Is Logitech Z-623 the true successor of Logitech Z-2300?


Well-Known Member
Oct 5, 2010
In the Haze..
Logitech Z-623

Logitech Z-2300

Even though Z-623 is touted by Logitech as the successor of Z-2300, I personally believe it does not packs the punch or have enough performance in it to be in the same league of Z-2300, let alone beat it. My beliefs were confirmed when my friend bought a Z-623, who also happens to owns a Z-2300. We did a full day audition of the Z-623 & compared it with the Z-2300 in every possible way, be it acoustic performance, quality of hardware used or just looks.


Z-2300: When Logitech introduced Z-2300 way back in 2004, it was a THX certified premium quality top of the range product. The Logitech engineers in the lab where given a clear goal i.e. to create the ultimate 2.1 multimedia speaker system in the world. They were not concerned about the price, they were more concerned about the performance & quality of the system which lead in using premium quality components, be it electronic components, speakers used, wooden casings of the subwoofers, plastic casings of the satellites and even the wires used to connect the components. Price was never an issue, performance was. This single mindedness of the engineers produced a unique product, and Z-2300 was born.

Z-623: Logitech introduced Z-623 in 2010 six years after Z-2300 reign. Actually I cannot recall of a 2.1 PC speaker that remained at the top of the performance charts for straight six years. They had to make the successor not because Z-2300 was getting old and becoming incompetent, believe me it is still is the king, but because the rival manufactures like Altec Lansing, Edifier, Creative, Sony etc are producing cheaper sets which claim to have the same power & performance of Z-2300 while using cheaper materials and then labeling them as their premium products. Also 2.1 speakers sets are no more the cash cows of audio manufactures, rather these companies makes a lot of profit from selling the 5.1 & 7.1 speakers sets.

Thus, I believe this time the engineers were given a strict goal during the designing phase, i.e. to make a speaker set that beats its opposition like Altec Lansing MX-6021, Sony SRS DB-500, Edifier S530 or Creative Gigaworks T3 by a small margin. Z-623 was not designed to reach the same level of acoustical performance of Z-2300, let alone beat it. After all there is no need to provide Z-2300 levels of performance when Z-2300 itself will be discontinued.

Also from the marketing point of view Z-623 having the same performance level of Z-2300 was useless since any marketing division want a system that is better than their oppositions, so they can advertise that and get the propaganda.
Consider the case of these two 200W RMS 2.1 speaker sets.

Let us assume that Altec Lancing uses hardware worth $80 and have assembling cost of $10 per set of MX-6021 and sells it at $150. Profit = 150 (80+10) = $60

Suppose in order to beat AL MX-6021, Logitech uses hardware worth $90 and have assembling cost of $10 per set of Z-623 and sells it at $150. Profit = 150 (90+10) = $50

So, Logitech gives hardware worth $10 more thus having more performance than MX-6021 at the same price in order to garner more sells at that price range.

Now, if Z-623 was supposed to beat Z-2300, then Logitech would have to use hardware worth $120 and have assembling cost of $10 per set of Z-623 and sells it at $150. Profit = 150 (120+10) = $20

So, Logitechs profit margin would have fallen from $50 to just $20 per set. And since Z-2300 will be discontinued & the current speaker sets having way below performance level than that of Z-2300, $50 profit per set was found more of a sensible option and correct from the logical point of view. If I was at the helm of Logitech I would have done that too. Unfortunately for customers, what they get is a good product but not an excellent one like Z-2300.


Audio Quality Certification: THX certified
Total Continuous Power(RMS): 200W
System THD: Better than 0.05% before clipping
Total Peak Power(RMS): 400W
Power distribution: 120 W (Subwoofer) + 2 X 40 W (Satellites)
Subwoofer: 120 W @ 8 ohms
Subwoofer Size (inch): 8
Satellites: 80 W (2 X 40 W) @ 8 ohms
Satellite Size (inch): 2.5
Frequency response: 35 Hz - 20 kHz
Signal to noise ratio(SNR): @ 1kHz > 100dB
Sound Pressure Level (SPL): 117db
Subwoofer dimensions(HWD): 11" X 11" X 15"
Satellite dimensions(HWD): 6.75" X 3.5" X 6"
Total weight : 15 Kg

