Galaxy S25 Ultra Cooling Test: Gaming and 4K60 Results With the KryoZon S9

Techduardo’s independent creator-run Galaxy S25 Ultra cooling test reported the processor at 57°C without external cooling and 41°C with the KryoZon S9 after 30 minutes of 4K60 recording, a 16°C difference under the same recording settings. The phone’s internal vapor chamber spreads heat effectively, but spreading heat and removing it from the chassis are separate jobs.

Image: Techduardo. Source: original YouTube review. Used with permission.

Techduardo tested the same Galaxy S25 Ultra across gaming and 4K60 workloads. The tables below preserve the original start and finish readings so the thermal behavior is easy to compare.

Gaming stress-test temperatures

Across three approximately 20-minute 3DMark runs, the uncooled phone finished at 42–43°C. S9 runs at maximum cooling finished at 14–23°C. The table includes both start and finish readings for full context.

Methodology: Techduardo ran approximately 20-minute 3DMark Wild Life, Wild Life Extreme and Solar Bay stress tests on a Galaxy S25 Ultra. The S9 was set to maximum cooling; Wild Life Extreme and Solar Bay were tested while charging.

In Techduardo’s approximately 20-minute Wild Life test, the Galaxy S25 Ultra moved from 33°C to 43°C without a cooler and from 13°C to 15°C with the external cooler at maximum output. Source: Techduardo on YouTube

What the gaming results mean

A colder phone matters only when heat is reducing sustained clocks. PhoneArena and CHIP both reported performance reductions during prolonged Galaxy S25 Ultra graphics testing.

The gaming data focuses on sustained thermal control. To measure the performance effect in a specific game, keep brightness, graphics settings, network and room conditions fixed, then compare the final 10 minutes of repeated runs.

The controlled 4K60 comparison

The 30-minute 4K60 runs used the same case-free phone, MC Pro 24 FPS settings, room, framing, lighting and brightness. That makes this the strongest comparison in the source.

Methodology: Techduardo recorded 4K60 video for 30 minutes on a case-free Galaxy S25 Ultra using MC Pro 24 FPS. Both runs used the same settings, room, framing, lighting, brightness and duration. Internal readings came from the on-screen monitoring overlay; surface values came from an external thermometer.

The processor and graphics readings were each 16°C lower with the S9. The warmest measured exterior point was 32.9°C with the cooler versus 42.4°C without it.

Quiet, fanless cooling and S9 specifications

The KryoZon S9 is an external fanless liquid-cooling phone accessory. A 60 × 60mm contact plate collects heat from the phone, and a PC-grade liquid loop carries it away from the handset.

With no cooling fan on the phone, the S9 avoids the high-pitched fan noise common to clip-on coolers. Its brushless pump is listed below 30dB, making the system a strong fit for streaming, voice chat and 4K60 recording near a microphone.

Specifications are taken from the official KryoZon S9 technical data.

For best contact, remove a thick case, clean the rear surface and centre the plate over the phone’s main heat zone. Use a 12V / 2.5A power source. High mode suits stress testing; AI or Low mode is better when maximum pre-cooling is unnecessary. See the KryoZon S9 product page for compatibility details.

Limits and best-fit use cases

For a repeatable comparison at home, start both runs at the same temperature and state of charge, use identical settings and compare the median of at least three passes.

Cold surfaces can fall below the room’s dew point. Watch for moisture, especially in humid environments, and stop if condensation appears. Charging also adds heat and changes system behavior.

Across the cited gaming and 4K60 workloads, the S9 consistently kept the reported finish temperatures below the corresponding uncooled runs.

Frequently Asked Questions

Does the Galaxy S25 Ultra need an external cooler for gaming?

External cooling is most useful when a demanding title loses frame-rate stability after 20–30 minutes, the screen dims, or the chassis becomes uncomfortable. Compare late-session FPS with identical settings to measure the effect in your game.

How much cooler did the Galaxy S25 Ultra run with the S9?

In Techduardo’s 30-minute 4K60 test, reported processor and graphics temperatures were each 16°C lower with the S9. The warmest external surface reading was 32.9°C with the cooler versus 42.4°C without it.

Can the KryoZon S9 cause condensation?

Condensation is possible whenever a cooled surface falls below the room’s dew point. Watch for moisture during initial use, avoid aggressive pre-cooling in humid conditions and use Low or AI mode when maximum cooling is unnecessary.

Can the S9 be used while the Galaxy S25 Ultra is charging?

The cited Wild Life Extreme and Solar Bay tests used the phone while charging. Charging adds heat and changes the workload, so use a compatible power setup, keep connectors dry and judge results separately from unplugged gaming.

Written by Wayne Wei

Co-founder of KryoZon. With a background in semiconductor cooling and consumer electronics, Wayne Wei tests every product in real-world scenarios — from marathon gaming sessions to 4K video renders — so you get cooling advice grounded in data, not marketing.