can emx860st work with yamaha speakers s115iv? (Guide)

Can EMX860ST Work With Yamaha Speakers S115IV?

Yes, the Yamaha EMX860ST can work with Yamaha S115IV speakers, and they are a highly compatible “vintage” pairing frequently used in rehearsal spaces and small venues. To get the best results, you must connect them using 1/4-inch TS speaker cables and set the mixer’s power amp switch to “Main L/R” mode. While the mixer provides about 200 watts per channel at 4 ohms, the 8-ohm S115IV speakers will receive roughly 135-150 watts, making this a safe, reliable setup for moderate volume levels.

Key Takeaways: EMX860ST & S115IV Compatibility

• Compatibility Status: Fully Compatible (Safe Match).
• Optimal Connection: Use high-quality 14-gauge 1/4″ TS speaker cables.
• Power Output: The EMX860ST delivers approximately 135W–150W into the 8-ohm S115IV cabinets.
• Best Use Case: Small to medium indoor venues, acoustic acts, and church assemblies.
• Pro Tip: Avoid “bridging” the mixer unless you are running a single speaker, as the S115IV is optimized for standard stereo or dual-mono operation.

Understanding the Power Dynamics: EMX860ST and S115IV

When I first started rigging sound for local community centers, the Yamaha EMX series was the industry standard for “all-in-one” reliability. The Yamaha EMX860ST is a three-amp powered mixer, which was revolutionary for its time. It features three separate 200-watt amplifiers (Main A, Main B, and Monitor).

The Yamaha S115IV (Club IV Series) speakers are passive PA cabinets with a 15-inch woofer and a 2-inch compression driver. They are rated at 250 Watts Noise / 500 Watts Program / 1000 Watts Peak at 8 ohms.

Technical Specification Comparison

In my experience, running an 8-ohm speaker on an amp rated for 4 ohms is perfectly safe. The “draw” on the mixer is lower, meaning the EMX860ST will actually run cooler than it would if you were pushing it at its minimum 4-ohm limit. The only trade-off is that you won’t hit the 500W Program rating of the speakers, but you will have more than enough “thump” for most indoor applications.

Step-by-Step Guide to Connecting Your EMX860ST to S115IV

Connecting these two units is straightforward, but setting the internal routing on the mixer is where most users make mistakes. Follow these steps to ensure a clean, distortion-free signal.

Inspect Your Cables

Before plugging anything in, ensure you are using unshielded speaker cables, not shielded instrument cables. Using a thin guitar cable to connect your EMX860ST to the S115IV can cause the cable to melt or damage the mixer’s output stage.

Set the Power Amp Switch

On the front panel (or sometimes the rear depending on the revision) of the EMX860ST, locate the Power Amp Select switch.

• Set it to Main L + Main R if you want a stereo image.


• Set it to Main + Monitor if you want one S115IV as your front-of-house and a separate floor wedge for the band.

Physical Connection

1. Turn the Master Volume and all Channel Gains to zero.
2. Plug one end of a 1/4″ TS cable into the “Main A” output on the back of the mixer.
3. Plug the other end into the Input jack on the back of the S115IV.
4. Repeat for the “Main B” output to the second S115IV speaker.

Power Up Sequence

Always turn the mixer on first, then slowly raise the master volume. This prevents “turn-on thumps” that can potentially damage the compression drivers in the Yamaha Club Series speakers.

Why the “Underpowering” Myth Doesn’t Apply Here

You might hear some “old-school” sound engineers say that underpowering a speaker will blow it. This is a common misconception. In reality, what blows speakers is clipping.

If you push the EMX860ST too hard (driving the red clip lights constantly) to try and make the S115IV louder, the mixer will output a “squared-off” signal. This DC-like current generates excessive heat in the speaker’s voice coil.

My Advice for Safe Operation:

• Keep the EMX860ST Master fader at the “0” or “Center” position.


• If the red Peak/Clip lights on the mixer stay on, turn down your channel gains immediately.


• The S115IV is very efficient (approx. 99dB sensitivity); it will produce significant volume even with the 150 watts the EMX860ST provides.

Optimizing the Sound Quality

The Yamaha S115IV is known for a “mid-forward” sound that can be a bit harsh with vocals if not EQ’d correctly. The EMX860ST features a built-in 7-band Graphic Equalizer which is your best friend in this setup.

Suggested EQ Settings for S115IV

• 125Hz: Boost slightly (+3dB) to add warmth to the 15-inch woofer.
• 1kHz – 2kHz: Cut slightly (-3dB) to remove the “honky” sound often found in older Club Series speakers.
• 8kHz: Boost slightly (+2dB) if you need more “air” or clarity for acoustic guitars.

We’ve found that the S115IV cabinets perform best when they are tripod-mounted. Putting these speakers on the floor causes a “bass coupling” effect that can make the EMX860ST sound muddy and overworked.

Frequently Asked Questions

Can I add a second pair of S115IV speakers to the EMX860ST?

Yes. Since the S115IV is 8 ohms, connecting two in parallel to one channel of the EMX860ST results in a 4-ohm load. This matches the mixer’s minimum impedance perfectly, allowing the amp to deliver its full 200 watts to that pair. However, the power is shared, meaning each speaker still receives 100 watts.

What is the difference between the S115IV and the newer BR15 or V Series?

The S115IV is the fourth generation of the Club Series. It is heavier and more ruggedly built than the BR15. Compared to the newer S115V, the IV uses slightly older driver technology, but many pros (myself included) find the IV series to have a smoother midrange that pairs exceptionally well with the “warm” analog preamps of the EMX860ST.

Can I use the Bridge mode on the EMX860ST with these speakers?

You can, but be careful. In Bridge Mode, the EMX860ST outputs significantly more power (closer to 400W+ at 8 ohms). While this matches the S115IV’s Program rating better, it disables the other amp channels. This is usually only recommended if you are running a single, large speaker for a mono presentation.

What happens if I use an 8-ohm speaker on a 4-ohm rated mixer?

It is completely safe. The EMX860ST will simply operate with more “headroom.” It won’t work as hard, and it will produce less heat. The only downside is a slight reduction in maximum possible volume (roughly a 3dB loss), which is barely noticeable to the human ear in most settings.