RPI Playhouse Sound System Design History (Main System, 1983-circa 2016)

In the late 1980’s I was still heavily involved with my college theatre group, the RPI Players. We had a very nice little theatre on campus which had been recently renovated, it reopened in 1983. Due to both budgetary limits and my lack of experience, the primary sound system installed in 1983 was not really adequate to the task. I set about to quantify what was wrong with it, determine how to fix it, and design and implement a new system. As of 2016 that system is still in use, but I have realized that many people do not know how it came to be or more importantly why we made the design decisions that we did. This page is an attempt to document the design process, the decisions and why they were made, and the history of that sound system.

Please note that this writeup only covers the main house sound system. As time permits, I will document my memories of the other aspects of the sound systems at the RPI Playhouse; wireless systems, lobby and back of house systems,  and stage feeds are just a few the come to mind.

1983

As the renovations to convert the 15th Street Lounge into the RPI Playhouse were nearing completion we needed to reinstall the sound system we had removed prior to renovation. During the year that the building was under renovation we decided to upgrade the main sound system in a number of relatively inexpensive ways, we had little money for such things at the time. The previous sound system consisted of a pair of Electro-Voice (EV) Sentry IV horn loaded loudspeakers, a couple Dynaco ST-120 amplifiers, and a Yamaha PM-430 mixer. The new system consisted of the midrange and high frequency horns from the Sentry IV speakers, but we replaced the bass horns with vented boxes utilizing EV EVM-18B drivers. The amplifiers were upgraded to two used Crown D-150A with a home made 2nd order butterworth crossover so we could bi-amp them. Equalization was provided by a pair of Urei 537 27 band graphic equalizers. The mixer was upgraded to a Yamaha MQ-1602. We had two of the speaker systems and they were originally hung near the center of the room. I had a theory that a single center channel speaker would be better for vocal reinforcement, more on this later. After the first production they were moved to conventional left and right positions and the low frequency amplifier was upgraded to a used Crown DC-300A. I left RPI at the end of 1983 and my involvement was limited for a few years.

The people besides myself who were involved in the above designs and implementation were, in no particular order,  Larry Fulton, Joyce Hyde, Ron Swanson, Mark Carline, Ed Falk, and others I am sure I am forgetting.

1983 Equipment List
  • EV Midrange and high frequency horns from Sentry IV with passive crossover, 1 each Left and Right
  • EV EVM-18B drivers in vented boxes, 1 each Left and Right
  • Crown DC-300A amplifier
  • Crown D-150A amplifier
  • Homemade 2nd order butterworts crossover (400Hz.)[note, I still have this little crossover]
  • Urei 537 27 band graphic equalizer, 1 each Left and Right
  • Yamaha MQ-1602 16 channel mixer

1989-1992

In 1985 I moved back to the Troy, NY area and in the Spring of 1989 a friend dragged me back to the RPI Playhouse for The Pirates of Penzance and introduced me to Mike Shannon. Mike and I immediately hit it off and we spent most of the party following closing of the show sitting on the sound booth floor discussing what was wrong with the main sound system and how to fix it. It was that summer that the RPI Playhouse Sound Committee was started by Jim Holmes. We spent many evenings discussing and debating what was wrong and how to fix it. The sound system did not have any real gain before feedback. While the room acoustics are partially to blame, it is an almost square room with all hard surfaces, the sound system was also to blame.

The following year I was Sound Designer for The Threepenny Opera and tried out one of my ideas as to why we had so many problems. I had theorized that the wide horizontal dispersion of the horns (120 degrees) was “spraying” sound against the side walls and creating lots of additional reflections and reverberant field energy. This made the direct to reflected sound ratio unfavorable to intelligibility. To reduce the pattern of the horns (especially the midrange) I found some cotton cloth and carefully stuffed it into the horn, strategically placed to reduce the output aimed at the wall. This became known around the Playhouse as “stuffing underwear in the horns“. It worked to improve the sound and proved my theory that it was the poor direct to reflected ratio that was the root cause of our issues.  If we could just control the pattern of the sound so that it hit the audience and not the walls (or floor or ceiling, but that was asking for a bit too much), then we would greatly improve the intelligibility and perceived gain before feedback.

