Sound Alignment Systems Lg-120

Best Car Stereo Systems 2019 - Radios, Head Units & In-Dash Receivers

1. Sound Alignment Systems Lg-120 House
2. Sound Alignment Systems Lg-120 Service

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After over a week of research and 14 hours of in-depth testing, the Pioneer AVH-501EX emerged as our pick for the best car audio system. This stereo produces high-fidelity audio and includes a time alignment tool, full lossless compatibility and 13 EQ bands. The AVH-501EX’s interface is very easy to navigate, and its display is the best we've seen. And with a DVD player and video ports for backup and dash cameras, this stereo is far more than just an audio system.

Pioneer AVH-501EX

The Pioneer AVH-501EX is our pick for the best car audio system because it received the highest grade in our audio quality tests and is more stylish and versatile than other systems.

JVC KW-R935BTS

The JVC KW-R935BTS is our value pick because it has high-end audio quality and an exceptionally intuitive and stylish display that’s comparable to those on stereos that cost nearly twice as much.

Pioneer DEH-80PRS

The Pioneer DEH-80PRS is the best single-din stereo we reviewed because it has great audio quality and is easy to use. Plus, its three 5-volt pre-outs make it ideal for expansion.

Sound Alignment Systems Lg-120 House

Best Overall

Pioneer AVH-501EX

The Pioneer AVH-501EX has average power for a car stereo, but its audio quality is superb. It received the highest audio quality grades in our tests, thanks in part to its EQ band filters and time alignment tools.

In addition, it's one of the few stereos in this price range that is compatible with all types of audio formats, even less common lossless formats like FLAC. This is why it's our pick for the best car stereo system.
The AVH-501EX’s 13 EQ bands come with presets that enhance the audio in specific music genres, and you can adjust each band with the stereo’s touchscreen. Most stereos have preset filters, but not many let you customize the EQ bands. You use the touchscreen to move the frequency bands up or down, which emphasizes or deemphasizes specific frequency ranges. Basically, you have total control over how your music sounds in your car.
This is the only double-din stereo we reviewed with a touchscreen. In addition to letting you customize the EQ bands, the screen makes it exceptionally easy to navigate the stereo’s myriad features.
The stereo’s time alignment feature helps you further improve how your audio system sounds. You place a microphone (included) where you want the best sound, such as the driver's seat or the middle console. The stereo then adjusts the timing of the audio signals so the frequencies from each speaker reach that point at the same time. When you combine the stereo’s EQ controls with its time alignment tool, you get high quality audio customized to your car's acoustic landscape.

Best Value

JVC KW-R935BTS

The JVC KW-R935BTS is your best option if you’re looking for an affordable double-din stereo with high-end audio quality and a stylish, intuitive display. This stereo has 13 EQ bands, a timing alignment tool and full lossless format compatibility.

As a result, it received an A grade for overall audio quality in our tests, which puts it on par with much more expensive systems.
Its display received an A for ease of use and an A- for quality, so it's both easy to use and stylish. The important buttons (pause/play, skip, repeat, volume and phone controls) are all big, clearly labeled and brightly illuminated – this makes them easy to find and use so you aren’t distracted with your music controls while you drive. In addition, the front of the display has ports for USB and AUX inputs, which makes the stereo easy to integrate with your smartphone or portable music player.
The power output is 50 peak watts per channel, which is average. Since the stereo has four channels, it’s total power output is 200 watts. There are more powerful stereos out there, but 200 watts is enough to rattle your windows. The KW-R935BTS reached volumes over 100 dB in our tests, which is more than loud enough to permanently damage your hearing if you’re exposed to it for long. In other words, it may be average, but average is enough.
If you have an external amplifier, it's worth noting that the JVC KW-R935BTS has 4-volt RCA outputs, which is excellent. A high voltage means the audio signal has less noise.

Best Single-Din Car Stereo

Pioneer DEH-80PRS

The Pioneer DEH-80PRS is one of the newest stereos to hit the market. Its single-din design means it fits almost every type of car installation, but it's the 5-volt pre-outs that set the stereo apart.

This stereo is designed for car audio enthusiasts who want to take the next step and add an external amplifier to their system. With this high voltage rating, the DEH-80PRS sends a cleaner audio signal to your amplifier than other stereos do.
In our tests, the DEH-80PRS received an A grade for audio quality, which makes it one of the best sounding stereos available. This is to be expected though, since it’s also one of the most expensive stereos we reviewed. It features 16 EQ bands and a time alignment tool, so you can optimize it to your car's unique acoustic landscape.
The one downside of this stereo's audio performance is it isn’t FLAC-compatible. However, this is a minor issue unless you're an audiophile and prefer the lossless quality of the FLAC format.
The DEH-80PRS’s display received an A- for ease of use and quality. The controls are very easy to navigate, so they aren’t a distraction while you drive. Its display also has some cool animations, though it didn't receive the best grades overall. In addition, there isn't a USB port on the front, so you have to install a cord from the rear USB port to stream audio from a USB source or to charge your phone.

Best Ease of Use

Alpine CDE W365BT

Car stereo displays are often designed for style over function with over 250,000 color combinations and video displays with animations, videos and album art. The Alpine CDE-W265BT shirks this pattern in favor of function. It was the only car stereo to receive an A+ for ease-of-use for its interface. I tested this by performing a series of functions on each stereo without looking at the interface. If a stereo is too complicated to use without taking your eyes off the road, it's not safe. The W265BT was the only stereo where I was able to complete every function without looking at the interface. The design of the buttons has a simple logic, making it the easiest interface to master.
Unfortunately, this means the display is boring in comparison to other car stereos. There are ways to enhance the style, like adjusting the colors, but you only have 30 colors to choose from. In addition, the digital display has the font of a digital clock, making it difficult to read. That said, the audio performance was excellent. So, if you don't mind a boring display, the Alpine CDE-W265BT is a good option.

