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Should I set my receiver's impedance switch to 4 ohms?

post #1 of 8
1/24/13 at 7:18pm
Thread Starter 
I am using an older Sony str-de845 receiver rated at 100w/channel and have a 5.1 setup. I own the Pioneer speakers designed by Andrew Jones. For the fronts I have a pair of the sp-fs52s and the sp-c22 center speaker. I have a pair of the sp-bs21s for the rears. I am also using the Hsu Stf-2 subwoofer with the crossover setting in the receiver set to 90hz. All of the speakers have an impedance of 6 ohms. The problem I am having with my receiver is that the center channel sounds harsh. I previously owned some JBL satellite speakers and had the same problem with the center channel. I wondered if my receiver was the problem so I bought the Yamaha rx-v373 receiver and hooked it up to my speakers. The center channel was no longer harsh so something is up with my Sony receiver. I returned the Yamaha receiver because I only intended to use it to see if there was something wrong with my Sony receiver.

My Sony receiver has an impedance selector switch on the back for the front left and right speakers that I have been setting at 8 ohms but the center channel sounds pretty harsh (meaning too bright) so I have experimented setting the switch to the 4 ohm setting and doing this gets rid of most of the harshness in the center channel. However, my receiver gets pretty warm doing this and I am concerned this isn't safe. My receiver never goes into protection mode and I don't hear any clipping but I am concerned about the heat. I will note that with the impedance selector switch set to 8 ohms, the center channel sounds clearer and when I set the switch to 4 ohms, the center channel is no longer harsh/bright sounding but the sound does because very slightly muffled. It does not bother me and is hardly noticeable but I am wondering if anyone knows why this would be the case. Is the muffled sound at the 4 ohm setting a result of clipping? If it is safe to run my receiver with the impedance switch set to 4 ohms I would prefer to do that because it gets rid of the harshness in the center channel.
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post #2 of 8
1/24/13 at 9:39pm
Quote:
Originally Posted by dave2441 View Post

I returned the Yamaha receiver because I only intended to use it to see if there was something wrong with my Sony receiver.

Thanks for fessing up to adding to the cost of consumer electronics. Didn't anything about that make you feel the least bit guilty?
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post #3 of 8
1/25/13 at 3:22am
Thread Starter 
I did feel guilty but I suspected that there was something wrong with the receiver and felt I had no other option to test this without buying a new one and then returning it. I would have borrowed a receiver from a friend or family member but I do not have a friend or family member with a receiver. I am a good citizen and this is not something I would do again under normal circumstances.
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post #4 of 8
1/25/13 at 6:21am
Quote:
Originally Posted by dave2441 View Post

I am using an older Sony str-de845 receiver rated at 100w/channel and have a 5.1 setup. I own the Pioneer speakers designed by Andrew Jones. For the fronts I have a pair of the sp-fs52s and the sp-c22 center speaker. I have a pair of the sp-bs21s for the rears. I am also using the Hsu Stf-2 subwoofer with the crossover setting in the receiver set to 90hz. All of the speakers have an impedance of 6 ohms. The problem I am having with my receiver is that the center channel sounds harsh. I previously owned some JBL satellite speakers and had the same problem with the center channel. I wondered if my receiver was the problem so I bought the Yamaha rx-v373 receiver and hooked it up to my speakers. The center channel was no longer harsh so something is up with my Sony receiver. I returned the Yamaha receiver because I only intended to use it to see if there was something wrong with my Sony receiver.

My Sony receiver has an impedance selector switch on the back for the front left and right speakers that I have been setting at 8 ohms but the center channel sounds pretty harsh (meaning too bright) so I have experimented setting the switch to the 4 ohm setting and doing this gets rid of most of the harshness in the center channel. However, my receiver gets pretty warm doing this and I am concerned this isn't safe. My receiver never goes into protection mode and I don't hear any clipping but I am concerned about the heat. I will note that with the impedance selector switch set to 8 ohms, the center channel sounds clearer and when I set the switch to 4 ohms, the center channel is no longer harsh/bright sounding but the sound does because very slightly muffled. It does not bother me and is hardly noticeable but I am wondering if anyone knows why this would be the case. Is the muffled sound at the 4 ohm setting a result of clipping? If it is safe to run my receiver with the impedance switch set to 4 ohms I would prefer to do that because it gets rid of the harshness in the center channel.

