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Vox Gyrotone Rotary Speaker

1970s Era Vox Gyrotone 50 with Vox Midas 50 Watt Power Amp

The dynamic, vibrant sounds of an organ played through a Leslie Model 122 rotary speaker were filling the airwaves in the mid 1960s. As the manufacturer of the most popular and prestigious combo organs in the world, JMI was anxious for Vox to tap into the rapidly expanding rotary speaker market. JMI jumped into the skirmish in 1967 with their Vox Gyrotone "Type I", "Type II", "Type III" and "Type IV" Series Enclosures. Before we investigate the rotary speakers from Vox, let's spend a few moments looking at the inspiration for the Vox Gyrotone series, the Leslie Model 122. Model 122 Leslie Speaker Leslie speakers mechanicanically create frequency modulation, or vibrato, by taking advantage of the doppler effect. The doppler effect causes a sound wave to increase in frequency when it is moving toward the listener and decrease in frequency as it moves away. This is why the pitch of a police siren seems to drop as the squad passes. Don Leslie, the inventor of the Leslie speaker, discovered playing the sound of a Hammond organ through a rotating high frequency "horn rotor" and a low frequency "drum rotor" would mechanically create a vibrant, multi-speed vibrato using the doppler effect. The Model 122 Leslie speaker utilized the horn and drum rotors pictured at right. The horn rotor was mounted near the top of the cabinet and driven by a high frequency compression driver. A downward facing 15" speaker directed the bass frequencies into a rotating drum rotor, located near the bottom of the cabinet. A pair of two-speed motors spun the horn and drum rotors, creating the "Chorale" (low speed) and "Tremolo" (high speed) vibrato effect. An internally mounted 40 watt tube audio amp and two-way frequency dividing crossover network powered the Model 122. Horn Rotor from a Model 122 Leslie Speaker Drum Rotor from a Model 122 Leslie Speaker

The 1x12" Gyrotone Speaker JMI designed a rotary speaker mechanism that would be shared by all eight of the Gyrotone models produced by Vox from 1967 through 1970. Described in Vox catalogs as the "1x12" Gyrotone Speaker," it narrowly escaped infringing on any of the 50 patents held by Don Leslie for his Leslie speakers. While the Leslie Model 122 utilized a dual rotor system with one rotor for bass and a second for treble, the Vox models had only one. The "1x12" Gyrotone Speaker" system suspended a molded styrofoam rotor over a vertically firing 12" speaker (see image at left). A passive crossover accentuated the mid and high frequencies projected by the rotor. The bass frequencies were produced by stationary, forward facing speakers.

The Gyrotone "Type I" Rotary Speaker (1967) - Introduced in 1967, the compact "Type I" enclosure utilized the standard two-speed Gyrotone rotary mechanism described above. It was most likely powered by a Celestion 12" 16 ohm T.1254 ferrite speaker. The components for the rotary mechanism were mounted to a slider board for ease of access. The "Type I" had only a treble rotor and was designed to be used in conjunction with an auxiliary bass cab. The stylish, angular cabinet featured Vox grill panels on the left, right and front panels. Dimensions: 27" W x 18" T x 21" D, ~52 lbs, Power Handling: 25 watts RMS, MSRP (1967): £84

The Gyrotone "Type II" Rotary Speaker (1967-69) Also introduced in 1967, the midsize "Type II" enclosure (shown above) utilized three 12" Celestion T.1254 speakers. One of these speakers was dedicated to the two-speed Gyrotone rotary mechanism, the other two were stationary, forward facing and produced the low frequencies. Dimensions: 27" W x 26" T x 21" D, Weight: 110 lbs, Power Handling: 50 watts RMS, MSRP (1967): £157.10 The Gyrotone "Type III" Rotary Speaker (1967-69) The "top of the line" for 1967 Gyrotone "Type III" enclosure (shown at left) offered a larger cabinet for greater bass response and speakers with improved power handling capacity. A 1969 German Vox catalog suggested that the 12" speakers in the Type III were from Goodmans, perhaps the 12HPG models included by Vox with Supreme amps. One 12" speaker was dedicated to the two-speed Gyrotone rotary mechanism, the other two were stationary and produced the low frequencies. Dimensions: 27" W x 41" T x 21" D, Weight: 140 lbs, Power Handling: 100 watts RMS, MSRP (1967): £176.5

