# What will a tweeter do to the impedence?

Discussion in 'Amps and Cabs [BG]' started by Player, Aug 11, 2000.

1. ### Player

Dec 27, 1999
USA Cincinnati, OH
I was thinking about adding a Tweeter (x-over @ 2.5k)to my 2-10 cab. How will this effect the impedence of the cab? Can I use an 8 ohm horn with just a x-over cap? What if I use an L-pad? I want to keep the cab @ 8ohms. (I'm thinking I need to cover the 3k htz - 7k range, the 10s go to about 4k). I found one that says "No x-over needed" that's rated at 400w. It's over 1k ohm @ 1khz and over 20ohm @ 40khz. I'm running 2-4ohm 10s in series (8 ohm), if I paralell the tweeter what happens to the impedence of the cab? Any help would be greatly appreciated. Thanks.

2. ### Mo' bass

May 4, 2000
Netherlands
In my Trace Elliot manual it says I can safely add a Horn box to a speaker without worrying about the impedance. I think this is because the Horn box has a very high impedance compared to a 'normal' speaker.

Let's assume that the impedance of a horn = 1kOhm.
The formula for calculating the impedance of two speakers in parallel is 1/total = 1/spkr1 + 1/spkr2, so....
1/total=1/8 + 1/1000=125/1000 + 1/1000= 126/1000.

TOTAL= 1000/126 = 7,93. That's almost 8 Ohms, so no problem!
( if the horn had an impedance of 100 Ohm this numebr would be a little bit lower, but still nothing to worry about.)

3. ### Joris

Sorry for the delay, Paul, I've been busy.

Mo'bass is absolutely right.

I have to add this:

Nearly every horn has an 8 ohm impedance. Only a piezo crystal horn (the type you guys are talking about) are 1k ohms. They can be parallelled to any woofer without a crossover. However, adding a 33 ohms 5 watts resistor in series (with the horn only), for protection, is often recommended. A standard L-pad cannot be used, since they are designed to deal with an 8 ohms load.

I, for one, don't like piezo tweeters. They sound harsh and crispy, always too loud. I have found it worth the trouble of putting in a crossover, so I can use a electrodynamic (8 ohms) tweeter.

4. ### Player

Dec 27, 1999
USA Cincinnati, OH
Thanks Joris.
So if I use an 8 ohm X-over and an 8 ohm horn with an 8 ohm speaker load will the cab be 8 ohm?