Speakers with A/B class amplifiers for smoother tops ?

[niacin]

So looking at 10" speakers I came across some positive reviews for the Presonus Air 10s. The idea is you use a D class amp, light but powerful, for the mids and lows, and an A/B class amp for the top end, being heavier but relatively small given it's only driving a 1" HF driver, and the A/B class amp is supposed to give you smoother 'airier' highs. So I've been using a Line6 L2t, and just looked up the specs to see how much lighter the Presonus Air 10s would be, and whatdyaknow the L2t has an A/B class amp driving the 1", their advertising just doesn't highlight it at all. So I'm wondering if anyone can comment on the Presonus or their claim about A/B class amps producing a better top end than current class D amps, and any experience with the Pesonus Air series.

[J. Dan]

Marketing BS. Doesn't mean they aren't good and don't sound good. But class A/B compared to class D is dependent on the design and quality of each. You can't just say that in every case, one will be better than the other. If they want to go that far, why not class A?

[Dave Bryce]

Marketing BS. Doesn't mean they aren't good and don't sound good. But class A/B compared to class D is dependent on the design and quality of each. You can't just say that in every case, one will be better than the other. If they want to go that far, why not class A?

Yup. Plus, what drivers did they use? How's the cabinet tuned? Etc.

 

Marketing BS indeed.

 

dB

[J. Dan]

And I have to deal with marketing BS in my own world from my own company and call them out. It isn't always fun, but my position is kind of a liaison between the field and the factory. Our competitors use what we call as FUD (fear, uncertainty, and doubt) to promote their features. It COULD be better. It MIGHT be better, do you want to risk getting something else? At the end it's BS. So I always push back to my own employer to keep the straight and narrow and avoid all this.

[Al Coda]

I only know, a Class-D amp is a so called "digital power amplifier".

The main advantage is it´s theoretical 100% efficiency, less weight and easy exchange of power modules.

The main disadvantages are quantization errors and according to the Nyquist-Shannon sampling theorem, sub-harmonics as well as aliasing when operating/working frequency and/or sampling frequency is on the (too) low side.

 

Class A/B amps are good combo of Class-A and Class-B, analog and push-pull circuit.

While original Class A ´s efficiency is low (about 6% - 25%),- Class-A push-pull is about 50% and Class A/B´s efficiency is 50 - 78.5%.

No artefacs like the ones a "digital" Class-D amp can produce.

I put "digital" in double quote here because Class-D isn´t 100% digital.

As a simple description, it´s an analog power amp, a digital switching amp/PWM modulator and a reconstruction lowpass filter.

 

IMO the quality of different types of amps cannot be judged generally.

It´s build quality/price dependend.

A manufacturer can build excellent or worst Class A/B.

Same rules for Class-D.

Buy LAB Gruppen amps,- when you need that power,- and you´re fine w/ Class-D.

But they have a price !

 

One might find better Class A/B than Class-D in the lower priced marketing segments.

 

Not to forget to mention another important factor,- the service and costs.

It´s much easier to repair a Class A/B amp than a Class-D amp.

Class-D power modules are typically throw-away when they fail.

They will be simply exchanged and depending on what you bought, that might be nearly as expensive as buying a new amp.

 

Class-A/B better for highs in studio monitors ?

Can be or not, also depending on quality of construction and manufacturing.

 

But I see the trend active studio-monitor manufacturers more and more go w/ Class A/B again.

See Focal Alpha and Shape 65 for both the woofer and the HF,- and they have a very good reputation.

KRK RP4 and RP5 RoKit G3, Swissonic ASM5 and ASM7, M-Audio BX8D3,- just only a few.

 

To me, that indicates, for the lower priced monitors the Class-A/B might be the better amps while when needing more (Class-D) power and excellent sonic quality without any reconstruction artefacts, one has to grab deeper into the pocket.

 

A.C.

 

 

[niacin]

Yeh I had written the Presonus off as market hype until I found out the Line 6 also had an A/B amp and so I got curious.

 

Al, thanks for the very informative response. That all makes a lot of sense.

