2x60watts LM3886/LM4780 can drive 2-ways bookshelf?

[cent88]

Is a single LM4780 or stereo LM3886 good enough to drive pair of 6ohm 2-ways bookshelf?

15watts-75watts
or
30watts-100watts

chassis and heatsink(L60xH45xW175mm) size is my limitation to go for parallel.

[AndrewT]

Hi,
are your speakers 6ohm or 4 to 8ohm?

You need this information to allow a transformer to be chosen to power the amplifiers.

A two way 6ohm speaker will have a 6ohm Bass/Mid driver and a 6ohm treble driver.

A two way 4 to 8ohm speaker will have a 4ohm Bass/Mid driver and an 8ohm treble driver.

You can measure Re of the drivers to determine the nominal driver impedance. Re ~ 70% to 80% of Rnominal

[cent88]

I have single LM4780 driving Energy eXL-16 bookshelf.
50 - 20 KHz +/-3dB

Tweeter(19mm)
Aluminum Dome with Cloth Suspension

Mid Driver(16.5cm)
Mica/polypropylene
XO cut 2.2KHz
91dB
8-ohms
15 - 110 watts

Not really satisfied with the sound, may be cause of the eXL-16's XO(full of electrolytic caps). Shall I mod it?

So getting a new speaker, either Wharfedale Diamond 10.0(6ohm nominal) or Dali Concept 1(8ohm nominal)/Dali Ikon 1(6ohm nominal). The only speakers I can get locally.

Here is the Wharfedale 9.1 measurements. I guess the drivers should be the same as newer Diamond 10.1.
http://www.stereophile.com/content/w...r-measurements

[AndrewT]

Hi,
the Diamond looks like a 4 to 8ohm speaker rather than a 6ohm speaker.
However the 2octaves below 6ohms is probably just about narrow enough (non continuous load) that you may be able to design the amplifier for 6ohm duty.
I'd ignore the 10 to 15Hz region for normal music.

[pacificblue]

Originally Posted by cent88

Is a single LM4780 or stereo LM3886 good enough to drive pair of 6ohm 2-ways bookshelf?

Yes.

Originally Posted by cent88

15watts-75watts
or
30watts-100watts

What does that mean? Can this be summed up as 15-100 W? How did you arrive at those figures? Most Gainclone owners have 20-25 W of output power per channel. Most of them believe they have 68 W and hardly any of them notices the difference or needs more power than he has. The few that do need more, won't even be satisfied with 100 W per channel.

Originally Posted by cent88

chassis and heatsink(L60xH45xW175mm) size is my limitation to go for parallel.

I doubt that you will be able to fit even a single channel into that. My 2 x 3,5 W LM1876 hardly fits into a 100x100x63 mm case with power supply and it only has a single pair of input connectors. Maybe you can achieve such a small thing, if you opt for a class D amp with external power supply.

[cent88]

@andrew:
then I'll try a pair of lm3886 for 6ohm duty.
I don't really care of the frequency below 50hz. =]

@pacific:
how come only half of the power 20-25W?
(L60xH45xW175mm) is the dimension of heatsink, 45mm length of fins from base.

[AndrewT]

Originally Posted by cent88

heatsink(L60xH45xW175mm)

do you know Rth s-a of this sink?
How many 3886 chipamps will be fitted to this heatsink?

[cent88]

@andrew:
Within 0.8-1.2C/W if not mistaken.
two lm3886 will be fitted to this heatsink and wondering it can support four or not.
my 36Vdc lm4780's 1.4C/W heatsink's volume/surface ~4 times lesser than this heatsink and doing 60-65celcius. ambient 27-33celcius.

[pacificblue]

Originally Posted by cent88

how come only half of the power 20-25W?

Because most of them use 2x18 V transformers and 8 Ohm speakers. 30 W is what you get from such a configuration with a stable power supply. Gainclones usually have low capacitance PSUs, which does not create a stable power supply and limits the output power accordingly.

Originally Posted by cent88

my 36Vdc lm4780's 1.4C/W heatsink's volume/surface ~4 times lesser than this heatsink and doing 60-65celcius. ambient 27-33celcius.

Seems you are listening at very low power levels. Even the over-optimistic Overture Design Guide calculates 1 K/W for 150 °C junction with 36 VDC and that is with 8 Ohm speakers.

[cent88]

@pacific:
I crank my lm4780 50k pot and also DAC/buffer near to the half only, higher I'll become deaf if listen to it for long period.