4 Ohm vs. 8 Ohm, what does it mean.....


Many of us know there are 4 ohm and 8 ohm speakers. (Like me). Many people dont know why (Like me). What are the design tradoffs for these different impedences? It would seem that a heavier load, ie, 8 ohm, would result in more accuracy, especially in the woofer....but I dont really know....thanks Mark
mythtrip
Sneaky follow on--what does it mean that McIntosh has always given its' ratings (even back in the 60's)at 2, 4, and 8 ohms? I assume its' a sign (guarantee?) of linearity. I run a 7270 and 7300.
In practical terms it means you are going to have major problems if you use an amp designed for 8 ohm loads with a 4 ohm speaker.
I had a relatively low powered amp (30 wpc class A, dual mono) which sounded real good. I decided to upgrade my speakers and bought a pair of Focus .7s. I was constantly kicking out the protection curcuitry in the amp. I brought the amp into the shop and had it checked out. They said there was nothing wrong with it but as soon as I began listening it did it again. Next I brought in the amp, pre-amp, and speakers along with their respective cables. The guy checked each piece out and didn't find anything wrong. I don't think he ever set everything up and listened to the system as a whole. After years of this I ran into a friend in the HiFi business in Milwaukee and explained it to him. He immediately said "it sounds like you're driving a four ohm speaker with an eight ohm amp."
I bought an amp capable of driving four ohms and never had another problem with the speakers.
Bill, Mac uses output transformers on their SS amps. As such, the amp sees a relatively consistent load regardless of the speaker it is connected to. That is, so long as the "most correct" tap is selected for that individual speaker. There are problems associated with doing something like this ( other than high cost ) though and that is why most other manufacturers avoid it. Even the best sounding tube amps ( like Atmasphere's and probably Tenor's ) don't use output transformers.

Using an output transformer is kind of like running hundreds of feet of zip cord speaker cable after working so hard to preserve the signal through-out the entire chain. It does lend a specific sonic characteristic to the signal though, and if that is your preference, so be it. I know what i like in a system and i set them up accordingly. I wouldn't expect anyone else to do any differently.

Nrchy, it sounds like you picked a speaker that was of low impedance and had a somewhat reactive phase angle. I'm sure that your 30 wpc amp could have dealt with the speaker IF the protection circuitry was not set quite as sensitive to triggering. This might have involved occasional clipping from the amp though, which happens more commonly than many folks would like to think. Whether or not the amp was a suitable match for the speakers without the protection circuitry would still remain to be seen if that approach had been taken. The fact that the manufacturer selected the trigger point on the amp that he did and the tech verified proper operation tells me that it was probably not up to driving the speakers in the manner that you wanted to use them. Sean
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I know that this is a gross generalization but I usually find that speakers with lower impedances have better bass.
Its way toooo general, Unsound.
You can grab an example on JM Lab Electra 926 where the nominal impedance is 6Ohm but it could be dropped down to 2.5.
My Totem Forests amps have a huge and resolving bass despite their tiny size and small 6" woofer. Their nominal impedance is 8Ohms and it doesn't go bellow 6. I was driving them with Pathos TwinTowers 35W/ch with enough loudness and clarity.
I might also generalize that speakers with lower efficiency have better bass while highly-efficient horns are only good for speach or voice...?