Help! Soldering legs onto tweeter protection lamp (Sylvania 211-2)

[ecluser]

Would the wiring be like this? Bridge all three bulbs, then wire the bridge to the circuit board?

Yes

Or if I'm using the Ohms law calculator correctly, I'd need a 17W bulb to get the resistance to 8.6 Ohms, is that right? Should I actually look for a 17W 12V bulb? Or is there a specific bulb that folks are using in the TF600 and CX27?

Yes, 12V, 1.4A is a 12V,17W bulb. It's just two different ways to say the same. I don't know what they are using in the original cross-over. The spec (12V, 1.4A) is from you, in your post #18.

 

[cmayo]

Yes, 12V, 1.4A is a 12V,17W bulb. It's just two different ways to say the same. I don't know what they are using in the original cross-over. The spec (12V, 1.4A) is from you, in your post #18.

Hugely helpful, thank you. I never understood how/why to apply Ohm's Law before your post. I located and ordered some 12V 18W festoon bulbs that should take my R to 8 Ω; that's as close as I could get to 8.6 Ω with a single bulb. Can't wait to hear them!

 

[gadget73]

well, the resistance of a lamp isn't quite exactly like a standard resistor. In technical terms, it is a positive temperature coefficient resistor, which just means the resistance goes up as it gets hotter. With no current flow its going to be a lot less than 8 ohms, but as you push current through the tweeter, the lamp will get hotter and increase resistance up to 8 ohms when it hits full rated voltage. A too-low wattage lamp will start cutting current back too early and the tweeter will end up playing lower as a result.

Its actually a fairly good way of limiting current for extremely minimal cost. Its exactly the same as a dim bulb tester used for working on amplifiers and other potentially shorted electronics. The bulb limits current flow to whatever the bulb is rated for.

 

[ecluser]

Its actually a fairly good way of limiting current for extremely minimal cost. Its exactly the same as a dim bulb tester used for working on amplifiers and other potentially shorted electronics. The bulb limits current flow to whatever the bulb is rated for.

In my opinion it is not a good idea to introduce a non linear resistance in series with a speaker. It might be good for safety, but not for sound. If the original lamp is replaced by a lower wattage lamp, the lamp might burn because 12V is much lower than the output voltage of medium power amplifiers.

 

[gadget73]

Not ideal, but probably the most effective for the least effort and expense possible.

 

[cmayo]

well, the resistance of a lamp isn't quite exactly like a standard resistor. In technical terms, it is a positive temperature coefficient resistor, which just means the resistance goes up as it gets hotter. With no current flow its going to be a lot less than 8 ohms, but as you push current through the tweeter, the lamp will get hotter and increase resistance up to 8 ohms when it hits full rated voltage. A too-low wattage lamp will start cutting current back too early and the tweeter will end up playing lower as a result.

Its actually a fairly good way of limiting current for extremely minimal cost. Its exactly the same as a dim bulb tester used for working on amplifiers and other potentially shorted electronics. The bulb limits current flow to whatever the bulb is rated for.

Ah, thanks for the clarification. I replaced the bulbs on a pair of CX-27's and felt like the tweeters weren't loud enough... I was hoping the right bulbs would get a little more out of them.