Ohms - do speakers have to match receiver?

[Gretchen_TX]

I just bought an Onkyo TX-8511 receiver (8 ohms). My speakers are Yamaha NS-555s (6 ohms) Will that work? Also, should I bi-wire the speakers? Thanks in advance for your help.

[This Guy]

it should be alright, it'll just be harder for the receiver. Don't bother bi-wiring.

[Florian]

I just bought an Onkyo TX-8511 receiver (8 ohms). My speakers are Yamaha NS-555s (6 ohms) Will that work? Also, should I bi-wire the speakers? Thanks in advance for your help.
The small Onkyo should be fine with the 6ohm load. The resistance is very very important, because if the resistance is higher on the speaker (lower ohm) than the AMP can take you risk of not only burning up your AMP you also risk of damaging your speakers because the AMP is clipping and failing.

But the Onkyo should be fine with the 6ohm load, and biwiring helps a little bit in my opinion.

-Flo

[Jace]

umm. higher resistance would be "higher ohms". just thought id point that out. ok here are the basics of whats happeneing between the speaker resistance (load resistance) and the amps rated overal resistance (source resistance).

when you have a perfect match, half the voltage is dropped across each resistance. this will give you the most efficiency and therefore the most power to the load.

when your resistance is higher at the load, you will get more voltage dropped across the load, but less overall current, resulting in less power to the speaker.

when you have a lower resistance at the load, you will get less voltage dropped across the load, but at the same time, you will have more current, but the increase in current is not going to be enough to give you any more power than if you have an equally higher resistance at the load. what it can do though is burn out your amp because of the increase in current and the increase in power disipated by the source resistance.

so in other words, you will lose some power, but it is better to run a higher resistance speaker than your amp/receiver is rated for that a lower one. still, in your case, it should be ok.

-Jace

[Florian]

higher resistance would be "higher ohms".
I dont agree on that. My Apogee's are 1ohm and therefore if not the hardest to drive speaker in the world. If what you say is correct then, i could use a Sony Receiver for it. The higher the "ohm" the easier it is to drive, thats why horns sometimes have 16ohm.

-Flo

[Kaboom]

yeah, sure with higher ohm easier to drive, but that's not because the resistance is lower, its just that its easier for the amp to drive higher resistances for the reasons Jace pointed out. Lower resistance at the speaker = more CURRENT has to be provided to the speaker. pumping out more current than the amp was designed for will eventually fry it.
Resistance is a measure of how a conductor opposes the flow of electrons across it, not of how hard it is to drive a speaker

[Jace]

umm florian. i think you got the right idea of how things work, you just dont know why it works like that. as you say, the higher the "ohm" (the correct term by the way is impedence, not "ohm". ohm is just the unit that impedence is measured in), the easier it is to drive. where your logic is flawed is that it is easier to drive because it is a higher resistance, not a lower one, for the reasons i have explained.

if i dont know what im talking about, perhaps i shouldnt be an electronics engineering technologist!

-Jace

[Florian]

Ooops, how emberassing. Me mean the same thing, i just didnt understand it in the way you worded it.

-Flo

PS: I think i am stupid, because it just doesnt make any sense to me that the higher the resistance is, the easier it is to drive.

[Jace]

haha. dont worry, its confusing to be sure. its not so much the impedence that is the important thing to look at in making it easier to drive so much as the affect that it has on the current and voltage that makes it easier to drive (they are all related of course as ohms law states).

the higher resistance, causes less current draw and the less current you have to draw from your amp, the easier it is on it. at the same time though, the less current you have, the less power you will have as well since power (in watts) is found by voltage multiplied by current.

thats why we go for a matched load because it gives the best compromise between current draw and voltage dropped across the load (your speaker) as i described previously. that is where you will get the most power and a moderate current draw that your amp will be able to handle.

-Jace

[Florian]

Well now it makes sense, but it sure is twisted :p
My new speakers are the Apogee Scintilla's which have a 1ohm impedance. These are horrible to drive, but gladly i have a big Krell KSA-150 amplifier.