Audio Quality Certification: THX certified
Total Power(RMS): 200W <-- Continuous or Peak Power ? No Mention. Why?
System THD: No Mention. Why?
Total Peak Power(RMS): ????
Power distribution: 130 W (Subwoofer) + 2 X 35 W (Satellites)
Subwoofer: 130 W @ 8 ohms
Subwoofer Size (inch): 7
Satellites: 70 W (2 X 35 W) @ 6 ohms
Satellite Size (inch): 2.5
Frequency response: No Mention. Why?
Signal to noise ratio(SNR): No Mention. Why?
Sound Pressure Level (SPL): No Mention. Why?
Subwoofer dimensions(HWD): 12" X 11" X 10"
Satellite dimensions(HWD): Unknown
Total weight : 10 Kg [5 kg lighter than Z-2300]


Frequency Response: Frequency response is the measure of any system's output spectrum response to an input signal. Humans are able to hear any sound between 20Hz to 20kHz. Any multimedia speaker system that can cover this entire range is regarded as a great achievement for the manufacturer so that the user can hear each &every note of the music playing.

While it is quite easy to go up to 20kHz to produce high frequency (treble), a manufacturer have to spend a lot of money in the hardware department in order to go way down in the frequency spectrum and reach 20 Hz (Bass). To produce frequencies at 20 Hz you need a bass driver which is at least 12 inch or more in diameter and also have lots of power from the amplifier to power that driver in order to move huge volumes of air.

Since Z-2300 uses a 8 inch bass driver it can go as low as 35Hz and its frequency response is in between 35Hz20kHz which is quite a respectable figure. For Z-623 there is no mention of frequency response of the set in their website. Why? Is it because Z-623 7 inch bass driver being an inch shorter than Z-2300 was not able to go as low as 35Hz as in Z-2300 could have and hover around 45-50Hz? I think so.

System THD: The total harmonic distortion (THD) is there to give us a measure of how much the audio signal is distorted when playing the system. Z-2300 had better than 0.05% THD before clipping which was excellent from acoustical performance point of view. In Z-623 there is no mention of these criteria in their website. Why? Is it because Z-623 THD is nowhere near that of Z-2300? I think so.

SNR: Signal-to-noise ratio (SNR) is a measure used in science and engineering to quantify how much a signal has been corrupted by noise. It is defined as the ratio of signal power to the noise power corrupting the signal. Z-2300 had hifi level 100dB SNR which was way better than 70-80 dB SNR its opposition was able to manage. For example, Altec Lansing MX-6021 have only 75db SNR. For Z-623 there is no mention of these criteria in their website. Why? Is it because Z-623 SNR also hovers at around 75dB and thus nowhere near that of Z-2300? I think so.

Continuous Power (RMS): For Z-2300 Logitech clearly stated 200W RMS of continuous power & 400W RMS of peak power. This means the Z-2300 was almost always able to continuously deliver 200 watts of distortion free power all the time. For Z-623 Logitech just states 200 W RMS of power. No mention of continuous power or peak power in their website. Why? Is it because Z-623 was not able to match the power output of Z-2300? I think so.

Weight: For multimedia speaker systems, weight is an indicator of good, robust design because it suggests that the speakers are made of thick MDF, have big drivers (speakers) with large magnets in them to handle lots of power from the amplifier, and therefore have plenty of capacity. Also weight is an good indicator for the internal amplifier because it suggests that the amplifiers important internal components--the power transformer, heat sinks, and storage capacitors -- are large, and therefore have plenty of capacity to process and store large amounts of power to handle loud dynamic peaks without distortion.

Z-623 is 5 kilograms lighter than Z-2300. I mean you can buy a moderately good 2.1 speaker system which weighs 5 kg. It also much smaller than Z-2300 and a space saver too, but if you look purely from an acoustical performance point of view of any sound systems generally the bigger & heavier becomes the winner. Why? Let me describe


Z-2300: The subwoofer is huge, in every sense of the word. The behemoth measures 11 (H) X 11 (W) X 15 (D), and its output could both rattle the paint off your walls & take the wind out of your lungs at the same time. The enclosure is very deep, which is great from an acoustical performance viewpoint. The subwoofer weighs 12 kilograms and is a back breaker for sure.

