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Old 24th November 2011, 09:03 AM   #1
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Question Compatible with 4–8 ohms output?

Hey all,
I was just reading the manual for my Definitive Technologies CLR2300 center channel and I'm a bit confused with this statement.

"Nominal Impedance:
Compatible with 4 – 8 ohms outputs
(set amp on 4 ohms if you have a choice)"

I've never had an amp that lets me chose what ohms to use... usually the speaker tells the amp what ohms to run at. And what happens with the crossover?

Definitive Technology - C/L/R2300
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Old 24th November 2011, 01:05 PM   #2
DrDyna is online now DrDyna  United States
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It just means that the impedance of the speaker moves around with frequency, as most speakers do. It's an "8 ohm" speaker but that doesn't mean that at some frequencies, it's not down around 4 ohms, or even lower. Some amplifiers do have an impedance switch, but that's usually if they're unstable at 4 ohms, or have an output transformer like many tube amplifiers do.

If you've got a decent HT receiver, I wouldn't worry about it too much.
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Old 24th November 2011, 01:40 PM   #3
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Not worried, just curious. Still not making sense to me. I have 4 and 8 ohm speakers and amps stable at 4ohms. If they are saying set it to 4 ohm, I would imagine it's a 4ohm speaker and the crossover is made for 4ohms. I'm just not understanding what happens with the crossover. When I build crossover, or take them out of broken speakers, they are either 8ohm or 4ohm, never both... unless you have a jumper or a switch in the path.
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Old 24th November 2011, 02:24 PM   #4
Ile is offline Ile  Finland
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Quote:
Originally Posted by nonsuchpro View Post
I'm just not understanding what happens with the crossover.
Nothing.

Switch lower amps DC supply rails to prevent end stages to melt with 4 ohm impedance.
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Old 24th November 2011, 02:29 PM   #5
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So... crossover points don't change?
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Old 24th November 2011, 02:41 PM   #6
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Quote:
Originally Posted by nonsuchpro View Post
So... crossover points don't change?
The passive crossover in your speaker is designed for the components used in the speaker, which have a usual nominal rating of 2,4, 8 or 16 ohms, even though speakers generally are only their nominal rating over a very narrow range of frequencies.

The amplifier provides voltage to the crossover/speaker, which varies in impedance throughout the entire frequency range.
The amplifier does not affect the crossover.
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Old 24th November 2011, 03:28 PM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
a 4 to 8 ohms speaker generally has a higher impedance treble driver usually around 8ohms.
It also usually has a 4ohm bass/mid driver or a pair of 8ohm bass/mid drivers arranged in parallel.

These types of speakers present a substantially 4ohms impedance to the majority of current coming from the amplifier.

4ohm capable amplifier is different from 4r0 stable amplifier in my book.

To drive a 4 to 8ohms speaker, the amplifier specification should state it is suitable to drive 4ohms speaker/s.
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Old 24th November 2011, 03:50 PM   #8
DrDyna is online now DrDyna  United States
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Quote:
Originally Posted by nonsuchpro View Post
Not worried, just curious. Still not making sense to me. I have 4 and 8 ohm speakers and amps stable at 4ohms. If they are saying set it to 4 ohm, I would imagine it's a 4ohm speaker and the crossover is made for 4ohms. I'm just not understanding what happens with the crossover. When I build crossover, or take them out of broken speakers, they are either 8ohm or 4ohm, never both... unless you have a jumper or a switch in the path.
Right, the confusion is simply with the "nominal" rating that speaker manufacturers use. It's an "average". When you have a driver that has a sticker on it that says "8 ohms" it's most likely an average, as the impedance varies depending on the frequency that's being fed into it. Take a look at the picture I've attached.

The speaker you have might just be an 8 ohm nominal speaker, but at certain frequencies it's down at 4 ohms, or even lower - and has enough of it's operation take place at 4 ohms to warrant warning people who don't have a 4 ohm stable amplifier (or who have output transformers) to use the 4 ohm taps, just to be on the safe side.
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