Sound Alignment Systems Lg-120 Service

Most Affordable

Boss Audio BV7260B

At $50, the Boss Audio BV7260B is the most affordable car stereo I reviewed, but it doesn't look like a cheap stereo. The display is a 3.2-inch color monitor capable of showing a wide range of animations, videos and album art. The interface has stylish, illuminated buttons and a backlit dial. In addition, the power output is impressive considering its size and price. At 320 watts and 80 watts per channel, it's one of the most powerful stereos I tested.
However, this stereo is just a multimedia player. The BV7260B plays only MP3s from a USB drive or streams audio from phones or music players via Bluetooth. It doesn't have a CD player and it can't play lossless digital audio formats like FLAC and WAV. It's a great option if your listening habits are limited to streaming audio from Spotify or Pandora, but if you have more discerning and varied musical preferences, it isn’t powerful enough.

Why Trust Us

Top Ten Reviews has reviewed car audio systems since 2010. I started reviewing car stereos in 2013. However, my passion for high-fidelity audio reproduction goes back to the late 1990s when a band I was in entered the recording studio for the first time. In the decades since, I have spent hundreds of hours in recording studios training my ear, studying frequency charts and learning the physics of creating great audio. My bands have recorded five albums in professional studios, and I've personally recorded an additional six albums on my own. I bring more than 20 years of experience to reviewing, evaluating and testing car audio components.

My passion for car audio began in 2002 when I purchased my first car. The car, a 1987 Honda Civic CRX, cost me $1,200 and had over 250,000 miles, but I bought it primarily for the sound system. It featured a high-end amplifier, an 18-inch subwoofer with a custom box and top-of-the-line speakers. The way I see it, I bought a mobile sound system, not a car. That's largely been my perspective on car audio systems since.

How Much Do Car Stereos Cost?

There are four kinds of car stereos to consider when looking at price.

• Multimedia players are the most affordable, costing between $20 and $100. These are designed to play only digital formats and music streaming via Bluetooth.
• Single-din stereos cost between $50 and $300. These are the slimmer types of stereos and feature CD players and a wider range of format options, including Bluetooth.
• Double-din stereos are about twice as big as single-din and feature most of the same features, but typically have more power and far better displays. These typically cost a little more than single-din as a result, but not a lot more. The low-end double-din options start around $80.
• Entertainment and Navigation stereos are the most expensive, ranging between $300 and $800. These stereos double as DVD players and in-dash navigation systems.

How We Tested

The best stereos noticeably upgrade to your car's audio quality. This starts with the quality of the audio signal sent to the speakers, but it also depends on control features like EQ filters and time alignment, which help make up for deficiencies in your car's acoustics.

Only after considering audio performance should you factor in the quality of the stereo’s display. And even then, you should first consider how easy the display is to navigate without looking, since you can’t take your eyes off the road to make changes while you drive. After that, style features, like how many colors the display can reproduce, are fun extras.

Audio Quality
Testing audio quality posed a challenge, as I didn't have a car to install these speakers in, and you can't simply plug a car stereo into a standard outlet. To overcome this challenge, I took a crash course in electrical wiring and learned how to use a DC converter to power the car stereos in the Top Ten Reviews Audio/Visual lab.

I tested stereos using our favorite speakers from the car speaker testing I did. I set them up in a front and rear speaker configuration so I could recreate, as best I could, the distances between the speakers in a standard sedan. In this configuration, it was easy to wire each stereo to the speakers.

I played music using all the available input sources – AUX, USB, CD player and Bluetooth. As I listened to a playlist that showcased different music styles and listening preferences, I adjusted the available EQ settings and used the time alignment feature, if the stereo had one.

I also gauged how much I could adjust and control the sound. This is important because every car is different, and a stereo that sounds great in one might sound lifeless in another. However, if you can control the frequency bands, you can optimize the sound to your vehicle.

Display Interface
Car stereos are often very colorful and flashy, but style comes second to ease of use. To evaluate this, I looked at the most-used buttons: pause/play, volume, skip, repeat and phone. You should be able to quickly identify and access these controls so they don’t become a distraction while you drive. In fact, the best stereos make it easy to navigate their controls without looking at them. That way, you don't have to take your eyes off the road when you want to answer a call or skip a track.

After grading ease of use, I looked closely at the quality of the display. With most stereos, you get what you pay for. If you want a display with cool animations and easy-to-read text that isn’t in the digital font, you have to pay for it. But if you're fine with a display that simply changes color and has outdated digital text, then you'll do fine with an affordable stereo.

Car Audio Systems: What to Consider Before You Buy

Every car has different acoustic challenges. Things like the ceiling shape, seat material, dash material, engine sounds and carpet density can affect the overall quality of your music. This is why a system that sounds great in one car can sound terrible in a different car. So, as part of my research, I consulted with experts in the car audio industry to get tips and advice that can help you make the best decision as you upgrade your audio equipment.

I consulted with Steve Stern, president of MECA (Mobile Electronics Competition Association). Based in Nashville, Tennessee, MECA is a car audio association that organizes some of the most popular car audio competitions in the U.S. It is the authority on high-end car audio.

I also consulted with a few professional car audio techs from the Sound Warehouse, a local Utah car audio store. They earn their living selling and installing car audio equipment.

Professional Installation
When asked what the most common mistake consumers make is, Stern pointed at the installation. He suggested that you need to 'make sure you get the most out of your audio system by doing the best installation possible. A tight install can work to bring out the best in even the most basic, inexpensive equipment.'

