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Speakers: Surround Sound for Dummies!

Do you know how to position your home theatre speakers? How to get the best sound from your space? Which surround sound system to choose?

Recently, while I was in an audio and electronics store waiting for a microphone, a man came in and asked the salesman for an X wireless sound system. I automatically stopped the ear.

Apparently the man wanted the same sound system that his friend had installed in his new house. That was all the information he had on the equipment. The salesman, with no friends with that sound system, knew little less than the customer.

The wait for the microphone was getting quite long, so I decided to ask the questions out loud:

Where in your house do you want to put it?
What do you want to use it for: watching TV, listening to music on smartphones or WiFi devices, listening to vinyl records, etc?

I am small and the man was a robust gentleman, so he looked down at me strangely but answered my questions without objection.

In this article I will tell you about what we talked about, because I think it can be useful for everyone.

He finally took a surround sound system (a soundbase + a small surround sound system that came out a little less than his friend’s sound system) and I passed him my email to find out how the purchase went. I got his email today and he seems to be more than happy with his choice.

Every home is its own universe and buying a sound system is a challenge, as there is so much to choose from and information about it can be tedious, unclear and even cumbersome.

Flat screen TV speakers are a piece of junk (it’s that simple).

With the convergence of technology in recent years, a large part of the consumer public changed their old television set for a flat screen. Although they look very nice, the truth is that very few brands have really taken care that these televisions have a good sound system. The main reason is because those same brands sell the sound system separately, but improved.

Basically, any improvement you make to the sound will make a big difference.

The Sound Bars / Soundbars

When you hear about sound bars, the first thing that people often point out is that they don’t need to be wired. That that’s the highlight is rare, isn’t it?

The sound bars is a system developed in the late 90’s, which has its origins in the LCR (left-center-right) sound system. The first commercially successful sound bar was the ADA 106 from the Alec Lansing factory which consisted of a two-part system together with a subwoofer.

ADA 106 - Altec Lansing
ADA 106 Sound Bar – Altec Lansing

The sound bars integrate small speakers placed in such a way that they simulate, by bouncing the sound off the walls, the sensation of surround sound. A calibration system using a built-in microphone is used to measure the room acoustics.

Each speaker handles a different sound channel to generate the feeling of spaciousness – front left, front right, center, rear left and rear right – this depends on how many speakers the sound bar has.

Barra-de-sonido
How a sound bar/soundbar works

Sound bars are ideal for enhancing the sound of a flat screen TV installed in a small room.

Good sound bars – worth over $1000 – usually have a good subwoofer, which makes the immersive feeling much better.

Soundbar formats

There are two formats of sound bars:

● Where the bar is placed under the TV against the wall (soundbar)
●Another so-called soundbase where the TV is placed on the bar.

soundbar vs soundbase
soundbar vs soundbase

Some Problems with Sound Bars:

  • Many sound bars don’t have their own remote control but are operated from the TV’s remote control, although this may sound good at first it doesn’t always work, especially if the TV is one brand and the sound bar is another. The problem is that during the setup process, the TV’s internal speakers are disabled, but then when you use the TV’s remote to adjust the sound bar volume, the TV tells you that the volume commands won’t work because the TV’s speakers were disabled.
  • All sound bars have a virtual surround command that does not actually simulate surround sound, but rather expands the sound so that the sound bar can be heard larger than it is – much like the computer’s surround simulator – mainly those with Dolby brand surround sound cards.
  • Not all sound bars are the same size but this does not mean that because they are longer they have more speakers. Many times it’s just a longer box, you always have to check how many speakers you have.
  • The sound bar may not necessarily match the width of the TV, even if it’s from the same manufacturer.
  • Most HDTVs have an optical audio output, but no analog audio output. The idea is that you connect all your devices to the TV, then connect your TV’s optical audio output to the sound bar, but almost all HDTVs only have a three-device input, which greatly limits the amount that can be connected to the TV. One solution to this may be an HDMI connector, but this can degrade the audio signal.
  • Most HDTV’s degrade the signal to stereo so it is advisable to have a surround sound input on your TV for a surround sound bar.
  • Casi todas las barras de sonido en el mercado cuentan con sistema Bluetooth incorporado lo que hace que se puedan conectar otros dispositivos al sistema.

