Speaker Impedance / Amp Question

Hello,

I'm looking to fit a stereo system to my woodwork shop, nothing fancy.

I have a set of Canton Movie 75 speakers that were given to me, and I've just bought a Tangent Ampster BT II amplifier.

I want to wire 2 satellite speakers to each of the 2 amp speaker connections (L/R), one in each corner of the workshop. The amp also has the output for a powered sub, so I'll use that too.

The Tangent spec sheet says :

1621935182468.png


The Canton spec sheet says (as a range, confusingly) :

1621935624697.png


If I put my multi-meter on the speaker terminals, I get 3.9Ω.

I understand that the 2 speakers could be wired in either series or parallel for each channel.

Is it correct in this case to wire them in series (~8Ω total impedance), as wiring them in parallel would result in an impedance of less than 4 (~2Ω Total impedance)?

Other speakers I have state the impedance on the speaker next to the terminals, but these do not.

Thanks in advance,
 

AmericanAudio

Active Member
AVForums Sponsor
Yes you are right, at that impedance you really should wire them in series to keep them in range of the amp.

As you have the capability, i'd measure again once you have them set up, just to double check.

Then for the first few time keep an eye on the amp and its heat dissipation.

V.
 
Yes you are right, at that impedance you really should wire them in series to keep them in range of the amp.

As you have the capability, i'd measure again once you have them set up, just to double check.

Then for the first few time keep an eye on the amp and its heat dissipation.

V.
Great, thanks for your help!

Before running the cables in the workshop, I will wire up on the bench and test as you suggested, thank you!
 

3rdignis

Active Member
If your using thin speaker wire?
14 gauge is better.
 

phil t

Well-known Member
If I put my multi-meter on the speaker terminals, I get 3.9Ω.
It's a common misconception that resistance and impedance are the same thing.

What you did was measure the resistance of the circuit, not the impedance.

Impedance is a combination of resistance, inductive reactance and capacitive reactance.

1622018706676.png

Both inductive and capacitive reactance change with frequency, which is why impedance is sometimes given a range of values (max - min).
Mostly what is quoted is a nominal figure.
 

3rdignis

Active Member
IEC standards is
80% nominal >= minimum ohms

4ohms x 0.8 = 3.2 ohms min.

Parallel that gives 1.6 ohms (or trouble)
 
If your using thin speaker wire?
14 gauge is better.
Because it's lower resistance over distance? Some of the runs might be quite long, so I will use 16GA regardless, thank you.
 
It's a common misconception that resistance and impedance are the same thing.

What you did was measure the resistance of the circuit, not the impedance.

Impedance is a combination of resistance, inductive reactance and capacitive reactance.

View attachment 1518298
Both inductive and capacitive reactance change with frequency, which is why impedance is sometimes given a range of values (max - min).
Mostly what is quoted is a nominal figure.

IEC standards is
80% nominal >= minimum ohms

4ohms x 0.8 = 3.2 ohms min.

Parallel that gives 1.6 ohms (or trouble)

Yes, I'm aware that impedance is reliant on frequency and inductive and capacitive loading, but not that it mattered particularly with speakers.

The documentation for the speakers says 4...8Ω, but does not mention nominal. Are they just covering their arse by quoting a range?

I'm happy enough that the speakers will work fine in series, with good enough wires. Thanks for all the help. This is going in a workshop so not really hi-fi at all, but I like the size and features of the ampster and the speakers were dirt cheap, basically unused and have nice brackets for mounting them.
 

Ugg10

Distinguished Member
@electricworry Remember the AWG (Gauge) system for wire size reduces in number as the diameter/cross section increases and the resistance decrease with increases in diameter/cross section. Therefore 16AWG is smaller than 14AWG and you will need larger wires the longer you intend on running them. Typically 13AWg is pretty close to 2.5sq.mm cross section and is typially Ok with runs up to 15m for a nominal 8 ohm load.


 

phil t

Well-known Member
Yes, I'm aware that impedance is reliant on frequency and inductive and capacitive loading, but not that it mattered particularly with speakers.

The documentation for the speakers says 4...8Ω, but does not mention nominal. Are they just covering their arse by quoting a range?
Possibly they're quoting a min and max z, based upon frequency response of the speaker?
 

Jules Tohpipi

Well-known Member
The documentation for the speakers says 4...8Ω, but does not mention nominal. Are they just covering their arse by quoting a range?

Speaker impedance is inherently a range, regardless of who might attempt to summarise it into a single figure to simplify things - including those who would stick a multimeter into the back to measure the DC resistance of the bass driver only…
 
Last edited:
@electricworry Remember the AWG (Gauge) system for wire size reduces in number as the diameter/cross section increases and the resistance decrease with increases in diameter/cross section. Therefore 16AWG is smaller than 14AWG and you will need larger wires the longer you intend on running them. Typically 13AWg is pretty close to 2.5sq.mm cross section and is typially Ok with runs up to 15m for a nominal 8 ohm load.



I meant to say 14AWG, not 16! There's plenty room to fit the larger CS stuff so no reason not to.
 

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