4-ohm setting with 8 ohm speakers


I have the Nightingale CTR.2 open baffle speakers. The manufacturer claims that "the Concentus CTR-02's speakers and crossover are designed and assembled on the acoustic screen following a scheme meant to guarantee that the impedance stays linear as the frequency changes."

However, with every amplifier used with these speakers, a 4-ohm setting sounds more natural and relaxed. Now I am listening them with the Hans Labs KT-88 power amplifier. With the 8-ohm setting, the sound is more tight, bland and stringent, it sounds more like a mid-level SS amplifier. I am wondering how this can be explained from technical point of view?
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Showing 3 responses by plato

This doesn't make sense to me and what Arnettpartners said doesn't make sense either. So just accept it as one of those weird audio interaction anomalies that works for some unexplained reason. Perhaps the maker of your amp or the maker of the speakers could shed some light on this.

Personally I wouldn't lose sleep over it. I'd just use the amp on whichever speaker taps sound best with your speakers. Surely it won't hurt anything.

If you find out the actual reason down the road shoot me an e-mail and let me know.
Okay, I see a lot of erroneous info flying around in this thread. A 4-ohm load is a lower impedance and thus a tougher load for an amp to drive (not easier).

Some confusion creeping in here involves the typical solid-state vs tubes. Typically, solid-state amps have more power driving into lower impedance loads, in fact, many of them double power into 4-ohms (this does not mean they sound better driving 4-ohms). Tubes, on the other hand (which is what we're talking about here) are typically optimised to drive 8-ohm loads, with some optimised for closer to 4 ohms.

This means that many tube amps will deliver a bit more power into 8-ohms than they will into 4-ohms. In most cases, the actual power difference is small, unlike solid-state.

That said, if you use a tube amp's 4-ohm taps to drive 8-ohm speakers it does increase damping factor and decrease distortion. In some cases, this can sound "better" to the listener, and in other cases it can sound "dryer" and more like solid-state. Sometimes the little extra distortion and looser bass is preferable to some listeners, because it usually gives a sweeter, though less focused, sound.

In this particular case, the results probably have to do with the tube amp being optimised to drive closer to a 4-ohm impedance coupled with this particular listener's personal bias. And of course interaction with the impedance curve of the particular speaker will come into play. This is why amplifiers can sound different when driving different speakers.
Magfan, I think you read my comment wrong regarding me saying you'd get "looser bass with the 4-ohm taps." Perhaps I didn't make it clear but the 4-ohm taps (compared to the 8-ohm) would increase damping factor for tighter bass. Distortion would also be less using an 8-ohm speaker on the 4-ohm amp taps. I said the bass would be looser using the 8 ohm taps, and that the 8-ohm sound may be sweeter though less focused/precise, but that some folks might still prefer it that way.