HomeMy WebLinkAbout7.1 Council Chamber Sound System -�0
CITY OF DUBLIN
AGENDA STATEMENT
CITY COUNCIL MEETING DATE: August 27, 1990
SUBJECT: Council Chamber Sound System
(Prepared by: Paul S. Rankin, Assistant City Manager)
EXHIBITS ATTACHED: Exhibit 1 : Sketch A - Window of Acceptance for Low
Profile Microphones
Exhibit 2: Sketch B - Proposed Mechanical Mute Button
Exhibit 3: Shure Automatic Microphone System Catalog
Description
RECOMMENDATION: Receive the Report and if the City Council concurs with
the Contractor's recommendations, select one of the
microphone options, authorize Staff to proceed. Approve
a Budget transfer from the Contingent Reserve. Authorize
Staff to negotiate for the sale of any unused Pyramid
microphones at a value of not less than $50 each.
FINANCIAL STATEMENT:
Modifications as Proposed by Contractor
Install Modular Connection $108.47 per position $1 , 193.17 for 11 locations
Install Mute Button $ 72.38 per position 796.18 for 11 locations
Rewire to mixer & tune system (flat charge) 275.00
TOTAL Modifications $2,264.35
Micro Phones: Select one option, the purchase will be made in accordance
with the City's purchasing ordinance. Prices shown are estimates. All
pricing is based on a quantity of 11 unless otherwise noted:
Option A: (Gooseneck w/stand) $3, 190
Option B: (Probe w/stand) $2, 640
Option B1 : (Probe w/stand - based
on a quantity of 7 microphones
& 9 stands:The City already owns
4 microphones & 2 desk stands $1 ,720
Option C: (Lavalier) $2, 695
Retrofit of four Pyramid Type Microphones
These would be retrofit for use in the Regional Meeting Room. The cost would
be handled on a time and materials basis not to exceed $300.
DESCRIPTION: Based on concerns raised at City Council meetings, Staff
has had an independent audio firm evaluate the public address system.
Overview of System Installed
The system is made up of components manufactured by Shure. The entire system
is from their automatic microphone system (AMS) line of products.
Tile AMS system is designed to solve problems typically encountered with a
multiple microphone installation. The microphones are "direction-sensitive"
and are designed to turn on only when they are addressed within a 120 degree
window. (See Exhibit 1 ) When the system is operated in the automatic mode,
and more than one microphone is used simultaneously, the gain level will
automatically adjust to help avoid feedback. The system is also connected
directly to a tape recorder, which provides a clear record of the meeting.
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COPIES TO:
Steve Loweree, Maintenance Superintendent
John McKeon, CBC
ITEM NO.
i
Audio/Visual Contractor Review
Staff contacted Coast Business Communications (CBC) of Livermore to review
the installation. This firm is a Shure Dealer and has experience with the
installation of City Council Chamber audio visual equipment at other
locations. This firm is primarily involved with the supply and installation
of equipment.
Current Microphones Conflict with Dais Design
The low profile pyramid shaped microphones are currently mounted in front of
a 3-4 inch backboard which forms the front wall of the dais. CBC believes
that part of the problems encountered result from sound bouncing off the back
wall and into the back of the microphone. As shown in Exhibit 1 , the "Window
of Acceptance" is in the front 120 degrees of the microphone. This design is
intended to allow the microphone to amplify only sound coming from in front
of it, which typically would be the speaker. If the microphone is picking up
sound from both the front and the back, it considers this to be "noise" and
it is not broadcast. Normally, if the microphone was receiving sound in both
the front and back, the source would be outside the "window, " such as someone
to the side who was speaking.
Current Momentary Mute Switch
Currently, each position has a button mounted under the desk top, which when
depressed will turn off the individual microphone. The original design
specifications included the momentary type switch , which requires a person
to hold the button to keep the microphone turned off. The location of the
button makes it awkward to operate this feature.
The Consultant has determined that the current wiring of the momentary mute
button has defeated a key feature of the system. As noted earlier, the AMS
system is capable of turning on a particular microphone only when it is
addressed. The momentary mute button has been wired with all microphones in
the "on" mode. They are only turned off when the button is depressed.
The impact of having all microphones in the "on" position is that the system
operates extremely inefficiently. The system loses approximately 3 decibels
of gain for each microphone which is in the "on" position. This means that
the gain must be turned up which increases the likelihood of feedback and a
hollow ringing sound. With the automatic feature working only those which
someone was speaking into would be in the "on" position.
Audio Contractor Recommendations
CBC has made specific recommendations which would improve the operation of
the system and also provide additional flexibility.
