Pickup Combinations - Who Uses What, and Why?
by Greg Gualtieri
President, Pendulum Audio, Inc.

Pickup Combinations - A Primer

Since we've been in the business of putting together preamp systems for acoustic instruments longer than anyone else, we've come across most of the configurations that players would like to use with their instruments. The bottom line is that nearly everyone wants something different, and needs a different approach to achieving it. For that reason, we've tried to incorporate as many features as you're likely to need both now and in the future. Since most players find that one pickup can't do the entire job, the SPS-1 is designed specifically for blending a pickup with something else, be it another pickup, an internal mic, or an external mic. What combination you choose depends a lot on your playing style - flatpicking or fingerpicking, playing solo instrumental music, accompanying vocals, or playing with other instruments at high sound pressure levels. Even whether you play in small clubs or with a concert sound system. The choices you make also depend on whether you're playing live or in the studio. Here are a few of the most popular combinations, and why people use them.

Two External Mics

The faint of heart need not apply! If you're a purist, and you're playing solo guitar in a studio environment, this is the combination you're most likely to use. However, it requires a pair of high quality condenser mics, and a great sounding room. Since the SPS-1 has two studio-quality mic preamps, parametric EQ and stereo output, it's the ideal preamp for going directly to DAT or digital multitrack. Perfect for recording you solo record yourself. No one would think of using this combination live, however, and expect to be heard. Unless, of course, you're doing a classical concert in a great European hall.

Pickup + External Mic

This is probably the ideal combination for solo acoustic performance, when you're looking for a good representation of the sound of your instrument but want some control over how 'woody' your guitar will sound. In most cases the pickup will be some sort of string-sensitive device, either a saddle or under the saddle piezo (that's pee-ay-zo folks, not pee-zo or pie-zo) transducer or a magnetic soundhole pickup. Some work better than others, some are easier to install, and some are just awful! The idea here is to use the pickup to provide the direct 'in-your-face' sound of the vibrating string, and combine it with the ambient sound of the wood vibration the external mic gives you. By varying the blend between the direct and ambient sound, you can get a very reasonable representation of your instrument. You can use more pickup in a very lively room, and more mic in a dead room.

By using a single pickup or two pickup Preamp Module in one channel of the SPS-1, and an external mic in the other, you can have complete control over this blend on stage. Many players find that piezo transducers flatter light fingerstyle playing, but are harsh when the strings are hit hard. The best magnetic pickups, on the other hand, don't fold up when played hard, but are too 'round' sounding for players who prefer that 'brash' piezo sound. The choice is up to you. Check out what your favorite player is using, and see if it works for you. In addition, most studio recording of acoustic instruments also relies on using these two sound sources. During mixdown you can establish the blend of pickup and mic that gets the guitar to cut through the mix. The downside is that you have to have to stay glued to one position for the mic to be effective. This doesn't work for everyone. And, you can't use this setup with high stage levels or in a band situation, since both feedback - and more important - leakage of other instruments into the mic, will present major problems. Mic selection and placement will often help solve some of these problems, but not in all cases, or even in all rooms.

Pickup + Internal Mic

This is currently a hot combination, since it gives you the benefits of an external mic, and you can move around. There is a price to be paid, however, since a mic inside a guitar will never sound as good as a mic out in front of your guitar. It may come pretty close, and in many cases it works very well, but it's still a compromise. After all, it's is a mic in a box. All that said, it works quite well in many applications, particularly for solo players or groups where the stage levels are low. The problems encountered with external mics, namely feedback and leakage, are also problems here. Feedback problems can usually be cured by keeping the mic out of the stage monitors, which the SPS-1's monitor output allows you to do. Leakage, however is another matter. The mic is in a resonant box with a hole in it, which acts as a 'magnet' for low frequency sound, particularly drums and bass. You can roll off all the low end on the mic, but isn't that what you wanted the mic for in the first place?

A word about soundhole covers: You may think that by blocking the sound hole, you're blocking external sounds from reaching the internal mic. This is true, but you're also preventing air from moving inside the instrument. If the air doesn't move, neither does the diaphragm of the mic. Consequently, the output of the mic drops dramatically, and sounds pretty dreadful. Venting the cover by putting a few holes in it sometimes works, but often the results are less than satisfactory. Sometimes you see a gauze pad over a soundhole, which lets the guitar 'breathe'. It only attenuates high frequency leakage though, not kick drum and bass.

Mic placement is another matter. The two most popular positions are at the 2:00 or 5:00 position (neck is 12:00, bridge is 6:00), tucked inside the soundhole about 1-2", 1" below the top, and aimed out at the strings. At certain positions inside the instrument there are 'nodes' where the low end boominess is less severe. Hunt around until you find a position that sounds best without EQ. Some mics are less boomy to start with, particularly hypercardioid capsules. Sometimes, pointing the capsule up directly at the top, as close to the top as possible without touching (sort of a PZM configuration), works well with large-body instruments. A little time searching for the best position will pay off in the long run.

To sum up: internal mics work well when stage levels are low, the mic is kept out of the monitors, and you've invested some time in hunting for a sweet spot inside the guitar.

Two Pickups

If you're playing in a band, and it's loud, you can rule out any type of mic. In this case, there are a couple of options. You can get a 'woodier' sound by blending a string-sensitive pickup with a contact piezo transducer mounted to the top. Although the contact pickup can feed back, the feedback occurs at the cavity resonance of the instrument, which can easily be notched out with parametric EQ on the SPS-1. The advantage, of course is that leakage is no longer a problem. You won't get the sound of the pick or your fingers hitting the strings, but at high sound levels this isn't a great sacrifice. You will get some body noise, though - the sound of your shirt sleeve scraping against the top, or your perspiring forearm peeling off the top.

Another alternative is to blend two string-sensitive pickups. A common combination is a saddle piezo pickup blended with a magnetic soundhole pickup. Here, you're getting two different tonal colors which you can blend to your liking. The piezo transducer is great for that brash, 'in your face' sound, and a biting attack. The magnetic pickup is ideal for getting harmonics out of your instrument (especially for tapping), and does very nice things for slide playing. It definitely opens a lot of possibilities.