OT set to 16Ω vs. 4Ω: Difference in volume?

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junior marbles
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OT set to 16Ω vs. 4Ω: Difference in volume?

Post by junior marbles »

I can install a 16Ω or 4Ω speaker (each of the same design) in my 1974x.
I can also install 2 speakers in my 1973x, either using 2 16Ω speakers = 8Ω , or 2 8Ω speakers = 4Ω (parallel) or 16Ω (series).

After setting the correct output impedance on the OT, which of these settings will be louder? Healthier for the amp? Better sounding? Or does it even make any difference?
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NickF
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by NickF »

When impedances are matched, I was told it doesn't make any difference to output volume. It's when you mismatch that you can get less output.
If the speaker is 97db efficient it's a great speaker. If it's 103db efficient it's a better speaker, you get more sound pressure per watt of power pumped into it.

As an aside, I've seen a few Youtube vids lately where people are claiming different impedance V30's of different years of manufacture sound different. I'd put that down to something like cone material or magnet strength though. These same people made a few videos of supposed differences. Personally I think it's splitting hairs and there are better things to worry about.
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by JMPGuitars »

Speaker efficiency doesn't make one speaker better than another; it may make it louder though. Higher speaker efficiency increases power/volume.

The only time the output impedance matters is with most (not all) of the 18W OTs. 4 ohm and 16 ohm usually have their own windings, but 8 ohm taps are usually only half the 16 ohm winding. This is why the 16ohm output is typically preferred.

Thanks,
Josh
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junior marbles
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by junior marbles »

The only time the output impedance matters is with most (not all) of the 18W OTs. 4 ohm and 16 ohm usually have their own windings, but 8 ohm taps are usually only half the 16 ohm winding. This is why the 16ohm output is typically preferred.
OK, you are saying that in my case it does not matter whether I use the 4Ω or 16Ω setting on the dual-speaker 18W model as long as I install the speaker with correctly matching impedance? Both are exactly the same in terms of efficiency, compatibility, tone, etc.?

But on my single-speaker 18W amp with a tappable OT, why is 16Ω "typically preferred" over 8Ω? What is the electrical explanation rather not to tap my OT's 16Ω secondary winding and therefore rather not install an 8Ω speaker, if I have a choice?
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by JMPGuitars »

junior marbles wrote:
Tue 12/14/21 3:47 pm
OK, you are saying that in my case it does not matter whether I use the 4Ω or 16Ω setting on the dual-speaker 18W model as long as I install the speaker with correctly matching impedance? Both are exactly the same in terms of efficiency, compatibility, tone, etc.?

But on my single-speaker 18W amp with a tappable OT, why is 16Ω "typically preferred" over 8Ω? What is the electrical explanation rather not to tap my OT's 16Ω secondary winding and therefore rather not install an 8Ω speaker, if I have a choice?
First part: Not exactly. I don't know whether or not a 4ohm tap is as delicious as the 16ohm tap. You would probably have to make a few recordings and compare them to form a proper opinion.

Second part: A lot of the 18W magic comes from soaking the OT. If you cut the sponge in half, you soak up less of that delicious juice. Less juice = still thirsty. ;)
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by Daviedawg »

as Josh suggests try it and see. You have two speakers to test at different impedances. Even if the speakers are described as the same spec apart from that, they can have variations in sound. So try them for a few days each then see what you think about them. Like guitars, speakers can vary individually to a some degree.

Or just go with the flow and fit the 16ohm?

Dd
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by turtle441 »

FWIW, I found this video very educational. I'd always felt that it made the most sense to use the highest impedance if you could since it seemed like you'd be using "more" of the OT. (How's that for science?) With that said listening to the recordings on the video, I felt like I preferred the lower impedance option better.

https://www.youtube.com/watch?v=WP6uHtClwec

I will openly acknowledge that I was not tracking some of what Josh mentioned regarding separate windings for 4 ohm vs 8 ohm. I've always assumed OT's would take both 4 and 8 ohm as a tap off of the entire winding. I suppose that just opens a different rabbit hole to go down when it comes to OT construction and making these decisions.
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by JMPGuitars »

turtle441 wrote:
Wed 12/15/21 11:16 am
I will openly acknowledge that I was not tracking some of what Josh mentioned regarding separate windings for 4 ohm vs 8 ohm. I've always assumed OT's would take both 4 and 8 ohm as a tap off of the entire winding. I suppose that just opens a different rabbit hole to go down when it comes to OT construction and making these decisions.
That's why it's important to check the OT specs, and hopefully there's an accurate schematic drawing depicting whether or not there are separate windings at all. For any OTs sharing all outputs by tapping the same winding, I would stick with the full winding (16ohm).
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by Bieworm »

4 Ohms is for F€nd€r people😄
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Re: OT set to 16Ω vs. 4Ω: Difference in volume?

Post by junior marbles »

That's why it's important to check the OT specs, and hopefully there's an accurate schematic drawing depicting whether or not there are separate windings at all. For any OTs sharing all outputs by tapping the same winding, I would stick with the full winding (16ohm).
Excellent point to consider when talking to transformer winders!
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