JBL GTO939 | Car Speakers | Review

One of the most thrilling experiences and probably the best for most is getting to have a car sound system that works just as you desire it to. Truth be told, it won’t be easy at all for you to get such and you’ll have to do a lot of searching to get the best.

To save you both the time and the hassle it would take for you to find the best, we’ve narrowed down your options to only a single coaxial speaker- the JBL GTO939.

If you are looking for a quick upgrade to your current car audio system, then this is definitely the speaker for you. from the installation to the listening experience, the JBL GTO939 will definitely give you a whole new experience.

That being said, how about we delve into taking a look at what this set of coaxial speakers has got in store for us?

JBL GTO939 Premium 6 x 9 Inches Co-Axial Speaker Review

Here are some of the features the JBL GTO939 packs under the hood that’ll definitely blow your mind…

Amazingly easy to set things up.

First off, we can both agree to the fact that one of the most frustrating things when it comes to upgrading the car audio systems can be the installation procedure. The installation package of this car speaker includes a pair of 6 x 9-inch coaxial speakers.

In most cases, the coaxial speakers will perfectly replace the factory installed speakers. If you’re lucky enough, all you may be needed to do is unscrew the mounting bracket of the factory speakers detach the wiring from the stock installed speaker. This should be followed by unmounting the factory installed speaker and replacing it with the JBL GTO939 car speaker. This can be done in a jiffy.

Regarding the installation location you prefer, you may be needed to do much or less work but as we all do know, the easiest way to go would simply be to replace the stock speakers with these ones.

If you want to install these in a new location other than where the stock unit was, you’ll definitely have a lot more to do. Something else that you should have in mind is that regarding the type of vehicle you have, the level of installation complexity you’ll experience will vary. As a matter of fact, you may or may not have to do some extra drilling, filling and a few other modifications to get it to fit. The best casescenario is that it’ll perfectly replace the stock unit even without the mounting brackets which we will look at in a while.


Unlike the coaxial speaker systems that have got the different drivers handled separately, this one has got all the tweeter and the subwoofer being handled by one driver. You’ll be getting a single set with two speakers which should be enough to give you a way better experience that you did get from the factory speakers.

A Dedicated Crossover

Here’s something you won’t get in a full range speaker system every day- a dedicated crossover. Crossovers are normally popular with the component speaker systems and it is one of the advantages they have over most coaxial speakers.

If you want something that’ll give you a kick for your buck, then you should definitely consider getting yourself this pair since each of them comes with a 12dB/octave high-quality crossover component.

This just works in the similar way the crossovers in the component speakers do- directing the high frequencies to the tweeters and the low frequencies to the woofer. If you install the speakers in a perfect location, you’ll definitely create an outstanding soundstage and get the most out of the isolated frequencies.

A piece of advice:

Considering this is a coaxial speaker system with a built-in crossover, it is simply designed to work in the best way possible by the manufacturers. I, therefore, strongly recommend that you don’t consider doing modifications by addition of an external crossover since this will simply interfere with the speaker’s internal wiring system.

The Power Handling.

The power handling capabilities are one of the most important things in a car speaker since it plays quite a big role when it comes to the overall sound quality.

Let’s have a look at how good the JBL GTO939 really is, shall we?

If you know even the tiniest bit of speaker power then you've probably heard of the root mean square. The Root Mean Square is simply the continuous amount of power with which the speakers operate. As a matter of fact, the greater the RMS is, the better off you are.

In our case, the JBL GTO939 has got an outstanding 200 watts of RMS which also makes it one of the best in the market. This simply means that you’ll be getting the best bass since the bass quality is normally determined by how high the RMS power is.

Besides the RMS, there is also the peak power. Whereas the RMS is the continuous power level with which the speakers are run, peak power, on the other hand, is a power level greater than the RMS that the speakers are allowed to achieve for only a few seconds.

The rule of thumb is that the peak power is double the RMS but this not always the case since, for the JBL GTO939, the peak is 300 watts. This, as it turns out is quite ideal when it comes to delivering both outstanding highs and lows.

I greatly advise that for the best experience, especially if you are upgrading your whole car sound system, you, first of all, purchase the speakers. Having done so, go ahead and match these speakers to a suitable head unit. This way, you'll get the most out of the speakers.


You should be keen to observe the RMS range since if you happen to exceed this, you may damage the speaker and have to worry about repairs or worse enough, a replacement. Simply put, as much as you may be having one of the best with you, utmost maintenance is necessary to keep it this way.

If you happen to exceed the RMS threshold for even a few minutes, you’ll be overloading the speaker which could in the end result to sound distortion, lagging or even worse damaging the speaker.

The tweeters- no other better way to enjoy ultimate clarity on the highs

We’ve already seen that for the coaxial speakers, the tweeters and the woofer are handled by the same driver, right? How about we now have a look at each of these individual drivers starting with the tweeters?

Watch The Video for testing sound quality

The tweeters are normally dedicated to handling the high frequencies. in most cases, these frequencies are greater than 2000 Hertz. Whereas all tweeters may be able to produce all the high frequencies that are input to them from the head unit, the quality normally varies which is where the material construction of the tweeters comes in.

The best cone material you can get on a tweeter is normally soft hence when it comes to the production of the clear highs, the sound won’t be too ear piercing.

For our tweeters, you’ll be getting the edge-driven soft dome tweeter design. This allows for the production of high quality and clear highs.

The soft-dome tweeter design increases the power handling threshold of the tweeter and at the same time reduces sound distortion at high frequencies. the edge-driven feature of the tweeters also allows for better dispersion and allow for a lower crossover frequency for better imaging.

Besides the dome on the tweeters, there is also the voice coil. This is oversized which makes it quite convenient when it comes to heat dissipation.