Now that we knew what we had to do we only had to find suitable equipment that was affordable and budget for it. Sounds simple doesn’t it. We knew we had problems down to at least 250 Hz. so we wanted directional control from 250 Hz. (lower if we could get it) through the top of the audible range. The challenge was the low frequency cabinet. It had to be horn loaded to provide any directional control and maintaining control to 250 Hz. required a large cabinet. Then we found the Klipsch LSI low frequency cabinets. These were a professional version of the consumer La Scala product (still available today). They had directional control to about 250 Hz., but got ragged in response above 400 Hz. The midrange horn driver combination we found, the EV DH1012A driver with HR-6040A horn, had a low frequency limit of 400 Hz. with a pattern of 60×40 degrees. We still needed a high frequency component as the DH1012A rolled off above about 10 KHz. I borrowed a pair of Altec Lansing MR902-16HF, this was a 90×40 degree “super tweeter” designed to operate from 5 KHz. up. The pattern match was not perfect, but we were still working on a shoestring. The EV drivers and horns were used, we traded in the Sentry IV horns to cover some of the cost. For the electronic crossover we managed to get a used Rane AC-23.

We powered the system with a Rane MA-6 amplifier making 100w in each of 6 channels. This amplifier is fan cooled with a 2-speed fan, it rarely stepped up to high speed and when it did, it was so loud in the house already that no one noticed. The MA-6 has built in limiting when you approach clipping and we (Mike Shannon specifically) called the folks at Rane to ask how to dial the limiters on the horn channels down, since they could only handle 50w continuous. The Rane people were very helpful and talked Mike through the circuit so that he could manage the modifications. Rane support was still like that prior to the acquisition by inMusic, I have no idea how their support is today.

We located the MA-6 in the 1st house truss to reduce the length of the speaker cable runs. This change will have an effect on design decisions later on.

As a side note, one of the design goals of the sound system was to get too loud even for Players. Specifically, I wanted to achieve 120 dB SPL throughout the room on average. Starting with this system, every generation of sound system in the Playhouse has been able to achieve that goal. The 120 dB SPL level was chosen so that any rational use of the sound system would not tax it’s capabilities.

About this time we started thinking about a subwoofer or two, but that was to come later.

The people involved this time were, in no particular order, Jim Holmes, Mike Shannon, Tim Shannon, Brian Borchers, Mike Passaretti and others I am forgetting.

Second Sound System Since Renovation
  • Altec Lansing MR902-16HF super tweeters, 1 each Left and Right
  • EV HR-6040A horn with DH1012A driver, 1 each Left and Right
  • Klipsch LSI bass cabinet, 1 each Left and Right
  • Rane MA-6 amplifier, 6 channels @ 100w each
  • Rane AC-23 electronic crossover
  • Urei 537 [no change here]
  • Yamaha MQ-1602 [no change here]

1993-1998

Sound was better, but we still were not happy. We still needed more gain before feedback and we thought the system really needed subwoofers to extend the low frequencies for both music and sound effects. We also knew that the existing 16 channel Yamaha mixer was no longer up to the task at hand. I do not recall the specific order of these improvements, but I know that we had all of them completed by the time I Sound Designed Cabaret in 1998.

The three-way flown systems had to be upgraded to make use of a better horn/driver that could cover 400 Hz. to over 16 KHz. We replaced the HR series “white whale” horns with EV HP-640 horns and DH1A drivers. These are 60×40 degree horns.

We added subwoofers built into the front of the stage. Originally these were 15 cubic foot boxes loaded with EV EVX-180 woofers and had response down to about 23 Hz! There were two of them and they were each driven by a Crown DC-300A bridged to make about 550w. We cooked one of them and after talking to EV (I worked for an EV dealer at the time) we learned that we were seriously under powering them! They were rated for 600w per RS-426A. The EV applications engineer said that we should put about 2,000w behind each one! We bought a QSC EX-4000A amplifier (800w continuous, 1,600w peak) and planned to eventually buy a second and run them bridged, one per subwoofer (which would be 2,400w continuous). We installed an SPL-1 limiter card in it and set it up for subwoofer use and 600w long term. Since installing the EX4000 we have not cooked a sub driver, but …

