The Extrema has a sensitivity of 88dB/W/M, so at 1m distance, 1 watt will produce an SPL of 88dBOf course, apologies for my over long post. Just one summary point before I go silent: current limited amplifiers like the Devialets and the Halcros will definitely not work very well with the Extremas (which are very hungry for current).
Now, lets apply some very simple math to get to a realistic listening position and volume
If we sit 4m (13ft) away from the speaker, we‘ll need 4W for the same 88dB (double the power for doubling of distance)
If we now start to crank up the volume we get the following (For each doubling of input power to the speaker, there will be a 3 dB increase in output)
Given the Extrema spec calls for a maximum 200W amplifier input, the most you‘re going to get out of them at 4m is about 105dB. If you need more for a larger room or a more distant listening position, then you’ve bought the wrong speaker and you need something that is more sensitive and can handle larger input currents.
Take a look at the Halcro and Devialet specs. 1000w into 6 ohms and 500W into 4 ohms Both have thermal cut-off protection But if you were driving your Extremas flat-out, you’d be using between 12.5% or 25% of either amplifier’s output capability. The reason the cut-off is thermal is that it limits SUSTAINED output rather than instantaneous. But, depending on the mains supply you are using, if its a regular household mains supply based on the typical 1.5mm2 cabling over quite some distance, with lots of questionable junctions then, you will potentially get some voltage drops at high volume (high current demand) which will clearly manifest through a drop in sound quality. If you want to get the most from these speakers you do need to make sure you’re providing the instantaneous current capability they need.
The reason high current amplifiers are recommended for the Extrema are:
1. They’re quite inefficient at 88dB/W/M
2. They need a largish room to operate at their best (plenty of space between them and well away from walls)
3. For a small 2-way speaker they produce great dynamics when the amplifier has sufficient instant current capability and plenty of headroom.
4. They are capable of handling high power transients.
So what you need is an amplifier with around 200W preferably with a mains supply that can respond to the amplifiers’ instantaneous power demands.