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#1326996 - 02/22/08 05:10 PM Very good info on using 2 ohm speakers with just a HU unit......no amp
soundhd
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I recently replaced the OEM speakers and HU in my truck....alot of looking around on the net trying to find out if the aftermarket HU's could handle the load of four 2 ohm speakers...Most replies were no it cannot, HU's amp will fail or burn up.....etc....
Well I have a new Pioneer DEH-P47DH HU running four Infinity Reference 2 ohm speakers and no problems....
Below is a copy of a note sent to the mobile retailers of the Harman Kardon line (they own JBL & Infinity) and it makes for very interesting reading....

“Hey Guys,

Andy from Harman here...I'd like to clear this up, if I can without having to get too technical.

First, we didn't just decide to make our speakers 2-ohms without doing some serious testing and verifying that it works and that the "technology" is sound. We tested lots of factory and aftermarket head units and none of them failed. Many made more power. A few made less distortion (which was a surprise) AND more power, but none of them failed. In the two years that we've been selling 2-ohm speakers, we have NEVER had a radio fail because it's been hooked up to our speakers. In every case where an installer has suspected that our speakers have caused problems, we've helped them trace wires and measure resistance and have found some other problem...poor connections, short circuits and the like.

In our test, the head unit was connected to the speakers with a 1-foot pieces of wire. That's short compared to the lengths of wire that connect your head unit to your speakers in your car and the wire contributes some additional resistance. Furthermore, after you've played the speakers for a few minutes in the car, the voice coils get hot (that's one of the laws of Physics) and their resistance increases. When that happens, our speakers look to the radio like a 4-ohm speaker and a 4-ohm speakaer looks more like a 5.5-ohm speaker. We're simply giving you back the power that you lose when you actually install the speakers in the car.

Some of you might be surprised to discover that MANY factory speakers are, in fact, 2-ohm speakers and replacing them with 4-ohm speakers DEGRADES the performance of the head unit.”


“I am an expert, but I'm not an engineer. I've been doing this for over 20 years. I was a retail installer for 10 years. I've taught installers. I've won competitions with my own cars and built cars for customers who have won also. I now work for a manufacturer and my job as a Product Marketing Manager is to help engineers understand what customers want to buy and help marketers, salespeople and customers understand how things work and how best to use the gear. I try to do that in a way that's understandable, rather than to just spout a bunch of techno-babble or talk so far above everyone that no one can understand it. Fortunately, I have access to some of the best audio engineers in the world. So...when I have a question, I can always get the real answer that I can turn into something that most people get, easily.

First, I'd like for us to deal with things that are known rather than making statements like, "I'm sure", "I think", "I'll bet", or the like.

Next, we don't make aftermarket head units anymore, but I've personally installed hundreds of them over the last 20 years. We do make thousands of factory systems and those factory systems use similar amplifier technology that's included in today's aftermarket head units. The amplifiers in head units are not often "designed" by the manufacturer of the head unit. The resistors, capacitors and inductors that are used aren't designed by the head unit designer either. They are CHOSEN. The amplifier in the head unit is an IC--Integrated Circuit, and it has its own set of specifications that help the head unit designer choose the right one from the company that supplies it.

The specifications for the IC amplifiers chosen by head unit manufacurers include a minimum impedance specification and it's tested using resistors and a measure of the current that has to be delivered driving that resistor. Those specifications are stated using the customary 2-ohm, 4-ohm, and 8-ohm conventions. So the answer to the statement about the head unit manufacturer considering the speaker wire, the increase in impedance due to wire and heat is "NO". That resolution isn't available.

The answer to the other difficulty you pose is that we're talking about power here, even though I generalized when I stated that "Performance" is often degraded. What is degraded is the amount of power that the head unit provides when a factory-installed 2-ohm speaker is removed and a 4-ohm speaker is installed. Whether the new one plays louder is dependent on several factors: the sensitivity of the speaker compared to the one being replaced and the difference in its frequency response. 3dB higher sensitivity may cause the speaker to play at the same level as the one being replaced and more than 3dB may cause an even greater difference. Whether you like the frequency response better is subjective. The LAW (Ohm's law and the Power Law) inidcates that the radio WILL make less power.

What makes all of this more difficult than your scenario about buying a 60-watt speaker and a 60-watt amplifier is that amplifiers are tested using resistors and enjoyed when they're driving speakers. Speakers are not resistors. Their impedance is not resistance and the nominal impedance rating is just that--nominal--that means "In name only". Look it up in Websters. To better understand what happens, one has to better understand how speakers work and how power is transferred to them and used by them. What I'm saying as a speaker manufacturer is that we have an oppportunity to provide a speaker that makes better use of the power available from any amplifier and that's what we have done.We've adjusted the impedance of the speaker to optimize the total load (which is what the amplifier's rating indicates) so that you, the customer gets the best performance available from his or her system when it's installed in the car.

