Our Objective Tests

I used a TEF 20 measurement system to make quasi-anechoic measurements of each microphone, using my B&K 4007 as a reference. Although these measurements are relatively informal, and may differ somewhat from manufacturers’ published specs, there was reasonable agreement between what manufacturers claimed, what we measured, and listeners’ comments. I performed the battery of measurements twice, on separate days, using different setups, and got similar results.

Frequency Response

Unfortunately, in 2005, I no longer have the response charts I made for these tests. You’ll have to make do with my text descriptions. Sorry about that!

These measurements are fairly reliable down to 100 Hz. Sensitivity is relative to my B&K 4007, which was documented at: 94 dB SPL (which is 1 Pascal, propeller-heads!) yields -53 dBV electrical output.

The AKG’s response is quite flat from 100 Hz. to 3 kHz. At 4 kHz there is a sharp and narrow peak of 4 dB, and then a slightly ragged elevated plateau from 5 to 10 kHz, where the output begins to roll off rapidly, falling 12 dB by 20 kHz. The broad boost from 5 to 10 kHz. is a typical quality of large diaphragm condenser mics. The narrow little spike at 4 kHz is a little more problematical, being right at the frequency where humans are both most sensitive to sound and most likely to have hearing loss. Due to its narrowness, its audibility will vary widely as a function of the program material. In general, the response looks quite respectable, except for the rolloff above 10 kHz.

The Audio Technica response curve looks extremely good from 100 Hz., where it may be down 2 dB, to 10 kHz. There is a gentle 1 dB dip from 3 to 4 kHz and a similar gentle peak from 5 to 8 kHz. A narrow 3 dB notch at 9 kHz is probably inaudible and between 10 and 15 kHz there is a 3 dB peak. The mic is down 5 dB at 20 kHz. In general the mic seems quite flat with the exception of the 3 dB peak in the 10th octave.

The Audix has much lower sensitivity than the above mics, with a measured nominal level of -58 dBV at 1 kHz. Output is down 4 dB at 100 Hz. and starting at 2K there is a broad 5 dB peak that extends to 12 kHz, with a slight, probably inaudible, notch at 8 kHz. From 12 kHz the response drops rapidly so it’s down 20 dB by 20 kHz. The low frequency rolloff means this mic will sound probably somewhat lighter and thinner and the peak will give voices an edge, hardness and/or brilliance. As we will see, this curve is quite reminiscent of the Shure SM58.

The Beyer mic is quite flat, with gentle 1 dB swings in response between 1 kHz and 15 kHz, where the output begins to fall off (down 5 dB at 20 kHz.). This response looks excellent, with the slight high frequency boosts probably adding a slight edge, brilliance or sheen to the sound. Whatever, this response curve looks quite respectable, even excellent.

The pretty impressive curve of the B&K serves to confirm the response of my 4007 (I had been curious if the two mics would agree as they were supposed to). Essentially we have a 1 dB variation from 100 Hz. to 18 kHz, and then the response is down 3 dB at 20 kHz. In the real world of acoustics, this is flat response! One would assume that such a mic will “sound great.”

The low frequency response of the Neumann is really flat up to about 1500 Hz. From there to 15 kHz there are two broad, not very deep (-2 dB) dips, the broader one centering at about 5 kHz. Above 15 kHz the response rolls off, falling 7 dB by 20 kHz. This response curve, with its slight loss in octaves 7-9, will tend to darken and smooth sound quality. My instinct is that it will sound terrific recording orchestral strings. It doesn’t look particularly appropriate for pop vocal recording.

The Sennheiser curve is somewhat more problematical. There is a pronounced rolloff (5 dB) below 200 Hz. and then a broad 5 dB peak or peaks starting at 1 kHz and ending at 15K, so that the generalized output is up 5 dB really across octaves 7-10. The slight raggedness of the response in this range will probably lead to changes in sound quality with different voices and contexts. The output falls 9 dB from its nominal level by 20 kHz.

The Shure’s response is characterized by the double peak at 5 and 9 kHz, followed by steeply falling response (20 dB down and off scale by 18 kHz.) I have used this mic a lot to good effect. Aside from rock recording, it really works in live sound reinforcement work, giving an edge, a focus and bite to voices that really helps their intensity in many performance situations.

Directional Response

I took response curves at 30° and 180° off-axis. All of the microphones exhibited good behavior at 30°, being smoothly and consistently down about 2-3 dB up to 10 kHz. Rejection at 180° was good at the middle frequencies, but less good at low frequencies (as I expected) and high frequencies (which I did not expect for the cardioid mics). Be aware that these microphones, except for the B&K, do not reject high frequencies all that well (only 5-10 dB).

Sample consistency

I compared sample-to-sample consistency in six of the seven of the mics which came in pairs (one was defective) All compared were within a dB across the response range with the exception of the Audixes, which showed a few inconsistencies of greater than 1 dB. The Shures and the B&Ks both exhibited consistency of considerably less than a dB.