Speaker advice redux?

Oh man, I'd hate to have to make this decision. My wallet made my decision for me.

My knee jerk reaction would be to say get the Harbeths. On the other hand, the Minuets are very nice. I have a pair.

I also listen to a very wide range of varying types of music and I have been on the hunt for the "perfect" speaker for me.

Just to play devil's advocate, I'd say that the Harbeths are a good bit less efficient. Just going by the specs, the Minuets should play about twice as loud for any given amount of power, for the times when you can. The Harbeths are also rated pretty low for power handling, at 50 watts. The Minuets are rated at up to 300. I also didn't like the Harbeths playing rock music, although they did everything else very well.

The Harbeths also don't go as low as the Minuets do. I often run my Minuets without a sub and don't miss it at all. When I do run a sub, I have it crossed over at 50hz, for what it's worth.

I think that I would characterize the Harbeths as being very civilized. They don't play all that loud and they don't go very low, but they sound excellent with what they can do.

The Minuets are a great bang for the buck speaker. I've had Dynaudios, Paradigms, System Audios, etc. and the Minuets have sounded the best in my room. What I've found with them is that they sound good no matter what. I mean, I can set them up to sound really good, but they sound at least good regardless of how I set them up. They are very forgiving.

To tell the truth, I feel kind of silly recommending the Minuets over a pair of Harbeths, but the Harbeths just weren't for me, although I will acknowledge that they are recognized as being a better speaker.

If you can afford the Harbeths, I'd recommend finding a used pair of Minuets. You can get them for $500 and under. Then I'd find a used pair of Harbeths and get those too. If you decide that the Harbeths are for you, then stick the Minuets in storage because everyone should have a pair at their price.

If the Minuets are for you, you can sell the Harbeths.

For their price and the countless number of hours that I've enjoyed the little Minuets, I cannot fault them for anything. Hours literally fly by when I'm listening.

"A speaker is either able to resolve details better than another one or it's not, level isn't going to change that."

That is true in many cases, and would probably be true in all cases if the spectral balance didn't change with volume level. But sometimes that is what happens. Let me give a hypothetical example that illustrates what I'm talking about. I'm going to make some simplifing assumptions here, to keep this hypothetical from getting too complicated:

Suppose we want to design a compact speaker with decent bass, so we choose a beefy little 83 dB efficient 5-inch woofer that has some serious low end going on (honest 40 Hz in about 1/4 cubic feet). Power handling 50 watts RMS, 100 watts "music program", 200 watts peak. And because we want good resolution, we choose a nice little 90 dB efficient 1" dome tweeter, same power handling characteristics as the woofer.

The problem we run into is thermal compression. As a ballpark generalization, a speaker will have about 1 dB of thermal compression at 1/10th its RMS power handling, increasing to about 3 dB at its RMS rated power handling, and going up from there.

The woofer will see far more power than the tweeter, since the tweeter will be padded down to level-match with the woofer. So let's say we "voice" our little speaker to sound correctly balanced at 97 dB, which corresponds to 50 watts input. Our woofer is seeing nearly the full 50 watts, and our padded-down tweeter is seeing a little over 2 watts. So at 97 dB, our woofer is exhibiting about 3 dB of thermal compression (that's why it isn't giving us the full 100 dB we would otherwise expect), and our tweeter isn't exhibiting any thermal compression at all. So instead of being padded down the 7 dB we might expect based on the efficiency difference between the two drivers, we have padded down the tweeter by 10 dB, so that the spectral balance is correct at high sound pressure levels (97 dB ballpark).

So, what happens at low levels, say down at 85 dB or less?

Well, at low levels, neither woofer nor tweeter are seeing enough power to exhibit any significant thermal compression. But remember that we had to pad down the tweeter by an extra 3 dB because we wanted the speaker to sound good at 97 dB. So now, at low levels, the tweeter is 3 dB too soft relative to the woofer! As a result, our killer little speaker sounds dull and lifeless at low levels - you have to hit it with a lot of power before it "wakes up"!

Now this isn't really a change in resolution per se, but it can sound like a change in resolution, because the treble range - which conveys the little details and nuances - is subdued relative to the rest of the spectrum at modest SPLs.

What would happen if we didn't pad down the tweeter by that extra 3 dB? Well it would sound correct at modest levels, but then at high levels it would be too bright, and especially so on peaks. (The correct solution, imo, is to do a better job of matching up the real-world thermal characteristics of woofer and tweeter... but then this hypothetical example would fail to illustrate my point.)

As mentioned early on, I have made some simplifying assumptions here, but the general principle is valid: When you have a large discrepancy in the thermal headroom of the woofer and tweeter, the spectral balance may change significantly as the volume level changes significantly.

Duke
dealer/manufacturer

Sorry I wasn't clear, Bob! Let me try again.

First a bit of background that I left out: Thermal compression is caused by the voice coil heating up which causes its resistance to rise (there are other bad things that happen as well, but this is the main one). As the resistance rises, progressively less wattage goes into moving the voice coil, and progressively more wattage goes into further heating the voice coil, so it's a viscious cycle. Normally thermal compression is negligible until we get up to maybe 1/10th the driver's RMS power handling, then it starts to accelerate rapidly, often reaching 3 dB at full rated power. In the example I gave in my post above, the woofer is subject to significant thermal compression but the tweeter is not.

It might be easier to visualize how this can make the speaker's spectral balance change with level if we start out at low SPL, using the same 83 dB, 50 watt woofer and 90 dB, 50 watt tweeter as before:

Let's say we start out with woofer and tweeter level-matched at 1 watt (83 dB). Since the tweeter is 7 dB more efficient that the woofer, we have padded it down by 7 dB in order to match the levels.

Now if we go up to 50 watts, we would expect both the woofer and tweeter to deliver 100 dB. But the woofer in our example loses 3d B to thermal compression (due to the voice coil getting very hot), so it only gives us 97 dB, while the tweeter is still delivering 100 dB. So the speaker sounds bright at high SPL.

If we wanted to "voice" the speaker to sound correctly balanced at 50 watts, we would want the tweeter to also deliver 97 dB. We do that by padding the tweeter down by an additional 3 dB.

But this additional 3 dB of padding on the tweeter needed to level-match at high SPLs results in the tweeter being -3 dB relative to the woofer at low SPLs, where thermal compression is negligible.

If it's still unclear, let me know and I'll try again.

I first became aware of thermal compression when listening to a well-respected three-way speaker (which cost more than my car) that sounded overly laid-back at at low and medium levels, magnificent at fairly high levels, and forward and harsh at very high levels. In this case, the woofer and tweeter were suffering from thermal compression, but the midrange driver was not (it was the "showpiece" of the system). Since then I've noticed the effects of thermal compression on spectral balance in more speakers than I can remember. It's most noticeable when a speaker gets bright or harsh or too forward-sounding at high SPL, and is most common when a high-efficiency tweeter is paired with a low-efficiency woofer.

Duke