Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems G57 with 4Ohm

Hmmm, my mileage varied. And I'm basing this on the assumption that the G57 is similar to the 557.

My Kefs are 4ohm nominal, with dips to 2 ohm at some frequencies. It took a move to 557s to contain this, and they did a spectacular job. I hadn't compared with as high quality competition as Ivan, but I had noticeable dips at 60Hz (the main 2R offender) with my prior Arcam. The 557 was still capable of driving linearly down there. I had the effect of extra bass after the upgrade, but it was simply the output not dipping in the crossover region like it did with a less current-capable amp.

For low impedance loads, you want an amp with a very high current drive ability. This tends to require a huge transformer and lots of high power output transistors. The specs will show massive power outputs for low impedances and bridging (which halves the effective impedance since the other end of the load is being 'pulled' by the other channel). Basically, the amp will appear to be overbuilt for its rated power output. Distortion will increase as the output stage and power supply is more heavily loaded (which may explain Ivan's harshness commment), and the spec's should include distortion at 4R (or be worst case figures across the rated range of the amp).

Personally, I've always thought that this is one reason that people find really powerful amps to sound great at lower volumes - the reserves are there to handle any non-linearity in loading from the speaker.