Why You Need an Amp to Power a Subwoofer

What Are Subwoofers?

Subwoofers are speaker drivers that can produce low-frequency audio. Subwoofers are usually mounted in a speaker enclosure that is called a cabinet. Cabinets are typically made from wood. The enclosure is really to protect the tech from air pressure and to avoid deformation.

Subwoofers have multiple design aspects that help their performance. An example of a design aspect that the cabinet of the subwoofers has is a bass reflex. This is usually the hollow tube that you see on speakers. That hollow tube acts as a hole or vent that allows the sound from the rear side of the diaphragm to increase the system’s efficiency when it has to produce low frequencies.

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Another example is passive radiator speakers. These are the dome-like structure that you see in speakers. The dome-like structure is actually called cones. This design is beneficial for compact audio systems where applying a vent is difficult or impossible. There are many more cabinet designs such as the acoustic suspension, infinite baffle, horn-loaded, tapped horn, transmission line, bandpass, or isobaric.

All represent unique trade-offs. The efficiency, sound quality, cabinet size, and cost are all factors that are considered when choosing a design for a subwoofer.

Subwoofers are made to produce audio frequencies known as bass and sub-bass. Both bass and sub-bass are low frequencies, and the typical range that a subwoofer that is sold for recreational purposes produces is about 20hz to 200hz. Higher quality subwoofers for professional live sound, on the other hand, produces lower than 100hz.

THX-certified systems can produce about lower than 80hz. George Lucas founds THX. Some movie theatres, screening rooms, gaming consoles, car audio systems, computer speakers, and video games utilize this system. So if you see audio systems that are THX certified, you can expect high-quality audio performance.

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What Subwoofer Should You Get?

The power and the driver size are important factors to consider. The first thing that you have to know about power is that higher-powered subwoofers are not louder than low-powered models. The power does not dictate the loudness; that’s what the volume is for! So a 1000-watt subwoofer is not louder than a 100-watt subwoofer.

The watt rating is just a rough guide on the output it can produce. Here’s a tip, don’t be scared of getting a 1000-watt subwoofer. They perform very well even in a relatively regular-sized room. In fact, a 100-watt subwoofer may not be enough since we are talking about subwoofers and not loudspeakers. 300, 500, and higher watts are a good range to choose from.

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Another important thing to factor in is size. The size of the driver inside usually dictates the size of the cabinet. So a subwoofer with a 12-inch driver has a bigger cabinet than a subwoofer with an 8-inch driver. It was mentioned before that the purpose of subwoofers is to create bass.

Bass waves are really long, so there should be sufficient space in the cabinet behind the driver. Because the driver has to perform heavily to create waves in volumes that we can hear, the bigger the driver, the better. So 12 inches is a good size to get.

There are multiple sizes to choose from. For example, you may encounter two 6 inch drivers. In that case, a single 12 inch is still better. However, multiple subwoofers are still good and useful because you get to improve the sound experience by setting it in different locations in a room so it is more spread out.

If you have a smaller subwoofer, a good way to counter that is to get a subwoofer with a higher power.

Voice coil also factors in when choosing a subwoofer. There are two:

1. Single Voice Coil or SVC – This generally only supports one specific ohms rating, so it is not as versatile as the DVC.
2. Double/Dual Voice Coil or DVC – This gives you more wiring options to connect your subs with amps allowing you to hit the correct impedance loads you need for the best sound possible.

How Will You Know if You Need an Amplifier With Your Subwoofer?

Some subwoofers come with loudspeakers, and some subwoofers have built-in amplifiers. But, definitely, subwoofers are never used alone. This is because subwoofers are just used to give loudspeakers a low-frequency range—loudspeakers, on the other hand, cover high-frequency bands.

A good thing to note is that an external amplifier usually powers passive subwoofers, and active subwoofers usually include a built-in amplifier. So when buying equipment really research about it. Find out the important details and specs.

So what do you need? A passive or an active subwoofer? Here is a short guide to help you find out!

Most of the time, for cheaper or entry-level audio systems bundles or kits, what you get is a passive subwoofer. A drawback that passive subwoofers have is that they might not give you the quality of an active subwoofer. Although, it is a good option because it is relatively more affordable and is more budget-friendly.

If you’re only buying for casual enjoyment, a passive subwoofer might be enough. Still, if you aim for a surround sound experience or generally just a really high-quality audio experience, active subwoofers might be for you. Active subwoofers are perfect for professional use or if you want to build a theater room at home.

You can even elevate the sound quality by adding an external amplifier. Although even without the additional extended external amplifier, an active woofer performs really well. It can also help save you real estate if you only have limited space for your audio system since there is no need for an external amp.

