Watts, Ohms, dB's, sensitivity and volume

[Geoff]

This IS embarrassing but....

can anyone explain in laymans terms the relationship between them?

I just changed my speakers. The old were rated at 10-100W, the new 10-150W. My amplifier is supposed to deliver 130W per channel. I have to crank the volume up another 10% to get a reasonable volume... in fact it has to play at about 60% in a medium size room (I'm knocking on, but I'm not going deaf... yet!)

I had a Meridian power amp when I first got into hi-fi, rated at 100W per channel. It drove 100W speakers. Above 30% it was going to attract complaints.... and it sounded absolutely effortless.

So why now, with a more powerful amp, do I have to crank the volume much higher?

Cheers

 

[markw]

I'll take a slight stab at this and hope others might add to it.

first off, those watts you give us for your speakers tell us how much power they are rated to be able to handle and have virtually nothing to do with how loud they will play, given a certain power.

That's where sensitivity comes in, and while you mention it in your heading, you say nothing about it in the body of your message.

Anyhow, a speaker with a higher sensitivity rating will play louder at a certain power level than one with a lower rating.

All else being equal, a mere three decible difference in a speakers sensitivity rating can either double or halve the power needed for a certain power level.

Likewise, the settings on the volume control have very little relationship as to actually how many "watts" are being fed to the speakers, particularly when comparing one manufacturer to anotheer.

i.e... all else being equal, a speaker with an 88 db seneitivity rating will require twice the power of a speaker rated at 91 db to play at the same level.

 

[Geoff]

Markw

Thanks very much for the reply. The old speakers were rated at 86 dB, the replacements at 89dB.

The old ones needed position 50 on the amp (100 being full on the setting I use). The new need 60 for about the same volume.

How does the impedence affect things overall?

I'm sure I used to know all this, but family and time have put it all firmly in the background!

BTW, your system looks great.

 

[markw]

theoretically..

an amp will deliver more power at four ohms than it will at eight ohm, but this is not a free lunch. A four ohm speaker will also force an amp to work harder and pump out more watts than an 8 ohm speaker at the same "position" of the volume control.

again, if you're comparing the relative positions of the volume control on two different units, don't. It's not a valid comparison. There is no industry standard on what those numbers mean.

thanks for your comment on my system.

 

[Geoff]

Thanks again.

In the meantime, I'm going to follow some suggestions on the board to get the system sounding right.

Is your system posted in the gallery section?