Electro-Voice EVF-1151S, EVF-2121S, EVH-1152S, EVF-1122S, EVH-1152D User Manual

EVF/EVH

User Manual

EVF-1121S

EVF-1151S

EVF-1181S

EVF-2121S

EVF-2151D

EVF-1122S (All Patterns)

EVF-1122D (All Patterns)

EVF-1152S (All Patterns)

EVF-1152D (All Patterns)

EVH-1152S (All Patterns)

EVH-1152D (All Patterns)

Electro-Voice EVF/EVH User Manual

Table of Contents

Rigging-Safety Warning...........................................................................................................................................................................................					3
1.0	Introduction .........................................................................................................................................................................................................				4
	1.1	Finishes and Colors Available.........................................................................................................................................................			9
	1.2	EVF Front-Loaded Series.................................................................................................................................................................			9
	1.3	EVH Horn-Loaded Series................................................................................................................................................................			9
	1.4	Accessories for EVF and EVH Systems.....................................................................................................................................			10
2.0	Tool List	.......................................................................................................................................................................................................			10
3.0 Designing an EVF/EVH Cluster .................................................................................................................................................................					11
	3.1	General Aiming and Placement Guidelines..............................................................................................................................			11
	3.2	Choosing between the EVF Full-Range and EVH Full-Range Systems............................................................................			11
		3.21	Directivity Break Frequency Defined........................................................................................................................		11
	3.3	More on Coverage Patterns, Multiple Coverage Patterns, the Need for Clusters of
		Loudspeakers and How Far a Single Cluster Can “Reach” into a Venue..........................................................................			12
		3.31	Basic Clustering Guidelines.......................................................................................................................................		12
	3.4	Coverage-Uniformity Target..........................................................................................................................................................			13
	3.5	Multiple-Source Interference in Clusters...................................................................................................................................			14
		3.51	Reducing Multiple-Source Interference...................................................................................................................		16
4.0	Preparing EVF and EVH Systems for Installation....................................................................................................................................				19
	4.1	Recommended Preflight Procedures.........................................................................................................................................			19
	4.2	Passive/Biamp Crossover Configuration..................................................................................................................................			19
	4.3	Rotation of High-Frequency Waveguides (EVF Systems).....................................................................................................			20
	4.4	Rotation of High-Frequency Waveguides and Mid-Frequency Waveguide
		Contours (EVH Systems)..............................................................................................................................................................			20
	4.5	Digital Signal Processing..............................................................................................................................................................			21
		4.51	Full-Range Systems in Passive Mode......................................................................................................................		21
		4.52	Using the EVF-1121S and EVF-1151S Low-Frequency Systems in Full-Range
			Clusters that Operate on a Single Power-Amplifier Channel.............................................................................		22
		4.53	DSP (Digital Signal Processor) Loudspeaker Presets for Biamp Operation.................................................		22
5.0 EVF and EVH Rigging System.....................................................................................................................................................................					23
	5.1	Introduction.......................................................................................................................................................................................			23
		5.11	The Flying EV-Innovation (EV-I) Loudspeaker System.........................................................................................		23
		5.12	Important Details that Apply to the VRK and HRK Rigging Kits.......................................................................		26
	5.2	EV-I Rigging Primer........................................................................................................................................................................			26
		5.21	Anatomy of an EVF or EVH Flying System Using M10 Eyebolts.......................................................................		27
			5.211	Eyebolt Application Warnings..................................................................................................................	27
			5.212	Eyebolt Installation......................................................................................................................................	28
			5.213	All-Eyebolt Clusters...................................................................................................................................	29
		5.22	VRK Kits and Vertically Rigged Clusters.................................................................................................................		31
		5.23	HRK Kits and Horizontally Rigged Clusters...........................................................................................................		32
		5.24	Assembly Instructions for VRK and HRK Kits........................................................................................................		35
6.0	Rigging-Strength Ratings and Safety Factors..........................................................................................................................................				37
	6.1	Working Load Limit and Safety-Factor Definitions...................................................................................................................			37
	6.2	Structural-Rating Overview...........................................................................................................................................................			38
	6.3	All-Eyebolt Structural Ratings......................................................................................................................................................			39
		6.31	Working Load Limits for Eyebolts.............................................................................................................................		40
		6.32	Suspension-Line Angles.............................................................................................................................................		41
		6.33	Left-to-Right All-Eyebolt Cluster Angles.................................................................................................................		41
	6.4	VRK Rigging Structural Ratings for Vertical Clusters.............................................................................................................			42
		6.41	Working Load Limits for Eyebolts used with VRK Vertical Rigging Kits..........................................................		44
		6.42	Left-to-Right Vertical Cluster Angles.......................................................................................................................		45
2				Electro-Voice EVF/EVH User Manual

