The Basics of Selecting the Right Loudspeaker
Investing in high-quality professional loudspeakers and configuring them correctly in your venue will make mixing live sound easier and will provide a more enjoyable listening experience for both the performers and the audience. Live sound reproduction requires reliable performance and consistent coverage throughout the listening area, so professional loudspeakers are worth the investment. PreSonus® has put together this brief tutorial to help you pick out the best loudspeakers for your budget so that you get the best results.
Selecting the Correct Speaker
The first major consideration when selecting loudspeakers is your live sound environment. If you are installing loudspeakers for permanent use, your first step should be contacting a licensed sound contractor to evaluate your venue. A sound contractor has the knowledge and experience to determine the best solution for your application and your budget and can properly install and service your loudspeaker system.
Once you’ve evaluated your listening environment, listen to some speakers at your local music store. Be sure to take along a comprehensive assortment of well-mixed recordings with which you’re familiar and that reflect the type of music your loudspeakers will be reproducing. Keep in mind that digitally compressed files can sound brittle and harsh on loudspeakers, so don’t use MP3s.
The listening environment at a music retailer is not always optimal. If you think this might be the case, it may be a good idea to rent two or three potential candidates and take them for a test drive before purchasing your final selection. If you are configuring a permanent installation, a contractor can also arrange for a listening demonstration in your environment so that you can get a preview of your sound system before you purchase it.
The most important elements to listen for are:
- Bass response. Is it tight and controlled or boomy and poorly defined? A well-designed loudspeaker will deliver punchy, musical bass. If you can’t hear the note, just “feel” it, it’s probably best to move on to another option.
- Mid-frequency response. A well-designed loudspeaker will have an even midrange. This is important because vocals and most instruments “live” in the midrange. Make sure you can hear the attack of the snare drum and that the vocals and guitars are vibrant and present.
- High-frequency response. Are the cymbals and hi-hats crisp and shimmery? Or do they have a brittle edge? A well-designed loudspeaker will provide crisp high end without sounding harsh or strident.
- Linear frequency response. Do some instruments seem more exaggerated than others? Does the vocal seem to vanish as it navigates the notes in the melody? A well-designed loudspeaker will provide a smooth, linear frequency curve throughout its reproduction range. A loudspeaker like this will translate well from room to room.
- Vocal presence. Are the vocals up front and present? Or do they get buried in the mix? Vocal presence is a good indication of how easy it will be to quickly dial in a good mix.
- Speech intelligibility. Can you clearly hear and understand what someone says when speaking into a microphone through the system? Are both male and female voices intelligible? Intelligibility is also a good indication of how coherently transients will translate in a mix.
- Off-axis performance. Most professional loudspeakers will sound good within their coverage area, so it’s important to move around the room. Well-designed loudspeakers will sound consistent throughout their coverage area, even at, or outside of, the edges the listening field.
Finally, and most important, your personal taste will always be the final determining factor. There is no right or wrong answer. Choose the loudspeakers that work best for your room and your target audience’s expectation. Go with what your ears tell you.
Speaker Basics
You should familiarize yourself with a few terms before going loudspeaker shopping. Understanding the terms pro audio manufacturers use to describe how their loudspeakers perform in real-world environments will help you to narrow down which type of speaker will best suit your needs.
Driver. Also called a transducer, the driver is the part of the speaker that produces sound waves. The better the quality of the driver, the better it will reproduce sound waves and take the wear and tear of a live sound environment. Two-way loudspeakers have two drivers: one high-frequency and one low-frequency. Three-way loudspeakers have three: one high-frequency, one mid-frequency, and one low-frequency.
Cone Driver. Named for their diaphragm shape, most loudspeaker cone drivers are paper or composite with two surrounding components and are typically responsible for low-frequency reproduction. The inner surround is called the “spider,” and it attaches near the bottom of the cone to better control the voice coil’s movement within the gap. The outer surround attaches the cone to its frame, also known as the “basket,” suspending it so that the diaphragm can move back and forth freely. Loudspeakers are typically described by their cone driver’s diameter (for instance, the PreSonus AIR10 10-inch, 2-way loudspeaker has a 10-inch cone driver).
