ohms questions

[Automission]

When buying an audio receiver is it better for the receiver to give out more ohms that the speakers? Say you have a 5.1 setup, all 4-6 ohms. Would it better to have a receiver give out 4-6 ohms, or should it be higher, like 6-8 ohms? Is there a limit to how many ohms you can put into the speakers?

Also what does the wattage mean, like if the speakers are 150w, should the receiver give the same amount out, more or less?

[Steve]

You want the Ohm rating of the speakers to match the Ohm rating of the receiver and vice versa. If you have a receiver rated for 6-16 Ohms (seems to be popular), then you want the impedance rating of your speakers to fall within that range. It's not a good idea to try to play 4 Ohm speakers on a receiver rated for 6-16 Ohms. You risk burning up the receiver.

When it comes to wattage ratings it's a little bit different. When a speaker is rated for 150 watts, you have to look at whether that's a peak rating or a continual rating (expressed as RMS). If it's a peak rating then the speaker can handle 150 watts, but only for a few seconds at a time. If it's rated at 150 watts RMS then it can handle 150 watts continuously. Your better speaker brands will show the wattage rating for their speakers as RMS rather than peak.

It's Ok if the wattage ratings of your speakers and receiver don't match. If your speakers are rated for 100 watts RMS, but your receiver is rated for 150 watts per channel (and can actually push that much-more on that later), then you're still Ok as long as you're somewhat careful. The wattage rating of your receiver means that's how much power the receiver can provide, not necessarily how much power it provides continually. In a nutshell, the power supplied by your receiver is directly related to how loud you have the volume set. For comfortable listening levels you may only be pushing somewhere between 10-20 watts per channel. This is not going to harm your speaker. But if you put in a good action movie and really crank the volume then you'll be pushing quite a bit more power. This is where having plenty of power comes in. Every time you double the power sent to your speakers you're only adding 3 dB of volume. So if you increase from 20 watts to 40 watts going to your speaker you're only increasing the volume by 3 dB. To increase by another 3 dB means you must double the power again to 80 watts and the cycle continues.

It's often Ok to push more power to your speakers than what they're rated for, within reason of course. The key is you want clean power. It's a good idea for your receiver to have more power in reserve than you'll actually use. This is known as headroom. By not driving it to its limit you're not putting a strain on it and you don't run as much risk of clipping or introducing distortion, and clipping and distortion will wreak havoc on your speakers. If your speakers are rated for 100 watts and your receiver is rated for 100 watts per channel and you have it turned up as loud as it can go then you're likely getting clipping and/or distortion (because you're running it to its limit) and there's a very good chance of damaging your speakers, even though the speakers and receiver are both rated for 100 watts. On the other hand if your speakers are rated for 100 watts and your receiver is rated for 150 watts per channel and you have the volume turned up just as loud and you're pulling 100 watts per channel, you won't do any damage because the power is clean and there's no distortion or clipping. This is where you may even be able to put 110 or 120 watts to your speakers without damage. Again the key is clean power.

Lastly be aware that manufacturers often overstate the wattage ratings of their receivers. It's common for a receiver's specs to say it has 90-100 watts per channel with all channels driven, but when these receivers are actually tested they usually measure somewhere in the 40-60 watt range. Some even lower. Certain lines like HK, Marantz, and Pioneer Elite tend to be quite accurate while others like Onkyo and Pioneer (non-Elite) are often considerably inaccurate. This doesn't mean they're bad units. It just means they don't have the power they say they do.

[Fors*]

What a really nice read....good post Fireman!

[Automission]

my sub woofer is 20k ohms, isn't that really high, or is that a different measurement than the normal 6 ohms?

[Steve]

Originally Posted by Fors*

What a really nice read....good post Fireman!

Thanks man.

Originally Posted by Automission

my sub woofer is 20k ohms, isn't that really high, or is that a different measurement than the normal 6 ohms?

I don't think that's right. What is the exact model of the subwoofer?

[jomari]

Fireman, an absolutely amazing posting regarding resistance and speaker capacity.

There not much to add on to this, you can also learn more about it from this sticky,

https://forum.blu-ray.com/speakers/7...ng-factor.html

[Automission]

one of these.
Specification - BRW10 | Monitor Audio

So if my speakers are all 6 ohms, I want a receiver starting at 6 ohms and up to 16 ohms? I'm looking at one with 8 ohms, would that not be powerful enough? You say trying to run 4ohms speaker on a receiver rated for 6-18 ohms is bad, but is running 6ohms speaker on a receiver rated for 4-18 ohms also bad, or will that not matter?

basically, does the receivers lowest ohm rating have to match the speakers, or can you go lower than the speakers ohms?