Table of Contents (cont’)

6.5	HRK Rigging Structural Ratings for Horizontal Clusters.......................................................................................................		46
	6.51	Using Tie Plates as Main Load-Bearing Suspension............................................................................................	47
	6.52	Suspension-Line Angles for HRK Kits.....................................................................................................................	48
	6.53	Symmetry for Horizontal Clusters using HRK Kits................................................................................................	49
	6.54	Inner Connection Points..............................................................................................................................................	50
	6.55	Left-to-Right Horizontal Cluster Angles..................................................................................................................	50
6.6	Ratings for Outdoor Applications with Wind Loading............................................................................................................		51
6.7	Electro-Voice Structural-Analysis Procedures..........................................................................................................................		51
7.0 Rigging Inspection and Precautions...........................................................................................................................................................			52
8.0 References ......................................................................................................................................................................................................			53
8.1	Rigging (Printed).............................................................................................................................................................................		53
8.2	Mechanical Engineering (Printed)...............................................................................................................................................		53
8.3	Rigging (Websites).........................................................................................................................................................................		53
Notes..........................................................................................................................................................................................................................			54

Rigging-Safety Warning

This document details general rigging practices appropriate to the entertainment industry, as they would apply to the rigging of Electro-Voice EVF and EVH loudspeaker systems. It is intended to familiarize the reader with standard rigging hardware and

techniques for suspending EVF and EVH loudspeaker systems overhead. Only persons with the knowledge of proper hardware and safe rigging techniques should attempt to suspend any sound systems overhead. Prior to suspending any Electro-Voice EVF and EVH loudspeaker systems overhead, it is essential that the user be familiar with the strength ratings, rigging techniques and special safety considerations outlined in this manual. The rigging techniques and practices recommended in this manual are, of necessity, in general terms to accommodate the many variations in loudspeaker clusters and rigging configurations. As such, the user is expressly responsible for the safety of all specific EVF and EVH loudspeaker cluster designs and rigging configurations as implemented in practice.

All the general rigging material contained in this manual is based on the best available engineering information concerning materials and practices, as commonly recognized in the United States, and is believed to be accurate at the time of original printing. As such, the information may not be directly applicable in other countries. Furthermore, the regulations and requirements governing rigging hardware and practices may be superseded by local regulations. It is the responsibility of the user to ensure that any Electro-Voice loudspeaker system is suspended overhead in accordance with all current federal, state and local regulations.

All specific material concerning the strength ratings, rigging techniques and safety considerations for the EVF and EVH loudspeaker systems is based on the best available engineering information concerning the use and limitations of the products. Electro-Voice continually engages in testing, research and development of its loudspeaker products. As a result, the specifications are subject to change without notice. It is the responsibility of the user to ensure that any Electro-Voice loudspeaker system is suspended overhead in accordance with the strength ratings, rigging techniques and safety considerations given in this document and any manual update notices. All non-Electro-Voice associated hardware items necessary to rig a complete EVF and EVH loudspeaker cluster (chain hoists, building or tower supports and miscellaneous mechanical components) are the responsibility of others.

Electro-Voice

June 2010

Electro-Voice EVF/EVH User Manual

3

1.0 Introduction

The Electro-Voice EVF series is a group of compact two-way front-loaded full-range systems, available with 12or 15-inch woofers, augmented by low-frequency and subwoofer systems. EVF full-range systems are available in two versions. The “S” versions employ 400-watt SMX low-frequency transducers and the ND2B medium-format, 1.4-inch exit/2-inch diaphragm compression driver. The “D” versions employ 500-watt DVX-A low-frequency transducers and the DH7N large-format, 1.4-inch exit/3-inch diaphragm compression driver. Both compression drivers have neodymium magnetic structures. In general, the premium components in the “D” versions provide lower distortion and reduced power compression.

