1995 Fender Blues DeVille 410 Speaker Impedance

[HD28]

The 1995 Blues DeVille I just bought had the 4-10 inch speakers changed from alnico blues to generic NoName 12.5 ohm resistance speakers. They are wired in 2 pairs, 2 in parallel, in series with the other 2 parallel.
The resistance for each speaker is 12.5 ohms, exactly. The resistance for the 4 of them totals 12.5 ohms exactly.
I assume that the impedance of each of these replacements are 16 ohm nominal.
There are numbers on the bottom 2 speakers only as shown. The top 2 are numberless.
As stated, the total resistance load on the speakers is 12.5 ohms.
Is it electronically safe to play and crank this amp until I get new speakers?

 

[Hpilotman]

I owned that very amp and it originally was wired at 8 OHMS and Extension Jack could plug in another 8 OHM cabinet to make 4 OHMS MINIMUM.
I personally would not run 16 ohm speakers although it should not hurt the amp as most Fender Tube Amps can operate at 100 % Mismatch.
Notice Fender went the other direction Away from 16 OHMS to 4 OHMS when using an extension speaker cabinet.
In my opinion the amp will perform MUCH BETTER at 8 or 4 OHMS.

 

[Lowerleftcoast]

It should be fine.

As mentioned above, the output transformer has a 4 Ohm tap. You can wire the speakers all in parallel and plug into the extension speaker jack. You must also plug a 1/4 inch dummy plug in the main speaker jack. The dummy plug must not be shorted tip to sleeve.

Actually either one of the speaker jacks can be used with a dummy plug in the other. (I prefer the extension jack for the speaker because electrically it is a more direct route.)

 

[Superpicker]

I always thought you could operate the amp at higher homage on speakers but not lower?

 

[HD28]

It should be fine.

As mentioned above, the output transformer has a 4 Ohm tap. You can wire the speakers all in parallel and plug into the extension speaker jack. You must also plug a 1/4 inch dummy plug in the main speaker jack. The dummy plug must not be shorted tip to sleeve.

Actually either one of the speaker jacks can be used with a dummy plug in the other. (I prefer the extension jack for the speaker because electrically it is a more direct route.)

Thank you.
I made a 2-4-8ohm dummy load for testing a super reverb before. This should work, no?

 

[Hpilotman]

PAGES 6 and 7

https://www.fmicassets.com/Damroot/Original/10001/OM_leg_gtramp_Blues_De_Ville.pdf

 

[Wally]

I always thought you could operate the amp at higher homage on speakers but not lower?

This is true for solid state amps, which can be operated with amply speaker load that is not less than the recommended lowest impedance.
With tube amps, the circuit operates safest and most efficiently with a matched load. A lower impedance of 50% of the recommended load puts the stress on the primary side of the OT…mainly the power tubes. A 100% mismatch to the high side puts the stress on the OT secondary winding by placing it in danger of damage by flyback voltage…especially if you push the amp.
I would wire those 16 ohm speakers in parallel for a 4 ohm load….or run two in parallel for an 8 ohm load.

 

[Lowerleftcoast]

I made a 2-4-8ohm dummy load for testing a super reverb before. This should work, no?

Wally answered the question.

You would be better off with all 4 speakers wired in parallel on the 4 Ohm tap or two speakers wired in parallel on the 8 Ohm tap. Don't bother with a dummy load.

A dummy plug just holds an internal switch open. It does not provide a load.

 

[Wally]

Wally answered the question.

You would be better off with all 4 speakers wired in parallel on the 4 Ohm tap or two speakers wired in parallel on the 8 Ohm tap. Don't bother with a dummy load.

A dummy plug just holds an internal switch open. It does not provide a load.

Llc, is not the main Spkr Jack a shorting Jack that will interfere with the ext Spkr Jack/OT relationship unless one uses a dummy plug in that main Jack?

 

[Lowerleftcoast]

Llc, is not the main Spkr Jack a shorting Jack that will interfere with the ext Spkr Jack/OT relationship unless one uses a dummy plug in that main Jack?

Yes. The Main speaker jack shorts to ground. A dummy plug would need to be inserted to open the jack switch. A 4 Ohm load could then be inserted in the Ext Spkr Jack.

Alternatively, a 4 Ohm load could be inserted in the Main Spkr Jack when a dummy plug is inserted in the Ext Spkr Jack.

The dummy plug physically works the jack switches. The dummy plug does not short circuit anything. The dummy plug does not have a connection from tip to sleeve.

 

[Wally]

Yes, I understand the dummy plug. My problem is that I was the dummy…I neglected read the word plug. Rather, I 8nstalled plug where you had written load! Duh on me.