Impedance: In Speakers

[JJ]

Exactly what does impedance in speakers and receivers refer to, outside of the basic electrical definition - and what should be avoided in terms of mixing/matching impedance of speakers and receivers? And what is to actually be used?

[richteer]

Originally Posted by JJxiv1215

Exactly what does impedance in speakers and receivers refer to, outside of the basic electrical definition - and what should be avoided in terms of mixing/matching impedance of speakers and receivers? And what is to actually be used?

A speaker's impedance is essentially its resistance, so the lower the impedance, the more current will be required to drive it at any given level. The "normal" speaker impedance is 8 ohms, so anything less than 8 ohms can be considered low impedance. Note that a speaker's impedance has no relationship whatsoever to its quality.

The impedance specified by receivers isn't their output impedance, but the impedance of the speakers they're expecting and are designed for.

Using speakers of a higher impedance presents no problems, but using a speaker that's much lower than the receiver is rated for will result in the receiver running out of headroom, or worse.

Typically, receivers designed to be OK with 4 Ohm loads tend to have much more beefy power supplies than those that aren't. A 4 Ohm speaker requires twice as much current than an 8 Ohm speaker for a given output, hence the larger power supplies (which can supply more current).

[JJ]

So a receiver such as the Onkyo 605 with an amplifier output of 90 watts/8 ohms could not be connected with speakers that have only 3 ohms?

[rigpig]

Originally Posted by JJxiv1215

So a receiver such as the Onkyo 605 with an amplifier output of 90 watts/8 ohms could not be connected with speakers that have only 3 ohms?

...a receiver should have an output rating for lower impedance as well, another power rating @ 4ohms for example....to give you some sort of barometer of what it's amp section can do with tougher loads. Generally, lower/midline rcvrs will struggle with lower impedance loads. Output distortion will be higher as well. 3ohm speakers may not be the best idea no.

[Clark Kent]

Most mass market receivers have no problem with 6 or 8 ohm speakers, at least if you don't push the volume to ear shattering levels. But the lower end receivers do have bigger problems with 4 Ohm and lower speakers. Most 4 Ohm speakers are meant to be driven with dedicated amps or the very high end of receivers. Hook a 4 Ohm speaker up to a cheap receiver and you can expect clipping and possible damage at some point. Your receiver manual will tell you what load it can handle.

[crackinhedz]

Originally Posted by JJxiv1215

So a receiver such as the Onkyo 605 with an amplifier output of 90 watts/8 ohms could not be connected with speakers that have only 3 ohms?

Onkyo TX-SR605 User Manual (Pg.20):

•North American models: Only connect speakers
with an impedance of 6 ohms or higher. If you use
speakers with a lower impedance, and use the amplifier
at high volume levels for a long period of time, the
built-in protection circuit may be activated.
• Other models: You can connect speakers with an
impedance of between 4 and 16 ohms. If the impedance
of any of the connected speakers is 4 ohms or
more, but less than 6 ohms, be sure to set the minimum
speaker impedance to “4 ohms” (see page 51). If you
use speakers with a lower impedance, and use the
amplifier at high volume levels for a long period of
time, the built-in protection circuit may be activated.

[phlydude]

I used to run AR3s (huge monsters) that were 4Ω and I was constantly blowing fuses in my dedicated amp (but I was 13 at the time and didn't understand the electrical nuances of home audio).
I got around it by wiring another set of 4Ω speakers in series to each speaker (MTX truck boxes....hey, I was 13)
Most home speakers are 8Ω and receivers are built to handle them.
If you have speakers of a different impedance, they probably weren't meant for the application that you are using them for.

Those AR3s were acquired during a church sale for $30 for the pair. They were church PA/organ speakers...but they had the bass I was looking for.

[Pilam69]

Originally Posted by JJxiv1215

So a receiver such as the Onkyo 605 with an amplifier output of 90 watts/8 ohms could not be connected with speakers that have only 3 ohms?

If you hook that up you risk permanently destroying your amp and possibly your speakers as well. I'm betting the protection circuitry would kick in really quickly and even then it MIGHT not prevent damage. You'd be kicking out a lot of heat from your receiver as well.

You would need an EXTREMELY beefy amp to run a 3 ohm load.

Edit: Could you? Yes. Should you? No.

[d_rob1031]

Originally Posted by Pilam69

If you hook that up you risk permanently destroying your amp and possibly your speakers as well. I'm betting the protection circuitry would kick in really quickly and even then it MIGHT not prevent damage. You'd be kicking out a lot of heat from your receiver as well.

You would need an EXTREMELY beefy amp to run a 3 ohm load.

Edit: Could you? Yes. Should you? No.

+1, if the magic blue smoke comes out of the machine you can't ever get it back in there. Most HTIB speakers are 3ohm sets so its bad news to plug those speakers into a real man's (or woman's in mistik's case) receiver. If you're gonna spend the money on the amp/receiver, take the time to save the money to buy the correct speakers.

[NJMetsFan]

Ohms is resistance. The higher the ohms the higher the resistance. Think of it like a filter. If you can get amp that has an output of 100w @ 8 ohms per channel, that would be better than an amp that has an output of 100w @ 4 ohms per channel. The 4 ohm amp has less resistance and your THD (signal to noise) will go up, meaning you will have more unwanted noise.

It would be best to match the speakers and the receivers recommend impedence. Going to a higher ohm rating on the speakers means your signal will be cleaner much it will probably be underpowered. Going to a lower ohm rating, you will get more power to the speakers, but the signal is dirtier.

Here is a thread were you can get more info on this topic. I made a few posts in there as well.

https://forum.blu-ray.com/showthread...highlight=ohms

[My_Two_Cents]

Good information in here. I'm in the same boat. I purchased a set of Carver Cinema 5.1 speakers from Costco for a steal right before Carver either went out of business or stopped making speakers (10+ years ago). They are great sounding, and have worked well in my HT set-ups over the years, though they are 4 ohm speakers. I don't typically play them at, what I would consider, loud volumes, and I've never had a receiver kick-out or overheat, and I've never noticed any sound distortion. I purchased my current Yamaha several years ago because it had a 4/6 ohm selector switch. Friday I was able to get in on the ShopOnkyo.com TX-SR705 refurb deal, and I see from reading the owner's manual that it also has a setting for 4 ohm speakers. I assume I will be okay with this receiver/speaker combination?

I love my Carvers, and really do not want to replace them at this time or in the forseeable future.

[moviefan]

The important thing is DON'T MIX SPEAKERS OF DIFFERENT OHM RATINGS!

[Clark Kent]

Originally Posted by moviefan

The important thing is DON'T MIX SPEAKERS OF DIFFERENT OHM RATINGS!

+1

Don't mix 4 Ohm and 8 Ohm speakers in your setup. That will really mess up a receiver.