Electro-Voice PRO-8A User manual

Speaker Systems for
Background Music and Paging
Technical Guide
Installed Sound
TA-2
Version 1.2
April, 2002
Distributed loudspeaker systems for paging and background music are
among the most important “bread and butter jobs in sound contracting. In
most cities, new restaurants, hotels, health clubs and clinics are continually
sprouting up. Each one has needs that can be met by a distributed system,
and each represents a potential client for the enterprising contractor.
The overwhelming majority of paging and background systems are relatively
small, however. With the margin on many installations running in the $400
to $600 range, there’s not much room for error or misunderstanding, since
the cost of a single callback can eat up most of the profits. To succeed with
distributed sound systems, the professional contractor needs to be able to
count on his jobs going in smoothly and efficiently.
In this article, we’ll explore some of the “nuts and bolts” issues that affect
profitability in the distributed sound system market, and offer suggestions
for improving your chances of success in the business.
The Site Survey
Every system specification begins with a survey of the site. The sales
engineer, whose job is to ask the right questions and gather all the
information necessary to complete an accurate bid, normally performs the
survey.
At this stage, it is most important to form an accurate picture of the
customer’s needs. Will the system be used for paging, background music, or
both? Do pages originate from a single location, or from multiple locations?
Must the system be tied into the customer’s telephone network? Should the
system be divided into multiple zones with separate volume controls? If so,
should pages be routed to all zones, or should zones be separately
addressable? Should zone controls be located at the rack, or is local control
required? The answers to questions like these will determine major aspects of
the system design.
Talking to individual users of the proposed system will help to flesh out
important design details. Is the maitre d’hotel’s station located directly under
a speaker? If so, then an independent local volume control should be
provided for that speaker, so that it can be adjusted to allow conversation

Speaker Systems for Background Music and Paging page 2
Electro-Voice Installed Sound Technical Guide
with patrons. Will the person issuing pages be sitting under or near a
speaker? If so, then consider equalization, or a separate muting circuit, to
avoid feedback. Is light-switch height a comfortable location for zone
volume controls, or does the user have another preference? Getting this kind
of information at the beginning will help to avoid confusion and delays at
the installation stage.
Just as important as the human factors are the construction details of the
site. How are the walls and ceilings constructed? What kinds of mounting
surfaces will be encountered? Is the drop ceiling a lay-in type, or tongue-
and-groove? Where must cabling be routed, and how accessible are those
spaces? Do partition walls or bearing members extend above the drop
ceiling, where they may obstruct cable runs? Is conduit or plenum cable
required? All of these factors directly affect the price quote and the actual
task of installation.
Defining The System
Upon completion of a thorough site survey, the system may be specified and
quoted. The sales engineer also usually generates the design and quote, often
at the same time as the site survey. Success at this stage depends experience
and product knowledge.
To avoid ambiguity and confusion at the installation stage, the specification
needs to be as explicit as possible. Of course, it should enumerate all of the
equipment proposed to do the job, and should include both a block
diagram and an accurate floor plan with annotations regarding construction.
In addition, it should provide details such as local volume control locations
and height, the desired location for amp racks, and even names of the
employees who are expected to use the system. To forestall disputes and
clarify responsibility if changes are required during or after installation, the
customer should be asked to sign a written agreement governing the
specification.
Many contracting companies simply communicate the sales engineer’s
design directly to their installation department, who are charged with
putting the system in and making it work. There are potential problems
with this approach. For example, the salesman’s natural tendency is to over-
design and oversell when he can. If the client is amenable, the result can be
an excessively complicated (and problematic) system. Moreover, it is easy to
make mistakes in the flush of a sale, and these may be compounded when
the system goes in.
©2002 Telex Communications, Inc.