We did have another interesting driver failure. The voice coil started rubbing. We returned the driver to EV (under warranty) and we got back an EVX-180A, which had a very different suspension (Fs of 29 Hz. vs 20 Hz. for the original EVX-180). Turns out the suspension was too soft and the cone would sag and the voice coil would rub and eventually die. So EV was slowly upgrading them all (under warranty) to the EVX-180A design which would last longer. We had to redesign the cabinets to take better advantage of the new parameters. I cannot take credit for the redesign, that was done by Matt Maessen. He did a fantastic design, reducing box size to 1/2 of what it was originally (one of the unused box halves spent may years as the stand for the chop saw), and utilized a “step down” tuning which got us full output to about 27 Hz. as long as we used the Furman Punch-10 which Matt modified to apply the correct equalization to match his box design. At some point the second EVX-180 failed and came back as an EVX-180A. Both subs have been operating with no failures ever since.

Ever since we moved back into the building in 1983 I thought what we really needed for good, solid reinforcement of vocals was a center speaker. This would reduce reverent field confusion by reducing the number of sources and serve to better localize the image onstage. During this time I got my way and we added a third Klipsch LSI bass bin and mid/high frequency horn. We used the same driver, an EV DH1A, but the horn is an HP-940, a 90×40 degree horn. This differs from the Left and Right which are 60 degree. In the case of Left and Right we wanted less than 90 degrees of horizontal coverage so that we could avoid both hitting the stage and the side wall with sound. For complete coverage of the house from the Center location we needed 90 degrees of coverage, so that is what we used. Joel Lord led the team that hung that Center speaker (I had led team that hung the Left and Right speakers).

We had been planning for a new sound board for years. One of the features that we knew that we wanted was a board that supported the new Center channel. We had not found a board we liked that we could really afford (we had about $15,000 total for the new board and all the parts to make it work). We really liked the Soundcraft Venue II Theatre, but the board alone would have cost all $15K. At the AES convention in NYC in the fall of 1995 I was talking to the DDA rep and described our needs. He told me not to buy anything until after the new product announcements in January. In January 1996 DDA introduced the CS-3 and by Me and My Girl in the Spring of 1996 we had a demo. We ran the show on that demo 16 channel CS-3 and fell in love with it. We were able to buy two short loaded 32 channel chassis for about $12K leaving another $3K for parts, cables, connectors and other odds and ends to actually connect them and make them work. I mixed Cabaret on a CS-3 using the Center channel. After one performance a Players Old Timer came up to me and asked if the sound system was working. I asked if he could hear everything. He said, “Yes, but I could not hear the sound system… oh wait… wow!!!!” We had never been able to mix with that level of precision that the audience could hear the actors without having the sound system be obvious. That night was one of my personal high points in Sound Design and Mixing.

The people involved at this stage of the game were Joel Lord, John Harvey, Jim Holmes, Mike and Tim Shannon, and a host of people learning Sound Design and Designing shows.

Third Generation Sound System Since Renovation
  • EV HP-640 horns for Left and Right [in use as of 2016]
  • EV HP-940 horn for Center [in use as of 2016]
  • EV DH1A drivers on all horns [in use as of 2016]
  • Klipsch LSI bass cabinets for Left, Center, Right [no change LR, add C , in use as of 2016]
  • Rane MA-6 amplifier [no change]
  • Rane AC-23 [no change LR]
  • Rane AC-22 added for Center
  • Furman Punch-10 for subwoofer processing (not crossover)[in use as of 2016]
  • Sabine ADF-4000F PowerQ added for Left, Center, and Right (two units)
  • DDA CS-3 32 channel chassis x2, one for in the booth with 12 stereo inputs and 12 mono inputs, one for FOH with 24 mono inputs and 4 stereo [one of which is in use as of 2016 in the booth]

1999-2005

By this point we were reasonably happy with what the sound system could do. We had good enough gain before feedback to do a very good job mixing a show. Now we were starting to address backend usability issues and making fine adjustments to go from what we needed to what we really wanted.

