Sensitivity 86 v 90

What is your preferred listening volume in the room? Have you bought a sound level meter in order to get a real number to work with?  Note that one person's "loud" is another's "medium" and so on.  The size of the room is also a factor along with whether or not you use a subwoofer (deep bass takes the most power.) 

Finally, keep in mind that the position of the volume knob is not an indication of whether or not you are at or near the amp's max output.  Here, the voltage output of the source and the input sensitivity of the peramp/amp play a big role. For example, a while back I tried using a unity-gain preamp with a low sensitivity power amp and having the volume knob turned to max only gave me moderate volume. I had to switch to a preamp with additional gain to get the sound I wanted, even though I did not change power amps. 

As you can see, lots of moving parts. But your first move is to figure out your desired listening level. 

In my experience for most speakers, the relationship between sensitivity and amplifier watts is often an overblown consideration. Gain, however, is predictable. Like others have stated you may have a gain issue. I do not know your preamp but 4-6 o'clock seems quite high already and a lower sensitivity is sure to make that more challenging. 

@lloydc Wrote:

Sensitivity 86 v 90

My question is, would the decreased efficiency be a concern?

No!

The two speakers have the same efficiency. Changing the impedance of the speaker will change the voltage sensitivity, not the efficiency -- the 4Ohm speaker is getting 2 watts from the amp, the 8Ohm speaker is getting 1 watt from the amp. That’s why the 4Ohm speaker has a 3dB higher sensitivity. (Ohm’s law) Sensitivity and efficiency are not the same. See below: Paragraph C. Hope that helps.

Also, what is the gain of the amp you have?

Mike

"Overcoming misinformation

One misleading piece of information with which our customers are often provided is sensitivity. This specification is commonly misrepresented as "efficiency" which it most certainly is not. Loudspeakers are terribly inefficient and it is likely that virtually no consumer has ever been given an actual efficiency specification. The most efficient loudspeaker designed to date was the Altec Lansing Voice of the Theater, which had an efficiency rating of approximately 3.6%. No loudspeaker manufacturer would ever publish an efficiency specification because it would discourage and mislead consumers. Be clear on one point: sensitivity and efficiency are not the same thing. Even when using a solid state amplifier, one cannot necessarily equate high sensitivity to high efficiency - the physics are simply more complex than many manufacturers, and sadly reviewers, lead us to believe.

Instead of efficiency, loudspeaker manufacturers provide a sensitivity specification. This figure is supposed to indicate how loud a speaker will play when fed one watt of power, or 2.83 volts, listening from one meter away. The problem with this measurement is that the conditions under which it is to be recorded are not well defined and hence the figure does not provide a consistent "apples to apples" point of reference. For one thing, the input sensitivity (gain) of the amplifier used to measure the sensitivity is unknown and unspecified. More importantly, while the specification calls for measurement at one meter away, the conditions of the listening room are not defined. It is not clear whether measurement is to occur in an anechoic chamber, a concert hall, a coat closet, or a gymnasium. Each of these rooms will yield remarkably different sensitivity readings at one meter from the speaker.

The most important lesson to learn from the above discussion is that for the purposes of determining tube-friendliness, sensitivity is essentially meaningless. Many tube gurus insist that one must use speakers with sensitivity ratings of 90 db or higher. This is simply not true. Many speakers with high sensitivity ratings are poor choices for tube amps, just as many speakers with low sensitivity ratings often work quite well. Why is this so? Read on…"

https://www.dhtrob.com/overige/tubefriendly_lsp_en.php

I went from JBL 4319 monitors rated at 92db efficiency, 6ohm nominal, 4.7ohm at lowest point to Atalante 3 monitors rated at 87db efficiency, 6ohm nominal, 4.4 ohm at lowest point and only have to increase volume 1- 1 1/2 db for the same results. Some reviewers are using 15 watt tube amps and getting wonderful results.

Even at the old normal listening level, I’m hearing more than with the older speakers. Just the SPL is lower. Without the cabinet and crossover, the drivers in the Atalante 3 are rated at 91db efficiency on their own. Turning the wick up to get the same scale and impact requires just a db or so to get there and it sounds more convincing in some respects but can sound too loud. Go figure.

I wished I had bookmarked a review where it was explained how efficiency is such a misunderstood measurement since no two speakers rated the same, perform the same and those that vary some will perform the same.

All the best,
Nonoise