Why would we do that? Because we're customers too and as customers we expect the companies from whom we buy products to use their expertise to provide us a superior experience. We always stand behind what we build 100% and I invite any of you who experience any difficulty driving your Infinity speakers with your head unit to contact me via PM. I'll make sure we take care of you.”


--------------------------------------------------------------------------------

Andy Wehmeyer
Product Marketing Manager
Harman Consumer Group

Here’s the link to the entire thread.

http://community.crutchfield.com/forums/thread/15414.aspx

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#1327199 - 02/23/08 06:03 AM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: soundhd]
keep_hope_alive Moderator
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that's a nice article, but as expected i have a couple issues. first, amplifiers produce more distortion at impedance loads below their rating, not less. amplifiers also produce more heat at lower impedance loads.

i've mentioned before that many OEM speakers are 2 ohm and should be replaced with a 2 ohm speaker, but installing a 4 ohm speaker will only result in a reduction in output. it's my understanding that the 2-ohm OEM market is the reason the speakers were made in the first place. there are several advantages to running a higher impedance load - such as an increase in dampening factor, reduction in heat, and reduced distortion.

the big issue i see is from heat - that will cause the most damage to your hu (depending on volume and settings).

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#1327202 - 02/23/08 06:25 AM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: keep_hope_alive]
keep_hope_alive Moderator
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after reading the Crutchfield thread one thing stood out: the impedance cure of the infinity speakers shows they should be labeled as 3 ohm. at no point does the curve go to 2 ohms.


that curve is from a 3 ohm speaker. that explains why there isn't as much of an issue. while your HU will certainly get hotter, the difference between 2 and 3 ohms is huge.

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#1327286 - 02/23/08 08:52 AM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: soundhd]
soundhd
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I do understand that having a seperate amplifier(s) is better all around.....less distortion, more power which means more headroom and cleaner sound when you are playing music at "extremly high levels"....but for those who are on a budget and do not have a need for sub-woofers and large amplifiers and play their music at "normal levels" this information can be very benefitial. Knowing that a HU's internal amp can drive 2 ohm speakers with out to much worry is important. At this level one does not need to run new power and ground cables to the battery, factory speaker wiring can be reused and with the right adapters installation can be pretty easy, there is no need to purchase and install aftermarket amplifiers and new speaker cabling.
The most inexpensive way to get a better sounding system is to replace the speakers....most mid level and even some premium OEM audio systems do not sound very well and most of that is the fault of cheap speakers.....
After one does replace the OEM speakers one can always add a aftermarket HU or install amps, sound processers, eq's and sub-woofers later. The speakers would have to be replaced anyway so why not start there first.
It is just nice to know that the higher end 2 and 4 ohm aftermarket speakers will work with OEM and aftermarket HU's without causing any problems.

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#1327688 - 02/23/08 06:45 PM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: soundhd]
keep_hope_alive Moderator
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[no] that article does not prove that a HU can run a 2 ohm speaker. all it says is that a 3 ohm speaker has been tested and works fine.

those infinity speakers pictured are NOT 2 ohm. Infinity is stupid for even stating they are if the curve does indeed look like that.

i'll measure the impedance curve of some myself and see what i get. i know a couple people with them, hopefully i can pull them out for a few minutes.

running 2 (3) ohm speakers on a HU can cause problems, and has caused problems for many consumers. it's buyer beware and good luck.

most speakers do not sound good in a car because there is no treatment or controlled enclosure/environment. i don't think that many aftermarket speakers sound good in an untreated enclosure/door/dash/deck/trunk/etc.

i also think that most coaxial speakers sound like crap. many factory systems sound better than <$150 aftermarket speakers.

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#1327852 - 02/24/08 06:04 AM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: keep_hope_alive]
soundhd
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Yes, I do agree with you that the speakers that I was/am dealing with now are really 3 ohm speakers....thats probably why (at least so far) I am not having any problems.....but I can tell you that the sound quality of these after market speakers (Infinty Reference) is so far beyond that of the stock factory OEM speakers........it is very close to having a GM factory Bose system in my truck (We also own a 2000 Corvette that has a Bose system...so I am able to compare)...an again I do agree that alot of the lower level after market speakers do not sound that great.....I guess as my reply above states using higher end after market speakers (if they will fit....in my situation my first choice was the JBL power series but the depth requirments were so they would not fit and the same was for the Infinity Kappa series....so this is why I wnrt with the Infinity Refernce series)is the most inexpensive way to improve your sound if you are on a budget or at least the first step in a complete system replacement, new HU, controler,amps, speaker wiring, su-woofers, ect......
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#1327983 - 02/24/08 01:52 PM Re: Very good info on using 2 ohm speakers with just a HU unit......no amp [Re: soundhd]
keep_hope_alive Moderator
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overall i think the Kappa series are some of the better sounding coaxial speakers i've heard. I like Eclipse a bit more though, but i haven't had a good listening session with them for two years. I don't know what the new Eclipse speakers sound like.
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