Voice Coil. A voice coil is the coil of wire that is attached to the base of a cone driver. It provides the movement to the cone by reacting to the magnetic field as electrical current passes through it. In other words, it is the motor that moves the cone driver. In general, the larger the voice coil, the stronger the movement will be, resulting in a tighter bass response.
Compression Driver. As its name describes, a compression driver moves sound into a small chamber, compressing it before it exits to an outer chamber, usually an acoustic horn. Just like cone drivers, compression drivers are described by their diameter. A larger compression driver will have a higher output.
Acoustic Horn. The acoustic horn is used to increase the overall efficiency of the driver. Most commonly used for high-frequency reproduction, the usual configuration consists of a compression driver that produces sound using a small metal diaphragm that is vibrated by an electromagnet. The compression driver assembly is then attached to the base of the horn’s throat. Well-designed horns, like the Pivot X110 horn used in the PreSonus ULT-series loudspeakers, can better control the high-frequency response throughout their coverage angle for improved off-axis response.
Acoustic Port. Also known as the “bass reflex port,” an acoustic port redirects the inward pressure produced by the outward movement of the speakers. The backward motion of the diaphragm pushes sound waves out of the port and boosts the overall sound level. Ported speaker designs are much more efficient because the power moving the driver produces two sound waves instead of one.
Coaxial Speakers. A coaxial speaker, like the one used in StudioLive® AI-series loudspeakers, places the high-frequency driver in the center of, and on the same axis as, the low-frequency driver, which is similar to the way the human ear works. Coaxial designs offer a symmetrical response both horizontally and vertically to create a wider “sweet spot” and consistent coverage throughout the room.
Crossover. The crossover separates the frequencies coming into a speaker and distributes them appropriately to the low- and high-frequency drivers. This helps the speaker run more efficiently and reproduce the frequency spectrum more reliably.
Frequency Response. This is the frequency range that a loudspeaker can reliably reproduce. Operating range limit measurements are not standardized and can be specified at -3 dB, -6 dB, or even -10 dB. As a general rule of thumb, a -3 dB measurement will be the most accurate representation of how a speaker will actually perform. A -10 dB measurement typically exaggerates a loudspeaker’s low-end capability.
Max SPL. Maximum SPL is measured at one meter using continuous broadband pink noise. This number does not mean that the speaker is reproducing every frequency at that range, so it’s important to evaluate potential loudspeakers with your ears, not just the cut sheet.
Nominal Coverage. Also called “coverage angle,” “nominal dispersion,” and “dispersion pattern,” this measurement will show you how wide or narrow a loudspeaker’s horizontal and vertical coverage patterns will be. Many point-source powered loudspeakers, like the PreSonus StudioLive AI-series and AIR-series, offer a 90˚(horizontal) x 60˚(vertical) dispersion pattern. A wider horizontal coverage angle, like the 110˚ angle available in the PreSonus ULT-series, will cover a broader area than the 90˚ angle available in other PreSonus loudspeaker series and most other loudspeakers in the same price class.
Throw. Many aspects of loudspeaker design, as well as the room itself, will determine how far a loudspeaker can carry or “throw” audio throughout a room. One of the most critical is the vertical coverage angle. For example, the wider vertical coverage angle provided by a 75˚ axis-symmetric dispersion has a shorter throw because the sound waves will encounter reflective surfaces, like the floor and ceiling, fairly close to the loudspeaker. The resulting reflections will blur the audio signal, inhibiting the loudspeaker from being able to carry clean, clear audio to the back of the room.
By contrast, a narrower vertical angle, like the 60˚ angle available in PreSonus StudioLive AI-series and AIR-series loudspeakers, will encounter those same reflective surfaces later, and farther, from the loudspeaker; and the 50˚ angle provided by the ULT-series will meet those surfaces later still, which is why we call them “Ultra-Long Throw” loudspeakers.
Amplification Basics
Active vs. Passive. Active loudspeakers have onboard power amplification that has been designed to optimally power the drivers. This takes the guesswork out of choosing the right speaker/amp combination. Passive loudspeakers do not have an onboard amp and require an external power amplifier. When matching an external amplifier to a passive speaker, it is critical to know both the impedance load and continuous power that your passive speaker is designed to receive. Mismatching either of these will cause damage to your speaker.
