how to wire up external speaker for amp and using it

[drew571]

This is basic.  I know.  And I think I know what I'm doing but wanted to make sure.

I just built an ISO cabinet for an external speaker for my 68 Fender Reissue Deluxe Reverb amp.  I purchased the exact same speaker that's in my guitar amp cab which is a 12" Celestion® G12V-70 8 ohm speaker.  The internal speaker cable coming out of the amp is an unbalanced 1/4" cable.

I'm guessing that the Tip goes to positive and the Sleeve goes to Negative?  Just wanted to make sure before I possibly messed something up. 

Thanks!

 

[pucho812]

tip is  (hot) +, etc

Sleve is  ground


I can't think of a situation that would require it to be reversed.

 

[Winetree]

Yes, correct hookup,
speaker cable is unbalanced, should be 2 conductor,
not using a braided shield as the negitive.

 

[drew571]

so this would be slightly different from your normal guitar cable then, correct?  would it be ok to use a microphone cable and then just not use the braided ground?  just the two insulated cables inside?

 

[Winetree]

No, you need to use 12 or 14 guage wire.
You could use lamp cord or a good speaker wire.

 

[PRR]

Microphone is several hundred ohms. A few ohms of wire resistance does no harm.

Speaker is a few ohms. A few ohms of wire resistance splits-off half the power.

Also your wire is longer than you have in a combo or cab-on-head. A combo's internal wiring may be a really small fraction of an ohm, but a longer wire is already more ohms and you want to keep the added ohms low.

The other thing is that shielded wire has lots of capacitance and *some* amplifiers do not like that. I doubt a 1960s DeLuxe would even notice, but it is generally bad-habit to use shielded wire on speakers.

On a speaker, + and - are often arbitrary. Nothing horrible will happen if you connect it the other way (this isn't car-radio power). Absolute Phase is just-maybe-barely audible. In a multi-speaker array (or in Stereo) you want them all the same so they don't cancel each other. Arguably some guitar-tones will sound different one way or the other, though particularly free in a room not closed in a box. Obviously you might take care to phase the iso speaker the same as the cab speaker.

If you are taking a mix of direct and speaker, there's always a phase issue (Murphy's Law). Your mixer has a switch for flipping phase of each channel. You can never put a pickup and a speaker+mike *IN* phase, but you can reduce or shift the comb-filter so it does not spoil the music.

 

[Giggity]

Check to see if the speaker jack is wired for parallel or series.  If parallel, it will put a 4ohm (nominal) load on the amp and it may not be able to handle that.  If series, it will be 16 ohm load and no problem.

 

[joaquins]

Check to see if the speaker jack is wired for parallel or series.  If parallel, it will put a 4ohm (nominal) load on the amp and it may not be able to handle that.  If series, it will be 16 ohm load and no problem.

Normaly it would disconnect the speaker in the cab, and he get the exact same speaker as the one in the cab, I guess same impedance, so no problem, plus, why someone would want an iso cab and leave connected the speaker outside it?

JS

 

[drew571]

Thanks for the answers.  Yes, I'll be disconnecting the internal speaker so I can get the amp up to volume without disturbing the kids.  I've got some thicker gauge speaker wire laying around so ill use that!  Can't wait to fire this baby up. 

 

[Giggity]

Check to see if the speaker jack is wired for parallel or series.  If parallel, it will put a 4ohm (nominal) load on the amp and it may not be able to handle that.  If series, it will be 16 ohm load and no problem.

Normaly it would disconnect the speaker in the cab, and he get the exact same speaker as the one in the cab, I guess same impedance, so no problem, plus, why someone would want an iso cab and leave connected the speaker outside it?

JS

Normally, absolutely  true.  And most do but, still wouldn't hurt to check, given the consequences.

Just push a T/S plug into the ext. jack and see.  Takes about 5 seconds.

Hey....My first post.  Just being cautious and trying to help what I can. 

 

[CJ]

you can check speaker polarity with a 9 V battery,

connect the + of the battery to the + of the speaker and see which way the cone goes,

some of the old speakers had the polarity flipped but most are the same nowadays,

also Marshall and Fender play out of phase with each other so if you ever Y cord your way into USA + UK sound, you need to flip the speaks on one or the other, i would pick the Fender as it is easier to get into the cabinet,

 

[joaquins]

Check to see if the speaker jack is wired for parallel or series.  If parallel, it will put a 4ohm (nominal) load on the amp and it may not be able to handle that.  If series, it will be 16 ohm load and no problem.

Normaly it would disconnect the speaker in the cab, and he get the exact same speaker as the one in the cab, I guess same impedance, so no problem, plus, why someone would want an iso cab and leave connected the speaker outside it?

JS

Normally, absolutely  true.  And most do but, still wouldn't hurt to check, given the consequences.

Just push a T/S plug into the ext. jack and see.  Takes about 5 seconds.

Hey....My first post.  Just being cautious and trying to help what I can. 

I didn't notice that it was your first post, sorry! and welcome!

The consequences aren't so bad, since a miss match on impedance for an old design is not a big problem, you would not burn your amplifier, in fact some tube amps user manuals recommend trying mismatching impedance at the speakers in order to get different response. Also another thing to have in mind is that tube power amps don't have problems when overloaded, the problem is when unloaded because the voltage in the transformer travels anywhere (really high voltages) and that can bur out your tubes. If low impedance load is connected it will run into saturation because of current and nothing really bad will occur since anode resistance, at least if connected for a short time, 4Ω still fine for not so short time, a short circuit may get your tubes little red, but you'll probably notice that before burning anything and even more if you are DIYing something.

JS

 

[drew571]

you can check speaker polarity with a 9 V battery,

connect the + of the battery to the + of the speaker and see which way the cone goes,

some of the old speakers had the polarity flipped but most are the same nowadays,

also Marshall and Fender play out of phase with each other so if you ever Y cord your way into USA + UK sound, you need to flip the speaks on one or the other, i would pick the Fender as it is easier to get into the cabinet,

Very interesting to know.  Thanks guys. Very informative.