The bigger the surface area the voice coil has the better off are the chances of your tweeters lasting longer since there will ideal heat dissipation. If the voice coil becomes overheated, the odds of it getting damaged are quite high and as far as repairs go, it’s not easy to repair one and you, in most cases may be forced to purchase a new sound system.

Dual-level tweeter volume adjustment-customize your highs.

Other than just having a soft dome backed up with an oversized voice coil, another mind-blowing feature on the JBL GTO939 is the adjustable tweeter volume.

This feature is meant to compensate for the low and the off-axis mounting position or the road noise. You can set the output of the tweeter from 0 to +3 decibels.

The Woofer- look no further for the best bass.

Besides the tweeters, a full range car speaker has got a woofer. The woofer simply determines how good the bass quality is going to be by converting the low frequencies from the head unit to the sound.

Testing  bass

For the best bass quality, you should strive to get a woofer whose cone is rigid and at the same time flexible. This way, you'll not have to worry about the cone coming apart and at the same time, it will have an optimal motion for the production of high-quality sound.

In the JBL GTO939, you’ll be having a carbon-injected plus one cone. As compared to other cones, this one is slightly larger in size. This means that they have a greater range of motion which in turn moves more air. In the long run, you end up with an above-average bass quality.

Vented magnet assemblies.

Keeping the voice coil cool is probably the best way to ensure that you get to enjoy your set of speakers for as long as possible. Normally, besides the speakers heating up from the electricity passing through them, the surrounding environment does contribute to the buildup of heat within them.

To take care of this, JBL included a vented magnet assembly. This helps keep the magnet cool which in turn increases the reliability of the speakers from greater power handling. At the same time, this eliminates power compression which could distort the speakers sound.

A carbon-composite nonmagnetic frame

Here’s something you’ll not be getting every day- a carbon composite non-magnetic frame. This is used in the JBL GTO939 so as to resist warping even when the speakers are mounted on an uneven surface. 

This is unlike anything you’ll find in most speakers as the non-magnetic carbon composite aids in controlling the magnet’s energy and deliver it to the voice coil instead of wasting it as heat.

To make things even more interesting, the plastic does not resonate hence contributing highly to the high levels of accurate sound you’ll be enjoying

The sensitivity.

Besides the power handling, something else that determines the quality of sound you get from your speakers is their sensitivity.

For the JBL GTO939, you get an outstanding 94 decibels of sensitivity.

Something you need to know about sensitivity is that it works hand in hand with the power capabilities of a car speaker. Normally, the higher the sensitivity, the better off you are. Higher sensitivity levels allow you to play your music at higher volumes at an outstanding quality and simultaneously use lower amounts of power.

The average amount of sensitivity for a coaxial speaker is around 88dB. If you’re lucky enough to get anything above this as is the case for the JBL GTO939, then you should definitely settle for those speakers.

Mounting brackets.

Along with the pair of JBL speakers, you’ll be getting mounting brackets for each of these. This simply allows you to have the speakers fit in place and at the same time the mounting brackets protect the speakers from any physical damage.

The mounting brackets that come with the JBL GTO939 will prove quite useful but on the downside, they may not fit in place of the stock speaker installation location. In such a case, you’ll need to drill the screw holes yourself to have them fit perfectly.

True 4-ohm impedance.

The impedance rating on a car speaker normally has a great impact on the power handling of the speaker. Think of the impedance and power as being inversely proportional.

The greater the impedance, the lower the amount of electricity it allows to flow through to the speakers but the lower the impedance the higher the amount of electricity it allows to flow through from the head unit to the car speakers

With 4 ohms on the impedance of our speakers, you'll be getting quite an outstanding performance considering it has got an RMS of 200W. this level of impedance makes use of every watt that comes from your head unit and also compensates for the substandard speaker wiring you may get in most cars.

Simply put, at the end of the day the 4-ohm impedance is a great boost to the overall sound of your vehicle’s audio system.

Outstanding frequency response

Finally, let’s take a look at how the frequency response on the JBL GTO939 really is. First off, you should know that the frequency response is the range of frequency that is audible to the human ear and this just is anything between 20Hz to 20kHz. Even so, it’s quite seldom to get a coaxial speaker that’ll observe this.

Too low a frequency for the bass is rarely used in music and most coaxial speakers will only function at 80Hz and above. For our JBL speakers, the frequency response is between 46Hz and 21kHz. This is enough to be able to handle both the highs and the lows in all music genres conveniently.


  • Vented magnetic assemblies to aid in keeping the voice coil as cool as possible.
  • High sensitivity of 94 decibels to provide an outstanding sound without overdriving the audio system
  • Dual level tweeter adjustment to help suit your listening preferences.
  • Larger carbon-injected plus one cone that move more air for an above-average bass.


  • Despite the sound quality being quite outstanding, installing the grilles may be quite difficult since there might be some extra drilling to do to get them to fit

Frequently asked questions

Q: does the bass hold up at a high volume?

A: yes, though if you want a really good bass you should consider getting subwoofers.

Q: what is the RMS rating on these speakers?

A: this is 200W continuous power and 300 watts for the peak

Q: what is the ohm rating on the speakers?

A: 4 ohms

Final Verdict

Coming to the end of the JBL GTO939 Premium 6 x 9 Inches Co-Axial speaker review, we can both agree that there’s a lot you’ll be getting from this pair of speakers. From the construction design to the power handling, it will definitely be worth every dime.

Just like the other components in your audio system, proper maintenance precautions are needed for these speakers. Don't, for instance, exceed the power handling capabilities.

As far as setting it up is concerned, the user manual comes along with the package and so does a pair of grilles each for the two individual speakers. In overall, you should definitely try it out if you’re looking for an upgrade; all the best!


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