A Simple Mic Comparison

Since I've been doing home recording, I've diligently read Internet postings and sites about microphones. I've upgraded my equipment several times, and my recordings are better now than when I started. But I'm not at all sure that the improvement is due to the equipment changes.

Since I have a small variety of mics, and four channels of recording capability, and a T-bar for mounting several mics in close proximity, I decided to attempt to compare some of these mics by recording a very brief clip of solo acoustic guitar.

Test Design

In order to minimize proximity effect and reduce variations due to small differences in position, I placed the mics 18 inches from the guitar. I used an M-Audio DMP-3 and Omni I/O for the mic preamps. The soundcard is an M-Audio Delta-66. The computer is a Dell Optiplex GX-150 with a Pentium III 1Ghz processor and .5 GB of RAM, chosen for its very low noise levels. The software is Cool Edit Pro.

The guitar used for the comparison is a Martin OM-18V, a mahogany and sitka small bodied acoustic. I play Hawaiian slack key nearly exclusively, so the guitar is tuned to Open G, and played with bare thumb and fingers.

Instead of normalizing to get consistent volume levels, we used FM radio static to attempt to match levels before recording. The precision of this matching is not very great, so there are inevitably some level differences. This factor alone may make these comparisons misleading and of little value.

All tracks are mono, 16 bit, 44.1khz, wave files. Since they're .wav files they are quite large, about 1Meg for about 11 seconds of audio.

The room is a rectangular drywall space, light carpeted floor, and two walls lined with vinyl LPs.

I can only record four inputs at one time, so I use one mic as a reference in each test. Thanks to a suggestion by Arny Krueger on the Usenet news group rec.audio.pro, I've included a Behringer ECM8000 omnidirectional measurement mic as the control mic in each batch.

Here's a picture of the mic mount. This is not a picture of any of the actual batches described below, just something to give you an idea of how the mics were positioned.

For your Consideration

This is a very non-scientific comparison, and a very limited one. The sound source is my thumb, which is a LOOOONG way from a precision instrument. I measure each position, but there are inevitably small variations. To compare mics between batches, you must compare within each batch to the Behringer ECM8000, and include that comparison in your evaluation. Even within batches, the lack of precision tools for matching levels makes the listener's job very hard. Psychoacoustically we much prefer louder clips, so the slight level variations that slipped through may make it impossible to effectively evaluate the results.

Probably the most important thing to consider is a point raised by Ty Ford on the rec.audio.pro usenet newsgroup. Mr. Ford is a very experienced recordist and evaluator of recording equipment, and he pointed out that getting the best recording requires finding the correct position for that mic on that guitar. Any of the mics here might do a MUCH better job if we moved it around until we found its sweet spot in relation to this Martin OM-18V. So listeners should always bear in mind that we're quite likely not showing any of these mics at their best.

Thanks

Arny Krueger, for the informative responses to the first test on rec.audio.pro, and the suggestion of the Behringer reference mic. Mike Rivers and Ty Ford, for additional insightful comments. And especially to Doug Young, who provided his Neumann KM-184 and TLM-103 mics to expand the scope of these comparisons.

A Simple Mic Comparison

Test Design

For your Consideration

Thanks

Batch 1 - Small Diaghragm Condensers

Batch 2 - The Good Stuff (or at least the pricey stuff)

Batch 3 - Omnivores

Batch 4 - The Dynamic Duo (and an odball)