Amplifier recommendations for 86 dB Sensitivity Speakers

Some useful information about amplifiers in the link associated with this recent A’gon thread (link to thread).

As others have said, not only are your speakers 86dB efficient (SPL @ 1M, @2.83V), but it is actually worse since they are rated for a 4 ohm impedance, which makes them only 83dB efficient for an input power of 1W.  As the impedance spec of 4 ohms is not clarified to be the nominal or minimum impedance, it could be even worse if the impedance drops further at certain frequencies. 

If you are still in the system building phase, then choose speakers that deliver the type of sound you like for the music you listen to, and then find the appropriate amplification that will adequately drive them.  As others stated, if you enjoy tubed amplification then look for medium to high efficiency speakers with nominal impedance of 8 ohms or above and no crazy impedance dips.  If you like the sound of 86 dB speakers with an impedance of 4 ohms (which is the rating of my speakers), then you need to have some power (i.e., current/amperage) to drive them.  Look for amplifiers that double, or nearly double, their output when the impedance is halved and that are stable into lower impedances.  Here is (a link to) a calculator that can determine the SPL output for a given power and speaker efficiency in W/1M (your proposed speakers are rated at 83dB @ 1W/1M so use 83 in the calculation).  Using the calculator, for your proposed speakers, an amplifier rated at 100w/channel/4 ohms will provide a SPL of about 95dB at a listening distance of 12 feet.  Figure out the sound pressure level you want to achieve and compute the minimum needed power rating for amplifiers you are considering.  I am not sure what rated power your Cayin will deliver into 4 ohms since it is rated at 8 ohms, but it may be 100 watts.

My amps do not quite double their power from 8 to 4 ohms, but they are rated at 650 wpc @ 8 ohms so even if they don’t double into 4 ohms there is plenty of headroom to drive my less efficient speakers.  In your case, I would look for amplifiers that provide at least 200 wpc into 8 ohms and that double into 4 ohms.  Using the calculator that gives you a maximum SPL of about 100 dB at full power.  Choose even higher powered amplifiers if you like to listen loud and then, even when not rocking out, the higher power can provide dynamic headroom to better handle musical peaks and to keep things from sounding thin.

Agree that most tube amps that can comfortably drive a 4 Ohm speaker will have 4 Ohm speaker posts or the amp’s transformer has different internal taps to wire to the binding posts.   
 

My Quicksilver amps have 4 and 8 Ohm posts.  My 300b amp has 8 and 16 Ohm taps … confirmation that it’s not a good match with difficult loads.

Often times a tube amp will put out less power with 4 Ohm speakers connected to an 8 Ohm post.  
 

Just picked up a pair of 6 Ohm speakers. They are 88dB sen and 50 watts wasn’t quite enough.  100 was a good match. 
 

your amp has 4ohm taps so just hook it up to those and you should be fine at low to moderate levels. 

Thanks everyone for your really helpful comments.

Indeed, the Cayin A100T has 8 and 4 Ohm taps, and I’m sure it can drive 86 dB speakers, however, since I couldn’t find information regarding its 4 Ohm output, I am not sure if it would have enough power to make those sound good and as were designed for; probably when they engineered these they had in mind those really advanced and powerful Technics amplifiers, or something similar. 

As a reference, I remember testing my old B&W 705 monitors with two different tube amplifiers. One was a 40 watt per channel and the other was this Cayin (70 watt per channel), and at the same volume level, the more powerful amplifier made a significant difference, it made the 705s sound more defined, in particular the bass was much better. So, I believe it might be the same with these Technics speakers, the Cayin will be able to output adequate power but I might be missing out their full potential.