Biamplification. A biamped loudspeaker has two amplifiers: one dedicated to powering the high-frequency driver and the other dedicated to powering the low-frequency driver. By separating the frequencies before they hit the amplifiers, a biamped system removes one of the major sources of intermodulation distortion. The resulting sound is more open and clear. Two other variants of this configuration are triamped and quadamped designs, like those in the StudioLive AI-series. These configurations provide three and four amplifiers respectively to provide independent power to each driver in the system.
RMS Power. The RMS power rating is the amount of continuous power that an amplifier can output or a passive speaker can handle. As a general rule of thumb, this rating is roughly half of the peak power rating.
Peak Power. This is the maximum power that an amplifier can deliver or a passive speaker can momentarily handle without being damaged. It’s important to mention that pushing a speaker to its peak power load for longer than a few seconds can damage a speaker.
Class A Amplification. This amplifier type uses output transistors to conduct the full waveform. Because Class A amplifiers can provide very low distortion, they are popular in audiophile applications; however, this amplifier type is too inefficient for pro audio applications.
Class B Amplification. This design conducts half of the waveform in separate sets of positive and negative signals. This efficient design suffers from crossover distortion where the positive and negative devices meet, especially at low signal levels.
Class AB Amplification. As its name indicates, this is a hybrid between Class A and Class B designs. At low levels, it functions just like a Class A, keeping the crossover distortion low. At higher levels, it changes to work as a Class B. The advantages of this design can best be heard in high-frequency reproduction. PreSonus AIR-series loudspeakers use a Class AB amplifier to power the high-frequency driver for this reason. The result is a much more natural sounding upper end without the brittleness or harshness some affordable Class D designs can introduce.
Class D Amplification. This amplifier controls the output using pulse modulation of the input signal. The pulses control the voltage and current flow at the output. Class D amplifiers are very efficient and lightweight, making them popular for mobile loudspeakers. This is the most common amplifier type used in active pro audio loudspeaker designs.
Loudspeaker Types
Point-Source. A point-source loudspeaker is what most people think of when discussing loudspeakers. Available in two- and three-way designs, point-source loudspeakers are fairly easy to set up because they provide very good coherence as compared to multi-speaker designs. While ideal for mobile applications, small venues, and floor monitoring, point-source speakers may not be capable of achieving the sound pressure level necessary for larger venues.
Distributed. A distributed loudspeaker system uses multiple smaller format speakers spread throughout the coverage area. These systems often supplement the main front-of-house system to provide coverage for areas that may be outside the main listening area. A distributed system can be challenging to configure because it requires carefully designed delay settings, level matching, and tuning. Some loudspeakers, like the PreSonus StudioLive AI-series and active WorxAudio-series systems, are equipped with powerful speaker processing that simplifies creating a distributed system.
Cluster. As its name indicates, a cluster system consists of a group of point-source loudspeakers being used in conjunction with one another. This is a flexible option to create a custom coverage pattern and to provide a higher SPL output. However, like a distributed loudspeaker system, a loudspeaker cluster requires a skilled system designer to achieve the desired result.
Line Array. A line array is one of the most popular loudspeaker systems for installations and large touring productions. It consists of multiple loudspeakers that work together to cover the frequency range. Many modern line arrays provide the ability to “steer” audio for precise coverage over a large listening area while keeping most of the sound off of walls and other reflective surfaces. Some line arrays employ multiple enclosures; others, like the PreSonus WorxAudio X3, provide the benefits of a multi-enclosure system in a single box.
Constant Directivity. Combining the uniform frequency response of a point source design with the uniform SPL coverage of a line array, constant directivity loudspeakers like the PreSonus CDL12 provide a “best of both worlds” approach for mid-sized mobile and large installed systems by supporting both single speaker and vertical array configurations.
Subwoofers. A subwoofer is designed to reproduce low- and sub-low-frequency content only. When carefully tuned to the full-range system, a subwoofer will naturally extend the low end to create a fuller listening experience. A properly calibrated three- or four-way system can improve your listening environment by offloading much of the bass-frequency reproduction to the sub, letting the low-frequency component of the full-range system focus on the low mids.
