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General discussion

Help - I need a new receiver - please someone explain ohms!

May 9, 2005 12:13AM PDT

I am looking for a stereo receiver for nice sounding older A and B shelf speakers and aux imputs for computer and tv, but not surround sound. I need something simple where you just plug in the speakers and go - (I'm old school - just care about the sound!). I don't want the remote to be the only control for anything. And I don't understand the Ohms and impedence thing, but I think it might be important. Somebody help! I am running Infinity Alpha 20 (8 ohms - nominal impedence) and Klipsch (KG 2.2 - I have no idea about the impedence - I don't see it anywhere, but they are from about 1990 or earlier and they sounded great with my old Onkyo receiver from the same period). I want to plug those into Speakers A and Speakers B, and as I said, just hit "play". I have a CD player to plug in and a TV, and would also like a couple of additional aux imputs for my computers for when I play music on them.

What should I buy? Can someone explain impedence and Ohms to me?

Discussion is locked

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receivers and ohms
May 9, 2005 3:42AM PDT

The number of stereo receivers available has shrunk to almost nothing in the last five years or so. Receivers are generally rated to support 8 ohm nominal impedance speakers. Problem is, many speakers drop to 4 ohms or less at some point of their frequency range. This wouldn?t normally be a problem unless the speakers were being played at the upper power limits of the receiver, which could cause the receiver to overheat and go into protection mode.

The problem with running two sets of speakers concurrently is that the impedance seen by the receiver halves. Most speaker switching (A+B) is wired in parallel, so the load seen is 8/2=4 ohms. But if the speakers drop down to 4 ohms at some point in their range, then the load could go as low as 2 ohms. Each time the impedance decreases, the receiver has to provide more current to drive them to the same level. A reasonably trustworthy spec is if the receiver can deliver in the neighbourhood of twice the output power (ignore dynamic power figures) at half the impedance, ie: 100wpc at 8 ohms, 200wpc at 4 ohms.

Another wrinkle with your set-up is that the Klipsches have a sensitivity of 93dB@1 watt/metre, while the Infinitys are only 88dB. If you drive both sets at once, the Klipsches will be considerably louder ? you should have noticed this in your previous set-up as well. If you?re running both sets at once, I?d recommend something in the 70-100wpc range with reasonable current delivery.

You could just replace your old Onkyo with a new one like this: http://www.us.onkyo.com/model.cfm?m=TX-8511&class=Receiver&p=i

or you could try something from Yamaha like this: http://www.yamaha.com/yec/products/receivers/RX777.htm

or you could move to a more up-market receiver like this Rotel offering: http://www.rotel.com/products/specs/rx1052.htm

or you could buy an integrated amplifier and a tuner (gives you more flexibility of amplifier choices) like either of the following two integrateds:
http://www.nadelectronics.com/hifi_amplifiers/C352_framset.htm

http://www.cambridgeaudio.com/summary.php?PID=13&Title=Azur%20640A.%20The%20ultimate%20award%20winning%20integrated%20amplifier

Hope this didn?t muddy the water more. Cheers.

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Home Theater Receiver
Jun 30, 2005 5:45AM PDT

I read your post answer regarding Ohms for a receiver and I trust the same applies to HTR's (home theater receivers).

I recently purchased a Yamaha Model: HTR-5830SL
http://www.yamaha.com/yec/products/HTIB/HTR5830.htm

The unit seems to be heating up and shutting down.

Am running large speakers for front Cerwin Vega's l/r at 4 ohms crossfaded from a JBL 8ohms sub, additionally have a SONY 8ohm 100watt sub running directly off the unit, my surrounds are 6 ohm Yamaha 220 watt tower speakers. My center speaker is a JBL at 8ohms. The receiver has two Ohm selections, 8 and 6, so last night I lowered it to 6 to see if it changes the overheat issue.

The overheat happens when running the unit at -4 or higher on the master volume.

Yamaha service thinks the problem is related to the Cerwin's drawing too much power at a high volume (I dont know the watt rating of the Cerwin's - they do have a 3 amp fuse on each)

Any guidance is well appreciated.

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Don't Run at Full Volume
Jun 30, 2005 10:55AM PDT

You will save your hearing as well as your speakers and receiver.

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Not even close
Jun 30, 2005 2:42PM PDT

You don't have NEARLY enough power in the reciever to do this right. You need ( sorry) about $400-$500 more reciever. Something that is capable of 4ohms. What you have now is not. Better yet (sorry again) retire the Cerwin Vegas, they haven't made a decent speaker since the 80's. Not efficient and really muddy in the mids and lows.