JBL BassPro SL2 Under Seat Slim Subwoofer Review

[Hayabusa]

No matter what I did with the three controls, I could not get anything that was a mountain. That made setting levels hard but I used to the peak and measured distortion at "86 dBSPL:"

View attachment 452588
The right relative THD is normally set to 5%. That resulted in the graph showing nothing but lines to out the top. I had to set it to 100% to get what you see. Even at its optimal output of 10 Hz, distortion is 15% and rises to 60% at 45 Hz.

I am confused.. I see THD 40db down in the left graph which corresponds to 15% at the right side.
I think the scale is of by exactly a factor 10 to high!

 

[amirm]

That was a typo. I meant 100 Hz, not 10 Hz. Corrected the review.

 

[Hayabusa]

That was a typo. I meant 100 Hz, not 10 Hz. Corrected the review.

But still the scale of the right graph is wrong? -40dB ~= 1% and not ~10%

 

[Old_School_Brad]

The internet is unfortunate sometimes. You post article after article which I love and appreciate. And then of course the one time I disagree, well, here I am interacting and disagreeing. Let me take this opportunity to thank you for all of the amazing work you do before I get back to questions and disagreement.





I'm quite confused by all of your statements and conclusions in these replies.

I have no doubt that a lot of teenagers throw subwoofers into their cars with zero tuning. Certainly my ears tell me it's true when one drives by.

From everything I have ever seen, EQ is absolute table stakes for anybody who cares about sound quality in car audio (as opposed to trying to set SPL records or simply annoy the neighbors)

Unlike a reasonable home listening environment, where EQ can be somewhat optional, an auto interior is a bit of an acoustic nightmare. That is doubly true if we're cramming a speaker under a seat, which is the explicit manufacturer use case for this product.

I also think you are underrating the in-car gain this subwoofer will get. In a sedan, rule of them is that it will be around +12dB per octave, which conveniently is approximately equal to a woofer's typical roll-off.

Anyway, I am a midget here in terms of knowledge. If I am wrong, somebody please correct me. I have no idea if this thing will actually sound good, and I am sure it will be less effective effective in the larger interior of a Sprinter van vs. a sedan.

Context is key.
This compact subwoofer is specifically designed to enhance bass in a small car cabin -and that’s its entire purpose.

It achieves this by having a deliberately “peaky” frequency response, creating the sensation of deep bass through upper-bass emphasis -often referred to as “cheat bass.” This tuning approach delivers a satisfying punch while keeping the enclosure compact -ideal for users with limited space. In real-world use, the natural cabin gain in smaller vehicles enhances low frequencies, making this tuning more effective in practice than the raw frequency response graph might suggest.

It’s very likely not a matter of JBL lacking expertise -quite the opposite. They understand their target audience well and have engineered this product to meet their expectations.

Amir’s van is not the intended environment for this sub.

And enthusiasts with extensive car audio experience aren’t the primary market either.

 

[Talisman]

I had suspended disbelief about this product category as well, and always wondered what they would look like on the test bench. Well, now we know.

If anyone was wondering what "one note bass" looks like, I could hardly imagine a better example.

I think that is a very reasonable hope.

We've seen KEF work miracles with 8" drivers in small boxes... this is not that.

"Frequency response 35hz - 120hz" ... I think everyone should burn that "spec" and this graph into their brains before they buy another speaker without seeing measurements...

Let's think for a moment about the use cases, cars or campers without a decent sound system, background music while traveling with ambient noise at - 20db if all goes well, windows open, engine etc etc.
The subwoofer in this context does not do what a hifi subwoofer does, that is, correctly represent all the frequencies below 80hz, it does what it can and what is needed, it gives a boost to some low and medium low frequencies that fill a bit compared to the almost absence of those frequencies, a push that makes you perceive the presence of a bass, significantly improving the listening pleasure.
It is always a mistake to evaluate an instrument outside of its scope of use.

 

[amirm]

But still the scale of the right graph is wrong? -40dB ~= 1% and not ~10%

Good catch! I don't know what happened but the percentage was for some other volume level. I corrected the review:

 

[amirm]

Let's think for a moment about the use cases, cars or campers without a decent sound system, background music while traveling with ambient noise at - 20db if all goes well, windows open, engine etc etc.

I will have measure the noise level in the cabin. For now, like noise indoors, it is going to have a spectrum. Some frequencies are damped more than others so the needed dynamic range will vary.

