Thinking of getting a power amp.

[Pyrrho]

I was told by a stereo repair guy that most speaker companies actually do this. They list the "nominal" impedance, because impedance changes with frequency. I don't know if it's even possible to design a speaker that stays at exactly 8 ohms throughout the range of 20Hz - 20,000Hz.

Virtually all speakers vary in impedance according to the particular frequency in question. The "nominal" rating is supposed to be what you can "pretend" the speaker is overall for matching with an amplifier.

What is ridiculous is to rate a speaker at 8 ohms if it has a minimum impedance of 3 ohms. Normally, reputable speaker manufacturers keep the minimum impedance not too terribly far from the nominal rating. For example, it would not be uncommon for a speaker rated at 8 ohms nominally to have a minimum impedance of 7 ohms. That kind of thing is fairly common. But it is not to be expected that the minimum impedance would be less than half the nominal rating. It has been done, but it is the kind of thing that should not be, as low impedances can stress amplifiers that are not designed for it, and if the speaker is rated at 8 ohms, people will use it with an amplifier rated only to deal with 8 ohm speakers, not something dramatically lower.

So, if a company rates a speaker at 8 ohms nominally, when the minimum is 3 ohms, they are causing people to unknowingly stress their amplifier if it isn't designed for such a low impedance. This is something that can cost their customers money, as it may lead to early amplifier failure. That is why I have a problem with companies rating speakers so inaccurately.

The maximum impedance of a speaker may be considerably higher than the nominal rating, but having a high impedance will not stress the amplifier, so this isn't generally a problem.

 

[mr-ben]

It might be worth your time to read some opinions about amplification of Klipsch speakers over in the Klipsch forums: http://forums.klipsch.com/forums/4.aspx

 

[AcuDefTechGuy]

Better safe than sorry, right?

I also vote for getting an amp or receiver that can handle 2 ohms just to be safe!

Another example about impedance difference is my DefTech speakers. The BP7000s & 7001s have a minimum impedance of about 3 ohms, while the CLR3000 has a minimum impedance of about 2 ohms. However, DefTech says that these speakers have a nominal impedance of "4 to 8" ohms. I guess the 4 ohms might be appropriate.

But Better safe than sorry!

 

[mouettus]

Funny. I thought I had great speakers too (Polks) until I started listening more carefully and thinking the same thing as you. My metal CDs were getting pretty harsh in the high mids. Then I shopped for other speakers. Ended up with some Energy; a more laid back type of speaker so when the music screams at you, they don't reach your ears to tear them apart. It solved my problem. From what you are saying, I think you might be in the same wagon as me.

PSB image (so-so), B&W 600/700 and Energy C/RC are 3 brands of speakers I auditioned that I thought were more adequate for metal music. The thing about the klipsch though is that they have great dynamics, so you lose a little bit of that in most cases.

 

[Midcow2]

Get big cable too. Get seven humongous Power Amps

Better safe than sorry, right?

I also vote for getting an amp or receiver that can handle 2 ohms just to be safe!

Another example about impedance difference is my DefTech speakers. The BP7000s & 7001s have a minimum impedance of about 3 ohms, while the CLR3000 has a minimum impedance of about 2 ohms. However, DefTech says that these speakers have a nominal impedance of "4 to 8" ohms. I guess the 4 ohms might be appropriate.

But Better safe than sorry!

Better safe than sorry get some humongous cable also! Heat build-up in the smaller gauges (highjer gauge numbers) could potentially cause a fire. Get 00 gauge cable just to be safe. Better safe than sorry.

Also your receiver might not be big enough. Go with the best, do't worry about the cost. Get seven McIntosh humongous MC2KW Power Amps Better safe than sorry.

 

[PENG]

Virtually all speakers vary in impedance according to the particular frequency in question. The "nominal" rating is supposed to be what you can "pretend" the speaker is overall for matching with an amplifier.

What is ridiculous is to rate a speaker at 8 ohms if it has a minimum impedance of 3 ohms. Normally, reputable speaker manufacturers keep the minimum impedance not too terribly far from the nominal rating. For example, it would not be uncommon for a speaker rated at 8 ohms nominally to have a minimum impedance of 7 ohms. That kind of thing is fairly common. But it is not to be expected that the minimum impedance would be less than half the nominal rating. It has been done, but it is the kind of thing that should not be, as low impedances can stress amplifiers that are not designed for it, and if the speaker is rated at 8 ohms, people will use it with an amplifier rated only to deal with 8 ohm speakers, not something dramatically lower.

