2. amps-preamps
  3. 190144-130

Shocked. Need Opinions. How muck power do I need?

I’m moving so of my sound gear around. As a temporary measure, I set up my little Cambridge EVO 75 in my main system. Driving my Dali Mentor 6s in a large room (36x36). Speakers are 9 feet apart and seat is 10 feet from speakers. This 75 water replaced my much more powerful monoblocks. To my shock, the amp drove these speakers just fine. The bass was a little weaker, but perfectly acceptable.  Here’s what I want to know— if 75 watts are enough, will 40 watts do? I’m talking all solid state. What say you?
 

 
 

 

tomaswv

Showing 3 responses by kijanki

kijanki's avatar
kijanki
4,452 posts
 

With 40W it will be -2.7dB.  Perceived loudness will be 16.6% lower (still over 100dB)

kijanki's avatar
kijanki
4,452 posts
 

For every decibel volume increase above 86db requires double the power.

For every meter distance requires double the power.

Double the power will increase volume by 3dB (+23% perceived loudness)

Volume drops at double distance by 6dB. To keep volume the same requires 4x power.  To keep volume at 2m the same as 1m requires 4x power.

kijanki's avatar
kijanki
4,452 posts
 

Required output current at min load can be calculated.
My Benchmark AHB2 delivers continuous 100W at 8ohm requiring 3.5A current.  Let's assume even 5A to give it 100% overhead (200W).  Current will be 4x higher driving 2ohm load (8/2=4) to keep the same output voltage (perfect voltage source), resulting in 4x5A=20A.  AHB2 is specified at 29A maximum current (both channels driven) so it is OK with 2ohm loads.  “Both channels driven” is very important part of this specification showing that power supply is able to deliver total specified current (2x29A=58A).

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