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All About Amplifiers!

An amplifier is a piece of audio equipment that increases the power of a signal that is connected to its input terminal. Hence, the output that you get from using an amplifier is a greater and balanced signal. Its gain measures the amp’s power output. The gain is the ability to increase the signal from the input to the output by adding energy converted from a power supply.

If the explanation is a little too complicated… here’s a simpler explanation. The amplifier receives a signal from the source connected to it, and these may be your mobile phones, turntable, CD, DVD, media players, etc. Then it replicates the signal it receives larger and greater for the output to produce.

Usually, the output is speakers. As you already know, from passive and active subwoofers, an amplifier can be a separate piece or is part of another piece. To control the output you’re getting from your amplifier, you will need a potentiometer. Using the potentiometer, you can control the volume.

This is because the potentiometer allows the user to control the amount of current that goes to the speakers, which directly affects the overall volume level. Amps may differ in their shape and sizes, but it all really works the same way… to amplify the sound that comes out of your speakers.

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What to Look for in an Amplifier?

When choosing an amplifier, there are five important factors to check out:

1. Power Output

This defines how loud you can turn up the volume. If you have large and high-quality speakers, the more power you want. However, for average listening and casual purposes, you don’t need lit. 10W is just fine and is already loud enough for an average user.

Although if you need audio for large parties, 100W may be what you need. So it all really boils down to what you’ll use it for. Speaker sensitivity also factors into this.

So also make sure to check the specs of the speaker you have or planning to buy. The average speaker sensitivity rating is 87 dB to 88 dB. 90 dB is considered excellent. The higher the sensitivity rating, the louder your speaker is.

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What Is a Good Signal to Noise Ratio for an Amplifier?

2. THD + N (Total Harmonic Distortion + Noise)

This is a measure of how much effect the amplifier has on the sound output it produces. What you’re looking for is that you want the output from the amplifier to be as close to the original sound.

However, your speakers will still have the biggest effect on the sound or the audio experience. That is why you must get an amplifier that works compatibly well with your speaker. For THD + N, the lower numbers are better! 1k is better than 20k, for example.

3. Signal to Noise Ratio or SNR

Amplifiers tend to generate a very faint noise. This is from the electrons whizzing around inside. Good amplifiers make this noise almost impossible to hear, and that’s what you want when looking for an amplifier.

You want the sound to be more dominant than the noise the amplifier generates. The bigger the number, the better the amplifier is in hiding the noise.

4. Crosstalk

This is the ability of the amplifier to differentiate what should come out to the left or what should come out to the right. Good quality amplifiers can split apart signals to travel to the output where it’s meant to be. The more crosstalk there is the more unwanted interference between left and right output.

5. Inputs and Connections

Will it work with the device you want to use it with? There are different connections for different purposes. For example, you’ll need 3.5mm cables for Mobile phones or USB for computers and laptops.

So when you look for an amplifier, these are factors that you may want to ask about.

Subwoofer and Amplifier Matching

Now that you know about subwoofers and amplifiers individually, time to learn how to use both together for a better sound experience!

Just a recap, if you have a passive subwoofer, you will need an external amplifier to improve the audio quality. Still, if you have an active sub, you don’t necessarily need an external amp since it already has an amplifier built in the box. Still, you can always add an external amp to improve the quality further.

Let us start learning about getting the right amplifier for your subwoofer or getting the right subwoofer for your amplifier!

First thing’s first, the amplifier capabilities need to match the subwoofer’s specs. In technical terms, the watts RMS and the ohms have to match.

Subwoofers for Amps

If you already have an amplifier, which subwoofer should you get? The first information you need is what your amp can do? What is the RMS rating of your amp at different loads? Your amp’s power output is expressed in watts RMS. Next, you also have to know the power output you would like to get because the load impedance of that rating will be what your sub’s total impedance be.

There is actually a chart that you can use for this that can help you as a guide. The number of subs you want or also need factors in. Lastly, it is important to get a subwoofer for both SVC (single voice coil) or DVC (double voice coil). Refer to the heading what to look for in a subwoofer for more info about SVC and DVC. Basically, it’s for versatility.

So remember, the secret to having your audio gear produce good bass is the have an evenly matched subwoofer and amp that works properly together.

External Amp for Subwoofers

Now, if you already have a subwoofer, but you need to add an amplifier. If you have multiple subs, the first thing to do is to check if they all have the same coil type, whether SVC or DVC and impedance. They must be all the same so that the power will be divided equally between all subs. But, again, you don’t want some to be overpowered or some underpowered.

