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Impedance switch, Help Yamaha owners (1 Viewer)

Barton Lynch

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Hi, hope you can help me with this.
My Yamaha receiver (RX-V595a) has been a work horse since I bought it. Compared to my previous Pioneer, this receiver almost never got hot and had enough power for everything. But, after I took it to service due to a "mysterious cause" that damaged the center channel output, I became a little paranoid. Call me weird but I am constantly touching it to see if it's warm and I don't seem to feel it as powerful as before. The authorized Yamaha center took good care of it, in fact they cleaned it so good I thought that they'd given me a new one, honest! But my paranoid self is so picky that I "think" it used to sound a little louder and use to run mildly warm (I didn't use to touch it though, It all started since it came back from the service center). So it all comes to this, does the impedance switch (don't remember in which position it was) has something to do with it? It is in the lower position (Reads like this in the manual: MAIN: If you use one pair of main speakers, the impedance of each speaker must be 8Ω or higher. If you use two pairs, it must be 16Ω or higher. CENTER The impedance of the speaker must be 8Ω or higher. REAR: The impedance of each speaker must be 8Ω or higher. ) now, will it make it louder if I change it? will it damage something? is it safe? My speakers are JBL HLS series, 8Ω all the way, but the rear ones are 6Ω. The upper position of the impedance switch read like this: (MAIN: If you use one pair of main speakers, the impedance of each speaker must be 4Ω or higher. If you use two pairs, it must be 8Ω or higher. CENTER The impedance of the speaker must be 6Ω or higher. REAR: The impedance of each speaker must be 6Ω or higher. ) The Question is: Where does the switch has to be set? according to my speaker set that is. Please help, I'm paranoid, you guys are cheaper than a shrink ;) (bad joke huh?) Anyone. Thanks in advance.
 

Chuck Kent

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Barton: Here is my reply to an earlier thread regarding lower impedence speakers and receivers...

Can you safely drive 6 ohm rated speakers with an 8 ohm rated receiver? IMO, most certainly!

Should you have any concerns?? Again, most certainly. But not (IMO) for some of the reasons given above.

Receiver failures indeed occur due to combinations of heat, high volume playback levels and surges. But none of these problems go away if one connects 8 ohm rated speakers to a receiver rated to drive 8 ohm loads (surges for one!) And likewise, these problems don't necessarily occur automatically if one connects speakers that have impedence ratings below 8 ohms.

What (IMO) does matter are a number of factors.

On the receiver side, the size and design of the heat sinks (also the inclusion of a fan or not), the number (and quality) of output devices per channel and the location of the receiver itself (whether or not it has access to plenty of ventilation) all lead to how well the receiver can deal with low load impedence and/or high playback volumes.

On the speaker side, there are mostly 2 main concerns. Impedence and sensitivity.

If a speaker has impedence measurements of less than 8 ohms, it will draw more current from the amp/receiver to return the same volume level back to you than one that is 8 ohms (if both have the same sensitivity maesurements.) The additional current drain WILL cause the amp/receiver to get noticeably hotter. (And if the receiver suffers from it's own problems, as I've noted above, then you will indeed have problems.)

But, if a less than 8 ohm speaker has a higher sensitivity, it may not draw enough (or in some cases, any) additional current to cause any problems. (An example would be an 8 ohm speaker with a sensitivity of 86db/watt/meter. If you compare it to a 4 ohm speaker that measures 89db/watt/meter, you may find that the 4 ohm speaker may not make the amp/receiver any hotter than the 8 ohm one would.)

Bottom line is that I believe most decent receivers can safely drive speaker loads of less than 8 ohms. Especially if you use some common sense on how loudly you play your setup. But like anything else in life, there are no free lunches...(and lots of things to consider if you're going to play things very loud and long.)

(One other thing to point out is how several makers deal with lower impedence speakers. Many include a 4/8 ohm switch on the speaker outputs. This switch lowers the potential power output available to the speakers by (an average of) 10 to 20 percent. Less wattage output means less current is needed. This translates to less heat generated. The reason for this switch is to more cost effectively pass UL or CSA heat safety ratings when feeding lower impedence loads. The switch allows receiver makers to save money by avoiding the use of more/better heat sinks or fans. This approach does work but should never be considered as necessary for low impedence drive capability.)
 

Barton Lynch

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Thanks Chuck, a little more techie talk than I'm used to but it helps. Still don't know where the switch should be and also if my mind it's just afraid to damage anything else, hence my paranoid aproach (find myself checking the heat than enjoying anything at all :frowning:) although I never really abused the receiver in the first place.
Anyone else?
 

Saurav

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Well, cutting out the techie parts from Chuck's post, this is what's left:

Bottom line is that I believe most decent receivers can safely drive speaker loads of less than 8 ohms. Especially if you use some common sense on how loudly you play your setup.
In your case, I agree with that statement. Leave it at 8 ohms, don't drive it too hard, and if you're playing it loud for long durations, keep an eye (or hand, as the case may be) on how warm your receiver is getting.
 

Richard Cook

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Hi Barton

Something else to check!

Some Yamaha amps, my 3090 includes, have a volume limiting switch on the rear panel

This cuts the sound by about 25%. Make sure that this is set at 100% so that the amp is working to full capacity.

My amp went off for a service once and it came back with the switch in the wrong position

'Worth having a look!!
 

Barton Lynch

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Thanx Richard, but, there is no such volume limiting switch anywhere, at least on my model.

Saurav, Thank You, i'll leave it there (the switch).
 

Chuck Kent

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Barton: Sorry if I rambled a bit from the earlier post.

Essentially, the switch is there to help keep the receiver from overheating. And overheating (whether all at once or over time) will cause the unit to fail sooner than it should.

The trade off is that if you run the switch in the 4 ohm setting, you run the risk of causing clipping (over driving) of the receiver's amps. And clipping can cause damage to a speaker's tweeter.

So which do you choose?

The 8 ohm setting is nearly always preferable, IF the receiver is not allowed to get too hot. (Some things that can help are to make sure it's ventilated as good as possible. Don't stack anything on top of it, no matter what the magazine ads may show. If your receiver is in an enclosed stand or cabinet, use some type of fan to circulate air into (or out of) the stand.)

But if your choice of locations means that you just can't keep the receiver from getting too hot, then you might want to consider the 4 ohm setting. Just try to keep the volume at reasonable levels.

Hope this helps better than before...
 

Barton Lynch

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Thanks Matthew.
Yes, Chuck, it helps better than before. Thank you very much, I know my mind is playing games on me. The receiver use to be always on the warm side, but again I never used to touch it, so it could always be like that and I never noticed it. I just have to get confident again and watch (and enjoy) a bunch of movies to settle in. It was all subjective though. BTW, I never stack anything on top of the unit and it is not inside any sort of cabinet, but... my room is small (really small) and loaded with A/V gear with no A/C. This is a tropical Country folks, an Oklahoma guy in Caracas, ahhh those snowy days of my childhood. Will adding a window A/C chill things a little bit? Not for me ;) for the equipment that is.It gets hot to the sweat after long periods of time. Thanx again.
 

Chuck Kent

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Yeah, an air conditioner could certainly help, both with the room/receiver temperature and the relative humidity (which can accelerate some types of corrosion.)

The obvious drawback is that is will be NOISY!
 

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