{{< ShowcaseGallery id="carl-dunn-5" title="1970 Led Zeppelin Tour" year="1970" band="Led Zeppelin" >}} A few days after the Leslie West disaster, humbled but not deterred from 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 with the following components; Photos from lansingheritage.com, catalog courtesy of Peter Larsen. {{< TechnicalSpec title="JBL 4520 Rear Loading Dual Driver bass cabinets" count="8" specs="A thirteen-foot folded horn with maximum loading to 42Hz, provision for two 15-inch low frequency drivers, uniform response to 50 Hz, usable to 30 Hz, above 150 Hz the low frequency drivers operate as direct radiators." dimensions="50 ¼” X 35 ¾” X 29” deep" weight="240 lbs" imageId="showco-14-jbl-4520-bass-cabinet-1" caption="JBL 4520 Rear Loading Bass Cabinet 1970" >}} {{< TechnicalSpec title="JBL 2220A 8 ohm 15” low frequency speaker" count="16" specs="40-2000 Hz, 100 watts program power, phenolic impregnated linen diaphragms and edge wound aluminum ribbon voice coils provide maximum power capacity and conversion efficiency." weight="14 1/4 lbs" dimensions="5 9/16” deep" imageId="showco-15-jbl-1971-catalog-low-freq-transducers, showco-16-jbl-1971-catalog-2220-photo" caption="JBL 2220A Catalog and Technical Views" >}} {{< TechnicalSpec title="JBL 2350 Radial High Frequency Horns" count="8" specs="Offers exceptionally uniform frequency response in a tightly controlled pattern. There are no dividers or discontinuities. The waveform expands smoothly through a single, unobstructed path. 90-degree horizontal X 40-degree vertical pattern, requires 2328 or 2329 throat, 500 Hz crossover, cast aluminum, damped." dimensions="8” X 24 1/8” X 20” Deep" imageId="showco-18-jbl-1971-catalog-2350" caption="JBL 2350 Radial Horn 1970" >}} {{< TechnicalSpec title="JBL 2361 Multicellular Long Throw High Frequency Horn" count="4" specs="60-degree Horizontal X 20 degree Vertical Pattern" imageId="showco-19-jbl-1971-catalog-2361-horn" caption="JBL 2361 Long Throw Horn 1970" >}} {{< TechnicalSpec title="JBL 2470 High Frequency Compression Drivers" count="24" specs="Phenolic impregnated linen diaphragms and edge wound aluminum ribbon voice coils provide maximum power capacity and conversion efficiency. 16 ohms, 50 watts Power, 500-12 kHz, 1 ¾” voice coil diameter, 1” throat." weight="11 lbs" dimensions="3 7/8” Deep" imageId="showco-20-jbl-1971-catalog-2470" caption="JBL 2470 Compression Driver 1970" >}} ### JBL Horn Adapters & Accessories The system required specialized throat sections and adapters to connect the various drivers and horns: {{< TechnicalSpec title="JBL Horn Adapters & Throats" specs="8 Each-2329 Dual Entry Throat (for 2350 horn to two 2-inch drivers); 16 Each-2327 Adapter (for 2-inch horn entry to 1-inch driver); 4 Each-2332 Dual Entry Adapter (for 2-inch horn entry to dual 1-inch drivers for 2361 long throw horns)." imageId="showco-21-jbl-1971-catalog-horn-adapters" caption="JBL 1971 Catalog Horn Adapters" >}} {{< TechnicalSpec title="Marantz 16B Power Amplifiers" count="16" specs="Stereo solid-state amplifiers, 100 watts per channel into 8 ohms. Each bass cabinet was powered by one 16B with each 100-watt module powering one 2220A 15” speaker, each high frequency horn had two 2470 drivers and was powered by one 100 watt 16B module thereby delivering 50 watts of power to each 2470 driver." imageId="showco-marantz-16b-modules-1971" caption="Marantz 16B with two separate 100 watt power amplifier modules connected together 1970" >}} 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 would consist of a 4530 single rear loaded bass cabinet with one 2220B 15” speaker, one 2390 high frequency lens horn with one 2470 compression driver and one 3110 passive crossover network all powered by one Marantz 16B 100 watt power amp module. About March 1, 1970, we placed the orders for the additional equipment with Taft Broadcasting and Arnold & Morgan Music. I set up a woodworking shop in Maxson’s garage with a radial arm saw and a table saw and various powered hand tools like drills, routers, jig saws and a large work table that I made from plywood. Maxson set up an electronics work area in an upstairs room inside his house. We needed to arrange a bank loan to finance the purchase of the additional equipment and we had no credit history as a company, so 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 for the past 25 years while he was working as an executive for AT&T, to use 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" caption="Grommes