Judging amps by Power Ratings for Inefficient Speakers
32@fa.com -- Sun, 05/02/2010 - 20:07
Dear Editors and Readers,
I am looking to drive fairly inefficient speakers such as Martin Logan Prodigies. I am assuming I need a lot of power. Obviously I intend to listen before purchasing, but I would like get educated and help narrow down the choices. I have spoken to some dealers and manufacturers and they all say - "Sure 155 wpc is enough because our amp is specia! Don't worry about the power rating. Our amp has expensive parts ans design and can drive any speaker" Is the power rating alone enough to judge, or are there othe factors such as current delivery, power supply, quality parts that help overcome the lower power rating?
All content, design, and layout are Copyright © 1999 - 2011 NextScreen. All Rights Reserved.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
Let your ears make the decision, not specs!
I agree with you but that is the last step. There are too many amps out there, and I have long driving distances. It would take me years!
There can be huge differences in the real-world power-output capabilities of two amplifiers that are each rated at "150Wpc."
Take a look at a 7.1-channel audio/video receiver that packs seven 100W amplifiers into a 40-pound package, and compare that with a single Pass Labs XA100.5 monoblock, for example. (I use this example because I've had both in my listening room at the same time.) The Pass has 40 output transistors; the AVR has perhaps four transistors. What this means is that in the frequency range over which the speaker's impedance drops, the Pass will deliver the current and the AVR won't. The AVR might be able to deliver 150W into 2 ohms for a few milliseconds; the Pass can deliver 400W into 2 ohms on a continuous basis. This from two "100W" amplifiers.
Still, if a speaker has low sensitivity and a difficult impedance curve, you need plenty of power to drive it. The highest quality 50W amplifier won't do the job.
The best way to determine if a given amplifier will drive a particular speaker is to connect them and listen for signs that the amplifier is running out of power (softening of the bass, compression of dynamics, sense of strain on peaks, or outright clipping).