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JL Audio JX400/4D 4-channel 70 watt RMS x 4 Car Amplifier Review

James Benchman
Published on
by James Benchman

If you ask a number of car audio builders which brand is among the most trusted in the affordable range, most of them will say JL Audio. Building that kind of trust with your user base definitely doesn’t happen overnight. On the contrary, JL Audio has earned every bit of respect they get these days.

Models like the JL JX 1000 D and the JL JX 500 by 1, are both sought after units. The amp we are going to review today is another solid product, The JL JX 4oo/4D

JL Audio JX400/4D is among the more interesting models in JL Audio’s current offer. As you are about to see for yourself, this thing is a gift that keeps on giving, even though it sits well at the edge of the entry-level part of the market.

This is the very same segment where you don’t expect to see too many features nor high-quality components, yet surprises are possible where you least expect them

  • It is portable and easy to install
  • Emitts little heat
  • Powerful yet affordable
  • Build is not as solid as other amps

A Closer Look at the JL Audio JX400/4D (Review)

Right around 400 Watts RMS is the output sweet spot for most people. Not everyone needs a kilowatt amp in their trunk, while a lot of users actually appreciate having their trunk space preserved as much as possible. In this regard, JL Audio JX400/4D is hitting the nail on the head. The amp brings the type of performance in a package  that is simply the perfect size.

You can place it just about anywhere you want, and that is exactly why it’s among the most popular models in JL Audio’s lineup at the moment.

Features of the JX 400/4D:

One quick glance at the JL Audio JX400/4D will make you wonder whether or not this thing could fit on a bike. That’s how small it is. In terms of design, you are looking at more or less standard JL Audio aesthetics which they apply to all of their affordable amps.

Everything about this model is kept simple. Connectors are all screw-in type, so cable termination will take some elbow grease. However, installing the amp itself is pretty easy thanks to its user-friendly form factor and well-defined mounting brackets.

JL Audio JX400/4D is rated for 400 Watts RMS. It’s a 4 channel amp that delivers some 70 Watts per channel at 4 Ohms or 100 Watts per channel at 2 Ohms. Additionally, you can bridge it to get 200 Watts on two channels at 4 Ohms.

Both of these metrics are for 14.4V. On 12.5V, the values are reduced by 20 Watts. All things considered, there is some serious versatility in these figures. JX400/4D is capable of providing just enough juice for a decent system consisting of two drivers and one woofer.

Frequency response range goes from 20 Hz to 20 kHz. In terms of filters, you have a slightly different solution. Instead of having both the low pass and high pass filter, there is a 12dB / octave filter that can be configured to act as either of these. Variable cut-off frequency range goes from 50 Hz to 200 Hz, and this configuration is pretty efficient.

The power supply JL Audio went with is a rather crude but reliable MOSFET unit that delivers the necessary juice where it is needed the most. With that said, this amp comes with wiring at all so expect to get a fuse among for it, among other things.

How does the JL JX 400/4 D Perform?

Who would have thought that a small box such as this one can deliver a decent enough performance to be categorized as high quality? The sound is pretty good considering both the size and the price of the unit, and there is plenty of volume and power no matter which channel configuration you go for.

With that said, pairing this unit with JL Audio’s JX monoblock creates a well-rounded system that might be a bit more efficient and providing you with a full frequency range saturation. Either way, there’s some good performance packed into this little amp.

As expected, you can use this unit in combination with most OEM heads thanks to low-level RCA inputs.

Heat is always something to think about when you’re dealing with smaller amps. Due to their limited form factor, heat syncs which are often found in these models are going to have limited effect on dissipating heat.

In the case of JL Audio JX400/4D, you have a highly efficient Class D amp that doesn’t really produce that much excess heat, at least not with this output levels. You can comfortably install the JL Audio JX400/4D even in less standard places and not worry about it overheating.

If we were to describe the tone this puppy offers, the world well-rounded certainly comes to mind. We are looking at a powerful punch with strongly defined basses backed up by a punchy section of middles and a healthy chunk of bright treble frequencies to round up the whole sonic attack. The product also packs a nice little roar if you’re looking to rock out, but mostly keeps things balanced and nicely rounded.

Is this JL Amp Worth the Price?

Small, compact amps are becoming the new battleground of the industry. There’s quite a selection at this moment, but like the rest of the JL Audio amplifiers , the JL Audio JX400/4D is definitely a great product.

Simplicity is often times the key to success, and this amp is a good example of that in practice. Those who are just looking to boost their factory stereo system, or those who want to get started in this hobby, will find the JX400/4D to be a great value for the money. For the listed price, we really can’t think of a whole lot of better devices to purchase.

This is good stuff and we thoroughly recommend it. A thumbs up from here!

  • It is portable and easy to install
  • Emitts little heat
  • Powerful yet affordable
  • Build is not as solid as other amps

About James Benchman
James Benchman
James is an Automotive Mechanic with over 20 years experience and 300+ car repairs. He is an expert with cars and has worked with different models from the biggest brands. James is a Mechanic , Husband , Father of 3 , and head of content at Caraudiologic. Learn more about us
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