LFE Input Explained

For the general public, connecting your audio peripheral(s) to your device(s) of choice is simple as plugging it in in the correct port with the correct cable for your peripheral.

However, that simplicity is thrown out of the window when it comes to complicated audio connections that some devices-to-peripherals and vice-versa might require. Two examples of those complicated connections would be namely Sub Out and LFE respectively. But what exactly are those two audio connections? And are both really complicated as it may sound to be? This explores both LFE inputs and Sub Out and the differences between each.

What is LFE?

Standing for Low-Frequency Effects, this type of connection is instead an audio channel that is band-limited (meaning that it has a defined finite bandwidth amount in a specialized transmission channel). This connection is frequently used for sending of low-frequency audio signals that are intense in nature, where it results in the production of emphatic sound effects in movies.

In layman’s terms, it is perfect for home theater systems that are used for watching movies and other forms of multimedia, as it brings more oomph, deepness, and loudness to the sound effects in a movie (i.e. explosions, gunfire).

lfe input
From Crutchfield

LFE Input

However, do take note that an LFE connection only sends bass-only sounds or information to the connected subwoofers. This is especially true during movie productions, wherein most of that bass-only sound or information has a frequency range of between 3 to 120 Hz (hertz).

Unlike other audio connections though, an LFE channel connection has the distinct advantage of sending encoded audio source(s) from a receiver unit or a theater system towards the connected speaker unit.

That means it has a secure connection when it comes to transferring audio data and/or information from one device to another, hence it is preferred by most movie productions as it was originally meant for them (to avoid leaks). Additionally, it is used for cinemas for its surround sound capabilities (the subwoofers placed inside the cinema walls, surrounding the audience.

LFE channel connections are mostly available on audio and theater devices that support multi-channel audio such as 5.1 and 7.1 surround sound in most receiver units of many home theater systems available in the market today.

What is a Sub Out?

Also called Subwoofer Output, this type of audio connection is a specialized audio output port found on audio receivers. Those audio receivers are designed to specifically be connected to active subwoofers of an audio system such as home theater systems (the receiver component).

There are also instances that a Sub Out will be present in active stereo receivers. Do take note that stereo speakers that use this kind of connection are connected to the main audio source’s main receiver.

The known downside to this kind of audio connection is that it only sends low bass frequencies to the connected subwoofer, regardless of how powerful the connected audio source is. The reason for this is that Sub Out ports automatically filter out high frequencies passing through it, resulting in the low bass frequencies issue. RCA cables are commonly used for this kind of connection, although LFE cables can be used as an alternative.

Don't Hookup Your Subwoofer Until You Read This - ecoustics.com
From eCoustics

Why Do Subwoofers Units Have Left and Right Inputs?

Don’t be confused when you are connecting your subwoofer unit and you see both “Left” and “Right” input labels on the ports present on its back panel. It is perfectly normal for subwoofer units needing/requiring an RCA channel connection, instead of an LFE one.

When an RCA connection is used to connect a subwoofer unit to the main component of a home theater system, once the main component receives an audio source for playback, low-frequency audio signals will be sent to both the left and right channels through the previously mentioned input ports. This makes the audio playback of low-frequency sounds meant for surround sound possible.

Left and right input ports won’t be present in older subwoofer units but will appear alongside newer ones instead, usually acting as a backup connection option if others such as the LFE channel connection fails/is broken.

Should I Use Dual Subwoofers Units?

If you are going for a Sub Out audio connection since you are either using a subwoofer unit or the main component of your home theater system doesn’t support an LFE audio connection, you might have wondered if using two subwoofer units is viable. Well, if you have the extra budget and space for a second subwoofer unit, then the answer to that is yes.

Since many audio experts and people in the audio community (especially hardcore ones) are already behind the concept of using two subwoofer units for your home theater system, might as well go for it as it will bring a more refined sound experience when viewing multimedia files such as movies, TV shows, and even when playing games.

Having two subwoofer units in a home theater system setup will eliminate the need for localizing the sound the system needs to produce. By doing so, it will produce more deep bass sound effects as a result. The deep bass even has a pseudo surround sound effect, thanks to the dual subwoofer setup.

Why Two Subwoofers Are Seriously Better Than One – M8audio.com
From M8 Audio

Additionally, the equalization of sounds (the moment wherein the volume of different frequency bands are automatically adjusted for an audio signal) coming out from the system can be also eliminated thanks to a dual subwoofer setup.

The common setup of a dual subwoofer unit in a home theater system would be that each unit would be placed on the left and right sides of the home theater system at an angled position. That position will create the pseudo surround sound effect even without the usage of both 5.1 and 7.1 surround sound and satellite surround sound speakers that are usually needed for it.

