Kef LS50 - Reviews, Prices, Specs and Alternatives

The primary components of a bookshelf speaker are “drivers,” which are the cones that actually create the sound. These cones come in three types: tweeters, midranges (sometimes called mids), and woofers. Tweeters produce high frequency sounds, while woofers produce low frequency sounds, i.e. bass. Adding a midrange driver allows for a more robust sound, since the audio is split among more drivers and each driver can focus on key frequencies.

To define the number of drivers, a speaker is considered two-way, three-way or four-way. The majority of bookshelf speakers are two-way speakers, meaning they contain two drivers (tweeter and woofer). Some high-end speakers are three-way, which adds a midrange driver to the mix for a total of three drivers (tweeter, midrange, woofer). You’ll be hard pressed to find a four-way bookshelf speaker—this is usually reserved for floor speakers—but as technology advances and components become smaller, you may start to see four-way bookshelf speakers popping up in the premium priced category. Four-way speakers include four drivers, typically a super tweeter, tweeter, midrange, and woofer.

While the number of drivers is important to the makeup of the speaker, more drivers does not exclusively mean higher sound quality. In most cases, having a third driver does create a fuller, broader range of sound (and will cost you a bit more money), but the difference between a three-way and four-way speaker is marginal. It’s important to look at the totality of the audio metrics to determine speaker quality, not just the number of drivers.

The cabinet refers to the portion that surrounds and holds all of the speaker elements together - the speaker box, if you will. The most common material is wood, but you’ll also find plastic, fiberboard, metal and combinations of materials making up the body of the cabinet.

Cabinet build and makeup is important because the amount of space and air behind the speaker determines the movement of the woofer. The more space (i.e., the larger the cabinet), the more powerful the bass. Also, strong, rigid materials are best, otherwise the sound becomes muffled and deformed. The key to a solid cabinet build is that it’s airtight and sealed. If air can escape, sound quality will suffer immensely.

The type of enclosure, or cabinet, plays a key role in determining the focus of your sound. Do you prefer accurate bass or loud bass? There are two main types: acoustic suspension and bass reflex.

Acoustic Suspension: Acoustic suspension uses a sealed enclosure to reduce bass distortion and provide more controlled bass response. This is the more accurate of the two cabinet types. Because of this, an acoustic suspension enclosure requires more power from the amplifier to play at the same volume as a bass reflex enclosure.

Bass Reflex: Bass reflex is a trade off of the benefits/drawbacks of acoustic suspension. Bass reflex enclosures are designed to increase bass response for louder, “boomier” bass with less power needed to play at higher volumes. However, you sacrifice bass accuracy for the bigger booms. Still, for true bass heads, a bass reflex speaker is the way to go.

Measured in decibels, or dB, sensitivity measures a speaker’s ability to convert power to volume. Lower sensitivity speakers require more power from the amplifier to achieve higher volumes. Higher sensitivity requires less power for high volumes. Generally speaking, higher sensitivity speakers are louder, and small increases in decibels result in big reductions in wattage needed to reach a certain volume. A low sensitivity is any rating up to 88dB. High sensitivity goes up to 100dB or higher.

Given as a range in Hertz (Hz), the frequency response is a measurement of the range of sound a speaker can produce. For reference, the human ear can hear a frequency range of 20 Hz to 20,000 Hz (shortened to 20kHz). A good frequency response starts at 50Hz or lower and covers as much of that range as possible. Also, take note of any ranges that include a +/- dB rating at the end. Since there’s no industry standard for frequency response measurement, speakers with this extra piece of information are typically more accurate than those that just provide a general frequency response range.

When sound is played through a speaker, an electromagnet is activated using the power from the amplifier to bring the driver forward, and another magnet pulls the driver back. This causes the driver to move forward and backward rapidly to create sound. Because of this process, speakers create an electromagnetic field that can cause serious problems for other devices. Strong magnetic fields can distort screens and displays on TVs and monitors when placed in close proximity to these devices, and can sometimes cause data wiping when close to hard drives and disks. The key here is proximity. If you plan to place your bookshelf speakers next to any of these devices, you’ll definitely want one with build in magnetic shielding surrounding the drivers to contain the magnetic field and protect your nearby devices.

Power handling, or peak power, is the highest wattage a speaker can accept from an amplifier before it burns out or becomes damaged. This number is given in watts. It’s recorded by measuring how loud the speaker is at 1 watt. It’s crucial  to match the peak power of your speaker with the highest output of your amplifier to ensure that you do not supply too much power to your speaker, or it can become damaged.

