bass amp faq : bass cabinet guide
The bass cabinet is the box with the speaker. It’s basically the last link in the chain you control before the sound hits your ears, microphones, and the audience. When you look at a cabinet you might think there’s little to it. It’s just a plywood cube with a speaker and some wires inside! That’s true. The materials used to make a bass cabinet do not seem that impressive. But, there is a lot that goes into designing the cabinet ensuring everything works together and creates a good reproduction of your bass tone. The design is a big part of what you pay for in a bass cabinet.
The maddening part of shopping for any bass gear is making sense of what is hype and marketing jargon and what is important. Plus, every manufacturer uses slightly different terminology. I’ll try to make sense of it for you as it relates to bass cabinets.
The Bass Cabinet Enclosure
The enclosure is the housing, or box, of the cabinet. The bass cabinet enclosure will experience a lot of vibration from the bass you pump through it. A solidly constructed enclosure is essential for a bass cabinet.
Most enclosures are made of plywood. Good quality plywood is important. Some manufacturers may specify the type of plywood birch, mahogany, etc. The type of plywood has a limited effect on the overall sound of the cabinet. I'm sure some would argue otherwise, but I wouldn’t get too worried about what type of plywood is used. You will sometimes see the term void-free plywood. That just means the plywood is solid though and through.
Since most cabinets are heavy and you’ll be moving them a lot, make sure they have good, sturdy handles. For really heavy ones, look for wheels (casters).
The corners should be tough and protected, too. The corners will experience a lot of abuse. You may see terms like stackable or interlocking corners. This helps you easily stack two cabinets together.
Sealed and Ported Bass Cabinets
Some cabinets are sealed meaning no air leaks in or out of the enclosure. Most bass cabinets are ported, or vented, meaning the cabinet has an opening where air can travel in and out.
Sound is essentially moving air. As the speaker pushes air in front of it, the rear side of the speaker (on the inside of the enclosure) is sucking air into the enclosure and vice versa. Having the port helps the speaker work more efficiently which means it requires less amp power to drive it.
Ports are tuned by the manufacturer to make sure they emphasize particular frequencies usually low ones. Ported cabinets, as a result, often get a better low-end response.
In a sealed cabinet the speaker cannot suck any air in. That makes the speaker work harder. Sealed cabinets need more power to achieve the same results. Some bassists like the sound of a sealed cabinet claiming they have a punchier sound. You will have to decide with your own ears. Most of your bass cabinet options will be ported ones.
Bass Amp Speakers
Speakers, sometimes called drivers or woofers, are constructed of a voice coil, magnet and a cone. The cone is the outer part of the speaker which, when it rapidly moves in and out, moves the air to create sound waves. Cones are usually made of paper and other times plastic or metal.
The voice coil and magnet work together to cause the cone to move in and out. The voice coil is an electromagnet. It interacts with the plain magnet pushing and pulling the cone as the polarity of the voice coil rapidly shifts back and forth.
Speakers come in different sizes measured in inches. You may see 8-inch to 20-inch speakers used in bass cabinets. Bigger is not necessarily better. The quality of the speaker is most important. A great 10-inch speaker might give off more bass than a poor 18-inch speaker.
Generally big speakers give you more "boom" while smaller speakers give you more clarity and definition. Many bassists like to use a combination of speaker sizes in their rig to cover the entire spectrum. To decide what speaker configuration to buy, it’s really important to make comparisons with your own ears.
Manufacturers will often name the brand of speaker used in the cabinet like "four 10-inch Celestion speakers". Other common brand names might be Eminence or Black Widow.
Horns are speakers which emphasize the higher frequencies in your bass sound. They can add that bright, crisp sound in with your low-end. Many cabinets come with horns. They are sometimes called a tweeter or a high-frequency driver. You may see an attenuator switch for the horn. This allows you to adjust the output of the horn or turn it off.
