Koss ESP-9

 Koss ESP-9 Electrostatic Studio Monitor

Offers a new tool for improved audiometry with self-bias or ac line energizing. Controlled monitoring with 1 octaves ±2 dB range exceeding best loudspeaker systems.  Eliminates all room reflections and polar distribution problems.

 Super wide-range response -  for critical, controlled monitoring of finest recording sources. Delivers all 10 audible octaves, 10 - 19,000 Hz (±5 dB), 4 octaves beyond ordinary headphones.

Virtually distortion-free performance -  precision electrical balancing of push-pull acoustical circuitry to give fatigue-free listening through long, intense recording sessions. Elements cancel all 2nd harmonic distortion, unlike conventional units.

Lightweight - human engineered for comfort - uses fluid-filled cushions for good, comfortable seal; extendable stainless steel headband with wide cushion for perfect fit and restful listening.

Calibrated, precisely controlled output - ideal for audiometric uses - switch on front panel of energizer selects ac operation for precision measurements of output; in self-energized switch position no connection to ac lines is required; this gives maximum convenience.

 High-power capability in very low bass range - lerge, oversize coupling transformers mounted in external E-9 energizer unit give good wave form at 30 Hz with up to 10 volts input.

No special amplifiers required - low efficiency, connects to low-impedance speaker terminals - easy, quic hook-up to any rated high-quality amplifier delivers performance to specification. Excellent for evaluating the spectral character of very low level noise in equipment like tape mastering machines and recording consoles. In contrast to the ESP-6 and ESP-7, both cups are independently energized; al. Eft cup signal in not required to supply bias to the right cup.

 E-9 Energizer:  Contains 2 coupling transformers, self-energizing circuitry, speaker/headphone transfer key-switch and ac pilot light on black anodized front panel Also contains ac power transformers, ac on-off switch, ac line fuse, and speaker terminals.  Has 6'4" conductor input cable terminated with 4 spade lugs to connect to amp. output terminals.

Size:  4 ½ H x 3 ¾ W x 6 ¼ D inches

Weight:  3 pounds

Specifications

Electrical

Frequency Response Range, Typical:  15 -15,000 Hz ±2 dB (10 octaves) 10 - 19,000 Hz ±5 dB

Sensitivity:  80 dB SPL at 1 kHz ±1 dB reffered to 0,0002 dynes/cm² with 1 volt at the input

Total Harmonic Distortion:  less than 2% at 110 dB SPL

Isolation from External Noise:  40 dB average through fluid-filled cushions

Power Handling Capability:  Max. Continous program material should not exceed 10 volts (12 watts) as read by an ac VTVM (Ballantine meter 310B or equal) with average indicating circuitry and rms calibrated scale, provides for transient peaks 14 dB beyond the continuous level of 10 volts

Source impedance: Designed to work from 4 to 16 Ω amplifier outputs

External Power Requirements:  None, except when external ac line is selected on front panel switch of the E-9 Energizer (1/16 amp. 117 VAC, 50/60 Hz normally; 234 VAC with internal strap for foreign use)

Physical

Size of Cup:  4 ¼" H x 3 ¾" W x 1 ¼" D

Cushions:  Fluid-filled for high ambient noise isolation

Headband:  Extendable stainless steel bands with self-adjusting pivoting yokes; conforms to any head size

Boom Mount for Microphone:  Knurled, anodized aluminum knob on left cup with threaded shaft and 2 compressible rubber washers; accepts all standard booms

Headset Cable:  Flexible, polyvininyl, 5 conductor shielded. 6" long, black with 5 prong plug keyrd to E-9 Energizer receptacle

Weight of Headset Only:  19 ounces

Accessory provided:  6" ac line-cord P.N 41-0235 for optional use