August 14, 1986 Gerald J. Morris Norshor Bldg. Silver Bay, MN 55614 Dear Gerald: Your letter regarding the Bob Dylan/Grateful Dead concert at Minneapolis Metrodome on June 26, 1986 has been forwarded to us for response. We are, of course, concerned about your unhappiness with the concert, and believe you are entitled to an explanation. The Minneapolis Metrodome is a large facility with a pneumatically suspended roof. This was the first concert held there. The Beach Boys played the facility for a baseball crowd following a game, but their performance was in no way comparable to a concert. The building's architecture provides some impediments to sound quality to certain portions of the building, which can only be solved by structural changes to the building's acoustical quality. The pneumatic suspension causes an interior air density of more than one and one-half atmospheres, which impedes the travel of sound through the room. This can largely be overcome by the use of sound reinforcement towers, which were placed 240 feet in front of the stage. Since the sound from the stage ampli fiers travels at the speed of sound, and the electrical impulses to the sound reinforcement towers travels at the speed of light, the towers are timed to < millisecond by sophisticated measuring equipment, so that the sound from the stage amplifiers and from the sound reinforcement towers reaches the remote audience at exactly the same time, giving a larger, clearer sound, which appears to emanate from the stage. The sound engineers obtained architectural drawings of the Metrodome from the Metrodome staff, and the placement of all speakers was determined from the equipment manufacturers' specifications, which experience has proved accurate. Templates showing the reach of the sound are prepared and placed over 1" drawings of the building, so that the sound is precisely placed. Final verifi cation of the sound quality was made with a B &' K Model 2032 Computerized Sound Analyzer, and sound samples were taken on the flat part of the field, in the lower, medium and upper seating sections, and in the side, rear and front. The measurements showed that in small sections of the stadium, there was more than four seconds reverberation time, coming mostly from the ceiling at all angles, which impaired acoustical presence. Grateful Dead BOX 1073, SAN RAFAEL, CA 94915 • TELEPHONE (415) 457-2322
Transcript
August 14, 1986
Gerald J. MorrisNorshor Bldg.Silver Bay, MN 55614
Dear Gerald:
Your letter regarding the Bob Dylan/Grateful Dead concert at MinneapolisMetrodome on June 26, 1986 has been forwarded to us for response. We are, ofcourse, concerned about your unhappiness with the concert, and believe you areentitled to an explanation.
The Minneapolis Metrodome is a large facility with a pneumatically suspendedroof. This was the first concert held there. The Beach Boys played thefacility for a baseball crowd following a game, but their performance was inno way comparable to a concert. The building's architecture provides someimpediments to sound quality to certain portions of the building, which canonly be solved by structural changes to the building's acoustical quality.
The pneumatic suspension causes an interior air density of more than one andone-half atmospheres, which impedes the travel of sound through the room. Thiscan largely be overcome by the use of sound reinforcement towers, which wereplaced 240 feet in front of the stage. Since the sound from the stage amplifiers travels at the speed of sound, and the electrical impulses to the soundreinforcement towers travels at the speed of light, the towers are timed to <millisecond by sophisticated measuring equipment, so that the sound from thestage amplifiers and from the sound reinforcement towers reaches the remoteaudience at exactly the same time, giving a larger, clearer sound, whichappears to emanate from the stage.The sound engineers obtained architectural drawings of the Metrodome from theMetrodome staff, and the placement of all speakers was determined from theequipment manufacturers' specifications, which experience has proved accurate.Templates showing the reach of the sound are prepared and placed over 1"drawings of the building, so that the sound is precisely placed. Final verification of the sound quality was made with a B &' K Model 2032 ComputerizedSound Analyzer, and sound samples were taken on the flat part of the field, inthe lower, medium and upper seating sections, and in the side, rear and front.The measurements showed that in small sections of the stadium, there was morethan four seconds reverberation time, coming mostly from the ceiling at allangles, which impaired acoustical presence.
Grateful DeadBOX 1073, SAN RAFAEL, CA 94915 • TELEPHONE (415) 457-2322
G. MorrisAugust 14, 1986Page Two
We have received relatively few complaints about sound quality, and the concertreceived good reviews. From these factors, plus our own observations, wehave to conclude that few people were inconvenienced. For that reason, we areunable to offer refunds.
In summary,while we strive for perfection and regret anything less,no expenseor effort was spared in attempting to make the Metrodome Concert a pleasurablesound experience for all attending.