Actually, this subwoofer was originally designed way back in the year 2000 for Z-560 which was the first THX certified multimedia speaker system from Logitech. This Holy Grail subwoofer was so good that Logitech kept this design and used it in all their THX certified speaker systems for the last decade as mentioned below:
Z-560 [first THX certified 4.1 system from Logitech]
Z-680 [first THX certified 5.1 system from Logitech]
Z-2200 [first THX certified 2.1 system from Logitech]
Z-2300 [second THX certified 2.1 system from Logitech with minor updations on Z-2200]

The wall of the sub is made of 16 mm thick medium density fiberboard (MDF) which is quite impressive. It has been further strengthened with internal clamps in the joints. This adds tremendous strength to the box in order to withstand the slamming, heavy duty sound waves produced by the bass driver.

Z-2300 uses a massive 8 inch long throw 70W Tang Band (W8-670Q) front facing bass driver. The driver is impressive and the bass it can provide is truly phenomenal. This driver has satisfied every bass freak out there for the last decade. The subwoofer also houses a patented U shaped exponentially increasing bass reflex port. Aesthetically, Z-2300 subwoofer is much better looking with its silver & black tones than the hideous full black Z-623s subwoofer. I especially liked the grill cover of Z-2300 driver than the protruding one of Z-623.

Z623: The Z623s subwoofer is two thirds the size of Z-2300. It measures 12 (H) X 11 (W) X 10.5 (D). Logitech kept the height & width almost identical but the depth of the box was drastically reduced by near 5 inches. From performance aspect this can never be considered a positive, since at least for subwoofers the simple theory of The Bigger the Better hold absolutely true.

From a technical point of view, Z-623 does not need a subwoofer enclosure as big as Z-2300 since the bass driver is an inch smaller in diameter measuring 7 inches and thus requiring a lot less volume of air inside the enclosure. But in return, Z-623 subwoofer will be much less powerful as compared to Z-2300. I think the 7 inch bass driver have a rated input power of 50W RMS [100W MAX] if you consider the 8 inch bass driver of Z-2300 was rated 70W RMS [140W MAX].

What I found amusing is that Logitech states this 7 inch bass driver can is capable to handle 130W RMS of power from the amplifier when the 8 inch bass driver of Z-2300 was always on overdrive mode handling its 120W RMS. This is the biggest proof that there is something fishy about the stated power of Z-623 & the amount of bass produced by the subwoofer or its loudness have substantially reduced by a good margin.

Also, the Z-623 subwoofer is nearly 4 kilograms lighter than Z-2300 sub. Where does this 4 Kilos go? Just vanished? Or is this is due to a smaller bass driver with a smaller magnet being enclosed in a smaller subwoofer enclosure with a thinner wall thickness than that of Z-2300?


Both Z-2300 & Z-623 uses 2.5 inch polished aluminum phase plug drivers in their satellites. Z-623s satellites are complete black units and are plain ugly, where as Z-2300s satellites with silver & black tones are beautifully crafted and looks like a piece of art.

The drivers of Z-2300 are 12W units made by Tang Band (W3-594SB). The combined weight of Z-623 satellites is nearly 600 grams lighter than Z-2300. Z-2300 satellites weighs 300 grams more per satellite since the construction of the box is way superior to Z-623 and the plastic wall thickness is more than that of Z-623.


Both Z-2300 & Z-623 houses the amplifier in their subwoofer assembly.

Z-2300: The amplifier module in Z-2300 uses four Class-AB STMicroelectronics power amplifiers.
The amplifier uses:
i) Two STMicroelectronics Class-AB, 80W, TDA7295 amplifiers bridged together to provide a total of 2 X 80=160W for the subwoofer.
ii) Two STMicroelectronics Class-AB, 60W, TDA7296 amplifiers powering each of the satellites.
iii) A Japan Radio Corporations JRC-4565 operational amplifier required for the headphones in the control pod.
iv) Filtering of the audio signal is done by two beefy SamXon/ CapXon 10,000 uF, 35V capacitors.
v) The amplifier board have two voltage regulators/ stabilizers a 78M18 and a 79M18, making positive and negative 18 volts respectively.

The amplifier is powered by a toroidal transformer made by Ten Pao International. Judging by the size of the core and the thickness of the wire in the secondary windings, the power is very decent. A toroidal transformer uses a doughnut shaped core & is much slimmer than a conventional (EI) transformer and at the same time at around 50% more expensive than a conventional transformer. A toroidal transformer has so many performance advantages over conventional transformer that it is hard to describe here other than to provide the performance ratio. Toroidal : Conventional :: 158 : 5

There is a heatsink located at the back of the subwoofer to cool the amplifier that pumps 200 watts of continuous power. There is a slow blow fuse found at the back of the subwoofer of Z-2300 along with a master power switch.
Overall I am highly satisfied with the design, detailing and high quality components used along with the built in safety features of the amplifier.