-Flo

[Jace]

ya. 1 ohm speakers are killer. it is so hard to get an amp to run stable when driving something like that. sounds like you have a decent setup for it though.

-Jace

[Florian]

Yup, the Krell is 110lbs and drives down to 0.5 ohm. Acording to Krell he pumps out 1760wpc into 1ohm load. The thing sucks more current from power outlet than Britney Spears. But its so nice to look at :p (the amp i mean)

[SpankingVanillaice]

I can say you can hook up 4 ohms speakers on a 8 ohms amp but only one pair of 4 ohms speakers you can hook up since if you hook up more the amp may fry.

[Florian]

I would not recommend a 4 ohm difference. Especially on tube equipment.

-Flo

[Gretchen_TX]

I very much appreciate all you guys taking the time to post your advice and comments. It seems that everyone agrees I will be okay running those speakers off that receiver, so I'll hook 'em up and try 'em out.

Thanks again, Gretchen

[RGA]

I would not recommend a 4 ohm difference. Especially on tube equipment.

-Flo

Why do you say this - many tube amps have a 4ohm tap -- low powered tube amps are practically impossible you'll blow the amp or the speakers --- even running certain ML's which dip to 1ohm...Low powered tubes will get very FUZZY sounding though.

What tube amps lack is a high damping factor generally so speakers needing it are out to lunch.

And Tube amps from VTL will drive any speaker anywhere -- the VTL Wotan is a 1250watt Tube amp that weighs an incridble 335 Lbs (packed) and incorporates 24 tubes per channel, 3 separate power supplies on a double deck chassis -- these ran the ML statrements at the 1998 show in LA and the Statements go to 1ohm and and maybe tougher 2ohms in the massive subwoofers -- this set-up produced 115db spl which is the spealers max.

How the amps sound I don;t know -- I have yet to hear an amp over 75 watts that I like enough to consider buying - but tubes can drive low impedences..

[Florian]

RGA ! use your brain for once and stop with this "possibility" stuff. Do you think that he has the possibility right now (no offence) to buy a 10K$ tube amp with 1.3kw? NO, it looks like he is around a 500$ budget. And the tube AMP's out there which are rated at 8ohm min should not be given a 4 ohm load. Noone is saying otherwise, we are simply recommending that he should only hookup whats recommended by his electronics.

Earth to RGA........

[RGA]

My receiver will drive any 4 ohm speaker out there -- and it is rated to 6ohms. It's the impedence swing of the speaker that matters more. bringing up the very few 1ohm speakers that exist is pointless -- the B&W DM 302 was an entry level speaker geared for entry level amplifiers (which means generally futless amps) and this speaker dipped to 3.1 ohms - any receiver can drive those speakers loud enough.

Driving it well and just driving it are not the same of course. Most tube amps even cheap ones have 4 ohm taps which means they can drive 4 ohm sepakers. You stated that tubes should be avoided as they won't like 4 ohms -- you said especially -- in fact it would be especially for S has SS hard clips tubes do not. -- Quad makes tube amps for electrostats.

[Florian]

That is not true. Not all amps drive 4ohm loads. 2ohm differences on a SS receiver are not vital, but i would not want to hook up a 4ohm Maggie on a Pathos TT and say thats ok, because he may be able to survive a bit.

Just match the Receiver and with the speaker load in a + - 2ohm range and you will be fine.

-Flo

[kfalls]

If you'll look at the specs in your owner's manual you'll find the answer to your original question. Under the amplifier section it does give its output as 100W @ 8ohms, but if you'll look at the dynamic power section the manual provides specs for max. of 140W x 2 @ 8ohms, 135W x 2 @ 4 ohms and 170 x 2 @ 2 ohm. These are not continuous power readings, but more of an indication of how well the amp will respond to instantaneous peaks. The fact they provide readings for other than 8 ohm loads is a good indication the amp is robust enough to handle current draw at the different impedances. Since impedance changes with frequency very few speakers provide a constant load to the amplifier. Try looking for parameters @ different impedances on cheaper receivers. Usually if they're there the distortion is much higher.