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Subwoofer amplifier

Item # 452SMP300

This powerful amplifier delivers up to 250 watts of Class D power for driving one or two subwoofers.

This powerful amplifier delivers up to 250 watts of Class D power for driving one or two subwoofers.

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Since 1974

Years of experience making people happy.

About the OSD SMP300

Eric A.

A powerful subwoofer amplifier

The OSD SMP300 delivers up to 250 watts of efficient Class D power for driving one or two subwoofers. It's 4-ohm stable and offers a variety of input/output connections that open up options for multiple subwoofer configurations. It also offers convenient remote turn-on options: always on, music-sensing, and 12-volt trigger. And you can dial in your subwoofer's performance with a variable phase control, adjustable level control, and 35-180Hz low-pass crossover control.

Product highlights:

  • Class D mono subwoofer amplifier
  • delivers up to 250 watts per channel into 4 ohms (150 watts into 8 ohms)
  • frequency response: 20-160Hz (±1dB)
  • signal to noise ratio: 95dB
  • variable low-pass crossover control: 35-180Hz
  • variable phase control: 0° to 180°
  • rotary level control on back panel
  • remote turn-on options: always on, music-sensing, and 12-volt trigger
  • two pairs of binding posts for speaker-level input and output
  • single pair of binding posts for speaker-level subwoofer output
  • stereo RCA line input and output
  • mono RCA LFE input
  • two-pin Euroblock 12-volt trigger input and output
Dimensions and warranty:

What's in the box:

  • Subwoofer amplifier
  • 6' AC power cord
  • 2 Brackets
  • 2 Screws
  • Install Guide

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Crutchfield response

<< >>

More details on the OSD SMP300

Stacey B.

Features & specs

Number of Channels 1
Power Output per Channel (8 ohms) 150
Power Output per Channel (6 ohms) ---
Power Output per Channel (4 ohms) 250
Frequency Bandwidth 20-160
THD 1%
Minimum Impedance 4
Bridged Power per Channel 0 watts
Speaker Outputs 1
THX Certification No
Width (inches) 16-9/16
Height (inches) 2-7/8
Depth (inches) 10-15/16
Weight 7 pounds
Parts Warranty 2 Years
Labor Warranty 2 Years
Inputs & Outputs
Number of Inputs 3
Input Type LFE, RCA, Speaker
Removable Power Cord IEC 3-prong
Level Controls No
Speaker Connectors Binding Post

Product Research


Mono Subwoofer Amplifier: Designed for use with passive subwoofers such as in-wall subs (such as OSD Audio's SC800D, sold separately) that require external power, the SMP-300 provides continuous, stable power. A powered subwoofer has its own internal amplifier, while a passive subwoofer requires external power and most in-wall subs are passive. After all, it's not so easy to install a 50-pound powered subwoofer inside a wall. That's where an amp like the SMP-300 comes into play. This amp not only adds necessary power, but routes LFE away from your surround speakers, which in turn gives you much cleaner highs and midrange. This subwoofer amp does much more than supply power, it also improves the overall sound quality of your entire surround sound system. This compact subwoofer amplifier will enhance the low frequency sound effects on your movie and music soundtracks, so you'll experience highly accurate bass and a more intense surround sound.

  • Class D Technology: The SMP-300 uses Class D digital amplifier technology that combines the best qualities of both Class A and B amp protocols into a highly efficient compact chassis that is ideal for a feature-rich digital sub amp that does not run hot or take up a lot of space.
  • Low Impedance Stable: OSD Audio's SMP-300 Class D mono subwoofer amplifier delivers dynamic and clean power even under demanding, low-impedance loads. It delivers 150 watts (RMS) / 300 watts (Peak) when used with an 8-ohm passive subwoofer or 250 watts (RMS) / 500 watts (Peak) when used with a 4-ohm passive subwoofer.