What you may not know about bookshelf speakers is that they don’t always work straight out of the box. To power the speakers, you often need a receiver and an amplifier. Amplifiers power the signal that is sent to your speakers to create sound. Without an amplifier, there is no sound. In some cases, you’ll have to buy a separate amplifier for your bookshelf speakers, adding more cost to your purchase. Purchasing an amplifier can also be confusing, since you need to match the capabilities of your speakers with the amplifier—if you don’t, you could seriously damage the speakers, throwing that money down the drain.

Because of this inconvenience, powered speakers are becoming more and more popular. Powered speakers have built-in amplifiers in the speaker cabinet, so there is no need to purchase an additional amplifier. These speakers are operational out of the box and connect directly to your AV receiver. The catch? They typically come at a premium price and may sacrifice other features for the powered ability.

Impedance is a key electrical measurement, provided in ohms. This number describes the electrical resistance provided by the speaker to the power signal sent by your amplifier. A common analogy used for impedance is the flow of water through a pipe. The audio signal is the water flowing through the speaker, which is the pipe. The bigger the pipe, the more water can flow through.

Impedance is equivalent to the size of the pipe. The lower the impedance, the bigger the “pipe,” and the more easily water (the audio signal) can flow through it. This number is crucially important to your speaker setup. Without it, power would flow freely through the speaker until it burned out. Why’s that? First, all speakers in your setup should have the same impedance rating. The most common rating is 8 ohms, which will work with most amplifiers, or amps. Just make sure that any other speakers you add to your setup have the same impedance.

Second, the impedance must be compatible with your amp. Lower impedance, such as 6, 4 or 2 ohms, needs a more powerful amp to reach higher volumes without damaging your equipment. There really isn’t any clear benefit to choosing a lower impedance speaker. It’s just critical to match this number with the other elements of your speaker set up (amplifier, other speakers, etc.).

More and more, musicians and streaming services are offering high-resolution audio playback for music files. Like a TV, your speaker has to be high-res capable to play these high-res files. True audiophiles and music enthusiasts will definitely need a speaker with high-resolution audio playback to truly enjoy their music experience. Keep in mind that buying this feature only matters if you actively seek out and listen to high-res audio files (or plan to in the future).

Tweeters produce the highest frequencies in sound, typically anything above 2,000 Hz. Usually located at the top of the speaker, tweeters come in different shapes (detailed below) and sizes. Generally speaking, the size of the tweeter is not as important as the shape. But, for some guidance, consider that a larger tweeter (measured by diameter in inches or millimeters) willFor the true audiophile, choosing the right tweeter shape is key to getting the best out of your speaker. Different tweeter styles distribute sound more effectively throughout the room, and because higher frequencies are more directional, better distribution usually means better sound quality. The major types include cone, dome, horn, and planar-magnetic.

Cone: Found most commonly, cone tweeters are the easiest to produce and, therefore, the lowest quality. Sound reproduction isn’t nearly as good with cone tweeters as it is with some of the other designs, especially because this style is usually made with inferior materials.

Dome: The dome shape is preferred over cones because it does a much better job of projecting audio and dispersing sound across a larger area. Dome tweeters look how you might imagine… like domes sunken into face or plate of the speaker.

Horn: Horn tweeters behave like a megaphone. The sounds coming through the tweeter are amplified by the horn for greater sound dispersion with more clarity of sound and less distortion. These are not nearly as common as the first two shapes, but you may come across them in some models.

Planar-Magnetic: Primarily reserved for the high-performance speakers, planar-magnetic or planar ribbon tweeters are made of a thin material between two magnetic poles. The material vibrates as sound passes through for transparent, light sound. Planar-magnetic tweeters are made of special materials with high sensitivity, and are more cost-effective to manufacture than regular ribbon tweeters. likely be louder and able to disperse sound over a larger area.

Woofers are built with a variety of materials, such as paper, plastic, polypropylene, Kevlar, or metal. Some are even made with more unique materials like wood. They key to quality in a woofer material is how quickly it reacts to sound, both in its stiffness while vibrating and its ability to stop abruptly when the sound stops (without any reverberations causing additional sound). The weight of the material is also an important factor. Typically, you want a material that is  rigid, lightweight, and doesn’t ring once the sound stops. The common materials used for woofers and their advantages/disadvantages are described below.

Polypropylene: This is the most common woofer material because it’s inexpensive and easy to manufacture. It is a type of plastic that reproduces decent sound and prevents ringing, but is heavier than some alternatives, such as metal and Kevlar.
 