The EVH series is a group of larger two-way horn-loaded full-range systems. Both the “S” and “D” EVH versions use SMX low-frequency transducers. The “D” versions substitute the DH7N large-format compression driver for the ND2B medium-format driver.

All full-range systems utilize high-order crossover networks that seamlessly integrate the low-frequency transducers with the high-frequency compression drivers, providing very low distortion and excellent frequency response.

The EVF/EVH systems have many threaded rigging points that can be used with the supplied eyebolt kits or optional suspension kits to easily create a number of horizontal or vertical cluster configurations. All enclosures in their normal orientations (long axis vertical) share the same height, just over 30 inches (762 mm), promoting attractive clusters. Six coverage patterns, all rotatable, are available in each family, as shown in Table 1a. The EVF-1121S and EVF-1151S low-frequency systems have integral low-pass filters that allow paralleling them with up to two full-range systems, offering a cost-effective way to augment the low-frequency output of EVF full-range systems.

Horn Pattern:	40° x 30°	60° x 40°	60° x 60°	90° x 40°	90° x 60°	90° x 90°	120° x 60°
EVF 12-inch		•	•	•	•	•	•
EVF 15-inch	•	•	•	•	•	•
EVH	•	•	•	•	•	•

Table 1a:

Coverage patterns available in the EVF and EVH series (all rotatable)

The model number scheme denotes the number of woofers, the diameter of the woofers, the number of band passes in the system, the woofer series used and, following a forward slash, the coverage pattern. An example is the EVF-1122S/96, which has a single SMX series 12-inch woofer in a two-way configuration and a 90° x 60° pattern. Another example is the EVF-1181S subwoofer, which has a single EVS-18S 18-inch woofer in a “one way” configuration and without a specific coverage pattern (essentially omnidirectional in the very-low-frequency range in which it is usually operated).

4	Electro-Voice EVF/EVH User Manual

1.0 Introduction (cont’)

	Model Name		EVF-1122S/96 (example)
	(As Shown)
	Model Name	EVF	-	1	12	2	S	/	96
	(Separated)
		Loudspeaker		Number of	Woofer	Number of	Woofer		Coverage
	Description	Family/Series		Woofers	Diameter	Band Passes	Series Used		Pattern
		(EVF Series)		(1 Woofer)	(12-inch)	(Two-Way)	(SMX Series)		(90° x 60°)

Table 1b:

Model number scheme, showing the meaning of each individual model number

Typical EVF and EVH systems are shown in Figure 1, with key dimensions, suspension points, weights and centers-of-gravity. Engineering data sheets for each model, containing full specifications and dimensional drawings, are shipped with each loudspeaker and are downloadable from the Electro-Voice Web site (www.electrovoice.com).

“S” System Weight - 60.0 lb (27.2 kg)

“D” System Weight - 65.5 lb (29.7 kg)

End View

Front View

Side View

Rear View

Figure 1a:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-1122 (all coverage patterns)

“S” System Weight -

70.1 lb (31.8 kg)

“D” System Weight -

75.7 lb (34.4 kg)

End View	Front View	Figure 1b:	Side View	Rear View

Key dimensions, suspension points, weight, and center-of-gravity for EVF-1152 (all coverage patterns)

Electro-Voice EVF/EVH User Manual

5

1.0 Introduction (cont’)

System Weight -

57.7 lb (26.2 kg)

End View

Front View

Side View

Rear View

Figure 1c:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-1121S

System Weight -

62.6 lb (28.4 kg)

End View Front View Side View Rear View

Figure 1d:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-1151S

System Weight - 101.2 lb (46.0 kg)

End View Front View Side View Rear View

Figure 1e:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-1181S

6	Electro-Voice EVF/EVH User Manual

1.0 Introduction (cont’)

System Weight -

82.4 lb (37.4 kg)

End View Front View Side View Rear View

Figure 1f:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-2121S

System Weight - 117.0 lb (53.1 kg)

End View Front View Side View Rear View

Figure 1g:

Key dimensions, suspension points, weight, and center-of-gravity for EVF-2151D

“S” System Weight -

“D” System Weight -

143.0 lb (64.9 kg)

