. 1 and FIG. 2).

Recycling airflow systems are disclosed in JP-2004/186898 and CA-1 2270726.7.

SUMMARY OF THE INVENTION

It is possible to decrease the power compression and increase the output power of the same woofer forcing the convection cooling on the voice coil 9; recycling the air flow produced during the dust cap 13 movement and passing through the hole 6 in the nucleus of the back pole plate.

The object of the present invention is achieved by a loudspeaker as disclosed in claims 1, 2.

This results are obtained with a metallic cap 1 in woofer added (also illustrated in FIG. 3 and FIG. 4). The results of the air flow created through the holes by the cap in FIG. 5 and FIG. 6 are visible. Air flow produces an air recycle that flows throughout the voice coil, cooling it and increasing the loudspeaker performances in electric and acoustics power.

VARIATION ΔT [°C] + 57 ΔP [W] -21

When measures of the same loudspeaker are performed, with the cap placed, a great improvement is obtained (as visible in CHART 3). The temperature of the voice coil in this test varies from 17 °C to 74 °C, thus the electric power as before starts from value of 155 Watts, at the end of 1 minute test is 134 Watts. TABLE 3 shows the results.

Moreover, the increase of temperature is limited, then there are some advantages in the containment of electric power loss. Important results are showed from electric and acoustic power; in fact the graph of CHART 4 report the loss of acoustic power limited to 1.3 dB.

TABLE 4 and TABLE 5 shows electric and acoustic power compression of the loudspeaker respectively with and without recycle system (SdR). The analysis show absolute value of the relative difference (|ΔRel|) of woofer endowed with recycle system, in comparison to the same woofer without recycle system; it illustrates a voice coil temperature attenuation of 40 °C, an increase in electric power of 15 Watts and an increase of acoustic power output of 1.3 dB.

Without SdR with SdR |ΔRel| ΔT [°C] + 97 + 57 40 ΔP [W] -36 -21 15

without SdR with SdR |ΔRel| PC [dB] -2.6 -1.3 1.3

FIG. 7 and FIG. 8 reported the case in which, for technical or construction loudspeaker characteristic, a workmanship of the anterior pole plate is not possible or too to perform holes on such plate, the recycle of the air could be used to cool voice coil by a different profile of the cap.

This woofer doesn't have the lengthened support of voice coil and it is deprived of thickness. The only changes performed to the standard woofer, therefore, there are the holes in the back pole plate and the insertion of new cap.

The modified cap leaves a part of holes of the back pole plate open, in such way the air flow, pushed in (compression phase, illustrated in FIG. 9) from the dust cap through the back pole plate nucleus hole, is made to converge by the cap through internal holes in the cap, to after escape from the external holes in the cap.

In expansion phase the air flow follows the same run, but with opposite verse. The performances results of woofer illustrated in FIG. 8 are 5% lower in comparison the woofer of FIG. 4.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a back view of a woofer with cap.

FIG. 2 is a cross-sectional view of a woofer with cap.

FIG. 3 is a back view of woofer with cap.

FIG. 4 is a cross-sectional view of woofer in FIG. 2, with pole plates illustrated.

FIG. 5 is a cross-sectional view of woofer with cap and illustrated air movement during compression stage.

FIG. 6 is a cross-sectional view of woofer with cap and illustrated air movement during expansion stage.

FIG. 7 is a back view of a woofer with modified cap.

FIG. 8 is a cross-sectional view of woofer with modified cap, with pole plates illustrated.

FIG. 9 is a cross-sectional view of woofer with modified cap and illustrated air movement during compression stage.

FIG. 10 is a cross-sectional view of woofer with modified cap and illustrated air movement during expansion stage.