The audio techs echoed the same sentiments as they gave me a tour of the shop. They showed me the various wire gauges, connectors, fuses and other equipment in the shop, explaining how it's often the little things, like the quality of the wiring, that can affect the quality of an audio system. The techs argued that you shouldn't attempt to install your stereo equipment if you don't have experience with electrical wiring. Openoffice writer bagas31 windows 7. You'll avoid frustration and mistakes while getting the best signals to your speakers if you let a pro do it.

Matching Compatibility
Another common mistake, according to Stern, is when people fail to get a stereo that is compatible with their speakers. What he's referencing is the power handling specifications.

Both speakers and stereos have specifications for peak power handling, continuous power handling and impedance. The most important of these is impedance. If your car speakers have an impedance rating of 3 ohm, then you need to make sure your stereo is also rated for 3 ohms. Most stereos are rated for an impedance range, such as 2 to 8 ohms, which means you can use any speakers that have an impedance within that range.

Matching incompatible speakers and stereos can result in blowing the speakers or burning out the stereo's amplifier. But mostly, you won't get the best audio performance.

Consider Output Voltage
Most of the car stereos I reviewed have power outputs of about 200 watts overall, or 50 watts per channel. This is plenty of power to reach ear-damaging volumes on four speakers, which I know because I tested the stereos with a decibel meter, and they all reached over 100 dB.

However, you might be interested in expanding your system to additional speakers and a subwoofer, especially if you want to drive high-fidelity speakers. If this is the case, choosing a stereo with a high output voltage is key to getting the best audio. The higher the voltage, the cleaner the signal to the amplifier. This helps minimizes noise in the signal processing through the amp. Typically, this voltage is one of the delineating factors between a high-end stereo (4 volts to 6 volts) and a cheap stereo (1 volt to 2 volts).

Car Speakers
When asked whether you should upgrade your stereo or your car speakers first (assuming both are in working order), Stern said that it depends on how old the stereo is. If the audio system is very old, he recommends replacing the stereo before you replace the speakers. But he also says that if the stereo’s electronics are in good shape, then upgrading to high-performance speakers and adding a 'specialized multi-channel amp, or the best amplifier you can afford,' is your next best option for upgrading your audio experience. Lastly, he recommends upgrading the wires connecting the speakers to the amplifier or stereo.

Car Subwoofer
If you want to take your car audio to the next level, adding a 10-inch subwoofer 'in a quality box, with most stable power source you can afford' is a great place to start, according to Stern.

Without a subwoofer, your car speakers are charged with producing the entire frequency range. Depending on the type of speaker, this usually means sacrificing midrange detail for good bass or vice versa. But with a subwoofer, you allow the midrange and high frequencies to be played on the car speakers while the woofer takes over the bass. Overall, the audio quality improves and is more accurate.

In addition, subwoofers allow you to feel the music more because bass is the most percussive frequency range. This also adds to the listening experience, making it sound livelier.

Car Amplifier
If you add a subwoofer, you need something to power it because your car stereo isn't designed to drive a subwoofer's huge woofers. This means you need to add an amplifier. These devices also allow you to push higher-quality speakers, and they do a better job of separating frequencies.

Acoustic Modifications
Every car has its own unique acoustic landscape. Sometimes the interior is excellent for audio – other times, not so much. If you've upgraded every aspect of your car sound system but are still not happy with the audio, you should consider making acoustic modifications. Typically, this means installing sound dampening pads in the doors and hood. This can minimize road and engine noise, as well as keep the interior from getting too much acoustic feedback.

What Is a Factory Sound Processor?

A growing trend in the automotive industry is to build comprehensive in-dash systems, sometimes with large touchscreens resembling a tablet. These systems allow for exceptional functionality through the manufacturer’s system, but it also means it can be very difficult, costly or impossible to replace or upgrade the stereo.

This problem has a lot to do with the way the receiver is tuned by the manufacturer to get the most out of the car’s factory speakers. The tuning shapes the sound to be more dynamic, allowing the cheap speakers to sound pretty good. At first. But eventually the speakers wear out and sound dull. However, if you upgrade the speakers, the audio signal isn’t tuned for the new ones. This often leaves people frustrated after upgrading their speakers only to find the sound quality didn’t improve or got worse.

To fix this issue, you might want to consider a sound processor. Rather than wiring the receiver directly to the speakers, you wire the receiver to the sound processor. It cleans up the signal by removing all the sound-shaping tuning applied by the receiver before sending the signal along to your speakers or amplifier. In this way, it gives you a lot more control over your audio system's sound quality when you’re unable to upgrade the receiver.

However, a sound processor isn't a cheap workaround. Even the affordable ones cost about as much as good aftermarket stereos, ranging from between $150 to $800, depending on quality and features. That said, if you’re a serious car audio enthusiast, the high-end processors provide unparalleled control over tuning and the upgraded components you add to it. For example, the $700 Rockford Fosgate 3Sixty.3 connects to your laptop via a USB port so you can use software to completely shape the audio signal to fit your preferences and your vehicle.

Related Product Reviews

• Hardware >PA

JBL Vertec line array. Photo courtesy of Harman Pro.

If you've been to a biggish gig or a festival in recent years, you've had the pleasure of hearing line arrays of loudspeakers in action. But why are line arrays the current 'best practice' in large–scale PA, how did they evolve, and will they ever filter down to more modest gig venues?

Here's a chance to show off what you know about live sound engineering. Simply complete the following sentence: The function of a PA system is to..