145.5 lb (66.1 kg)

End View	Front View	Side View	Rear View
		Figure 1h:

Key dimensions, suspension points, weight, and center-of-gravity for EVH-1152 (all coverage patterns)

Electro-Voice EVF/EVH User Manual

7

1.0 Introduction (cont’)

Washer (x4)

Eyebolt (x4)

Figure 1g:

Key dimensions for washers and eyebolts included with each loudspeaker

End View

Side View

Rear View

Figure 1h:

Key suspension point dimensions for EVF or EVH loudspeakers as indicated in table below

Dimension:	A	B	C	D	E°
EVF 12-inch	4.176” [106.07mm]	14.301” [363.24mm]	N/A	16.129” [409.67mm]	15°
EVF 15-inch	4.176” [106.07mm]	14.301” [363.24mm]	N/A	18.353” [466.16mm]	15°
EVF Subs	3.957” [100.50mm]	13.889” [352.77mm]	23.857” [605.97mm]	28.255” [717.68mm]	10°
EVH	3.957” [100.50mm]	13.889” [352.77mm]	23.857” [605.97mm]	26.409” [670.79mm]	10°

Table 2:

Key suspension point dimensions as shown in figure above

8	Electro-Voice EVF/EVH User Manual

1.0Introduction (cont’)

1.1Finishes and Colors Available

The standard EVF/EVH indoor versions are finished in tough EVCoat™. In addition, all models are available in two levels of weather resistance, indicated by letters following the coverage-pattern numbers. The FG versions, e.g., EVF-1152S/64-FGB, are designed for full weather exposure and feature a fiberglass-fin- ished enclosure, stainless-steel hydrophobic grille and the CDG dual-gland-nut input-panel cover. The PI versions, e.g., EVF-1152S/64-PIW, are rated for indirect outdoor exposure only in protected areas, such as under a roof overhang, and feature a stainless-steel hydrophobic grille and CDG dual-gland-nut inputpanel cover on an enclosure finished in standard EVCoat. External fasteners on all systems are stainless steel.

All EVF and EVH systems are available in black or white. Black is indicated by BLK or B at the very end of the complete model number and white is indicated by WHT or W at the very end of the complete model number, e.g., EVF-1152/94-BLK and EVF-1152S/94-PIW.

1.2 EVF Front-Loaded Series

Note that engineering data sheets with complete specifications are packed with each system and downloadable at www.electrovoice.com.

EVF-1122S/64, EVF-1122S/66, EVF-1122S/94, EVF-1122S/96, EVF-1122S/99, EVF-1122S/126, EVF-1122D/64, EVF-1122D/66, EVF-1122D/94, EVF-1122D/96, EVF-1122D/99, EVF-1122D/126: two-way 12-inch full-range systems with six different rotatable waveguides ranging from 60° x 40° to 120° by 60°, as detailed in Table 1.

EVF-1152S/43, EVF-1152S/64, EVF-1152S/66, EVF-1152S/94, EVF-1152S/96, EVF-1152S/99, EVF-1152D/43, EVF-1152D/64, EVF-1152D/66, EVF-1152D/94, EVF-1152D/96, EVF-1152D/99: two-way 15-inch full-range systems with six different rotatable waveguides ranging from 40° x 30° to 90° by 90°, as detailed in Table 1.

EVF-1121S: 12-inch low-frequency system.

EVF-1151S: 15-inch low-frequency system.

EVF-1181S: 18-inch subwoofer system.

EVF-2121S: Dual 12-inch low-frequency system.

EVF-2151D: Dual 15-inch subwoofer system.

1.3 EVH Horn-Loaded Series

Note that engineering data sheets with complete specifications are packed with each system and downloadable at www.electrovoice.com.

EVH-1152S/43, EVH-1152S/64, EVH-1152S/66, EVH-1152S/94, EVH-1152S/96, EVH-1152S/99, EVH-1152D/43, EVH-1152D/64, EVH-1152D/66, EVH-1152D/94, EVH-1152D/96, EVH-1152D/99: two-way 15-inch full-range systems with six different rotatable high-frequency waveguides ranging from 40° x 30° to 90° x 90° and mid-frequency waveguide contours, as detailed in Table 1.