[Reezekeys]

I only know, a Class-D amp is a so called "digital power amplifier

Class D is not "digital."

 

This is a good explanation of the different classes of amplification:

 

https://www.soundonsound.com/techniques/what-class-d-amplification

[Al Coda]

I only know, a Class-D amp is a so called "digital power amplifier

Class D is not "digital."

 

This is a good explanation of the different classes of amplification:

 

https://www.soundonsound.com/techniques/what-class-d-amplification

 

I didn´t says it IS digital,- please re-read.

 

"They" (wikipedia p.ex.) call it "digital" because of the switching amp, PWM and reconstruction filter.

 

A.C.

[Reezekeys]

You are correct! "So called" you said. I'm actually guilty of thinking there was some kind of A-to-D involved.

[b3plyr]

Al Coda, as have others, has presented a lot of valid points. I have worked with Class D amplifiers for quite a while now, not just as a musician, but also in design as an electrical engineer. An old musician's tale is that they will never sound as good as a traditional power amplifier, particularly in harmonic distortion. Not true. For one, as Al Coda said, it is the quality of the amplifier that makes the difference. And of course the speakers, cabinet, and especially the crossover. Looking strictly at specs, and especially at marketing hype, is a waste of time. Listen to the amplifier and then make your judgement.

 

My K10.2s sound great. They are Class D, were not that expensive, and have a smooth response across the audio range. And I am comparing them with my studio Dynaudio acoustics BM15A 10" studio monitors - which are more traditional technology. Are they as pure sounding? Of course not, but they do hold their own and at much higher power levels.

 

niacin, all the advice given in this thread is dead on.

[Dave Bryce]

There is a decent amount of commonly held beliefs about Class D that is a holdover from days when they weren't as good as they are now - a lot of it dating back a few decades. The current crop of product is actually quite good. I've been through some blind testing, and I feel pretty safe in saying that most folks really can't tell which is which.

 

Plus, a lot like the DCO/VCO thing (both of which, as with the amps, are analog devices with one being under digital control) there are all sorts of flavors of both. Ever hear the VCOs from the OB-Mx? I'd rather have the DCOs from the JX-8P.

 

dB

 

 

[The Real MC]

Class D isn't "digital", it just looks that way because the switching transistors are always at either full on or full off. The audio signal is never in the digital domain; the audio signal is pulse encoded then reconstructed using a filter. Not too dissimilar from how audio is transmitted over FM radio.

[Al Coda]

You are correct! "So called" you said. I'm actually guilty of thinking there was some kind of A-to-D involved.

 

AD/DA conversion CAN be involved and eventually it is often even the customer doesn´t know.

 

The old (hi-end) amp designs introduce HIGH damping factor.

The damping factor of an amp controls the speaker´s excursion (cone/diaphragm),- the higher the better.

Class-D amps don´t come w/ high damping factors, so it has to be compensated by other technology, mostly digital ... DSP.

WHEN there´s a DSP in the signal path, there´s AD/DA conversion involved.

 

A.C.

[RudyS]

But there must be a reason they do this, AB-class for Hi's and D-class for lows. The by dB beloved L2t does the same thing. I don't think multiple companies would do this out of pure marketing.

[AnotherScott]

I don't think multiple companies would do this out of pure marketing.

Sure, multiple companies could do the same thing for pure marketing reasons. But I think you're right that that's not the case for Line6 using this kind of amp, because they don't seem to actually mention it as a marketing point anywhere on their promotional info.

[niacin]

But there must be a reason they do this, AB-class for Hi's and D-class for lows. The by dB beloved L2t does the same thing. I don't think multiple companies would do this out of pure marketing.

 

No, it's not just hype, there's a cost-benefit analysis that Al explained above:

 

"for the lower priced monitors the Class-A/B might be the better amps, while when needing more (Class-D) power and excellent sonic quality without any reconstruction artefacts one has to grab deeper into the pocket."

 

Which explains why Presonus, for example, use an A/B amp to drive the 1" in their cheaper Air series but not in their more expensive products where they use Class D amps, presumably with some more expensive DSP tricks that the customer pays for, the gain being lower weight and more power.