Tone in bass guitar amps can depend on many variables, from playing technique to the multitude of stompboxes and multieffects you use – but speakers are where sound truly matters.
When purchasing speakers for your bass amp, three main considerations must be kept in mind when choosing new replacement speakers: wattage, impedance and mounting hole layout.
Power
No matter where they’re performed, bass guitars require plenty of power to sound full and crisp. To maximize performance, often a power amplifier must be combined with a speaker cabinet; this pairing is known as a bass amp. Bass amps may use either tube (thermionic), solid state (transistor) technology or hybrid designs that employ both technologies, including preamp and power amplifier circuitry that utilize both technologies simultaneously.
A bass preamp is designed to alter the sonic characteristics of the bass signal it receives, typically tuning itself towards a particular tone. Once this signal reaches your speaker cabinet, it projects that sound into listener ears – typically using small (8″ or 10″) speakers for more controlled guitar sounds and smaller tubes for warmer or less distorted tones.
Wattage ratings of bass amp speakers typically consist of two components, the “continuous” rating and peak power handling capacity. The former measures how much average power the speaker can withstand without risking damage (for instance melting voice coils or softening adhesives that hold its components together), while peak power capacity refers to how much peak power can be handled temporarily during high peaks (e.g. driving the amplifier into overdrive mode).
As such, while a 100-watt bass amp may suffice for practice sessions, at least 200-watts will provide sufficient power to drive your speaker loud enough for performance in live settings. Furthermore, some bassists use bi-amplification techniques where high frequencies are split off into separate amplifiers and speakers for greater control over tone; John Entwistle from The Who has made this style well-known among bassists.
Frequency Response
Frequency response of bass amp speakers plays an essential role in their overall tone. A speaker amplifies only those frequencies it is exposed to, with its response curve dictating how much low-frequency information it delivers. Furthermore, each bass speaker needs to be tuned to achieve desired tone across its frequency spectrum, using components with excellent low and high frequency performance so as to prevent muddiness or harshness in sound production.
Typically speaking, the higher a speaker’s power handling capacity, the lower its frequency response will be. This is because high-power speakers require larger magnets and stiffer voice coils that make amplifying low frequencies less efficient; furthermore they may incur distortion modes that are undesirable, producing harsh and muffled sound quality.
Engineers designing speakers for bass amplifiers tend to aim for narrower frequency responses than those designed for other guitar amps, to filter out harmonics and overtones unsuited to bass music while stimulating desirable distortion modes that fit it better.
This can be achieved in various ways, including decreasing internal damping and changing speaker sensitivity. To get optimal results however, matching up speaker and cabinet together properly is paramount for success.
An ideal starting point should be to ensure the headphone’s output impedance (listed on its rating plate) matches that of your speaker impedance. Although this won’t cause immediate harm to either system, any difference will become apparent in terms of loudness.
Frequency response of speakers can also be enhanced through use of either a ported or sealed cabinet, which will help reduce resonance and air pressure within the speaker, and increase their ability to produce low-frequency notes. An alternate way of improving frequency response would be lowering amp gain while playing bass – this will minimize vibration with speakers, prevent damage to them and will save your speaker from having to work as hard producing low frequencies output.
Cabinet Design
Cabinets play an enormous role in shaping the sound of your bass amp. Additionally, they determine how much power each speaker can handle; larger cabinets often produce more low-frequency “boom,” so they must be properly vented to avoid thermal distortion at high volumes. Many bassists utilize multiple cabinet sizes in their rigs in order to cover all frequencies and venue sizes they play at. A typical combination would include 4 x 10, 1×15 and 2×10.
Closed back cabinets (often called sealed cabinets) feature no openings for gas to enter; therefore they’re gas tight. Closed back cabinets are most frequently found in older Fender, Marshall and Ampeg amps as well as combo amps used for practicing or lower power applications like tube combos.
Open-backed cabinets feature openings in the rear of their enclosure that draw air in from behind and push it out through front cone, a common feature in modern bass amp combos as well as standalone models.
When selecting speakers to replace those found on a bass amp, it’s essential that they possess similar impedance and power ratings as the originals. Your amp was created to operate with specific impedance levels in mind; using different-rated speakers could result in overloading it and damaging speakers over time.
Dimensions and porting play an enormous role in shaping tone; unfortunately they’re nearly impossible to predict without going deep into speaker specifications and heavy physics. You should also decide between an open back cabinet or closed back one; additionally you need to decide whether you prefer open or closed drivers for it.
Keep in mind that sensitivity measurements don’t offer much help for bassists; these numbers indicate how loud a speaker will sound with one watt of signal. To gain a truer picture of its volume level, compare various models prior to making your purchase decision.
Adjustable Crossover Point
A crossover is an electronic circuit that filters (divides) frequencies so only those you wish to hear pass through. There are three types of filters used: high-pass, low-pass and band-pass filters – high-pass discards all frequencies above or below an identified point while low-pass filters reduce frequency below it while band-pass passes any frequencies between both points.
Variable crossovers allow you to adjust the frequency of low-pass and high-pass filters so that your speakers are perfectly tuned with the overall sound of your system. In order to accomplish this, it is essential that you know both their sensitivity ratings and efficiency ratings as well as what their natural frequencies may be.
The best approach for approaching this is listening and making slight modifications with the crossover’s gain controls until your system has an all-encompassing sound with punchy mids and clear highs.
Adjusting your bass guitar amp speaker crossover to suit a certain genre or personal taste is easy: 100Hz will deliver the kind of boom many rap fans are after; 80Hz tightens bass tone while improving front soundstaging.
The crossover features a variable band-pass setting to help eliminate feedback and distortion by filtering out unwanted frequencies in the midrange. This feature can be particularly beneficial in open vehicles such as wagons and SUV’s where lower frequencies may resonate through seat materials and compromise sound integrity.
To adjust bandpass settings, run patch cables from your receiver’s output terminals to the inputs on a variable crossover, followed by additional cable runs connecting its outputs – high outputs for tweeters/mids, while low outputs connect directly with bass speakers – directly into amplifiers that power your speakers’ amplifiers and amplifiers that power their tweeters/mids/woofers amplifiers.
Care should be taken when setting bandpass settings. Going too far will result in the highs becoming indistinct and lows sounding fatter; if this occurs, reduce gains by several clicks before listening for quality before repeating this process until satisfied.