Sensitivity question

We  mustn't confuse or obfuscate these two factors even though both determine whether a given amplifier will drive a give speaker satisfactorily.

Resistance, ohms, of a speaker is the main determinant of how hard it is for the amplifier to drive it without distortion.   A statement that a speaker 'is' say 8 ohms is a subjective judgement of the lower ohm areas of its impedance curve plotted against frequency.  A 4 ohm or less speaker will need an amplifier with a stiff power supply, not merely large but, more importantly, not weakening when asked to drive a low frequency at a low resistance.  The amplifier's output in watts is not the most important issue here, although high power amplifiers tend to have big strong power supplies.

The dB measure of a speaker is how efficient it is - how much sound you get for each watt put in.  83db is very low.  You need a lot of watts to drive it to high sound levels.  Conversely a 100dB speaker is very efficient and a few watts will drive it very loudly.

The following will help advance the answer to your question, which some above have touched on. https://audiojudgement.com/speaker-impedance-curve-explained/

I drive a pair of 83db speakers with a class A 28wpc amplifier. Normally I would have never even thought to do this but since we do audio repairs, the amp came in and to test the repair we hooked it up. It drove the speakers better than many other amplifiers we typically would use. So give it a try and see what happens.

Happy Listening.

@bluorion,👍

Thanks for all the great responses---it was a huge help! @ditusa Great article!! 

Hoffman’s Iron Laws of Speaker Building

1) Bass Extension

2) Efficiency

3) Small Enclosure

The law is that you can only have two of these three attributes in speaker building.  Ideally, we would want all three, we want speakers with good bass, can play really loud, and are small.  Unfortunately, we cannot have all these.

@bluorion Wrote:

 

Sensitivity question

See article below:

Mike

https://geoffthegreygeek.com/understanding-speaker-sensitivity/

@johnk +1

Mike

Your 23wpc class A amplifier should have no problem driving a 10 ohm speaker. How loud the experience is dependent on room size and distance one sits from speakers. 

It will work fine just will sound small and have limits on peak SPL. After all, you selected a small speaker and lower power. You picked your limitations.

You seem to be mixing concepts. "hard to drive" is usually reserved for speakers with very low impedences in certain frequency bands that need very high current. Not the same as sensitivity

Low sensitivity needs more watts of power, but isn’t necessarily hard to drive.

High impedence means less amps required and generally requires less current for the same watts.

Now if you’re looking for a speaker to pair with an SET at low wattage, the only thing you really need to look at is sensitivity. Then check that it isn’t one of the "problem" speakers that has impedence dips. 4 ohm or even 3 ohm is fine for most amps (the amp manufacturer will warn you if it is designed for 8 ohm only). Infinity speakers, especially the Kappa’s are known to have very low impedence dips and thus require huge currents and are very "hard to drive’. Lesser amps tend to fry.

If you're trying to match to a 23 wpc amp, you might look for 90 and above but 88 may work.  Do you listen loud?  Check that the 88 is not a "problem" load.  

Jerry

8 ohm speaker rated at 88dB will produce 88dB/W at 1m distance.  At 2m it will drop to 82dB/W, but room reflections add 3dB and second speaker adds another 3dB, resulting in 88dB at 1W.  At 23W they will produce 102dB - should be loud enough.

Sensitivity is specified at 1W or 2.83Vrms.  It is the same with 8ohm speaker, but specifying 4ohm speaker at 2.83V (2W) shows better (by 3dB) sensitivity in specs.

Speaker's nominal impedance is specified usually at 1kHz, but might vary a lot at different frequencies.  As you stated lower impedance speaker is a little harder to drive, but the same goes for speakers that have impedance dip at certain frequencies.  My amplifier is specified for >2ohm speakers, while my 6ohm speakers' minimum impedance is 3.6ohm - so I'm OK.

Good question,

my instincts are: only in a small space, i.e. 10 x 12.... like an office, den, ..., but not enough power/enough volume for a large space where the listening position is likely to be further away.

Combining with a self-powered sub or two subs combined could work in a larger space.

You need to get the bass load off the amp, so it only needs power for upper bass/mids/highs which need much less power than low bass.

That means line out of the amp to the sub(s), then line minus low bass from the sub(s) back to the amp. Now, amp receives no low bass, doesn’t need power for that, AND the small speakers do not have to make low bass, thus they probably will sound better.

small space, I would probably use one in-expensive sub, just to get the load off the amp and add just enough bass so the main speakers do not sound small. Unaware of sub until you turn it off.

larger space, a stereo pair of self-powered subs, better quality, front firing, located adjacent to the mains. Very low bass may start mono, but the overtones quickly become directional.