Electro-Voice EVF/EVH User Manual

9

1.0 Introduction (cont’)

1.4 Accessories for EVF and EVH Systems

Note that some accessories are supplied with certain system versions, as noted.

CDG: optional dual-gland-nut input-panel cover to protect the input connections from water. Note that this cover is supplied with the weather-resistant versions.

CSG: optional single-gland-nut input-panel cover to protect the input connections from water.

CDNL4: optional input-panel cover equipped with dual Neutrik Speakon® NL4M connectors, providing a quick-disconnect alternative to the standard Phoenix screw-terminal input connectors.

HRK and VRK: a series of horizontal (HRK) and vertical (VRK) rigging kits that accommodate a number of horizontal and vertical system aiming angles. See section 5.0 EVF and EVH Rigging System for details.

TK-150: optional 70.7/100-volt transformer kit mounts on the inside of the EVF and EVH input panels, offering 37.5, 75 and 150 watts at 70.7 volts and 75 and 150 watts at 100 volts. Installation instructions come with the TK-150.

EVF-UB: optional U-bracket kit for mounting single EVF full-range and low-frequency (not subwoofer) systems to a wall or ceiling. Installation instructions come with the EVF-UB.

EVI-M10K: optional eyebolt kit, consisting of four M10 shoulder eyebolts and four fender washers, used when additional eyebolts are needed to suspend loudspeakers. See section 6.3 for details. One EVIM10K eyebolt kit is supplied with each loudspeaker system.

EVI-AC: optional access card which allows diagnostic access to the transducers and protection circuitry inside the enclosure. Use of this accessory does not require any disassembly or disconnections beyond removal of the plug-in switch card.

2.0 Tool List

Listed below are the tools required to prepare EVF and EVH systems for installation:

1.3/16-inch flat-blade screwdriver (for attaching signal wires to input-panel connectors).

2.Phillips #2 screwdriver (for grille removal to rotate waveguides, removal of high-frequency waveguides for rotation, and removal of input panel to install the optional TK-150 70.7/100-volt transformer).

3.4-mm Allen (hex) wrench (for removal and reorientation of the EVH hard foam mid-frequency waveguide contours to rotate the mid-frequency coverage pattern).

4.6-mm Allen (hex) wrench (for working with all rigging points).

10	Electro-Voice EVF/EVH User Manual

3.0Designing an EVF/EVH Cluster

3.1General Aiming and Placement Guidelines

Loudspeakers should be “pointed at the people” and away from reflective room surfaces. Since people are excellent absorbers of sound and room surfaces are often not, this practice insures not only that the audience will receive the high frequencies necessary for good voice intelligibility and musical clarity but also that the reflective surfaces do not energize the room with intelligibility-robbing reverberation.

Loudspeakers for sound reinforcement are usually located high above a stage or platform and aimed down and out into the audience. This minimizes the difference between the longest throws to the rear of a venue and the shortest throws to the front rows, promoting coverage uniformity. Note that the typical portable loudspeaker on a short, 6-foot stand cannot duplicate such uniformity since the distant seats are so much farther away than the front rows. The direct sound from a loudspeaker drops 6 dB every time the distance from it doubles, according to the formula:

Level loss (dB) = 20log10(closest distance/farthest distance).

See comments on the audibility of different dB differences in section 3.4 Coverage-Uniformity Target.

3.2 Choosing between the EVF Full-Range and the EVH Full-Range Systems

When the reverberation time of a room (formally called T60 and the time it takes sound, once the source has stopped, to decay by 60 dB) exceeds 2-2.5 seconds at mid frequencies, the horn-loaded EVH series should be used. The EVH’s low-frequency horn mouth is large enough to control the rated coverage pattern down to 500 Hz, which promotes clarity by keeping more sound off of reflective surfaces than can the smaller, 12-inch-square horns and direct-radiating woofers of the EVF series. This concept is explored in more detail below.

3.21 Directivity Break Frequency Defined

Below a certain frequency, the mouth size of a waveguide is no longer large enough to maintain the nominal coverage angle and the coverage angle gets wider and wider as frequency is decreased. The frequency at which this occurs is called the “directivity break frequency” (fb) and is inversely proportional to the size of the waveguide mouth and the nominal coverage angle of the waveguide. The directivity break frequency can be approximated by the following formula:

fb (Hz) = 1,000,000/[angle (degrees) x dimension (inches)].

