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JBL BassPro SL2 Under Seat Slim Subwoofer Review

Rate this Automotive "subwoofer:"

  • 1. Poor (headless panther)

    Votes: 62 72.1%
  • 2. Not terrible (postman panther)

    Votes: 20 23.3%
  • 3. Fine (happy panther)

    Votes: 4 4.7%
  • 4. Great (golfing panther)

    Votes: 0 0.0%

  • Total voters
    86

amirm

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This is a review and measurements of the JBL BassPro SL2 underseat slim "subwoofer" for automotive use. I purchased it for US $275.
JBL BassPro SL2 Active Underseat Car Subwoofer Distortion Response Review car.jpg

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:
JBL BassPro SL2 Active Underseat Car Subwoofer Distortion Response Review wiring connectors ba...jpg


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:
JBL BassPro SL2 Active Underseat Car Subwoofer specs specifications.png


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:

JBL BassPro SL2 Active Underseat Car Subwoofer Anechoic CEA2034 Frequency Response gain crosso...png


No matter what I did with the three controls, I could not get anything that was not a mountain. That made setting levels hard but I used to the peak and measured distortion at "86 dBSPL:"
JBL BassPro SL2 Active Underseat Car Subwoofer Distortion Response Measurements.png


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:
JBL BassPro SL2 Active Underseat Car Subwoofer Anechoic CEA2034 Frequency Response Measurements.png

There was little beaming so I am not going to show the directivity 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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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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ASR: Automotive Sound Review?
At least temporarily until I finish this project. :)

Seriously, I have done testing of car audio here and there as members have sent products in. I built my Lithium batter bank for this purpose so am setup to do more testing.
 
Many years ago I had a Kenwood W00X in my F150 without any back seat. It fit perfectly behind the driver’s seat and gave that extra kick I needed. Wonder how it would have measured. This JBL isn’t going to win any competitions but when space is limited I think it’s going to be a nice option.
 
Thank you for those refreshingly different reviews. :cool:

Kind of 1990s Bose Acoustimass and small PC subwoofer one note bass tuning if not used with EQ/DSP, Pioneer (who was at some time the largest loudspeaker driver manufacturer in the world) used to and still has also some low budget compact subwoofers to place under your seat, wonder how they measure.
 
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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.
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.
Hoping better response can be had with increased volume.
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...
 
Every time I’m sitting at a stop light and some jackass pulls up next to me with a thousand watt subwoofer rattling my car, I have very, very unhealthy thoughts.
Take solace in the fact that they're actively making themselves deaf... you don't even need to do anything to get back at them, it's taken care of.
 
Every time I’m sitting at a stop light and some jackass pulls up next to me with a thousand watt subwoofer rattling my car, I have very, very unhealthy thoughts.
Take solace in the fact that they're actively making themselves deaf... you don't even need to do anything to get back at them, it's taken care of.
This is actually due to excess leakage due to poor integration, I had someone tell me how they went through something similar and even though it was so loud outside the car, inside it sounded normal.
 
Saving grace here would seem to be that huge SPLs are not needed for a car, given that it's extremely near-field and a very small "room". Even after lopping off the huge peak via EQ I should think there's would be enough SPL headroom available for any sane requirement of bass. If you want to rattle the door panels off and piss off everyone around you, then should definitely look elsewhere though.
 
Doesn't the Klippel predict room response? I would think that a room the size of a car would have a lot of reflected low frequency energy. You would not want anything close to a flat, anechoic response for a flat, in-car response.
 
If the Sprinter's original sound system did not have a subwoofer, you should check to make sure the factory head-unit even outputs low frequencies. Many have a high-pass filter in place, which lets them get a little more volume out of those 4-inch "woofers." I ran into this problem when I wanted to add a subwoofer to an economy car (Honda Fit/Jazz). The head unit does not even output subwoofer frequencies, so I never added one.... :mad:
 
It always has an added interest to test unorthodox designs.
Now where's the in-van response graph? :D
I'd be curious to see how it measures at driver's level when it's set.
 
Thank you for the review, @amirm
What will you do with the JBL? It definitely sounds like a 'hand-me-downer' item.

We had built bench-like storage compartments (with locking/hinged lids, and shag carpeting) in our college Tradesman300 van.
After filling these nooks with tools, gear, cassettes, etc., I still had few compartments (24"Wx12"Dx16"H) empty.
Stuffed them with a few 10" speakers... and learned all about how NOT to build DIY subs!:cool:
 
I would think that a room the size of a car would have a lot of reflected low frequency energy. You would not want anything close to a flat, anechoic response for a flat, in-car response.
I agree with the first part, but I am not sure how to evaluate room gain / modes in a case where almost the whole frequency range has wavelengths longer than the space. So maybe a flat response is as good a place as any to start?
 
Subs having a not-peaky response is "a privilege, not an entitlement" (to use a term from my conscription days).

But that's what DSP is for
 
...This is my application in trying to improve the sound in our camper van which currently only has small door drivers...
The JBL may serve a sub-lemental purpose, while the camper is stationary (e.g., camping) but wouldn't the drone of the camper - while in motion - fully negate its [woeful] raison-d'être?
 
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