U47 clone pattern switching loud pop and amplitude change

[living sounds]

I've built an MK47 that works well in cardiod mode, however, switching patterns to omni gives a very loud "pop" sound and the front capsule sounds weaker and thinner, while the back side is fine.

All that switch does is close the connection so both capsules are in parallel.

Any idea what could be wrong here and what to check for? Thanks!

 

[shabtek]

switching polarizing voltage to the most amplified and microphonic part of the circuit will cause a pop if you leave the monitors up

as for response anomalies in omni IDK, i'd be tempted to switch capsule connections front to back and see if it changes

 

[Tubetec]

If you look at the spec of many LDC mics you will find the sensitivity changes depending on polar patern , its normal

Maybe you have capacitive imbalance in the capsule ,or some leakage on one side thats dragging the response down.

 

[Tashi]

You might’ve tried but start by ruling out the capsule - try swapping the leads front and back

 

[gyraf]

..and remember that you are supposed to loose the proximity effect when in omni - your "weaker and thinner" could just be absence of proximity effect..?

/Jakob E.

 

[living sounds]

Thanks guys, I will switch the wires.

Yes, overall differences with omni vs. cardiod are normal, but in this case the front capsule sounds normal in cardiod but weak in omni, while, the back capsule when engaged sounds fine (very similar to the front capsule in cardiod, minus proximity). In omni the front capsule is several dB weaker than the back capsule.

 

[Tim Campbell]

Perhaps you have the wires to the front membrane and backplate reversed or just a defective capsule

 

[shabtek]

in omni are you monitoring live on headphones or a recording and at what distance?

 

[living sounds]

Perhaps you have the wires to the front membrane and backplate reversed or just a defective capsule

Would a defective capsule still work properly in cardiod?

 

[living sounds]

in omni are you monitoring live on headphones or a recording and at what distance?

Recording, at the same distances to both front and back. It is very obvious.

 

[kingkorg]

Check capacitance between sides and how well they match. You need to disconnect the capsule wires from the board. You probably also have additional leakage from the switch.

 

[Tim Campbell]

Would a defective capsule still work properly in cardiod?

yes. If the rear membrane reads much higher capacitance than the front membrane it would be loudest.

 

[living sounds]

Check capacitance between sides and how well they match. You need to disconnect the capsule wires from the board. You probably also have additional leakage from the switch.

I've checked with a multifunction tester. The (current) front side reads below 80% of the capacitance of the back side.

I checked a chinese double-sided capsule with the same tester for reference, both sides are within a pf.

Next I switched capsule connections between front and back. The overal amplitude drops going to omni (not entirely unexpected) and the backside sounds strange, thin and phasy.

So it looks like the capsule might have a problem on one side...

 

[kingkorg]

Yes it has. You have a bad capsule.

 

[living sounds]

Any idea what might have happened to the capsule? Can it be damaged by overvoltage this way? From the outside there isn't any obvious damage.

So, I need a new capsule... has anyone here tried a Braingasm capsule? The other options would be Thiersch or Heiserman, I guess. Neumann doesn't sell them anymore. Any recommendation?

 

[kingkorg]

You should be able to tell if it collapsed, that would be the first sign of overvoltage. Other than that it could be a number of things or factory dud.

When it comes to choice of capsules that topic has been beaten to death, and well documented.

 

[living sounds]

You should be able to tell if it collapsed, that would be the first sign of overvoltage. Other than that it could be a number of things or factory dud.

Well, it doesn't sound bad on its own. Different, but not broken in any way. I don't know if it was working correctly when I installed it 10 years or so ago. It's a BeezNeez K7.

 

[Tim Campbell]

Has it worked properly in omni before?

 

[living sounds]

Well, it doesn't sound bad on its own. Different, but not broken in any way. I don't know if it was working correctly when I installed it 10 years or so ago. It's a BeezNeez K7.

That I cannot say, unfortunately. When I build it I was very much in the early stages of DIY and never needed anything other than cardiod patterns in mics. I seem to remember I found the omni mode funny, but since I didn't use it...

Though everything looks clean I will make sure and take apart the high ohm circuitry and mount the resistors away from the PCB. This might impair the performance as well... But I also need another capsule...

 

[Delta Sigma]

That I cannot say, unfortunately. When I build it I was very much in the early stages of DIY and never needed anything other than cardiod patterns in mics. I seem to remember I found the omni mode funny, but since I didn't use it...

Though everything looks clean I will make sure and take apart the high ohm circuitry and mount the resistors away from the PCB. This might impair the performance as well... But I also need another capsule...

K7 is a great sounding capsule. Send it back to Ben for repair. Order something relatively cheap to use while it's gone. If you can order a 3U or Maiku, you could even prefer it in the end. If you're thinking about another K47/M7 build in the near future (M49, etc), order a Heiserman M7 or something else high-end. Gives you the option to swap between them to find which capsule you prefer in which mic.