Z623: I am unable to give you a clear detail of the Z-623 amplifier, since my friend was reluctant to open the newly purchased set, which is quite understandable. But minutely looking at the subwoofer, I found out that there is no slow blow fuse.

Also surfing the net I found out Logitech have completely replaced the Z-2300s 200W Class-AB amplifier module powered with expensive toroidal transformer with cheapish Class-D amplifiers powered by switch mode power supplies (SMPS) as found inside our computers.

Just consider the case of Z-2300, which uses two Class-AB TDA7295 amplifiers bridged together to provide 160W for the subwoofer. Since these amplifiers will produce a lot of distortions at peak output & not comply with THX specification they are limited to just 120W for the subwoofer. So, we find that Z-2300 have a lot of headroom (160-120=40W) in the amplifier department & delivers THX certified clean undistorted power to the bass driver even at full volume.

The trend to Class-D was first started by Logitech in Z-Cinema which was a hybrid Class-AB/ Class-D. Now if, Logitech have used the Philips TDA8920 100W Class D amplifier for the subwoofer as in Z-Cinema (and there is a high possibility) the actual power supplied to the subwoofer may be 70W since Class-D amplifiers will produce even more distortion than Class-AB equivalent and needs even bigger headroom (100-70=30W) in the amplifier department in order to deliver THX certified clean undistorted power to the bass driver at full volume.

Also, 70W power to a 7 inch bass driver is quite understandable & justifiable but Logitechs claim of 130W power to that driver is completely unjustifiable.


Considering the case of Logitech Z-Cinema claimed 200W, I dismantled it myself and found out
1) One Philips TDA8920 100 watts Class D amplifier for the subwoofer.
2) One Philips TDA8922 50 watts Class D amplifier supplying 25W to each of the midrange speakers of the two satellites.
3) One STMicroelectronics TDA7269 20 watts Class AB amplifier supplying 10W to each of the tweeters of the two satellites.

Total maximum continuous amplifier power of Z-Cinema is 100 + 50 + 20 = 170W, where as
Total maximum continuous amplifier power of Z-2300 is 2 X 80 + 2 X 60 = 160 + 120 = 280W

For Z-2300, Logitech put the maximum continuous amplifier power down from 280W to 200W in order to provide a 80W headroom for the amplifiers & to comply with THX certification and was able to deliver clean undistorted sound even at full volume.

If you consider the Z-Cinema having maximum continuous amplifier power of 170W, they have to provide at least 50W headroom in order to provide undistorted power at full volume & to comply with THX certification. So, actual power you get in Z-Cinema is 170 50 = 120W.

But, the new trick currently followed by speaker manufactures are in stating the unrealistic peak power of a system which happens to be two times the continuous power, So the Z- Cinemas peak power = 2 X 120W = 240W.

Now it is even better for a manufacturer neither to state the actual continuous power or the peak power, but rather just provide a output power figure between these two and term it as Power Output.

For Z-Cinema,
Continuous Power: 120W
Peak Power: 240W
Manufacture claimed Power Output: 200W

Now, you get the picture. I personally believe that like Z-Cinema, Z-623 also has at around 120W and nowhere near the 200W real power of Z-2300.

So, now you can see why Logitech is not clear in stating its actual power. But I do not find Logitech guilty for this reason since every other manufacturer be it Altec Lansing, Sony, Edifier or Creative are all following the same path, Sony being the worst example with their 300W claim for DB-500 speaker set which actually have only 100W according to a much respected website.

Also there is no need of external heat sink for Class-D amplifiers, thus Z-623 does not feature one.


A quick look at many new low power speaker amplifiers on the market highlights the move to class D audio performance, but when it comes to low distortion and low noise and best sound quality, class AB still has the edge.

Class AB architecture offers a signal to noise plus distortion ratio of up to 10 times better than its equivalent Class D neighbour as well as providing a much simpler architecture which can be tweaked as required, without the need for reactive filter components on the output and the electromagnetic radiation resulting from an output stage switching at a few hundred kHz.

Class D amplification has inherent distortion in it and therefore is predominantly used in lower bandwidth amplification like in subwoofers. In other words it is quite impossible for a Class D to achieve the level of linearity in frequency response produced by a Class AB amplifier. Class D achieves about 90% power efficiency compared to about 60% respectively for Class AB.

