To sum it up, in comparison to the BassBoss SSP118, the SRX818P falls noticeably short from 55Hz on down and very even from 60Hz - 90Hz.
The dual SRX828, in comparison to the BassBoss SSP118, basically beats it everywhere (not by a lot) and more noticeably from 55Hz - 100Hz.
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In frequency response terms, the JBL SRX828 performs almost identically to two SRX818, meaning it gives you the same frequency response with 6dB more output. The JBL SRX828 offers maximum continuous output of 134dB at 67Hz. That means peak output can be calculated to 140dB.
The BASSBOSS SSP118 is competitive with the SRX828, offering almost equivalent output between 35 and 50Hz. The SRX828 offers more output above 50Hz and a bit more below 40Hz. This is to be expected from a double driver sub. The design is essentially two SRX818 boxes joined at the port side. The SRX828 will deliver a bit more very low bass at maximum output because it helps to have another 18" cone to displace that air.
At maximum level, the JBL offers 3dB more output at 30Hz, 2dB more output at 35Hz, 0.8dB more output at 40Hz, 0.3dB more output at 45Hz and 0.7dB more output at 50Hz. Above 50Hz the two lines diverge, with the JBL continuing higher and the SSP118 going lower. At 55Hz the JBL double-18 shows a 3dB advantage, at 60Hz it shows a 4.2dB advantage, at 65Hz it shows a 5.7dB advantage, which it holds through 90Hz.
The SSP118 was designed to be a subwoofer, to deliver as much deep bass as possible from a relatively small, portable enclosure. The fact that is does an excellent job at this is evident in the fact that between 40 and 50Hz, it runs neck-and-neck with either a double 18" subwoofer, or two single 18"s. In either case, the JBL's are twice its size. The SSP118 offers better low bass performance than all competitors' similarly sized single 18" subs that we've so far tested, and better than some that are much larger, including the Yorkville 21". The JBL SRX828 double-18 is the first box tested to offer more low frequency output than the single-18" SSP118.
An important thing to consider that is demonstrated in the response graph is the sound "character". It's true that you can't hear a loudspeaker by looking at a response graph but you can get an indication of its character. These graphs can tell you a lot about what to expect in terms of "sound quality". You can determine where the energy is focused, what it does best and the overall balance across its spectrum. This does give you a good indication of what it's going to sound like. The words people use to describe these things vary but a high resolution frequency response measurement graph will tell you a lot about the "character" of a loudspeaker. Is the energy focused at the bottom end of the spectrum, in the middle, or at the top? What does it give up and where does it peak when you turn it up to the limit?
Under normal operating conditions, the SSP118's energy is focused between 35 and 55Hz. What it gives up when it enters compression is some of the energy between 25 and 45Hz. When pushed to the limit, it peaks at 50Hz.
The JBL SRX828's energy is focused between 47 and 83Hz. It gives up energy between 30 and 50Hz when it enters compression. When pushed to the limit, it peaks at 67Hz.
At maximum output above 50Hz, the SSP118's output decreases where the SRX828's output increases. This gets into the area of design choices and philosophy. Both at maximum and below maximum, the SSP118's output decreases above 50Hz. This is a deliberate choice intended to give the SSP118 a full, rich tone, to make it sound big and deep. To give it a big and deep character, it could not be designed to also go as loud in the upper end of its range. This is necessary to allow the SSP118 to get as loud as possible as low as possible and, when it's turned up to the limit, to prevent it from changing character and sounding different. Thus, at any level the SSP118 has a "deeper voice" than either of the SRX boxes.
In comparison to the SRX818, the SSP118 is deeper and louder. The SRX828 has a louder voice, but if you wanted to give the SRX828 a deeper voice, to match the tonality and balance of the SSP118, you would have to give up on much of the area where it is louder. So, if you like your bass deeper, the SSP118 will do very nearly everything the SRX828 will do from a box that's half the size. That said, the SRX828 is a good product for the price. Next we'll be testing it against our double 18" subs, and we'll post that as soon as we have the testing done.
BASSBOSS SSP118: 130dB continuous. 136dB peak. Peak output frequency: 50Hz
JBL SRX828SP: 134dB continuous, 140dB peak. Peak output frequency: 67Hz
On the subject of limits, if you do tend to run your system buried in the limiters and every bit of output is necessary, it might be tempting to consider the higher output SRX828. On the other hand, the BASSBOSS warranty covers your boxes for 6 years, your amps for 3 years AND covers you against blown voice coils for 2 years. The JBL warranty covers the boxes for only 2 years, the amps for 3 years and if you blow the drivers you aren't covered at all.
Thanks for your questions, I'm enjoying testing these subs!
best
David Lee
Although it would be pricier, a pair of BassBoss SSP118's vs. a JBL SRX828 would easily favor the BassBoss' (the graph would go +6dB at every point for the SSP)
For you SRX 818SP and especially SRX 828SP stans, fans and owners... you've still got a good sub.
