The LSR305 is a great speaker for the price, but it has some key flaws. @Erin in particular noted a nasty resonance around 220Hz in his review. Since I have a pair I am repurposing for garage use, I thought I'd try a few modifications and see what effect they had. They are all simple so I only have before/after measurements for the whole set, not as individual changes.
The mods are:
The results are way better than I expected! The graph below is from the accelerometer on the back and side panel of the speaker, both before and after the mods. Compare green to green and orange to orange. The port resonance itself hasn't changed much, but the rest of the behavior is between 10dB and 20dB down compared with before the mods. The nearfield FR for the port and bass driver show that the 1.5KHz trash fro the port is still there. I'll probably fix that with some melamine foam on the wall behind the port.
Subjectively the speakers sound a lot closer to my reference system, with speech intelligibility being obviously improved.
The mods are:
- Filling voids in the front panel with polyester filler ("Builder's bog" in Australia). I used an 800g tin of filler and managed to get 300g in per panel before it set too hard to use any more
- Wrapping the port with some foam tape, and securing it with a zip tie
- Glueing 10x30mm strips of hardwood to the top, left, bottom and right panels
The results are way better than I expected! The graph below is from the accelerometer on the back and side panel of the speaker, both before and after the mods. Compare green to green and orange to orange. The port resonance itself hasn't changed much, but the rest of the behavior is between 10dB and 20dB down compared with before the mods. The nearfield FR for the port and bass driver show that the 1.5KHz trash fro the port is still there. I'll probably fix that with some melamine foam on the wall behind the port.
Subjectively the speakers sound a lot closer to my reference system, with speech intelligibility being obviously improved.