Nope, more than that! There are at least three variants of KEF LSX extant, and LS60... and at least one other...
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Why would anyone use an AB amp for a tweeter?
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charlielaub
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Didn't wade through this entire thread but am posting my 2 cents, since this is something that I have considered myself (class-AB on tweeter, class-D for all other bands in a multichannel active speaker).
Cheap-er class-D amps, or maybe I should say those that use older technology, often have frequency response problems above 3kHz due to the interaction of the output filter with the load impedance. It's only relatively recently that better amps from Hypex and Purifi have become load-independent "up there". So you can get away with a less expensive class-D amp using older technology for all bands except the tweeter. Here is where class-AB would work great, since there is far less load interaction even with relatively low cost implementation. And of course the power demand in that band is lower as has been mentioned several times.
Sorry if this point was already brought up, but I am in a rush to do some Xmax related stuff!
Cheap-er class-D amps, or maybe I should say those that use older technology, often have frequency response problems above 3kHz due to the interaction of the output filter with the load impedance. It's only relatively recently that better amps from Hypex and Purifi have become load-independent "up there". So you can get away with a less expensive class-D amp using older technology for all bands except the tweeter. Here is where class-AB would work great, since there is far less load interaction even with relatively low cost implementation. And of course the power demand in that band is lower as has been mentioned several times.
Sorry if this point was already brought up, but I am in a rush to do some Xmax related stuff!
Yep it’s has been brought up , so nowadays you can get class-D modules that’s relatively load independent not only from hypex and purify .
KEF has compounded the normal issues by designing the LS60 with an upper fr response of 36kHz .
And typically class-D modules are limited to ca 20kHz for the filter and other design considerations ( Bruno P has stated that he rather optimise inside the audible band than make the designs more wideband ).
So I Guess there are limited suppliers that provides a 40kHz class D module , it’s not only the filter but also switching frequency et all involved ? So you then have to do some in-house development or contract that to someone else . I would further guess that developing a traditional small class AB amp is known entity, you can probably find it in a textbook.
unpluggged
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Interesting examples.
First the Nilai above maxes out worst case at -80 dB while the NAD is around that range entirely. Looking the other way, the Nilai is better in all other frequencies and powers other than 2 highest ones.
Second, as I have written a thousand times plus wrote a FAQ about it, the Nilai (Hypex and Purifi in general) did this on purpose. Better to have the feedback loop strongest where it is audible and let go where it is inaudible (2nd/3rd harmonics of 10 kHz are 20/30 kHz, of 15 kHz are 30/45 kHz, etc). Especially around 10 to a 100W in a tweeter, where musical signal is dozens of dB below full scale.
These examples just show good engineering at its best: solve a problem where it matters.
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Haskil
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Perhaps quite simply, the size, weight and heat release become problems in a space so constrained as a small acoustic enclosure, even if it is a column...
When we see the size of the cooling radiator of a class AB amplifier making 500 watts, when we see the size of the transformer to power it and that of the filter capacitors (which can admittedly be replaced by a switching power supply lighter)... I still wonder if resorting to class D is not a necessity...
Because the two amps producing the most power and the most heat are those dedicated to the bass and the midrange... and this Kef precisely contains a 500 watt amp for the bass and one of 100 watts for the midrange in class D ...
And when you produce on a large scale, the weight of each packaged unit is not such a negligible data...
So the reason would be economic-technical-logistical
And the 100 watt amplifier for the tweeter is not expected to deliver more than 2 or 3 at medium speed... so it does not need to be cooled as if it were amplifying the complete signal
When we see the size of the cooling radiator of a class AB amplifier making 500 watts, when we see the size of the transformer to power it and that of the filter capacitors (which can admittedly be replaced by a switching power supply lighter)... I still wonder if resorting to class D is not a necessity...
Because the two amps producing the most power and the most heat are those dedicated to the bass and the midrange... and this Kef precisely contains a 500 watt amp for the bass and one of 100 watts for the midrange in class D ...
And when you produce on a large scale, the weight of each packaged unit is not such a negligible data...
So the reason would be economic-technical-logistical
And the 100 watt amplifier for the tweeter is not expected to deliver more than 2 or 3 at medium speed... so it does not need to be cooled as if it were amplifying the complete signal
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JohnnyAudio
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I have tried A & AB with 4- AMT ESS H.F. drivers and subjectively the SET amps sound much better with AMT's.
Old_School_Brad
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Exactly what you were expecting, right?
I would say whatever KEF’s done with the LS60 I would not say that self nois is a problem IME , have had other active speakers hiss more like Adam or Fostex .
Galliardist
Major Contributor
Having caused the initial confusion, I've also been reading. The Australian website actually clearly states differently: for the LSX II LTthe secondary speaker is active, powered from the primary speaker. The LSX II is active with each speaker powered. It couldn't be any clearer:
LSX II LT
LSX II LT shares the same immersive High-Fidelity sound and key technologies as LSX II at a price you’ll love. Powered by KEF's Music Integrity Engine and signature Uni-Q driver array, this compact wireless HiFi speaker system delivers unparalleled sound clarity.
au.kef.com
Sokel
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Just out of technical fetish (far,FAR from audibility) it's reasonable for one to want an AB class amp up high,specially a low power one as the SINAD list top champions which against class D they maintain a straight line at the abysses of the chart up to ultrasonics.
However that's not the case with Kef amps I suspect as this straight line can probably be a lot higher.
That's how the myths sustain though.
Until we see a Purifi or a (as they promised) icepower Conductor doing the same up there the myth will go on.
And of course all that are technical,again,far from audibility.
However that's not the case with Kef amps I suspect as this straight line can probably be a lot higher.
That's how the myths sustain though.
Until we see a Purifi or a (as they promised) icepower Conductor doing the same up there the myth will go on.
And of course all that are technical,again,far from audibility.
Galliardist
Major Contributor
And the LSX II LT manual doesn't say anything about where the amplifiers are, at least not directly.
What it does say is that the signal sent to the secondary speaker is upsampled to 96/24, indicating a digital signal rather than analogue signal to the drivers.
What it does say is that the signal sent to the secondary speaker is upsampled to 96/24, indicating a digital signal rather than analogue signal to the drivers.
Galliardist
Major Contributor
What is the source for these figures?
True, I made an assumption and it's probably wrong, not the first or last time, I see the interspeaker USB c cable for the LT also provides power via PD3 as well as the digital signal.
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unpluggged
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The Sound & Recording magazine, obviously. It's well-regarded here as a source.
Galliardist
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Thanks. It’s always best to quote the source.
ZolaIII
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This is bridged 3.4 KW, tho stereo is far less impressive 950 Wx2.
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