Yamaha NS-615B
Owner's Manual
18cm 2-Way 2-Speakers System
Special Features
The NS-615B speakers are designed in accordance with Yamaha Audio's policy of accurately and naturally reproducing music. They feature superior directivity, very low distortion (less than 1% over 100 Hz at 96 dB/1 m), a woofer with a large diameter voice coil, a tweeter with unique tangential edge support, and an enclosure built with Yamaha's woodworking expertise. This results in a compact, high-performance unit with high power handling capacity.
Enjoy the natural sound of all types of music with the stylishly compact NS-615B.
Precautions
The NS-615B grille is removable. To remove it, grasp the bottom edges gently and pull away from the cabinet, then remove the upper part. Be careful not to damage attachment parts during removal.
Ensure your amplifier's output terminals are compatible with the connection procedures outlined in the amplifier's owner's manual.
While higher amplifier output power can provide better low-distortion music response, ensure your amplifier's output does not exceed the NS-615B's maximum input capacity. Typically, setting an amplifier's volume control to its midpoint produces about 70% of its maximum output capacity.
Connecting to Your Amplifier
Connect the speaker output terminals on your amplifier to the terminals on the rear of the NS-615B using appropriate connector cords. Ensure the amplifier power is switched off before connecting.
The NS-615B uses push-spring type connection terminals. Connect the left speaker to the amplifier's left-channel output and the right speaker to the right-channel output. Observe correct polarity: the cord side with the silver line is typically plus (+), and the other side is minus (-).
Speaker polarity differences can affect stereo response and tonal clarity. If using a tube-type amplifier, ensure you connect only to the 8-ohm terminals.
To connect: Push the lever on the terminal, insert the stripped end of the wire into the hole, and release the lever to secure the wire. Connect the red terminal to the amplifier's plus (+) terminal and the black terminal to the amplifier's minus (-) terminal.
[Connection diagram: Red terminal to Plus Terminal, Black terminal to Minus Terminal]
Speaker Location
Optimal speaker placement significantly impacts performance. Consider the following:
- Place speakers so tweeters are at ear level for a natural concert hall feel. Avoid placing them directly on the floor or carpet, as this can impair bass response. Use heavy, solid stands.
- Separate left and right speakers by 1.5 to 2 meters for optimal stereo effect. Placing them too close reduces the stereo effect; too far apart can cause a "middle omission" effect.
- The wall behind the speakers should have a live, reflecting surface (e.g., polished). The wall behind the listener should be sound-absorbing. Thick curtains can help absorb sound if the listener's wall is concrete or has glass.
- Experiment with different locations to achieve the best balance of bass, midrange, and treble response for your room.
Be careful where you place your turntable. If it is on the same support as the speakers or directly in front of them, howling can occur.
Avoid locations exposed to direct sunlight or high temperatures.
Precautions During Use
The NS-615B has a rated input of 25W and a maximum input capacity of 50W. Observe the following:
- Rated Input: This is the maximum average input for long listening sessions with optimum, fatigue-free music response.
- Maximum Input Capacity: This value can be reached for short periods during peak program source levels, which can be up to ten times the average level. Peaks should not exceed twice the rated input. Use level meters to regulate dynamic passages and avoid exceeding this maximum.
- Operation Precautions: Be especially careful not to exceed the RATED input in the following situations:
- When tone controls on your preamp or pre-main amplifier are set to maximum (bass or treble).
- When a special signal is fed through the speakers, such as from fast winding/rewinding tape, turntable needle shock noise, power-on transients, or sine waves from a signal generator.
Characteristics
The following graphs illustrate the performance characteristics of the NS-615B:
Frequency Response and Harmonic Distortion
A graph shows frequency response from 20 Hz to 40 kHz, with harmonic distortion curves (2nd and 3rd) overlaid, measured at 1 meter with a 6V input.
Impedance Characteristic
A graph shows impedance from 20 Hz to 40 kHz.
Directional Characteristics (Horizontal Plane)
A polar plot illustrates the horizontal directional characteristics of the speaker.
Specifications
| Parameter | Value |
|---|---|
| Type | 2-way acoustic suspension |
| Woofer | JA-1801 180mm cone |
| Tweeter | JA-0518 38mm soft dome type |
| Crossover frequency | 2 kHz (12 dB/Oct) |
| Fundamental resonance frequency | 85 Hz |
| Impedance | 8Ω |
| Output sound pressure level | 96 dB at 1m 4 Watt Input |
| Rated input capacity | 25W |
| Maximum input capacity | 50W |
| Frequency response | 60 Hz – 20,000 Hz (+4~-8dB) |
| Dimensions (HxWxD) | 382 x 215 x 199 mm (15" x 8-1/2" x 7-13/16") |
| Weight | 6.0 kg (13 lbs 4 oz) |
Specifications subject to change without notice.