That wasn't hard, was it? But in case you're struggling, the function of a PA system is to deliver your sound to the audience, and deliver it well. It's as easy as that. But hang on, it doesn't seem to be all that easy, does it? Whenever have you experienced perfect sound as an audience member? And when have you ever felt that your band's sound has been delivered to the audience as well as it should have been? There must be additional criteria that need to be fulfilled to achieve satisfaction. And yes, there are. Three..

• Adequate level, in relation to purpose (clearly, heavy rock music needs to be louder than a classical guitarist).
• Low distortion, low noise and a flat frequency response.
• Adequate clarity, in relation to purpose (speech requires near–100 percent intelligibility; all the words in a theatre musical must be easily understood; other forms of music may not need to be absolutely crystal clear).

Achieving adequate level is never a problem. It hasn't been a problem since the 1970s, when PA systems as we know them today had fully matured. All you need is a recognition of how many watts you require for a particular venue, usually calculated by rule–of–thumb and reference to past experience, and the budget to hire enough amplifiers and loudspeakers. Achieving low distortion, low noise and a flat frequency response hasn't quite been fully solved, although if the noise level of your PA is audible to the audience there's a fault somewhere in the system: power amplifiers in general have a better signal–to–noise ratio than just about anything else you'll find in the whole of sound engineering. The frequency response of PA loudspeakers, however, leaves a lot to be desired, and it is definitely true to say that the only thing that produces more distortion than a loudspeaker is the lead guitarist's screaming Marshall on overdrive. But even though not all is yet perfect regarding the above points, most people find the sound quality of a decent PA system acceptable. And the typical sound of a PA has almost defined people's expectations of what a PA should sound like. A circular argument, perhaps, but there's a lot of truth in it.

There's still one point left unanswered: that of clarity. It is possible for a PA system to be capable of detailed, analytical clarity within itself. But when deployed in a real–life concert scenario it sounds anything but clear. You must have experienced it yourself many times as an audience member — that fuzzy mush of sound that clogs up your ears, but you can't really resolve it into music. Clarity, therefore, is the last unconquered frontier of PA. It is the last major problem that remains difficult to solve.

At this point I need to return to one of the requirements of PA that I previously said had been solved: that the PA system should be loud enough. There's no difficulty in making it loud enough, providing you have the budget — but it has to be loud enough for all members of the audience, and that's a problem that isn't necessarily solved just by spending a lot of money.

There are two scenarios here: one where the audience are seated, the other where they are standing and free to move. If the audience are free to move, it is acceptable to have different levels in different parts of the venue. Those who like it loud will gravitate towards the loudspeakers. Those who perhaps want to chat during the show will move further away. However, if the audience is entirely seated it suddenly becomes much more difficult. You don't want to deafen the front rows of the audience while leaving those at the back struggling to hear. If only certain members of the audience are delivered a level that is adequate, without being too quiet or too loud, the PA has not fully met its purpose. Let me therefore refine the requirements of PA into this simple statement: all of the audience should enjoy high–quality sound that is loud enough and clear enough.

Predicting Loudspeaker Behaviour With MAPP

MAPP Online is the Multipurpose Acoustical Modeling Program developed by loudspeaker manufacturer Meyer Sound to model the sound fields developed by its products in a variety of configurations. A sound designer is able to enter data into MAPP Online, including individual loudspeakers and arrays, then click the 'predict' button and get a graphical display of the expected coverage. Meyer Sound claim that MAPP will allow the user to:

• Plan an entire portable or fixed loudspeaker system and determine delay settings for fill loudspeakers.
• See interactions among loudspeakers and minimise destructive interference.
• Place microphones anywhere in the soundfield and predict the frequency response, impulse response and sound pressure at the microphone position.
• Refine system design to provide the best coverage of the intended audience area.
• Use a virtual equaliser to pre–determine the correct settings for best system response.
• Gain load information about the array, to determine rigging capacities.

Clearly, a system such as this, that is accurate in its predictions, is a tremendous tool for the sound designer. MAPP Online will run on Windows, Macintosh or Unix computers, and data that the user enters is sent to Meyer Sound's servers, where the analysis and prediction is made, then delivered back to your desktop. The example shown is a composite of two predictions made for arrays of Meyer Sound MILO cabinets, one with just three loudspeakers, the other with 20, both at 1kHz. It is clearly possible to see how much more directional, and how much louder, the larger array is. You can also clearly see the 'side lobes' that develop — an unfortunate by–product of all line arrays that the sound designer must take into account.

Cover The Audience, Not The Walls

A paramount rule of PA is to direct the sound towards the audience and not elsewhere. But how often do you see this rule flouted? The best and most classic example of this not being done was in several London Underground stations, some years ago. At the time, the tube network was decaying and falling into disrepair, so several stations were refurbished with bright, modern designs. Along with the visual aspects, these stations were given new sound systems too. Some bright spark designer decided that the loudspeakers should be mounted in cylinders (cylinder = tube, get it?) and several should be mounted at intervals along the platform, parallel to the platform and just above waiting passengers' heads. The result was that from any point on the platform, you could hear every loudspeaker, with delays increasing with distance. It was, indeed, possible to stand as close to a speaker as you could and still not understand what was being said! This state of affairs wasn't allowed to continue for long, and now the speakers point as they should — down at the passengers on the platform.

So the most important thing is to point the loudspeakers at the people in the most direct way possible. At the same time, consider how much sound is being 'sprayed' onto the walls and ceiling. The audience will absorb much of the sound energy that strikes them, meaning that it won't be reflected to bounce around the auditorium and cause confusion. But the walls and ceiling are very likely to be reflective, so the more sound that goes in these directions, the more mush–inducing reflections will be created.

