# Blues Junior extension Cab



## knight_yyz (Mar 14, 2015)

Hey guys, does anyone know how this was done? I was thinking it would be nice to run the Blues Junior through a 2 x 12 cab, but getting one made isn't going to be cheap. I have checked out the MOJO site, as i would love to turn the BJR into a 2x12 combo but with shipping and exchange rate, I might as well buy a used 2x12 combo. LOL. 



I saw this by accident on Bill M's old website, but i can;t figure out how he did it. I think it looks great and it's probably the cheapest alternative to having a second 12" speaker. I've emailed him but it might take a while for him to get back to me depending on how busy he is and whether his health issues are resolved. 

Any way here's the pic I'm talking about....










The normal BJr is thicker at the bottom than the top, but the extension is the same thickness top and bottom, with a recessed handle so the upper combo sits flat. 

Anyone else know how this was done? I'm also curious because, if I remember ohms law correctly, two 8 ohm speakers will need an impedance of 4 ohms, so that is the part that has me messed up. So either he put a 16 ohm in each cabinet, or he somehow changed the impedance on the amp to 4 ohms for the 2x12 8 ohm speakers.


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## sulphur (Jun 2, 2011)

I found this thread, it looks like the same setup...http://www.tdpri.com/forum/amp-central-station/135877-my-fender-blues-jr-ext-speaker-cab.html

He said that he "Fendered up" an Epiphone Valve Junior extension cab.

As far as ohms, it should state what you need on the jack for the extension cab.

I run a Traynor YGL1 and a DHX112 cab with it, the speakers are not original though.



After lugging an eighty pound 2x12 combo for a few years, 
I now appreciate the 1x12 combo and the ext. cab.
Even grabbing the amp in one hand and the cab in the other is easier than one unit.

I find that the extension cab makes a big difference with the combo.


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## davetcan (Feb 27, 2006)

Here is a statement attributed to Bill M. I probably wouldn't do it though. I put my Pro Jnr into a head shell and i can now run it into a 1 x 12 or 2 x 12 cab. Either option sounds wayyyy better than the boxy little 10" cab it comes in.

http://www.harmonycentral.com/forum/forum/guitar/acapella-28/1674662-


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## sulphur (Jun 2, 2011)

Oh, there's no ext. jack for a cab?


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## davetcan (Feb 27, 2006)

sulphur said:


> Oh, there's no ext. jack for a cab?



No Sir! (stupid not enough letters rule)


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## greco (Jul 15, 2007)

davetcan said:


> Here is a statement attributed to Bill M. I probably wouldn't do it though.


Would you not do this because of the impedance mismatch or for another reason (or reasons)?
My curiosity again...sorry.

Your Pro Junior "conversion" to a head cab is very impressive!! 
Did you build the head cab yourself?

I am also a fan of using amp heads over combos as the ability to try various cabs, speakers, configurations, etc., etc. is a nice somewhat "unrestricted" feeling.

Cheers

Dave


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## GWN! (Nov 2, 2014)

sulphur said:


> Oh, there's no ext. jack for a cab?


On the Blues Jr there is no ext jack but the speaker is connected to the amp chassis via a jack. So it is fairly easy to unplug the internal speaker and a plug in an external cab.


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## davetcan (Feb 27, 2006)

Ohm mismatch only. He could, of course, put a 16 ohm speaker in the combo and another in the ext cab to get back to 8 ohms. At that point a Y cable might work.

The head cab was made by John (urko99) I believe. I got it in trade from him for something. It was unfinished so I just stained it black and popped the chassis into it. It weighs nothing and sounds great.



greco said:


> Would you not do this because of the impedance mismatch or for another reason (or reasons)?
> My curiosity again...sorry.
> 
> Your Pro Junior "conversion" to a head cab is very impressive!!
> ...


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## sulphur (Jun 2, 2011)

Would either of these work?

http://www.bhphotovideo.com/c/product/216447-REG/Hosa_Technology_YPP_118_1_4_Male_to_Two.html#!

http://www.musiciansfriend.com/acce...ogies-1-4-male-mono-to-two-1-4-female-adapter


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## davetcan (Feb 27, 2006)

Second one would, you don't need TRS, just mono 1/4. I'd still change the internal speaker if it were me though 



sulphur said:


> Would either of these work?
> 
> http://www.bhphotovideo.com/c/product/216447-REG/Hosa_Technology_YPP_118_1_4_Male_to_Two.html#!
> 
> http://www.musiciansfriend.com/acce...ogies-1-4-male-mono-to-two-1-4-female-adapter


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## sulphur (Jun 2, 2011)

I did what you had mentioned with my combo and extension cab Dave,
I'm pretty sure that the Webers were 16 ohms that I used as replacements.

It does make a difference when the cab isn't plugged in that way though.


