Speakers-Facts on Sensitivity,Number of Drivers,Ohms and Watts

[Audio_Freek]

Hello FM's

The post is to make a clarity on the common facts which are consider when someone like to Buy first speaker or Upgrade.

1.Minimum Watts- The Amplifier should have atleast 2*power of the minimum recommended watts of speaker.
Eg: Speaker Minimum Wats is 30 and Max is 100, then the Amplifier should be atlest 60 Watts per Chanel.

2.Sensitivity- High the Speaker is Sensitive they can be driven with less watts amps,

Assumption : 99 DB Speaker can emit 144 db with only 32 watts,where as 86 DB Speaker needs almost 500 Wats per channel.

3.Ohm- some basic understanding. Low the Ohm will load would heat up the power unit(Transformer) of Amp compared to 8 Ohms.

8 Ohm 89 db Sensitivity speakers consume 500 watts for 114 db.
4 Ohm 89 db Sensitivity speakers Consume say approx more power than 8 ohms.

So 8 is better and 4 needs more power.

Is this the reason the SUBWOOFERS are more power HUNGRY?

Note: The wats needs to be DOUBLED for feeling the INCREASE three DB.

4.Numbers of Drivers- Still need a clarity.

2*8 ohm speaker=4 Ohm Load= Double the power required than Single driver.


1*8 Inch driver at 89 db Sensitivity needs 32 Watts for reaching 104 DB ?
2*8 Inch Driver at 89 db Sensitivity needs 64 Watts for reaching 104 DB?


I understood that MORE DRIVERS=MORE Watts consumed= Less OHM.

So DOES More drivers= Good Quality of sound and the power consumed are really worthy?
If the More sensitivity Speakers are easy driven with low power amps then Why we cant find much Speakers with More sensitivity now a days compared to say 70's and 80's or before.I have seen few Vintage speakers they are really with High sensitivity. But

Please share your opinion's

Note:
All, All the above is my assumption\understand by reading and not TESTED LIVE ,So kindly correct wherever, I that i could correct my understanding.

 

[Jatt_boy]

Hello FM's
2.Sensitivity- High the Speaker is Sensitive they can be driven with less watts amps,Eg 99 DB Speaker can emit 144 db with only 32 watts,where as 86 DB Speaker needs almost 500 Wats per channel.

3.Ohm- This is in-directly proportional to Watts consumed.

8 Ohm 89 db Sensitivity speakers consume 500 watts for 114 db.
4 Ohm 89 db Sensitivity speakers Consume say 1000 Watts for 114 db


1*8 Inch driver at 89 db Sensitivity needs 32 Watts for reaching 104 DB ?
2*8 Inch Driver at 89 db Sensitivity needs 64 Watts for reaching 104 DB?

Please share your opnion's

Sir, the above said is not in agreement with the laws of physics applied to electronics/transducers and sound pressure level

 

[dheerajin]

may be not all but some of facts can be found in these links--
http://www.avsforum.com/forum/91-audio-theory-setup-chat/1473592-b-w-speakers-power-hungry.html

B&W 685 and Audiolab 8200A | whathifi.com

cheers

Dheeraj

 

[NakTech]

1.Minimum Watts- The Amplifier should have atleast 2*power of the minimum recommended watts of speaker.
Eg: Speaker Minimum Wats is 30 and Max is 100, then the Amplifier should be atlest 60 Watts per Chanel.

In my opinion this is very very minimum. Ideal is to match the Max power with the RMS power of the amp. If further power can be afforded, add at least 2dB more headroom to the amp.

2.Sensitivity- High the Speaker is Sensitive they can be driven with less watts amps - This is correct.

Eg 99 DB Speaker can emit 144 db with only 32 watts,where as 86 DB Speaker needs almost 500 Wats per channel. - This is wrong.

Sensitivity = 99dBSPL@1W@1m
Target SPL = 144dB@1m
dB difference = 144-99 = 45dB greater than 1W
Therefore power required for 144dB = log INV (45/10) = 31622.77 Watts

Sensitivity = 86dBSPL@1W@1m
Target SPL = 144dB@1m
dB difference = 144-86 = 58dB greater than 1W
Therefore power required for 144dB = log INV (58/10) = 630957.34 Watts

All this is in free field.

3.Ohm- some basic understanding. Low the Ohm will load would heat up the power unit(Transformer) of Amp compared to 8 Ohms.

This is true.

8 Ohm 89 db Sensitivity speakers consume 500 watts for 114 db.
4 Ohm 89 db Sensitivity speakers Consume say approx more power than 8 ohms.

The SPL a speaker can produce depend only on the sensitivity and power drawn from the amplifier. Impedance has nothing to do with it.

But if the gain of the amp is constant, 4 Ohm will draw double the power from the amp compared to 8Ohm. So if you compare 2 speakers with the same sensitivity but one 4 Ohm and the other 8 Ohm, the amplifier gain required to produce the same spl at the same distance would be 3dB less for the 4 Ohm. But if you measure the power at that spl, both 8 ohm and 4 ohm will draw the same power because the sensitivities are same.

4.Numbers of Drivers- Still need a clarity.

2*8 ohm speaker=4 Ohm Load= Double the power required than Single driver.


Double the power it can handle than a Single driver. It is not a requirement.

1*8 Inch driver at 89 db Sensitivity needs 32 Watts for reaching 104 DB ?

Sensitivity = 89dBSPL@1W@1m
Target SPL = 104dB@1m
dB difference = 104-89 = 15dB greater than 1W
Therefore power required for 104dB = log INV (15/10) = 31.6 Watts

Yes... you are right...:clapping:

2*8 Inch Driver at 89 db Sensitivity needs 64 Watts for reaching 104 DB?

This is a bit complicated. 64W is wrong. But how much power is actually required for 104dB depends on how the 2 speakers correlate in the acoustical environment. If the 2 drivers are very close to each other, we can assume that they are perfectly coupled. Then there is a 3dB gain in sensitivity. In that case you will need only 16W per speaker.
However, 2 speakers can never be in the same point. So depending on the distance between them and the wavelength of the sound there will be varying degrees of correlation. Usually low frequencies below 100 Hz are considered to gain 3dB for sure because their wavelengths are very long.

I would recommend further reading of The yamaha sound reinforcement handbook. It will be there in all the leading libraries. All the best...

 

[dheerajin]

i dont know why experienced ones are quiet..and it is not debatable subject as cables..please guide us all in this respect..

thanks
dheeraj