When you have speakers and a horn, you need a crossover. A crossover splits the bass signal into the high and low frequencies. The highs are sent to the horn and the lows to the speaker(s). Some crossovers are fixed to split the signal at a designated frequency. Other crossovers let you adjust the crossover frequency. The crossover will be built into most cabinets containing both speakers and a horn.
Jacks and Connectors
Many cabs use 1/4" jacks into which you plug the output of your bass amp head. Though these jacks may look the same as what you plug into your bass, you need special speaker cables to connect the head to the cabinet. Don’t use an instrument cable to connect speakers to amps! You can cause some real damage.
Some cabs use Neutrik Speakon jacks. These are a special brand of jack which accept special Speakon connectors which are locking. Other cabs may use banana plugs like many home stereo systems.
Be sure to get the right cables with the right connections to hook up your head and cabinet. If you don’t know, ask the salesperson.
Bass Cabinet Specifications
You will come across a number of technical specifications as you shop for bass cabinets. These can be quite confusing at first. Here are some simple explanations…
Frequency response refers to the range of frequencies the cabinet can produce. Frequencies are measured in Hertz (cycles per second). You might see a range from a low 30Hz to a high 20kHz (20,000Hz). Human hearing typically ranges from 20Hz to 20,000Hz.
The low E of a 4-string bass rings around 41Hz. The low B of a 5-string bass hits 30Hz. To really hear your low notes well-defined, you might look for a frequency response down to 30 or 40Hz.
Sensitivity is a measure of output. It is often marked as SPL (sound pressure level). You may see “Sensitivity: 104dB SPL” or “SPL: 102dB 1W@1m” in specs. Sensitivity is the volume (measured in Decibels) put out when a 1kHz test tone is played at 1 watt of power. It is measured from 1 meter away. That is what 1W@1m means.
Not much happens in the 1kHz frequency range for us bass players. Without more information on the lower frequencies, sensitivity is a relatively useless spec to worry about. It may only give you a slight impression of how loud the cabinet is.
Power handling is how much power (watts) the cabinet can safely take without the speaker blowing or being damaged. You want to make sure your amp head is not sending too much juice to the cabinet. Can your amp's watts exceed the rating of the speaker? (For example, a 500W head into a 400W speaker.) Yes, but if you crank it too much you risk damaging the speakers. On the other hand, not having enough power in some cases can damage the cabinet, too. If you are driving the head too much because it is under-powered, you will cause the amp to clip or distort. When it is clipping, the amp might be sending more watts than it is rated. Sending that to your cabinet can damage the speakers.
Manufacturers love to put big numbers in specs next to small numbers such as “200W RMS/400W peak power handling.” You should not worry much about wattage numbers which say peak. That only means a quick burst of power. That number will always be much higher than the real power handling of the cab. Instead you want to know how many watts the cabinet can take constantly. You will see numbers which say “450W Continuous” or “200W RMS”. If there is only one wattage number listed, that’s usually what you want to know. Most of the time it will be marked as RMS (Root Mean Square) or True RMS. With multiple wattage numbers in the specs you can guess the true power handling is the lowest number of watts listed.
When power flows to the cabinet, the cabinet resists some of the power. Impedance is a measure of resistance and is expressed in ohms (Ω). Bass cabinets usually come in 4- or 8-ohm impedances. Choosing the right impedance to match your amp confuses many people and I’ll explain it in the how to hook up amps and cabs article.
Important Considerations Before Buying a Bass Cabinet
Can you afford it?
Gear can be pricey. If you plan ahead with what you are going to buy, you can buy your ultimate bass rig piece-by-piece or gradually upgrade. That can help you ease in financially.
Can you carry it by yourself?
Don’t expect the drummer to help you to carry your gear. Even if you get an amp with wheels you may need to carry it up stairs, over curbs, or while running away from an angry soundman.
Can you transport it?
Cabinets can be big and difficult to get into cars. Can you maneuver the cab into your vehicle? Will it fit in your car’s trunk or front seat? Will there be enough room for other passengers in your car, too?
Good luck in shopping for your dream bass cabinet!