The EAW CLA37 column loudspeaker uses seven 3–inch drive units to achieve a coverage of 120 degrees horizontal x 30 degrees vertical, thus controlling the vertical dispersion tightly. It is suitable for speech reinforcement in large reverberant environments if several or many units are distributed amongst the listeners. In a situation where the information content of speech is of primary importance, the classic solution to intelligibility is to use many small loudspeakers and have them close to the people — obviously, pointing at them and not at reflective surfaces. This works extremely well and the information content gets through clearly. But this solution is not acceptable for a musical performance. The reason for this is that we expect a performance to take place on a stage. We watch the performers on the stage, and we expect the sound to come from the stage too. If the sound were coming from a small speaker mounted at just a couple of metres distance, up and to the side, that would cause a conflict between the visual and the auditory. Everything might be clear and intelligible, but we wouldn't enjoy the performance.

So the multiple small speaker solution doesn't work for performance. We need the sound to seem as much as possible as though it comes from the stage, and for this you can't do better than actually having loudspeakers at the sides of the stage, like a great big stereo system. However, there are still potential problems..

The first problem has been mentioned already and has to do with directivity. Loudspeakers naturally have a characteristic directional response — almost omnidirectional at low frequencies, tightening to a focused beam at high frequencies. Put another way, anyone sitting directly in front of a loudspeaker will experience a reasonably flat frequency response, but people sitting further and further to the side will hear less and less high frequencies, so the sound will be increasingly dull. So the 'big stereo system' style of PA suffers in that it sprays the walls and ceiling with low–frequency and low–mid energy that reflects into a confusion of reverberation, and only select members of the audience receive sound with a good balance of frequencies.

A second problem stems from the lack of directional control. Because much of the sound is spread widely, beyond the width of the audience, energy is lost. The more sound spreads out, the more thinly its energy is spread, and therefore the more level is lost with distance. This is an important point. The reason a sound source becomes apparently quieter as it becomes more distant is primarily because its energy is spread out. Yes, some level is lost through absorption in the air, but not much. It's distance that's the killer. An audience member sitting a long way from the loudspeakers will experience a distant and therefore quiet sound, while audience members close to the speakers are getting their heads blasted off!

Let's think in terms of light. Take a torch bulb. Intrinsically it emits light almost equally in all directions, so by itself it isn't much use for finding your way in the dark. But put a reflector behind it and a lens in front of it, so that its energy is concentrated into a beam, and you will notice immediately that it is now usefully bright. You'll also notice that the beam extends into the distance. So not only do you see the immediate area in front of your feet, but the area beyond where you direct the beam. The area of coverage is less, but you can now see where you're going. If the same could be done with loudspeakers, there would be two benefits: one, that the sound is focused on the audience and away from reflecting surfaces; and two, that the sound retains its level as it travels. So the audience members at the back are served as well as those at the front, and the difference in level between front and back is much less.

Directivity Theory

If you understand the theory behind the directional characteristics of sound sources, you'll be in a good position to understand PA loudspeakers and get the best out of them. There are two extremes of directionality, between which there are other interesting cases. One extreme is the point source, which is a source of sound that has zero size. OK, there's no such thing as zero size, but in practice if a sound source is dimensionally smaller than the wavelength of sound it is emitting, it has the characteristics of a point source. The low–frequency output of a small loudspeaker would be a real–life example.

A point source emits sound equally in all directions. There you have it: all you need to know about the point source! Well, not quite all.. but you'll need a little imagination. Imagine this very small point source pulsating outwards momentarily, just once. A sphere of high pressure leaves its surface and radiates outwards, becoming larger and larger. The point source has put a certain amount of energy into this pulse, and that same amount of energy over time has to cover a larger and larger area, the surface area of that continuously expanding sphere. I could at this point bore you to tears with detailed calculations concerning the surface area of a sphere, energy density and stuff like that, but instead I will cut directly to the chase and say this: for a point source, sound pressure decreases by 6dB for every doubling of distance. We call this the inverse square law.

One mistake or over–simplification is that it is commonly said that all sound obeys the inverse square law. This is not so. Only sound from a point source obeys the inverse square law. Any sound source that is not omnidirectional does not obey the inverse square law. (If you get so far away from it that visually it recedes to a point, from your point of observation it will appear to obey the inverse square law, but in practical terms this is not relevant to PA).

A four–module array of Renkus–Heinz STLA/9 cabinets.From this we can derive two interesting facts. The maximum rate at which sound level can decrease with distance is 6dB per doubling of distance. The only way sound can decay at a faster rate than that is if you actively do something to block it. Also, sound sources that are directional decay at a rate that is less than 6dB per doubling of distance.

It's interesting to consider the opposite extreme. Would it be possible to have a sound source, the level from which does not decay at all with increasing distance? Amazingly, the answer is yes. It is possible to have a sound source that is so focused that it will cover an amazing distance with hardly any reduction in level. You want an example? I'll give you two examples: an old–fashioned ship's speaking tube, and a tin–can telephone. We call this kind of sound source a plane source. In both cases, the sound energy isn't just focused, it is constrained to travel within an enclosed medium so that it cannot spread out at all. And since it cannot spread, no level is lost. (In practice, a little level is lost, but nothing's perfect.) You can see that this is not a practical way of delivering your sound to the audience, so we will leave it as a curiosity, but a curiosity that demonstrates a useful principle.

The next type of sound source is the whole purpose of this article, and is the salvation of PA as we know it. We call this type of source — fanfare of trumpets — the line source. To understand it, lets go back to the point source for a moment. I said that the point source (which is omnidirectional) needs to be small in comparison with the wavelength of sound that it is emitting. The converse is true too: when a sound source is larger than the wavelength it is emitting, it becomes more directional. And the larger it is, the more tightly directional it is. So a really large sound source would be tightly directional. This is what we want: a source that can be focused and directed to cover the audience, but not wasted on other areas of the auditorium.