Ultimately it comes down to what you want, for efficiency and cost effectiveness Class D is the best, but if you can sacrifice some efficiency & increase cost for the sake of sound quality then Class AB is the best.

Actually Class A amps sound the best, cost the most, and are the least practical. They waste power and return very clean signals. Class AB amps dominate the market and rival the best Class A amps in sound quality. They use less power than Class A, and can be cheaper, smaller, cooler, and lighter. Class D amps are even smaller than Class AB amps and more efficient, because they use high-speed switching rather than linear control.

The most important reason behind which multimedia speaker manufactures are switching from Class AB to Class D is to increase profit margin for the company. Class D amplifier modules are cheaper than Class-AB modules does not need expensive toroidal transformers and require a huge extruded aluminum heat sink.

Honestly I think that it is ridiculous to use a class D amplifier in a high end studio monitor and also you will not find one that uses Class D. Class D amps cannot be used on highs frequency response because of the way they work. They only produce square waves because of the technology involved, so they will make your highs sound lifeless and tinny. Class AB amplifiers produce full variable signals and can capture subtle nuances better while sounding warmer, more natural and generally having greater depth of sound.


Z-2300: The control pod of the Z-2300 is quite simple, minimalistic & functional, which I prefer. No fancy lights just a big volume knob, a bass control, a 3.5 mm headphone jack, power LED and a power button. You can keep the control pod on your desk where ever you like and the controls are very convenient.

Z623: The volume knob, bass control, 3.5 mm headphone jack, power LED and power button are all integrated on the right satellite. Now every time you need to make an adjustment you have to reach your hand out to the right satellite. This becomes very irritating and once again reminds me that it is a deliberate move by Logitech to cut cost.


Logitech have gone a whole way to reduce cost of the hardware in Z-623 in comparison to Z-2300.
1) The subwoofer is smaller & lighter with thinner wall thickness and no silver/black design. Saves cost.
2) The bass driver is smaller by an inch & have smaller magnet. Saves cost.
3) Jump from Class-AB amplifiers to Class-D with much less power. Saves cost.
4) Switching power supply instead of toroidal transformer. Saves cost.
5) No heat sink at the back of the subwoofer. Saves cost.
6) No master power switch & external fuse on the subwoofer. Saves cost.
7) Much thinner & shorter wires. Saves cost.
8) Satellites are ugly and use black plastic instead of glossy silver/black design with mesh cover of Z-2300 satellites. Saves cost.
9) Integrated controls with right satellite instead of separate control pod. Saves cost.


No doubt that Logitech produces speaker system with excellent built quality that are built to last for decades. But at least for electronic components like speaker sets nothing is for sure. And also remember that Logitech will provide support for the initial 2 years, after that there will be no support. So what happens when:

1) Bass driver blows: Since Z-2300 uses an industry standard 8 inch bass driver, you can find a hundred speaker companies out there to provide a 8 inch bass driver that fits into the Z-2300 subwoofer assembly. Check YouTube & you will find a hundred examples out there.

Since Z-623 uses manufacture specific & odd sized 7 inch bass driver, forget about getting it replaced with a new one. So, you end up with a dead system.

2) Amplifier Module: Class-AB amplifier modules found in Z-2300 are very easy to repair, any local repairing shop will do that for you, and the amplifier chips and components are readily available in the market for replacement. Same goes for Z-2300 toroidal transformer.

Z-623 uses Class-D amplifiers & switching power supplies which are piles of crap after they are broken or dead. Just think when your PCs power supply (SMPS) blows out you do not repair them since they require costly machinery for repairment & also the parts are not readily available. So you just buy another SMPS and fit into your PC.

The problem with Z-623 is it does not use a industry standard SMPS as your PC but are manufacture specific, which the manufacturer (Logitech) will not provide to you after 2 years. So, you end up with a dead system.

3) Satellites stop working: Z-2300 uses two satellites that are connected to the subwoofer with industry standard RCA input cables. Suppose one of them stops working, I can buy a dozen pair of bookshelf speakers having RCA input cables available in the market and directly plug to the Z-2300. All I have check is that each bookshelf can handle at least 40W RMS of power & are rated at 8 ohms.

