fenders and extension speaker wisdom

skeksis · January 11th, 2008, 12:14 PM

looking for advice on running an extra speaker with my older Princeton Reverb... there's internal and external jacks on the back of the amp, and it's target load is 8 ohms. what's the conventional wisdom on this?

I've seen it somewhere that a 'rule of thumb' is to not exceed by 2x or 0.5x the intended speaker load for a small amp like this...

so, by that reasoning, I could plug an 8ohm extention AND keep the internal speaker plugged in? I try to be pretty careful about these things, and have always unplugged the internal when using external speakers to keep the total resistance right.

am I too paranoid, or is a 'better safe than sorry' approach warranted in this case?

BoB/335 · January 11th, 2008, 12:35 PM

I see this question from time to time and I don't see a real answer from the point of an amp company. I have 3 vintage Fender Amps that Have a speaker jack and an extention speaker jack. If Fender only wanted one speaker hooked up at a time I would think there would only be ONE jack.
I would make sure that the speakers (or total cab) are the same ohms as what is in the amp.
My Princeton Reverb has one 8ohm speaker. Therefore I will only plug an 8ohm load into the extention jack while using the internal speaker.
My Twin Reverb and Pro reverb both have 2-12" 8ohm speakers = a 4ohm load. Therefore I will only 2 4ohm load into the extention speaker jack.

That's just my opinion.

6942 · January 11th, 2008, 12:45 PM

8 ohm amp = (1)8 ohm speaker
= (2) 16 ohm speakers in parallel
= (2) 4 ohm speakers in series

If you DO NOT want to blow up your amp....please remember this.

Steve

Paul G. · January 11th, 2008, 02:41 PM

Fender amps are pretty good with impedance mismatches.

You can safely run an 8-ohm Fender (like your Princeton) with a 4-ohm load.

So plug in an 8-ohm extension cab with your internal connected and have at it.

The jacks are wired in parallel so you will see a 4-ohm load.

P.

BoB/335 · January 11th, 2008, 05:49 PM

Quote:

Fender amps are pretty good with impedance mismatches.

That's the line I read over and over and over. Is it REALLY a mismatch if the amp was DESIGNED for a speaker PLUS an extention speaker? To me THAT is the REAL question and no one seems to answer that or point to a reliable source with an answer in writing.

nonvintage · January 11th, 2008, 06:24 PM

I run an 8 ohm 15" Alnico with my SFPR and the only problem I had with it was that it had volume cutting in and out going from loud to soft. It revealed a bad phase inverter preamp tube. Since replacing that I've had no problems.

Dacious · January 11th, 2008, 06:37 PM

Older Fenders will cope with it OK - but it's like towing things with your car. There is an impedance mismatch which has some effect on the operation of the amp. You will maybe wear tubes a bit faster. Maybe I'd be a bit more careful with a Deluxe Reverb than a Princeton because the tubes are already being buzzed pretty hard in the DR compared to the PR.

Just like you wouldn't overly abuse you car by revving it too hard or trying to accelerate or brake like it was unloaded when towing a heavy load, running your amp dimed with the output mismatch and a tubescreamer in the front is probably not a smart thing.

OTOH, some amps are notorious for not tolerating this well. I would personallly not run a Vox AC amp or any era with a mismatched output load because they are a bit more fragile. And I'd be wary of Marshalls, too, if running them hard.

T_red7882 · January 11th, 2008, 06:56 PM

I don't get this... anyone wanna explain it for us who aren't proficient with loads and such...?

sector9 · January 11th, 2008, 07:17 PM

Quote:

Originally Posted by T_red7882

I don't get this... anyone wanna explain it for us who aren't proficient with loads and such...?

A princeton reverb output transformer runs at 8 ohms, it can handle a mismatch of no higher than twice and no lower than half of its expected 8 ohm speaker load.

You can run it with a 16 ohm load or a 4 ohm load or anywhere in between. If you want to use 2 speakers all the time
the ideal setup would be a 16 ohm speaker in the amp and a 16 ohm ext. speaker cab = 8 ohms

Dacious · January 11th, 2008, 07:34 PM

If you want it simple, the amp will be happiest working how the manufacturer set it up.

You might think it 'sounds' better mismatched. It may. But that's not how the maker intended it. Some amps won't tolerate that well.

Speakers paralleled which is what most extension plugs do, will be half their original impedance if both the same. So two 8 ohm speakers will equal 4 ohms plugged in together.

If your Fender wants to see 8 ohms (Princeton, Deluxe Reverb) then plugging a second 8 ohm speaker in is OK. Fender designed it like that. If your Fender wants to see 4 ohms (Vibrolux, Pro, Twin, some others) then plugging in a 4 ohm extension will give you 2 ohms total together with the original speakers and that is OK.

