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Small drivers vs big drivers

Hi,
I have a question that is always in my mind recently. I see some speakers with small  drivers (5-9 inches) that is reviewed to be able to throw out big sound stage and go down to 18hz-20hz. Some other speakers with big drivers (10-15 inches) though are commented to have 'big sound stage' but can only go as low as 30-35hz. 

To make the situation more complicated, some speakers have small drivers but there are many of them. Can many small drivers be compensate for the size limitation?

I don't know which specs determine a wide sound stage and the ability to reach low frequencies.  What is the pros and cons of each design?

Thank you!

Huy.
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quanghuy147 OP
29 posts
 
Thank you @eisen0169!

With me, actually, I don't care much about the size of the speakers, I just need the sound. (My wife is going to kill me if she reads this :) )
kosst_amojan
2,095 posts
 
"I work for a company the makes speakers with giant drivers. All small woofers just suck and you're a dumbass for paying good money for them."

That pretty much sums up the collective quotes and bottom lines whenever this debate comes up. Show of hands; who listens in a sports arena? Nobody? So why do you think you need speakers sized for an arena? 

"It's for the dynamics!"

Really? You listen at physically painful volume? You need a speaker that will produce 110dB at 50 away in your personal arena? 

Like that idiotic automotive quote goes, "there's no replacement for displacement", 15" woofers seem just as idiotic to me. Last I checked Formula 1 cars don't have 15 liter single cylinder engines. They have these tiny little things with a bunch of little pistons. Wait... That's because they're just trying to build them cheaper, right? Those Bugatti's are just really cheap because they're using 18 cylinders instead of one gigantic cylinder. 

Formula 1 engines don't use one giant piston for the same reason a lot of speakers don't. Large masses are much more difficult to control and replicate perfect pistonic movement with. 3 6.5" drivers have about the same area as a 10" driver but the smaller drivers are vastly stiffer and better controlled. It's a no brainier. 

Unless you're digging very low where you require the size purely to couple the frequency to the air, it usually makes sense to compromise between driver size and numbers of drivers. I personally think 2 8" drivers in a cab is a good compromise. 
audiokinesis
1,872 posts
 

Kosst, I think you are resorting to straw-man arguments; that is, putting words into the mouths of those you disagree with in order to make them appear foolish.

I design speakers having what you would probably call "giant drivers".

The primary reason we use them is for radiation pattern control, to minimize detrimental early reflections and create a spectrally-correct reverberant field.

One secondary benefit is improved dynamic contrast. Our giant drivers have negligible thermal compression at home audio SPL’s.

Another benefit is compatibility with a wider range of amplifiers.

Another benefit is a larger sweet spot with proper set-up.

Like just about everything else in audio, driver size is a juggling of tradeoffs.

Duke

kosst_amojan
2,095 posts
 
@audiokinesis 

I hate to break it to you, but you're wrong about radiation patterns. At every scale where waves are radiated and observed, arrays are the preferred and dominating technique. The largest radio telescopes are arrays. The largest optical telescopes are arrays. The largest audio rigs are arrays. The largest radio transmitters are arrays. 

Your argument concerned thermal effects is a non-starter because the basis of your argument assumes one large driver with one large voice coil vs. one smaller driver with one smaller voice coil. For an array of smaller drivers equalling the radiating area of one large driver the voice coil thermal radiating area will be greater in the smaller drivers. 

Ultimately the well understood physics of arrays better supports the technology. 
audiokinesis
1,872 posts
 

Kosst, of course we can compare arrays of smaller drivers vs large drivers.

"Array" is a rather open-ended term. How big is your array? Line array? J-array? Splayed array?

Arrays can get pretty big and pretty sophisticated.

So let’s do an actual apples-to-apples comparison.

Each of us picks out about $300 worth of drivers for their hypothetical speaker. You specify the shape of your array. Then let’s look at thermal and mechanical limits, radiation patterns, and bandwidth.

I’m picking a $210 woofer (Eminence Kappalite 3012LF), a $45 compression driver (Celestion CDX1-1446), and a $14 horn (Dayton Audio H6512), Parts Express retail prices. That comes to $269. These are all components that I actually use.

You pick your ballpark $300 worth of array drivers, tell me how they arrayed, and let’s take a look at the thermal and mechanical limits, radiation patterns, and bandwidths. I have a modeling program that can model radiation patterns fairly accurately, "Enclosure Shop" by LinearX. I will post my analysis of how your array would perform, and of how my giant driver two-way would perform. You are of course invited to do your own analysis.

Let’s get specific. Maybe you are right, maybe your array will be better across the board. Let’s go apples-to-apples and find out.

Duke

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