[Steve]

Originally Posted by jomari

Fireman, an absolutely amazing posting regarding resistance and speaker capacity.

There not much to add on to this, you can also learn more about it from this sticky,

https://forum.blu-ray.com/speakers/7...ng-factor.html

Thanks.

Originally Posted by Automission

one of these.
Specification - BRW10 | Monitor Audio

So if my speakers are all 6 ohms, I want a receiver starting at 6 ohms and up to 16 ohms? I'm looking at one with 8 ohms, would that not be powerful enough? You say trying to run 4ohms speaker on a receiver rated for 6-18 ohms is bad, but is running 6ohms speaker on a receiver rated for 4-18 ohms also bad, or will that not matter?

basically, does the receivers lowest ohm rating have to match the speakers, or can you go lower than the speakers ohms?

I don't know about the impedance rating of that sub. It's odd the way it's listed. One thing about powered subwoofers though is that since they have their own amps built in they're really a non-issue in regard to matching your speaker and receiver impedance-wise.

You don't have to use a receiver that is rated all the way up to 16 Ohms. I was just using that as an example because it's somewhat common to find that rating on current receivers. As long as the impedance rating of your speakers falls within the range specified on your receiver you'll be fine. It seems 8 Ohms is the most common rating for speakers. However there are quite a few out there that are rated at 6 or 4 Ohms as well. If you have 4 Ohm speakers your best bet for powering them is a separate amp rather than an integrated AV receiver. Even when you see a receiver rated at 8 Ohms, you will often find that it's stated somewhere that it can operate 6 Ohm speakers as well if you look a little deeper. When in doubt contact the manufacturer of the receiver to find out if your particular speakers will be compatible with it.

[jomari]

The only time you'd be concerned is if your AVR cannot handle speaker resistance lower than its rated at. in most cases, you'd be weary of an AVR that cannot handle anything under 4ohms. some AVRs have an alternative mode to switch from regular 8ohms to 6ohms at times.

Jason R gave me a link a while back towards connecting speakers rated differently from the AVR and the chances of it causing problems... i personall do not advocate this method, but it does show its feasible. again a disclaimer, try at your own risk damaging your AVR and/or speakers...

here it is...Connecting 4-ohm Speakers to an 8-ohm Receiver — Reviews and News from Audioholics

post of conversation found here...https://forum.blu-ray.com/home-theat...ml#post2777979

some subs list their resistance in case people want to modify or update their drivers afterwards. personally, i dont believe the rating listed. wierd.

[Beerserker]

That 20K ohms in the subwoofer listing is the input impedance for the on-board amplifier, and not really relevant to you or me. You could hook it up to any receiver with a sub-out.

For the OP, I just like to add that receivers or amps with low impedance ratings are more desirable, it means they are stable at high current draw. If you get a receiver that is rated at 8 ohms it may have trouble running speakers that are 4 ohm speakers (the 4 ohm speakers may draw too much current). So, say you have the choice of two receivers, both tested at 100 watts per channel at 8 ohms, and both have all the other features you want. One is rated as stable at 8 ohms and the other at 4 ohms. The best choice is the 4 ohm receiver, regardless of what speakers you want to run, be they 4, 6, 8 or 16 ohm.

[Automission]

so an impedance as low as 4 ohms is okay for speakers rated at 6ohms? I figured an impedance as low as that would overpower the speakers and damage them? Would the 8 ohms then under power them, or be stable? I'm looking at a Yamaha RX-V765 at the moment, specs are here.
RX-V765: Specs - AV Receivers/Amplifiers - Products - Yamaha UK and Ireland

[richteer]

Originally Posted by Automission

so an impedance as low as 4 ohms is okay for speakers rated at 6ohms? I figured an impedance as low as that would overpower the speakers and damage them? Would the 8 ohms then under power them, or be stable? I'm looking at a Yamaha RX-V765 at the moment, specs are here.
RX-V765: Specs - AV Receivers/Amplifiers - Products - Yamaha UK and Ireland

The impedance spec of the amp is merely an indication that it is designed to be able to power 4 Ohm speakers (which require more current than those of higher impedance). It's not an indication of power per se.

