US1789270A - Adjustable speaker unit - Google Patents

Description

Jan. 13, 1931. BQXLEY 1,789,270

ADJUSTABLE SPEAKER UNIT Filed Feb. 16, 1927 2 Sheets-Sheet 1 A TTORNEYS.

Jan. 13, 1931. F. BOXLEY 3,789,279 1 ADJUSTABLE SPEAKER UNIT Filed Feb. 16, 1927 2 Sheets-Sheet -2 IN V EN TOR.

A TTORN E YS.

Patented Jan. 13, 1931 UNITED STATES FREDERICK BOXLEY, F OAKLAND, CALIFORNIA ADJUSTABLE SPEAKER UNIT 'Application filed February 16, 1927. Serial No. 168,815.

This invention relates to sound reproducers such as employed in conjunction with radio receiving sets or phonographs which reproduce and amplify sound through vacuum tubes and the like, and especially to an adjustable attachment which will afford a considerable range ofmodulation in quality, volume, intensity, flexibility, etc., of the sound or tones reproduced.

Those who have studied the physics of sound even superficially will know that every body has a sound frequency period of its own. For instance, a tuning fork may have a period vibration of exactly 256. This is determined not only by the physical dimensions of the fork but also by its shape. A wooden box, a metal bar, a plate; all such things have their own frequency periods and the speaker diaphragm is no exception. Every diaphragm used in. a telephone or loud speaker has its own special sound period which will depend upon (1st) the thickness of the diaphragm, (2nd) the diameter of the diaphragm, (3rd) the shape thereof and 1th) the particular material from which it is constructed.

There is always one particular frequency which will find the diaphragm 'most sympathetic and which will represent its highest point of efiiciency. This statement should not be construed to mean that a diaphragm cannot be made to vibrate to sounds having a frequency above or below this natural period but it should be construed to mean that it is physically impossible for the diaphragm to reproduce otherfrequencies with the same degree of faithfulness that it is able to reproduce a frequency at or near that of its own period. With conditions existing as above stated, one cannot expect a loud speaker to respond perfectly to the Woodwinds, bass viols. kettle drums and brasses of a symphonic orchestra, nor can one expect such ,a diaphragm to respond with equal efficiency to the voices of baritones, tenors, contraltos,

- Sopranos, etc.

The sound reproducing qualities of a diaphragm is also affected by other factors which tend to render the tones hard, harsh,

m shrill and penetrating, or conversely, low, in-

distinct, muflled and jumbled; These factors may be caused by overloading of the magnets by which the diaphragm is actuated,

by improper adjustment of the reed or armature with relation to the magnets and dia- 65 phragm, by lost motion between the connected parts, by improper leverage connections and by variation in impedance between the last vacuum tube of a receiving set and the impedance of the coil of the speaker unit, etc. The sound reproducing qualities of a diaphragm is also affected by variation in the modulated current flowing through the coils whereby the armature is aflected, i. e., if a, receiving set is located within a few blocks of a broadcasting station, the modulated current flow through the coils may be so strong as to cause the armature to vibrate excessively thus producing a blasting or vibrating sound. Again it is possible that a broadcasting station may be at such a distant point that the modulated current flowing through the coils is so Weak that the armature will not be affected and no sound will be reproduced or at least will be so faint as to be of no practical value.

The object of the present invention is to generally improve and simplify the construction and operation of sound reproducers of the character described, to provide an adjustable attachment whereby the diaphragm of a, sound reproducer will be caused to vibrate at highest efliciency, to provide an adjustable attachment whereby the tone quality of the sound reproduced may be modulated to produce clear tones, to increase volume, etc. And further to provide an adjust-able attachment whereby a resistance may be imposed upon the armature and the diaphragm when the modulated current flow is excessive and whereby the resistance may be materially decreased when the modulated current flow is Weak as when receiving from distant broadcasting stations. The invention is shown by Way of illustration in the accompanying drawings in which Fig. 1 is a front view of a loud speaker unit showing the application of the invention,

D which is Fig. 2 is a central vertical section taken on. line IIII, Fig. 1,

Fig. 3 is a perspective view of the adjustable mechanism whereby the reed arm is supported,

Fig. 4 is a perspective view of yoke,

Fig. 5 is a perspective view of the reed arm and the connecting rods attached thereto,

Fig. 6 is a perspective view of the bearing block,

Fig. 7 is a perspective view of the slidable support,

Fig. 8 is a perspective view of the tension sprmg,

Fig. 9 is a perspective view of the main supporting plate,

Fig. 10 is a side elevation of a reed type of speaker unit,

Fig. 11 is a side elevation of a modified form of a reed type of speaker unit.

