Speaker sensitivity vs SQ

There are a lot of examples when amplifier has mixed SE and PP stages.
For example some SET amplifiers have first stage SRPP and PP amplifiers have SE first stage before phase spliter.
Another example - SE preamp and PP amplifiers.
Do all these amplithis have a prominent 5th harmonic in addition to a 2nd and a 3rd ?

In P-P amps what is concerning is what circuits are in the feedback loop. They will affect which harmonics have more prominence. IOW the topology affects the distortion signature. IMO a single-ended preamp can work alright with a balanced amp, but I'm not sure that is what you are asking as P-P amps cover quite a range of circuits!

@phusis The T-1 has a 250Hz horn, using a 4" compression driver that is field coil powered. The diaphragm is made of beryllium and employs a Kapton surround, which is how it goes so low without breakups. I don't know the spec on the T-1 but I do know that the 3" diaphragm in the T-3 has its first breakup at 35KHz. The breakups are a pretty big deal; I got to hear what the regular TAD diaphragm did compared to the CAL unit and it was not subtle- much smoother!

Some of the older Horn loaded speakers like Altecs and JBLs that I had a lot of experience with when I was young were all very colored. Back then K horns were the best but they did not image well and though not as colored as the other horn speakers you still knew you were listening to horns.

Like any other tech, horns have benefited dramatically from the aid of computer optimization. I owned Altecs, Klipsh and EV horn systems and there's no way I would go back to them; as you say they were very colored (and lacked bandwidth, particularly in the bass). The Classic Audio stuff is a different beast altogether- neutrality is a good descriptor. The speakers produced by Audiokinesis using waveguides had a similar neutrality- you found yourself involved with the music rather than the speakers.

@mijostyn  I don't know about Curl's designs so much, but Nelson does make fully differential amplifiers so he is able to take advantage of the lower distortion afforded, and yet have a nice 3rd to help mask the higher orders.

What are the T3’s sold for - close to $100k? Re: mentioned "better interface" it reminds of what Simon Mears told me of the importance of the coupling between the compression driver exit and the throat of the horn it’s mounted to; transition, transition, transition - as he put it.

@phusis As I understand it, my speakers are currently about $33,000/pair. Mr. Mears is correct. The coupling was optimized on a computer and the result is very smooth and seamless. People often comment on hearing T3s (and T1s) that the speakers sound more like ESLs in that they are so fast and seamless. IOW no ’horn artifact’ at all.


Regarding the SETs, IMO/IME their main advantage is that as the power is reduced, the distortion decreases linearly to unmeasurable. This is important because (to trot out an old expression) it really is all about that first watt. But just so you know, this character is not unique to SETs, although it is rare in push-pull amplifiers. But you can imagine since I’m writing this that I know of a few amps which share this important characteristic. But one **disadvantage** of SETs is that their primary distortion product is the 2nd harmonic, as well as low power and troubles making bandwidth due to the output transformer.


Now we all know that the 2nd harmonic is innocuous in that the ear is insensitive to it (and because the ear converts all forms of distortion into tonality, it assigns the quality of ’warmth’ and ’bloom’ to this one). However, the ear assigns this same quality to the 3rd harmonic as well, but there is an important distinction. Circuits that have a 2nd harmonic as their primary distortion product mathematically have what is known as a ’quadratic non-linearity’. Its not so important to know the math, but if you feel like working it out what you will see is that harmonic orders above the 2nd decrease rather slowly as compared to a circuit that has a ’cubic non-linearity’ (produces the 3rd as the primary distortion component). An amplifier that has this quality has its distortion decreasing much faster as the order of the harmonic is increased! This is important since the ear uses higher ordered harmonics to sense sound pressure (and assigns the quality of harshness and brightness to them). IOW, an amplifier with a cubic non-linearity will sound more detailed (because distortion masks low level detail) and **smoother** because the higher ordered harmonics are at a lower level.

