Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: shortfuse on October 20, 2011, 11:19:53 am
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My question is in a 412 cab whats the difference if you use 4 8ohm speakers or 4 16ohm speakers as far as the sound and tone are concerned and why. I realize this is a personal taste question and answers are going to vary but I am curious.
I ran my own experiment at home and found I liked the 4 8ohm speaker sound better. I tried it wired up both for 8 ohm and 16 ohm.
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I ran my own experiment at home and found I liked the 4 8ohm speaker sound better. I tried it wired up both for 8 ohm and 16 ohm.
How did you wire 4 8Ω speakers for 16Ω?
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I am not aware of any sonic difference between the same model speakers in 8 and 16 ohm versions.
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I ran my own experiment at home and found I liked the 4 8ohm speaker sound better. I tried it wired up both for 8 ohm and 16 ohm.
How did you wire 4 8Ω speakers for 16Ω?
Sorry I meant to say I tried 4 of the same speakers 8 ohm wired up at 8 ohm, and 4 of the same speakers 16 ohm wired up 16 ohm. I don't think you can get 4 8's to 16 can you? It may just be me but I thought the 4, 8 ohm wired 8 ohm sounded punchier.
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The model of the 8 ohm speakers were the same as the model of 16 ohm speakers?
Were these both plugged into the same amp? Was the amp set for 8 ohms with the 8ohm wiring arrangement, and 16 ohms for the 16 ohm case?
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The model of the 8 ohm speakers were the same as the model of 16 ohm speakers?
Were these both plugged into the same amp? Was the amp set for 8 ohms with the 8ohm wiring arrangement, and 16 ohms for the 16 ohm case?
Yes, yes, & yes. All were Eminence Governors. I have a friend that has a 412 Marshall cab with the 8 ohm arrangement. And, my 412 Marshall is loaded with the 16 ohm arrangement. They are both in 1960B cabs.
Does it make the difference where the presence control resistor (I think this is called the negative feedback resistor) is attached to at the impedance selector in the back of the amp? I have my Hoffman Plexi 50 wired up just like the diagram with the 47K. http://www.el34world.com/Hoffman/images/Plexi50Old.gif (http://www.el34world.com/Hoffman/images/Plexi50Old.gif).
Now playing out of my friends amp which is a DSL50 there was not a noticeable difference in tone until you got into the higher volume levels and again the 8 ohm arrangement sounded punchier. Seems to me the best sounding arrangement should be 16ohm as most 412's are sold with 16' in them. Does that make any sense or is it just me?
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yes, yes, & yes. All were Eminence Governors. I have a friend that has a 412 Marshall cab with the 8 ohm arrangement. And, my 412 Marshall is loaded with the 16 ohm arrangement. They are both in 1960B cabs.
Then there should be no difference in sound. Other than possible differences in individual speakers of the same type due to tolerances.
Does it make the difference where the presence control resistor (I think this is called the negative feedback resistor) is attached to at the impedance selector in the back of the amp? I have my Hoffman Plexi 50 wired up just like the diagram with the 47K.
It does matter where the resistor is, but doesn't matter if you're using an impedance selector switch.
That resistor is part of the feedback loop. The voltage present at the OT secondary tap (8 ohms for the stock circuit in this case) is divided by the series feedback resistor (47k) and shunt feedback resistor (5k presence pot here), then introduced into the phase inverter. The amp was designed with the stock amount of feedback in mind.
Now if you have an impedance select switch, it doesn't matter what tap you're using, the amp still sees the same amount of feedback. There is a voltage present at every tap all the time. So, if you're using the 16 ohm tap, and the feedback resistor is still connected to the 8 ohm tap, both are getting what they need. In other words, don't think you need to move the feedback resistor to a different tap.
If, however, you had a multitap OT but the tap used and feedback resistor are hardwired to the output jack, when you re-wire for the 16 ohm situation, you are actually increasing the amount of feedback in the amp. You might then think the 8 ohm arrangement sounds "punchier" or "more raw". That's because there is more voltage present at the 16 ohm tap for the same power output, and when moved to the 16 ohm tap, the feedback resistors then pass more feedback voltage to the phase inverter.