Primo EM258 and EM172 Microphone Capsules

Primo EM258 & EM172 DIY Mic Capsules: Unboxing First Look

Learn how to unbox two packages of DIY microphone capsules from MicBooster. If you’re into building your own microphones or just curious about what these tiny components look like, I’ll show you what arrived.

This is not a sponsored post. I purchased these items myself to check them out.

What Are Primo Capsules?

Primo makes small, high-quality electret condenser microphone capsules. They are popular in DIY audio projects for building everything from tiny lavalier mics to binaural recording setups. You can buy them directly from Primo, but I ordered these from MicBooster for convenience.

You can find the official datasheets here:

• Primo EU Site: http://www.primomic.de/omni.htm
• Primo US Site: https://primomic.com/products/

Package 1: EM258 Omni Capsules & Cables

The first package is perfect for building a simple stereo or binaural microphone.

Contents:

• Primo EM258 Capsules: 7 pieces (unmatched)
• Cable: Mogami 2368 unbalanced miniature cable
• Connectors: One Neutrik 3.5mm stereo right-angle plug and one straight plug

About the EM258 Capsule:

• Type: Omni-directional electret condenser
• Diameter: 5.8 mm
• Height: 2.0 mm (incredibly thin!)
• Sensitivity: -32 dB
• Operating Voltage (Vcc): 3V
• Signal-to-Noise Ratio: 74 dB (this is a “low noise” version)
• Datasheet: http://www.primomic.de/pdf/EM258.pdf

These capsules are tiny and flat, ideal for projects where you need a very low-profile microphone. They came in a small, plain plastic bag. While anti-static bags might be better, these seem fine and undamaged.

Package 2: EM172 Capsules & Balanced Cable

The second package is geared toward a more professional, balanced mono microphone build.

Contents:

• Primo EM172 Capsules: 4 pieces (single/unmatched)
• Cable: Mogami 2697 balanced miniature cable
• Additional Cable: A short piece of “figure of 8” screened cable

A Note on the EM172:
The EM172 model isn’t listed on the main Primo website anymore. It has been succeeded by the newer EM272 model. If you’re looking for the latest specs, check the EM272 datasheet here: http://www.primomic.de/pdf/EM272Z1.pdf

The EM172 capsules are slightly larger in diameter than the EM258s and have a more traditional cylindrical shape. They also arrived in a simple plastic bag.

First Impressions & Build Tips

Everything arrived exactly as ordered from MicBooster. The quality of the components—from the Primo capsules to the Mogami cable and Neutrik connectors—looks excellent.

If you’re planning a build, here are the basic steps you’d follow:

1. Plan Your Circuit: Decide if you’re building an unbalanced stereo mic (using the EM258 package) or a balanced mono mic (using the EM172 package). You will need a power source (like a battery or phantom power adapter) for the capsules.
2. Prepare the Cable: Cut your Mogami cable to the desired length and carefully strip the outer jacket and inner wires.
3. Solder the Capsule: Connect the tiny pins on the back of the capsule to the correct wires. This typically requires a fine-tip soldering iron and a steady hand.
4. Solder the Connector: Attach the other end of the cable to your plug (like the 3.5mm Neutrik).
5. House It: Design or find a case to protect the capsule and circuitry. This can be anything from a small metal tube to a 3D-printed enclosure.

These capsules are a great starting point for DIY audio enthusiasts. I’m looking forward to testing them in some projects soon. If you have experience building mics with these capsules, share your tips in the comments.