Paper: Another common material used in woofers is paper. Paper has similar advantages to polypropylene. It’s not as stiff as metal, and it’s heavier, but it’s particularly adept at preventing sound reverberations. One downside to paper is that is reacts to humidity and temperature and can warp, which will affect the sound quality over time. Still, it’s not a terrible choice of material for your woofer.
 
Kevlar: You’ve probably heard Kevlar more commonly used in bulletproof vests… but believe it or not, this material is great for woofer cones. Kevlar is a tough, tightly woven fiber, which makes them stiff—a huge plus for sound reproduction in speakers. And kevlar woofers usually respond well to the stopping of sound, which prevents ringing. This makes kevlar one of the better choices for woofer material.
 
Metal: The benefit of a metal woofer is that it is clearly stiff and lightweight. However, a huge downside is that it usually has ringing problems. Metal is actually a better material for high frequency drivers, or tweeters, rather than a woofer.
 
Finally, you may also see rubber pop up when assessing woofers. Rubber is what makes up the surround, which borders the woofer and prevents unnecessary vibration. Having a rubber surround is a positive feature in any speaker.

If the bookshelf speaker is Wi-Fi or Bluetooth-enabled (or both), you’ll likely be able to control the output through your smartphone or other device. Sometimes, this capability comes with the caveat that you must download a certain mobile application to use your speakers. 

For example, Yamaha’s MusicCast app lets you control your speakers from your device. It syncs with popular online music services, such as Spotify, Pandora, and SiriusXM, allowing you to stream audio directly to your speakers. The app also connects you to other Yamaha speakers in your home and gives you the option to play different audio on different speakers or play the same song through different rooms. This is just one industry example of this type of app, but shows what to look out for if you hope to play audio on your speakers directly from your phone (bypassing the receiver or TV).

Speakers with Wi-Fi connectivity connect directly to your home Wi-Fi network to stream audio from your devices—smartphone, tablet, laptop, etc. This may require an app from the brand, such as Yamaha’s MusicCast app, to connect to the speakers and play audio. If this is the case, it’s important to verify that the brand’s app works with your favorite online music services (e.g., Spotify, Pandora, etc.). To bypass the app, choose a speaker that is also Bluetooth-enabled.

Speakers with built-in Bluetooth allow you to stream audio content directly from device (e.g., smartphone, tablet, laptop) on the speakers. This feature behaves just like any other Bluetooth-enabled device, such as portable Bluetooth speakers. It’s important to remember that connecting to your speaker over Bluetooth will slightly reduce the quality of the sound, as signals travel much more easily through wires.

Not to be confused with Wi-Fi-enabled speakers, wireless speaker set ups do not require a speaker wire or direct lines to other speakers and the AV receiver. Typically, these speakers require a wireless hub that acts as a transmitter for the sound coming from your device, TV or otherwise. Each speaker has its own wireless receiver that connects with the transmitter to produce sound. Note that these speakers are not completely wireless. They still need to be plugged into AC outlets for power. Still, it can be challenging to hide long runs of speaker wire all over the room, depending on the number and placement of your speakers. On the other hand, wireless speakers are generally more expensive. And some users complain that sound quality is sacrificed by wireless transmission (rather than through a dedicated speaker wire). You’ll have to weigh the benefits and drawbacks to determine whether or not this feature is important to you.

Speaker wire is the connection used between speakers, amplifiers and receivers. This is a special type of wire that makes an electrical connection and transmits sound signals. You will only use this type of wire when setting up your bookshelf speakers and the associated sound system. If the box for your speakers does not come with a speaker wire, you will have to purchase it separately. Consider this additional cost when assessing what bookshelf speakers you want.

Bookshelf speakers commonly come with speaker wire inputs/outputs to connect your speaker to an AV receiver, which transmits the sound from your TV. In some cases, speakers may come with additional inputs to connect different devices to your speaker. Some examples include: an Ethernet port to connect Wi-Fi-enabled speakers directly to your home network; an auxiliary jack for connecting devices via aux cable; a USB input for connecting a computer or other device; and/or an optical digital input. You’ll typically see more connections in bookshelf speakers that do not require a receiver, so you have plenty of options.. Speakers that do not require a receiver are uncommon.

For the environmentally conscious, choosing an “ENERGY STAR Certified” speaker may be important to you. Technology devices with this label are required to meet certain industry standards as it relates to energy use and environmental safety.