Need help: ...... Ribbon tweeters !!!

Mrpong

Member
2004-08-30 11:14 am
Bangkok
Hello

Recently I got a new pair of Aurum Cantus G2i, , not G2si. Here are my questions:-

I used a digital multimeter to check impedance of each tweeter. The meter said 0.3 ohm approximately and 0.2 nF capacitance.
- Why is its impedance so low? Is it not 4 ohm, 6 ohm or 8 ohm?
- Does anybody know the difference between G2i and G2si?

Thank you so much
 
A ribbon tweeter usually has a transformer to increase the impedance seem by the amplifier. The ribbon diaphragm is only a piece of aluminium so the resistance is very low. Only with very long ribbons are the resistance higher and don't need a transformer. On the Aurum Cantus website the technical drawings do show a transformer attached to the rear of the tweeter, so I am not sure why yours would measure so low. OTOH, the impedance is indicated as 8 Ohm, but that would be in the ribbon's frequency bandwidth. What you measured was their DC impedance (i.e. their impedance at 0Hz), which might be very low. I do think however that when use with a suitable cross-over, they should be fine. Have a look however at the drawings on the website and see if yours are similar. Here's the address:
Aurum Cantus G2 Aluminum Ribbon Tweeter
Their main website address is:
Aurum Cantus
I also added the drawing for the G2 rectagular ribbon below (note the block the binding posts are attached to- that is the transformer).

Enjoy,
Deon

[IMGDEAD]http://www.aurumcantus.com/g2g3/images/G21.gif[/IMGDEAD]
 
The multimeter measures DC resistance and the ribon element being a short piece of aluminum strip has essentially the same resistance as that of a small piece of wire. DC resistance is only part of the total imedance, mathematicaly the complex sum of resistance, iductive resistance and capacitive resistance. Dynamic speaker drivers exhibit inductive resistance in addition to DC Re due the voice coil (in general capacitive Re is negligible).

As mentioned above the tranformer acts as the impedance matching device in a ribbon and since it's essentially a coil, the form of resistance that an amp see's is that of inductive inducive resistance.