Laboratory test resuLts
Newport Test Labs’ fourth graph (why not make it the first, guys?) tells the story here most clearly, with the lab having measured the PSB SubSeries 200’s frequency response at a distance of two metres from the subwoofer, using pink noise as a test signal. The captured data was then smoothed to one-third octave via post-processing. The black trace on Graph 4 shows the SubSeries 200’s response when the crossover is set to 150Hz (its maximum setting) and you can see that it is extremely flat from 35Hz to 125Hz and overall extends from 24Hz to 180Hz ±3dB. This is an outstanding result.
When the crossover control is set to its minimum (50Hz) setting, the response is at its most flat across the 25–65Hz region after which it rolls off very smoothly. This response appears to get a little extra energy down at 25Hz. In this configuration, the PSB SubSeries 200 returned a frequency response of 18Hz–75Hz ±3dB.
The first three graphs really show how PSB’s engineers achieved these results. Graph 1 shows the nearfield sine response of the bass driver (black traces) and the port (green traces) with the crossover set to maximum (dashed traces) and minimum (solid traces). You can see that the bass driver’s natural response peaks at 80Hz but is getting quite a bit of extra assistance from the bass reflex port across its operating region. The driver’s minimum output is at 29Hz. You can see that this doesn’t quite marry with the maximum output of the port, which occurs at around 27Hz, and it would appear that this is due to PSB’s engineers ‘tweaking’ the alignment to get a little extra low-bass from this design.
Graph 2 shows the difference between using the PSB SubSeries 200 with the crossover set to 150Hz, and with the crossover bypassed (by using the LFE input). You can see the output is essentially identical below 125Hz, other than a slight difference in level due to the crossover circuitry. Above 125Hz you can see the SubSeries 200 rolling off the response fairly steeply when the crossover is in circuit, whereas the high-frequency response is slightly more extended—and rolls off a little less steeply—when the LFE input is used.
As I said at the beginning of this section, it’s Graph 1 that tells the story here, and it’s an excellent story, because the PSB SubSeries 200 is a very well-designed subwoofer that has a flat and extended low-frequency response and whose controls will enable it to be integrated with any main speaker system you might use, whether it’s a bookshelf/ standmount model or a floorstander.
Steve Holding