odd, AFAIK, whar the 4 ohm switch is supposed to do is limit available voltage, and available power, to avoid overheating the receiver when running the more challenging lower impedance speakers. It's not like a transformer tap for a tube amp - there is no need for solid state amplifictiation devices. It should not have an effect on sound at all unless you push hard enough to cause clipping with the 4 ohm setting that would not occur at the 8 ohm setting..
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post #5 of 8
1/25/13 at 6:50am
Quote:
Originally Posted by dave2441 View Post


My Sony receiver has an impedance selector switch on the back for the front left and right speakers that I have been setting at 8 ohms but the center channel sounds pretty harsh (meaning too bright) so I have experimented setting the switch to the 4 ohm setting and doing this gets rid of most of the harshness in the center channel.

I can't imagine why that would be. This particular switch on AVRs is only really meaningful for bench testing, and should have absolutely minimal effect on sound quality in a real world audio system.
Quote:
However, my receiver gets pretty warm doing this and I am concerned this isn't safe.

"Pretty warm" is a very subjective phrase, and it is impossible to know what it really means. You might obtain a IR thermometer and take readings of the case temperature.



Under $10 on eBay and they actually work!

Usually actual AVR overheating is due to poor ventilation.
Quote:
I will note that with the impedance selector switch set to 8 ohms, the center channel sounds clearer and when I set the switch to 4 ohms, the center channel is no longer harsh/bright sounding but the sound does because very slightly muffled. It does not bother me and is hardly noticeable but I am wondering if anyone knows why this would be the case.

There is no technical reason for your perceptions.
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Is the muffled sound at the 4 ohm setting a result of clipping?

The impedance switch makes only a small difference in your AVRs power output before clipping. Are you running a dance party so that you would be running your system that loud?
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If it is safe to run my receiver with the impedance switch set to 4 ohms I would prefer to do that because it gets rid of the harshness in the center channel.

The position of that switch shouldn't make that much difference one way or the other. It makes an approximate 15% change in the voltage available to the output stages, which can be meaningful on the test bench with pure sine waves and resistive loads but is unlikely to make much difference with music and speaker loads.

If I did some technical tests and found that you were autosuggesting these perceptions to yourself I wouldn't be the least bit surprised.

For openers, spend $10 or so on the non-contact thermometer and get some objective data about the actual operating temperature of your AVR.

If it is not too hot to touch without severe discomfort than it is staying below 120 degrees, which should be fine.

If it is getting too hot, the most likely cause is likely poor ventilation, so if needed, fix that!
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post #6 of 8
1/25/13 at 6:54am
Quote:
Originally Posted by JHAz View Post

AFAIK, what the 4 ohm switch is supposed to do is limit available voltage, and available power, to avoid overheating the receiver when running the more challenging lower impedance speakers.

Close, except that the switch generally only makes a significant thermal difference on the test bench with test tones and resistive loads.

What it does is select some taps on the power transformer that changes the power supply voltage for the output stage by maybe 10-15%.
Quote:
It's not like a transformer tap for a tube amp - there is no need for (such a thing) with solid state amplification devices. It should not have an effect on sound at all unless you push hard enough to cause clipping with the 4 ohm setting that would not occur at the 8 ohm setting..

Agreed on all counts.
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post #7 of 8
1/25/13 at 10:11am
Thread Starter 
I am not an audio expert but since the impedance selector switch is for the front left and right speakers only, does the sound from the center channel become less harsh with the switch at the 4 ohm setting because more power is being sent to the front left and right speakers and less power is sent to the center channel because of this.
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post #8 of 8
1/25/13 at 11:07am
Quote:
Originally Posted by dave2441 View Post

I am not an audio expert but since the impedance selector switch is for the front left and right speakers only, does the sound from the center channel become less harsh with the switch at the 4 ohm setting because more power is being sent to the front left and right speakers and less power is sent to the center channel because of this.
Why not try it and see if the harshness goes away?
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