Understanding Ohms Help?

[jackz4000]

Today alot of speakers (and receivers) are rated at 6 ohms. I have a vintage Pioneer SX-1250 receiver rated at 160 rms watts/pr/ch @ 8 ohms. I'm looking at new speakers. Pioneer tech support told me running 6 ohm speakers is fine with this high current receiver. Big power supply so no problem. Anyone who can simply explain this ohms/amps/speakers thing to me. Whats going on here? The more I learn, the less, I realize.... I know, Thanks, Jack

[Smokey]

Yes, Ohms and power subject can get complicated.

Generally, the lower the speaker ohm is (as to compared with amp's speaker ohm rating such as 160 rms watts/pr/ch @ 8 ohms), the more power it demands. So if you cut the speaker load in half to 4 ohms, then theoretically, the output power of your amp should double to 320 watts.

But the good news is that for typical listening habits, we only use 1-10 [rms] watts of amp's power output. So generally one should be alright with using lower ohm speakers with their amps (than what the amps is rated for), as long as we don't play it too [window rattling] loud, and/or speakers sensitivity is not too low (below 86 db) :)

[topspeed]

Today alot of speakers (and receivers) are rated at 6 ohms. I have a vintage Pioneer SX-1250 receiver rated at 160 rms watts/pr/ch @ 8 ohms. I'm looking at new speakers. Pioneer tech support told me running 6 ohm speakers is fine with this high current receiver. Big power supply so no problem. Anyone who can simply explain this ohms/amps/speakers thing to me. Whats going on here? The more I learn, the less, I realize.... I know, Thanks, Jack
Disclaimer: I'm not an engineer. That said, I'll take a shot:

Ohms are a way of measuring resistance. A speaker is a resistive load and this load will vary dramatically depending on what it is asked to do. The higher the number, the easier it is to drive, the lower the harder. When speakers are rated a 8, 6, or 4 ohms, understand that this is their nominal rating and they can and will vary from this rating considerably. An extreme example would be planer or 'stats, designs with notoriously tricky loads. A Martin Logan Ascent i is 4 ohm nominal but will present 1.2 ohm dips. This is a brutal, amp devouring drop that will tax great amps and send lesser amps running home to their protection circuitry. Therefore, when looking for speakers, you should not only pay attention to the nominal ohm rating, but more importantly the minium rating because it is here that your amp will earn its keep.

My advice is to find a speaker that you like first. This way you can always purchase an amp that is capable of driving them properly. In other words, make sure it is rated as 'stable' for the given load. An amp that is asked to go beyond it's design parameters will either clip, shut down, or eat itself. Needless to say, none of these are a good thing with clipping giving you the value added bonus of killing your speakers too.

As it is, while your Pioneer is likely a very competent amp, I for one wouldn't even consider hooking it up to a set of ML's, "high current" or not.

Hope this helps.

[jackz4000]

Its a little more clear now. Thanks. I saw some graphs of speakers ohms resistance and that an 8 ohm nominal speaker will easily drop down to 5 ohms etc. I guess volume level has alot to do with it? Although I am not sure. Some high end amps specs say they are stable down to 1 ohm.

My 1250 is switchable for either 8 ohm or 4 ohm loads and takes mixed loads. As I understand it the lower the ohm (resistance) the harder the amp has to work, especially at higher volumes.

I currently have been running 8 ohm speakers as mains and 6 ohm speakers as "B" speakers without any problems.

I went on a spree over the last couple days and bought all 8 ohm speakers to replace the current ones.

[topspeed]

I guess volume level has alot to do with it? Although I am not sure. Some high end amps specs say they are stable down to 1 ohm. Actually, it's not so much volume as frequency. Woofers are harder to drive than tweeters, if I remember right.

As I understand it the lower the ohm (resistance) the harder the amp has to work, especially at higher volumes.Righto!


I went on a spree over the last couple days and bought all 8 ohm speakers to replace the current ones.Congrats! Hopefully you purchased based on sound and not ohms. Enjoy your new toys.

[jackz4000]

Although, ohms load was a consideration. Did not want to run 4 ohms. Got 2 pairs of vintage JBL's.