8 Ohm 6 Ohms 4 Ohms aaaarrrrgggghhhh!!!!

[twochordcool]

OK, so if I'm starting to build a stereo and home theater from scratch, and I am probably looking at the higher end budget equipment - Should I concern myself with impedance?

The only reason that I ask is because I have started with speakers, and I am shying away from very good speakers for their impedance ratings, ie Monitor Audio Bronze B2's (6 Ohm) and Epos ELS-3's (4 Ohms).

What do I have to take into consideration if I will be looking for a 6.1 receiver under $500?

Are most of those receivers going to be strictly 8 Ohm impedances?

Will I have 6 and 4 Ohm choices in this price range?

Are there advantages of buying a receiver rated at 6 and 4 Ohms?

 

[Spiffyfast]

OK, so if I'm starting to build a stereo and home theater from scratch, and I am probably looking at the higher end budget equipment - Should I concern myself with impedance?

The only reason that I ask is because I have started with speakers, and I am shying away from very good speakers for their impedance ratings, ie Monitor Audio Bronze B2's (6 Ohm) and Epos ELS-3's (4 Ohms).

What do I have to take into consideration if I will be looking for a 6.1 receiver under $500?

Are most of those receivers going to be strictly 8 Ohm impedances?

Will I have 6 and 4 Ohm choices in this price range?

Are there advantages of buying a receiver rated at 6 and 4 Ohms?

First off most speaker impedences aren't actually 8ohms most say they are 8ohm compatible or something like that, dont remember the actual terminology most use. Alot of speakers are closer to 6ohms and a receiver in the 500 dollar range should be able to handle them. The 4ohm speakers you may have trouble with depending on the particular receiver, especially more budget concious ones. Hope that helps ya out.

 

[Takeereasy]

I have PSB 2B's as my bookshelf speakers and they are rated as 6ohm nominal and 4ohm minimal. That said my Sony receiver never had a problem driving them and my new Marantz gets nowhere past half volume for fear of deafening myself. The impedence of a speaker is not the only indicator of how much of a load a speaker rewuires to drive it effectively. Unless those speakers are dipping below 4ohms you should not have too much of a problem. A speaker rated at 4 ohms nominal is likely to dip below 4 ohms much more often than one rated at 4 ohms minimal. I don't know how they rated those epos speakers but I'd bet that the 4 ohms is a minimal because they are budget components, and what's the point in making $300 speakers that need a $1000 amp to drive them? From all of your suggestions I still like the Monitor Audios (the B2's)

 

[tbewick]

I'd go along with the previous posts, in saying that a half-decent receiver would drive such speakers. I've got a fairly cheap Marantz A/V amp that in the manual says will drive low impedance speakers because of its high current capability. Unless you're trying to fill a very large room and are sitting far away from the speakers, then a normal 40 watt amplifier should do the job no probs.

I have heard that B&W and probably other speaker manufacturers use Krell and other v. powerful amps when testing their equipment/measuring performance. They double their power output per halving of impedance, eg. 3000 watts into 8 ohms, 1500 watts into 4 etc. This power level is most likely used to test the speakers to their absolute limit and aren't what you'd encounter in most domestic situations.

There's an article about this on the main Audioholics web site.

 

[annunaki]

It should read " 1500w at 8 ohms, 3000w at 4 ohms"

 

[tdeluce]

THX Ultra2 receivers are suppose adhere to very high
performance standards all the way down to a 3.2 ohm
load.

Many receivers will spec performance as follows:
---
7 Channels equal power amplifier section
125 watts per chan (8 ohms, 20 Hz-20 kHz, <.05%THD)
150 watts per chan (6 ohms, 20 Hz-20 kHz, <.05%THD)
---
the above tells you that the receiver amps were capable
of driving both 8 ohm and 6 ohm loads equally well.


On the other hand if find the following specification:
----
7 Channels equal power amplifier section
120 watts per chan (8 ohms, 20 Hz-20 kHz, <.05%THD)
160 watts per chan (6 ohms, 1 kHz, <.7%THD)
-----
the fact that the specification is showing THD at only
one frequency is a huge red flag that there was a problem
driving the 6 ohm load or else the receiver manufacturer would have provided the spec over the entire frequency range. Also note the increase in THD from .05 to .7

Also look out for a spec that looks like this:
----
120 watts per chan (6 ohms, 40 Hz-20 kHz, <.05%THD)
---
by eliminating 20Hz to 40Hz from the bandwidth, the
receiver manufacturer is able to show much better numbers
since 20Hz to 40Hz often provides the most trouble.

Using a separate subwoofer with bass management
helps significantly since the frequency range for
the seven amps is more like 60 or 80 Hz to 20KHz.

There are very good 8 ohm speakers and if use them
instead of 4 ohm speakers you won't have to worry
about any of these as long as the receiver operates
as follows:
--
125 watts per chan (8 ohms, 20 Hz-20 kHz, <.05%THD)
----
Although I would defnitely still use a separate subwoofer
with bass management in most cases.

 

[MBauer]

Easy and complicated

As has been posted look at the specs of the receiver and in almost all cases (with a $500 major brand receiver), the receiver should drive 4, 6, or 8 ohms. SPL will vary, but that then you have to know the efficiency of the speakers

Determining the impednace of a speaker, at different frequencies is a bit trickier and you shouldn't have to worry about it, let the designers worry about it.

Also, has been stated, you can get some terrific speakers rated at 8 ohms.

Before buying you should determine the room volume, listening distance, types of material you listen to, volume levels, etc. Then you could post that info here and a bunch of knowledgeable people will lend a hand.

 

[Buckeyefan 1]

Linear ratings on amps should be (ie)
120w+120w 8 ohms .05 thd
180w+180w 6 ohms .05 thd
240w+240w 8 ohms .05 thd
But...

Most amps have current limiting circuitry. That is why ratings rarely double down with half the ohm rating. Unless very expensive, large caps are used in conjunction with proper heat distribution, manufacturers must use current limiting.