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.

@mamifero - This remains a math problem wrt having enough power to drive that particular speaker to the desired SPL for your room and listening position.

The post by @atmasphere below explains why I used 83dB in my calculations.  To his point, even my second example of a 200 wpc amplifier that doubles into 4 ohms will only drive those speakers to a SPL of about 100dB at 12 feet.  That calculation does not take into effect a larger than typical room, speaker impedance anomalies, or the desire for greater dynamic headroom so, even at 200/400 wpc you my have barely adequate power.

As a result, there is probably no way you will have satisfactory results driving those speakers with your current amplifier.  I don’t disagree with the 1,000 wpc recommended by @atmasphere, assuming he means into 4 ohms.  IOW, an amp delivering around 400 to 500 wpc into 8 ohms and doubling into 4 ohms, should be about optimal.  The Cary 500MB amps in my second system provide 500/1,000 wpc of power, and the SMc Audio monoblocks in my main system provide 650/1,000+ wpc and do an excellent job of driving Aerial LR5 speakers that have the exact same sensitivity and nominal impedance specs as the Technics speakers you are considering, while dipping to an even lower minimum impedance of 3 ohms. 

As to sound quality, IME, amplifiers do sound different from each other so, like any component, you will need to find amplifiers delivering the type of sound you want to hear. However, if you don’t get the power right, your speakers will never reach their optimal sound quality.