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Post subject: Vintage Deluxe Speaker Ohm Question
Posted: Tue Jan 27, 2015 8:50 am
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I have a '65 Deluxe.

I've been reading up on the problems with making use of the ext. speaker jack on the vintage amps. The Deluxe is set for an 8 ohm load with one 8 ohm 12" speaker built into the amp. So, adding any speakers overloads the transformer and cuts power.

What if I swap out the internal 12" with 16 ohm speaker, then plug another 12" 16 ohm speaker into the extension jack? It seems that would create an 8 ohm load and get optimum power from the amp while driving two speakers instead of one.

Does this make sense? Wouldn't it be louder than just the 8 ohm 12" by itself?

Thanks,
Lincoln


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Post subject: Re: Vintage Deluxe Speaker Ohm Question
Posted: Tue Jan 27, 2015 9:31 am
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Maybe the best way to go is get a two X 12-inch external cab, loaded with two 16-ohm speakers in parallel --- in a sealed enclosure. The total impedance = 8 ohms, for that cab. Disable the internal speaker.

This setup will be prolly be louder (really, more efficient) than using one external 16-ohm, closed back and one internal 16-ohm, with open back in that Deluxe.

I had a two X 12 inch cab made for me. It has one Celestion Vintage-30 and one Weber 12A125. Both are 8-ohm speakers, wired in parallel = 4-ohms, for the Bassman head unit. Very nice setup, IMHO.


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Image


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Post subject: Re: Vintage Deluxe Speaker Ohm Question
Posted: Wed Jan 28, 2015 8:59 am
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Thanks for the suggestion.

This can be a frustrating topic. I've done a lot of reading about Ohms and the effects of mismatching and different cabs. It's hard because most of the information points to Fender being able to easily handily mismatched Ohmage and describe various combinations, but few describe tonal differences.

Some guys run an internal 16 ohm speaker by itself sometimes, and sometimes add another 16 ohm cab, and they describe the sound as preferable to a single 8 ohm speaker. But "preferable" tells me nothing about how it sounds.

And here's something else. Let's say you keep the stock 8 ohm speaker, and run another 8 ohm in a cab. The amp can't develop full power at a 4 ohm load, so it won't be as loud. HOWEVER, what is the tonal difference and "perceived" volume difference between amp vol on 8 with 2 speakers vs. amp vol on 5 with only 1 speaker? Sure, tone and volume knobs being equal, the power will be cut with 2 speakers, but you are running 2 speakers. It's a bigger sound. Is it cleaner? Dirtier?

If you listen to the amp at 5 then plug in another speaker and crank it to 8, it's probably going to be louder and bigger sounding. But are you driving anything harder? Has the tone changed? Is it breaking up more or less?

See? It gets complicated.


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Post subject: Re: Vintage Deluxe Speaker Ohm Question
Posted: Wed Jan 28, 2015 3:29 pm
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I really don't think the NOMINAL impedance value listed for a speaker effects the tone. "Nominal" because the actual impedance of a speaker varies throughout the frequency range. Nominal impedance is usually the measured impedance of the speaker at 1KHz with 1 watt of input.

Speaker's tonal response is a complicated matter. Based on frequency response of the amp. Characteristics of the speaker throughout the amp's frequency range. Its interaction with the amp's output tranny throughout this range. Physics of the cab it is placed in. Room dynamics.

The impedance of a speaker AND it's output... versus frequency effect the overall tone. Adding to each speaker's own unique tonal response.

Graph 1 show a speaker with a resonance impedance around 125Hz

Image

Graph 2 show a speaker with resonance impedance around 50Hz

Image


The two speakers will sound much different in the same amp. Regardless, of the amp's nominal output impedance. Notice how both speakers are nominally rated at 8-ohm impedance.


Here's a graph of the complex frequency versus output loudness response of one speaker.


Image


Notice how complicated the response really is.

Now, for that DR. I would not put mismatched impedance load onto the amp. It does not have the heavy duty output transformer, seen in bigger Fender amps. It prolly cannot handle a mismatch as well as these amps with those heavy duty OPT's. Stick to 8-ohm total impedance load.


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Post subject: Re: Vintage Deluxe Speaker Ohm Question
Posted: Thu Jan 29, 2015 1:42 am
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Myths die hard don't they? :roll:

I'm sure that Fender added a speaker jack so that you can just plug in another speaker without worrying about the mythical boogie man eating the transformer. Do you really believe that they put a trap there for some unsuspecting chump to plug in a speaker and blow his amp?

Your amp will work fine with an 8 ohm, or 4 ohm speaker load. A mismatch within a 2 to 1 ratio will be perfectly fine.

Those that advise against a mismatch.....how many transformers have they blown? I, and many forum members, routinely run many of my amps mismatched, and have for years, zero problems.

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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