7380 Jensen Ave. S.Cottage Grove, Mn. 55016August 18, 1986
Your technical letter of August 14, 1986, did nothingto appease me in regard to the anger and frustrationI have felt as a result of the Dylan/Dead concert atthe Minneapolis Metrodome on June'~:26, 1986. Not onlydid I dislike heing patronized with all your technicallingo on the first page of your letter, hut it wasyour second page that was really the killer. Come onDan, do you really expect me to "believe that you have
.tively few complaints about the soundquality? The letter that I received from the productioncompany responded in a letter to me that they had re-p.pivrH a m /m-RiE nv noMTST.ATTvmng in regards to the soundquality at the concert. I am much more apt to believethem than you. Besides, I heard quite a number ofpeople around me grumbling about the terrible sound.
As for your second point in which you write,"...the concert received good reviews." I would like tochallenge that statement. I subscribe to the St. PaulPioneer Press and Dispatch and the dav after the concertthe paper stated how bad the sound quality at the concerwas. If you need confirmation, I will gladly send youthe article from the paper regarding the concert.^
Third, on page two of your letter you state you are notoffering refunds because, based on your own observations,you concluded that few people were inconvenienced. Whatsort of observations did you make Dan? Were you at theconcert? I doubt that, and even if you were, I highlydoubt you were sitting next to me (the person who waswas also complaining about the sound). Your observationswere biased.Fourth, you write that because so few people wereinconvenienced (your conclusion), you are unable tooffer refunds. What is the problem here, Dan? Ifso few people were inconvenienced, why can't you offerthem a refund? Certainly a refund to a "few people"will not cause bankruptcy for the Grateful Dead.I guess you can tell by now that I was thoroughly disappointed with your response and I will not be satisfieduntil 1 receive a full refund for the price of theticket($20) as well as .880 for postage. I will beforwarding copies of this letter to Rosewood Productionsas well as the Metrodome Commission.
cc: Rosewood ProductionsMetrodome Commission
Sincerely,
Anita M. Kennedy
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Page 2Mr. Jerry BellMetropolitan Sports Facilities CommissionHubert H. Humphrey MetrodomeJanuary 7, 1987
intelligible unless you were directly on axis of one of the high frequencyhorns.
We question whether the interior air density inside the Metrodome is indeedgreater than one and one-half atmospheres. Even given that as fact, it wouldnot "impede the travel of sound through the room". It will attenuatefrequencies above lOKHz which will somewhat affect intelligibility.Temperatures and humidity would have a much greater affect on how the soundtravels through the space.
The real need for delayed sound reinforcement towers is to provide uniformsound coverage and sound pressure levels. Sound levels decrease six decibelseach time the distance from the source is doubled. An example of this is:
Sound level produced by a loudspeaker is specified as 120decibels at 4 feet with full power.
4 ' 1 2 0 d B114dB
1 6 ' 1 0 8 d B3 2 ' l 0 2 d B6 4 ' 9 6 d B
1 2 8 ' 9 0 d B2 5 6 ' 8 4 d B
You can clearly see the need for additional delayed sound reinforcement towersto maintain typical concert sound levels of 115 decibels or greater. TheMetrodome system has been measured at a consistent 101 decibels in the seatingarea with peaking capability of 118 decibels. Delaying the audio signal tothe sound reinforcement towers preserves the presence effect by giving thelistener the illusion that the sound in coming from the source (stage) andalso allows it to arrive at the listener "in time" with the source sound. Ifthis was not done, the listener would hear an echo.
Technology does allow us to computer design sound systems with great accuracy.All of the manufacturer's performance specifications of the loudspeaker areincorporated into the program. The design program allows us to design asystem with uniform sound coverage (plus or minus 3dB within the area is anaccepted practice) and acceptable intelligibility. Intelligibility ismeasured in ALCONS or percent of articulation loss of consonants or mostrecently, in RASTI. Fifteen percent articulation loss of consonants isconsidered maximum allowable for a sound system with nothing greater than tenpercent loss being desired. RASTI equivalents are a maximum of 46 withnothing less than .52 being desirable.
Page 3Mr. Jerry BellMetropolitan Sports Facilities CommissionHubert H. Humphrey MetrodomeJanuary 7, 1987
Both the loudspeaker performance specifications and the room acoustics (reverbtime) are used in calculating the intelligibility of a system. Once thesystem is properly designed, installed and tuned, it should provide uniformsound coverage, uniform frequency response, and intelligible sound. Thisassures all listeners that there are no "dead spots" or "hot spots" in theseating area, that the sound will be natural and pleasing to hear, and thatthey will understand what they hear. I can only assume from Dan Healy'sletter that all of these steps were followed.
The reverberation time referred to as four seconds is a concern and at nine asmeasured, is a real concern. Reverberation time is the length of timemeasured in seconds for the reverberant sound to decay 60 decibels. As wasevident in the previous paragraph, reverberation time is critical in theperformance of a sound system. Also of importance is reflected sound. Goodsound system design practice dictates that no sound be directed toward flatvertical surfaces, creating direct reflections.