But imagine you're a loudspeaker looking out from the stage to the audience. The audience in front of you are spread widely from left to right, but from top to bottom — in perspective, from the rear rows to the front — there is only a narrow spread. You can see the problem. If you made a large loudspeaker that focused the sound tightly enough to direct sound accurately in the vertical dimension, it wouldn't cover the full width of the audience. And vice versa: if it covered the full width, you'd end up covering the ceiling as well, and we know that's a bad thing.

The solution is to devise a loudspeaker that is tightly focused in the vertical dimension but spreads sound widely in the horizontal dimension. To do this, the speaker needs to be large vertically, but small horizontally. Like a column, in fact. And here we have it (bigger fanfare of trumpets): the column loudspeaker! Did I say 'column loudspeaker'? Sorry, I must use the more up–to–date and exciting terminology: line array. They are both examples of the line source.

Deploying The Line Array

Clearly, you're not going to have a full–scale line–array system in the back of your band's Transit van. In fact, playing through a line array for the first time may mark your transition from wannabe band to successful band. But there will come a time, hopefully, when you are called upon to have an influence in the specification of your touring PA system. At first, the line array looks intimidating. All those cabinets, all that cable. Who's going to go up there and string the whole thing together? The answer is nobody, because the system is assembled at stage level and the whole thing hoisted up. The motorised hoists even have remote controls so that no–one has to shout instructions or converse through an intercom. A line array can actually be set up by as few as two or three people. Any kind of flying, however, involves considerable responsibility, and manufacturers are keen to use the words risk, damage, injury and death frequently in their operators' manuals. Apparently, the most dangerous part of the rigging process is when the equipment is at stage level. As it rises into the air, providing everything is done correctly and the equipment is in good condition, it flies out of the danger zone.

Setting up a conventional PA system on stage involves a certain amount of use of of rules–of–thumb. The line array is far too big a thing to set up in the same way, and once it's set up you don't really want to have to move it, so you need to be sure that the positioning is right, the height is right, the horizontal angling is right, and — most of all it — that the array takes up the optimum J–shaped curve to distribute sound evenly to the front and back of the audience, and everyone in between. To make this possible, manufacturers commonly provide software that can be used to calculate all the necessary parameters, examples of which are shown on the following two pages. Meyer Sound are good enough also to advise equipping yourself with binoculars, laser measuring tool, pedometer, laser inclinometer and a self–levelling, four–way laser. That should really be a last resort, as any decent venue should have a set of plans with accurate measurements!

The Column Loudspeaker

I often think that one of the best lessons of the past is not to go there again. However, the column loudspeaker has as important a place in the history of PA as the electric guitar does in rock music. Yes, really. One day there might be people who make a living as historians of PA, and they'll be able to tell us exactly how the column loudspeaker came to be developed. Until then, my guess is that it developed by chance and was found to work effectively. It seems like a natural development for a 1960s band to have speakers at either side of the stage for the vocals. Then they decide they want to be louder and need speakers with multiple drive units. But speakers that are wider take up more stage area, so they choose speakers that are taller. The typical pub band of the 1960s would therefore have a pair of column loudspeakers, for vocals, that typically would contain four 10–inch or 12–inch drive units, sometimes topped off with a small horn (for example, the WEM Vendetta). Although they might seem primitive now, in fact they worked surprisingly well. The small horizontal dimension meant that the full width of the audience was covered, while the large vertical dimension ensured that the sound was 'beamed' to the back of the room. However, the next generation of bands working at a higher level of the business moved on to 'bins and horns'. (A horn loudspeaker is the most efficient way of converting amplifier power to sound. A 'bin' is a bass loudspeaker, which is commonly in the design of a folded horn. 'Bin and horn' systems of adequate physical size can sound very good, but their directionality is not necessarily well controlled.) Small bands followed suit with similar but scaled–down systems, and the column loudspeaker was forgotten. Small column loudspeakers, however, continued very successfully in speech PA, such as for places of worship, where intelligibility is all–important (see the photo below). The 'bin and horn' system amounted to nothing more than the 'big stereo' commented on earlier, and directional control was lacking.

The next real development in PA technology was the centre cluster, much used in musical theatre. The centre cluster relies on another directional technology known as the constant directivity horn. The idea here is to combine multiple full–range loudspeakers, each of which is designed to have a consistent directional pattern over a wide range of frequencies. Horn loudspeakers can be designed to do this reasonably well. These full–range loudspeakers are arrayed together into a part of a sphere and mounted high up to cover the whole of the audience. Each member of the audience is delivered sound through only one full–range loudspeaker (apart, of course, from people sitting exactly on the dividing line between the coverage of two loudspeakers).

The centre cluster is outstanding for its intelligibility. It fulfils the criterion of directing sound only at the audience, and has the additional benefit that it forms a single sound source, therefore there is no possibility of hearing delayed sound from another loudspeaker somewhere else in the auditorium — at least, in a pure centre–cluster system. But there are two problems: the first is that ideally the centre cluster would be designed first, and then the auditorium designed around it! The second is that if each audience member is delivered sound (apart from the exception noted) by only one loudspeaker, plainly there is going to be a limit to how loud the sound can be. There will always be a role for centre clusters but, as we shall see, there are more flexible (literally) forms of loudspeaker distribution.

