My speakers are three-way system and the stickers at speaker terminals are labeled 8 Ohms nominal. However, I have measured the drivers’ resistances (Re) by a RLC meter and they’re shown as follows:
Tweeter = 3.2 Ohms
Midrange = 3.4 Ohms
Woofer = 3.6 Ohms.
IMO, these all should be 4-Ohm drivers.
So, why the manufacturer claimed they’re 8 Ohms nominal?
I know the speakers have an impedance curve which could be fluctuated depends on frequency. But the 8 Ohms nominal is the result of averaging with the peaks on the impedance curve, isn’t it?
Tweeter = 3.2 Ohms
Midrange = 3.4 Ohms
Woofer = 3.6 Ohms.
IMO, these all should be 4-Ohm drivers.
So, why the manufacturer claimed they’re 8 Ohms nominal?
I know the speakers have an impedance curve which could be fluctuated depends on frequency. But the 8 Ohms nominal is the result of averaging with the peaks on the impedance curve, isn’t it?
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Because they can do what they like -there are no obligatory standards beyond safety, and nominal values like that are almost meaningless (I still don't know why you put such value on them). Chances are it will probably lurk somewhere vaguely near that in practice given the real world frequency varying impedance load of the drivers, numbers and wiring of units, changes in impedance load from filtering etc., but if you're expecting anything more rigid, you'll be waiting a very long time.
The IEC standard (IEC60268-3) allows any impedance above the rated value, but limits the impedance below. It does not allow the rated impedance to fall below 80% of the nominal value at any frequency.
As Scottmoose pointed out, standards are not obligatory.
That said, your DC resistance measurements are not the impedance, though it would be unlikely that their minimum impedance would be only 6.4ohms.
Do you have a system impedance measurement?
It's still possible the system impedance can reasonably be considered 8 ohms.
It's still possible the system impedance can reasonably be considered 8 ohms.
If you look at some woofer datasheets you will quickly see that Re is significantly lower than the nominal impedance. However, I do generally see closer to 6 ohms Re on an 8 ohm driver.
Truthfully, Re has nothing to do with impedance. You can only know impedance from the graph.
Truthfully, Re has nothing to do with impedance. You can only know impedance from the graph.
You need dats v3 for more accurate measurements. Especially final speaker including crossover.
https://www.parts-express.com/Dayto...ter-Based-Audio-Component-Test-System-390-807
You can infer the likely minimum impedance by taking individual DC resistance measurements of drivers, but a much better option as adason said is to do a final system impedance sweep. Ugg10 here just recently made a cheap jig to which allows REW to be used to do such a measurement:
https://www.diyaudio.com/community/threads/impedance-measurement.415830/#post-7752293
Failing that - purchasing DATSv3 or similar will allow the same (if you want a plug and play solution).
https://www.diyaudio.com/community/threads/impedance-measurement.415830/#post-7752293
Failing that - purchasing DATSv3 or similar will allow the same (if you want a plug and play solution).
If you want to check the system minimum impedance but only have a DVM,
drive the speaker with a sine wave through a 1k ohm 1% resistor.
Adjust the frequency for minimum amplitude across the speaker, probably around 500 Hz.
Then calculate the approximate system impedance at that frequency by (with R in ohms) :
R = 1000 x ( Vspeaker / Vgenerator )
Of course you can measure the impedance magnitude at other frequencies as well,
given the frequency limitations of your DVM
drive the speaker with a sine wave through a 1k ohm 1% resistor.
Adjust the frequency for minimum amplitude across the speaker, probably around 500 Hz.
Then calculate the approximate system impedance at that frequency by (with R in ohms) :
R = 1000 x ( Vspeaker / Vgenerator )
Of course you can measure the impedance magnitude at other frequencies as well,
given the frequency limitations of your DVM
If the measurements were precise, woofer is closer to nominal "6 ohms" than to nominal "4 ohms", so whole loudspeaker should be declared as "6-ohm". Bear in mind - minimum impedance is higher than DC resistance. And according to IEC standard, minimum impedance should be at least 80% of the nominal impedance. Hence, nominal "6-ohm" loudspeaker has 4.8 ohms minimum impedance and lower than 4.8 ohms DC resistance. Nominal "4-ohm" loudspeaker has 3.2 ohms minimum impedance and lower than 3.2 ohms DC resistance.
Midrange and tweeter usually have serial resistor for attenuation, so minimum impedance (of the whole loudspeaker) in their passbands may be higher than their natural minimum impedance. All that leads to conclusion that this loudspeaker is nominally 6-ohm. Of course, only measured impedance vs frequency will tell the truth.
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You don't 'need' DATS (or its WT3 predecessor for that matter) for that -you can make a simple resistor jig to use with REW and other similar software if you feel so inclined. It's very convenient -I have v2 & v3 myself, along with said jig in a little box I made. All of these are low voltage methods though, so while useful, depending on what you're doing you can expect to see variations to measurements taken at a higher voltage drive, which are arguably more representative of actual usage.
Yes, you can make simple resistor jig...but presscot did not do it. That's why i suggested dats. With simple jig you get impedance, once you plot it yourself. But with dats you get Fs, Qts, Qes, Qms, Le, and so forth.
All true but the real question is impedance at the nominal crossover frequency and that may well be 8 Ohms.
Think about the BBCs LS3 mini monitors where there were 15R and 16R versions; that I know about, there may have been others
Think about the BBCs LS3 mini monitors where there were 15R and 16R versions; that I know about, there may have been others