Why would anyone use an AB amp for a tweeter?

[JustJones]

I didn't see where the AOR said class AB sounded better than class D. What I read was for the "price point" they could get AB with better sinad than D. Using with the tweeter might have more to do with hiss.

 

[thewas]

On the other hand, if you are more of a skeptical mind and know KEF and their hyped products for decades, you may guess that they are simply not able to build a decend Class D amp for driving a tweeter.

I doubt they build any amp themselves which is not bad though since they are a loudspeaker company and its better to use external expertise in fields you are not long into.
If your personal "skeptical mind" assessment is their products are hyped and mainly due to marketing may it be like that, I personally enjoy their engineering seen at their recent white papers and objective measurements results which are some of the finest in the home hifi business market.

 

[unpluggged]

Focal monitors use class G for the LF and AB for the HF.

Many studio monitors use similar designs (ADAM, for instance). This could have something to do with tweeter hiss, but competently designed speakers don't hiss even with PWM amps.

 

[Galliardist]

If it's more cost effective then why isn't it used in the KEF LSX range? Why would you think a profit making company designs products based exclusively on engineering decisions? Maybe they used AB in this context as a marketing ploy aimed at audiophiles wedded to "AB is better"? There's an interesting split in the KEF LSX range with the KEF LSX II LT aimed at the non-audiophile streamer, and the KEF LSX II aimed at audiophile types (Roon capability, aux input for turntable, etc.,...) One wonders if KEF might introduce an LS60 LTD at a much lower price point?

The features left out of the LSX II LT, if removed from the LS 60, would probably reduce the price of an LS60 LT by the same amount. But that is a much lower percentage of the LS60 cost: so unlikely to sell in greater numbers as the LSX II LT might/should.As to why the AB amp isn't in the LSX range - they are powered according to the description, not active, so that would be a single class D amp?

 

[JustJones]

The LSX II has amps in each speaker and can be used wireless connection in the KSX II LT amps are only in one speaker with a usb c connection to secondary they aren't wireless.

 

[Mnyb]

All in all I do,like the LS60 as I own them . Even serius audio companies has some marketing woo woo , so one has to judge the total package.
They also make passive speakers with biwire terminals

We don’t know much about the BOM of the amp module and other considerations. The woofer module are speced the same as the one used in some of thier subs thou ?

 

[Sokel]

biwire

Would you ever except to even see the word in a Purifi specsheet?

https://purifi-audio.com/document/share/59/a82eb980-951a-4387-85ce-43caaa1e5c2e

 

[Galliardist]

The LSX II has amps in each speaker and can be used wireless connection in the KSX II LT amps are only in one speaker with a usb c connection to secondary they aren't wireless.

Missed that, which is a much bigger difference. Thanks. It makes an LS60LT even less of a value proposition I guess.

 

[Galliardist]

We can take the example of Marantz integrated amps as another A/B vs D point. The Model 40 could easily have been built using a Hypex module, but the company felt that an A/B amp was actually a better value proposition at that price point. They seem happy to use either class of amp based on the requirements of the product they are designing.

One requirement is always to sell the product, though.

 

[ZolaIII]

In simple terms all do not best example as there are even far better cheap plate class D amp's that will behave far better in the bass range.

AIYIMA A70 Mono Amplifier Review

This is a review and detailed measurements of the AIYIMA A70 Mono TI TPA3255 based class D amplifier. It was sent to me by the company and is on sale for US $116. The on/off and input type selectors have good quality feel to them as do the rotary controls. Right one is volume but left one had...

www.audiosciencereview.com

But in highs they inherit increase in noise.

https://www.audiosciencereview.com/forum/index.php?attachments/aiyima-a70-mono-hi-fi-amplifier-power-into-4-ohm-vs-frequency-distortion-measurement-png.400130/

And output capacity falls. There are filtered top end design which doesn't have problem and are much more coherent regarding output power but such cost money.
Now take a look of rather good old (refined) AB class text book example where that's been done good.

https://www.audiosciencereview.com/forum/index.php?attachments/yamaha-a-s701-stereo-amplifier-power-4-ohm-vs-frequency-measurement-png.375882/

And that costs less. For the mids it doesn't matter much really and 1 KHz dashboard is a king and even this Aiyima stands great there. Reason for having even 100W for a midrange are usually smaller and less efficient drivers.
I hope that illustrated explosion to you how and why.

 

[ahofer]

I would not be surprised if this was really marketing driven, given the likely inaudibility of the difference. But I’m not so familiar with the cost/performance curve for non-hypex class D, so could be legit as well.