Subwoofer Controls: The SMP-300 includes a variable low pass filter control for balanced and seamless sound quality, as well as variable phase control for additional fine tuning, plus independent volume control to match the output of your audio system. These controls can be easily accessed on the front-panel of the mono subwoofer amplifier. There is also a rear-panel volume limit control.

  • Volume Level: Use the volume knob to match output level of the SMP-300 and your passive in-wall subwoofer with the rest of your speaker system.
  • Low Pass Filter: The variable low pass filter (35-180Hz) allows you to adjust the upper frequency limit of the subwoofer to control the overlap of the subwoofer's upper frequencies and the main speakers' lower frequencies. This results in bass that complements the sound from the main speakers rather than overpowers.
  • Phase Control: The variable phase control knob that operates over a range from 0 degrees to 180 degrees and allows you to match the arrival times of the sound waves from the subwoofer and the main speakers. This fine-tuning results in bass that is less muddy or thumpy, but rather smooth and detailed.
  • Volume Limit: Use this control to adjust the maximum volume setting of the SMP-300 amplifier and your connected passive subwoofer. Setting the max volume setting will ensure that no clipping or damage will occur even when the front-panel volume control is turned all the way up.

Line-Level & Speaker-Level Connectivity: Multiple connection options include a mono LFE input, stereo RCA line-level inputs/outputs, and speaker-level inputs/outputs to cover newer and older source equipment.

  • Mono LFE Input: If your AV preamplifier or receiver has a LFE or Sub out, you can connect it to the SMP-300's LFE input. The LFE input will bypass the SMP-300's low pass filter and instead use the LFE bass management of your AV preamplifier or receiver. The mono LFE input consists of a female mono RCA jack.
  • Stereo RCA Inputs/Outputs: If your preamplifier or receiver does not contain a LFE or Sub out, then you can use the line-level outputs from your preamp or receiver to connect to the stereo RCA inputs of the SMP-300 amplifier. There is also a stereo RCA output that can be used to pass the line-level input signal of the SMP-300 amplifier to another receiver or amplifier. The line-level inputs and outputs consist of female stereo RCA jacks.
  • Speaker Inputs/Outputs: The SMP-300's speaker level inputs can be used if your receiver does not have a LFE, Sub, or line-level output. In this setup, you'll connect the main speaker outputs of your receiver to the speaker level inputs of the SMP-300 amplifier, and then connect your main speakers to the speaker level outputs of the SMP-300 amp. The speaker-level inputs and outputs consist of binding post terminals that will accept bare wire (up to 14AWG), pin-connectors, and banana plugs (single only).

Subwoofer Output Terminals: The SMP-300 mono subwoofer amplifier is outfitted with two binding-post terminals to connect your speaker wire and passive subwoofer. The binding post terminals will accommodate bare wire (up to 12AWG), pin-connectors, and banana plugs (single or dual).

Auto On/Off: The OSD Audio SMP-300 can be set to automatically turn-on when it sense an audio signal on the mono LFE or stereo RCA line-level inputs. It will automatically turn off after 15 minutes of no signal and no operation. The SMP-300 also features a 12V trigger input and output for auto on/off synchronization with other components. The 12V trigger input and output each consist of a 2-wire terminal euro-block.

Power Requirements: The OSD Audio SMP-300 comes with a detachable 6' IEC 3-prong AC power cord that will need to be plugged into the back of the mono subwoofer amplifier and an AC wall outlet or surge protector (sold separately - see Accessories Tab).

Mounting Options: The OSD Audio SMP-300 mono subwoofer amplifier can be mounted on a shelf or other flat tabletop surface. It can also be mounted in a equipment rack or cabinet using the supplied hardware. It takes up 1U rack space with the feet removed.

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Customer Q&A

1 question already asked

Can this be Paired with The SONOS AMP?
[ Scott  Feb 02, 2023 ]
1 answer
Yes. The Sonos Amp's sub output could be connected to the LFE input of the SMP300.
[ ZACHARY  Feb 02, 2023 ]  Staff

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