1 . Currently, the microphones are wired directly back to the mixer.
Microphone jacks were not installed at the dais, however, they are available
at several wall locations and at a floor outlet. i
The Contractor has recommended installing a jack at each location on the
dais. This would provide a convenient method of connecting the preferred
microphone. This also provides flexibility in maintaining the system in the
event that a microphone malfunctions.
The cost of making this modification would be $108.47 per microphone. This
modification would be proposed for the 11 seated positions at the dais.
2. CBC has recommended that a mute button be installed on a stainless steel
plate adjacent to the connection jack described in item 1 above. The word
"MUTE" would be engraved on the plate. The button would be mechanical and
would change colors when it is activated. (See Exhibit 2) The Contractor has
experience installing this type of switch in other Council Chambers.
The mute button provides each individual position with the ability to silence
their microphone when they are not participating in the discussion. This
provides a convenient way to avoid having the microphone pick up the rustling
of papers or other background noises. Also, this would be convenient at
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Staff locations where the person typically only participates in the
discussion when a report is presented. The different color of the button
also reminds the speaker that their microphone is muted. This will also
correct the problems which are currently being experienced by having all
microphones wired in the "on" position.
Due to the limited spacing around the dais if a microphone is not muted, it
may be capable of picking up sounds from either side. As shown on Exhibit 1 ,
the microphone will pick up sounds from a wide angle. In order to be assured
that the individual would be close enough to the microphone, Staff believes
that it is important to have a separate microphone at each position.
The cost of performing this modification would be $72.38 per location,
provided that it is undertaken at the same time as recommendation number 1 .
3. After completing the above items, the City could select from three
microphone types. The options presented (Exhibit 3) will avoid the current
conflicts with the dais design. In addition, all of the options will allow
the microphone to be moved closer to the speaker. This should improve the
sound quality since individuals sit different distances from the microphones.
Also, if a member of the audience could not hear a particular individual, the
speaker could move closer to the microphone.
The options available are as follows:
A. Goose Neck Microphone:
This would be similar to the microphone at both the Staff and the
audience speaker locations. Instead of being mounted, the microphone
would be attached to a black desk stand heavy enough to resist tipping.
B. Probe Microphone On Desk Stand:
This option involves a standard microphone on a stand. Staff will have
this type of microphone available to review at the City Council meeting.
C. Lavalier Microphone
This microphone is worn loosely around the neck. This provides the user
with mobility and it also assures that the microphone is within optimum
distance from the speaker.
Cost of Replacement Microphones
The cost of replacement microphones with stands is estimated to range between
$240 - $290 per microphone depending on the type selected.
Estimated Cost
Gooseneck with Stand $290
Probe Microphone with Stand $240
Lavalier Microphone $245
The potential to obtain a credit for the existing microphones would depend on
whether the Contractor had other jobs which would find this equipment
acceptable. The salvage value in this situation is estimated at
approximately $50 per microphone. Staff would also accept possible bids from
other firms in order to obtain the highest value.
It may be possible to retrofit four of the existing pyramid type microphones
for use in the Regional Meeting Room. This would involve replacing the cord
with a jack type plug which could plug into the wall outlets currently
located in that room. One could also be permanently mounted to the movable
podium in that room. Although the exact details of the work have not been
specified, the Consultant estimates that these modifications could be
undertaken for a total of approximately $300. Staff would recommend that
this be undertaken on a time and materials basis not to exceed $300.
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i
SUMMARY OF RECOMMENDED CHANGES
The costs and options have been summarized under the financial section shown
on the first page of the Staff report.
As shown in Option B1 (Financial Section) , the cost of purchasing microphones
could be reduced if the City used the 4 probe style microphones provided with
the original system. These were intended to be used in the Regional Meeting
Room, Supplemental Staff Seating Area behind the Staff at the Dais, and at
the audience location. If these four microphones are incorporated into the
modified system, the City will only need to purchase 7 microphones. This
would provide a savings of approximately $920.
Staff proposes to have the materials and services noted under System
Modifications provided by CBC with a one-year warranty. Staff would propose
that the City purchase the microphones and any stands directly from a vendor,
based upon the City's Purchasing Ordinance. Staff would discuss further with
the Contractor, the modification of Pyramid microphones on a time and
materials basis for use in the Regional Meeting Room. This work would not
exceed $300.
