rotel rsx1056 w/4 ohm speakers;misconception

[rick c]

I always thought that the rsx1056 should not be used with 4ohm speakers.Atleast that's what rotel told me a while back when i was inquiring about dynaudio speakers,so i ended up with B&W 603s3's/lcr600(really liked them anyway).Well i have upgraded my speakers to a System Audio setup(sa1750/sa720av/sa505's)these speakers are 4-8ohm and 90db and fantastic by the way(apparently not that well know in U.S.A).Thinking that the rsx1056 was going to need an amp with these speakers i began inquiring into the class d amps specifically the red dragon amp1.In the mean time i just used the rsx1056 w/o an amp until i would decide.Beleive me the rsx1056 does a fine job with these speakers so much so that i think an amp would probably be a waste of money.So if anyone who has an rsx1056 and was afraid to use 4ohm speakers do not be afraid to use them.I really dont know why Rotel advises against it.Is it that my speakers are 90db the reason for the rsx1056 performing so well?You tell me.

[Destruction]

I think the reason that 4 Ohm speakers are not recommended is that the output devices fitted to the receiver's power amp section cannot provide the current at high levels into loads with nominal impedances of less than 8 Ohms. If the output device (transistor) exceeds the rated current it will practically blow-up, leaving your receiver dead.

This is why 4 Ohm speakers are not advised, so you should be afraid to use them. It's not that they wont work but the fact that you will stress the amplifier at high levels, ultimately leading to the demise of your receiver and I'm pretty sure that this will not be covered under warranty.

My advice therefore is to be careful.

All the best.

[shadow 8]

Actually they are not advised because the amp runs warmer with 4 ohm speakers. I think UL certification turns on how warm an amp runs. I run a Martin Logan setup with my 1056 and it drives them fine.

[rick c]

I think the reason that 4 Ohm speakers are not recommended is that the output devices fitted to the receiver's power amp section cannot provide the current at high levels into loads with nominal impedances of less than 8 Ohms. If the output device (transistor) exceeds the rated current it will practically blow-up, leaving your receiver dead.

This is why 4 Ohm speakers are not advised, so you should be afraid to use them. It's not that they wont work but the fact that you will stress the amplifier at high levels, ultimately leading to the demise of your receiver and I'm pretty sure that this will not be covered under warranty.

My advice therefore is to be careful.

All the best.

Thanks.But FWIW i've been running with these for over a week now over 8hrs a day.I checked the warmth of the receiver several times and it doesnt seem any warmer than normal.Are you suggestioning that i relook about getting an amp which i was originallyy doing to avoid any possible problems.I was originally looking at the red dragon amp1 but rethank it since i felt the rsx1056 was doing fine on it's own.

[Destruction]

A separate amp will probably be best in the long run, even if the receiver does not run exceedingly hot. It is usually the instantaneous current drawn from the device that will damage it. This is most likely to happen at low frequencies and at high level, especially if you set your speakers to large.

You could look at the Rotel class D amps as these are pretty stable with difficult loads?

8)

[gianni]

I think the reason that 4 Ohm speakers are not recommended is that the output devices fitted to the receiver's power amp section cannot provide the current at high levels into loads with nominal impedances of less than 8 Ohms. If the output device (transistor) exceeds the rated current it will practically blow-up, leaving your receiver dead.

This is why 4 Ohm speakers are not advised, so you should be afraid to use them. It's not that they wont work but the fact that you will stress the amplifier at high levels, ultimately leading to the demise of your receiver and I'm pretty sure that this will not be covered under warranty.

My advice therefore is to be careful.

All the best.

Not true at all. The previous model, the RSX-1055 has identical amp sections and Rotel told me 4 ohm speakers are fine - this is also listed in a Rotel FAQ sheet. I beleive the reason for the 4 ohm warning is purely a legal/UL rating thing. In the real world, unless your speakers are unusually inefficient and you have a large room, 4 ohms is a non issue. I have used 4 ohm speakers for the last 4 years with my RSX-1055. Ignore the fallacies.

To see for yourself:
Rotel FAQ

[shadow 8]

Again, you will have no problem driving 4 ohm speakers. If you want to drive inefficient speakers like Dynaudio to near reference level you would likely need more power, but the B&W speakers you have are a breeze for the 1056.

[rick c]

Again, you will have no problem driving 4 ohm speakers. If you want to drive inefficient speakers like Dynaudio to near reference level you would likely need more power, but the B&W speakers you have are a breeze for the 1056.

The B&W's i used to have were 8ohm and no problem there.Now i have the System Audio's that i described in the OP.As far as i can tell i'm having no problems driving these speakers with the rsx1056.I thought i was going to but that is not the case as far as i can tell.As a side note the B&W's that i had and liked were out of their league in comparison to the System Audio's,even though the SA's are 4ohm.IMHO I really cant explain how much better these speakers are in every sense.

[Destruction]

Not true at all. The previous model, the RSX-1055 has identical amp sections and Rotel told me 4 ohm speakers are fine - this is also listed in a Rotel FAQ sheet. I beleive the reason for the 4 ohm warning is purely a legal/UL rating thing. In the real world, unless your speakers are unusually inefficient and you have a large room, 4 ohms is a non issue. I have used 4 ohm speakers for the last 4 years with my RSX-1055. Ignore the fallacies.

To see for yourself:

I'm sorry to dissapoint you but the amplifier in the RSX-1056 is very different in terms of the output devices and driver transistors.

Whilst I agree with you that 4 Ohms will work provided the level is not too high, it still remains that there is a possibility of damage that would not be covered by the manufacturers warranty - at least in the EU anyway.

The minimum 8 Ohms rating is not a legal issue believe me, however I do know that US and EU standards are different so maybe this explains it.

Obviously this debate could go on a bit so to keep things civil we may have to agree to disagree on this occasion. 8)

[rick c]

FWIW, i contacted rotel tech support today in regards to a small problem i'm having with the rsx1056.They advise me it's probably a software glitch and that a new one(software) is coming out in a few days that should take care of the problem.While i was talking to him i went ahead and asked in regards to 4ohm speakers with the rsx1056.He said as long as there is ventilation there wont be a problem.

[shadow 8]

As I noted earlier, I am driving five Martin Logan 4 ohm speakers with no problem at all.