Spectrum analysis of a few of my microphones

[link=http://stabilitynetwork.blob.core.windows.net/g-tunes/MicStudy.html]http://stabilitynetwork.b.../g-tunes/MicStudy.html[/link]
 
I was looking at an old microphone that used to give me trouble and I cranked up the gain and looked at the Spectral Analyser and was really surprised by what I found (quiet room basically recording nothing really loud).
 
My cheaper microphones are flatter and my more expensive ones have a boost in the low end. This wasn't what I expected to find.
 
I snapped all the screen shots of the Spectral Analyser with the mics on a soft cloth pointed towards the wall (more or less in the same spot). Mics that could be put face down were. The room isn't silent. The AC was running (not near by it blows in the room). In almost all cases the gain was totally cranked.
 
Anyway, I was surprised by my findings.
 
Edit: Maybe I'm looking at this wrong. Maybe the main difference is in whether they are condenser mics?
Edit2: Well, that's out. The only dynamic in the bunch is the SM57.

9Mike, I really appreciate you responding to my post. I am very grateful that you are here.

I'm not at all surprised to find that my test was REALLY bad. :-)

I didn't start out testing the microphones frequency response at low levels. Actually, the MXL V69 used to give a soft fluttering sound at very low volumes. At lunch yesterday I was wandering around Guitar Works and Sam Ash and I wondered if my problem might go away with my new interface (got it last November at Guitar Works).

So, once my kids homework was done I broke out the MXL V69 and cranked the gain. I didn't used to have the nice tools that come with the RME. I didn't even have Sonar open b/c I wasn't aiming to record. And interestingly (happily) I didn't hear any flutter sound from the MXL V69 when the gain was really cranked. I noticed it didn't need phantom power and wondered if that had caused the problem from my old interface. When I turned on the phantom power, I didn't hear a problem.

This mic has been on the shelf for years now because of the soft fluttering noise it generates that the others do not. Last night, I did not plug the microphone into my old interfaces to see if the soft fluttering noise returns. The pre-amps on my M-Audio are wrecked for some reason. I can only use separate pre-amps (my RME or my Art-Tube Pres (2)) so I'm not sure if the test would be good anyway... also, as long as it works, who cares where it doesn't work.

I can say that after buying it I replaced the tubes in it several times trying to resolve the fluttering sound and eventually just gave up.

Anyway, that's the background for how I came to the test. The soft cloth was sitting on top of my Tascam 2488. It's an old tie-dyed tapestry I use as a dust blanket over a shelf of gear. When I'm home it's in a pile on top of the Tascam (which has the roof spot on my rolling shelf). RME and Compressor have lower shelf and bottom shelf is reserved for often needed items like headphone splitters, cables, microphones etc.

My test was inconsistent. It was not in an Anechoic chamber. RTA = Real time analyzer? Yes, if my chair creaked or I breathed the results of the Spectral Analysis would jump to high heaven. I don't know how I could really compare them fairly. they point differently. I don't have those rubberbandy shock mounts for all of them. Some just click into regular mic holders.

Anyway, your response is very helpful. Just pointing out the things that are wrong with my test really helps me get a better grip on my gear. My favorite mics aren't going to change because of this test. Years of listening to them has earned them their rank in differing tasks.

I continue to just think this hobby is the most awesome fun. I appreciate you teaching me!

Bit,
 
You don't you think that there's something to be said for the fact that all the Microphones were put in the same place? I'm not saying that the test was perfect by any means. Perhaps so flawed as to be fully misleading, I'm not sure. I guess, I was feeling that the test may actually demonstrate something. The microphones showed consistent and similar characteristics. You could never use data like this to sell microphones, but being the owner of them, I felt like I'd learned something. I think that whether it's the room or the Mic, that some of my mics get a better bass response and those are the ones I prefer.
 
The information was not what I was expecting to see, and for that reason, I thought it was particularly useful. Also, while I didn't snap screenshots I did move the microphones around the room. I got somewhat similar results in lots of different positions.
 
I also think you can see the fan around 1000+-.