Conclusion
Staff recommends that the City Council:
(1 ) Receive the report. (2) Review the proposed modifications. (3) If it is
found acceptable, authorize Staff to work with CBC to pursue the system
modifications. (4) Select a microphone option and any stands required with
the new configuration. (5) Authorize a transfer from the Contingent Reserve
in the following amounts: $2,575 to General Building Dept 105 - Contract
Services and $1 ,720 - $3, 190 to General Building Dept 105 - Furnishings and
Equipment. The range presented reflects the need to determine the quantity
and type of microphones to be purchased.
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BASIC SETUP: THE MICROPHONES
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MICROPHONE
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AMS26
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MIGROPki0N
WHAT TO DO HOW TO DO IT
S. In general,place the talker within the front acceptance 6. Sound sources outside the shaded acceptance angle
angle of the microphone. will not turn on the microphone. See diagrams 6A
through 60.
7A. If the chairs are 3 feet or less from each other, use 7A. Place each microphone a foot and a half from the table
one microphone between each pair of seats. edge, helWy between the two seats
7B. If chairs ere more than 3 feet from each other,use one 78. Place each microphone a foot and a half from the table
microphone per seat, edge, directly in front of the talker
8. Remove any objects immediately behind the 8. The grille of an AMS26[probe]or AMS24[gooseneck]
microphones that may reflect sound. microphone should be at least 8 inches above any table-
top. [The A26X Extension Tube inserted between the
swivel adgpter and desk stand will raise the AMS26 an
additional 3".] Remove ob cts behind AMS22 micro-
phones.
EXHIBIT �--
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Fe Clear Plastic
Black Shroud
Orange button
Position 1 Position 2
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% C�flIBIT
Automat 1- c Microphone smu'm
System
AMS System AMS Microphones
The Shure AMS automatic microphone system is a dedicated, AMS22 AMS Low-Profile Microphone
totally integrated system consisting of complementary mixers ,Phis surface mounted microphone is styled to be unobtrusive
and microphones that work together to solve the most on a table surface. Supplied with nondetachable 20'cable,
aggravating problems associated with multiple microphone with a male XLK connector.
installations. The AMS system features direction-sensitive _
microphones that turn on automatically only when ad- AMS26 AMS Probe Microphone
dressed within their own 120° "window of acceptance." Each The AMS26 is designed for conventional swivel-adapter
microphone continuously samples its own local acoustic stand mounting,with front pop-filter grille. When mounting
environment,and automatically compensates for changing on a desk stand,the AMS26 grille must be at least 8"above
room conditions. Advanced microphone,mixer,and logic the table surface for optimum results. Not supplied with mic.
technology enable the AMS to turn on to the sound source
quickly,quietly,and automatically. When more than one
microphone is activated simultaneously,the system provides
automatic gain compensation to prevent annoying feedback.
a
Key Features
• Microphones turn on and off smoothly,reducing muddy
sound and feedback
• Direct output on each channel connects to multi-track AMS 26 '
tape recorders for detailed sound recordings AMS 22.
• All mics act independently when turned on or off
• Advanced logic terminals provide flexibility in expanding AMS24 AMS Gooseneck Mounted Microphone
the system's capabilities Same as the AMS26,but mounted on matte black gooseneck,
• Microphone flexibility:surface mount,lavalier,or with 20'attached cable. Comes with mounting flange.
lectern/stand use
AMS28 AMS Lavalier Microphone
AMS Mixers The AMS28 is worn around the neck,giving the wearer
AMS4000 Automatic 4-Channel Mixer mobility during a presentation. Unit is supplied with 20'
This 4-channel mixer has these key features:channel LED
nondetachable cable with 3-pin male XLK connector.
indicators light when mic turns on;microphone gain control
with mic off position;master level control; 1/4"auxiliary
inputs with level control;1/4"headphone jack;overload LED
lights when Line/Mic,Aux,and phones approach clipping;
jacks to link up to 25 AMS mixers;hold time switch deter-
mines how long a mic stays on after speaker stops talking;
line/uric level output;four female XLK AMS mic inputs;and
direct 1/4"line out from each mic channel
Dimensions:3-1/2"1-1 x 19"W x 11-3/4"D.
AMS8000 Automatic 8-Channel Mixer
Same as AMS4000,with 8 AMS mic inputs. AMS 80110 AMS 24 AMS 28
um 71
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Accessories
r
f. �' } C25E Mic cable,25',black XLR at mic end,
chrome XLK at equn ment end
C50J Mic cable,50',chrome XLK connectors
NOTE:Please call for coarplele infornratiorr on all accessories for
• • ® Y Y • R the Shure Autornalic Microphone System.
158 Institutional and
grmnfily pricing available PHOTO & SOUND COMPANY
1' ' -6
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