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Hi all. Years ago I bought (almost for nothing) a very old dilapidated Fender Twin blackface. I think it's an old 68. The pre- and power amp sections are still original although the valves don't work anymore. The speakers have been changed unfortunately and they are really crappy.
The idea was to restore the amp to its former glory, but since buying it I have realised that 100 Watts are way to loud for me to use the amp for practice or for most venues that I play. The second issue I have is the weight of this beast. My chiropractor loves it though!!

Since it is gathering dust in the garage I decided to make use of it and convert it into an extension cab for my Super Champ XD. I want to remove the power amp and simply fit two decent 12 inch speakers.
The Super Champ XD has a 15 Watt power rating at 8 Ohms.

My questions are the following:
1. If I want to fit two 12 inch speakers what should the Ohms and Wattage be to fit the output of the Super Champ XD?
2. Which speakers would you recommend? I have read around the forum that Greenbacks, Vintage 30's Jensen C12's and Celestions GK12's are all popular choices depending on the sound you want. I am looking for a really good fenderish clean sound that must carry overdrive well. I use stomp boxes for overdrives.
3. Connection from the Super Champ to the extension cabinet: Is it a simple Y chord? Can the speaker Super Champ play through its own 10 inch speaker while going through the extension cab as well, or is it either one or the other?

All info will be appreciated.
    I wouldn't convert a Blackface. Probably better to sell (or restore and sell) and buy yourself a cab.
      Hi Alan, thanks for the reply. I will take your advice. Since I have the opportunity to learn something here I would like to know why it is a bad idea to convert a twin? Is it because of the dimensions, the build or just the plain impracticality? It made sense to me because it fits two 12 inch speakers already and the open back should not be a problem.
        I'm no expert in collectable amps, but here's my take on it - hopefully some of the guys who are into vintage and collectibles will chip in:

        It's a damn nice amp and pretty collectible (although not quite at the point where it's really valuable ...yet). Restore it and it's value will only increase over the next 10 years or so. A quick eBay search tells me it's currently worth about $1,800 - $2,000, but the Blackface models from just a year or two earlier are going for $3,500 - and there is no difference between them (AFAIK) other than who owned the company.

        On the other hand, a 2X12 cab is relatively cheap and common. Worst comes to the worst, I'm sure you could easily find someone who would be willing to swap your "fixer-upper" for a new cab with speakers of your choice.
          Alan, thanks for the effort. I will phone my local music shops to get quotes on a 2 x 12 cab. The statement of the vintage value is true, but then it applies to someone who has the knowledge, patience and time to really do a good job of fixing it up - I have none of the 3 unfortunately.
          Anyone who wants to get rid of a cab?
            Anyone who wants to get rid of a cab?
            Y'know... I need a big amp like I need another guitar (OK - bad example), but A fixer upper might be worth me fixing up and swapping/selling it for something more up my street like a PRRI.
              Hi Werner

              The idea of driving 2 X 12" with a champ is an interesting project. Some tips:

              1. You are going to have to use either the internal speaker (typically 4 Ohm 8 watt) or the external speaker. Both together would probably sound feint and muffled.

              2. Doing two 12" increases their efficiency above a single driver (I think 6 dB increase - where's the technical guys?). So probably very pleasant, but (and there is usually a but :-[) you need hi sensitivity speakers. The higher the SPL rating (100dB / watt should be very nice ?) the better your sound. Also try to get a 4 Ohm combination. The 6V6GT wants to see 5000 ohms load. If you plug in a 8 ohm load - the reflected load doubles up to 10 000 ohms (still in spec for a 6V6GT), but the tone is cleaner (mind you; you might like it ?. 16 ohms speaker load probably a bad idea :-\

              3. Consider partly closing the back of the cab for better bass response. Leave hole as big as the piston area of the 12" doubled (or leave an option to tune the cab). Look at the rear of old tweed bassman etc. cabs. for ideas.
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