The first information you need is the answer to how much power can your subwoofer produce? This is the watts RMS rating of the subwoofer that you have. If you have multiple subs, you will need to multiply the subs you have by the RMS rating of each to get the total RMS rating.

Next, you need to know the total impedance that the subs can be wired together from.

Once you have information on both steps, you can now pick an amp to handle those watts and ohms. Here is a rough guide that can hopefully help you choose the right amplifier for your setup

• 1 SVC 2-ohms can only have 2 ohms of impedance
• 1 SVC 4-ohms can only have 4 ohms of impedance
• 1 DVC 2-ohms can have 1 ohm or 4 ohms of impedance
• 1 DVC 4-ohms can have 2 ohms or 8 ohms of impedance
• 2 SVC 2-ohms can have 1 ohm or 4 ohms of impedance
• 2 SVC 4-ohms can have 2 ohms or 8 ohms of impedance
• 2 DVC 2-ohms can have 2 ohms or 8 ohms of impedance
• 2 DVC 4-ohms can have 1 ohm or 4 ohms of impedance
• 3 SVC 2-ohms can have 6 ohms of impedance
• 3 SVC 4-ohms can have 1.3 ohms of impedance
• 3 DVC 2-ohms can have 1.3 ohms or 3 ohms of impedance
• 3 DVC 4-ohms can have 2.7 ohms or 6 ohms of impedance
• 4 SVC 2-ohms can have 2 ohms or 8 ohms of impedance
• 4 SVC 4-ohms can have 1 ohm or 4 ohms of impedance
• 4 DVC 2-ohms can have 1 ohm or 4 ohms of impedance
• 4 DVC 4-ohms can have 2 ohms or 8 ohms of impedance

The Best Amplifier in the Market Right Now

Marantz PM6007

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Marantz PM6007 Specs

Power Output (8 / 4 Ohm RMS):	45 W / 60 W
Frequency response:	10 Hz – 70 kHz
Total Harmonic Distortion:	0.08%
Damping Factor:	100
Input Sensitivity: MM:	2.2 mV / 47 kOhm
Input Sensitivity: MC:	No
Signal to Noise Ratio: MM/MC	83 dB / No
Input Sensitivity: High level	200 mV / 20 kOhm
Input Sensitivity: Balanced High level	No
Signal to Noise Ratio: High level	102dB(2V input)
Input Sensitivity: Power Amp Direct IN	No
Signal to Noise Ratio: Power Amp Direct IN	No

This is a 45W per channel amp. You can use either coaxial and optical cable for digital inputs. It also supports headphone output. Overall, this amp is a clear and punchy performer, has broad connectivity options, has a solid built. The only con is that it is not Bluetooth enabled and no connection for USB.

Cambridge Audio CXA81

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Cambridge Audio CXA81 Specs

Power Output (8 / 4 Ohm RMS):	80W RMS into 8 Ohms, 120W RMS into 4 Ohms
Frequency response:	<5Hz– 60kHz +/-1dB
Analogue Audio Inputs:	1x balanced XLR, 4 x RCA
Digital Audio Inputs:	1 x S/PDIF coaxial, 2 x TOSLINK optical, 1 x USB audio, Bluetooth (integrated)
Compatibility:	TOSLINK optical: 16/24bit 32-96kHz PCM only, S/PDIF coaxial: 16/24bit 32-192kHz PCM only, USB: audio profile 1.0/2.0 (default 2.0), up to 32bit 384kHz PCM, up to DSD256 or DoP256, Bluetooth: 4.2 A2DP/AVRCP supporting up to aptX HD (24bit 48kHz)
Bluetooth Aptx Hd Receiver Built-in	Yes
Roon Tested	Yes
Outputs	Speakers A+B, 3.5mm headphone, Preamp Output, Subwoofer Output
Remote Control:	Yes
Max Power Consumption:	750W
Standby Power Consumption:	<0.5W
Dimensions (H X W X D):	115 x 430 x 341mm (4.5 x 16.9 x 13.4”)
Weight:	8.7kg (19.1lbs)

This amp has a power of 80W per channel. You can use S/PDIF coaxial and Toslink for digital inputs. Unlike the Marantz PM6007, it is Bluetooth enabled and has USB connectivity. It has an aptX HD receiver built-in for Bluetooth.

It also allows headphone output. The only con, but it isn’t really a deal-breaker, is that it doesn’t have a remote control. But overall, it is still one of the best. The price may be a little bit too steep if you’re going on a budget.

