Question about Sony STR-DB940 Receiver

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Sony STR-DB940 Receiver Speaker Impedance Question

I know the manual talks about 4 and 8 ohm speaker loads, but my question is how low the load impedance can safely go. Basically, I want to wire the center channel output to a pair of speakers hanging off my Pioneer PDP-5020FD plasma TV. I figured I would wire them in parallel. I measured the ohms of each speaker; one is 6.8 and one is 7, so in parallel it would be around 3.4. Is that a safe load? It's not much below 4 ohms, and I know many amps can handle down to 2 ohms, but I don't know if my receiver will. Please help. Thanks!

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  • jsdittmer Mar 03, 2009

    Thanks Gene. I might not have described my situation well enough for you. The speakers are detachable from the plasma, so they are not hooked up to it at all now. I want to attach the center channel of my Sony STR-DB940 receiver amp to this speaker bar. The bar has two speakers. I would like to use both if possible. Right now I have the center channel of my receiver hooked to only one speaker.

    My question was that if I hooked up both speakers in parallel to the receiver, the load would be cut in half to around 3.4 ohms, and if in series it would be 13.8 ohms, would either work? It is the Sony STR-DB940 receiver amp that I want to hook to the speakers. I would do either based on a professional recommendation (or neither if the receiver won't handle it). The receiver specs only state 4 and 8 ohm scenarios, but it's a beefy receiver, so I was wondering if it will actually handle 3.4 ohms (since many can handle as low as 2 ohms). Maybe this is a question only for Sony, but I figured someone on here might know. It would be on everyday, but normally at pretty mild levels. I just didn't want to risk anything without professional advise.

    Thanks

    Jeff


  • Anonymous Mar 26, 2014

    i no the cumin speaker wires are 4ohm but is the rj output 8 ohm

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Whats the rating on the Plasma? How many watts at 4 ohms? If the plasma is rated 100 w at 8 ohm... hanging a 3.4 ohm load would put a lot of strain on the plasma's output amp. At 3.4 ohm the amp would be trying to delive close to 200 watts at full power. But it depends on how hot you normally run the volumn. Remember an amplifier output is AC volts. 1 ohm of resistance is close to a dead short. The amplifier would have to work its *** off to supply that type of power and would probably burn the output op-amps. If the outputs burn & it pumps any DC current through the speaker wire..the speakers would be toast...if not catch on fire. Try to keep the speaker load at or very cloe to the plasma's output load rating. Also if the plasma doesn't state it will handle loads down to 2 ohms...It probably won't.
Gene

Posted on Mar 03, 2009

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Since the Sony receiver has preamp outputs for all channels, you could use the center channel preamp output to drive the existing amplifier in the television set. This will avoid concerns over speaker impedance and make the cabling simpler as well. By the way, if you measured the speaker "impedance" with a DC ohmmeter, you haven't actually measured impedance. DC resistance is a scalar quantity measured with an ohmmeter, but impedance is a vector quantity consisting of resistance and reactance.

Posted on Jan 11, 2010

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hi pawanh75,

thanks in advance for a very informative setup that you have.

Here are some of possible mods , only if you like and can DIY

( or have someone to help you )


• Using a 6 ohms impedance for an 8 ohm impedance amp clearly

denotes that it heats up the output stages.

(please forgive my very technical words)


• One way to lessen the heat is to install a blower .

Use a 220V blower on top of the receiver.

( air should be in going up direction ).


• Before I proceed further please indicate if having the speaker

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when the volume is at medium to high level.


If it s running hot at zero level with speaker , please post.

If it is running hot even without speaker, post also


• It may also helps , if you have a powered subwoofer ( for the low's),

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Hi I purchased a sony av amplifier model STR-DB930 on e-bay a few months ago and I am using 3 ohm speakers from my old surround sound system. The output selector on the back of the unit is set to 4 ohms....


The lower number in Impedance specs is not a suggestion. It's a limit. 3 is not between 4 and 8.

Register and download the manual for free at retrevo.com

http://www.retrevo.com/support/Sony-STR-DB930-Receivers-manual/id/387bh934/t/2/

If you don't want to buy new speakers, settle for safer low volume levels.

You're going to kill that receiver driving a 3-ohm load. HTS-style speakers aren't reliably re-deployable to other electronics. Perhaps, if you have 4 speakers and they're similar you could wire them in SERIES and present a 6-ohm load to each channel.

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I have a str-de750 and a str-de597 both after less than 2 years of use flashed "protected" and are rendered useless to me.I will not purchase a 3rd one unless this can be resolved.FYI since the...


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My only rational guess besides the receivers having been defective is this.

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If you put four 4 ohm speakers together. The amplifier would see 1 ohm resistance. That is almost a short circuit.
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I founs some articles and For Sale posts:

http://toronto.kijiji.ca/c-buy-and-sell-electronics-Sony-STR-4800SD-Stereo-Receiver-135-OBO-W0QQAdIdZ243602516
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The power consumption figure shown in a photo below says "145W", which would be consistent with a 35 watt amplifier.

http://www.oaktreevintage.com/web_photos/Stereo_Receivers/Sony_STR-4800SD_Stereo_Reciever_collage.jpg

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I'm guessing these are separate issues.

Has either one ever worked and stopped suddenly?

From the manual:
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In other words, two 8-ohm speakers in parallel would yield a 4-ohm load.

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That model of receiver goes into protect mode when there is really
low
resistance or a short on your speakers/wires. It does it to protect the
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2) The speakers are below the rated minimum nominal impedance, causing the amplifier to strain and overheat

3) There is a problem within the amplifier that is causing this problem - this is not user repairable.

I'd try another pair of speakers which are rated at 8 ohm nominal impedance and give it a trial. At the same time, monitor the heat output from the unit (note that modern amplifier sections do run hot). If the unit runs extremely hot at a low volume and still shuts down on 8 ohm speakers, it's time for service or replacement depending on value.

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