Wiring a speaker cabinet 1/4 inch jack

jman72

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Hi everyone,

This is a simple question (and I've done some research) but just wanted to check before I hook things up. I have converted my '77 Pro Reverb to a head and a 2x12 speaker cab. I want to use a 1/4 inch speaker cable to connect the speaker output of my amp to my speaker cabinet. I'm going to use a Switchcraft mono jack (attached to the speaker cab by an L-bracket) and just wire it up to my speakers in parallel as shown here:

Speaker Jack Wiring 1.jpg


Should this work fine? The positive (shown in red) is connected to the jack tip, while the negative (black) is connected to the jack ground? I can just plug in a 1/4 speaker cable between the amp output and this speaker jack and all should be fine? Any suggestions or comments? Thanks!
 

jman72

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That looks good, just watch your impedance.
Thanks for the input. When you say to watch my impedance, you mean to make sure that my speaker impedance (as wired) matches my OT for my amp? The OT for the Pro Reverb is matched for a 4 ohm load, so the two 8 ohm speakers wired in parallel should give me the 4 ohm impediance.
 

JustABluesGuy

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Thanks for the input. When you say to watch my impedance, you mean to make sure that my speaker impedance (as wired) matches my OT for my amp? The OT for the Pro Reverb is matched for a 4 ohm load, so the two 8 ohm speakers wired in parallel should give me the 4 ohm impediance.

Exactly. It sounds like you have a handle on it.
 

DougM

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As pictured in your wiring diagram if those two speakers were 16ohm each the cab would end up being 8ohm right?
Correct. Two speakers with the same impedance in parallel will be half the value of each, while in series it will be double the value of each. Combining speakers that aren't the same impedance in parallel is trickier and requires a calculator. In series though you just add the two together to get the total. So, an 8 and a 4 in series will be 12, but an 8 and 4 in parallel is 2.7.
 
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Chunkocaster

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Correct. Two speakers with the same impedance in parallel will be half the value of each, while in series it will be double the value of each. Combining speakers that aren't the same impedance is trickier and requires a calculator.

Great, thanks. What do you end up with if you use one 8ohm speaker and one 16ohm speaker combined as above? Is there a way to combine the 8 and 16 to get a 8ohm or 16ohm cab?
 

Chunkocaster

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I used to have exactly such an Ohm calculator app for iPhone, but it quit working with a past iOS upgrade.

I found a online calculator and apparently if you run two 16ohm speakers in parallel and one 8 ohm in series with those you get 16ohm. Makes sense seing as the two 16ohms are converted to 8 by running them parallel. Unfortunate for me I was interested in mixing ohms for a 8ohm amp.

http://www.speakerimpedance.co.uk/?act=three_series_parallel&page=calculator
 




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