I have a U87 copy and am noticing distinctly different frequency responses comparing one side to the other. The front sounds normal, but that back side, there is a noticeable drop off in high frequencies.

Normal or should I expect better?

You have the mic in figure of eight and you're talking into the mic with headphones on, right?

Try it with someone else talking.

So, I'm talking into one side of the mic, then rotating the mic 180 degrees and I'm hearing a high frequency roll off. The mic is functioning in a figure of eight pattern, room acoustics should be relatively the same.

No. Welcome to the wonderful world of physics and acoustics.

The topic for today is Polarity. Your U 87 Copy has two diaphragms. They sit back to back in the capsule.

When you have them connected with the same polarity. You have an Omni pattern.

Reverse the polarity by reversing the leads of one of the diaphragms and you have a figure of eight pattern, .

When you speak into the front capsule and listen to yourself with headphones. You sound normal. When you speak into the rear capsule you don't because you are listening to your own voice with REVERSED polarity.

That's why I wanted you to have someone ELSE talk into the backside of the mic. To you, if you were listening on headphones, they would sound fine either way because it's THEIR voice not your own you're hearing. OTOH, if THEY were listening on headphones to THEMSELVES, their voice would also sound wonky when they spoke into the rear capsule.

Extra Point: There is a spectrum of patterns. On one end of the spectrum are all Omni patterns.. On the other end of the spectrum are Figure of Eight patterns. Every directional mic there is exists somewhere on that spectrum.

Lesser known fact #1 : Sometimes in a ribbon mic capsule, the diaphragms are moved slightly to the front in the gap between the magnets.

Lesser known fact #2 : If you have some mis-wired mic cables that reverse pins 2 and 3. They reverse the polarity of your connection and the front side sounds funky and the back side sounds OK. The Rule for cables has been discussed and argued for decades, but, as far as I know, the latest outcome was. "**** you. It's Pin 2", meaning that Pin 2 is for the positive polarity and Pin 3 is for the negative. Pin 1 is for ground, btw.

Yeah had the same thing on my KSM44's I had a few, it was my expectations it was to be the same identical on both capsule sides but there was some weirdness and not the same. I figured that's the way it is...they all sounded the same so it wasn't a one off mic thing.

never tried it with someone else in the other side, same time, fig8 mode back-side capsule diaphragm. I didn't care really, its in cardiod 99% of the time.

Just to clarify what Ty is saying, it's about interference between the sound going into the mic and being played through your headphones, vs. sound being conducted physically from your vocal cords via your body and skull to your ears (and I guess to some degree by the air immediately you, at low frequencies.)

The mic is usually wired so that positive pressure on the front of the mic will cause a positive voltage on pin 2, but positive pressure on the back of the mic will cause a negative voltage on pin 2. (Usually the voltage on pin 3 is the reverse of pin 2.)

If the mic is wired normally, the sound in your headphones will be in phase with the sound conducted through you to your ears, if the mic is pointed toward you, and add postively, but it will be out of phase and largely cancel out, especially at low frequencies, if the mic is pointed away from you.

If your mic sounds thin when you do that, but not when you listen to someone else talk, it is likely wired backwards.

Many very cheap Chinese mics of the BM-700 / BM-800 type are wired backwards. You can fix that by switching the wires that go from the PCB to pins 2 & 3. (Those are cardioid-only mics with only one diaphragm, but the same principle applies.)