 

[M.C. Logan]

Not sure what year you have. Do you have the Harman upgrade sound system? If so that is pretty decent right, with some decent DSP adjustments available? Different market have different sound options in these.
You can upgrade the drivers in the stock subs, not sure what level of benefit comes with that.

https://www.crutchfield.com/g_456350/Replacement-Subs.html?l=X

Kind of pricey for those drivers.

But yah, if you want deep and higher SPL bass you will give up space in the hatch. Lots of folks are cool with that. Lots more are not.

You'd shocked at what a fully custom install could do but that could be $$$ thousands and you might have to search for the right installer, could be many months of planning and waiting.

What most do is build or buy something like this Kicker 'shelf' much more high quality bass on tap vs the underseat option but keeps the rear hatch functional as a grocery getter for many people.

https://www.crutchfield.com/p_20651PTRT0/Kicker-51PTRTP10.html?tp=114

This just lays flat, driver facing down and the topside can be used for setting things on it.
10" version shown here, the 12" is thicker but same idea

View attachment 452717


This JL audio thing has dual 8's and is small.

https://www.crutchfield.com/p_13693331/JL-Audio-ACP208LG-W3v3.html?tp=114

View attachment 452718

Custom ideas
View attachment 452720

I have a 2012 F25 X3, Diesel, 3.0xd in the UK so no point in any USAican references. And Yeah, like most people I use the boot, all the time, otherwise I'd have a convertible. I honestly don't understand why one would have an X3 size or larger SUV unless you need the space in it. Mine is either filled with shopping, compost or a dirty English Springer Spaniel. I upgraded the basic speakers with some improved aftermarket ones, including the under seat bass drivers, not brilliant but now tolerable, and that cost nearly £400 ($530) plus fitting, not paying more than that for something I only use a few hours per month.

 

[ROOSKIE]

I have a 2012 F25 X3, Diesel, 3.0xd in the UK so no point in any USAican references.

Howdy, the USA links are to demonstrate some products and ideas in a type of public conversation, not necessarily be a reason or correct place for everyone reading to shop.

The links may not interest you directly, this is a public message on a worldwide public forum.
While I quoted you, it was not a DM, so links are general info for you, & anyone and all following along. Some may appreciate the information, some will not.

 

[Orion76]

Fun seeing reviews like this. I had an Infinity Basslink in the trunk of my little car- 10" sub, 10" passive radiator, 200 watts. I was very happy with it.

 

[kemmler3D]

Let's think for a moment about the use cases, cars or campers without a decent sound system, background music while traveling with ambient noise at - 20db if all goes well, windows open, engine etc etc.
The subwoofer in this context does not do what a hifi subwoofer does, that is, correctly represent all the frequencies below 80hz, it does what it can and what is needed, it gives a boost to some low and medium low frequencies that fill a bit compared to the almost absence of those frequencies, a push that makes you perceive the presence of a bass, significantly improving the listening pleasure.
It is always a mistake to evaluate an instrument outside of its scope of use.

In one sense you're right, but in another sense, fitting a "subwoofer" under a car seat was never a very realistic idea, and this product shows why. I'm pretty sure you can get portable Bluetooth speakers with more output below 100hz.

 

[Timcognito]

Got to have the "SLAPS" technology

K-10 Kompressor Tube

The 10 inch K-10 Kompressor Tube with SLAPS passive radiator technology is technologically one of the most advanced subwoofer tubes on the market.

earthquakesoundshop.com

 

[M.C. Logan]

A speaker whose primary purpose is to reproduce frequencies under 100Hz or so is commonly referred to as a subwoofer.

Well, sub bass is c. 20-50Hz, ergo sub woofer is for that range in my book.

 

[Chrise36]

FWIW 2 6*9 in bass duties under the seats works great especially if you make them big enough.

 

[M.C. Logan]

Howdy, the USA links are to demonstrate some products and ideas in a type of public conversation, not necessarily be a reason or correct place for everyone reading to shop.

The links may not interest you directly, this is a public message on a worldwide public forum.
While I quoted you, it was not a DM, so links are general info for you, & anyone and all following along. Some may appreciate the information, some will not.

No need to get so upset, simply not relevant to me, I write like I talk, a conversation.

Well, sub bass is c. 20-50Hz, ergo sub woofer is for that range in my book.

And since my main speakers go down to 50Hz and I don't class them as subwoofers.....

 

[Palladium]

I have stock Pioneer oldschool head unit door hooked to doormount 5" speakers with no subs in my work van. I actually had to kill ALL the bass boost, EQ down the bass significantly 80Hz as well as run a 4th order HPF at 50Hz with the built-in tools to get a semblance of neutral bass.

