Fender Princeton ----> Twin

[Axtman]

I will measure and get back to you.

I uses 5U4 rectifier tube.

[Helmholtz]

I uses 5U4 rectifier tube.

Some Princetons came with the more efficient GZ34, which gives around 2W more output.

[Chuck H]

IMHE the Oxfords are less efficient than the Jensen speakers. Though they sound just fine. And I don't expect any speaker breakup is involved with the headroom issue for the amp. Though speaker efficiency can still make a difference.

I've never modded a Princeton for a bigger speaker but I have done three Champs. All the SF amps I've seen had glued baffles so there may be no way to do it without permanently changing the cabinet. But if your crustomer is bent on making an improvement with a speaker then a 12" is the way to go. An option might be to build a 1x12 cabinet that he can plug the amp into! It's an extra cabinet to drag around but as I guess the Oxford at something under 95dB sensitivity, there are 12" speakers boasting as much as 103dB, not to mention the option to tune the cabinet, this is the best option for increasing volume without destroying the Princeton. Plug the amp into a purpose made 1X12 tuned cabinet loaded with an efficient speaker for extra volume circumstances. Then use the Princeton as stock for home practice and recording. This doesn't need to be complicated.

EDIT: Assuming the stock Oxford at, say, 94dB (?), a 103dB 12" in a tuned cabinet would, in theory, increase output over the stock cabinet as if the amps wattage was raised from 13-ish watts to 52 watts! Now that's not real world experience but that's the actual theory. My point is that the difference could still be significant if done right. Take that stupid ten inch Celestion and sell it on *bay. It's not helping matters.

[Axtman]

I may never work on anyone's tube amp again. I typically buy a broken amp for cheap or free, repair it myself, and sell it. The nice thing about that is the customer either likes it or not. There are no mods or "cork sniffing".

The nice thing about solid-state amps is they either work or not. There are few mods to be done to them.

I also tend to work on more bass amps which means clean headroom. There is no arguing over which distortion sounds best.

One of these days I might build a Princeton clone. If I do I will upgrade the transformer and put it in a cabinet with a 12-inch speaker hole.

[Chuck H]

Follow up on my post above... I just did a bunch of speaker comparison listening on *outube. I was listening specifically to some Celestions and Jensens compared to the Eminence speakers that are over 100dB and I think the Cannabis Rex would be a good choice. The Eminence Governor and Wizard speakers are the most efficient but I never liked the sound of them. The Cannabis Rex comes in at 101.8dB and sounds great. I couldn't find any Oxford comparisons though. The Cannabis Rex sounded the most like the Jensens. I had one of these speakers in my own amp for a time and it sounded great. I took it out to demo a V30. I intended to put the Cannabis Rex back in but somehow it had gone missing. So the V30 is still in my amp and sounds just fine after breaking in so I haven't troubled to buy another Cannabis Rex yet.

So this is the speaker "I" would suggest for a cabinet to plug the Princeton into. JM2C and YMMV

EDIT: Ok, this is interesting. Fender put out an amp they called the '65 Princeton Reverb Tweed 12. And what speaker did they choose for OEM in this amp? The Eminence Cannabis Rex. I think it's funny that me and Fender came to the same conclusion. There are Demos on *outube.

[Helmholtz]

...and 6dB higher efficiency corresponds to 4 times power.

[Axtman]

The customer dropped off the Celestion Greenback G10 speaker two days ago. I put it in last night.

Wow! There is definitely a difference! The amp is now louder and I can feel it moving more air. That puny Oxford speaker could not hold up to the fully functional amp. I am surprised because the speaker was professionally reconed to the original specifications.

That said there is still some distortion I am dealing with. See the new thread on Positive Cycle Clipping.

The amp puts out about 10.5 volts with a 8 ohm speaker so about 13.8 watts of power before clipping.

[Chuck H]

The amp puts out about 10.5 volts with a 8 ohm speaker so about 13.8 watts of power before clipping.

That's pretty good for a Princeton actually. You need to step to the questions on the new thread. Is the amp clipping unevenly at the output??? This question would be for the other thread. And...

The Celestion being only 95dB sensitivity IMAGINE how well you could do with a dedicated cabinet and a 12" Cannabis Rex at 101.8dB. It would probably blow your mind. I don't know a lot about Oxford speakers but I've always gotten the impression they are pitifully inefficient. And there may be some additional detriment that came with the recone. Impossible to say really.