Few days ago I made a post about having problem with De-essing. Some of the guys suggested that I use Cardioid mic.

I had a Sennheiser MD 421 II that I haven't used in a long time(over a year). I decided to give it a try. I've kept it clean and took care of it. It's not brand new but it's in a good shape mic that was used lightly in a TV Station.

When I plugged it in, and armed my track to record vocals in Pro Tools 10 and 11, and after cranking the gain up on the mic, I could here a country/rock like song playing in the back ground. The sound becomes more obvious when compressing the sound a bit.

I tried many times in different DAW's with the same outcome. I thought of many reasons but I was wrong. I thought it could be a plugin or some kind or warez causing that even though my DAW is licensed. Then I thought it's my Mbox, but I've been using it for over a year with no problem. I've even recorded whatever song that was playing in the background and saved it in a track and I am sure I can record that again if you guys like to hear what I am talking about.

I am really confused about this and have many questions now.
-Do these kind of mics or any mic have in impulse response of some sort that's implemented in the mic system?
-What could be the problem?
-Had anyone encountered such a problem with MD 421 II or other mic?

By the way, the song in the background sounds like it's playing on radio with bad signal. I also googled for similar topics and found nothing. I am sure that mics should have a clean signal with no crazy music playing in the background if I am recording or not.

It's making me crazy.

Any help is appreciated in advance

 

Cable Terminations
Inspect the mic cable's connector terminations. I mean visually inspect, not just assume, their correctness. Make sure that the following terminations are present:

- On phantom powered mics (and other mics with XLR three-pin connectors):
Pin #1 and the ground lug of each connector's housing must be connected together, on both cable ends!

Pin #1 of the XLRs must then be connected to the cable's ground wire. If the cable does not have a dedicated ground wire, the cable's shield must be connected to pin #1. If the cable has both, ground wire and shield (Gotham, Neumann), connect both to pin #1 of the XLRs.

Beware of certain connectors (some Neutriks comes to mind) which do not have a separate ground lug termination point for the connector's housing. Do not use these connectors on mic cables, as the connector shells cannot be grounded.

When you are done, do the following test to confirm the correct connections:
An ohm meter's leads connected to both connector housings should read zero or a few single digit ohms. If it reads open, go back and inspect what's wrong, or you will get RFI!

On tube mics:
Connect ground wire and cable shield together to the pin of the connector that is dedicated to ground and install a wire from ground to make contact with the connector's housing. This connection is often conveniently made at the cable strain relief, where a clamp is screwed into threads of the connector housing.

Again: install this ground/shield scheme on both sides of the cable, and when done, perform the ohm meter test, as described above.

This method of termination is always applicable for microphone cables, except for rare multi-connector hook ups (I won't get into this here.) Please do not mix up correct RFI terminations with what you have learned about terminations to prevent ground loops- there are no ground loops with mics and their cables, as they are single ended.
The terminations described above also happen to be the official Neumann recommendation.

Gunnar Hellquist adds:

Quote:

The microphone should be electrically insulated from the holder and hence from the stand.

If not, the mic is no longer ground loop-poof, as contaminating electricity, picked up from somewhere else, may flow through the conductive mic stand to the mic)


2. Cable material
I will not discuss advantages of certain cable brands, or their effect on sound. (I recommend and endorse, without payment, a specific microphone cable- Gotham, Switzerland)
I will share though, that in several independent cable tests for RFI susceptibility, one of them in an official AES paper, cables with double Reussen layer shields were provably more resistant to RFI than any other method of cable shielding.

Reussen layer cable shields are nothing else but multi strands of copper wire twisted in a cork screw fashion around the cable conductors. A second layer is then twisted in an opposite direction over the first. This is visibly different from braided shields or foil shields.

To my knowledge, only Neumann, Berlin, and Gotham, Switzerland (whose Reussen cables are now made by Belden in Germany) use this type of shielding.

My experience has been that in nasty cases of RFI, this type of cable, in combination with proper terminations cured the problem when correct terminations alone did not.

3. Chokes
A choke is a wire coiled in such a way that certain frequencies of audio when it passes through the coil, are suppressed.
Typically these choke coils, which in mics are very small and look like resistors, are inserted in series at the balanced outputs of the mic.

This method of RFI suppression really works well- like a sledge hammer on mosquitoes: The deterioration of sound from choke coils ranges from subtle to unbearable, depending on the value of the coil chosen.

Typical values of coils factory installed in mics range between 40 and 100µH (choke coils are rated in µH.)
I have found that anything above 25 micro-Henry is not tolerable, as the coil effect pretty much messes up the phase of the midrange of the mic's audio.


4. Ferrite beads
Schoeps pioneered the use of tiny hollow magnet beads inserted over the wires of the impedance converter inputs, i.e. the ferrite bead is inserted over the FET's gate wire or the tube's grid wire. The magnetic effect of these strategically placed beads interferes with the RF component of audio (don't ask me how it works)

 

Thanks for the quick and extensive reply
I will surely check my connections and cables and give it a shot.
In case I still have the same result, I will take my mic and cables down to a music gear store in town and have it tested.

thanks again and really appreciate you taking the time to help

 

This makes me think of a long time ago I was pretty sure I could hear phone calls,
It really surprised me, the first time I thought I had to stop using liquor and drugs at the same time.
only explanation I have is that some of these connections are not encoded (dect?)

In porta-studio situations it's best to have Mic cables around the exact length you need, if you don't want to spend to much time and cash looking for a cable made of diamonds harvested on a full-moon late at night by elves. and ofc, all the pins have to be connected

 

Once upon a time, our bassplayer got russian short wave radio signal into his amp. It was distant, grungy and faint. We were all like "WTF?!" when we heard that strange russian voice. For swedes like us it was pretty scary, especially when rehearsing at 2am at night.

 

The enemy comes from the east.

 

What if they take the long way around the globe? Then they come from the west. Surprise!

 

What if we're surrounded and now have nowhere else to run?