Wall/Ceiling Loudspeakers

They are mainly used in public places, shops, small theatres, churches, etc.

If the system is designed correctly, it does not require any special equipment other than an amplifier and an audio source, always keeping in mind that care should be taken not to overload the amplifier by keeping the total impedance of the speaker above the minimum impedance of the amplifier.

They are suitable for small venues and work very well as rear speakers for surround systems.

For a sound system with speakers embedded in the wall to work properly, it has to be placed by an expert and the necessary acoustic measurements made.

Another aspect to consider is the quality and length of the cables that will be needed to mount them.

Wall-mounted speakers have problems with low frequencies because they do not have an external cabinet. To solve (medium) this problem, we recommend placing cabinets inside the wall.

An external subwoofer is recommended for low frequency enhancement.

Altavoces de pared - In wall speakers
Altavoces de pared – In Wall Speakers

Big or Small Speakers

When we talk about size, we’re not just talking about the box.

Large speakers are those that can sound over a wide range of frequencies (reaching frequencies of 80 Hz or below), most play in the mid to high range, but many do not have the ability to reproduce a large amount of low frequencies.

This type of speaker with a low frequency range is called a small speaker (17 cm high also called a rack speaker), and needs a subwoofer to compensate for the low frequencies that the speaker itself cannot produce.

However, it is always better to have one that can reproduce a wide range of frequencies without having to rely on or resort to a subwoofer.

IMPORTANT: Between the speakers, the difference in size does not make a better sound.

altavoces torre vs pequeños altavoces
tower vs. small speakers

Size is NOT What Matters

When buying speakers, you not only have to consider the size, but also that it is consistent with the room where they are going to be installed. Speakers achieve their greatest potential in combination with the acoustics of the space in which the sound is moving.

For large environments we recommend larger ones (towers over 30 cm) together with one or two subwoofers, if you want a (well) powerful sound.

For small environments, speakers under 20 cm are recommended next to a subwoofer.

Room Sizes

Talking about sizes without mentioning measurements creates confusion so…

  • A small room is a place of less than 13 m².
  • It is considered a medium sized room with spaces between 13 m² to 25 m².
  • A large room is a room of more than 25 m².

Speaker Sensitivity

Sensitivity defines your ability to effectively convert energy into sound, therefore…

The traditional way to measure sensitivity is to use the 1 Watt 1 meter standard. This means: a microphone is placed 1 meter away from the speaker to measure the sound output (in decibels) that is produced using 1 Watt of power.

The higher the sensitivity, the less power is needed to produce sound. A speaker with a sensitivity of 85 dB SPL will need much more power to amplify the audio signal than a 94 dB SPL speaker.

A quality speaker has a minimum sensitivity rating of 87 dB.

5.1 and 7.1 System Speaker Placement

Colocación-de-altavoces

Center channel speaker:

The central channel should be placed directly on the axis, at a distance of 2 to 3 meters from the seat position (in small rooms keep the distance ratio). It is advisable that the speaker is at head height if possible, but this will depend on the position of the screen.

Front Left/Right speakers:

The main speakers should be placed at about 25°-30° off the centerline, 2 to 3 meters away from the seat position. A better sound image is obtained when the tweeters are at ear level. Most tower speakers have this position, but a shelf speaker will require a stand to position it at the proper height.

It is recommended that the front speakers be placed away from the corners of the room to reduce sound reflections.

Surround Side Speakers:

In a 5-channel system, the side surround speakers should be located about 90°-110° off center. For best sound range, the height of the treble should be about 60 cm above ear level.

Surround back speakers:

In 7.1 systems the surround back speakers are placed behind the seat position, 135°-150° off center, to generate panoramic effects.

As with the side surround speakers, the position of the tweeters should be about 60 cm above head level when sitting.

Subwoofer:

It is placed on the floor or at ground level. The low frequency sound generated by the subwoofer is omnidirectional, and as such, can be placed anywhere you wish. Take care to place it near the corners of the room or inside any type of cabinet or architectural detail.

Placing them too close to walls and in semi-enclosed spaces causes the directionality of the speaker to change from omni-directional to directional, resulting in the subwoofer sounding overwhelmingly loud and booming.


Author: Sol Rezza
Editor | Corrector: Franco Falistoco
@ 2019

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