How Much Do You Need: The Ultimate Question Of Power
Chapter 1
“How Much Amplifier Power and Speaker Output Do I Need?” is a topic that often comes up, in many contexts, especially in DIY design when we’re selecting among components, hopefully taking their interaction into careful consideration towards a goal. We get to choose drivers. We get to choose amplifiers. We get to choose enclosure design. We get to choose the placement of loudspeakers and listening areas. If we’re really lucky and serious, we get to choose all aspects of the room itself.
Options are empowering, and if exercised intelligently, they are an efficient means toward end goals, if we understand consequences. That means understanding the interaction of factors, as well as the actual benefits of the end goal, spelled out into objective criteria. How much you need of anything depends pretty much on everything, from the source content itself, to your optimal personal playback preferences, and all things between. It is a complex question, with multi-factor answers.
As an end product, delivered to your lap, your head, at your ears, and ultimately between them, the end result of Sound Pressure Level, or SPL, is often related to ‘Reference Level’.
So Let’s talk about ‘Reference Level’,
In the aforementioned forum thread, Tom Vodhanel of Power Sound Audio had some really good points as to why this was not a trivial consideration, as did many others, and David Matthews shared this pretty good take in an editorial article.
I think this is particularly salient and a common discussion within DIY circles, as we often wonder about matching amps and speakers based on ‘power handling’ capabilities, sometimes to a dysfunctional level, followed by examining modeled output predictions to sometimes excruciating length. Chris Popovich might call it modelbating, an offshoot of measurebating, that can often become analysis paralysis.
While this happens often to nauseating detail when looking at predicted theoretical output, it often becomes very vague about how all of that translates to what we really get at the listening position, and how that compares to what we ‘need’ to achieve target playback capabilities.
What we actually need throughout the system, specifically, to satisfy our actual listening requirements, is itself a question that many don’t even bother to ask.
Many ‘System Designers’ are actual wizards, but more in the sense of configuration wizards that fill slots with options. For example, a client wants a quote, so they choose Widget A from Category B into Designated Quote Slot C, and keep adjusting choices in ‘D-Tools’ until that final total price of installed system quote adds up between Cost D minimum and Cost E maximum, with enough abstract brand and religion clout to feel good about it. I have watched it work that way, behind the scenes, and it reminds me of seeing how many clowns you can fit into a car to drive around in a circle. Most system ‘designs’ I have seen by companies selling ‘design and engineering’ are barely engineered, if at all. If they come with accurate wiring lists and connection diagrams that actually work, they’re better than average.
If we are actually doing system design engineering on a deeper level than having boxes that connect to make sound, we need to ask this question, among many, and we need to arrive at an answer, both in terms of end result capabilities, and specifically how we guarantee that we actually get there, with performance capabilities (beyond just SPL) intact: How Much Do I Need?
In depth interrogation of that question includes putting the screws into thumbs of the details, such as.
At your listening position?
From your loudspeakers?
From your power amplifiers?
Often, in real life, that question is answered not by self-evaluation, but by simply pulling a number commonly accepted by others. Of those times, most often that number is related to ‘Reference Level’. As in, “I want to be able to hit reference level”. Sometimes it may be, “I only listen 10-15 dB below reference, because beyond that it’s just too loud. ” Both of those answers are valid, though how one comes to that might benefit from some context.
Read it now, read it later. It’s a pleasant read.
‘Reference’ itself is a loaded word. It is often used in contexts such as ‘The Reference Standard’, as in a standard of the highest quality. However, the implications of the word, its history, and derivative nature of human beings, have created a gap between meaning and interpretation that is anything but consistent. There is a saying, I can explain it to you, but I can’t understand it for you. Reference level is exactly that, and I will attempt the former.
Manufacturer Perspective (Cody Hiebert). Reference level is interesting, because it shows no guarantee of sound quality at maximum output. What is the distortion metric on the speakers, where are the compression limits? Compression is the first indication of lost efficiency, and different distortions show how the speaker is deviating when suffering from efficiency losses. Without this information, Reference and associated headroom margin, or any other name you want to call SPL based cinema design, is just simply a number with no assurances attached. By its own nature SPL becomes ambiguous because in of itself it is a meaningless number with no real value. It does not guarantee linearity at all SPL points in audio playback.
Come back next week for Chapter 2.
Originally published by Totally Hypeless
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