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speaker ohms [message #14697]

Fri, 03 September 2004 12:25

Calvin
Messages: 1
Registered: May 2009

Esquire

Why are there different ohms speakers? Why isn't there a standard that all use?

/Calvin

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Re: speaker ohms [message #14698 is a reply to message #14697]

Fri, 03 September 2004 12:57

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

The standard is 8 ohms, but some applications work better with different values. 4 ohm is usually used for auto sound where the supply voltage is lower and 4 ohm drivers increase sensitivity. 4 or 6 ohms are sometimes used in home audio also to gain additional sensitivity (if the amp will handle the increased aperage draw). 16 ohms is often seen in pro-audio horn drivers, which allows easier level matching with lower sensitivity cone drivers. 4 ohm and 16 ohm drivers are often used with multiple driver speakers to make it easier to gain a total impedance of 8 ohms (or what ever is desired).

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Details on 16 ohms please [message #14699 is a reply to message #14698]

Sat, 04 September 2004 18:55

GarMan
Messages: 960
Registered: May 2009

Illuminati (2nd Degree)

Hey Bill,

Can you elaborate on the use of 16 ohms in pro-audio horns please. An example would be great.

thanks,
Gar.

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Re: Details on 16 ohms please [message #14700 is a reply to message #14699]

Sun, 05 September 2004 07:50

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

Sure- a JBL 2426. This is available in both 8 and 16 ohm versions, and you usually see 16 used. Since this has 110 dB sensitivity it's only logical to use a 16 ohm coil to better match it with a 100dB woofer section. Another advantage here is that as you raise the impedance you lower the crossover point, or, conversely, lower the size of the crossover components to maintain the same crossover frequency, which means that for a 16 ohm driver versus 8 ohm the crossover component sizes are halved, which saves serious money in the case of high-power high order crossovers.

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split impedance [message #14701 is a reply to message #14700]

Sun, 05 September 2004 10:22

Oberon
Messages: 20
Registered: May 2009

Chancellor

Some amplifiers don't like impedance changes like this. If biamped, no problem but if not it might be depending on what amp is used.

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Re: split impedance [message #14702 is a reply to message #14701]

Sun, 05 September 2004 10:42

Bill Martinelli
Messages: 677
Registered: May 2009

Illuminati (1st Degree)

Please explain how the amplifier can see or sense individual components past the passive crossover? I always thought the amp would only see the total load and impeadance that is given at the point of entry, the crossover.

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Re: split impedance [message #14703 is a reply to message #14702]

Sun, 05 September 2004 11:58

Oberon
Messages: 20
Registered: May 2009

Chancellor

The crossover is a splitter that hands off to the drivers. Whatever impedance they are is seen by the amp in their range.

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Re: split impedance [message #14707 is a reply to message #14703]

Mon, 06 September 2004 07:27

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

True, but as long as the load impedance is within the amps ability to drive it the amp doesn't care. Differing impedances would bother a constant current amp, so amps are constant voltage devices for just that reason. Besides, impedance is always a nominal figure. The typical in-use impedance of an 8 ohm woofer actually runs from a low of perhaps 5 ohms to a high of 50 ohms or more, depending on the frequency at which you measure.

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Re: split impedance [message #14708 is a reply to message #14707]

Mon, 06 September 2004 10:39

Oberon
Messages: 20
Registered: May 2009

Chancellor

Low DF amps are what I'm talking about. Amps with low DF don't like impedance changes.

http://www.classic-audio.com/marantz/mdampingfactor.html

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Re: split impedance [message #14711 is a reply to message #14708]

Mon, 06 September 2004 20:01

Bill Martinelli
Messages: 677
Registered: May 2009

Illuminati (1st Degree)

Interesting read. Thanks for the link. I've always thought of the crossover as a combiner as much as a splitter. Never ran into problems with various impeadance drivers before.

Bill

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