Headset Audio Guide
EPOS SD Pro 1 + Grandstream GRP 2650 — Audio Settings Setup
How to Configure Your Headset & Phone Audio
Follow these three steps to get the best call quality with the EPOS SD Pro 1 headset and Grandstream GRP 2650 phone.
EPOS / Sennheiser SD Pro 1
Wireless DECT Headset
Grandstream GRP 2650
14-Line Carrier-Grade IP PhoneThree Settings, Perfect Audio
Complete each step in order for best results.
Set the Microphone Volume Dial — Base Station
Flip the base station upside down. You will see a small rotary dial labelled Mic. Volume with positions 1–10. Turn it to position 7. This is the recommended starting point for the GRP 2650 — it gives callers a clear, natural voice level without distortion or clipping. Use a coin or flat-head screwdriver if the dial is stiff.
Set the In-Call Volume — GRP 2650 Phone
During an active call, use the Volume rocker (the – and + keys on the lower-right of the keypad) to set the headset listening volume to the midpoint — approximately level 5 out of 10 on the on-screen bar. This gives the headset's own volume control room to go both up and down without hitting the limits. Set this once and leave it; do not use the phone volume for day-to-day adjustments.
Fine-Tune Volume During Calls — Headset Audio Button
During every call, use the Audio button on the headset itself to raise or lower the listening volume. Push the button up to increase volume and down to decrease it. A double beep means you have reached the maximum or minimum. This is your primary day-to-day volume control — the phone volume (Step 2) stays fixed at the midpoint.
To mute your microphone: press the Audio button once during a call. The base station Link LED flashes red while muted. Press again to unmute.
Pro Tip — ABC Switch on the Base Station
If callers report that your voice sounds too quiet even at dial position 7, or if you hear distortion, try adjusting the ABC switch on the underside of the base station. Make a test call, then cycle through positions A, B, and C until the dial tone and your voice sound clearest in the headset. Position A is the default and works for most phones including the GRP 2650.
Quick Reference
All settings at a glance.
| Setting | Device | Location | Recommended Value | When to Adjust |
|---|---|---|---|---|
| Microphone Volume | EPOS Base Station | Rotary dial on underside of base | Position 7 | Set once during initial setup. Only change if callers consistently report you are too quiet or too loud. |
| In-Call Listening Volume | GRP 2650 Phone | Volume rocker (– / + keys) during a call | Midpoint (~5/10) | Set once. Leave fixed so the headset button has full range in both directions. |
| Fine Volume Control | EPOS Headset | Audio button on headset (push up / down) | Adjust per call | Use this for all day-to-day volume adjustments during calls. |
| Mute Microphone | EPOS Headset | Press Audio button once during call | Press to toggle on/off | Base station Link LED flashes red when muted. Press again to unmute. |
| ABC Switch | EPOS Base Station | Slide switch on underside of base | Position A (default) | Only change if audio quality is poor after adjusting the mic dial. |
Hearing safety: Always set the volume to a low level before putting on the headset. Prolonged exposure to high volume levels can cause permanent hearing damage. The EPOS SD Pro 1 will emit a double beep when the maximum volume is reached — treat this as a warning, not a target.