Changing Speaker Impedance - Opinions?

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JMPGuitars
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Changing Speaker Impedance - Opinions?

Post by JMPGuitars »

I have a few 8 Ohm speakers I really like, but of course I'd rather have 16 Ohms for my 18 watt amps.

Obviously the easy answer is to sell/trade them for some 16 Ohm speakers. However, I'm curious about opinions on doing something like increasing the resistance with a high wattage wire wound resistor in series...

Other ideas? Opinions?
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CurtissRobin
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Re: Changing Speaker Impedance - Opinions?

Post by CurtissRobin »

A series resistor would give you a higher resistance but it'll change your sound substantially. Remember that a speaker voice coil is an RL (resistance-inductance) circuit and changing R without changing L changes the impedence-frequency curve, a.k.a. its response, to a given signal. Give it a try and let us know what you think.

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Re: Changing Speaker Impedance - Opinions?

Post by JMPGuitars »

Which direction do you think the curve will go? Do you think it will be a tone curve shift, or with the response turn into mud?

I assume I need to use at least 20 watts for the resistor value? I'd just try it out for the heck of it if I have high enough wattage resistors lying around.
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Re: Changing Speaker Impedance - Opinions?

Post by CurtissRobin »

I'd expect some muddying of the sound. A resistor attenuates without regard to frequency while a coil in series attenuates highs ergo the combination will attenuate more at the high end than at the low end. Not much, but probably just enough to muddy the sound. OTOH if you've got one of the really bright 18 watt amps it could be the ticket to take the edge off. I've never tried it but it's come up in conversation every couple decades or so. It'll be interesting to see what you learn.

The resistor won't dissipate anywhere near the full power of the amp since the speaker still uses its share, but oversize resistors in this application is a good, conservative design idea.

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Re: Changing Speaker Impedance - Opinions?

Post by Weldaar »

Two 8 ohm speakers will give you 16 ohms. I have two 8's in my cabinet and I run them at 16 ohms. You just have to wire them in series.
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Re: Changing Speaker Impedance - Opinions?

Post by dollarjoe »

A few years back, I wanted to use my 2X12 Marshall angle cab in conjunction with my Marshall JCM800 4210 (1X12) combo. I took my 1X12 to http://www.wembleyloudspeaker.com/. They re-coned the 12" speaker in the combo to a different impedance. They're still in business, I believe, in Shepherds Bush, W. London.meaniesbobs#2.jpg
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Re: Changing Speaker Impedance - Opinions?

Post by musicheals »

I tried this before and it will bring not a better tone. It will get slightly muddy. Using 16 ohm speakers will not give you noticeable improvement in tone, only if you want to believe it. I wouldn't change anything...

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Re: Changing Speaker Impedance - Opinions?

Post by JMPGuitars »

musicheals wrote:
Thu 06/10/21 1:55 pm
I tried this before and it will bring not a better tone. It will get slightly muddy. Using 16 ohm speakers will not give you noticeable improvement in tone, only if you want to believe it. I wouldn't change anything...

Thank
musicheals
You're only sort of correct. There's no reason to add a resistor, that won't help. But a properly matched speaker will affect the tone. For example, most 18 Watt Output Transformers have 2 secondaries- 4ohm, and 16ohm. The 16ohm being larger, and center-tapped to provide an 8ohm tap. If you're on the 8ohm tap, you're only using half the secondary. 16 ohms nominally matched correctly to a 16 ohm speaker does sound better, as you get more out of your OT.

Now, will that difference blow your mind? I doubt it, but it does exist, and it is perceivable. Obviously if you have an amazing 8 ohm speaker, and a crappy 16 ohm speaker, go with the 8 ohm. There's never just 1 magic variable (other than your playing skill). ;)

Thanks,
Josh
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