Monster Monster S21
Monster Shock Plus Bluetooth Speaker User Manual
Brand: Monster | Model: Monster S21
1. Introduction and Overview
The Monster Shock Plus Bluetooth Speaker is designed to deliver a powerful and immersive audio experience. Featuring 30W loud stereo sound and Monster's unique pure sound technology, it ensures crystal-clear highs and deep bass. With advanced Bluetooth 5.4, TWS pairing capability, and an impressive 15-hour playtime, this portable speaker is perfect for both indoor and outdoor use. Its IPX6 water-resistant rating provides durability against splashes and spills, making it an ideal companion for any adventure. The built-in microphone also supports hands-free calling for added convenience.

Figure 1: Front view of the Monster Shock Plus Bluetooth Speaker.
2. What's in the Box
- Speaker X1
- Lifting rope X1
- AUX IN Cable X1
- USB-C Charging Cable X1
- Quick Start Guide & Warning card X1

Figure 2: All items included in the product packaging.
3. Setup
3.1 Powering On/Off
To power on the speaker, press and hold the Power button (usually marked with a circle and a vertical line) located on the top panel until you hear an audible prompt or see an indicator light illuminate. To power off, press and hold the same Power button until the indicator light turns off and you hear a power-off sound.

Figure 3: Top panel with control buttons, including the Power button.
3.2 Bluetooth Pairing
- Ensure the speaker is powered on and in Bluetooth pairing mode. It will typically announce "Discovering" or have a blinking blue LED indicator.
- On your mobile device (smartphone, tablet, laptop), navigate to the Bluetooth settings.
- Search for available devices. The speaker should appear as "Monster Shock Plus S21" or similar.
- Select the speaker from the list to initiate pairing. Once connected, the speaker will announce "Connected" and the LED indicator will become solid blue.
The speaker utilizes Bluetooth 5.4 technology for a stable and fast connection, ensuring seamless audio streaming.

Figure 4: Advanced Bluetooth 5.4 technology for stable connections.
3.3 True Wireless Stereo (TWS) Pairing
For an enhanced audio experience, you can pair two Monster Shock Plus speakers together to achieve 60W synchronized stereo sound.
- Ensure both Monster Shock Plus speakers are powered on and not connected to any other Bluetooth device.
- On one speaker (this will be the primary speaker), press the TWS button (often marked with an 'M' or a chain link icon). The speaker will enter TWS pairing mode.
- The primary speaker will automatically search for and connect to the second speaker. Once connected, you will hear a confirmation sound, and the LED indicators on both speakers will change to indicate a successful TWS connection.
- Now, connect your mobile device to the primary speaker via Bluetooth as described in Section 3.2. Audio will play through both speakers in stereo.

Figure 5: TWS pairing for a wider stereo soundstage.
4. Operating Instructions
4.1 Control Buttons
The top panel of the Monster Shock Plus speaker features several control buttons for easy operation:
- Power Button: Press and hold to power on/off.
- Play/Pause Button: Press once to play or pause audio.
- Volume Up (+): Press to increase volume. Long press to skip to the next track.
- Volume Down (-): Press to decrease volume. Long press to go to the previous track.
- TWS/Mode Button (M): Press to switch between input modes (Bluetooth, AUX, TF Card, USB). Long press to initiate TWS pairing.

Figure 6: Overview of speaker control buttons.
4.2 Multiple Connectivity Options
Beyond Bluetooth, the Monster Shock Plus offers versatile connectivity for various audio sources:
- AUX Input: Connect external audio devices using the included 3.5mm AUX cable.
- TF Card Slot: Insert a TF (microSD) card loaded with your favorite music files.
- USB Port: Connect a USB flash drive for direct music playback.
- USB-C Charging Port: Used for charging the speaker.
To switch between these modes, press the Mode button (M) on the top panel.

Figure 7: Connectivity ports for various audio sources.
5. Maintenance
5.1 IPX6 Water Resistance
The Monster Shock Plus speaker boasts an IPX6 water-resistant rating, meaning it is protected against powerful water jets from any direction. This makes it suitable for outdoor use, poolside, or beach outings. However, it is not designed for submersion in water. Ensure the port cover on the side is securely closed to maintain water resistance.
To clean the speaker, use a soft, damp cloth. Avoid using harsh chemicals or abrasive cleaners.

Figure 8: IPX6 water resistance for outdoor durability.
6. Troubleshooting
If you encounter issues with your Monster Shock Plus speaker, please refer to the following common solutions:
- No Power:
- Ensure the speaker is fully charged. Connect it to a power source using the USB-C cable.
- Press and hold the Power button for a few seconds to ensure it's not just a short press.
- Cannot Pair via Bluetooth:
- Make sure the speaker is in pairing mode (blinking blue LED).
- Ensure Bluetooth is enabled on your device and it's within range (up to 33 feet).
- Forget or remove "Monster Shock Plus S21" from your device's Bluetooth list and try pairing again.
- Restart both the speaker and your Bluetooth device.
- No Sound or Distorted Sound:
- Adjust the volume on both the speaker and your connected device.
- Ensure the speaker is not muted.
- If using AUX, TF card, or USB, ensure the correct mode is selected and the audio source is functioning correctly.
- Try playing a different audio file or from a different application.
- TWS Pairing Issues:
- Ensure both speakers are Monster Shock Plus models and are not connected to any other Bluetooth devices.
- Place the speakers close to each other during TWS pairing.
- Repeat the TWS pairing steps carefully.
7. Specifications
| Feature | Detail |
|---|---|
| Brand | Monster |
| Model Name | Monster Shock Plus S21 |
| Speaker Type | Portable Speaker |
| Connectivity Technology | Bluetooth, Auxiliary, USB |
| Wireless Communication Technology | Bluetooth 5.4 |
| Speaker Maximum Output Power | 30 Watts |
| Audio Output Mode | Stereo |
| Battery Life | 15 Hours |
| Charging Time | 2 Hours |
| Water Resistance Level | IPX6 Water Resistant |
| Product Dimensions | 2.99"D x 10.08"W x 4.02"H |
| Item Weight | 1.83 pounds |
| Material | Plastic |
| Control Method | Button |
| Included Components | Speaker, Lifting rope, AUX IN Cable, USB-C Charging Cable, Quick Start Guide & Warning card |
8. Warranty and Support
8.1 Warranty Information
The Monster Shock Plus Bluetooth Speaker comes with a Limited Warranty. Please refer to the included Quick Start Guide & Warning card for specific terms, conditions, and duration of the warranty. Retain your proof of purchase for warranty claims.
8.2 Customer Support
For technical assistance, troubleshooting beyond this manual, or warranty inquiries, please contact Monster customer support. Contact information can typically be found on the product packaging, the official Monster website, or the Quick Start Guide.
For the most up-to-date support information, please visit the official Monster website or the retailer's support page where you purchased the product.
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