JBL LSR310s Teardown and Analysis

8 August 2016

The JBL LSR310s sub is so good I had to take it apart. I hesitated buying it since I wasn't a fan of the downfiring and not grill-protected woofer, but having the LSR305s I decided to be brand loyal and wow: -3dB at 32Hz and quite flat above. It is audible with uncolored bass lower, though at much diminished SPL, which my equipment cannot properly measure, so let's say -10 dB at 27 Hz.

Board shots follow, let's go thorugh!

The switched power supply takes the right 2/3 of the board and provides 47V output to the power amplifier, in addition to +/-15V for the input opamps and 5V and 3.3V for the digital chips. The power amplifier is bridged, but I didn't take the heatsink off to note the chip used. My suspect is STA516, which implies the circuit has a generous power reserve. The power amp heatsink gets to 45 oC when the board is idle and exposed to open air.

Zooming in on the audio section:

The ADC is CS5341 while the DSP is STA309A.

Side of view of the main board.

Finally the MDF cabinet (thin but braced) and woofer (not cast chasis) don't seem to make an impression, but certainly seem to get the job done. The only downside I readily notice is the lag - at sub 30 Hz, building the cabinet resonance and firing through the port introduces a detectable delay.

Overall good stuff, I highly recommend it. Though the Rockville APM10B apparently has the same main chips for 40% of the price. Anyone willing to try it out?

LSR305 review + teardown here.

Comments for JBL LSR310s Teardown and Analysis

Shail on February 7, 2017

Hey Rouslan! This looks great. The LSR305's are good on their own. I use them with unbalanced out from a computer. Would the subwoofer accept the same kind of unbalanced Line level signals. I wouldn't want to buy an expensive DAC just to do balanced cable runs for short distances :-)

Rouslan on February 7, 2017

Yes, I drive the woofer straight from my sound card through a mono 1/4" jack to RCA adapter and then 1/8" jack to RCA cable. The negative input is thus grounded & I do not hear hum or buzz, so you are good to go!

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