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400 Watt Speakers: What Size AMP? (Updated 2023 Guide)

Size Amp For 400 Watt Speakers

Picking out new speakers is fun.

But finding which AMP will suit them isn’t as exciting, is it?

That’s because all the fancy terms like watts and ohms can be intimidating.

However, fret not. I’m here to save the day. 

Continue reading to find out: 

  • My top-3 recommended amplifier brands. 
  • 5 quick steps to find the right AMP for you. 
  • What type of amplifier best suits 400-watt speakers. 
  • And this is just the beginning… 

What size AMP for 400 watt speakers?

A 600-watt AMP is best for 400-watt speakers. That’s because it’s better to have an amplifier that’s 50% more powerful than the speakers it needs to power. However, ensure that both devices have the same impedance (measured in ohms). Otherwise, 1 or both of them may fail. 

What does 400 watt AMP mean?

A 400-watt AMP means that your device can provide 400 watts of power to speakers. 

See, a watt is a measurement of electricity. 

And as amplifiers process sounds, they create an output that’s measured this way. 

With that said, speakers also have something called a power capacity.

And this measures how many watts your speakers can handle for long durations. 

“Do all speakers need an amplifier?”

No, they don’t. That’s because some models already have built-in AMPs. 

See, there are 2 types of speakers you can buy:

  1. Active.
  2. Passive. 

And simply put, active speakers already have built-in amplifiers. 

So you can just plug them into power, and they’ll immediately produce sound from your input.

Fun fact: Portable Bluetooth speakers are examples of these. 

On the other hand…

Passive speakers don’t have built-in AMPs. Thus, they need external amplifiers to function. 

“How do I know which type of speaker I have.”

It’s easy. Just check if your device has a power port. 

That’s because active speakers have it, and passive ones don’t. 

You might also be interested: 23 Easy Steps To Use Bluetooth Speakers Without WiFi

How do I match my speakers to my AMP?

To match your speakers to your AMP, you first need to know your speakers’ power capacity. That’s because your amplifier should have 50% more power than your speakers. 

After that, you should match both devices’ nominal impedance. So you won’t encounter any problems connecting them. 

Let’s get into the specifics with these…

5 quick steps to find the right AMP for your speakers:

#1: Know the power capacity of your speakers 

Now, I already mentioned what power capacity is earlier. 

But to give you a refresher, it’s how much electricity your speakers can work with safely. 

“Why do I need to know this value?”

Good question. You need to do so because… 

The power capacity will help you determine how many watts your amplifier needs.

That said, you can easily find this value in your speakers’ user manual or specs sheet.

So once you know the power capacity of your device (in watts), proceed to the next step. 

Note: In some models, this is called RMS or program watts

Warning: Don’t mistakenly use the value of the Peak power capacity. That’s because this refers to the highest power your speakers can handle in short periods. And you may damage your speakers if you use this value for the equation. 

#2: Know the nominal impedance of your speakers

Nominal impedance refers to:

How much your speakers can resist the current of electricity. 

That said, the lower the impedance is, the more “power hungry” your speakers are. 

Or, in other words, they’ll draw more electricity from your AMP.

And if you’re wondering why you need to know the impedance of your speakers…

That’s because, as mentioned earlier, your AMP and speakers must have the same ohms value. 

Otherwise, you may fry 1 of your audio devices.  

If you want to know more about nominal impedance, I recommend watching this video: 

Note: You can also find this value on your speakers’ user manual or specifications. 

#3: Calculate how many watts your AMP needs 

You already know your speakers’ power capacity, so this will be a very easy step.

That’s because all you need to do now is:

Multiple your speakers’ power capacity by 1.5

For example, if your speakers have 400 watts…

Simply multiply 400 x 1.5, then you’ll get 600.

Important: The product you’ll get is how much power your AMP needs to provide. So if you have 400-watt speakers, you should find an amplifier with 600 watts per channel.

Now, at this point, you’re probably thinking:

“Won’t a more powerful AMP destroy my speakers?”

But fret not, it won’t.

Let me explain. 

See, it’s a common misconception that…

Connecting an AMP to a speaker with lower watts will destroy the latter. 

But in reality, a more powerful amplifier (in moderation) is always the better choice. 

Here’s a scenario that can help you understand this easily: 

Imagine that your speakers are as heavy as their power capacity in kilograms. 

And your AMP is a weight-lifter that can easily carry its wattage converted to Kg. 

In this scenario, it’s not surprising that if the amplifier has higher watts than the speakers…

The former will have an easy time lifting the latter. 

On the other hand, if the AMP is weaker than the speakers’ power capacity…

The amplifier will need to work harder to lift the other device.

As you see, getting a more powerful AMP is much more efficient. 

That’s because it doesn’t need to work too hard to power your speakers.

Reminder: Never underpower your speakers. Or in other words, don’t use an AMP much weaker than your speakers’ power capacity. That’s because an overworked amplifier is likely to fail early. 

However, as mentioned earlier…

Your AMP’s watts should still be in moderation.

On that note, sticking to the calculation you made earlier is crucial.

Warning: You also shouldn’t use an amplifier that exceeds 150% of your speakers’ power capacity. That’s because overpowering your speakers can destroy or fry their components. 

You might also want to know: 3 Ways To Wire 4 Speakers To A 2-Channel Amp Diagram

#4: Find an AMP that matches your speakers’ ohms

As mentioned previously, your AMP and speakers must have the same impedance.

That’s because if your speakers’ ohms are any lower than what your AMP can handle…

You’ll risk frying your amplifier and also blowing out your speakers. 

“But what if my speakers have higher ohms than my AMP?”

In that case, your speakers won’t blow up.

However, you still won’t be able to get that much sound from your device.

And what good comes out of a speaker that can’t play loudly, right?

All that said, if your 400-watt speakers have 4 ohms… 

You should find a 600-watt AMP that can also handle the same impedance. 

#5: Enjoy your new audio set up

You can now enjoy your new speaker set up.

However, there are some pointers you need to mindful of. 

Important: Always start at the lowest volume when using your AMP and speakers. Then, gradually increase the gain as you see fit. 

Warning: Avoid using your AMP at more than 70% of its full volume capacity. Because this can blow up your speakers as your amplifier is more powerful. 

That said, just keep these in mind, and your audio devices will be safe from damages. 

Now, if you’re thinking: 

“I don’t have an AMP yet. Do you have any recommended amplifier brands?”

Then I’ll be glad to talk about the… 

Best 3 amplifier brands I’ve tried:

#1: Marantz

Marantz Amplifier

When it comes to audio devices…

You can rest assured that Marantz will deliver quality.

And, of course, that’s clearly shown by their amplifier models too. 

See, they have all kinds of AMPs, including those with the power capacity of:

And regardless of the model you pick, you can expect a high-end sound projection. 

#2: Cambridge

This is another brand that consistently produces top-quality audio devices like:

  • Speakers.
  • Amplifiers. 
  • Audio receivers.

And, trust me, Cambridge never disappoints.

See, I have their 2-channel amplifier with Bluetooth at home. 

And with its 120W, 4 ohms output…

I can easily connect it to my OSD Nero Bookshelf speakers

#3: Denon

“Listen to your favorite songs with impeccable precision.”

That’s how Denon introduces their devices.

And after years of using this brand…

I can confidently say that Denon stays true to its promises.

See, I’ve tried their PMA-600NE Stereo Integrated AMP before.

And despite its small build (around 17 x12x5 inches)…

It can provide enough power to a 50-watt speaker to play loudly throughout a whole room. 

So if you’re searching for amplifiers that cost less than $500… 

Don’t hesitate to check out Denon products.