Help required on Logitech Z-2300 toroidal transformer

[RishiGuru]

A little 8" speaker is an ordinary woofer, not a sub-woofer. That is why you turn up its volume control too high.
If it is half-decent or better then it will have a flat response down to about 60Hz.
A half-decent or better sub-woofer has a flat response down to 20Hz or lower so you can feel the vibrations.

A volume control is never made to provide full power when it is turned to max. It allows you to turn up the volume much higher for sounds that are played softly. If the volume control is turned up to max rotation then with normal music the amplifier will be clipping like mad.

A volume control is not linear, it is logarithmic. So when it is turned down to half-rotation then the power is 1/10th as much as when it is turned to max. 1/10th the power sounds half as loud. 10 times the power sounds twice as loud. That is why volume controls are logarithmic.

Here is some pictures of the 8 inch bass driver. It is made by TangBand and is based on their model W8-670Q. But as Logitech says these are custom designed from that model. While W8-670Q is capable of 70W, Logi's modified version W8-670C is capable of 100W. I think now they are also overrating this drivers too.

I provide the link to their website below:
TangBand W8-670Q

Some pics of my subwoofer:
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Do you think this sub is okay. TangBand quotes FREQUENCY RESPONSE -->38-500 Hz

 

[audioguru]

Manufacturers of cheap audio products lie about output power.
They talk about turning up the volume control too high so there is horrible 10% clipping distortion to make the power number higher. But nobody listens to audio when the amplifier is clipping like mad.

They don't say "continuous power". Maybe the power is produced for only a moment? Maybe it is "peak power" which is simply double the amount of real power. Maybe it is momentary peak power which might be 4 times the amount of real power.

 

[RishiGuru]

Z-2300 uses 2.5 inch polished aluminum phase plug drivers in their satellites. The 12W satellite drivers of Z-2300 are again custom designed & is based on 3 inch Tang Band (W3-594SB) having frequency response capability between 100Hz-20kHz.

 

[mvs sarma]

yes
modern world, created a new term called PMPO which, as you once rightly commented, is not defined anywhere If i remember.

@Rishi guru,
nice pics
of late speakers come up with transparent polyurethane based cones. Everything looks transparent.

We used to have woofer, mid range and tweeter. you cant perhaps have 100Hz to 20KHz same speakers?

Perhaps the need for 5+1 system is different, as they are able to orient the sound as per original recording- may be what is called surround sound effect.

 

[RishiGuru]

Manufacturers of cheap audio products lie about output power.
They talk about turning up the volume control too high so there is horrible 10% clipping distortion to make the power number higher. But nobody listens to audio when the amplifier is clipping like mad.

They don't say "continuous power". Maybe the power is produced for only a moment? Maybe it is "peak power" which is simply double the amount of real power. Maybe it is momentary peak power which might be 4 times the amount of real power.

You are absolutely right, they do not quote about "continious power". This is what I found in the Z-2300 manual:

Total RMS Power : 200W
Total Peak Power : 400W at < 10% THD
System THD: Better than 0.05% before clipping
Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz

Can you describe what "Total RMS Power" means? And also peak power is rated less than 10% THD. But th question that eludes me the most, what is "System THD"? All this terms suddenly looks very mysterious to me.

 

[audioguru]

"Total RMS Power : 200W"
They don't say that the volume control is turned up too high so there is horrible 10% distortion. They also don't say continuous or momentary. It is probably only for a moment.

"System THD: Better than 0.05% before clipping"
THD is Total harmonic distortion. Any modern amplifier produces low distortion when its volume control is turned down so the amplifier is not clipping.

"Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz"
10% distortion is when the volume control is turned up too high so there is 10% terrible clipping distortion to make the power numbers appear higher.

 

[mvs sarma]

at 230VAc, it is (20.1*1.414)-one diode drop. this value with no load.
once loaded copper loss etc come up and rectified voltage falls to almost 21V or so DC.
while so the design works anywhere between 18 to 25 but the output changes for the final stages of amplifier.
pre-amplifiers would have regulated power derived from the 20V DC line.
even power amps too may have stabilized biasing within the chip
which power amp chip is used and what is its spec?

 

[RishiGuru]

"Total RMS Power : 200W"
They don't say that the volume control is turned up too high so there is horrible 10% distortion. They also don't say continuous or momentary. It is probably only for a moment.

"System THD: Better than 0.05% before clipping"
THD is Total harmonic distortion. Any modern amplifier produces low distortion when its volume control is turned down so the amplifier is not clipping.

"Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz"
10% distortion is when the volume control is turned up too high so there is 10% terrible clipping distortion to make the power numbers appear higher.

So, it all comes down to a 80W "continuous power" 2.1speaker system which will provide moderately good distortion free sound under half volume.

Also, never to turn the volume more than half, or else the transformer will blow!!!!!!!!!!!

These crappy computer speaker companies......can go and F%@K themselves.

