U87 EQ Mod Kit

The Studio Projects C1 and C3 sound
nothing like the Neumann U87!

(until we fix 'em)

That's what a purist would tell you, probably while pounding on the table just to make sure you get the point.

That's OK. He spent $3000 for his fancy microphone. He has paid well for the right to be skeptical about the sound of your cheap gear.

And anyway, he's right, for the most part. The C1 and C3 use a capsule that is remarkably similar to the U87's, but the C1/C3 don't contain the EQ circuit that the U87 does. That's why the C1 and C3 sound peaky-bright in the high octaves, while the U87 is famously neutral (more or less).

Too bad the C1/C3 circuit can't be fixed...

Because then that U87-ish capsule would let the C1/C3 sound pretty much like the U87, eh?

If only someone would invent a circuit to implement the U87's high-frequency filter for the Studio Projects microphones...

You know, something like this:

C1 EQ Board prototype

What is that thing?

Pictured above is our proprietary circuit board add-on for the Studio Projects C1 and C3. It replaces and upgrades the main signal capacitors, and implements a variable high-frequency rolloff so you can tune the mic's brightness to suit your personal taste.

In a sense, the recipe for a U87 is a K67 capsule plus an aggressively bandpassed circuit. The C1 and C3 already have the right capsule. As it turns out, creating a high-frequency rolloff, or "deemphasis," or "corrective EQ" circuit is pretty easy. And pretty inexpensive.

Our mod kits don't stop there. Several additional upgrades are bundled in the kit, to lower the noise floor and reduce distortion.

But the core of this modification is to give your C1/C3 the same frequency response as a U87.

Don't believe it? Here's proof.

C1/U87 frequency comparison

We recorded a passage into a modified C1 and a U87Ai, side by side, and produced an averaged frequency plot for each track. The two traces very nearly overlap. Above 80Hz, these two microphones sound every bit as close to one another as any two U87Ai's. (Note that Neumann's spec for the U87Ai is ±2dB.)

Below 80Hz, the modded C1 is fuller, because we chose not to artificially roll off the lows the way the U87 does. The C1 has a switchable HPF; if you're close-miking a source and need to remove proximity effect, just engage the HPF. But the lowest octaves are there if you want them.

Customer Testimonials

We've sold hundreds of these kits, with wonderful results. We think it's the best ~$60 gear mod on the market. (And if you're not able to DIY, we can mod your mic for you.)

Here's what our customers have told us:

Now the C1 sounds fantastic! Tried it on my voice and acoustic guitar and the sound is amazing, compared to how it used to sound.

This mic, to my ears, sounds 100% better after the mod.

The highs are silky smooth – no longer thin and brittle. It seems like the upper mids opened up as well. I don't remember it sounding that clear in the mids/upper mids. Nice work!

It's unbelievable what this upgrade delivers. It changes a mediocre microphone into a seriously good one, which I found myself using in every session! Buying a second-hand Studio Projects C3 and upgrading it is possibly the most cost-effective way of getting a professional grade microphone short of stealing one!


We make 4 versions of this kit. Click on the photo of your mic for audio samples and more information.

Studio Projects C1 Studio Projects C3
studio projects C1, old and new studio projects C3, old and new