Electro-Voice EVF/EVH User Manual

11

3.0 Designing an EVF/EVH Cluster (cont’)

3.3 More on Coverage Patterns, Multiple Coverage Patterns, the Need for Clusters of Loudspeakers and How Far a Single Cluster Can “Reach” into a Venue

The coverage patterns or angles mentioned previously are defined where loudspeaker output is 6 dB down from maximum, usually on-axis level. In order to help cover only the absorptive audience with sound, given different trim heights and the wide variety of venue shapes, the EVF and EVH series are offered in the many coverage patterns listed in Table 1 (above). Even with this wide choice, it is relatively unlikely that a single loudspeaker will cover the audience uniformly. Therefore, two or more loudspeakers are often assembled into clusters and aimed in different directions in order to reach the entire audience.

3.31 Basic Clustering Guidelines

The aiming angles of systems in a cluster are related not only to room geometry but also to the particular coverage patterns selected. A rough design can be based on the plan and elevation views of a room, representing the loudspeakers by the angles of their horizontal and vertical coverage patterns, e.g., 60° x 40°. A wide or “short throw” coverage pattern, such as 120° x 60°, is good for aiming down into the front rows of a rectangular venue to reach all of the seats left to right. Narrower patterns, such as 60° x 40° and

40° x 30°, are appropriate as “long throw” devices that send sound to the rear of the audience without also “blasting out” the front rows.

Sophisticated software is also available, which allows the designer to build a room model and place and aim loudspeakers within it, assessing the uniformity of coverage. An example is EASE 4.2 (Enhanced Acoustic Simulator for Engineers), developed by Acoustic Design Ahnert (www.ada-acousticdesign. de). EASE is available from the Bosch Communications Systems/Electro-Voice technical support group; specific contact information can be found at www.electrovoice.com. EASE loudspeaker data for EVF and EVH systems may be downloaded at www.electrovoice.com.

A common practice is to widen the horizontal coverage of a single loudspeaker by placing two systems side by side and aiming them in such a way that their horizontal patterns do not overlap. Individually, each system will be 6 dB down at the overlap point. Together at the overlap point, they will sum coherently to the 0-dB on-axis level. A specific example is two 60° horizontal systems clustered together with their axes placed 60° apart.

If these two systems are “underlapped,” with, say, their axes 75° apart, the overall coverage angle will be wider but the level near the array axis will drop. If the two systems are overlapped to any great degree, e.g., their axes only 45° apart, the overall coverage angle will be reduced and the interference discussed in section 3.5 Multiple-Source Interference in Clusters will be worsened.

The degree to which long-throw devices can extend the region of uniform coverage is limited. A single loudspeaker will typically “reach” to the rear a distance that is about twice that of the distance to the closest front row. See Figure 2.

12	Electro-Voice EVF/EVH User Manual

3.0 Designing an EVF/EVH Cluster (cont’)

Figure 2:

Typical “reach” of a single loudspeaker into a venue (DI ) in order to maintain the desired ±3 dB coverage is about two times the distance to the closest seats (DS )

Adding a long-throw device will typically extend this reach to about three times the closest distance. See Figure 3.

Figure 3:

Adding a long-throw device extends the reach to about three times the distance to the closest seat

For reaches beyond this, loudspeakers can be suspended over the audience, with their signal delayed with respect to the front or source loudspeakers so that the sound image will appear to come from the front of the room. The details of these design tips are beyond the scope of this manual and should be left to experienced design personnel.

3.4 Coverage-Uniformity Target

A good uniformity target is ±3 dB throughout the audience area, particularly in the 2,000and 4,000-Hz octave bands, the bands most important for intelligibility. Such coverage should also be achieved in the 8,000-Hz band, important for “sparkle.” As a reference, a 1-dB level difference is nearly imperceptible, a 3-dB difference is noticeable but not a large change, a 6-dB change is clearly noticeable and a 10-dB change is twice or half as loud. The ±3-dB uniformity target is related to these perceptual differences.

