I have been researching several A/V receivers and the HK's have a noticible sound degregation when driving 6 Ohm loads. Is this typical for all receivers or just the mass-market ones.
For instance NAD says their receivers can handle 4 and sometimes 2 Ohm speakers but they never say if THD pays the price as far as distortion goes.
Maybe one of you gurus can shed some light on this.
I assume you are looking at spec sheets and not actually listening to the receivers.
It takes a lot of work to run low impedence speakers. Although 6 ohm speakers are not what I consider "low", the lower the impedence the more current will be required by the power supply and more heat will be generated by the amps transisters. Both may be being pushes to thier limits causing distortion as the near clipping.
Hope that helps.
Well theres still my question in particular about NAD's power supply and transistors. I assume the very high and high end receivers account for this drain on current/power supplies. How does NAD fair? I haven't seen any specs addressing this issue.
NAD simply uses better power supplies. They also realize a high dynamic power advantage which briefly produces up to four times the rated power. This burst will have high distortion but it's better than the sound of clipping.
This startded about 15 years ago when NAD, Proton, Soundcraftsmen, Carver and other started producing amps with high dynamic power through two sets of power supply rails or signal tracking switching power supplies.
I once had a Proton receiver that was rated at 20w/c but could do 100 watts into 2 ohms easily.