OEM Systems Model 500 Subwoofer Amplifier — Owner's Manual

Owner's manual for the OEM Systems Model 500 subwoofer amplifier — a 500W Class A/B amplifier utilizing patented BASH technology for high electrical efficiency, with four independent controls for integrating nearly any subwoofer with your main speakers and listening environment.

Important Safety Instructions

• Do not use this apparatus near water.
• Clean only with a dry cloth.
• Do not block any ventilation openings; install per manufacturer's instructions.
• Do not install near heat sources (radiators, heat registers, stoves, other heat-producing apparatus).
• Do not defeat the safety purpose of the polarized or grounding-type plug.
• Protect the power cord from being walked on or pinched, particularly at plugs and receptacles.
• Only use attachments/accessories specified by the manufacturer.
• Unplug during lightning storms or when unused for long periods.
• Refer all servicing to qualified personnel — required if the power cord/plug is damaged, liquid has been spilled, objects have fallen into the unit, the unit has been exposed to rain, doesn't operate normally, or has been dropped.
• Warning: Disconnect power before making any connection to the speaker terminals — risk of electrical shock.

Box Contents

Amplifier, Rack Ears with Screws, Power Cord, Owner's Manual.

Features

• 500W Class A/B amplifier using patented BASH technology for high electrical efficiency
• 4 independent controls integrate the subwoofer with main speakers and the room
• Continuously-variable low-pass filter, adjustable 40Hz–120Hz, bypassable for external filters
• Continuously-variable phase circuit, adjustable 0–180 degrees
• Continuously-variable subsonic filter, adjustable 20Hz–35Hz, protects the subwoofer from overdrive/excessive excursion
• Defeatable Auto-Power mode — turns amplifier on automatically when signal is detected
• Dual subwoofer outputs allow multiple woofers without pigtails or wire nuts
• Stereo Line Level inputs/outputs let the amp sit between a preamp and amp without Y-connectors; buffered internal summing network derives mono from L/R while preserving stereo signal for main speakers
• Double-insulated isolated-ground electrical supply prevents ground loops and reduces noise floor

Controls & Connections (Rear Panel)

Connection

Output: Two output sets are wired internally in parallel (this is a mono amplifier — same signal at both). Calculate load impedance for parallel connections accordingly (e.g. two 8-ohm loads on Output 1 and Output 2 = 4-ohm total load). The Model 500 is optimized for a 4-ohm load. Speaker connectors are 5-way binding posts accepting banana plugs (remove the button-plugs to access). No signal cable is included — use a shielded RCA-type coaxial cable or shielded two-conductor wire with RCA connectors.

Input Option 1 (Left/Right Stereo): Use when no LFE/Subwoofer output is available but a line-level Front Channel Output or Preamp Output is. Connect the left/right RCA front channel outputs of your receiver/preamp to the Left/Right Line Level inputs.

Input Option 2 (LFE): Preferred when your receiver/processor has a dedicated LFE or Subwoofer output. Use a single RCA cable from the LFE/Subwoofer output to the Left/LFE Line Level input.

AC Power: Insert the supplied IEC AC cable into the amplifier's IEC receptacle. Connect power only after all other connections are made.

Setup & Room Placement Tips

• Placing a subwoofer near a wall increases radiating power up to 2X; near a corner (intersection of two walls), up to 4X ("corner loading").
• Sitting at a room boundary (e.g. near the back wall) significantly increases perceived bass level.
• Placing a subwoofer close to the listening position (<5ft/1.5m) can increase transient intensity and reduce acoustic power demand — or increase demand if placed at a primary resonant node.
• Bass frequencies below ~80Hz are largely omnidirectional/non-localized, so subwoofer placement isn't limited to the front of the room — though tactile/vibration cues can suggest source direction.
• Multiple subwoofers can be placed symmetrically or asymmetrically to reduce room-mode effects and balance localization.
• It is not necessary to aim the front of a subwoofer at the listening position.

Fine-Tuning the Controls

Level & Frequency: Start with Level all the way down and Frequency set to 120Hz. Play bass-heavy music and increase Level until bass sounds robust/exaggerated, then reduce Frequency to blend with main speakers (most 6"–8" woofer speakers blend well between 50–80Hz). Readjust both until bass sounds full, extended, and natural using multiple test tracks.

Phase: Less noticeable than Level/Frequency. If difficulty hearing changes, temporarily set Frequency to 120Hz while adjusting Phase, then return Frequency to its desired setting. Rotate Phase back and forth listening for changes in bass localization/level; settle on the position with the most defined, coherent bass.

Subsonic Filter: Protects the subwoofer from excessive excursion and preserves amplifier power for reproducible bass frequencies. Set at or just below the woofer's low-frequency limit. Factory default is 35Hz (works well for most 12" or smaller subwoofers); lower it for larger/more capable woofers.

Other Controls

Crossover Switch: To bypass the internal crossover and use an external one (e.g. in a receiver/processor), move the Crossover switch to Bypass — the subwoofer will then pass signals up to 300Hz. Level and Phase adjustments remain active even when the crossover is bypassed.

Auto Power Mode Switch: The amplifier automatically powers up when signal is detected and enters standby after ~10 minutes of silence. Bypass this by switching Auto to ON if using a remotely operated AC power source instead.

Specifications