The Vox Gyrotone "Type IV" Rotary Speaker w/Internal Power Amplifier (1967) The Gyrotone "Type IV" rotary speaker (not pictured) was included in the 1967 Vox retail price list but was not mentioned in any other Vox catalog literature from the era. Unlike the Type I, II and III Gyrotone units, the Type IV included an internal power amplifier. The Type I, II and III units required a separate and external power amplifier for operation. I suspect that the Type IV added a power amplifier to a Type III model. If so, the dimensions were: 41" T x 27" W x 21" D. MSRP (1967): £225 Nameplates and "Power-On" Indicator Allthough the images of the first generation JMI Gyrotone speakers from the 1967 Vox catalog were depicted with vertical US style Vox logos, actual production models were equipped with horizontal US style Vox logos. Vox mounted the power-on indicator lamp in the center of the "O," as shown at right. Second Generation Vox Gyrotone Rotary Speakers (1970 - 1971) By 1970, both JMI and the subsequent owner of Vox, Vox Sound Equipment Limited, had gone into bankruptcy. Vox was now in the receivership of the Corinthian Bank and hoping to be rescued by a new owner. It was a time of austerity for Vox, sales were weak and they could no longer command the premium prices for their products that they charged only a few years back. Items with poor sales performance were eliminated from the product line. While the Gyrotone Series escaped the cut, their original stylish cabinets were redesigned and simplified as a cost saving measure. Page 13 from the 1970 Vox product catalog (shown below) illustrates the results of this redesign. Gyrotone II (1970) An updated version of the original Gyrotone Type II. Simplified, rectangular cabinet design. Equipped with three 100 watt, 12" Fane "Crescendo" speakers with an "Anistotropic" magnet structure. Dimensions: 27" W x 26" T x 21" D, Weight: ~110 lbs, Power Handling: 50 watts RMS, MSRP (1970): £155.0 Gyrotone 50 w/Vox Midas 50 Power Amplifier  (1970) The Gyrotone II with the addition of a 50 watt internal Vox "Midas 50" solid-state power amp. Aside from powering the Vox Gyrotone 50 rotary speaker, there was no further mention of the Midas 50 amplifier in Vox catalogs or price lists from this era. Equipped with three 100 watt, 12" Fane "Crescendo" speakers with an "Anistotropic" magnet structure. Dimensions: 27" W x 26" T x 21" D, Weight: ~145 lbs, Power Rating: 50 watts RMS, MSRP (1970): £232.50 Gyrotone III (1970) An updated version of the original Vox Gyrotone Type III. Simplified rectangular cabinet design. Dimensions: 27" W x 41" T x 21" D, Weight: ~140 lbs, Power Handling: 100 watts RMS, MSRP (1970): £166.0 Gyrotone 100 w/Vox Midas 100 Power Amplifier (1970) A Gyrotone III with a 100 watt internal Vox "Midas 100" solid-state power amp. Dimensions: 27" W x 41" T x 21" D, Weight: ~180 lbs, Power Rating: 100 watts RMS, MSRP (1970): £243.50

Further Links and References

1967 Vox "It's What's Happening" Magazine Ad - Establishes that the original name of the Gyrotone was "Gyrovox." 1967 "Vox Parade" Autumn 1967 - Vox new product announcement from the 1967 UK Trade Fair. Printed on newsprint. 1967 - 1968 Vox Solid State Amplification Catalog - First catalog offering the Gyrovox Type I, II and III 1967 Vox Price List Dated April 1967 - First Vox price list that included Gyrotone speakers 1969 "Colossus Incorporated" Vox Organ Flyer - Includes the Type II and Type III Gyrotone speakers 1969 "It's Highness" Magazine Ad - Promotes Vox Organs and Gyrotone Speakers 1969 Vox Sound Equipment Limited UK Price List - Includes the Gyrotone II and Gyrotone III 1969 German Vox Catalog - Includes the Gyrotone II and Gyrotone III 1970 Vox Sound Limited "Green" Catalog - First appearance of the second generation Vox Gyrotone Series 1970 Vox Sound Limited "Green" Catalog - First appearance Vox Midas 100 solid state organ amplifier 1970 Vox Sound Limited Price List - Pricing for the second generation Gyrotone Series 1970 Vox Sound Limited Price List - Pricing for the Vox Midas 100 solid state amplifier Do you have any pictures or catalog images of Vox Gyrotone speakers that you would be willing to share with the Vox Showroom? Please email your submissions to voxshowroom@gmail.com and I will consider them to improve and update the information on this page.