Changing impedance of a speaker cabinet

[crossbones]

Hi,
I have a 1 x 12 extension cab with a 16 ohm speaker.
(An impossible one to replace)
Is there a way to install a resister in the cabinet to bring the impedance down to 8 ohms?
If there is, than I guess it would also be possible to have it switchable?
Would it affect the sound of the speaker?

Thanks.

[R.G.]

Hi,
Is there a way to install a resister in the cabinet to bring the impedance down to 8 ohms?

Yes. You parallel it with a 16 ohm resistor. This changes the nominal impedance down to 8. However, speaker impedance can vary by 4:1 with frequency. That 16 ohm speaker may (depending on its construction and the speaker cabinet it's in) vary between as much as 8 to 32 ohms as it sits at different frequencies.

If there is, than I guess it would also be possible to have it switchable?

Yes.

Would it affect the sound of the speaker?

It would affect the sound of the combined speaker/amplifier setup. If the amp is a tube amplifier, its output depends somewhat on the loading. This is in fact why speaker impedance matters as much as it does. So the additional load would change the way the amplifier "sees" the speaker.

And in addition, the resistor would eat nominally half the power the amp put out into the speaker/resistor combo.

[hasserl]

Yes, you could wire a large wire wound resistor in parallel with it to change the reflected impedance, but the resistor will need to be of sufficient wattage rating to handle at least half of the power you'll be sending to the cabinet, and it definitely will effect the sound, not in a good way.

If you need a different impedance cabinet the best thing to do is to swap out the speaker for what you really need.

Or, use the Weber Z Matcher to match up the impedance of the existing speaker to what you need: https://taweber.powweb.com/store/zmatch.htm

[crossbones]

Thanks R.G.,

I know the best route would be to get a correct impedance speaker, but the one I have in the cabinet is special. (Impossible to find)
Where would you get a resister like that that would handle up to a 40 watt amp?

Thanks again for looking.

[Jazz P Bass]

Thanks R.G.,

I know the best route would be to get a correct impedance speaker, but the one I have in the cabinet is special. (Impossible to find)
Where would you get a resister like that that would handle up to a 40 watt amp?

Thanks again for looking.

http://www.amazon.com/Ohm-20W-Resist...uct/B0002KR4GG

[Steve Conner]

You need a 16 ohm resistor, not 8.

[crossbones]

Wow thanks!

[g1]

Put 2 of those 8ohm 20W in series, then you have a 16ohm 40W resistor. Place that in parallel with the speaker. Better to go overkill on the wattage than to burn up a 20watt (because you're really cranking it to make up for the lost power ).

[Jazz P Bass]

You need a 16 ohm resistor, not 8.

OOps.
Heh, heh. Can't read.
20 Ohm 20W Resistor Wire Wound 017-20
Thanks Steve.

[pdf64]

I don't think that the use of resistors is a good option; as pointed out it will affect the response by interfering with the interaction between amp and speaker, and will waste power.
Firstly, what amps are we talking about?
Many can tolerate a '1 step' mismatch'.
Pete.

[crossbones]

Well,
A 50's Fender champion 600.
65 deluxe reverb.
Several 60's Gibsons.
Several other older amps.
A Japanese solid state amp that I won't name.

[pdf64]

There should be no issue with driving a solid state amp into 16ohms.
For the others, if you are using them clean then I wouldn't worry about it, just use the speaker straight, as is.
If you do hammer the amps, then consider fitting a multitap output transformer to the main one.
Or get the Weber Z Matcher.
Pete.

[SpareRibs]

Hello,
If you look at Organ's some of them have 16 ohm speakers. I have seen them on Craigslist free. The last one I saw was full of 12AX7 and 12AU7 tubes, it also had 2- 12" speakers.