Monster Shock Plus S21 Portable Bluetooth Speaker, 40W

The Monster Shock Plus S21 is a portable Bluetooth speaker listed with 40W output, stereo audio, and claimed playback of up to 20 hours. AUX and TF card playback, wireless pairing with a second speaker, and a claimed IPX6 rating suit flexible indoor and outdoor listening, though listing details need clarification before relying on some specifications.

At a glance

The product title and feature copy claim 40W stereo sound and up to 20 hours of playtime. Battery life is a listing claim, not a guaranteed runtime.
The listing describes Bluetooth 6.0, AUX, TF card and USB connections, but the technical connectivity field lists Bluetooth, Auxiliary and USB only.
TWS pairing is claimed to connect two speakers for stereo playback. A second speaker is not listed as included.
A feature description claims IPX6 water resistance. The technical field gives only “Water Resistant,” so confirm the rating and intended exposure if it matters.
Built-in microphone and hands-free calling are claimed in the feature copy.

Price

$39.99Save 79%

Reference price: ~~$189.99~~

Price checked: Nov 12, 2026

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Pros and cons

Pros

Multiple playback options are claimed, including Bluetooth, AUX and TF card input.
TWS pairing offers a claimed option to link a second compatible speaker.
The claimed 20-hour playtime and lifting rope may suit travel or outdoor listening when portability matters.

Cons

The listed Bluetooth range is about 33 feet, which may constrain placement away from the connected device.
The product's plastic enclosure and tabletop mounting description give no listed ruggedized construction beyond the water-resistance claim.

Technical specifications

23 specifications

Identity
Brand	Monster
Model	Shock Plus

Audio
Maximum output power listed	40 watts
Audio output mode	Stereo
Frequency response	20000 hertz
Audio channels	2
Audio driver type	Dynamic Driver
Audio driver size	40 millimeters
Signal-to-noise ratio	80 db
Impedance	140 ohm

Connectivity and controls
Connections listed	Bluetooth, Auxiliary, USB
Control method	Push Button
Maximum range listed	33 feet
Audio latency listed	16 milliseconds

Power and battery
Power configuration	Battery Powered
Battery listing	1 12V batteries required. (included)

Dimensions and installation
Mounting type	Tabletop Mount
Dimensions	2.99"D x 10.08"W x 4.02"H
Weight	0.7 kg

Materials and protection
Enclosure material	Plastic
Water resistance	Water Resistant
Color	Black S21

Other listed details
Warranty description	1 Year Manufacturer

What to know before buying

The claimed up-to-20-hour runtime has no listening-volume or other operating conditions specified.

Listing details to confirm

The listing has inconsistent or unconfirmed details: Bluetooth 6.0, TF support and IPX6 appear in title or feature text, while the technical fields list Bluetooth, Auxiliary and USB connections and only “Water Resistant.” It also lists 40W output and stereo claims alongside technical entries such as a 140 ohm impedance and 80 db signal-to-noise ratio, while driver diameter fields include a 6-inch subwoofer, 10-inch woofer and 1-inch tweeter for a speaker listed at 10.08 inches wide. Confirm the selected listing's exact configuration and rating before buying, especially if size, input support or water exposure is important.

Who is it for?

A good fit for

Buyers seeking a portable speaker with claimed stereo output and several wired or wireless playback options.
People who want the option to pair two speakers for a wider stereo setup.
Travelers or outdoor listeners who value a claimed long playback time and water resistance, subject to confirming the rating.

Less suited to

Buyers needing verified waterproofing for submersion or a clearly specified exposure rating.
Anyone requiring confirmed TF-card playback or precise driver and enclosure dimensions without checking the seller's selected configuration.

Monster Shock Plus S21 Portable Bluetooth Speaker, 40W · photo 2 — Additional product photo 2

Customer reviews on Amazon

4.8 / 5 · 21 ratings

5 stars86%86%
4 stars14%14%
3 stars0%0%
2 stars0%0%
1 star0%0%

Aggregate ratings are favorable, with the available distribution concentrated in four- and five-star ratings. This is a small rating sample and provides no detail about sound quality, battery runtime, connectivity, or water resistance, so it cannot resolve the listing's specification uncertainties.

Frequently asked questions

How long does the Monster Shock Plus claim to play?

The feature copy claims up to 20 hours on a charge, but does not specify the conditions for that runtime.

Can it pair with another speaker?

The listing claims True Wireless Stereo pairing for two speakers. It does not establish that a second speaker is included.

Is this speaker rated IPX6?

The title and feature copy claim IPX6, but the technical water-resistance field only says “Water Resistant.” Confirm the rating on the selected listing before relying on it.

Does it support TF cards?

TF playback is claimed in the title and feature copy, but the technical connectivity field lists Bluetooth, Auxiliary and USB. Check that TF support applies to the exact listing.