Apparently, the major complaint about the concert is that people haddifficulty understanding. Several factors come into play here, including thecoverage. Assuming that a system is designed correctly, a sound engineerdoing the show mix can run the instrument levels high enough above the vocallevels to "bury" the vocals. Thus, a poor mix can be perceived as poor sound.It is my assumption that this was not the case.
Our technician attending the concert observed two major factors that wouldcontribute to poor sound. First, the delayed sound reinforcement towers wereelevated and angled such that sound was being directed onto the front glasssurfaces of the private suites. This created some unfavorable reflections.Second, the power amplifiers were operating in "clip" most of the time. Somemanufacturers install colored indicators on the front panels of amplifiers toindicate to the user that the amplifier is operating in a mode beyond itscapability to produce clean undistorted sound. This is commonly called a clipindicator. Since it was observed that the clip indicators were on, I mustassume that the loudspeakers were receiving a distorted signal.
During construction of the Metrodome, a concert sound system was designed andproposed, but not accepted. By today's standards, neither the fidelity orpower of the system would be acceptable for concert use, but the concept, inmy opinion, remains essentially correct. It included a speaker cluster thatwould be suspended above the stage. A single suspended cluster is always moresuccessful than "stacks". Midway down the field was another cluster on alift. This group of speakers were on an audio delay system. The fieldspeakers were to be used in conjunction with the house clusters through anelaborate delay matrix.
I believe that it is not possible to provide acceptable sound both on the
Page 4Mr. Jerry BellMetropolitan Sports Facilities CommissionHubert H. Humphrey MetrodomeJanuary 7, 1987
field and in the seats, unless the overhead clusters are used. This wouldmean that the visiting sound company and our company would have to workclosely to achieve the optimum result. This would ultimately benefit thecommission and the performer. We have become very familiar with the facilityover the past years with various events and probably understand the soundproblems better than anyone.
In closing, I offer our assistance anytime you consider activities in theMetrodome that require more than the permanent sound system. We need to worktoward a common goal of having the customer feel good about the show and aboutthe facility.
Please do not hesitate to call if you have any questions.
Sincerely,
MTS NORTHWEST SOUND, INC.
Robert ThompsonVice President
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METRODOME COMMISSION STATEMENT
Date: June 26-? 1986
Venue: Bob Dylan., Tom Petty, Grateful Dead show
AFTER TAX GROSSES
OOH 7
Bob Dylan
Tom Petty— c o m b i n e d
Grateful Dead
TOTAL AFTER TAX GROSSES
LESS NON-COMMISSIONABLE REVENUE
COMMISSIONABLE REVENUE
METRODOME PERCENTAGE
NET DUE METRODOME
$ 76 ,081 .94 m,
$_ 1 08,734 .75 i
Nl
1 8 4 , 8 1 6 . 6 9 v 3I E 6 0 , 0 0 0 . 0 0
12 4 .816.69
X 10%
12 ,481 .67
CASH OR CHECK NO /~)//'n
RECEIVED BY
TITLE
February 3, 1986Dennis A l f tonJe r r y Be l lMetro Sports CommissionHHH Metrodome900 South 5th StreetMinneapolis, MN 55415Dear Dennis and Jer.py;"^'"""'
usta np.teto-:-Gon|;r-rm'the' hold we have art-anged for apossible Grateful Dead' and Friends concert foY June 26,1 9 8 6 . \ . /
Our load in would be aTEex^Tn^T^tWTTfyonts on June 24,or early on June 25. The show would be June 26 with an'immediate load out that would have the dome cleared bythree in the afternoon on June 27.
We would have reserved seats on the Dome floor and a Domefl o o r fi r e p r o o f t a r p e l i n . T h e s t a g e w o u l d s i t o n p l y w o o d .
If the show comes together the Grateful Dead Friends wouldinclude Bob Dylan. The show wi l l not be played i f he isunable to perform.
I have explained to the show producer that the Dome isrent free with a 10% Dome tax, and a 6% sales tax. I amassumingthat the 10% tax would cover the costs of power,a i r c o n d i t i o n i n g , c l e a n u p , t r a f fi c p o l i c e , e t c . C h a i r s 'you own, plywood you own, etc.Please give me a call if you see any problems with theabove. I am sending them some Dome photos that we areshoo t i ng . I ce r t a i n l y hope t hey accep t t he s i t e .Best Regards, /~n
I Vf —- XRandy LevyVice Pres\idejit--schonJrrodtjctions, INC
526 Nicollet Mall, Second Floor, Minneapolis, MN 55402/(612) 332-6575
