Electro-Voice Model 30W Woofer
The Electro-Voice Model 30W woofer is a significant advancement in bass speaker design, offering unparalleled low-frequency performance. This is achieved through a combination of a substantial magnet structure, a heavy-duty, edgewise-wound copper voice coil, and a rigid polystyrene foam cone. A one-piece, diecast aluminum frame ensures permanent component alignment while minimizing weight. The unit features a 9 lb. 4 oz. ceramic magnet within a 23 lb. magnetic circuit, constituting over two-thirds of the total unit weight.
To accurately reproduce the impact of instruments like the pipe organ and bass drum, high acoustic power is necessary due to reduced ear sensitivity in the low-frequency range. Acoustic power output is directly proportional to the cone's radiating area. The 30W, with over 500 square inches of cone area, provides a significant increase in radiation resistance, enabling unprecedented performance in the extreme bass range, even at full power input with the cone motion remaining within the linear range.
Specifications
- Resonance: 15 Hz ± 3 Hz
- Impedance (Nominal): 8 ohms
- Impedance (Minimum): 5 ohms
- DC Resistance: 4 ohms
- Power Handling Capacity (RMS): 60 watts
- Power Handling Capacity (Pulsed): 150 watts
- Conversion Efficiency: (See Figure 6)
- EIA Sensitivity Rating: 10%
- Recommended Crossover: 54 dB
- Voice Coil Diameter: 100 Hz
- Magnet: 2 1/2 inches, 9 lb. 4 oz., ceramic
- Dimensions: 29 7/8" dia., 13-13/32" depth behind wall
- Net Weight: 34 pounds
- Baffle Opening: 28 1/2 inches
- Mounting: 6-3/8" holes equally spaced on 28-7/8" circle
Enclosure Design
The enclosure is critical to the performance of the 30W woofer. Recommended enclosures are sealed (acoustic suspension) types; ported (bass reflex) enclosures are not necessary or desirable. Key factors influencing performance include:
- Enclosure volume
- Damping material
- System environment
- Mass loading
Enclosure Volume
Figure 1 illustrates the relationship between enclosure volume and speaker resonance. Figure 2 provides representative response curves under anechoic conditions. For instance, enclosure volumes of 22, 50, and 300 cubic feet result in speaker resonances of 40 Hz, 30 Hz, and 20 Hz, respectively. Smaller enclosures with higher resonance tend to be underdamped, causing a rise in the response curve at resonance. An optimal response curve is approximately 3 dB down at resonance. The effect of damping is broad; curves C and E represent an enclosure volume ratio of 13:1. Adjusting these variables allows for precise tuning of the system's response.
Acoustic Damping Material
Underdamped speakers can be compensated using acoustic resistance within the enclosure. Fiberglass insulation is an effective and inexpensive damping material. Removing any paper or foil backing before insertion and filling the enclosure until the fiberglass is slightly compressed can reduce resonant frequency by up to 10% and increase damping.
System Environment
The placement of the speaker significantly impacts its performance. In large, open areas away from reflecting surfaces, performance approximates free-field conditions. Placing the speaker against a solid wall, at a wall junction, or in a corner (1/2, 1/4, or 1/8 space conditions) contains low-frequency energy, leading to a rise in bass response. In large spaces, a slightly underdamped curve may be preferred. Conversely, close reflecting surfaces boost low frequencies, making an overdamped (rolled-off) free-field curve more suitable, achievable with a larger enclosure and/or fiberglass damping.
Mass Loading
When enclosure volume is limited, mass loading can lower resonant frequency at a slight cost to efficiency. This technique is used in the Patrician 800 system. A simple method involves facing the speaker towards a rigid surface, like a wall (Figure 3). As the speaker moves closer to the wall, the effective mass of air in front increases, lowering resonance by up to 25%. However, if sufficient cabinet space is available, a conventional approach is preferred over mass loading.
Figure 1: Enclosure Volume vs Resonance
Enclosure Construction
Cabinet wall vibrations, being out of phase with the woofer cone, can cancel some of the woofer's output. While a concrete block enclosure is ideal, it is impractical. One-inch plywood walls braced with 2x4 sections offer a good compromise for reducing panel vibration with manageable weight, cost, and construction ease. Bracing should not exceed 24-inch spacing in any direction. Sixteen-inch spacing is convenient for layout and provides greater panel rigidity. Joints should be secured with wood glue and nails, except for removable access panels, which should use screws. Removable panels can be sealed with closed-cell foam tape or non-drying caulking compound.
Unlike many enclosures, lining the interior walls with fiberglass is not necessary to absorb standing waves, as the low frequencies of standing waves in 30W cabinets are unaffected by wall lining. Adding fiberglass does alter the response curve by lowering system Q and reducing the amplitude of internal standing waves.
Mounting the 30W in a wall may require removing a stud. Structural rigidity can be maintained with a header and sill above and below the speaker (Figure 4). For convenience, the 30W can be secured to a plywood baffle screwed to wall studs. Consulting an architect or builder before proceeding with wall mounting is highly recommended.
Figure 4: Wall Mounting
Connections
For installations where the 30W is close to the crossover and other components, No. 18 wire (like lamp cord) is sufficient. If the distance is greater, use No. 16 or larger wire to minimize resistance losses.
Electro-Voice Model X1835 and Model X1020 crossovers are designed for the 30W woofer. The X1835 is for Patrician components, while the X1020 allows integration into existing full-range systems. The recommended crossover frequency is 100 Hz.
To ensure maximum bass response, perform a phase-reversing test during installation. Play audio with significant content below 100 Hz (e.g., organ music) and reverse the woofer connections. The connection that yields better bass response is the correct one. If no difference is apparent, either connection is acceptable. This test accounts for potential cancellation near the crossover frequency due to speaker spacing and room acoustics.
Customer Service
The 30W is packaged to exceed shipping requirements. If shipping damage occurs, contact the carrier or dealer for inspection and instructions.
Warranty (Limited)
Electro-Voice high fidelity speakers, systems, and accessories are guaranteed for five years from the original purchase date against defects in workmanship and materials. Malfunctioning units will be repaired or replaced at Electro-Voice's option without charge for materials or labor if delivered prepaid to an Electro-Voice service facility. Units will be returned prepaid. The warranty does not cover finish, appearance, or malfunctions due to abuse or operation outside specified conditions. Unauthorized repairs will void the guarantee.
For the correct shipping address, return instructions, and locations of authorized service agencies, contact: Service Department, Electro-Voice, Inc., 600 Cecil Street, Buchanan, Michigan 49107 (Phone 616/695-6831).
Electro-Voice also provides non-warranty service for E-V products.
Specifications are subject to change without notice.
Figure 5: Power Input vs Duty Factor
Note: The document refers to figures (Figure 1, 2, 3, 4, 5, 6) which are not included in the text provided, but are described in the context of the document.
