A few days after the Leslie West disaster, humbled but not deterred in our goal of building a world-class sound system, Maxson and I sat down with the JBL professional products catalog and designed and specified a much larger Showco sound system that significantly increased the number of JBL professional loudspeaker components and Marantz power amplifiers over the original JBL system specified by Walter Dick at JBL. The JBL equipment is described below and appears in JBL’s 1971 professional products catalog. Readers interested in seeing original equipment photographs, drawings, and JBL specifications can view the 1971 JBL Professional Series Catalog (PE71) in the Lansing Heritage collection. The JBL equipment described below appears in JBL's 1971 professional products catalog. Readers interested in seeing the original equipment photographs, drawings, and JBL specifications can view the 1971 JBL Professional Series Catalog (PE71) in the Lansing Heritage collection. **1971 JBL Professional Series Catalog (PE71):** [https://www.lansingheritage.org/html/jbl/catalogs/1971-pro.htm](https://www.lansingheritage.org/html/jbl/catalogs/1971-pro.htm) Brutsche and Maxson specified the following equipment: ### JBL 4520 Rear-Loading Dual-Driver Bass Cabinets **Quantity:** 8 The JBL 4520 was a large folded-horn bass enclosure designed for two 15-inch low-frequency loudspeakers. Its approximately 13-foot rear-loading horn path provided acoustic loading to 42 Hz, while at frequencies above 150 Hz, the two loudspeakers operated as direct radiators. Each of Showco’s eight 4520 cabinets contained two JBL 2220A, 8-ohm, 15-inch loudspeakers, giving the system a total of sixteen bass drivers. **Dimensions:** 50 1/4 × 35 3/4 × 29 inches deep **Weight:** approximately 240 pounds each {{< StoryImage id="showco-14-jbl-4520-bass-cabinet-1" caption="JBL 4520 Rear Loading Bass Cabinet 1970" size="medium" >}} ### JBL 2220A 15-Inch Low-Frequency Drivers **Quantity:** 16 The 2220A was an 8-ohm, 15-inch professional loudspeaker used as the low-frequency driver in Showco’s 4520 cabinets. Each speaker was rated at 100 watts program power and had a specified operating range of approximately 40 Hz to 2 kHz. The speaker used a four-inch-diameter, edge-wound aluminum ribbon voice coil and phenolic-treated linen suspension/diaphragm construction designed for the power handling and efficiency required in professional sound systems of the period. **Impedance:** 8 ohms **Program power:** 100 watts **Frequency range:** approximately 40 Hz–2 kHz **Depth:** 5 9/16 inches **Weight:** approximately 14 1/4 pounds

{{< StoryImage id="showco-15-jbl-1971-catalog-low-freq-transducers" caption="JBL 1971 Catalog Low Frequency Transducers" size="medium" >}} {{< StoryImage id="showco-16-jbl-1971-catalog-2220-photo" caption="JBL 2220A Catalog and Technical Views" size="medium" >}}

### JBL 2350 Radial High-Frequency Horns **Quantity:** 8 The JBL 2350 was a cast-aluminum radial horn used for the high-frequency portion of the system. It provided a nominal coverage pattern of 90 degrees horizontally by 40 degrees vertically and was intended to operate at a crossover frequency of approximately 500 Hz. Unlike multicellular horns, the 2350 used a continuous horn path to obtain its desired coverage pattern. Showco configured the 2350 with two, and later four, JBL 2470 compression drivers through appropriate throat-adapter components. **Coverage:** 90° horizontal × 40° vertical **Crossover:** approximately 500 Hz **Construction:** cast aluminum with acoustical damping **Dimensions:** 8 × 24 1/8 × 20 inches deep {{< StoryImage id="showco-18-jbl-1971-catalog-2350" caption="JBL 2350 Radial Horn 1970" size="small" readable="true">}} ### JBL 2361 Multicellular Long-Throw Horns **Quantity:** 4 he JBL 2361 was a multicellular high-frequency horn used where narrower coverage and longer projection were required. Its nominal dispersion was 60 degrees horizontally by 20 degrees vertically. In the Showco system, the 2361 horns supplemented the wider-coverage 2350 radial horns and provided high-frequency coverage over greater distances. **Coverage:** 60° horizontal × 20° vertical {{< StoryImage id="showco-19-jbl-1971-catalog-2361-horn" caption="JBL 2361 Long Throw Horn 1970" size="small" readable="true" >}} ### JBL 2470 High-Frequency Compression Drivers **Quantity:** 24 The JBL 2470 was a professional compression driver used to power the system’s high-frequency horns. It had a 1-inch throat, a 1 3/4-inch voice coil, a nominal impedance of 16 ohms, and a rated power capacity of 50 watts. Its specified frequency range extended from approximately 500 Hz to 12 kHz. The driver used an edge-wound