Speaker Systems for Background Music and Paging page 3
Electro-Voice Installed Sound Technical Guide
To address such pitfalls, it makes good sense to have each proposal reviewed
by a second engineering employee whose approval should be required before
the specification goes to installation. At this stage, design details can be fine-
tuned and potential problems can be addressed to assure that the design is
feasible, efficient and free of unnecessary redundancy.
Selecting and Positioning Loudspeakers
In the traditional approach to overhead-distributed systems, loudspeakers are
located in a grid arrangement whose dimensions are dictated by the room
height and the directivity of the speaker elements. Two basic placement
patterns prevail: square spacing, and hexagonal (or crisscross) spacing.
In addition to the spacing pattern, the designer must choose between three
density types, designated respectively as edge-to-edge, minimum overlap and
center-to-center. The greater the overlap, the more uniform the coverage—
and the higher the cost. Budgetary constraints tend to favor sacrificing
density, so the optimum center-to-center configuration is, in practice, the
least common of the three.
Ceiling Speaker Size
System designers usually specify 8-inch cone loudspeakers for distributed
overhead systems, at least in part because they represent the traditional
choice. In many cases, however, you can achieve equal or better results—at a
significant savings—by using 4-inch elements. Characterized by somewhat
smoother frequency response and less susceptibility to feedback than 8-inch
elements, 4-inch units are also generally less expensive and offer a real
advantage in directivity.
Of course, a 4-inch unit will typically be somewhat less sensitive than a
comparable 8-inch. For equivalent motor assemblies, the difference is on the
order of 3 dB. The 4-inch will also have slightly reduced low-frequency
capabilities.
Expect The Unexpected
The distributed sound system market is highly competitive and margins are
small. It makes good sense to do everything you can to avoid problems at
the installation stage and to be ready to handle callbacks or last minute
changes smoothly. One way to do this is to anticipate problems before they
occur and build contingency plans into your operation.
For example, you should always have some inexpensive “fixes” at the ready.
Say that the customer decides to change his floor plan at the last minute,
©2002 Telex Communications, Inc.
Read more about
EV®ceiling speakers.
Ceiling speakers
data sheets:
205 Series 4”
405 Series 4”
EP405 Series 4”
EP407 Series 6.5”
PRO-8A Series 8”
209 Series 8”
309 Series 8”
409 Series 8”
EP 309 Series 8”

Speaker Systems for Background Music and Paging page 4
Electro-Voice Installed Sound Technical Guide
requiring you to add another zone to the system. Electro-Voice offers the
MA/MR series of rack-mount or shelf-mount mixer/amplifiers, receivers and
power amplifiers that enable you to offer a painless quote for the requested
change, and come out a hero. You can even avoid the additional cost of
installing a volume control in the new zone by putting the amplifier on a
shelf in the zone.
Similarly, it may make sense to pull a couple of extra cable pairs (both
speaker lines and mike lines) when making your home runs. That way, if
there’s a base that wasn’t covered in the specification, you can make it up
onsite. The practice also facilitates expanding the system at a later date.
Be sure that the floor plans you use are up-to-date, and keep
communications open with the client. Particularly if you are limited to
using existing wiring, you need to know if the client’s plans for space usage
will remain the same. Otherwise, you may end up with a real headache—
like having the emergency room announcements directed to the pediatric
ward
Finally, it is vitally important to be sure that you know who in the client’s
company is authorized to make decisions when questions arise on the job
site. If the building manager tells your installers to put the amp racks in the
basement you don’t want the owners calling you and insisting that they
should have been in the second floor office
Standardizing for Profitability
One of the best strategies that we can recommend for success in contracting
is to standardize your operations wherever possible. Settle on a few basic
system designs that can be modified to cover a wide variety of circumstances
and then educate your sales staff about them. Develop standard pricing
calculations, in cost per hour, for all of the basic labor items: putting in a
can, pulling a cable pair, installing a plenum run, and so on. Rather than
trying out a new, whiz-bang esoteric product on each installation, stock a
carefully selected complement of proven performers and use them
consistently. Often you can achieve significant savings by reducing the
number of suppliers whose products you use. When you use several
suppliers, you encounter differing lead times, minimum order quantity
requirements, freight policies and payment terms that complicate your
ability to respond quickly and consistently to demands from your customers.
These are “hidden” overhead costs that compromise your ability to generate
a profit.
©2002 Telex Communications, Inc.
Read more about
MA/MR Series
amplifiers:
MA-1005B
MA-355B
MA-605B
MR-355C receiver