Why aren’t there more 2-ohm speakers?

Another thread in this forum got me thinking -

Since most car audio amps are 2-ohm stable in stereo, and have been for quite some time, why aren't there more 2-ohm speakers?  I'm not talking about about subwoofers, I'm talking about component sets and coaxials/triaxials.

Think about it - how many of us are driving around using our 2-ohm stereo-stable amps to drive a pair of 4-ohm speakers or component sets?  That's wasting half of the capability of our amps.  Are 2-ohm speakers that much harder or more expensive to design?  Are they any harder/more expensive at all?

I know that 4-ohm speakers have been the standard in car audio almost from the beginning, but it seems to me that a speaker company could make a bundle in the aftermarket by making 2-ohm speakers and component sets.  As a consumer, you could double the power from your aftermarket amp with a simple speaker swap, or if you're designing a system from scratch, you could use a smaller amp to get the same power by using 2-ohm speakers.

The only technical drawback I can think of would be the fact that you'd be halving the damping factor of the amp.  That's not important, since just about any modern solid-state amp has a damping factor well into the triple digits.  You'd never hear the difference in damping factor going from a 4-ohm load to a 2-ohm load.

Scott Gardner

The old Orion HCCA component set was 2 ohms. 

But actually one thing I learned recently is that running at lower impedances increased distortion levels.  And I'm not talking about just from the amplifier.  Dr. Kipple has done extensive research on distortion from speakers and has found that 70% of the distortion you hear comes from BL nonlinearities.  Here's a link if you are interested: https://www.klippel.de/pubs/alma2001/website_alma-Dateien/frame.htm  A speaker get's it's motor strength from BLi (B being the magnetic flux in the gap, L being the number of turns in the magnetic flux, and i being current).  Current is what drives the speaker as you can see.  Well when you halve the impedance, current increases.  This makes the speakers louder, but also increases distortion due to nonlinearities within the motor.  If you have a motor which provides a flat BL curve, then you wouldn't have this problem though.

If you would like some more links to even more information on this topic, I can provide it for you.  Just let me know.

Thank you, Steven Kephart, for the link and the comments.  I have been saying something similar for year.  Lower impedences = potential for more noise and distortion, every time.  This is why most home stereo is set up for 8 ohms, and why many high-quality drivers are higher resistances.  Indeed, back in the early 70's car speakers were 8 ohms just like home stereo, since this was the industry standard.  The change to 4 ohms happened sometime in the 80's as I recall, as the drive toward "louder" began.

The reason many OEM manufacturers are making 2-ohm speakers nowadays is that they do tend to "play louder" with a given size amplifier than will the same speaker at 4 or 8 ohms.  Thus, Ford or Chevy or Nissan can put 2-ohm drivers into a car and make it sound "louder" with a 6-watt factory radio for the same cost.  The average consumer seems to equate loud with "good" which is a real shame. 

I cringe anytime I have a customer (or friend) say "I want it to play loud."  This to me usually means "I don't really care what it sounds like."  A shame.  But "loud" is realtively easy to do.

Here's some interesting comments about this from Dan Wiggins, CEO of Adire Audio:

"All else being equal, current is current, BLi=ma, and how you get that current is immaterial. In car audio we tend to have lower impedance because back in the dark ages (the 80s - were some of you even alive then? ) high voltage switching power supplies were expensive. So you used the least amount of voltage possible, meaning that to maximize current flow at that low voltage rail you used low impedance drivers.

Now days, with switching FETs being cheap and plentiful, a 3 kW switching power supply is quite affordable. We stick to low impedance mainly because of market inertia. This is one area that I have a lot of hope for 42V car systems - higher voltage systems allows use with higher impedances."

I had a pair of soundstream 6x9's 2 ohms and recently swapped them for some pioneers that were 4 ohms cause they just sounded better.

So my q. is if i hook up two more 4 ohm 6x9s to get the 2 ohm load will i then be better off  or will it sound the same as 1 pair of 2ohm speakers?

superchuckles wrote:

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as long as the wattage used on the speaker is the same (i.e. if the speaker is being fed 400 volts at 1 amp, or if it's being fed 10 volts at 400 amps) the result should be the same as far as the speaker is concenred (in other words, i highly doubt that wiring up speakers to equate a 2 ohm load on an amp to gain say 500 watts per speaker will sound different or have any more distortion than it would if you wired them up as an 8 ohm load and just bought an amp that put out four times the wattage so that you would still end up with 500 watts per speaker)

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I recomend that you read the link I posted above.  It has a great deal of information on this topic throughout.  In fact, here's what Chris (Geolemon), the co-owner of Better Audio had to say on this: "Output level would still be higher though, even if "power" were technically the same - because of F=BLi... more current, more force, more output, higher excursions...AND higher distortions."

Read my first post to see where the distortion comes from.  Also to take this a step further, in the linked thread I asked this: "let's say same situation, but output is the same. So output is the same, but one has more current than voltage. Will the one with more current have more distortion, even though it's power level is lower?"

Dan Wiggins posted the answer: "Stephen and Geo, you're both right! Force truly is BLi, so given all else being equal, you need the same current to generate the same SPL in the drivers you're talking about.

Now, if you had one driver that needed X amps of current to generate Y Newtons of force, and a second driver that needed 0.5X amps to generate that same Y, then the second driver would have lower distortion. Of course, it's also 3 dB more efficient, meaning either BL doubled or mass was cut by 41%."