aluminum ribbon voice coil and a phenolic-treated diaphragm assembly. **Impedance:** 16 ohms **Rated power:** 50 watts **Frequency range:** approximately 500 Hz–12 kHz **Voice coil:** 1 3/4 inches **Throat:** 1 inch **Depth:** 3 7/8 inches **Weight:** approximately 11 pounds {{< StoryImage id="showco-20-jbl-1971-catalog-2470" caption="JBL 2470 Compression Driver 1970" size="medium" >}} ### JBL Horn-Throat Adapters Connecting JBL compression drivers to different horns required specialized adapters: - 8 JBL 2329 dual-entry throats used with 2350 horns to accommodate two compression drivers with 2-inch-diameter throats. - 16 JBL 2327 adapters provided the transition from the JBL 2329 dual-entry throat, designed for two drivers with 2-inch throats, to the 1-inch-throat JBL 2470 compression drivers. - 4 JBL 2332 dual-entry adapters were used to attach two JBL 2470 compression drivers to the JBL 2361 long-throw horns. {{< StoryImage id="showco-21-jbl-1971-catalog-horn-adapters" caption="JBL 1971 Catalog Horn Adapters" size="medium" >}} ### Marantz 16B Power Amplifiers **Quantity:** 16 Showco powered the system with sixteen Marantz Model 16B solid-state stereo power amplifiers. Each 16B incorporated two separate 100-watt amplifier modules bolted together behind a gold-anodized front panel, providing 100 watts per channel into an 8-ohm load. For the bass cabinets, one Marantz 16B powered each JBL 4520 cabinet. Each amplifier’s 100-watt module drove the cabinet’s two JBL 2220A, 8-ohm, 15-inch loudspeakers. The Marantz 16B amplifiers powering the high-frequency horns drove two, and later four, JBL 2470 compression drivers from each 100-watt module. Two 16-ohm 2470 drivers connected to a 100-watt amplifier module divided the available power between the two drivers, providing approximately 50 watts to each driver. With four JBL 2470 drivers on each 100-watt module, each driver received 25 watts, which greatly improved the reliability of the drivers’ diaphragms. This arrangement used a passive 800 Hz crossover connected between the audio mixers and power amplifiers. It gave the Showco system separate amplification—bi-amping—for the bass and high-frequency sections at a time when high-powered, bi-amped, solid-state professional sound reinforcement was still relatively new. {{< StoryImage id="showco-marantz-16b-modules-1971" caption="Marantz 16B with two separate 100 watt power amplifier modules connected together 1970" size="medium" >}} We decided to use the JBL speakers originally specified by Walter Dick for the house system as side-fill, onstage monitors. Each side-fill speaker consisted of one 4530 single rear-loaded bass cabinet with one 2220B 15-inch speaker, one 2390 high-frequency lens horn, one 2470 compression driver, and one 3110 passive crossover network. Each was powered by one Marantz 16B, 100-watt power-amplifier module. About March 1, 1970, we placed orders for additional equipment with Taft Broadcasting and Arnold & Morgan Music. I set up a woodworking shop in Maxson’s garage with a radial-arm saw, table saw, various powered hand tools such as drills, routers, and jigsaws, and a large worktable that I made from plywood. Maxson set up an electronics work area in an upstairs room inside the house. We needed to arrange a bank loan to finance the equipment purchases because we had no company credit history. My widowed mother—my father had died in 1968—loaned me $15,000 ($120,000 in 2025) worth of AT&T stock that she and my father had laboriously earned and saved over the previous 25 years while he was working as an AT&T executive. We used the stock as collateral for a $10,000 ($80,000 in 2025) loan from First National Bank in Dallas. The three founders of Showco—myself, Jack Maxson, and Jack Calmes—also personally guaranteed the loan. Only a mother’s love would have inspired such a risky move. ## The First Showco Mixing Console We needed to build a new mixing setup for the new sound system and we decided to change from the Altec 1567A mic mixers that I had used in my sound systems in the 1960’s to the Grommes Precision G5M six channel tube mic mixer: {{< TechnicalSpec title="Grommes Precision G5M Mixer" count="3" specs="5 XLR mic inputs and one line level input with a main 600 ohm balanced line output. A second separate high impedance line level output was independent of the front panel volume controls, intended to be used for connecting to a tape recorder." imageId="showco-23-grommes-g5m-mixer, showco-grommes-g5m-mixer-rear-view-1970" imageCredits="© Rusty Brutsche Archive|© reverb.com Silverdog sales listing" caption="Grommes G5M Mixer 1970. © Rusty Brutsche Archive" >}} {{< TechnicalSpec title="First Showco