How much does impedence matter ?

 

New member
Username: Madhuds

Post Number: 4
Registered: Jul-10
I am trying to make a decision on the speakers and one thing i come across when comparing Jamo speakers to most of the others, impendence (ohms) is 6 while most other brands are 8.
My question is, what is the nominal impendence for bookshelf speakers. Would a diff of 2 ohms matter a lot ?
 

Gold Member
Username: Magfan

USA

Post Number: 1402
Registered: Oct-07
Only if your amp / receiver simply didn't like lower impedance.
6 ohms 'nominal' is not wacky at all by modern standards.
A 4ohm speaker which dips to 2.5 ohms is more problematic.
Also, BIG swings in impedance are generally worse than small swings.
The other measurable, which is seldom mentioned, is that of phase angle. How much the voltage and current are 'out of step'. In a pure/perfect resistor, they rise and fall together. Add an inductor or a capacitor and they begin getting out of 'sync'.
The worst speaker load is one that has both wide impedance AND wide phase angle swings.
In short, a speaker of 6 ohms which has few peaks or valleys in either phase or impedance would be a better load than an 8 ohm speaker with huge excursions of both phase and impedance.

You need some further information. I'd write to Jamo and ask if they have phase data. I'll bet they DO, as a normal part of speaker development, but may not totally share it. Never tried.

Stereophile tests routinely include such data.
 

Platinum Member
Username: Nuck

Post Number: 15245
Registered: Dec-04
You are taking a good approach to making a set, ar.

search stereophile data for any speaker you like, see whats there. It is free learnin' for an informed enthusiast, as Leo suggests.

If you are looking at speakers for your tube amp, read here.

http://www.symphonysound.com/articles/tubefriendly.html

The characteristic responses from the speakers to sand amps is similar, the amplification, not so much.
 

New member
Username: Madhuds

Post Number: 5
Registered: Jul-10
The amp/receiver that i am gonna have these speakers hooked up will be Pioneer 21TXH
 

Silver Member
Username: Kbear

Canada

Post Number: 726
Registered: Dec-06
http://www.symphonysound.com/articles/tubefriendly.html

The Symphony Sound article is a good one when it comes to understanding impedance. Basically, the lower the impedance the harder a speaker is to drive. Nominal impedance tells us very little, because impedance varies across the frequency range...it's always changing when you play music. Because of this a speaker that quotes a nominal impedance of 6 might in fact be easier to drive than one that quotes 8. This would be so if the lowest impedance reached for the 6 ohms speaker is 5, while the lowest reached for the 8 ohm speaker is 4 ohms. It happens quite often. A low impedance at a low (bass) frequency is tougher than one at a higher frequency, and phase angles that vary greatly from 0 at these low points make things very challenging for an amp.

That's pretty much the extent of my knowledge, and while I think I've got a good grip on this topic it's at a pretty basic level. One would hope a speaker quoted at 6ohms nominal impedance isn't too demanding (otherwise they would have quoted 4ohms). But unless one can find the impedance curve online (not always possible) then you probably won't know for sure. Listening would be the test.
 

Gold Member
Username: Magfan

USA

Post Number: 1406
Registered: Oct-07
0? Zero? That is pure resistive and the EASIEST to drive.

I rather have the electrical characteristics of my panels, 4 ohm, no less and moderate phase angles than some wacky speaker going from 3 to 13 a couple times with a phase angle of -45degrees at the same place as a nice dip to 4 ohms.....at 100hz.......

Does the Pioneer have a 6 ohm switch? Is it rated to 6 ohms?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 15061
Registered: May-04
.

Read this; http://www.ecoustics.com/electronics/forum/home-audio/628565.html), then ask specific questions.

Pioneer HT receivers are not widely known for their ability to deliver current into low impedance loads. The guys have given good information by telling you to research not the "nominal" impedance but the lowest impedance point in the speaker's impedance curve (this will occur at a frequency point and the impedance will dip to that point and rise from that same point) and to also know about the speaker's phase angle as low impedance by itself is not a deal breaker. Where in the speaker's frequency response these two elements become their most difficult for the amplifier is what you want to know. The Symphony article is a good start in understanding impedance and phase. What you should take away from it is impedance must be as stable as possible, as high as possible over the broadest frequency response and the electrical phase angle should be as close to 0° neutrality as possible. If the impedance dips but the phase ange is close to 0°, the phase cancels the impedance to a large extent and vice versa. While that all sounds like mumbo-jumbo now, reading will explain specifically what you are looking for in a speaker.

Unfortunately, no one tests amplifiers for sustained current delivery which is the element required to successfully drive difficult loads. You have to rely on past history in most cases and Pioneer is not known for its brute strength in this arena. Should your speakers be difficult to drive at very low frequencies, then the addition of a subwoofer to your HT system can somewhat make up for the failings of the amplifier. It would be better, of course, to have an amplifier that didn't require additional back up current delivery but that sort of HT receiver tends to be expensive. On the otherhand, it looks like you're prepared to drop a goodly sum on the Pioneer. Maybe you should look at the receiver first and find the highest current delivery for the dollar, then your speaker choices are not so narrowed by the restrictions of the amplifier. That normally equates to the heaviest amplifier for your dollar as weight comes mostly from the power transformer which is largely responsible for delivering current (amperage) to low impedance loads. If the amplifier has been well designed and implemented, you're very likely going to find less geegaws and features being sold. The money must go somewhere and, if the money is being put into a well built amplifier, then the money for nonsense features isn't there. How many surround modes do you really think you might use? A plain face plate often hides a terrific amplifier.


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New member
Username: Madhuds

Post Number: 6
Registered: Jul-10
This is what i could find on Pioneer 21TXH receiver
Surround Power - 110W x 7 (20Hz - 20kHz, .09% THD @ 8 ohms, All Channels Driven)
Stereo Power - 110W x 2 (20Hz - 20kHz, .09% THD @ 8 ohms
 

Platinum Member
Username: Nuck

Post Number: 15258
Registered: Dec-04
If anyone could prove the unit to deliver 1/3.....1/4 of that power number, into a 7 kind speaker load, I will eat my hat.

ar, forget the #'s for now, look at the electical handshake and keep listening to as much as you can.

Take notes to yourself on listening.
 

Gold Member
Username: Stu_pitt

Irvington, New York USA

Post Number: 3921
Registered: May-05
If impedence didn't matter, Pfizer wouldn't have made all that money on Viagra.

Sorry. I'm in the middle of moving and need a distraction.
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