Comparing Microphones

[Stub Mandrel]

I've been experimenting with testing microphones. I used a Scarlett interface into my laptop and Friture to produce Mel & A-weighted spectrograms.

I used a HH Vector 8" producing pink noise over bluetooth as a sound source.

 

Speaker and mic 1.25m apart and 1.25m above the floor in large room with lots of soft furnishings, curtains.

 

Most obvious thing was the speaker had limitations, as you could see the same notches across all the mics.

 

The flatest response was... a £30 generic BM800 mid-sized condenser microphone. Often used with 5V from a PC, these run well on 48V phantom power and are very sensitive. Lots of hacks for their circuit or putting larger inserts in them. I haven't modded this yet, but it gave the biggest signal and flattest curve with widest frequency response of all the mics I tested...

 

I think this gives the best idea of the HH Vector's output. Note the dips at 4500 and 5500Hz which I guess may be the crossover frequency.

 

 

My other condenser mic - Behringer C2, used flat and with low cut, which drops around 3dB from around 1000Hz ish. Interestingly the 5500 dip is not very pronounced.

 

 

 

I think I need a better white noise source before repeating the experiment... things are going on for different types of mic, but I don't have confidence the sound source is flat enough to draw meaningful conclusions on anything but the sensitivity and the extent of the high/low frequency response.

 

 

If anyone can recommend the ideal spectrogram settings, better software (Friture has no manual and appears to lack a simple save screenshot function) or any advice at all, all welcome!

Edited 2 hours ago by Stub Mandrel

[tauzero]

You might want to have a look at sweep frequency generators - these generate a single variable frequency sweeping typically from 20Hz to 20kHz, and so you can get a frequency response by mapping amplitude against frequency.

[Stub Mandrel]

11 minutes ago, tauzero said:

You might want to have a look at sweep frequency generators - these generate a single variable frequency sweeping typically from 20Hz to 20kHz, and so you can get a frequency response by mapping amplitude against frequency.

 

Good call. I asked Chatgpt for advice and that was one recommendation.

 

Another was to use software that allows me to calibrate using a reference mic... I know someone who may lend me one.

[tauzero]

There is a very elderly website that has at least some relevant information - https://www.ymec.com/hp/signal2/index.htm

[tauzero]

@stevie and @Phil Starr might have some suggestions - after all, measuring speaker frequency responses with a specific microphone and measuring microphone frequency responses with a specific speaker are two sides of the same coin.

[itu]

1.25 m is a very unstandard measure. Use 1.00 m as a reference. 

 

Although your room has furniture, it is recommended to have a space that has minimal amount of reflections and reflective surfaces. They tend to boost suitable frequencies. 

 

Measuring a speaker, beware: the placement of the microphone can boost the low or the high end. 

 

You should have a calibrator to your system. 

[Stub Mandrel]

I'm seeing as little as 0.6 to 0.5m being recommended for 'living room' calibration.

 

Our vocalist has said he's happy to lend me his reference mic and I've found better software.

[Dan Dare]

The thing that strikes me from the plots above is how broadly uniform most are. The major peaks and troughs occur at similar points for many. 

[Stub Mandrel]

2 hours ago, Dan Dare said:

The thing that strikes me from the plots above is how broadly uniform most are. The major peaks and troughs occur at similar points for many. 

 

The inadequacies of a fairly basic powered speaker are hiding the true responses of the various mics. Does show how much influence PA can have on your tone...

[Dan Dare]

1 hour ago, Stub Mandrel said:

The inadequacies of a fairly basic powered speaker are hiding the true responses of the various mics. Does show how much influence PA can have on your tone...

 

Yes and no. Given that they are all fed through the same speaker, differences should still be apparent. Certainly, nuances will be less obvious, but I think my overall observation stands. I appreciate the importance of a quality PA. I have one. I find that most mic's,  barring the really cheap and nasty. give a decent account of themselves through it. Sometimes, an El Cheapo can surprise you, as you found with your BM300. It's still the case, as it always is, that some will suit certain voices and instruments better than others, but I find differences are not massive in the main and can often be compensated for with eq.

[Stub Mandrel]

1 hour ago, Dan Dare said:

 

Yes and no. Given that they are all fed through the same speaker, differences should still be apparent. Certainly, nuances will be less obvious, but I think my overall observation stands. I appreciate the importance of a quality PA. I have one. I find that most mic's,  barring the really cheap and nasty. give a decent account of themselves through it. Sometimes, an El Cheapo can surprise you, as you found with your BM300. It's still the case, as it always is, that some will suit certain voices and instruments better than others, but I find differences are not massive in the main and can often be compensated for with eq.

 

Yes, but they are quite subtle and hard to see aside from a few obvious things... the condenser traces (three at top right) have MUCH higher frequency response and are much more sensitive. The drum mics and the (very old, cheap and nasty) Ross 338 have better low end, even though the T-Bone one has a cheap as chips insert chosen for a claimed good low-end response (it also has very low sensitivity). The SM58 is low sensitivity as well.  Some have a distinctly lower response below around 32kHz and a few have apparent extra dips and peaks, but hard to be definitive.

[Beedster]

Excuse my ignorance but why are you testing microphones, especially given they all appear to be giving you similar results? Not criticising, just genuinely interested, all seems a bit eccentric in which case I'm with you 👍

 

BTW I went quite mad trying out various permutations of my Townsend L22 Sphere, wish I'd stuck with my SM7-Bs to be honest