The Unique Acoustics of 'Bluegrass Underground's' Performance Space

by Michael S. Eddy
in Features
Bluegrass Underground's Volcano Room. Photo by Michael Weintrob.
Bluegrass Underground's Volcano Room. Photo by Michael Weintrob.

House engineer Andy Kern and Lonely Dog Productions owner Tony Cottrill on the non-televised gigs staged within the PBS Bluegrass Underground venue, the Volcano Roomxt

A truly unique room — naturally beautiful and with amazing acoustics — makes a memorable music venue. The Volcano Room, a venue that seats 600, is the home for a popular radio and television series Bluegrass Underground, as well as a variety of non-televised concerts each month.

What makes a concert in the Volcano Room truly unique is the fact that it is 333 feet below ground in rural Tennessee? It is, in fact, a cave, located in the Cumberland Caverns in McMinnville, TN, where Bluegrass Underground has been running since 2008. The series started out on radio for the first two years, and it’s been on both radio and TV since 2010. It now runs on most PBS stations across America. [In 2018, Bluegrass Undergrounde concerts will be moving to another cave system. See related story, below).

Cave acoustics limit the need for sound reinforcement.

The producers also put on non-televised concerts in the Volcano Room — some under the Bluegrass Underground banner and some billed as Live from the Underground — that are just for the audiences in the cave. (Some of these non-televised shows are broadcast via radio as well.)

In this majestic setting, these productions celebrate the power of music to bring people together. The show prides itself in offering fans a wide variety of genres and has featured such artists as Vince Gill, Del McCoury, Widespread Panic, Jason Isbell, Rhonda Vincent, Amos Lee, Lucinda Williams, Steve Earle, David Grisman, Edward Sharpe and The Magnetic Zeros, Doyle Lawson, Lee Ann Womack, Leon Russell and Old Crow Medicine Show.

There are never any weather-related surprises (or wind) in this cave, and RF interference from outside sources aren't an issue.

‡‡         The Cave Concept

The Volcano Room and Cumberland Caverns were “discovered” by producer Todd Mayo in the summer of 2008 when he proposed the simple idea of producing live performances in a cave. The inaugural show featured The SteelDrivers with Chris Stapleton on lead vocals and, since that August day, the event has grown into a worldwide phenomenon, drawing music fans, media attention and cave buffs from around the globe.

Most of the concerts use a small house audio package, but there are times when the artist requires more gear. Then, Andy Kern, house engineer, brings in a supplemental audio package for those acts. “I’m the house engineer and handle front of house, monitors and record some of the monthly shows for remix for a radio show at a later date,” explains Kerns. “We do roughly two shows a month plus some special events — a Halloween special, New Year’s and one-off shows. As far as the PBS series, which we shoot in one three-day session, I’m the audio producer for Bluegrass Underground as well as the post production remixer.”

While many might think that supporting and capturing audio in a cave would be hard, you might be surprised to find that other than a few minor challenges — like getting your equipment into the cave through long and sometimes very tight passages — working that deep underground has a variety of benefits. The natural shape of the cave creates exceptional acoustics. “The cave has a very unique and diffuse sound that is different than you would expect,” comments Kern. “There isn’t a lot of extreme echo or delay due to the fact that there are no parallel surfaces in the cave. The cave is also a constant 56 degrees F. with 98 percent humidity, meaning once your front fill, sub and out fill delay times are set in the morning, they will be exactly the same in the evening; there’s no chasing temperature and humidity changes all day. Also, there’s NO wind!”

Kern works with artists and their teams on their audio requirements. “We get sent all the usual advance stuff ahead of time and we just kind of work back and forth,” he comments. “When the house system doesn’t meet what they need or require, we look at whether we need to bring in a console, or some extra wedges, to make it work for them. We do all that during the advance process.” Once the artists get into the caves, then Kern and production works with them to get the stage set and make sure that they are comfortable. “We work through sound check, just like any other show,” Kern continues. “We make sure that everyone is happy.”

Three RCF HDL10-A are stacked atop a single RCF SUB 8006-AS sub per side.

