Receiver and 4 ohm speakers? - Page 2

This is very true.My experience with Denon AVC-A1XV and A1HD with MK 150THX,it was fine for many months and after that these receivers always shut down in protection mode frequently even low listening level.

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that would be EXTRAORDINARILY unusual with the units you note...

EXTRAORDINARILY...

again, cause analysis please...

fwiw, i agree pretty much with michael, but the most recent "anecdotal" reports are, umm, "interesting", to say the least...

I sent them for repairing and service center said they were ok.Now I use MK system(4 ohm)with Denon avr 100 and there is no protection mode issue for a year now.

+1

While as I said above I suspect my listening levels might never challenge an amp that's not really rated for 4 ohm loads (especillay with bass management), in fact when I bought my receiver I had Magnepans and I made sure the receiver I purchased was both rated for 4 ohm loads and had decent third party testing results at 4 ohms.

The ohm rating for a speaker is completely meaningless.

Impedance varies not just with frequency, but with the exact waveform passed into the speaker. It's impossible to give it a value like you could for say DC resistance.

There's a reason the impedance value is nominal and it's always in very rounded units. The reason is the number is basically guessed or just plain made up by the manufacturer. Some manufacturers say their speaker is 8 ohms simply because of people scared of 4 ohm speakers. Others put the impedance at 4 ohms so they can protect themselves in case the speakers fail. They can just say the receiver or amp wasn't rated for 4 ohms, so no warranty coverage. OR they can try to get purchasers to get a better qaulity amp or receiver.

As far as power goes...
It's true that, all things being equal, a speakers power output under 4 ohms of impedance will require more current than the same under 8 ohms, but it's also true that the receiver will have less difficulty delivering said current. By the way, it's not twice the current. Power consumption is a function of the current squared, so it will actually require about 1.4x as much current (p=r*i^2 or p=iv, where v=ir,r=resistance or impedance).

Saying beware of 4 ohm speakers is analogous to someone saying you need to be careful driving an SUV too fast. The extra weight puts a lot of strain on the engine. Without taking into account the SUV having a beefier engine.

Sensitivity or efficiency of the speakers will have more impact on whether or not the receiver overheats at a given volume level than the nominal impedance. So if you have an inefficent 8 ohm speaker, you're more likely to blow an amp than if you have an efficient 4 ohm speaker.

I would guess that if someone set up a test environment with a given receiver and hooked up a set of 4 ohm and a set of identical 8 ohm speakers (impedance being the only difference). Most couldn't tell which was which without measuring the current directly.

Historically, speakers had impedances of 16 and 8 ohms nominal. The higher the speaker impedance, the more windings in the voice coil and consequently the accuracy of the cone movement in the magnetic field was better. Car radios initially used vibrators to create a supply voltage higher than 6 or 12 volts for the vacuum tubes and output transformers were used so the speaker impedance was high. With semiconductor radios, the output transformers were gone and speaker impedances were dropped to 4 ohms to get more power on a given supply voltage.
Getting back to the topic at hand, as most have mentioned, speaker impedance with respect to frequency is not a constant. It peaks at the resonant frequency of the speaker in its cabinet. This is why ported enclosures typically tune the port below the free space resonance of the speaker itself to give a more uniform response over a wider frequency range. For those looking for a good read on speaker impedance, I would recommend the Wiki file.
http://en.wikipedia.org/wiki/Electri...c_loudspeakers

Incorrect..
Nominal speaker impedance is an important specification..
But like other electronic components it is just 1 spec of many that should be reviewed when deciding loudspeaker brand/model..
The actual nominal speaker impedance is not guesswork but rather a range..
For example, in a 3-way loudspeaker each transducer may have different impedance and when designed into a total system its impedance is determined by the total system design. Frequently conjugate circuits, are used to balance the total impedance load and keep it above certain minimum impedances..



As mentioned previously, the challenge today is that the amplifier sections & power supplies within the price point AVRs (SRP <$999) have been cut back very significantly to save $.. And since 87% of the home theater market segment are using subwoofer/satellite loudspeaker systems, most users won't notice the cutback....
However, as the listener becomes more experienced and informed, very frequently they will upgrade their loudspeaker system to a higher performance, full-range system.. As the bandwidth extremes are pushed especially the low end, then the shortcomings of reduced amplifier sections & power supplies for the price point AVRs becomes more apparent & audible...

Just my $0.02..