So, what they're saying is that the amp will be OK driving any speaker with an impedance of 4 or more Ohms (i.e., most of them).

[Beerserker]

Originally Posted by Automission

so an impedance as low as 4 ohms is okay for speakers rated at 6ohms? I figured an impedance as low as that would overpower the speakers and damage them? Would the 8 ohms then under power them, or be stable? I'm looking at a Yamaha RX-V765 at the moment, specs are here.
RX-V765: Specs - AV Receivers/Amplifiers - Products - Yamaha UK and Ireland

I think you have it a bit muddled with all these specifications. For a detailed explanation read the sticky that Jomari linked to.

Ohms are a measuring unit for resistance. The higher the Ohm rating the more resistance there is. Speaker impedance is a little different, but I wont get into that here, kind of the same idea though. Speakers with low ohm ratings will draw more current. You want to be sure your amp or receiver can supply the current they will draw. Quick and dirty rule is make sure your receiver Ohm rating is equal to or lower then the rating for the speakers you want to run.

What speakers are you going to run? I'll see if that receiver will be ok with them.

[Automission]

Originally Posted by Beerserker

I think you have it a bit muddled with all these specifications. For a detailed explanation read the sticky that Jomari linked to.

Ohms are a measuring unit for resistance. The higher the Ohm rating the more resistance there is. Speaker impedance is a little different, but I wont get into that here, kind of the same idea though. Speakers with low ohm ratings will draw more current. You want to be sure your amp or receiver can supply the current they will draw. Quick and dirty rule is make sure your receiver Ohm rating is equal to or lower then the rating for the speakers you want to run.

What speakers are you going to run? I'll see if that receiver will be ok with them.

These are the speakers I own .
Specification - BR2 | Monitor Audio
Specification - BR6 | Monitor Audio
Specification - BRLCR | Monitor Audio
Specification - BRW10 | Monitor Audio

Given what you say is true, I might continue looking elsewhere. The Yamaha may provide 6ohms, but if 4 is going to be better, I'l have to see what else there is.

I'm open to any suggestions on what will go well with those speakers.

[Beerserker]

I don't think the yamaha will have a problem with those speakers, though I can't find a bench test on it. Don't let my comments deter you from getting this receiver if you want it. Yamaha is a good brand, and those monitors should run on most receivers.
The stability (ohm rating) of a receiver is only one of the factors to look at, I don't want you to bend over backwards to find a receiver that is rated super low. It's just an indication of the build quality of the power stage in the receiver. Sometimes it's hard to find the actual stability rating of a unit, there is so much marketing BS.

[Automission]

Okay good to know, thanks. I'l keep researching for a bit, as I'm told the Yamaha doesn't support setting an optical audio input to a hdmi video input, I'm currently unsure if that was changed. Thanks for the help.

[Steve]

OP also keep in mind that to get a receiver that is actually rated down to 4 Ohms will probably be quite expensive. If your speakers are rated at 6 Ohms, and your receiver is rated for 6 Ohms, you're good to go. You're not going to see any improvement with a receiver rated for 4 Ohms just because it's rated for 4 Ohms. Other factors may come into play that might positively influence the sound, but the Ohm rating won't be an issue.

What is your budget for a receiver by the way?

[Automission]

Really I don't want to spend more than £300, the yamaha is just over that, which is why I'm planning to do some more research into another receiver. If it comes to it, I'l settle for the yamaha, and just try to rustle up some more cash.

[Steve]

Originally Posted by Automission

Really I don't want to spend more than £300, the yamaha is just over that, which is why I'm planning to do some more research into another receiver. If it comes to it, I'l settle for the yamaha, and just try to rustle up some more cash.

The Yamaha 765 is a nice receiver, and I didn't even catch that you were in England. I don't know if it's an oddity or the norm, but Onkyo receivers like the 605 that I used to have were only rated down to 6 Ohms for the US version, but the UK version had a 4 Ohm mode the receiver could be set to.

Anyway the Yamaha you're looking at has a full set of pre-outs and that means that down the road you can add a separate amp if you want to and having that option is a good thing.

[Automission]

I think mine probably did, but the issue I had was the Onkyo had the handshake, hdmi board fault. Regardless of it being fixed, I've been told it occurs again. I've been put off buying another onkyo of a different model number, given the poor quality of the 606.