G5M Mixer 1970" >}} {{< 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" >}} 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" >}} At the top of the lower section of the console rack is the first generation Showco stage monitor mixer. This unit took the high impedance tape outputs from the three Grommes G5M mixers and combined them using a resistor network with individual volume controls into the music input of a Grommes G-23 20 watt public address amplifier that we modified to be a line amplifier. {{< TechnicalSpec title="Grommes G-23 Public Address Amplifier" specs="Modified to be a line amplifier with balanced 600 ohm output. Provided master volume for stage monitors and mic input for talkback to the stage." imageId="showco-26-grommes-g23-amplifier" caption="Grommes G-23 Public Address Amplifier 1970" >}} {{< TechnicalSpec title="Processing Rack (Lower Console)" specs="Melcor 8 band graphic equalizer for main speaker stacks and 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" >}} 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 a Led Zeppelin show at the 10,000 seat Memorial Auditorium in Dallas on March 28, 1970. We rented an 18 ft Ryder yellow truck and rolled the new equipment down Maxson’s driveway of his house on W Beverly Drive in Dallas on the new Colson casters to the street and loaded up the truck using the power liftgate on the truck. Zeppelin had started this US tour on March 21, 1970 and had played 6 shows before they arrived in Dallas for the show on March 28, 1970. At that time there were very few sound companies that offered touring sound systems. The local promoter in each city was responsible for hiring a local company to do the sound, and almost all local sound companies had equipment suitable for small meetings or for announcing basketball games. The sound equipment was not designed for the high sound levels of the new rock concerts and as a result the 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 and were blown away with 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 remaining shows on the tour. We packed the Showco equipment back into the Ryder truck, hired Bill Heald, who played rhythm guitar in my band, the now defunct Soul Society, to be my roadie, and we drove off to do the remaining shows on that leg of the 1970 US Zeppelin tour. In hindsight, the bad experience with Leslie West had actually been a blessing, because it motivated me and Maxson to build a really big sound system (for the times) all at once and quickly rather than do it piece meal 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 15,000-18,000 seat hockey/basketball arena was the enabling and essential technology that was 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 and that Led Zeppelin show in Dallas on March 28, 1970 validated our vision and set us on a path for great success in the worldwide entertainment industry. To further validate Showco’s Eureka Moment and put a stamp on it, Terry Bassett called to book the sound system that I was using on Led Zeppelin for a Three Dog Night show at Memorial Auditorium in Dallas on April 26, 1970, a week after the last Zeppelin show on April 19, 1970. I returned to Dallas, and we did the show for Three Dog Night with the new Showco sound system and Maxson operating the system and the same thing happened as with Zeppelin - Three Dog loved the sound and wanted to take the system on the road with them. Maxson hired a roadie and took the system and the Ryder truck and began doing shows for Three Dog Night, becoming their sound engineer for several years. Showco sound was off and running two months after building 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." >}} {{< 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." >}} {{< 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." >}} {{< StoryImage id="showco-044-zeppelin-promo" caption="John Bonham Led Zeppelin 1969. Photo Carl Dunn" size="responsive" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-robert_2_6x9_ls" caption="Robert Plant Led Zeppelin 1969 Photo Carl Dunn" size="responsive" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-zep_2" caption="Jimmy Page Led Zeppelin 1969 Photo Carl Dunn" size="responsive" >}} {{< StoryImage id="showco-carl-dunn-photos-1-unedited-originals-zep_templet" caption="John Paul Jones Led Zeppelin 1969 Photo Carl Dunn" size="responsive" >}} {{< ShowcaseGallery id="carl-dunn-5" title="1970 Led Zeppelin Tour" year="1970" band="Led Zeppelin" >}}