However, as the name suggests, it isn’t a true surround sound experience, as you will be not hearing sounds from your rear area (rear left, rear center, rear right) as the sound will be only coming out from the dual subwoofer units on each side of your home theater system and the main speaker units attached to the system, which are usually placed on the front of the system in a default setting.

What’s the Difference Between Sub Out vs. LFE?

Since both Sub Out and LFE are made for transmitting low-frequency bass sounds, it makes them both similar technically. However, both audio connections are still different from each other as there is one thing that sets them apart, which is crucial in telling them apart. That one thing is about the amount of information carried over each connection.

Audio Signals

As mentioned earlier, both Sub Out and LFE audio connections are made to carry bass signals from the audio source to an audio system’s receiver unit. High frequencies are filtered and left behind during transfer, thus only carrying the bass frequencies during transfer. However, this is where the differences between the two connections come into play, as one carries more information than the other.

As for the information carried by either connection, the exact one would be the type of elements of the bass signal each connection would carry and the amount it would carry. Do take note that the content produced and transferred in an LFE channel connection is way different when being compared to the content being transferred by a Sub Out connection.

From Totem Acoustic

For a Sub Out connection, it can carry either some specific amount of information or all of it at one given time, mostly bass sound information from an audio signal coming from the main source.

However, that isn’t the case with an LFE channel connection as it is instead designed to supplement the total amount of bass information present in an audio signal coming from the source.

The result of that particular design adds more bass information in an audio signal being transferred, giving more weight and depths to many movie sound effects such as explosions and guns being fired.

To put it simply (and as mentioned earlier), LFE channel connections are meant for a home theater system for watching movies, while Sub Out is better used for listening to audio music sources.

Can LFE be Present on Subwoofers?

That might sound confusing, but yes, there are subwoofers that have various audio input ports such as RCA channels and LFE channels. LFE channel ports present in subwoofer units are called LFE Input.

What is an LFE Input, you might ask? Well, it is an input port that connects your subwoofer unit to your audio system’s receiver unit by combining both left and right channels of your receiver unit. The commonly used cable for that kind of connection would be through the usage of a single LFE-RCA cable.

However, do take note that not all subwoofer units being made and sold in the market today can support an LFE channel connection inside them (i.e. not having the correct port for an LFE channel connection).

Instead, the usage of an RCA channel connection or a wired stereo connection is used to connect those subwoofers to a home theater system’s main unit and receiver unit. Do take note that an RCA channel connection will combine both left and right audio channels and will instead send separate signals to each.

Can You Use LFE on Subwoofers?

The simple answer to that is a yes, as long as that type of connection is supported by your subwoofer unit. It is a given that you shouldn’t use an LFE channel connection to a subwoofer unit that doesn’t support it unless you want to intentionally damage it. Using an LFE channel connection for your home theater system will greatly enhance the sound effects coming from the multimedia source you are playing with the system itself.

Do remember that LFE channels will enhance the total amount of bass content of the sound being played in your system. Pair it along with subwoofers that are primarily designed to emit low-frequency sounds and it will make your multimedia viewing experience many times better without it.

What type of cable is used for subwoofers - theGuruChoice
From Guru Choice

You can even recreate the sound feeling of a true cinema experience by using surround sound channels like the previously mentioned 5.1 and 7.1, even enhancing your viewing experience even more than ever.

LFE on subwoofers will result in the produced audio quality being highly accurate. It will also help relieve the audio burden experienced by other channels when transferring sound. To achieve high accuracy on the audio quality, it is best to adjust the levels of the speaker units being used to their large or full-range level. Doing so will allow your speaker units to freely output the full range of signals coming from an LFE channel connection transmission.

Can You Connect a Receiver’s Sub Out to a Subwoofer’s LFE Input?

Now, you might be wondering if it is possible to connect a Sub Out of a receiver unit to the LFE input of a subwoofer unit. The answer to that question is yes, but you must connect the Sub Out ports to an LFE input via the usage of a single audio cable with RCA on both of its ends. Once correctly done, the Sub Out port will send out low audio signals that have been filtered (inducing LFE information) to your subwoofer.

Additionally, you can also connect amplifier units in the same way you can connect to subwoofer units. The reason why amplifier units can be connected in the same way is that most of them have built-in Sub Out connection ports that can support LFE channel connections. 

Final Thoughts

As mentioned earlier, both Sub Out and LFE channel connections are technically the same when it comes to transferring sound bass information. However, they differ in function as the former focuses more on the transfer of low-frequency sound bass information, while the other enhances the amount of it by adding more during the transfer process.

Both can be connected to each other and audio devices that support it such as the receiver units of a home theater system and even standalone amplifier units. However, both can now be considered old technology as new and modern technology can do their roles without relying on their connections alone anymore unless you are using older tech.

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