# Making 16 ohm speaker into virtual 8 ohm?



## ed2000 (Feb 16, 2007)

Disclaimer: Just wondering
Would this work - using a 16 ohm speaker in parallel with 2 8 ohm voice coils(only) in series to yield 8 ohms combined?
Secondly, using a 16 ohm resistance device in parallel with the 16 ohm speaker to give 8?

The numbers add up but I think there is something I'm missing in my theory -inductance, phase??


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## jb welder (Sep 14, 2010)

Your math is correct, but it is important to warn you that power handling of a speaker is only with the voice coil properly in the magnet gap. The voice coil out removed from the speaker will not be able to handle much power at all.


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## greco (Jul 15, 2007)

ed2000 said:


> Secondly, using a 16 ohm resistance device in parallel with the 16 ohm speaker to give 8?


IIRC, I read about this in the far distant past. 

The two things that I remember (and, when we hear from the techs, we will see if my memory is any good ) are that:

1) Your tone is altered...please don't ask why or how because it wasn't explained.

2) That you need a resistor of reasonable power handling capabilities calculated on the output power of your amp in watts. IIRC, you should have a power resistor rated at about 1.5 times greater than the power output of your amp. Hence, a 30 watt output should have at least a resistor rated for ~45 watts (maybe I'm confusing this with building a dummy load).

*If I am correct*, these resistors are nice ( I had one in a dummy load):

They are by Dale/Vishay and come in many specs.










I will following this thread with much interest.

Cheers

Dave


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## dtsaudio (Apr 15, 2009)

Yes, your math is correct. But in your first example with the voice coils not only would power handling be limited as JB mentioned, but the impedance will not be 8 ohms without the magnet in the gap.the inductance therefore the impedance is only valid with the iron in the core.
The resistor example will also work, but half your power is dissipated as heat, and could be a lot of heat. The net effect on the amp is nil.
You will also slightly change the tone of the amp because the transformer is now supplying the tubes with a different load. Both distortion and frequency response change.
You're much better off getting the right impedance speaker or if possible changing the output tap on the transformer.


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## greco (Jul 15, 2007)

dtsaudio said:


> The resistor example will also work, but half your power is dissipated as heat, *and could be a lot of heat.* The net effect on the amp is nil.
> 
> 
> You will also slightly *change the tone of the amp* ......


I forgot to mention the heat issue and the probable need for some sort of heat sink. I got caught up in trying to remember what I had read about this in the past. It is amazing how hot those encased power resistors become even after a few minutes of playing into one used as a dummy load with a wattage rated at about twice the maximum output wattage.

@dtsaudio...How would you subjectively describe the slight change in tone? Just curious.

Cheers

Dave


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## ed2000 (Feb 16, 2007)

...How would you subjectively describe the slight change in tone? Just curious.
Cheers
Dave

Woody maybe, or wooly, or woofy(sorry, couldn't resist...see signature)



Perhaps parts of the frequency response curve may show dips or notches


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## greco (Jul 15, 2007)

ed2000 said:


> Woody maybe....


I just knew this would happen.

Now that I think about it again, it is a bit of a dumb question on my part...LOL.

@ed2000...Did you decide to try the resistor? 

Cheers

Dave


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## ed2000 (Feb 16, 2007)

.

@ed2000...Did you decide to try the resistor? 

As stated in the posting I was just wondering what to do if I ever have a 16 ohm speaker. Basically I'm trying to learn new (completely useless) ideas to stimulate some inactive neurons.

Thanks for the posts, y'all, to my hypothetical musings.


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## High/Deaf (Aug 19, 2009)

I built a resistive load, primarily for my YBA1-Mod1. Four 32 ohm 10W resistors in parallel in a small metal enclosure with a pair of 1/4" jacks. I have two 8 ohms boxes (1X12 and 2X12), and the Traynor has a 4/8 ohm switch. 

The biggest reason for this was the jumps in the master volume control (they call it an attenuator). The settings are 40, 20, 5, 1 and 0.1 watts. With the dummy load, I get 20, 10, 2.5, 0.5 and 0.05 watts. So with the quick change of a switch and a plug, I can go 40, 20 (two different ways), 10, 5, 2.5, 1, 0.5, 0.1 and 0.05, making it easier to set the master to the room and be able to set the volume controls for the amount of gain I want.

It does change the sound a bit, perhaps a wee bit brighter or harder sounding. But it can be tamed with the presence control a bit, and the extra settings are worth it.

I intended to try it with the DRRI as well but haven't gotten around to it. It does mean I'd be running the amp at 4 ohms, but I like to wind that amp up a bit and its often too loud for the room when I do that.


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## greco (Jul 15, 2007)

High/Deaf said:


> *It does change the sound a bit, perhaps a wee bit brighter or harder sounding.* But it can be tamed with the presence control a bit, and the extra settings are worth it.


Bingo! 

Thanks

Dave


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