8 vs. 16 OHM

[BirdmanPA]

I am currently looking at a couple of pairs of UHF tweeters to add to my S7R's. One is a pair of O77 8 OHM glass tweeters and the other is a pair of 2405 Slot 16 OHM tweeters. I have been told and I have read differing opinions on this issue, 16 vs. 8 OHM UHF tweeters. I need to know if it is going to present a problem if I use the 077's in the existing system where the drivers are 8 OHM, or if I need to stay with 16 OHM tweeters. I have read and been told that all the tweeters, whether 16 or 8 OHM, test out the same and mixing them would not be a problem. Does anyone know categorically whether this is true or not? Any help would be greatly appreciated.
Birdman

[Earl K]

I have read and been told that all the tweeters, whether 16 or 8 OHM, test out the same and mixing them would not be a problem. Does anyone know categorically whether this is true or not? Any help would be greatly appreciated.

Here are impedance graphs run by Mr. Widget . ( Click on the following pic to see the post that it's taken from ).

http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=8985&stc=1&d=1121547524 (http://audioheritage.csdco.com/vbulletin/showpost.php?p=62922&postcount=51)

- As you can see,,, the impedance labelling (of 8 or 16 ohm ) on either a 077 or 2405H , is very misleading ,,, they are neither . They are both, more like 10 to 12 ohms.

[BirdmanPA]

So bottom line would be that it will make no difference wheth the tweeter I use is "16 OHM or 8 OHM", correct?
And thank you for your response.

[Earl K]

So bottom line would be that it will make no difference wheth the tweeter I use is "16 OHM or 8 OHM", correct?
And thank you for your response.

The bottom line is ;

- Once you add a 20 ohm load resistor across any of the 4 tested tweeters / and then stick an 8 ohm Lpad in front of that combo ( source side ) / your passive crossover elements ( L & C ) will be looking into an 8 ohm load, that almost looks like a straight-line .

[Mr. Widget]

So bottom line would be that it will make no difference wheth the tweeter I use is "16 OHM or 8 OHM", correct?
No, but it will make no difference if you use a JBL 077 or 2405 that is labeled 8 ohms or 16 ohms since they are all the same regardless of what has been printed on the back.

To design a proper passive network the impedance does matter. Other than the design of the network, the actual impedance of a tweeter has little importance.


- Once you add a 20 ohm load resistor across any of the 4 tested tweeters / and then stick an 8 ohm Lpad in front of that combo ( source side ) / your passive crossover elements ( L & C ) will be looking into an 8 ohm load, that almost looks like a straight-line .... or you can do that :) since these tweeters are so sensitive that tossing out a bit power isn't a big deal.


Widget

[duaneage]

Impedance of the tweeter has little effect, the only difference might be efficiency and that is easy to correct with Lpads or other methods.

Woofers and midranges are another story. Woofers can underload an amp if presented with a low impedance. Midranges are integrated into the crossover network more so the passband gain, filter Q, and final efficiency can be drastically altered by doubling or halving the impedance.

If there are Zobels, notch filters, or traps on the driver they may need to be recalculated since the filter action is usually based on driver impedance at a specific frequency.