‡‡         A Unique Environment

Even though the artists and their team know they will only bring a scaled back version of their show in the cave, it is hard to understand the space until they actually arrive. “They know that they’re going to leave half or more of their production gear on the truck,” comments Kern. “They don’t need a video wall; trusses of lighting; and all sorts of gear so they leave a lot of that back on the truck. Instead of doing two 4x10 cabinets, they’ll use a little 2x12 instead; they’ll scale back in that way as well. Even being told and knowing in advance it requires scaling back, some of them are still a little surprised when they show up and see the space itself. It is a very unique venue. We work with the artists and they work with us to find the right balance of gear because we all have the same goal. We always want to get them set up so they’re comfortable and have a good performance.”

Tony Cottrill and his company, Gallatin, TN-based, Lonely Dog Productions, works closely with Kerns and the Cumberland Caverns team to provide the right additional equipment to supplement the house audio system as needed. “The small house rig consisting of a Yamaha LS9 console, a small monitor and mic package and two JBL Eon speakers,” Kern explains. “Tony and Lonely Dog provides additional audio equipment and support for some of the monthly concerts and Live From The Underground radio concerts that require more equipment. We were looking for a compact system with low power consumption that wouldn’t require bringing in extra feeder and a distro. The entire RCF PA that they bring in runs off just two 20-amp Edison circuits.”

With 98 percent humidity, there is a challenge to keep the equipment dry, which Cottrill and his team have solved. “To keep the gear dry, we cover the RCF rig with bags or plastic sheeting and leave the amps and power on to allow the heat from the electronics to help drive out the moisture. There are some benefits unique to the cave that go hand-in-hand with great acoustics, which Cottrill highlights. “Luckily it is far enough underground that there is zero interference from outside RF/TV signals, that helps any wireless mic or IEM systems run cleanly,” he comments. “Also, there isn’t any outside audio interference like street noise or air conditioning that we have to deal with.” There’s also another huge benefit, which would make any venue manager or producer happy. “Being inside a cave, we’ve never had to cancel a show due to inclement weather,” laughs Cottrill.

Cottrill adds his thoughts on the cave’s acoustical properties. “You can explain the acoustics in that room to people, but it really still surprises people when they experience it,” he says. “The acoustics are really good because there’s obviously no parallel surfaces and the reverb is very controllable. We’ve still got something like three four seconds, but it’s very contained in there. The first time some of the FOH engineers come in they’ll crank it up to rock ‘n’ roll volume, and it just hurts. The room has such natural acoustics and you get the sound of the drum kit and the guitar amps coming off the stage and what you want to do is you just kind of blend the mics into the acoustics rather than make the microphones do all the work, like you would in a typical show.”

“Andy’s a master at this; he’s been mixing that room for eight years, and he’s just got it down. He knows how to mix it, and he knows how to help bands scale back and still have everything they need, especially when you know how hard it is to get gear in there,” Cottrill says, referring to the logistical reality of getting the gear in and out via trailers pulled by Gators utility vehicles down into the Volcano Room.

RCF ST12-SMA’s are used for monitors.

‡‡         Logistics and Load-Ins

“There’s no pulling up at the dock,” Cottrill notes. “There are a few low spots, so we have to be careful how high the cases are stacked and which side of the trailer we put them on. I’ve got a Soundcraft Vi3000 console, a pretty big framed digital desk. You can’t put it on its wheels in that cart and take it down there. You have to lay it down on its side, and we’re pretty much ducking down, driving all the way in there. It’s really a neat experience getting the gear in and working there. We have taken grand pianos in, but we really try to get everyone’s head wrapped around the idea of a more scaled-down show.”

When artists and their teams come in, the house crew helps them get a cave feel. “You don’t want it to have an arena feel,” says Cottrill. “You don’t want to be putting up truss; you don’t have this massive lighting rig; and you don’t want to have massive P.A., drum and keyboard risers. Here the bands come in and they’re setting up on the dirt floor. We stack the P.A., we don’t fly it in there. This is for sightlines and because you don’t want the audience’s attention to be on production; you want the attention to be on this artist, performing in this cave.”

The connection between Kern and Cottrill goes back to when Kern was a student under Cottrill when he taught audio production around the Nashville area. “When I started working with Andy in support of Cumberland Caverns, Lonely Dog was only about a year old,” says Cottrill. “I’ve been an educator most of my life as well as touring at the same time. Eventually, I decided to open my own rental company.

