Friday, April 5, 2013

"POWER", The Myths and Maths Series Part 1

Let's Talk About Power! (Part 1)

    I get asked a bunch of power related questions all the time.  My goal in this series is to educate and demystify what manufacturer's power ratings mean and how to apply them in real world situations.  I will also be doing an FAQ section with references and notes when available.  You may not like the answers but when applied, these answers may be the best thing you can do.

    Let us start with part of the chain that users see most. Woofers.  Woofers come in all shapes and sizes and in all cases, the power handling numbers printed on them by the manufacturer are WRONG.  The intent of this number is another story.  Some makers are conservative, some are just liars.  Either way, any number they give you is wrong.

    The reason they're wrong is that are so many more factors in the power rating of a driver that need to be considered.  In the case of woofers, there is program, (signal, music, sine waves, etc.).  Another factor to consider is enclosure size and that relates to the overall question, "What's your application?".  How are you going to use this tool, this device that turns electricity into sound.  I myself have used a wrench to pound in a nail so keep an open mind when it comes to application.  Everyone wants to do different things and it's important to keep that in mind when helping someone or planning your own projects.  Not everyone has the same kind of budget nor standards.  Let's keep it fun and interesting though and explore several avenues of application.

    Entry Level / Woofers

    Entry level subs are by far the best money makers for audio brands / manufacturers.  They cost close to nothing to build and ship, yet the margin on these items is the greatest, (percentage), and the price point is the broadest and most accessible in the market.  In recent years, you may have noticed a flood of these products.  JL Audio for example out did themselves.  The typical 4 tier marketing strategy was W1, W3, W6 and W7 to top it off.  Now they have two more levels of performance below what used to be the entry level woofer, the W1!  That's dookie-load of sku's!  The great part about this is that now everyone can afford to buy a genuine JL Audio woofer.  What's even better is that the WX series is no slouch.  It's certainly not a W7 by any stretch of the imagination but they do get down and work great in small / medium sealed boxes which also save the end user money.  Enclosures can be almost made of cardboard and still sound great due to the low pressure.  Less packing material is required to ship and amp costs / requirements are cut down considerably.  All in all a great deal... Unless you want to do hair tricks....

    Now, back to the problem of POWER.  Assuming what I've seen, tested and heard is true, these two woofers both come from the same factory overseas and are, in essence the same woofer.  Assuming all of that, HiFonics claims this sub is good for 800w Maxx.  (Yes that's double X's because it's that bad-ass!)  JL is much more conservative in their power rating and even make a recommendation.  Their site also has a much cooler graph to show you where the , "DumDum Line", has been drawn at no more than 200w.  With that said, neither of these ratings do anything to address application.  Both of them are wrong and yet, 'acceptable' and legal answers to what these subs can take. (Also don't worry about the secret of the HF series subs getting out.  People that buy the HF series are not the kind of customers JL wants.  (More on that later in the buying / selling blog entry.)

OUCH!  That's HOT!

    So what's a girl to do?  Michael Q. aka Q-Daddy, one of my early mentors broke it down this way.  Imagine a 100w standard work light.  They're really bright, hot and dangerous.  Imagine holding that bare bulb in your hands.  THAT'S what 100wrms feels like!  So if that's what 100w is, how can a speaker company rate a speaker do be double that and not be called a liar?  Simple.  Different makers use different methods of ratings.  Some companies rate their speakers as a "Thermal", rating.  Meaning when they fail or catch on fire, e.g. old Orion XTR woofers.  Some use some very good math and measurements but those numbers still don't address frequency or enclosure size.  None of them ever address the amount of RUN TIME that the driver can deal with that kind of heat.  All of a sudden, 400w becomes an oven in a space the size of your fist.  How long can your woofer deliver awesomeness?  Is that sine wave?  Is it random pink noise?  Is that for an 'optimal' enclosure size?  What is optimal about the enclosure?  Is it for SPL or SQ?  Is it to get the most low end?  What's considered low end?  20Hz?  30Hz? 40Hz?  With a filter or without? Xmax vs Xmech?  110 or 220 VAC?

   Dan Wiggins went through this with his clients when he started Adire Audio.  Here's a paper that shows how the Brahma did with all that power.   After reading the paper, you'll see that enclosure size has everything to do with power handling numbers.  As always, there is a compromise.  You can have great output at 30Hz, but you can't throw 1600wrms at it and expect it to survive... At least not that driver.  Now if you have an Adire Parthenon, that's a different story.

    Can you rebuild a speaker to handle more power?  Yes, but you loose the ability to play deep.  You simply re-build the speaker with higher power handling features like direct connect leads, stiffer suspension, maybe even a lighter cone.  So now your rubber band / woofer is much beefier and tighter.  Can you abuse it more? Yes.  Does it handle six gazillion watts? Yes, but now because of the stiffer suspension it has trouble with the low end which is sorta the whole point to having a woofer in the first place.  To get around this, you can add mass to the driver, you can even put it in a bigger box but you're still limited by excursion to get the loudness at the depth you're looking for.  And now you've killed the sensitivity of the driver by adding mass to it.  There are several ways to get around these problems.  A great example of this is also from JL Audio.  The W7 series.

    Displacement = Bore x Excursion, this is the key to moving lots of air.  Since not everyone can have a 50" sub-woofer in their car, excursion will have to be your friend if you want to make really low sounds quite loud.  The W7 series from JL Audio does a great job of this.  They start out with a healthy amount of magnetic material, the motor as it's called.  Add a tight gap and a soft, as well as large suspension and you've got a winner.  Click the link above and then click on the Specifications tab.  You'll see their cool power graph on what's acceptable.  (More on how JL and other brands cheat at this later.)

    OK, so when you look at these graphs, that's the power that's applied, not the amplifier size.  I get asked all the time, "What size amp do I need?", that's a whole other blog entry I'll make about selling / buying.  Basically, whatever you can afford is the bottom line and then you can deal with that. Since you can afford what you can afford, that's what you go with.  So then the question becomes, "Should I buy a popular brand like JL or Kicker or will a generic China made amp do the same job?"

Check back in a few days, bookmark the page or subscribe to this blog and / or our YouTube channel.

The new video will show you how to make the Mojo / LVS woofer more reasonable or just re-cone it.

Thanks as always,
Patrick Chandler
Co-Founder of Robot Underground