Sound Mixing Console" specs="Three Grommes mixers mounted in a custom rack made by Wilkins Trunk Company. Fancy angled design by Jack Maxson. Featured the first Showco Master Crossover Drive Panel at the top." imageId="showco-002-equipment-70-73" caption="First Showco Sound Mixing Console 1970. © Rusty Brutsche Archive" >}} At the top of the rack is the first Showco Master Crossover Drive Panel. This unit and later versions of it became the center of Showco’s sound systems. This first unit housed a passive RC crossover network with an 800 Hz crossover frequency, a summing network that connected the outputs of the three Grommes mixers together and two line amplifiers that fed the low frequency and high frequency audio signals from the crossover network to the Marantz power amps for the bass cabinets and high frequency horns respectively using two 600 ohm balanced lines. On one of the first shows that Maxson and I did with this mixing console prior to the Led Zeppelin show on March 28, 1970, we plugged the low frequency and high frequency drive lines in backwards and fed low frequencies to the high frequency compression drivers and blew out all of the diaphragms in the drivers. We reversed the sex of the drive line XLR connectors to prevent this from happening in the future and this became standard practice in all Showco sound equipment. {{< TechnicalSpec title="Showco Master Crossover Drive Panel" specs="Custom built line amplifiers converting 16 ohm speaker outputs to 600 ohm balanced line level signals using matching transformers. Featured separate volume controls for lows/highs, master volume, and VU meter." imageId="showco-25-first-generation-showco-master-panel" caption="First Generation Showco Master Crossover Drive Panel 1970. © Rusty Brutsche Archive" >}} {{< TechnicalSpec title="Processing Rack (Lower Console)" specs="The top unit is the stage monitor mixer made using a Grommes G-23 public address amplifier modified to be a line amplifier which controlled the mix and the volume level for the stage monitors and provided a mic input and volume control for talkback to the stage. A Melcor 7 band equalizer for main speaker stacks and a UREI 1176LN limiter to protect the system from being over driven. Mounted on Colson 3 ½” heavy-duty casters." imageId="showco-003-equipment-70-73" caption="Lower Section featuring Stage Monitor Mixer, Melcor EQ and UREI 1176LN limiter. © Rusty Brutsche Archive" >}} When the large order of JBL and Marantz equipment was delivered, I built plywood cases for the high frequency horns and plywood amp racks to hold the Marantz 16B amplifiers. I mounted four of the 3 ½” Colson casters on every piece of equipment. I purchased Wilkins steamer trunks to hold mic stands, cables, microphones and other accessories and I mounted four of the Colson casters on each trunk. On the JBL bass cabinets I routed off the sharp edges, mounted the Colson casters to wooden 2X4’s that I fastened to the bottom of the cabinet and I mounted a connector for the speaker cable and an expanded metal grill over the 15” speakers. The bass cabinets were made out of fiberboard and were very heavy. ## The Led Zeppelin Eureka Moment We received a call from Terry Bassett at Concerts West to book a sound system for Led Zeppelin’s show at the 10,000-seat Memorial Auditorium in Dallas on March 28, 1970. We rented an 18-foot Ryder yellow truck, rolled the new equipment down Maxson’s driveway at his house on W. Beverly Drive in Dallas on new Colson casters, and loaded the truck using its power liftgate. Zeppelin had started this U.S. tour on March 21, 1970, and had played six shows before arriving in Dallas. At the time, very few sound companies offered touring sound systems. The local promoter in each city was responsible for hiring a local company to provide sound, and almost all local sound companies had equipment suitable only for small meetings or announcing basketball games. The sound equipment was not designed for the high sound levels of new rock concerts, so groups had to suffer through bad sound night after night. Showco’s Eureka Moment occurred when Zeppelin arrived in Dallas and used our new Showco system. They were blown away by the sound. The show sounded great and was a huge success. Their manager, Peter Grant, told Terry Bassett that he wanted to use the Showco system for the next leg of Led Zeppelin’s U.S. tour, which began on August 10, 1970. In hindsight, the bad experience with Leslie West had actually been a blessing because it motivated Maxson and me to build a really big sound system for the time, all at once and quickly, rather than piecemeal over time. The birth of the concert-touring industry was a