If you have a 4 ohm extension cab you want to use with an 8 ohm Princeton or Deluxe, unplug the internal speaker and plug in the extension to the internal speaker jack.

Never leave the internal speaker jack on a Fender with no speaker plugged in, even if you have a speaker load in the extension. It is a shorting jack and with nothing in it represents a dead short or zero load; which will kill your output transformer if you run it long like that.

BoB/335 · January 11th, 2008, 07:38 PM

Quote:

If you want to use 2 speakers all the time the ideal setup would be a 16 ohm speaker in the amp and a 16 ohm ext. speaker cab = 8 ohms

Which still doesn't make sense to me why there would be an extention jack while the manufacturer already has a matched load.

Well I just did some research and found a '65 Twin Reverb Re-issue Manual and it is interesting to see what it says.

E. MAIN SPEAKER JACK- Plug-in connection for speakers. This jack must always be used as the primary connection to speakers.
F. EXTERNAL SPEAKER JACK- Plug-in connection for an external speaker. This jack is wired in parallel with the MAIN SPEAKER JACK, and must only be used in conjunction with the MAIN SPEAKER JACK. Should the EXTERNAL SPEAKER JACK be used without also using the MAIN SPEAKER JACK, there will be no sound. Note that the amplifier is optimized for a 4 ohm speaker load, and that the speakers in the cabinet are wired for 4 ohms. Should a total load of more or less than 4 ohms be used, the amplifier will not put out its maximum power output before distortion occurs.

I guess that about says it all.

And here is from a '65 Re-issue Deluxe Reverb Manual

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.
F. 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.

In my 40 years of playing I have barely tried another speaker load. I ususally used my Twin and having 2-12's was plenty. I have told the story of trying a DRRI and ended up with a '69 Pro Reverb with 2-12's. I really think the extra speaker makes a huge difference in the sound. As I get older I am always concerned of the weight factor and in the back of my mind always consider giving the Deluxe another shot someday and probably having a matching extention cab to continue getting that 2-12 sound I love so much. The info above has only given me ANOTHER reason to give the Jensen Neos a shot to lighten this load just a little because NOW I can't ever see going smaller. (and btw I also have a '69 Princeton Reverb that doesn't see as much play time as my Pro. AND I'm not talking volume here)

dadm · January 13th, 2008, 07:19 AM

I had a '68 princeton reverb years ago. it sounded beautiful but the drummer
was too loud for it. Didn't have a good P.A. I used a 12'' 8 ohm along with the factory 10'', an LPB-1 power booster and played it wide open every night
for a year. Never wrecked it but it always sounded best on about half without
the extra stuff plugged in.

BoB/335 · January 13th, 2008, 07:30 AM

I thought there would have been a lot of comments on the Fender Manual info.

dadm · January 13th, 2008, 07:33 AM

I had a '68 princeton reverb years ago. it sounded beautiful but the drummer
was too loud for it. Didn't have a good P.A. I used a 12'' 8 ohm along with the factory 10'', an LPB-1 power booster and played it wide open every night
for a year. Never wrecked it but it always sounded best on about half without
the extra stuff plugged in.

January 11th, 2008, 12:14 PM	#1 (permalink)
skeksis Tele-Meister Join Date: Dec 2007 Location: phoenix Age: 30 Posts: 228	fenders and extension speaker wisdom looking for advice on running an extra speaker with my older Princeton Reverb... there's internal and external jacks on the back of the amp, and it's target load is 8 ohms. what's the conventional wisdom on this? I've seen it somewhere that a 'rule of thumb' is to not exceed by 2x or 0.5x the intended speaker load for a small amp like this... so, by that reasoning, I could plug an 8ohm extention AND keep the internal speaker plugged in? I try to be pretty careful about these things, and have always unplugged the internal when using external speakers to keep the total resistance right. am I too paranoid, or is a 'better safe than sorry' approach warranted in this case? __________________ '86 mij '62 Custom Tele ----> '08 Marsh 5F4 Super kit or 60's Silvertone guitars (Harmony-made) ----> '66 Princeton Reverb http://www.myspace.com/jswattsmusic

January 11th, 2008, 12:35 PM	#2 (permalink)
BoB/335 Tele-Meister Join Date: Aug 2003 Location: Long Island Posts: 473	I see this question from time to time and I don't see a real answer from the point of an amp company. I have 3 vintage Fender Amps that Have a speaker jack and an extention speaker jack. If Fender only wanted one speaker hooked up at a time I would think there would only be ONE jack. I would make sure that the speakers (or total cab) are the same ohms as what is in the amp. My Princeton Reverb has one 8ohm speaker. Therefore I will only plug an 8ohm load into the extention jack while using the internal speaker. My Twin Reverb and Pro reverb both have 2-12" 8ohm speakers = a 4ohm load. Therefore I will only 2 4ohm load into the extention speaker jack. That's just my opinion. __________________ BoB/335

