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Impedance Query again - sorry! Yes or no?

 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 142
Registered: Sep-04
Sorry to bring this up again, guys....

I just want to recap again:

Is it okay to run 4ohm speakers with a 6ohm rated amp? Yes, no, or maybe?

I've been trawling the archives and seem to have lost all the threads where we spoke before about it. I think I know what impedance is, but just can't get my head around it in practice.

And if impedance changes during use, then what are the variables? I mean - most equipment says:
"4-6 ohms" or "6-8 ohms".

Duh! No, I'm lost again!

Thanks for your patience,

V

 

J. Vigne
Unregistered guest

The problem exists in the term "nominal" impedance. What that represents is the broad average impedance of the speaker's response curve. Only by looking at the actual data for a given speaker can you know for certain what the real impedance swing amounts to. Nominal 8 Ohm speakers may still have a dip beneath 4 Ohms and go as high as 65-70 Ohms. Whether your amplifier will drive the load is a "suck it" and see what happens scenario. Many amplifer manufacturers have begun to put printed restrictions on their equipment that offer them some protection when the same speaker is continually attached to their amplifier and the volume is cranked. After the first warranty repair, the amp maker can opt out of covering any further damage. (Blow me once ... ) Many amps can drive a low impedance load but will be rated for higher impedance as a protection for the amplifier maker. Many amps can drive a lower impedance load as long as the volume is kept low. Most amplifier makers won't tell you what they will actually drive because that might encourage abuse. With the large number of speakers on the market, it is also very difficult for an amplifier maker to know exactly what speakers their product can work with.

If you can find the impedance swing of your speakers and a test of your amplifer that determines the load variables you can begin to guess what combinations might work. Still the problem exists that an amplifier is asked to only drive a load resistor that is one resistance value. That load resistor doesn't actually reflect the variables the amplfier will find when it is connected to a real world loudspeaker. Your dealer might be the best place to ask for more advice.



 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 2065
Registered: Dec-03
Mr. vigne is excactly correct.

And when it comes to an amplifier, going up in impedance on the speaker
is not the problem but going low is. "Just to make sure you knew"

And like Jan said you need to find the impedance swing of the speakers to really
determine weather they will hurt your amp or not.
(Or call the mamufacturer of both)

If your amp is rated at 6 ohms then generally they can take a lower impedance
load than one rated at 8 so if your speakers dip to 4 ohms once or twice
accross the full spectrum they will probably be fine on a 6 ohm rated amp.
But if they dip to 2 ohms then 4 quite a bit then maybe go back up to 8
or higher then there probably not good for your 6 ohm amp.

That's just a generality not a sure thing but should give you the right idea!
 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 143
Registered: Sep-04
Thankyou - J. and Kegger.

I will contact the dealer where I bought the AS 4 ohmers and the 6 ohm amp.

The problem exists now only with the spares I have left over from my recent upgrades. The Gales were originally meant to go with the Cambridge, because they are impedance matched. Now that I've heard them on the NAD, I don't want to change them and they match impedance wise, just fine.... Plus, I don't have any need for vinyl upstairs (dirty hands while working - CDs are more convenient) and the NAD is the one with the phono-preamp onboard, now downstairs with the Gales.

Actually, I think that CA A5 (6 ohm) is actually a bit of a lemon, don't you think?

Since I've bought it, I've had more problems and queries with it than both my old NADs. Actually, I don't feel it even sounds as good!

I'm thinking now of selling it on and putting the money into a NAD 320BEE. All NADs as far as I know give you impedance choice in the shape of the toggle switch at the back and 'soft clipping' for extra protection for loud parties. Can't go wrong really. I've been uncomfortable with the Cambridge ever since I bought it.

I could change the speakers, of course - or buy the Cambridge Audio phono preamp. I'll give the options some thought over the next few weeks.

While I'm here.... anyone got any opinions on the Cambridge Audio PM01 PRE-AMP for turntables? Any good?

Thanks again for your helpful responses,

V



 

J. Vigne
Unregistered guest

No idea on the phono stage.

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