Rega io

Rega io Specs

Power Output:	30 W per channel into 8 Ω
Power Consumption:	135 W
Inputs:	1 x Phono input, 2 x Line inputs
Frequency Response:	Phono: 15 Hz to 40 kHz (-3 dB points) / 27 Hz to 20.5 kHz (-1 dB points)
Remote Control:	Mini
Max Power Consumption:	135 W @ 230 V / 220 V / 115 V / 100 V into the rated load of 8 O
Dimensions (H X W X D):	7.1″ x 11.4″ x 2.7″
Weight:	2.9 kg

Power is 30W. Doesn’t provide Bluetooth and USB connectivity. Also, no digital input. However, it does allow headphone output. It also has a remote control included. All in all, it produces detailed, rhythmic, and fun sound, and it has a good headphone output. Good enough for those looking for an amp on the cheaper side.

Naim Nait XS 3

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Naim Nait XS 3 Specs

Power Consumption (max.):	350VA
Mains Supply:	115V, 230V; 50 or 60Hz
Power Consumption (quiescent):	16VA
Supplied With:	NARCOM-5 Remote Control, Mains Lead, Link Plug and Safety Manual
Audio Inputs MM Phono Input:	via RCA, 47k parallel 470pF input impedance, suitable for 5mV cartridges
Line Level Inputs:	130mV sensitivity, 47k input impedance, suitable for 2V
Audio Outputs:	DIN Socket
Speaker Outputs:	70W per channel into 8 ohms (4mm sockets), 100W per channel into 4 ohms
Remote Input:	1 x 3.5mm Jack on rear
Max Power Consumption:	350VA
Mains Supply:	115V, 230V; 50 or 60Hz
Dimensions (H X W X D):	70 x 432 x 314 mm
Weight:	8.5 kg

Power is 70W. Zero digital inputs available and no USB or Bluetooth. Headphone output available. This amplifier has a dynamic sound.

Cambridge Audio CXA61

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Cambridge Audio CXA61 Specs

Power Output:	60W RMS into 8 Ohms, 90W RMS into 4 Ohms
Frequency response:	<5Hz– 60kHz +/-1dB
Analogue Audio Inputs:	4 x RCA, 1 x 3.5mm MP3 input (front panel)
Digital Audio Inputs:	1 x S/PDIF coaxial, 2 x TOSLINK optical, 1 x USB audio, Bluetooth (integrated)
Compatibility:	TOSLINK optical: 16/24bit 32-96kHz PCM only, S/PDIF coaxial: 16/24bit 32-192kHz PCM only, USB: audio profile 1.0/2.0 (default 2.0), up to 32bit 384kHz PCM, up to DSD256 or DoP256, Bluetooth: 4.2 A2DP/AVRCP supporting up to aptX HD (24bit 48kHz)
Bluetooth Aptx Hd Receiver Built-in	Yes
Roon Tested	Yes
Outputs	Speakers A+B, 3.5mm Headphone, Preamp Output, Subwoofer Output
Remote Control:	Yes
Max Power Consumption:	600W
Standby Power Consumption:	<0.5W
Dimensions (H X W X D):	115 x 430 x 341mm (4.5 x 16.9 x 13.4”)
Weight:	8.3kg (18.3lbs)

This is a 60W per channel amplifier. You can use S/PDIF coaxial and Toslink for digital inputs. It has USB and Bluetooth connectivity, a headphone output, and a few hundred bucks cheaper than the Cambridge Audio CXA81. Most of all, it has detailed and dynamic audio and great build quality.

Rega Brio

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Rega Brio Specs

Power Output:	50 W into 8 Ω
Power Consumption:	195 W
Inputs:	1 x Phono input, 4 x Line inputs
Frequency Response:	Phono: 15Hz – 40kHz (-3dB) / 27Hz – 20.5kHz (-1dB)
Remote Control:	Yes
Max Power Consumption:	195 Watts at 115V into the rated load of 😯
Dimensions (H X W X D):	216 x 78 x 345 mm
Weight:	5.1 kg

Power is 50W. Just like the Rega io, it doesn’t provide Bluetooth and USB connectivity. Also, no digital input. However, it does allow headphone output. It also has a remote control included. Still, the quality is amazing, detailed, and dynamic. Agile and rhythmic.

Location and Positioning

Audio quality doesn’t directly rely on your equipment. It is also good to know how you can set it up to get the most out of your audio equipment. For example, putting your subwoofer against the wall may add a little a bit of volume, and putting it in a corner will add a little bit more.

All in all, to know the best placement for your subwoofer in the room, test it out. Sit in the place where you mostly do the listening. Have a family member or friend move it around to test the sound quality. Try it on several locations that are a few feet apart.

There is no exact ruling on where you should place your bass because it can depend on preferences but having it ear level is a good tip. Getting the most out of your system is important. You don’t want just one area in the room to get a ton of bass and another part to get next to nothing.