Referring to the drawings in detail and articularly Figs. 1 and 2, A indicates a liase plate on which is supported a permanent'magnet B, a reed arm C, an armature ositioned betweenthe poles of the magnet and coil windings E through which the modulated current from the tubes or receiving set is directed. I

A standard balanced or pivoted armature type of speaker unit is illustrated in Figs. 1 and 2, the armature D is shown as being centrally pivoted as at F. It will be noted that the armature D is connected through rod 2 with the reed arm C and that this is in turn connected with the diaphragm G through means of the rod 3. The armature is centrally suspended on delicate bearings between the poles of the powerful permanent magnet and since the pulling force of each pole of the magnet is equal and in op-,

- posite directions, no strain is placed on the diaphragm when the speaker is not in use. The armature is also disposed between the coils E and the modulated current impulses from the radio set are permitted to flow through these coils. This modulated or fluctuating current causes the armature to vibrate in the permanent magnetic field and these vibrations are transferred through the rod '2 to the reed arm C and from the reed arm through the rod 3 to the diaphragm, and the diaphragm is thus made to keep in step with the armature.

The majority of loud speakers placed on the market have a fixed or permanent connection between the armature D and the diaphragm G and while a particular type of speaker may operate to fair satisfaction with a certain type of receiving set, it may be entirely unsuited to another type of set due to the variation of impedanceand other factors. In the present instance the vibratory movement of the armature is first transmitted to a reed arm and then to the diaphragm of the speaker. A reed arm of considerable length is employed and means are provided for increasing or decreasing the point of bearing of the reed arm, the means employed being best illustrated in Figs.. 2 and 3' and being generally indicated by the reference character H. The mechanism H is an adjustable bearing which is adapted to engage and support the reed arm C at any point intermediate the rod 3 and the bearing block 4. This bearing is constructed as follows:

.Formed in the base plate A is an elongated receive a. clamping nut 8. Interposed between the T-shaped block and the base plate A- is an elongated tension spring 9 which is provided with a central rectangular shaped opening 6?) to permit the extension 6a of the block to pass therethrough. Straddling the upper end of the T-shaped block is a bearing block 10. This block is provided with bevelled ends 10a and with two interspaced foot extensions 106 which are adapted to engage the upper surface of the tension spring 9 on opposite sides of the T-shaped block, these foot extensions being padded as indicated at 100. The reed arm C is disposed in parallelism with the base plate A in alignment with the elongated slot 5 formed therein. It passes over the bearing block 10 and is supported thereby and it is adapted to be clamped to the bearing block and the base plate by means of a yoke-shaped member 11 which straddles it and which is secured to the T-shaped block by means of screws 11a. When the several parts of the adjustable bearing H are assembled as shown in Figs. 2 and 3, and if it is desired to adjust the point of support, it is merely necessary to loosen the clamping screw 8 and then to slide the adjustable bearing one way or another in the longitudinal slot 5. If it is desired to decrease the lever action of the reed arm C with relation to the armature and the diaphragm G, the adjustable bearing is moved inwardly in the slot 5 in the direction of arrow a (see Fig. 2), if it is desired to increase the length or lever action of the reed arm with relation to the armature and the the adjustable hearing as a whole at the point.

of adjustment and it will at the same time form a support for the reed arm. The adjustable connection between the armature and the diaphragm has been found to be of great importance as the tone quality of the sound reproducer may be considerably improved or the sound reproduced as a whole may be rendered more sensitive to reception from broadcasting stations located at a great distance, etc. For instance, if the tones seem to be low or muflied, a slight tightening action on the screw 8 may be all that will be required to clear the tones. Conversely, if the tones are shrill or sharp, it may be remedied by a slight slackening of the screw, etc. That is, the adjustable bearing does not only serve the function of increasing or decreasing the lever arm action of the reed arm C and the ratio of movement between the armature and the diaphragm, but it also serves the function of adjusting the armature D with relation to the pole pieces. For instance, by tightening the screw 8 and compressing the tension spring 9, a downward pull may be exerted on the rod 2 which is suflicient to tilt the armature about its central pivot, thus bringing the pivot ends ,of the armature into closer proximity to the pole pieces or vice versa.

If a receiving set employing a loud speaker is positioned fairly close to a broadcasting station, it is possible that the modulated current flowing from the tubes through the coils of the speaker is so strong that the tones reproduced tend to vibrate and blast. In such an instance the tone quality may be materially improved by moving the adjustable bearing longitudinally of the reed arm in the direction of arrow (1. This decreases the ratio movement between the armature and the diaphragm and it will at the same time impose a resistance which will tend to further decrease the movement of the armature and diaphragm. 011 the other hand, if theperson is listening in to a broadcasting station located several hundred, one thousand, or more miles away, it is possible that the modulated current flowing from the tubes to the coils of the speaker are so weak that the armature is not sufiiciently affected to operate the diaphragm. In that instance the adj ustable bearing 10 is moved outwardlv on the reed arm in the direction ofarrow 7). action is thus increased, the resistance is materially reduced and the armature will thus be more sensitive and easily afit'ectedbythe weaker currents. In other words, with an adj ustment of this character it is possible to listen in to different stations which-otherwise would not be heard. It might be stated that the adjustments provided serve three main functions 1st, that of increasing or decreasing the lever arm action between the armature and the diaphragm, 2nd, that of increasing or decreasing resistance imposed upon the armahe lever arm ture and diaphragm, and 3rd, that of adjusting the armature with-relation to its pole pieces. This is also of considerable importance, particularly when listening to a distant station as the modulated currents passing through the coils of the speaker are in some instances so weak that the pole pieces are not materially affected, and in that instance, it is necessary to adjust the armature so as to assume a position in as close proximity to the pole pieces as possible. Suffice. it to say that the adjustments provided permit a wide range of tone modulation. It