“Andy saw an article about a show that I supported in Nashville, and that I was an RCF dealer. He was very interested in the RCF boxes, because each box only draws about 1.3 amps, and they’re so water resistant; they could stand up to the damp in the cave. Andy called me and said that he ‘had a show the next day, would I bring some gear down for it?’ I loaded up my trailer with all this gear and drove it down to Cumberland Caverns.

“I didn’t know what I was getting into, but I got to show him what the gear was all about and started a work relationship from there,” Cottrill continues. “He started renting gear for the different shows, and I’ve been working with them a couple of years. Sound Image does the audio support for the once-a-year three-day taping of the Bluegrass Underground PBS shows. While my Lonely Dog Productions work on all the other shows, the production’s are not televised, though a lot of the shows we work on are taped for radio throughout the year.”

The power and cabling is very straightforward, as all the power is in the cave; plus, proper planning is essential to a good production. Wally Bigbee is the house electrician. “They have a great team there with Wally and Andy. Being in a cave, there is not much room for error; your gear better be well-maintained and prepped prior to loading-in,” notes Cottrill. “There’s no going back to the shop once you’re 300-plus feet underground.”

For Cottrill, it is the special acoustics of the venue that you find which continues to inspire artists and audiences. “Because the venue is so unique and has a naturally low noise floor, we get to see great artists really play with the dynamics of their show with this environment,” he says. “It creates moments where you can hear a pin drop, even with 600 people in the audience.”

RCF HDL10-A and ST12-SMA speakers handle outfill and frontfill duties.


Bluegrass Underground Finds a New Cave

The PBS shows will relocate from the 600-capacity Volcano room (pictured here) to a 1,000 capacity cave at the base of Monteagle Mountain in Tennessee.

Bluegrass Underground will be leaving the Volcano Room behind for the 2018 season as the production has found a new, permanent home in The Caverns, located within the base of Monteagle Mountain in Tennessee’s Cumberland Plateau.

Also boasting natural acoustics, the new cave location is larger, and the plan calls for permanently installed production gear. It can accommodate close to 1,000, vs. the Volcano Room’s capacity for about 600, a boon not only for Bluegrass Underground but for other live music concerts, as the producers keep expanding the genres of music that they present in the cave.

As many as 50 performances are projected for 2018, expanding the “underground experience” to include symphonic music, comedy shows and some yet-to-be-announced underground surprises.

“This is a dream come true to find a cave system that expands and improves the live and televised musical experiences of underground performances we have been curating since 2008,” said Bluegrass Underground creator and executive producer, Todd Mayo, noting enhanced food and beverage concessions planned for the new space along with installed lighting and sound gear.

The Caverns’ enhancements will greatly benefit the Bluegrass Underground PBS series as well, says television producer Todd Jarrell. “In the past, we taped the entire 12-episode season over one weekend due to the difficulty and expense of bringing literally tons of cabling and show gear a quarter mile into the cave,” explains Jarrell. “But The Caverns permanent infrastructure presents us the flexibility to match calendars with some of the world’s greatest performers, enticing them underground to offer our fans a ‘deep down’ lifetime experience throughout the year.”

The Caverns located in Grundy County near Pelham, TN, at the base of Monteagle Mountain is just 10 minutes off Interstate 24’s Exit 127. The Caverns is 30-minutes closer to two of its major markets: Nashville and Chattanooga — only 75-minutes from Nashville and 45-minutes from Chattanooga.

“Bluegrass Underground is now far more easily accessible to the vast majority of our regional patrons as well as our national and international fly-in fans,” adds Joe Lurgio, the show’s general manager and associate producer, noting the ability for  Bluegrass Underground to now be more accessible to patrons with physical disabilities.

The Caverns adjoin a number of connected cave systems that have long drawn interest from spelunkers for their beautiful formations, vast rooms, winding underground rivers and pristine natural condition. Most of the cave systems on the property are slated to remain accessible to qualified cavers.

“In time, we’d like to sustainably develop and share portions of these amazing caves for both educational and recreational purposes,” Mayo added. “We are so excited to present music in our own magical space for an experience that truly represents the Bluegrass Underground family and brand.”