The Line Array

Although the column loudspeaker was effective in its context, it suffered from a lack of scale and a lack of science, each equally important. So to scale up a column loudspeaker to auditorium proportions took the best part of three decades. Still, we got there in the end. Here comes the science..

Going back to the point source, we find that level drops by 6dB for every doubling of distance. With the plane source, the level doesn't drop at all. So is there an in–between condition where the sound level drops by, say, 3dB? Yes there is, and it is the line source, which in theory can produce a cylindrical wave, as opposed to the spherical wave of the point source. A genuine cylindrical wave will have 360–degree dispersion in the horizontal dimension and zero dispersion in the vertical dimension. Any real–life source is going to be an approximation of this, but if someone offered you approximately £100, you would accept £75, wouldn't you?

A Meyer Sound 12–cabinet MICA array.Earlier, I said that to achieve directionality a sound source needs to be larger than the wavelength it is producing. To achieve focus, or near–zero dispersion, which is a more stringent requirement, it needs to be somewhere approaching four times the wavelength. The wavelengths of audible sound extend all the way to 17 metres (20Hz) and beyond. But taking a reasonable lowish frequency of 170Hz with a wavelength of two metres (taking 340 metres per second as a nice round figure for the speed of sound), a line source eight metres high will be necessary. Quite tall! But at least we have a notion with some science behind it.

The next question is: how exactly do you make a loudspeaker that is several metres high? Currently, the way to do it is to stack multiple loudspeakers on top of each other. But instead of stacking 10–inch or 12–inch loudspeakers featuring identical drive units with poor HF response, as they did in the 1960s, each loudspeaker consists of LF and HF drive units and covers the full audio range (down to a reasonably low frequency). Also, rather than making one very tall cabinet, the modern line array consists of multiple small cabinets. The benefit of multiple cabinets is that you can assemble a line array that is as big or small as you like, or can fit in, or can budget for. You can also manipulate the shape of the array, which, as we shall see shortly, has significant benefits. Time for more science..

Since the line array is not actually one single tall–but–narrow drive unit, but is made up from discrete loudspeaker cabinets, one has to ask whether the individual units will couple together as though they were a genuine line source? The answer is yes, they will, but only where the drive units are separated by less than half a wavelength. This is easy for the lower frequencies, but more difficult to achieve as the wavelength shortens. As a benchmark, the wavelength at 400Hz is around 85 centimetres. So to couple at 400Hz the cabinets have to be less than 42.5 centimetres high. OK, that's doable, but we are not even halfway up the audio band here.

Still, at least we know the criteria to aim for. The longer the array is, the more tightly directional it will be in the vertical dimension, and for individual cabinets to couple well into the array, they have to be small vertically. The better both of these criteria can be achieved, the more controllable the beam of sound from the array will be. A good point is made by Ralph Heinz of PA manufacturers Renkus–Heinz: 'The answer to the question of whether a line array is a line source is 'almost never'.' Heinz's comment demonstrates that a theoretically perfect line source is virtually impossible to achieve. Only the best line arrays will come close.

Waveguide

I wouldn't be surprised if some of the readers out there are microwave engineers concerned with the efficient transmission and reception of microwave signals, SOS readers tending towards the technical. To you guys and girls, I'd like to say thanks — you gave us all the technology we need to make great–sounding line arrays. Seriously, a lot of loudspeaker technology does borrow from microwave technology, as the wavelengths of microwaves and sound waves are comparable. I have said already that to couple together into a line source, or at least a close approximation of a line source, individual sound sources must be no further apart than half a wavelength. You can turn this around and say that the closer together the individual sound sources are, the higher up the frequency spectrum line–source behaviour will be maintained. So each individual cabinet must be as short as possible in the vertical dimension. For preference, the height of the cabinet should be no more than the diameter of the low-frequency drive unit plus the thickness of the cabinet walls. However, to achieve a high sound level, clearly the low–frequency drive units will have to be reasonably large. In the Meyer Sound M3D, for example, 15–inch (38cm) drive units are employed on either side of the high–frequency unit. Since 38cm is half a wavelength at around 450Hz, an array of M3D cabinets will approximate to a line source up to around this frequency. Above 450Hz, the directional characteristics will begin to depart from the ideal cylindrical wave, although not immediately.

Many manufacturers of line array systems provide software for calculating optimum configuration and placement, which clearly will depend on each individual venue. Here we can see a calculator from McCauley that's particularly striking in its visualisation. You can enter the type of cabinet and quantity to be deployed, and the dimensions of the area to be covered. The software instantly shows the necessary angling of the cabinets (top right) with rigging information (top centre–left). In the lower–left panel, on the left we can see the line array surrounded by a graphic showing the vertical dispersion pattern. Listening points can be selected and the frequency response at those points will be displayed in the panel at centre left. So what happens above 450Hz in the case of the M3D? At 580Hz the signal is crossed over from the low–frequency drive units to a specially designed high–frequency driver. What is special about the design? Well, to make the whole concept of the line array viable, each individual cabinet has to be a line source in its own right, or at least approximate a line source as closely as possible. For this, the high–frequency drive unit needs very sophisticated design to produce the required wavefront that diverges hardly at all in the vertical dimension. There are several possible techniques for doing this — some practical, some not.

One possibility is the ribbon drive unit, which basically has a long, thin diaphragm up to around 15cm high. Incorporated into line–array cabinets, the ribbon driver will display at least reasonable line-source behaviour above around 4.5kHz, but below that point adjacent units will be more than half a wavelength apart and therefore will not couple correctly. For good coupling at higher frequencies, the high–frequency driver should radiate over at least 80 percent of the height of the cabinet. Ribbon drivers, in any case, are rather low on output when compared to more conventional compression drive units. A horn with compression driver would be another possible choice, but for a horn to have a suitable direction pattern and a mouth area covering 80 percent of the height of a typical enclosure it would need to be inconveniently long. A reflector can also be used to focus sound, as in the Nexo GEO system. However, it seems that the current favourite technique is the acoustic lens.