Electro-Voice EVF/EVH User Manual

13

3.0 Designing an EVF/EVH Cluster (cont’)

3.5 Multiple-Source Interference in Clusters

Whenever two or more sources serve a single venue, some seats will receive strong signals from multiple sources. Consider two EVF-1122S/64 60° x 40° systems clustered side by side with their axes 60° apart to form a 120° x 40° cluster. If these systems maintained their rated coverage patterns into the lowfrequency range, there would be essentially no interference. But the 12-inch-square waveguides used in the EVF series will begin to “balloon out” at about 2 kHz and below, an effect discussed in Section 3.21 Directivity Break Frequency Defined, above.

On the axis of the cluster, the output of both systems sums perfectly, since the listener is equidistant from each system and the output of both reaches the listener at the same time. This is the axis-of-cluster line shown in Figure 4. If the listener moves to the left (as viewed in the figure), the left loudspeaker will be closer and the sound will arrive sooner. At some angle and at some frequency, the time difference will be equivalent to reversing the polarity of one signal, causing a complete cancellation of cluster output at that frequency.

Figure 4:

The two loudspeaker sources sum perfectly only on the axis of the cluster (as shown); to the left and right of this axis, distance differences produce arrival-time differences that cause cancellation of some frequencies (see text for more details)

14	Electro-Voice EVF/EVH User Manual

3.0 Designing an EVF/EVH Cluster (cont’)

This effect is shown in the frequency-response of Figure 5. Given the dimensions of the typical compact loudspeaker systems and when they are clustered in close proximity to one another, the first several interference nulls occur right in the middle of the vocal range. A frequency response with these ever-more- closely spaced nulls is known as a “comb filter” response, after the visual appearance of the response.

NORMALIZED

Figure 5:

Typical response off the array axis of the two loudspeakers shown in Figure 4, showing cancellations due to arrival-time differences

If one of the null frequencies is chosen and the horizontal polar response is measured, the result is shaped like the blue polar response in the center lower graph of Figure 6. In this view, the cluster axis points up (+X). Full output is achieved on this axis, since both signals arrive at the same time. But there are off-axis problems. While the overall coverage of the cluster is about 120° (6 dB down), two deep nulls occur at about 20° on either side of the cluster axis.

Figure 6:

Horizontal polar response (blue center plot) of two closely clustered 60° x 40° loudspeakers aimed 60° apart, showing the off-axis nulls at 1,250 Hz caused by multiple-source interference

(see text for more details)

Electro-Voice EVF/EVH User Manual

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3.0 Designing an EVF/EVH Cluster (cont’)

At higher frequencies, the interference patterns become more densely packed, which essentially eliminates their audibility. Figure 7 shows this effect at 8,000 Hz.

Figure 7:

Horizontal polar response (blue center plot) of two closely clustered 60° x 40° loudspeakers aimed 60° apart, showing multiple, densely packed off-axis nulls at 8,000 Hz caused by multiple-source interference (see text for more details)

3.51 Reducing Multiple-Source Interference

Multiple-source interference cannot be eliminated but it can be substantially reduced. Systems which have radiating devices large enough to hold their rated coverage angles down to relatively low frequencies, such as the horn-loaded EVH series that hold their coverage angles down to 500 Hz, will exhibit less interference in clusters. Also, doubling the distance between the two systems of Figure 8 produces multiple interference nulls which are more densely packed than those of Figure 6, reducing the audibility of the interference.

Figure 8:

Horizontal polar response (blue center plot) of two 60° x 40° loudspeakers aimed 60° apart but with double the distance between grille centers compared to Figures 6 and 7, showing the more densely packed 1,250-Hz off-axis nulls caused by multiple-source interference (see text for more details)

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3.0 Designing an EVF/EVH Cluster (cont’)

One clustering technique that accomplishes this separation without putting a physical space between two full-range systems is putting a low-frequency or subwoofer system between two full-range systems. Such a cluster is shown in Figure 9, assembled with the optional HRK rigging kits.

HRK-2 Kit

(Sold Separately)

HRK-2 Kit

(Sold Separately)

EVF Full-Range

System

	EVF Subwoofer
Note: Loudspeakers
are non-specific and	EVF Full-Range
shown as an example.	System

Figure 9:

A way of separating two full-range loudspeakers to reduce the audibility of multiple-source interference by separating them with a subwoofer (see text for more details)

Electro-Voice EVF/EVH User Manual

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