also permits a speaker or sound reproducer to be adjusted to be more resistant or vice versa or more sensitive as conditions may require. It also permits adjustments which will render diaphragms of varying diameters, thicknesses, shapes. etc, more efficient withrelation to the output of the radio set or amplifying instrumentthan would otherwise be the case. Referring to Figures 2 and 5, it will be noted that the reed arm increases in thickness from end to end, it being thinnest or lightest at the end adjacent the armature and proportionately heavier at'the opposite end. This is important as the resistance imposed upon the armatureand diaphragm may accordingly be varied to a considerable degree when the bearing H is adjusted longitudinally of the reed arm. It should also be noted that a pad A1 is interposed between the shown as attached to a balanced or pivoted armature type of speaker. 11 the adjustable bearing is shown as at tached to reed types of speaker units. For instance, in Fig. 10 areed 15 is shown as rigidly secured and supported on a bearing post 16. This reed extends between the poles of the magnet and also serves the function of an armature, the free end of the reed is in this instance connected with the main reed arm C-by means of a rod 2a and the main reed arm is in turn connected with diaphragm not here shown by a rod 3a. The adjustable bearing H is identical in construction to that shown in connection'with Figs. 1 and 2 and is adjustable and operable in the same manner, the only difference being that two tension springs are employed as indicated at 9 1 and 9a. The spring 9a on the rear side of the base plate may or may not be. employed as desired, the same bein true of the other units disclosed. In the F1g.' 11, the main reed arm is again indicated at C while the arma- In Figs. 10 and.

ture reed 2b is shown as directly connected or attached to the free end of the reed arm C without any intermediate connection as illustrated in Figs. 2 and 19. The adjustable bearing H is also employed in this instance and the lever arm action may accordingly be increased or ,decreased as conditions may demand.

While certain features ofthe present invention are more or less specifically described and indicated, I wish it understood that various changes may be resorted to within the scope of the appended claims; similarly, that the materials and finish of the several parts employed may be such as the manufacturer may dictate or varying conditions or uses may demand:

said reed arm having a lever. arm action between the armature and the diaphragm and means for increasing or decreasing the length of lever arm action between the armature and the diaphragm.

2. The combination with the vibrating armature and the diaphragm of a sound reproducer of a reed arm connected with the armature at one end, a bearing member sup-. porting the opposite end of the reed arm, said reed arm functioning as a lever arm between the armature and the diaphragm and means for adjusting the bearing longitudinally of the reed to increase or decrease the length of the lever arm. a

3. The combinatibn with the vibrating armature and the diaphragm of a sound reproducer of a reed arm connected with the armature at one end, a bearing member supporting the opposite end of the reed arm, said reed arm functioning as a lever arm between the armature and the diaphragm and an adjustable bearing movable longitudinally of the reed arm to increase or decrease the length of the lever arm action.

4. In a sound reproducer, a balanced armature, pole members cooperating with the armature, a diaphragm connected with the armature, and a means for varying the ratio of movement of the diaphragm with relation to the balanced armature.

5, In a sound reproducer, a balanced type of armature, pole members cooperating therewith, a diaphragm, a reed arm connected at one end with the bearing armature, a fixed bearing member supporting the opposite end of the reed arm, a connection between the reed arm and the diaphragm and an auxiliary bearing member adjustable longitudiarmature at one end, a support for the opposite end of the reed arm, a connection between the reed arm and the diaphra 111, said reed arm having a lever arm action etween the armature and the diaphragm, means for increasing or decreasing the length of lever arm action between. the armature and the diaphragm, and means whereby the movement of the armature and the diaphragm may be variably resisted.

7. The combination with the vibrating armature and the diaphragm of a sound reproducer of a reed arm connected with the armature at one end, a support for the op posite end of the reed arm, a connection between the reed arm and the diaphragm, said reed arm having a lever arm action between the armatureand the diaphragm, means for increasing or decreasing the length of lever arm action bet-ween the armature and the diaphragm, means whereby the movement ofthe armature and diaphragm may be variably resisted, and means whereby the position of the armature may be ad usted with relation to pole pieces cooperating therewith. r

8. The combination with the vibrating armature and the diaphragm of a sound reproducer of a reed arm connected with the armature at one end, a support for the reed arm and adjustable longitudinally of the reed arm, and a connection between the diaphragm and the reed arm at a point intermediate the armature and the adjustable support.

9. The combination with the vibrating armature and the diaphragm of a sound reproducer of a reed arm connected with the armature at one end, a support for the reed arm and adjustable longitudinally of the reed arm, a connection between the diaphragm and the reed arm at a point intermediate the armature' and the adjustable support, and means permitting'vertical adjustment of the longitudinal adjustable support.

FREDERICK BOXLEY.

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