So, if a company rates a speaker at 8 ohms nominally, when the minimum is 3 ohms, they are causing people to unknowingly stress their amplifier if it isn't designed for such a low impedance. This is something that can cost their customers money, as it may lead to early amplifier failure. That is why I have a problem with companies rating speakers so inaccurately.

The maximum impedance of a speaker may be considerably higher than the nominal rating, but having a high impedance will not stress the amplifier, so this isn't generally a problem.

I would agree with you in general if those dips (to 3 ohms) are over a significant range of frequencies but of all the curves I have read those dips are over a very narrow range and normally not (or at least not always) in the 30 to 80 Hz range. As such, I am not concern about any well made amps or receivers being stressed as long as the overall average/nominal value is in the neighborhood of 8 ohms. It seems to me people sometimes like to brag about how difficult their speakers are to drive.

 

[rufas2000]

Break down and get a nice classical to test your setup.

I put in Handel's "Messiah". The recording uses period instruments (as opposed to instruments invented after Handel's time). I would give more details but its in the other room and I really should try to cut down on my walking while my toe heals from surgery. I think the company of musicians call themselves the Academy of Ancient Music (or close).

I really enjoyed the sound, my only concern is that during the "busiest" moments the lower vocals got lost a bit, if only for a few seconds a shot(during "forever and ever"). The boys choir is quite dominant, I'm not sure if that's the recording (well it is but how much) and how much is my speakers / setup.

I would try my Holst "The Planets" but honestly I don't know what to listen for. It always sounds good to my ears. Maybe I'll do further vocal testing with Beethoven's 9th (I think Snell conducted, from the 60s) or "The Compact Ring" (Wagner's "Greatest Hits", LOL, can't afford the full operas but I wish the Compact Ring was two CDs, a bit less compact). I have "Peer Gynt" with vocals (as was written for the opera I think) but not enough for testing purposes.

Jazz is the same way for me. Maybe I'll throw "Kind of Blue" or "A Love Supreme" in there just to enjoy it, again its very well recorded IMHO and always sounds good.

OTOH: Marvin Gaye would be a very good test subject for vocals as he has an extensive range, "Whats Going On?" or "Lets Get It On" would work nicely.

Thanks for the suggestion.

 

[mtrycrafts]

I put in Handel's "Messiah". The recording uses period instruments (as opposed to instruments invented after Handel's time). I would give more details but its in the other room and I really should try to cut down on my walking while my toe heals from surgery. I think the company of musicians call themselves the Academy of Ancient Music (or close).

I really enjoyed the sound, my only concern is that during the "busiest" moments the lower vocals got lost a bit, if only for a few seconds a shot(during "forever and ever"). The boys choir is quite dominant, I'm not sure if that's the recording (well it is but how much) and how much is my speakers / setup.

I would try my Holst "The Planets" but honestly I don't know what to listen for. It always sounds good to my ears. Maybe I'll do further vocal testing with Beethoven's 9th (I think Snell conducted, from the 60s) or "The Compact Ring" (Wagner's "Greatest Hits", LOL, can't afford the full operas but I wish the Compact Ring was two CDs, a bit less compact). I have "Peer Gynt" with vocals (as was written for the opera I think) but not enough for testing purposes.

Jazz is the same way for me. Maybe I'll throw "Kind of Blue" or "A Love Supreme" in there just to enjoy it, again its very well recorded IMHO and always sounds good.

OTOH: Marvin Gaye would be a very good test subject for vocals as he has an extensive range, "Whats Going On?" or "Lets Get It On" would work nicely.

Thanks for the suggestion.

Well, you can listen to those classical and see if you hear the shortcomings you head from that metal music? Most likely you won't
That segment where vocals get lost, perhaps it is just normal acoustic masking at play. Our ears don't hear every bit of info out of the speakers but is masked. This is what makes perceptual coding to work. Through research they know what can be discarded since it is just not heard in the first place but masked.