25W*4 or 45W*2 which one will give better audio experience

[arunkumar413]

Hi Team,

For an in car infotainment system which of the below configuration will give better audio experience.

4 channels (25 Watts each)
0r

2 channels (45 Watts each)

Also, I'm thinking of using **broken link removed**IC for amplifier. Do you recommend any other amplifier?

Thanks,
Arun

 

[audioguru]

The 4-channels Japanese amplifier IC has graphs of distortion in its datasheet. It shows that clipping begins at an output of about 16W into 4 ohms for each of its 4 channels. The words talk about high maximum output power that is when the volume is turned up too high so the output is severely clipped and is very distorted and has a squarewave waveform. The graphs show 10% distortion at about 24W but 10% distortion sounds awful.

How can this amplifier produce 45W each from two of its 16W channels? Two channels will produce a total of 32W. Four channels will produce a total of 64W that sounds only a little louder than 32W. If you are thinking of "bridging" two channels together you can't because each channel already has bridging.
Some amplifiers have higher output power when driving 2 ohm speakers. Not this one, it will blow up and/or melt.
The quality of the speakers makes a huge difference. Also a good-sounding car audio system has a sub-woofer.

 

[dr pepper]

Using typical car audio components probably 4 x 25, as even if a typical import speaker had 90w printed on it, whether it would actually survive handling that power let alone sound good is another question.

 

[audioguru]

As I said, the datasheet for the Japanese amplifier IC shows that like most car radio amplifiers it begins clipping at about 16W per channel into 4 ohms speakers. At 25W the distortion is unbearable because the waveform is almost a complete squarewave. It is a perfect squarewave when the output power is double the 16W because then the distortion harmonic frequencies produce as much power as the fundamental frequency.

Maybe Mr. Kumar thinks two channels can be paralleled for double the current then the amplifier will produce 32W into a 2 ohms speaker, for two stereo channels. But the paralleled amplifiers will poorly share the current so series resistors must feed the speakers reducing the power to the speakers and causing poor damping of their resonances.

All my cars have had 4 or more channels. 2 in the front, 2 in the rear and sometimes a sub-woofer. But none were used to play surround sound.
If only 2 speakers are used in a car, where will they be mounted? In the rear there is plenty of space for their enclosure (the entire trunk/boot) for good bass but the highs are not heard well in the front. In the front there is not enough space for big speakers and their large enclosures for good bass but the highs sound good.

 

[arunkumar413]

AudoGuruit seems that you're referring to this graph. From graph it appears that the distortion is above 10% at approx 25% watts that too if the supply voltage is 13.2V. In car audio the supply voltage is lesser than or equal to 12V. So I'm thinking that the distortion would be less than 10%.

 

[Nigel Goodwin]

The claimed power outputs are basically imaginary - a bridged amplifier from a car battery will provide 16W to a 4 ohm speaker (at a reasonable amount of distortion), or 4W for a single ended amplifier.

So your amplifier options are really 4x16W or 2x16W.

Any decision is really down to who many speakers you have?, for 4 speakers you need the four channel option, for 2 speakers only the two channel option.

However, these are standard specs from car radios - so why do you need an amplifier?.

 

[audioguru]

AudoGuruit seems that you're referring to this graph. From graph it appears that the distortion is above 10% at approx 25% watts that too if the supply voltage is 13.2V. In car audio the supply voltage is lesser than or equal to 12V. So I'm thinking that the distortion would be less than 10%.

No. The 13.2V and 4 ohms graphs show that clipping begins when the output power is halfway between 10W and 20W. 1% distortion is very obvious to most people and graph shows 18 to 19W. I never play an amplifier so loud that it is clipping. Do you?

The supply voltage in a car is 13.2V when the engine alternator is not charging and is 14.4V when it is running and charging.
A car is small and the speakers are near you. 4 x 16W= 64W which is very loud in a car, 32W is just a little less loud and 128W is only a little louder.

Car speakers also determine the loudness. In North America the rear speakers are 6" x 9" oval with a tweeter in the center. The front speakers in the doors are 5.25" and are not as loud as the rear ones and they play deep bass frequencies poorly.
Many North American cars have additional speakers all over the place with tweeters and a center speaker in the dash and a sub-woofer in the rear.
Cheap car speakers play all frequencies poorly.

 

[arunkumar413]

From the graph mentioned in my previous post how did you determine that clipping occurs between 10W-20W?

 

[dr pepper]

As allready implied when it comes to car audio there are a lot of over optimistic ratings.
Higher power car amps have a power inverter that steps up the supply voltage first.
I remember looking at a coach audio amp a long time ago, it had a transformer on the o/p as a step up, probably didnt sound that great though, and its tricky to get an amplifier to be stable at low resistance loads.

 

[audioguru]

An amplifier output is clipping when the input level is gradually increased but the distortion rises steeply as shown on the graph:

 

[arunkumar413]

Ok thanks. Now coming to the intensity of loudness heard by human hear which of following is more louder.

1) 2 speakers with 45W each.
2) 4 speakers with 30W each.

 

[audioguru]

Ok thanks. Now coming to the intensity of loudness heard by human hear which of following is more louder.

1) 2 speakers with 45W each.
2) 4 speakers with 30W each.

The curves in the datasheet show that this and most other car amplifiers cannot produce power as high as 45W or 30W.
If the speakers are all the same at the same distance, then 30W in each of four speakers producing a total of 120W will sound slightly louder than 45W in each of two speakers with a total of 90W. 10 times the power sounds twice as loud because our hearing's sensitivity to loudness is logarithmic.

 

[JimB]

which of following is more louder.

1) 2 speakers with 45W each.
2) 4 speakers with 30W each.

I am not sure, but I think that either of them in the confines of a saloon car would be loud enough to make your ears bleed.

JimB

 

[audioguru]

The peaks of the music probably will not be blasting at the maximum from the amplifier at 16W per channel but if they are then the average power will be 1.6W to 3.2W per channel which is loud but not too loud.
I have never turned up the volume on my car audio system high enough to cause clipping. But I have heard cars drive past me with their audio system clipping like crazy.