(BTW this combo sounds surprisingly good either on FM or when hooked to a Tunai Firefly LDAC->3.5mm portable receiver)

Its consistent with what I read about car interiors having massive inherent bass gain (~20dB at 20Hz) because the enclosed volume is so much smaller than residential rooms. I really don't see the point of car subs unless you want to annoy bystanders or get hearing damage.

 

[kyuu]

Its consistent with what I read about car interiors having massive inherent bass gain (~20dB at 20Hz) because the enclosed volume is so much smaller than residential rooms. I really don't see the point of car subs unless you want to annoy bystanders or get hearing damage.

20dB of boost isn't enough if the speakers have no bass response to speak of, which is common with the small drivers stuffed into door panels.

 

[Old_School_Brad]

20dB of boost isn't enough if the speakers have no bass response to speak of, which is common with the small drivers stuffed into door panels.

Simultaneously, the 10 W head unit attempts to drive frequencies below 75 Hz through those same speakers. This can make it difficult to tell whether any noises coming from the doors are due to rattling, distortion or clipping..

Car audio is often underestimated by those who haven’t been involved with it. In reality, achieving high-quality sound in a car is just as complex and rewarding as setting up an excellent listening environment in a dedicated room. When done properly, I would argue that a well-designed car audio system can deliver an experience that rivals the best home audio setups.

 

[AudioSceptic]

This is a review and measurements of the JBL BassPro SL2 underseat slim "subwoofer" for automotive use. I purchased it for US $275.
View attachment 452585
The idea behind these integrated active subs is to stick one easily under any of the seats in the car and immediately get a boost in the low end. This is my application in trying to improve the sound in our camper van which currently only has small door drivers. It is easier and less parts than building a box and using an external amp. There a lot of companies offering this but I thought I pay twice as much for this JBL offering. As you see, it kind of manages to look attractive although the I wished it was built out of metal than polycarbonate. Controls are nice and what you expect in a proper amplifier:
View attachment 452586

I hooked the unit up on my bench but was kind of hard to test as it would resonate everything around it. And basically what you heard from it was "thump thump." So I decided to measure it.

Here are the specs:
View attachment 452590

JBL BassPro SL2 Subwoofer Measurements
For something like this that doesn't go very deep or very loud, I am able to just put it on Klippel NFS and measure it just like any speaker. As usual, I start with my usual near-field testing and was disappointed to see such a peaky response:

View attachment 452587

No matter what I did with the three controls, I could not get anything that was a mountain. That made setting levels hard but I used to the peak and measured distortion at "86 dBSPL:"
View attachment 452824

The right relative THD is normally set to 5%. That resulted in the graph showing nothing but lines to out the top. I had to set it to 100% to get what you see. Even at its optimal output of 100 Hz, distortion is 15% and rises to 60% at 45 Hz.

Edit: Percentage graph was wrong. It is now at full scale like other measurements.

On the other hand, distortion is quite low in 200+ range. As such, I wish there was not such a forced roll off there as it could offload that duty from the midwoofers in the system.

The low bandwidth meant that Klippel NFS could characterize with very few points, reducing measurement time to just 40 minutes, resulting in what we already knew:
View attachment 452591
There was little beaming so I am not going to show the derivativity plots.

Conclusions
Without a reference, it is hard to know how good or bad these numbers are. Fortunately I also bought a Kicker version I will be testing next. Until then, I sort of assumed laws of physics were suspended and this thing would act like a proper woofer with flat response until it couldn't. Instead we have this one note response. With EQ it the peak can be flattened but then I worry about amount of power available. Will be testing it in van and post the final conclusion then.

For now, I am starting to think that a box with a driver and external amp may be a better way to go. Place I have for it is 17 by 17 inches and can have as much as 5 to 6 inches height. Hoping better response can be had with increased volume.

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"I could not get anything that was a mountain" should be "I could not get anything that was not a mountain"?
"derivativity plots." should be "directivity plots."?

Disappointing results in any case. I would expect at least an attempt at a flattish response over an octave or so.

 

[amirm]

Its consistent with what I read about car interiors having massive inherent bass gain (~20dB at 20Hz) because the enclosed volume is so much smaller than residential rooms. I really don't see the point of car subs unless you want to annoy bystanders or get hearing damage.

My SUV has OEM subs in the back and it sounds excellent. Far, far better than my van does which currently has no bass and annoying mids.

As I noted, the RV vendor had put a sub in there before. That did create boom boom but that is because no tuning was done whatsoever. As you see from the response of this sub, these things can't be thrown in a car and expect it to perform. The small volume of a van/car means that modal response goes up to hundreds of hertz. You are just not going to get even response without EQ.