1999-05-30In 1999 four of us spent the entirety of Memorial Day weekend at the Playhouse ripping out the old patch bays and wiring in the new ones. I was the first to arrive Friday about noon (I had taken the day off) and started soldering up a patch bay. To get the best price we bought patch bays with no wiring attached! We had to solder every single wire in place and dress the bundles so that they would be manageable. By dinner time the core crew of John Harvey, Joel Lord, Jim Holmes, and myself were hard at work. We worked until we needed to eat or sleep, then we did that. Once we were fed or slept we went back to work. 59½ hours after we started we were finally done. This was the only time that year we could take the sound system down for an extended period. We left a note for those who came after us.

One of the flaws we discovered in the original design that placed the house amplifiers in the 1st truss in the house was noise. We used Crown D-series amplifiers for a period before switching to the MA-6. The D-series are all convection cooled with no fans. The MA-6 has a 2-speed fan, running at a very slow speed unless the amplifier chassis heats up. Even at the slow speed the fan is audible in a quiet house. There was lively debate, as with almost all the decisions made by the Sound Committee, as to whether the house was ever that quiet with an audience present. In the end we all agreed that going to convection cooled amplifiers was the best solution, as we could make very good use of the MA-6 in other applications in the building. The replacement of the MA-6 was lead by Joel Lord and the Hafler P-3000 was chosen as the replacement for a number of reasons including being fan free and having the sound quality of a studio monitor amplifier rather than a PA amp.

The march of technology combined with aging of the AC-23 crossover, remember it was used when we go it, had us looking for a a new electronic crossover. We went with two Rane RPM-26z which is a 2 input 6 output DSP based processor. It also has 2 digital inputs and outputs via the AES protocol. The dream was to one day get the AES I/O cards for the Sabines and go from the ADF-4000F to the RPM-26z digitally. Alas, that project was never a high enough priority to see it implemented. I was stunned with the difference in sound quality after the first time we aligned the system with the new processors. The ability to cleanly time align all of the components made an enormous difference in the intelligibility and imaging. I had known that time alignment was important, but this was like night and day. The main sound system really sounded good.

The people involved in the above were: Joel Lord, John Harvey, Jim Holmes, and I am sure I am missing many others. This was a time period where I was not the driving force behind these projects, I was involved as a design advisor and someone with the technical skills to make it happen.

Fourth Generation Sound System Since Renovation
  • EV HP-640 horns for Left and Right [no change, in use as of 2016]
  • EV HP-940 horn for Center [no change, in use as of 2016]
  • EV DH1A drivers on all horns [no change, in use as of 2016]
  • Klipsch LSI bass cabinets for Left, Center, Right [no change LR, add C , in use as of 2016]
  • Hafler P-3000, 1 each for Left, Center, and Right
  • Rane RPM-26z, two, one for Left and Right, and the other for Center
  • Furman Punch-10 for subwoofer processing (not crossover)[in use as of 2016]
  • Sabine ADF-4000F PowerQ [now used as patchable processors where needed]
  • DDA CS-3 32 channel chassis x2, one for in the booth with 12 stereo inputs and 12 mono inputs, one for FOH with 24 mono inputs and 4 stereo [one of which is in use as of 2016 in the booth]

2006-circa 2016

The need for more channels to handle more complex shows lead to a project to replace the DDA consoles. At the time of the purchase the biggest question was whether to stay analog or go digital. Digital had lots of appeal for a number of reasons, but it was still more expensive to get a digital console with a fully featured user interface than a comparable analog console. We were looking at Soundcraft MH-2 or MH-3 and Allen and Heath ML-3000 and ML-4000 in the analog realm. I do not recall what we were looking at in terms of digital, but then Soundcraft introduced the Si-1/Si-2/Si-3 series as a lower end version of the Vi-series. The Si-3 did what we needed and we could almost afford it. We ran one of the first alumni fund raising campaigns specifically for this purchase.

Once again the march of technology has driven a change in the main processing. The Rane RPM-26z have been replaced in the main house feeds with a Rane HAL-1x, the RPM-26z have been repurposed for effects and backstage processing.

I know that this section is light on details, but I have not been directly involved in the decision making process for a number of years. I would love to update this with more details, but I need them from the people involved at the time.