Correct impedance on new amp??? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 03-20-2004, 06:27 AM - Thread Starter
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Hi Guys!

I am currently building up my first HT and today I purchased a Pioneer VSX-912 A/V receiver and a Canton Movie 6 CX pack (5.1). I noticed in the Pioneer manual that the requirements are for 8 or 16 Ohm speaker impedance. However in the Canton manual it says "Speaker Impedance - 4...8 Ohm". Can anyone help with this? I assume it is ok but I thought I had better check. :rolleyes:

Thanks guys!!

Cam

P.S Wasn't sure whether to post in Amps or Speakers so thought I'd try here first...
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post #2 of 5 Old 03-20-2004, 01:18 PM
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The Pioneer receiver will overload attempting to push full power into a speaker whose impedance average droops below 8 ohms, which is what Canton speakers rated at 4-8 ohms typically do. On paper, this is a mis-match.

What determines whether this receiver will handle these speakers is how much sound you attempt to reproduce. Even the weakest amp will push the lowest-impedance speaker if you keep the volume control low enough.

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post #3 of 5 Old 03-20-2004, 03:06 PM
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Quote:
Originally posted by Cammo
Hi Guys!

I am currently building up my first HT and today I purchased a Pioneer VSX-912 A/V receiver and a Canton Movie 6 CX pack (5.1). I noticed in the Pioneer manual that the requirements are for 8 or 16 Ohm speaker impedance. However in the Canton manual it says "Speaker Impedance - 4...8 Ohm". Can anyone help with this? I assume it is ok but I thought I had better check. :rolleyes:

Thanks guys!!

Cam

P.S Wasn't sure whether to post in Amps or Speakers so thought I'd try here first...
Cammo,

You need to match the capability of the amp / receiver to the speakers.

For a given voltage - it requires more current to flow through a low impedance than a
higher impedance. Thus 16 ohm speakers are the easiest to drive, 8 ohm speakers
are more difficult, and 4 ohm speakers are still more difficult to drive.

The most common speaker impedances are 4 ohm and 8 ohm, the latter the more common of the two.

The amp in you receiver doesn't have the current reserves to put out a lot of current -
hence it can't drive 4 ohm speakers at full output. As Larry states - the Pioneer is
ill suited to drive the Cantons.

However, Larry is also correct that if you keep the volume control low enough so that
don't tax the receiver - it will still play through those speakers.

However, if you crank up the volume - you could overtax the receiver - it won't be able
to deliver all the current required. If this happens, the receiver will "clip" the top off the
waveform - because it can't go up to the full voltage being asked of it because it ran out
of current into an impedance lower than it's rated for.

If this happens - you will hear distortion - a "crackly" quality to the sound. If this happens,
turn down the volume QUICK. If the amplifier clips - it produces distortion due to the
clipped wave - and this is real bad for speakers - it will fry the tweeters.

More speakers are destroyed by amps / receivers with too little power, or that can't drive
a too low impedance.

If it sounds OK - you're probably OK. But just be mindful that if you crank up the volume
control with that combination of receiver and speakers - you're flirting with the possibility
of frying the speakers. So be careful with that volume control.

Dr. Gregory Greenman
Physicist
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post #4 of 5 Old 03-20-2004, 04:02 PM - Thread Starter
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Greg & Larry,

Thanks for your helpful tips! I am only a HT newbie and I really appreciate this forum!!!

I was doing some speaker positioning testing this morning and a good level for the movie I was watching as a test (LOTR1) was about -20Db. I am not sure if this means much at all but does that sound about right?? The amp didn't seem to get very hot at all and the sound was great (in my newbie opinion) but I hope I am not overpowering it.. I have no idea what max volume is so I am not sure if it is at 1/4, 1/2, 3/4 or whatever power.

Any more thoughts?? Should I take the speakers back? They really suit the room I am building and sound great so I am a bit hesitant however if it is obvious that they are unsuited and may cause problems then I will swiftly return them..

Thanks in advance :)

Cam
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post #5 of 5 Old 05-05-2004, 08:14 PM
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Quote:
More speakers are destroyed by amps / receivers with too little power, or that can't drive
Hi Morbius,
I'm doing a search about ohms and its definition. Came upon this thread with your excellent layman explanation.

Still trying to grasp its theory .... does that mean if given the choice to set impedance on my receiver, it's better to set at the lowest ohms, in order to drive as many ohm-type speakers as possible? Or from another perspective, when buying receiver/amps it's better to choose lower-ohm capability (<8 ohms) or should it be vice versa (speakers should be 8ohms above)?

Thanks in advance

Clatto! Verata! Nnyaarrghahum(coughcough)!!
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