In terms of circuit design an amplifier with this characteristic must be fully differential and balanced from input to output. In this way even orders are cancelled with each stage in the amp (instead of being compounded), leaving the 3rd as the primary distortion component, at about 1/10th what you would get with a single-ended circuit, assuming that neither employs any feedback.

Now if you mix single-ended and push-pull, you wind up with a prominent 5th harmonic in addition to a 2nd and a 3rd (put another way an amp like this has **both** cubic and quadratic non-linearities). This is why many people prefer SETs, but those same people find that if they hear an amp with similar concepts (triode, class A, zero feedback) executed fully differential, that it has all the desirable properties of SETs without a downside. BTW this difference is easy to hear (its not subtle) and of course its also easy to measure.

How would you compare them to the likes of JBL Everest’s (DD67000, or one of the other two variants), if you heard them?

I have. The Classic Audio Loudspeakers are **easily** in the same league. If I had to compare, the CAL is a bit smoother, owing to a better interface between the throat and horn, resulting in far less artifact. The field coil compression driver is also a higher performance bit of kit.

These are field coil-fitted drivers, right? In that presumable case their price, though way above what needs to serve a fitting purpose here, makes a little more sense.

@phusis 

They are TAD 1602s. Pricey, and a bit different from the EV. I forgot to mention they have Alnico magnets.FWIW the midrange driver employs a field coil and a beryllium diaphragm with a Kapton surround.  They are Classic Audio Loudspeakers model T-3. I had the cabinets custom-built by CAL to be a bit taller than stock so they are flat to 20Hz. 

Guys, it's simply not true to make a statement that a higher sensitivity speaker is more costly to make.  Drivers, cabinet material, R&D, spikes, connectors, wire, glues, finishes.... and of course how many points dealers get to sell them

Let's be clear about one thing: Sensitivity isn't the same thing as Efficiency and it really is the latter which is the focus of this thread. You can build a high sensitivity speaker by simply taking a number of low efficiency drivers and putting them in parallel. Cheap and high sensitivity, but its efficiency will remain low. High Efficiency cannot be achieved cheaply for the simple fact that there is a much higher degree of precision needed in the construction of the driver's motor.

The difference between Sensitivity and Efficiency: The former is 2.83Volts at one meter. The latter is 1 watt 1 meter. If the speaker is 8 ohms the two are the same. If we take four 8 ohm drivers that are 87dB and put them in parallel, the load is now 2 ohms. The sensitivity is increased by 6dB; 93dB doesn't sound too bad. But that is 2.83volts into 2 ohms; when you do the math that is 4 watts. If you put 1 watt into that same array you'll still get 87dB. A higher efficiency driver that can make 98dB with 1 watt and is 8 ohms is a different beast altogether. This describes the 15" drivers in my speakers at home and they cost $2000.00 each.


You can find 15" drivers that cost $200.00. I'd be very interested to learn of a 15" with the same 22Hz free air resonance and 150 watt power handling that cost $200, or even $600.00. Have at it! But I think you'll find that such simply does not exist.

My point is that dynamics are a matter of volume. A speaker that can hit 110dB without compression is going to be more dynamic than a speaker that can only get to 100 dB even if it is less. efficient. Just a matter of power. Horns are very dynamic because they go very loud. They do it with less power because they tend to be very efficient. As far as sound quality goes, it's a toss up.

Thermal compression occurs with all voice coils. The less efficient the driver, in general there will also be greater thermal compression as the speaker is being asked to deal with more power. As the voice coil heats up (which it does on each individual bass note; yes, they can heat that fast) its ability to move the speaker cone is reduced. Result: lower efficiency speakers tend to have lower dynamic qualities as well and unless you move away from a voice coil M.O., you can't throw more power at it, more power makes it worse. IOW the louder you play, the more compressed it becomes.

So there must be other factors. Why don't all speaker manufacturers build exclusively high sensitivity speakers?

@clearthinker  Cost, in a nutshell. High efficiency drivers are much more expensive due to a greater degree of precision required to precisely place the voice coil in a narrower gap, plus a more powerful magnet system.