 

[RishiGuru]

at 230VAc, it is (20.1*1.414)-one diode drop. this value with no load.
once loaded copper loss etc come up and rectified voltage falls to almost 21V or so DC.
while so the design works anywhere between 18 to 25 but the output changes for the final stages of amplifier.
pre-amplifiers would have regulated power derived from the 20V DC line.
even power amps too may have stabilized biasing within the chip
which power amp chip is used and what is its spec?

Z-2300 uses Class-AB amplifiers from STMicrolectronics.

The amplifier uses:
i) Two STMicroelectronics Class-AB, 80W, TDA7295 amplifiers bridged together for the subwoofer.
ii) Two STMicroelectronics Class-AB, 60W, TDA7296 amplifiers powering each of the satellites.
iii) Two ripple filters SamXon/ CapXon 10,000 uF, 35V capacitors for smoothing the DC output.
iv) A Japan Radio Corporation’s JRC-4565 operational amplifier required for the headphone socket in the control pod.
v) Two voltage regulators a 78M18 and a 79M18, making positive and negative 18 volts respectively to feed the JRC4565 op amp.

 

[mvs sarma]

thanks Rishi jee

 

[audioguru]

The power transformer is rated to have an output of two times 20.1VAC when it has its rated load. So its resistance has already dropped the open circuit voltage and its peak will be 1.414 times higher which is 28.4V peak. The single rectifier drops it to 27.4V and the ripple drops it to 26VDC. A very poor quality transformer will have its core saturate a little which "squashes" the sine-wave and reduces the peak voltage.

 

[audioguru]

The Tangband 8" Taiwan woofers have paper cones not poly.

 

[mvs sarma]

they made a full wave rectifier with centre tap, thus it is dual output.

ps:
the music power was defined by ST micro in their datasheet for TDA7296 as
" MUSIC POWER is the maximal power which the amplifier is capable of producing across the rated load resistance (regardless of non linearity)1 sec after the application of a sinusoidal input signal of frequency 1KHz."

 

[RishiGuru]

they made a full wave rectifier with centre tap, thus it is dual output.

ps:
the music power was defined by ST micro in their datasheet for TDA7296 as
" MUSIC POWER is the maximal power which the amplifier is capable of producing across the rated load resistance (regardless of non linearity)1 sec after the application of a sinusoidal input signal of frequency 1KHz."

From the Logitech website i found out that Z-2300 have two model generations
1) M/N: S-0118A
2) M/N: S-0118B

This numbers are printed at the back of the subwoofer. There are rumors in the web that the second model consist of 4 X TDA7296. One of the members of Logitech Forum confirmed me that he has got the S-0118A model and they have 2X TDA7295 (for sub) and 2X TDA7296 (for satellite).

I have the S-0118B model.

Now having a new model may have two implications:

1) To rectify some problem in hardware that may have existed during the development of the product and later been reported by the customers after prolonged use.

2) As a cost cutting measure. With time the minimum offering price(MOP) of a product comes down so the company is no longer able to keep the same margin in profit that it garnered on new release of that product.

Now 4 X TDA7296 is more than enough for the 150.9VA transformer. And there is no need of TDA7295 since the toroid is incapable to extract the full performance from it.

@mvs sarma & @AudioGuru

How much power you TechGurus think will be distributed to the subwoofer & to each satellites?

 

[mvs sarma]

A WORD OF CAUTION TO RISHI GURU
the fuse inside the transformer would not blow for no reason.
Thus it is important to check for short circuits on load of either main or satellite amplifiers before really switching on the system with serviced transformer. OTHEWRWISE THE FUSE WOULD BLOW AGAIN.

 

[mvs sarma]

From a distance we cant comment.
as it is already owned . there should be no regrets. human years need a few watts to be able to listen
all other power only to disturb people surrounding you. thus , use it at a level where distortion is less
but take caution not to energize unless any possible short circuit by any section of amplifier is tested deliberately and satisfied.

 

[RishiGuru]

A WORD OF CAUTION TO RISHI GURU
the fuse inside the transformer would not blow for no reason.
Thus it is important to check for short circuits on load of either main or satellite amplifiers before really switching on the system with serviced transformer. OTHEWRWISE THE FUSE WOULD BLOW AGAIN.

Actually, I was blasting the Z-2300 at nearly 90% volume at my house party when it stopped working. It blasted for nearly two hours at 90% volume when suddenly everything stopped. I came and inspected the subwoofer & found that the heat sink is as hot as a frying pan & the LED on the control pod is not glowing. Also I checked the fuse at the back of the subwoofer & it was ok.

Later as we found the internal fuse of the transformer blew. I am now astounded how that punny toroid could manage to withstand for almost 2 hours.

 

[mvs sarma]

If nothing else failed, you would be lucky !!!

 

[RishiGuru]

If nothing else failed, you would be lucky !!!

Tomorrow will be the day to find out whether every thing will pan out perfectly or not. Wish me luck!!!

 

[audioguru]

Thank you for explaining that your house party had the sound system playing much too loud (you said it was blasting) which luckily blew up only the fuse in the transformer and not the entire circuit and speakers.

Don't forget that it is a computer sound system, not a home sound system.