January 11th, 2008, 02:41 PM	#4 (permalink)
Paul G. Tele-Holic Join Date: Mar 2003 Location: Rhode Island Posts: 885	Fender amps are pretty good with impedance mismatches. You can safely run an 8-ohm Fender (like your Princeton) with a 4-ohm load. So plug in an 8-ohm extension cab with your internal connected and have at it. The jacks are wired in parallel so you will see a 4-ohm load. P. __________________ Listen to your mother

January 11th, 2008, 06:37 PM	#7 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,610 35 Photos	Older Fenders will cope with it OK - but it's like towing things with your car. There is an impedance mismatch which has some effect on the operation of the amp. You will maybe wear tubes a bit faster. Maybe I'd be a bit more careful with a Deluxe Reverb than a Princeton because the tubes are already being buzzed pretty hard in the DR compared to the PR. Just like you wouldn't overly abuse you car by revving it too hard or trying to accelerate or brake like it was unloaded when towing a heavy load, running your amp dimed with the output mismatch and a tubescreamer in the front is probably not a smart thing. OTOH, some amps are notorious for not tolerating this well. I would personallly not run a Vox AC amp or any era with a mismatched output load because they are a bit more fragile. And I'd be wary of Marshalls, too, if running them hard. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

January 11th, 2008, 07:34 PM	#10 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,610 35 Photos	If you want it simple, the amp will be happiest working how the manufacturer set it up. You might think it 'sounds' better mismatched. It may. But that's not how the maker intended it. Some amps won't tolerate that well. Speakers paralleled which is what most extension plugs do, will be half their original impedance if both the same. So two 8 ohm speakers will equal 4 ohms plugged in together. If your Fender wants to see 8 ohms (Princeton, Deluxe Reverb) then plugging a second 8 ohm speaker in is OK. Fender designed it like that. If your Fender wants to see 4 ohms (Vibrolux, Pro, Twin, some others) then plugging in a 4 ohm extension will give you 2 ohms total together with the original speakers and that is OK. If you have a 4 ohm extension cab you want to use with an 8 ohm Princeton or Deluxe, unplug the internal speaker and plug in the extension to the internal speaker jack. Never leave the internal speaker jack on a Fender with no speaker plugged in, even if you have a speaker load in the extension. It is a shorting jack and with nothing in it represents a dead short or zero load; which will kill your output transformer if you run it long like that. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

January 11th, 2008, 12:45 PM	#3 (permalink)
6942 Tele-Afflicted Join Date: Apr 2006 Location: Western Maryland Posts: 1,437	8 ohm amp = (1)8 ohm speaker = (2) 16 ohm speakers in parallel = (2) 4 ohm speakers in series If you DO NOT want to blow up your amp....please remember this. Steve

January 11th, 2008, 06:24 PM	#6 (permalink)
nonvintage Tele-Meister Join Date: Mar 2006 Location: San Diego Posts: 464	I run an 8 ohm 15" Alnico with my SFPR and the only problem I had with it was that it had volume cutting in and out going from loud to soft. It revealed a bad phase inverter preamp tube. Since replacing that I've had no problems.

January 11th, 2008, 06:56 PM	#8 (permalink)
T_red7882 Tele-Holic Join Date: Dec 2006 Location: San Francisco Age: 26 Posts: 622	I don't get this... anyone wanna explain it for us who aren't proficient with loads and such...?

January 13th, 2008, 07:19 AM	#12 (permalink)
dadm TDPRI Member Join Date: Jan 2008 Location: ludington michigan Posts: 23	I had a '68 princeton reverb years ago. it sounded beautiful but the drummer was too loud for it. Didn't have a good P.A. I used a 12'' 8 ohm along with the factory 10'', an LPB-1 power booster and played it wide open every night for a year. Never wrecked it but it always sounded best on about half without the extra stuff plugged in.

January 13th, 2008, 07:30 AM	#13 (permalink)
BoB/335 Tele-Meister Join Date: Aug 2003 Location: Long Island Posts: 473	I thought there would have been a lot of comments on the Fender Manual info. __________________ BoB/335

January 13th, 2008, 07:33 AM	#14 (permalink)
dadm TDPRI Member Join Date: Jan 2008 Location: ludington michigan Posts: 23	I had a '68 princeton reverb years ago. it sounded beautiful but the drummer was too loud for it. Didn't have a good P.A. I used a 12'' 8 ohm along with the factory 10'', an LPB-1 power booster and played it wide open every night for a year. Never wrecked it but it always sounded best on about half without the extra stuff plugged in. Last edited by dadm : January 13th, 2008 at 08:11 AM.