It's worth thinking for a moment about how an acoustic lens could be created. A lens for light works by slowing down light rays in a transparent medium of higher refractive index than air — i.e glass. This could be done for sound. Simply form a suitable medium into a lens shape and situate it in front of the drive unit. Sounds too simple to work? No, not at all, and this technique is indeed employed by Electro–Voice and McCauley. The lens is made out of foam, which acts as an 'obstacle array' around which the sound wave has to pass, thus slowing it down. The foam doesn't have to have the conventional lens shape, as it can be of variable density, which provides the 'shaping'. Foam does have its limitations, as you would expect. At high frequencies it will absorb sound rather than slow it down, and at low frequencies it will have no effect. Nevertheless, the fact that it is used for some current line–array systems demonstrates that it is a viable solution to the problem.

The other way of producing an acoustic lens is the path–length refractor. This uses metal plates to direct sound through channels. The channels have varying lengths and therefore sound can be slowed down by varying amounts of time. With appropriate design, this can form a perfectly viable lens that works over a reasonably wide range of frequencies. Obviously, since there are four different techniques currently in popular use in this application, the ultimate solution hasn't quite been found yet.This EAW calculator superficially doesn't look as polished as the McCauley one, but it offers presets for different types of venue. This example shows a small theatre with a balcony, which is also covered by the line array. The software shows, by colour coding, the levels that can be achieved in different sections of the venue.

Intensity Shading & Divergence Shading

We've covered a lot of technical material so far, and it's worth going back for a moment to the purpose of the line array, which is to deliver sound to the entire audience, at pretty much the same level, all the way from the front to the back. It does that by focusing the sound vertically while allowing it to spread out horizontally. Even though a well–designed line array can achieve that reasonably successfully, it will remain the case that the front of the audience receives a higher sound–pressure level than the rear of the audience — which, of course conflicts with our requirement. The solution to this is intuitive: simply reduce the output of the lower section of the array. This is known as intensity shading. The front rows of the audience are much closer to the lower cabinets than they are to the upper cabinets of the array, therefore reducing the level from the lower cabinets will deliver a lower sound–pressure level to the front of the audience. However, there is a problem here: the front rows will still hear sound coming from the upper cabinets of the array, and they will hear it clearly because these cabinets are louder. But sound from the higher cabinets will be delayed with respect to the lower cabinets, and that will create an interference pattern and an uneven distribution. This problem could be tackled with equalisation and delay, but that would destroy the elegant concept that the line array is.

The alternative to intensity shading is simple and obvious, and you would probably do it by instinct anyway. When a line array is flown, it will take you precisely two seconds to observe that the front rows of the audience are almost underneath the array, whereas the rear rows are much more on the same level as the top of the array. So it seems appropriate to curve the lower section of the array so that it points down at the front of the audience. You have just created the familiar 'J' shape of the practical line array (see screen above). You have also implemented divergence shading. Simply by angling the cabinets apart more, you have required the sound they produce to cover a wider angle, therefore its intensity will be reduced at the listening position. Ideally this requires a more divergent cabinet for the curved part of the J, which manufacturers solve by designing specific long–throw and front–fill cabinets.

Line Arrays For The Gigging Band

If line arrays are good for top touring acts, surely they're good enough for the small gigging band too? In my view, it can only be a matter of time before manufacturers of small PA systems (many of whom make large–scale systems too) bring the line array into the small pub and club venue. There is a vacuum at the moment that desperately needs to be filled. Oddly enough, since a large–scale line array is composed of multiple small cabinets, there is absolutely no reason why you couldn't stand one on stage and stack it all the way to the ceiling, taking safety precautions of course. The limitation on small–scale deployment of line–arrays is actually ceiling height. In a large auditorium, the line array is hoisted high over the audience, so that the lower section of the J–shape points down at the front rows, while the upper cabinets point roughly horizontally at the rear of the audience. Raising the array like this reduces the difference in distance between front and rear, thus reducing the level difference due to distance. In a small venue, the line array would fire into the audience as much as it fires over their heads. Although the approximation to a cylindrical wave it produces would be advantageous, the loss of the downward perspective severely limits this advantage. And, of course, in a small venue the audience bunch up around the stage, so the front rows are very much closer to the loudspeakers than the people at the rear.

Contacts

By now, you should be realising that there's a awful lot to know about line–array technology. There simply isn't room to cover it all here, plus the top manufacturers are constantly researching new developments, particularly with regard to focusing and steering of arrays. Although we wait for line–array technology to re–emerge as a major force at the gigging band level, my expectation is that it will. Although line arrays need to be large to work at their best, in respect of directional characteristics, there is no reason why smaller bands should not take advantage of the technology. Indeed JBL have scaled down that contained in their large–scale Vertec series (shown at the start of this article) into the new VRX932LA, designed for smaller venues. Each cabinet contains a 12–inch LF drive unit and an HF horn, designed for arrayability. Practical array sizes start at just two or three cabinets, and JBL advise up to six for optimum control over dispersion. A six–cabinet array would have to be flown, just like a full–scale line array, but JBL have cleverly provided the option of mounting two cabinets on a tripod stand, or on a pole on top of the SRX718S subwoofer.

An understanding of the directional properties and coverage of loudspeakers and arrays can only benefit the successful delivery of sound to the audience. Great sound should not only be the province of the large-scale auditorium PA, but should be available to all, at a reasonable price.