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## GWN! (Nov 2, 2014)

sulphur said:


> Would either of these work?
> 
> http://www.bhphotovideo.com/c/product/216447-REG/Hosa_Technology_YPP_118_1_4_Male_to_Two.html#!
> 
> http://www.musiciansfriend.com/acce...ogies-1-4-male-mono-to-two-1-4-female-adapter


Most available Y cables are made with instrument cable and not speaker cable and therefore should not be used for cab connection. I would make my own using two wire speaker cable.


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## greco (Jul 15, 2007)

GWN! said:


> Most available Y cables are made with instrument cable and not speaker cable and therefore should not be used for cab connection. I would make my own using two wire speaker cable.


Excellent point!!!


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## sulphur (Jun 2, 2011)

GWN! said:


> Most available Y cables are made with instrument cable and not speaker cable and therefore should not be used for cab connection. I would make my own using two wire speaker cable.


When I did include "speaker cable" in the search it didn't come up with much.


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## GWN! (Nov 2, 2014)

sulphur said:


> When I did include "speaker cable" in the search it didn't come up with much.


You will not find too many. Here is one.

http://procablesnsound.com/items/speaker-y-cables/power-y-adapter-70001-detail.htm


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## davetcan (Feb 27, 2006)

GWN! said:


> Most available Y cables are made with instrument cable and not speaker cable and therefore should not be used for cab connection. I would make my own using two wire speaker cable.


Very good point, I went through a search for this awhile ago and didn't come up with much either.

- - - Updated - - -



GWN! said:


> You will not find too many. Here is one.
> 
> http://procablesnsound.com/items/speaker-y-cables/power-y-adapter-70001-detail.htm



Nice, I didn't find that one.

- - - Updated - - -



GWN! said:


> You will not find too many. Here is one.
> 
> http://procablesnsound.com/items/speaker-y-cables/power-y-adapter-70001-detail.htm



probably need this one for the Blues Jnr.

http://procablesnsound.com/items/speaker-y-cables/power-y-adapter-70002-detail.htm


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## knight_yyz (Mar 14, 2015)

edited, I posted a long winded piece then found the solution 5 minutes later... .


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## knight_yyz (Mar 14, 2015)

In post 2 of this thread sulphur posted a link to another site. I read Bill M's comments and he says this...

"Nice job! The Blues Junior will drive 4 ohms without problems; you can make up a Y connector or install an aux speaker jack in parallel. I do it all the time, as do many of my customers."

So I don't have to upgrade I just need to wire in an auxiliary jack


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## GWN! (Nov 2, 2014)

davetcan said:


> probably need this one for the Blues Jnr.
> 
> http://procablesnsound.com/items/speaker-y-cables/power-y-adapter-70002-detail.htm


Yes saw that one after and that one would save you from having to buy a separate speaker cable to go to the cab.


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## knight_yyz (Mar 14, 2015)

- - - Updated - - -



davetcan said:


> Second one would, you don't need TRS, just mono 1/4. I'd still change the internal speaker if it were me though


I have a Cannabis Rex in my BJr


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## knight_yyz (Mar 14, 2015)

I also found this statement from Bill M regarding the BJr on 4 ohms

OK, let me explain.

The output transformer's main job is to convert the impedance of the output tubes to the impedance of the speaker for maximum efficiency. When there's a mismatch, there's a reduction in efficiency. Most any tube amp can withstand a 100 percent mismatch, so an 8 ohm nominal rating can drive a 4 ohm load or a 16 without problems. One notable exception: don't try to go lower on amps with 2-ohm output.

When the impedance gets too high on a tube amp, you get the possibility of flyback--arcs that can damage the output transformer or the output tubes. The BJr and many other modern amps have anti-flyback diodes in the output circuit to short out these high-voltage pulses.

When the impedance gets too low, the tubes and output transformer run warm. But it takes a lot of current, like playing loud into a dead short, to damage either.

Fender used the stock Blues Junior chassis in the Two Tone, a big cabinet with a 10 and a 12, both 8 ohm speakers, connected in parallel, a 4 ohm load. 

I drive a second 8 ohm cab all the time from my Blues Juniors. So do many of my customers.


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## davetcan (Feb 27, 2006)

I was only concerned about the impedence ;-) C-Rex is a good speaker for that amp. As Bill has stated, most amps will handle 100% mismatch so running 4 ohms total should be fine. I was just saying I wouldn't feel comfortable doing it. I'm often overly cautious though ;-)



knight_yyz said:


> - - - Updated - - -
> 
> 
> 
> I have a Cannabis Rex in my BJr


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## jb welder (Sep 14, 2010)

Consider also that almost all the classic vintage Fender amps that have "ext. spkr" jacks get mismatched when those jacks are in use.
Lots of old Traynor's too.


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## knight_yyz (Mar 14, 2015)

I'm not going to worry too much. I dont crank anything to 10, the master stays at about 2 or 3 tops and I crank the volume to maybe 7 to really break it up. But now that I have my box of rock built I might not even have to crank that up. Holy crap the SHO half of the box of rock is insanely loud.


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