huge wave that began cresting in early 1970. Having a sound system capable of delivering concert-quality sound to an audience seated in a 15,000- to 18,000-seat hockey or basketball arena enabled the essential technology required for the development of the concert-touring industry. Because we had built that big JBL sound system, we were perfectly positioned to jump on the wave and start riding it. The Led Zeppelin show in Dallas on March 28, 1970, validated our vision and set us on the path to great success in the worldwide entertainment industry. To further validate Showco’s Eureka Moment, Terry Bassett called to book a new Showco sound system for a Three Dog Night show at Memorial Auditorium in Dallas on April 26, 1970. We did the Three Dog Night show with Maxson operating the system, and the same thing happened as with Zeppelin: Three Dog Night loved the sound and wanted to take the system on the road with them. Maxson hired a roadie, Tiny Gosson, who took the system in the Ryder truck and began doing shows with Three Dog Night, becoming their sound engineer for several years. With Three Dog Night as our first touring client and Led Zeppelin lined up as our second touring client, Showco sound was off and running two months after we built our first Brutsché-Maxson-designed sound system. {{< FeaturedImage id="showco-copy_image_255_nx_bw" title="Led Zeppelin and Showco: Oklahoma City, August 1970" caption="Led Zeppelin show in Oklahoma City, August 20, 1970 during the summer leg of their 1970 US Tour. Rusty Brutsché is pictured wearing a white t shirt and mixing the sound from a location on stage left behind the speaker stacks. Peter Grant, Led Zeppelin’s manager is standing next to Rusty at stage left. The first-generation high frequency horn cabinets are stacked on top of the bass cabinets on stage left and stage right. The casters were mounted on the side of the horn cabinets and were smaller than the 3.5” Colson casters that were used on the next generation cabinet design and that became the standard Showco caster on all of our equipment. The first-generation side fill monitors with the JBL 4530 bass cabinet and the JBL 2390 high frequency lens horn are located downstage left and right." position="left center" fit="contain" readable="true" >}} {{< FeaturedImage id="showco-ps_edit_3_d5_zep099led" title="Showco Speaker Stacks - Technical Detail" caption="Showco speaker stacks for Led Zeppelin show in Oklahoma City on August 20, 1970. The bass cabinets were the stock JBL 4520 dual rear loaded cabinets that were made of fiberboard. Each cabinet had two JBL 2220 15” 100 watt speakers. I mounted 2 X 4’s on the bottom of the cabinets to mount the 3 ½” Colson casters because the fiberboard was not strong enough to hold the bolts used to attach the casters. The horn cabinets were the first generation design with small casters mounted on the side of the cabinet and no lids to cover the horn mouths during transport. The side fill monitors were the original JBL speakers specified by Walter Dick at JBL that we used for the show with Leslie West and Mountain on February 23, 1970. Photo Carl Dunn." size="small" readable="true">}} {{< StoryImage id="showco-carl-dunn-2-photos-image100a" title="Bullets for Earplugs: A Generational Collision" caption="Loudness and security were major issues on the early Led Zeppelin tours and police officers were frequently used as security and placed along the front of the stage during the shows. This officer placed bullets from his side arm into his ears to substitute for ear plugs to protect his hearing from the loud stage volume at the Led Zeppelin show in Ft. Worth, Texas, August 22,1970. Photo Carl Dunn."size="small" readable="true" >}} {{< StoryImage id="showco-cd_lz_bw-168_nx_bw_" title="Security and Chaos" caption="Police Officers being used for security at Led Zeppelin show in Ft. Worth, Texas August 22, 1970. Photo Carl Dunn." size="small" readable="true" >}} {{< StoryImage id="showco-044-zeppelin-promo" caption="John Bonham Led Zeppelin 1969. Photo Carl Dunn" size="small" readable="true" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-robert_2_6x9_ls" caption="Robert Plant Led Zeppelin 1969 Photo Carl Dunn" size="small" readable="true" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-zep_2" caption="Jimmy Page Led Zeppelin 1969 Photo Carl Dunn" size="small" readable="true" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-zep_templet" caption="John Paul Jones Led Zeppelin 1969 Photo Carl Dunn" size="small" readable="true" >}} {{< ShowcaseGallery id="carl-dunn-5" title="1970 Led Zeppelin Tour" year="1970" band="Led Zeppelin" size="small" readable="true" >}}

Showco History