My receiver started doing weird things, like switching inputs on its own every once in a while, in few months after I got new 4ohm speakers. This got progressively worse and it would switch instantly making it unusable. Sometimes it would just turn off. I stopped using this receiver for few months and after that reconnected it using 8 ohm speakers and it worked perfectly after that. There was one change though from a cabinet I moved my gear to open shelf that could be a factor, there was decent clearance on the top and I always kept cabinet open. Had Similar experience with another receiver as well, and this receiver always ran very cool, so I am leaning towards not considering cabinet as a big factor.

Don't get it wrong.It's nothing to do with 4 Ohm speakers.Newer AVRs tend to have 4 Ohm speaker adjustment/switching like Denon 4311 or Onkyo xxx9 serie.
Another issue to consider is always the ventilation.

Receivers I have seen have a 6 ohm switch, not a 4 ohm switch. And near as I can tell, all it does is to reduce the power supply voltage to the amps. In tests, this has been shown to limit power.

If your receiver needs the lower impedance switch to avoid going into protection, I could argue it can't handle 4 ohm speakers.

Onkyo has had a switch for 4 ohm and 6 ohm for a number of years.
This is what the manual says:

Decent amps don't need an impedance switch. Its one of the reasons I have separates. Even Emotiva amps, some of the least expensive, do not need a switch for speaker impedance. If low impedance was associated with "poor control" of a driver than it would have higher distortion in tests, in reality some of the lowest distortion drivers are 4 ohms. The 8 and 16 ohm standards were for tubes which, unlike solid state, don't handle low impedance's well.

I certainly feel my Onkyo is a decent amp. Actually feel it's one of the best values to be had.

perhaps I spoke too strongly. I have an Onkyo pre-pro but separate amps. I really wouldn't buy a receiver with an impedance selector though, its a clear indication of inadequate amplification. I used to use a Yamaha DSP-A1 with an impedance switch and the thing clipped very easily.
If you have 4 ohm speakers I would seriously consider a separate amp for at least the L/C/R.

I would agree if using 4 ohm speakers amplification would be an issue. My 809 pushes plenty of power to my RF 82's.

Very true. I built my own speakers and the Emotiva amps drive them to very loud levels without clipping even though the drivers dip below 4 ohms. The typical receiver isn't designed for such use because of economics.

Ouch... there goes such receivers as Onkyo TX-5009, Integra DTR 80.3, Denon AVR 4311 and the amplifier Integra DTA-70.1 out of the door...
Interestingly, the Denon has a 4, 6 and 8 ohm setting.

I generalized and I apologize. I didn't know the Denon used such a switch and I have heard that Denon has decent 4 ohm output. I assumed that the impedance matching switch simply reduced current.
.

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it does...

many have a "switch"... they are all essentially useless though... if the user doesn't get acceptable results with it set to 8, it won't help to set it to 6 or 4...

edit: i use a 4311 with 4ohm speakers... does the job for me...

That's what I thought.
It's good to hear that your 4311 works well with four ohm speakers.

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yea, i made sure that it would before i sold the bryston i was using with the av7005...

i think that those switches are merely there to cya... as noted, they can't do anything to actually help (can't make the power supply magically more robust simply by flipping a switch)...

it the user is putting a unit into protection at an 8 ohm setting, they'll put in to protection at a lower setting as well...

What a change, from Bryston and 7005 to a Denon receiver!

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lol...

and i don't regret it, either... not to get too far ot, but the usage of xt32, in my room with my speakers and subs, made a significant objective and subjective change for the good...

Well the topic is receiver's with 4 ohm speakers, I think your experience with the Denon is on topic. I have a pre-pro with XT32 too. Receiver's that handle 4 ohm speakers are rare probably because of budget constraints limiting the quality of the power supply, especially the expensive transformer.

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yup, i'd agree with that... the power supply is what "costs"...

here's a link to a post by mcode from awhile ago on the cost breakdown of a 600 dollar avr... i would imagine it doesn't scale directly, but it gives an idea...

click me

i think with 4ohm speakers, it also comes down to usage... if the user doesn't abuse the volume control, even a relatively small power supply will still be ok... however, if the user is like me, it won't...

My ancient Yamaha DSP-A1 clipped easily and my DIY speakers were 4 ohms and clipped whether the impedance switch was set to 8 ohms or 4 (or was it 6?). Now I use separates which are required for my DIY active fronts. I did consider a receiver but the necessity of having several external amps and "wasting" the receivers amps for all but sides was something I couldn't get past. The Denon as a pre-amp would have probably been a good alternative. There are those who claim 4 ohm speakers are a poor design but I think this is only true if one's receiver's amps aren't up to 4 ohms. There are many great 4 ohm speaker's available.

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yea, i've seen your descriptions of your setup, that is very nice...

i (obviously ) couldn't agree more with your last statement...

I'm sorry, I repeat myself.

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you and me both...