Photograph 1. Photo courtesy of Andreas Schulz and leftover-visuals.de.
Since the days of MTV unplugged, many working bassists who would normally rock to a solid electric body have broadened their sonic palette with an acoustic bass guitar. When it’s not practical for a band to play with a concert drums and backline – perhaps an in-store promotional gig, a radio station, or an intimate show – an acoustic bass allows low-enders who don’t. not play standing up to hold down for their flat mates. Although such performances are generally referred to as “unplugged”, the bassist still needs amplification to raise the acoustic bass above the volume levels of the campfire.
Even when there is no electricity involved, we face the same problem with our low frequency acoustics as when we plug in our solidbodies. Remember that compared to electric guitarists, we need a lot more power to boost our signal to a useful level. Likewise, an acoustic bass needs a lot more body volume and soundboard area to keep up with an acoustic guitar, but even with the oversized body of the Stoll acoustic bass (Photo 1), you may still not be on par with the rest of the group. So, once the audience reaches a certain size, you’ll need an amp to be heard and, more importantly, the right mic. Sorting through the plethora of collection systems can be confusing, but luckily they all boil down to a few principles.
Magnetic. As long as you’re using nickel or steel strings, magnetic pickups run on acoustic bass, and you don’t need a preamp to generate usable output. Unfortunately, magnetic pickups often sound more like an electric bass, as the cutoff peak prevents higher frequencies from passing through. (For more detailed information, read âPassive Tone Controls.â)
Sorting through the plethora of collection systems can be confusing, but luckily they all boil down to a few principles.
Optical. This is not really an option, as no manufacturer currently offers an optical mic for acoustic bass. But if you’re curious about how this technology works, check out âPiezo and Optical Bass Pickupsâ.
Microphone. A good mic might be the perfect transducer, but internal and external mics are often plagued by feedback. Crosstalk is another difficulty that microphones create for a sound engineer. (Contact microphones are still microphones, but they fit better into the next group.)
Contact pickups. Although “contact” is not really a principle of operation, this group contains all piezo, electrostatic, and electrodynamic transducers, as well as contact microphones. These devices pick up vibrations in direct contact with the instrument and produce little feedback and almost no crosstalk. Despite their often inferior sound quality, inexpensive contact microphones, especially the piezo variant, are the most popular transducers.
Contact microphones are available in many different designs and technical constructions. But since most bassists spend their money on their primary instrument, the electric bass, it’s no surprise to see a secondary bass rigged with a cheaper system. This is why many players opt for a single piezo pickup under the saddle. The high-impedance output of a piezo pickup requires an active buffer or preamp, partially negating the price advantage, but having built-in access to your main controls is a plus given the sensitivity of amplified acoustic instruments.
Photograph 2. Photo courtesy of stollguitars.de.
Essentially, an acoustic bass guitar bridge consists of a simple plastic or bone saddle that sits on a piezo tape with the same footprint. Photo 2. The upper face of the saddle serves as the point of intonation and determines the action, while its underside presses on the piezo. A piezo element is very sensitive, and the simplicity of construction often poses problems when it comes to picking up strings at equal volumes. In particular, the outer strings can lose bulk if a weak saddle bends upward at the ends. A poorly routed saddle slot can also cause volume irregularity. It’s less of a problem today, thanks to the CNC routed slots.
If you’re having string-to-string volume issues, your best bet is to start by lightly sanding the underside of the saddle absolutely flat. But the key word is slightly, because it also affects the action. If the problem persists, your only solution is to sand the areas under the strongest ropes. It can be a long process of trial and error, but it’s the price we pay for using budget technology.
The problems aren’t limited to the bottom of the contact area, either. On a purely acoustic instrument, you want the saddle to fit snugly into the slot. But if you are using a mic under the saddle, make sure the saddle can easily move up and down to reflect the movement of the strings. However, if he obtains too much loose, the saddle could tilt and put more pressure on an outer side instead of the entire piezo element. Even adjustment on all ropes is one way to prevent the saddle from getting caught out. It sounds like a pretty sensitive system, but it works most of the time.
More complicated solutions can overcome these problems (sometimes spawn new ones) and even add tonal value, a topic worth considering in another column.