Speaker impedance switch...........what's the point?

[caniac]

Just got a new receiver, a Pioneer VSX-D814. The manual says that for speakers under 8 ohms (mine are 6 ohms), you need to switch the impedance.

I'm just wondering, what is the point of doing this? I've been running these speakers for probably 10 years on several different receivers and I've never had even a hint of any problems.

[PAT.P]

Maybe thats because most receiver rated 8 ohm impedance could also play 6 ohm with no problem .If they were 4 ohm you would need more power. My towers are 8ohm but the nominal is 6ohm.I had only a Sony .Now i have a Yamaha and but switch at 4 ohm and its like day and night .The receiver as the power and Im running two towers .My sony would go on protect all the time.Pat.P

[kexodusc]

. My towers are 8ohm but the nominal is 6ohm.I had only a Sony

Hi Pat.P,

I'm not sure I follow this statement...if your speakers are 6 ohms "nominal", they're said to be a 6 ohm speaker, that is, they behave similarly to a 6 ohm resistor. You shouldn't have a 6 ohm nominal speaker referred to as an 8 ohm speaker (but I've seen stranger things) They undoubtedly have peaks well above 12 ohms and probably below 6 ohms as well. The low number is usually the one you worry about (high impedance should be dealt with by the crossover, or we can assume it's insignificant).

The switches on receivers often only adjust the internal protection devices, so your receiver doesn't go into protection mode to early, or worse, too late. Many amps/receivers don't even bother with them.

[PAT.P]

Kexodusc I was told they would have no problem playing them on a 8 ohm receiver like the Sony I was using.Still not benefiting at this time all potential of these speaker (bi-wire and by-amp).Pat.P

[kexodusc]

That makes sense...and that's a bit different than being an 8 ohm nominal speaker. 6 ohm nominal speakers suggest that the average impedance accross all frequencies for your speaker is closer to 6 than to 8 ohms. This is fine...No speaker has a constant impedance, it varies with frequency. Even 8 ohm speakers will tend to dip belo 6 ohms, and often below 4 ohms over certain bands.

If the dips aren't too far below 6 ohms, than a 6 ohm nominal speaker "should" often work fine on 8 ohm receivers. Some 8 ohm speakers with lower impedance dips would actually be harder on the amp than the 6 ohm speaker with relatively minimal dips.

There's a lot of discretion that goes into rating the impedance of a speaker...I suspect a lot of manufacturers choose to rate them 8 ohms so not to scare potential customers off.

Electrically, theoretically, bi-wiring shouldn't yield any advantage despite what you read, and could in fact diminish performance...in practice a lot of people claim good results..

[Pat D]

Just got a new receiver, a Pioneer VSX-D814. The manual says that for speakers under 8 ohms (mine are 6 ohms), you need to switch the impedance.

I'm just wondering, what is the point of doing this? I've been running these speakers for probably 10 years on several different receivers and I've never had even a hint of any problems.
Here's a link to an article on receivers and speaker impedance. There is a 'NOTE" on impedance selectors, too.

http://www.audioholics.com/FAQs/4-ohmspeakersreceiver.php

[sam9]

My opinion:

The 4-ohm switch is a CYA to reduce warranty problems. What it probably means is that the transformer can't handle a 4 ohm speaker under cionditions of heavy use. It will overheat and suffer damage. The swith drops the voltage to where the transformer is safe.

Example: Suppose the amplifier section has the following power ratings with the switch in the 8 ohm position 100W @ 8 ohms and 150W @ 4 ohms. In the 4 ohm postion is msy be 65W @ 8 ohms and 100W @ 4 ohms.

Depending on your situation maybe this is ok or maybe not. For instance if you were using small satellites with a powered sub, a mere 50W @ 8 ohms is often more than adequate for any same listening level.

[kexodusc]

I'm normally a big fan of Audioholics, but if I see an impedance selector, and the manual advises using it, that tells me I should use it. Perhaps not as much with beefier flagship receivers that have 400-500 watt power supply units, but for the smaller multi-channel receivers that have 230-300 watt units it makes more sense.

Most amps I've owned didn't have a selector switch, and usually produced double the rated power into 4 ohms that they would at 8 ohms...if not, it was really close.

If a receiver has one of these switches, that's telling me the manufacturer isn't 100% confident of it's ablility to handle 4 ohm loads, whether it can't handle the voltage, current, or heat.



Depending on your situation maybe this is ok or maybe not. For instance if you were using small satellites with a powered sub, a mere 50W @ 8 ohms is often more than adequate for any same listening level.

Taken a step further, I have large towers that are 91 dB sensitve... 2 watts plays pretty darn loud in my large size room, even the dynamic peaks are only measuring 16 - 24 watts. (I love VU meters).

We're seeing more and more speakers delivering higher sensitivities. In mid-size living rooms, a few watts/channel is all it would take to reproduce theater volumes. I can see digital amps gaining a lot of popularity on the home theater side of things.

[Woochifer]

My opinion:

The 4-ohm switch is a CYA to reduce warranty problems. What it probably means is that the transformer can't handle a 4 ohm speaker under cionditions of heavy use. It will overheat and suffer damage. The swith drops the voltage to where the transformer is safe.

Another more recent reason is that I believe that UL approval now requires an impedance switch. If you go into the setup menus of newer receivers, you'll find that the impedance selector is now switched that way rather than through a manual switch on the back of the unit. Just because you don't see one doesn't mean that it's not there.

[sam9]

Makes sense if driving too low a load causes a fire hazard due to heat in the transformer. There maybe other acceptable safegards such as a thermal link (fuse) embeded in the winding.

Other obvious solutions are "brute force" just use a large enough transformer for any load, VI limiting that takes the transformer into acount as well as the output devices, or a SMPS. All of these except the first add to either the cost or the weight or both. One more but rare possability: I was told by an amp designer (French I think) of using a transformer designed to be mounted with it's own heatsink and fan that could kick in if needed-- this let them cut the size and mass of the transforner by 2/3.

[hermanv]

This is new, a Japanese receiver with a transformer? Does the Pioneer VSX-D81 have an output transformer or even an input transformer for that matter? Is this not a solid state unit?

Most "modern" transistorized receivers have neither an ouput transformer or the conventional input transformer (most new products use a high speed switching power supply and a related high frequency ironless transformer because it is cheaper). If well done, there is nothing wrong with this.

So I go with keodusc that it changes the internal feedback loop for protection or even for correct compensation. It might interact with the main power supply to limit peak current.

Ouput transformers are very expensive and even more so for a multi channel surround receiver, they are basically necessary only for tubes (except the OTL designs which have a different way of consuming your spare money).

Anyone seen a schematic, looked inside? :rolleyes:

[Geoffcin]

Here's a link to an article on receivers and speaker impedance. There is a 'NOTE" on impedance selectors, too.

http://www.audioholics.com/FAQs/4-ohmspeakersreceiver.php

And I've always used it in the 4 ohm setting with good results. The 4 ohm setting looks like it engages current protection circuit.

Just for giggles, as I now have it out of my daughters setup, I tested it both ways and I cannot hear a difference in quality. I think the Audioholic guys jumped to a conclusion without first actually TESTING to see if what they were saying was correct.