As for Z-623 you can do that for the left satellite as it comes with RCA cabling but not the right one which comes with manufacture specific D-Sub plug. Also, the satellite speaker impedance rating is 6 ohms which is kind of odd, since 4 & 8 ohms are readily available in the market. So, if the right satellite goes you end up with a dead set.


Z-623 performs admirably well in movies & games. It also performs well in music. It may not have the same hardware architecture of Z-2300, but Logitech engineers have made sure that Z-623 possesses the genes of Z-2300. It definitely has the upper hand over its opponents namely Altec Lansing MX-6021, Sony SRS DB-500, Edifier S530 & Creative Gigaworks T3 in terms of performance. No doubt Z-623 is the winner among the current heard and also the best of the lot in terms of performance/ price ratio.

But when you put the Z-2300 in the above equation, everything falls loose. Z-2300 is like a lion among a herd of cattles named Z-623, DB-500, S530 & T3.

1) None of the above sets have the power output capability of Z-2300. Z-2300 is the loudest of the lot and makes the opposition eat the dust.

2) Z-2300 has wonderful power reserve in the amplifier & thus do not distort even at full volume. Z-623 & all the other sets distorts at full volume.

3) In terms of music representation Z-2300 is second to none. Since Z-2300 uses Class-AB amplifiers, the sound produced by Z-2300 is more natural, very well defined & represents the true analog nature of the human voice. Both male & female voices are excellently represented in Z-2300. In contrast Z-623s Class-D amplifier lacks a little bit of the natural feel & warmth in the sound as found in Z-2300 and represents more that of MX-6021 & DB-500 in their sound characteristics. The subwoofer has tight bass but the overall bass of the Z-623 is not well defined. A system with Class-AB amplifiers (as in Z-2300) will produce bass which is a little less deeper than a Class-D of Z-623, but the bass will be much more defined & accurate and also feel more natural & real.

For example, playing the track "Chant" of the band Foreplay, I noticed that the kick drums of that track produce "boom boom boom" on the Z-623. Playing the same track on Z-2300, the kick drums sounded "booouuumm booouuumm booouuumm" which happens to be the actual sound of kick drums. In contrast, Z-623 bass goes a little deeper but is less natural & neutral. Audiophiles will definitely choose Z-2300 over Z-623 for these single criteria.

4) In movies & games which do not contain the subtle nuisances of complicated music reproduction, Z-623 is right up there with Z-2300. If you just want a speaker set for movies & games you will be blown out with the performance levels these Z-623 babies can achieve.


Z-2300 is hitting the end of the production cycle. It is the last of the titans which is finally going to take slumber. But it is going to rule the hearts of those who were lucky enough to possessed them and experience their performance. If you really need a high end 2.1 THX certified multimedia speaker system dont waste any more time and get a Z-2300 while it is still available. If it not available then only greet the new champ of the block, Logitech Z-623.
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In reply to Rishiguru's excellent post post re the Logitec Z-623 v Z-2300. A correction to the statement that the 623 uses class D amplification. In fact it is Class G/H.

Class-G amplifiers (which use "rail switching" to decrease power consumption and increase efficiency) are more efficient than class-AB amplifiers. These amplifiers provide several power rails at different voltages and switch between them as the signal output approaches each level. Thus, the amplifier increases efficiency by reducing the wasted power at the output transistors. Class-G amplifiers are more efficient than class AB but less efficient when compared to class D, however, they do not have the electromagnetic interference effects of class D.
Class-H amplifiers take the idea of class G one step further creating an infinitely variable supply rail. This is done by modulating the supply rails so that the rails are only a few volts larger than the output signal at any given time. The output stage operates at its maximum efficiency all the time. Logictec Z-623 uses Class AB linear amps controlled by Switched-mode power supply used to create the infinitely tracking rails. Significant efficiency gains are achieved but with the drawback of more complicated supply design. No RF Hash as with class D and the usual good performance from AB.

I should mention that I have a Z-623 system and for the money it sounds 'real good'. My real system is a home brew using 2xFoster 12" carbon fibre subs driven by 2x500W RMS class AB amps. The speakers are wired in phase firing from the back and front of the enclosure with an internal Helmholtz resonator and tuned port firing downwards.
If Z-623 uses Class G, then it seems to be a nice thing. I have always wanted to get an Arcam AVR-600 back then and it took me a while to understand why that AVR sounds so good and now-a-days Arcam actively advertises their Class G amps in their premium range which are very nice and smooth.
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