There has been much discussion on many of the audio forums lately regarding mid priced A/V receivers and multi channel amplifier power capabilities as well as their abilities to drive low impedance loads. Much of the controversy steams around the infamous " All Channels Driven Test " which simulates a best case test load in a worst case environment and by all intents and purposes an unrealistic real world scenario. As a result, we have come up with a standard for measuring amplifier performance that deals with various types of power tests as well as other metrics that directly affect sonic performance and how the amplifier can sound powering various types of speaker loads.
Discuss "Basic Amplifier Measurement Techniques" here. Read the article.
When I was doing all of my critical listening in a car, being able to drain the battery on the freeway while pounding bass was the key measurement. The manufacturer power ratings on amplifiers really are useless. The Audioholics review of my receiver, along with other reviews led me to a brand I'd not taken seriously before. The measurements are very important to me, not because of a specific watt measurement, but the results as a whole. Any difficulties, or details of operation that are not what would be expected are also of high importance. For instance, a input that limited bandwidth or misapplied bass management. Surprises aren't always fun.
Thank you for taking the measurements seriously, I want to say thank you to everyone for doing a great job. Consumers lack the skill and equipment to fully evaluate things like amplifiers; independent analysis keeps firms honest and provides buyers peace of mind. It's nice to make an informed decision.
Thanks again, Allan
When a manufacturer would rate their amp at 100W and it was 5" x 5" x 2" with one 5A fuse, we were in the position of telling people that what they bought at the big sale put on by a liquidator was garbage and couldn't put out that much power if it was hit by a solar flare.
Never eat anything that squirts out of a machine.
Thanks for providing this explanation/education.
It is good to have an unbiased explanation of what matters and what doesn't relative to what we hear as well as insight into relative measures between different test methods used by various publications.
Perhaps the most important thing Audioholics is doing is providing a well thought out "real world" set of tests. If a test is not realistic, manufacturers are tempted to expend resources "building for the test" rather than building for audio quality.
In case anyone thinks this is a stretch, I'll offer two cases where this has been done:
Computer graphics card manufacturers incorporated a graphics sequence commonly used for testing into their board so as to by-pass actually having to process those graphics. These boards inexpensively returned exceptional test scores (on that particular test), but their real-world performance was not exceptional.
Honda (and likely other auto manufacturers - Honda is the one I know about) incorporated a design modifications to improve NHTSA side impact test results; however, if you were to relocate the point of the impact 6" forwards or backwards, the result would not reflect the car's safety rating.
The graph showing the spike in the Class D Axiom A1400-8's frequency response piqued my interest.
Is there (or will there be) a review on this amp (my search came up empty) with a more detailed explanation on this test result, or was this simply an isolated measurement to demonstrate the behavior of a Class D amp?
That is bizarre. I have to look into why that is the case. Thanks.Doh!
What am I doing wrong?!!!
I put "Axiom Audio A1400-8" into the search field and get nothing!!
Pursuing the truth in audio & video...
Thanks for the write up. You've excluded the all channels test becuase you say that this is a non event in real life. But so are just straight resistive loads of 4 ohms. I may have missed it in reading through this but does your equipment test for reactive loads as well? Any receiver can drive a 4 ohm resisitive load....but throw a complex impedance at it and it changes the whole game. If you do test for that you would probably be one of the first in the industry.
The other thing I'm curious about is that manufacturers using variacs during their tests to maintain line voltage. This could be easily eliminated if you provide a non standard 60/100 amp circuit. I know its non standard but I also can't help but think that people with big home theater setups would have dedicated feeds of higher amperage circuits.