A question about speaker Ohmage

John Bechtel · From: Nashville, Tennessee, R.I.P.

I'm not one to mess with a good thing very often, I'm just curious! I have a new '65 Reissue Fender Twin-Reverb Custom™ 15. I was reading old tips and secrets from the past in the archives. I read about adding a Tweeter to the existing speaker. Not knowing much about electronics, I'd just like to know for sure, to be safe; my 15” Eminence speaker is 4 0hm for this amp. If I want to add a Tweeter in a little box of it's own to sit on top of the Amp. cabinet and plug into the External Speaker-Jack of my Twin, what 0hmage would be a match? (I'm guessing another 4 0hm) According to the Owners Guide, both Speaker Jacks are 4 0hm. I just don't want to disturb the 15” efficiency.
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“Big John” Bechtel
Franklin PSG D–10 (9 & Cool

Fender ’49–’50 T–8 Custom
Fender ’65 Reissue Twin-Reverb Custom™ 15
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[This message was edited by John Bechtel on 17 April 2004 at 08:32 PM.]

[This message was edited by John Bechtel on 17 April 2004 at 08:34 PM.]

John Floyd · From: R.I.P.

Big John
You need a capacitor in Series with the Tweeter, a 4.0 mfd NP , (non polarized) capacitor should work fine to block the lows from getting to the tweeter and adding a tweeter in this manner shouldn't affect the overall impedance that much. You can experiment a little with capacitor values if it doesn't quite sound like you want, also you can use a 25 - 50 ohm wirewound pot to control the level of the tweeter.

Get up with Woody Woodell, About the best I guy I kmow around Nashburg to rig up something like this.

[This message was edited by John Floyd on 18 April 2004 at 12:22 AM.]

Ken Fox · From: Nashville GA USA

A piezo horn/tweeter needs no crossover. Its impedance is extremely high; therefore the amp sees virtually no load. However, be careful. The late 1970's Twins and Vibrasonics used a switching jack on the speakers to change taps and rewire the speakers in either parallel or series (different for each amp). I looked at the 1965 Reissue Twin and the Custom Vibrasonic schematics, they do this, and they are just parallel jacks. My best guess is this new amp is just other late 90 Vibrasonic. However to be safe, check the schematic or just parallel off the speaker itself, not the extension jack.
I have built two of these using piezo horns from Radio shack, they work quite well.

Bill Crook · From: Goodlettsville, TN , Spending my kid's inheritance

John.........

I agree with what Ken and John said.

If you need any help with doing this, call me.
Bill

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http://home.comcast.net/~crookwf/

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[This message was edited by Bill Crook on 18 April 2004 at 02:17 PM.]

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