Use of Int/Ext Speaker Jacks on Deluxe Reverb?

[Mango Moon]

Can anyone help educate me on this topic of speaker impedance and the proper or intended use of the two (internal/external) speaker jacks on a '65 Reissue Deluxe Reverb?

The amp has one 8-ohm 'internal' speaker and two speaker jacks (one internal and one external); the manual indicates that they are wired in parallel with an Output Impedance of 8-ohms (both speaker jacks combined).

So here is what I'd like to know; can I safely unplug the lone 8-ohm 'internal' speaker, and instead, connect two external cabinets (8-ohms each) using both jacks? Or will this damage the amp somehow?

Thanx All! I apologize ahead-of-time for my ignorance.

[Mango Moon]

Say what?

Forty-two different people (viewers) don't know the answer to this question? Wow! I guess in relative terms, I'm not that ignorant after all. Go figure!

Anybody?

[Enzo]

Have you any idea how many of those "viewers" are NOT people? Look sometime at the online now numbers. WHen you see 50 members and 500 guests, you can count on the majority of those "guests" being robots. Google and other things regularly scan. That is why you can start a thread here, and in a couple days google the topic, and there the thread will be.

Your amp has no idea where the speaker is. If you want to unplug the internal speaker and plug some extrenal cab in its place, go ahead. Just always use the internal jack first. Never use the external jack alone.

[Mango Moon]

Thanks Enzo, I appreciate your time and effort, but I'm afraid this hasn't answered the question.

Can both jacks (the internal and external) be used simultaneously with two (8-ohm) speakers, one external speaker connected to each jack? In other words, can the amp drive two speakers at the same time?

That's it! That's all I'm after.

[Enzo]

Can you use a 4 ohm load on the amp? (Two 8 ohm speakers in parallel)

Sure.

Are you supposed to?

No.

Is it going to hurt the amp?

No.

[Mango Moon]

O.K., so then what is the intended use of the 'external' speaker jack? In other words, why bother having two jacks?

If you're not "supposed" to use both jacks simultaneously, and you've plugged an external 8-ohm speaker into the external speaker jack, then according to what you've said here, by design, Fender intended you to unplug the internal speaker. Correct? At which point, you could have used either jack for an 8-ohm. So why bother having two jacks at all?

Maybe its clear to you, but something is still missing here for me, and that's precisely why my original post asked for an education on impedance.

[DirtyGeorge]

If you are unplugging the internal 8 ohm speaker then you could plug in two 16 ohm cabs (one in each jack). That would keep the correct load on the amp.

Or, if you don't have two 16 ohm cabs, you could use two 8 ohm speakers (one could be the internal speaker) for a 4 ohm load. That would be an impedance mismatch but as Enzo says, it won't hurt anything.

[mottaz]

The owners manual says:

E. INTERNAL SPEAKER JACK - Plug-in connection for the 8Ω internal speaker. A speaker must always be connected at this jack when the amplifier is ON. A
speaker impedance load of 8Ω should be used to avoid distortion or damage to the amplifier.

EXTERNAL SPEAKER JACK - Plug-in connection for an external speaker. This jack is wired in parallel with the INTERNAL SPEAKER JACK {E} and affects the speaker impedance load.

Some amps encourage you to play with speaker load. They sound/behave differently if there is a mis-match. They are robust enough to not worry about it. It's usualy a 4/8 8/16 mismatch, not 16/2 ohm difference. Fender is not endorsing this at all.

http://www.fender.com/support/manual...uxe_Reverb.pdf

[Richard]

How does an impedance mismatch alter the tone of an amp and affect headroom/output? There seems to be a lot of incomplete and contradictory information out there.

[dwhutchens]

I vote that it was a marketing ploy. Seems it's as worth about as much as the teats on a boar hog I didn't bother putting one on my amp. If the main jack is a shorting jack like the diagram shows and you leave it unplugged you won't get any sound out of the other jack and you'll probably stress the tubes and OT.

[Mango Moon]

Thanks to Enzo, George and everyone else who has responded here. I'm grateful.

This discussion has helped out a lot and I think I'm relatively clear on it now. Another respondent to the same question posted elsewhere stated the following . . . "Most Fender tube amps will tolerate a 2:1 mismatch of the output impedance. If you plug an external 8-ohm cabinet into the amp you'll have 4 ohms and it'll work fine. If you lug in a pair of external 8-ohm cabinets you'll be fine as well. Just don't try to run it with nothing plugged into the internal speaker jack."

So, the bottom line is, I can safely run a pair of external cabs that I have here, loaded with 8-ohm Celestion Blues, or alternatively, a pair of external cabs loaded with 8-ohm EVM-12Ls from this Fender DRRI amp, using the two (parallel-wired) Internal and External speaker jacks simultaneously (one speaker in each jack), without causing damage, and that's what I needed to know.

Thanks again everyone.