 

[Vacceo]

The features left out of the LSX II LT, if removed from the LS 60, would probably reduce the price of an LS60 LT by the same amount. But that is a much lower percentage of the LS60 cost: so unlikely to sell in greater numbers as the LSX II LT might/should.As to why the AB amp isn't in the LSX range - they are powered according to the description, not active, so that would be a single class D amp?

I hope that at some point, KEF releases a renewed version of the LSX with 12th generation UniQ and metamaterial.

 

[Mnyb]

I would not be surprised if this was really marketing driven, given the likely inaudibility of the difference. But I’m not so familiar with the cost/performance curve for non-hypex class D, so could be legit as well.

I'll guess that one market driven decision is to make it flat up to 36kHz ? Excludes most class-D plate amps . But reels in the HiRez audio crowd .
If their customer base plays source material with content >20khz and has decided so willingly . Then i think many loudspeakers mfg tries to make thier product go quite high up in the treble possibly useless but their customer thinks otherwise .

 

[574stereo]

For those of you doubting the post from 'AOR', Jack Oclee-Brown (VP of Technology at KEF) says the same in the Darko Audio podcast.

Listen from 27 minutes onwards.


Seems like they'd prefer to try and put Class AB in if possible, but there isn't the space (PSU, 700w of power + DSP + drivers generating heat in a slim enclosure). He discusses using an AB amp for the midrange driver but heat was a restriction.

No speaker company build their own amps,they are all of the self.
Here's one of what Genelec uses:

https://www.ti.com/lit/ds/symlink/lm1876.pdf?ts=1712744355761&ref_url=https%253A%252F%252Fwww.google.com%252F

Tottaly of the self ones.
Look at the suggested applications


View attachment 415688

So?

ATC are building all their own class A/B amplifiers in-house. As far as I know almost all their active models use more or less the same circuit design as the P1 and P2 amps but with different amounts of power on hand.

 

[Sokel]

ATC are building all their own class A/B amplifiers in-house. As far as I know almost all their active models use more or less the same circuit design as the P1 and P2 amps but with different amounts of power on hand.

You're right,I forgot about these ones and probably there's others too.

 

[ZolaIII]

I would not be surprised if this was really marketing driven, given the likely inaudibility of the difference. But I’m not so familiar with the cost/performance curve for non-hypex class D, so could be legit as well.

On high enough level self noise of let's say bad class D one's with not so good SNR on path from tweeter's is audible even in far range setup. Given real content even 8 KHz is high enough regarding overtones and 12 KHz is certainly enough for almost anything.
Regarding economics the cheap plate class D done properly that it doesn't get EMI and is filtered will do low end just fine and doesn't have even to perform very good but you need the power/$. Even good cheap class D amp will be more than good enough for mids and it's not like that Yamaha active speakers with class AB amps cost much more than one's with cheaper class D (especially when you count off cost of AC/DC convertor) competition so stage itself doesn't cost that much.

 

[574stereo]

You're right,I forgot about these ones and probably there's others too.

PSI as well I think. There are others too I'm sure...

 

[KSTR]

15 years ago, there simply were no small usable class-D amps (chips or ready-mode modules) that sounded good, that's why many studio monitors deployed class-A/B for tweeters. And larger modules were a) oversized and b) often even sounded worse.

I myself had the pleasure to spec and co-develop class-A/B modules as drop-in replacements for ICEpower 250ASP and 200AC modules, with 1/4th of the power of the modules (which run BTL, whereas our linear module was SE output).

These days, things have changed quite a bit, recent class-D chips are much better and modules have improved as well and are offered in reasonable wattages.
So today, IMHO, pushing class-A/B for tweeters is more a marketing thing ("our customers expect tweeter amp to be A/B") than a technical one.

 

[Mal]

KEF ... you may guess that they are simply not able to build a decend Class D amp for driving a tweeter.

Guessing isn't very scientific.

Subjectively, my KEF LSX has a decent tweeter, at least I've been listening to it for two years and am, mostly, happy with it. Objectively, you have measurements in ths forum, and Atkinson, over at Stereophile indicating it's decent - not perfect - but what is?

 

[GXAlan]

So today, IMHO, pushing class-A/B for tweeters is more a marketing thing ("our customers expect tweeter amp to be A/B") than a technical one.

Agreed, although the question of “today” is worth thinking about. The LS60 launched in 2022 but the LS50 Wireless 1 was from 2016, so perhaps the amplification goes all the way back to 2014. So, the R&D may go as far back as 2012. Factor in supply chain and long term agreements…