Tube amps have a specific load they need to drive, straying from this load can cause component failure. Reasons being is the speaker load on the secondary of output transformer is reflected onto the primary to load the power tubes.
Tube amps are not like SS amps in regard to halving the load impedance will yeild roughly double the power. That is if you are planning to hook up two different drivers to the same connection point effectively putting them in parallel. Two 8 ohm speakers in this configuration would equal a 4 ohm load. If you are going to mismatch the load you are better off going lower then higher. Example: running two 8 ohm speakers in parallel from an 8 ohm speaker tap. It will not be any louder with two speakers.
Edit: The math would be (from a voltage source) Power = (V^2) / R
Tube amps are not like SS amps in regard to halving the load impedance will yeild roughly double the power. That is if you are planning to hook up two different drivers to the same connection point effectively putting them in parallel. Two 8 ohm speakers in this configuration would equal a 4 ohm load. If you are going to mismatch the load you are better off going lower then higher. Example: running two 8 ohm speakers in parallel from an 8 ohm speaker tap. It will not be any louder with two speakers.
Edit: The math would be (from a voltage source) Power = (V^2) / R
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I would think it would be the opposite if anything. You would get less voltage across the smaller load on the primary translating into less voltage on the secondary
This is the same reason you don't increase the load to a valve amp.......the increased AC voltage swing on the primary can exceed the insulation rating.
The Absolute Sound (at that time) thought that stacked Advents were just great, and much better than just one pair.
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Loudness and power and volts, oh my!! (Sorry, but someone had to.)
As someone who rocked the stacked Advents for several years back in the late 70s (on a Crown DC-300), I remember the sound was not just louder after adding the second pair, but somehow stronger, more authoritative; although I hadn't learned enough at that point to really understand what I was hearing. Thankfully I have since moved on from that setup*, but I think what I was hearing was all about the wavelengths as has already been mentioned.
Assuming your power amp is up to the task, with 2 stacked loudspeakers of the same design (and typical home-stereo dimensions), the lower frequencies tend to sum more, while the higher ones tend to interfere more. So it would seem to me that compared to a single unit, the combined power output into the room would be a downward slope, adding closer to 6 dB at the bottom end and closer to 3 dB at the top.
Having identical doubled systems, I imagine the overall slope would be fairly smooth, by 1970s standards at least. Surely it got a bit(!) ragged as frequency increased, but even that might've subjectively improved somewhat towards the top end as the interference modes got closer together. Not exactly today's recipe for pinpoint imaging of course, but I was just a kid back then and didn't really understand any of those finer points - I was just digging that funky new room curve, heh. Stronger & more authoritative, indeed! More is better, especially if it's skewed toward the bottom end!
-- Jim
*Actually, I do still have 2 of my original Advents, sort of. I pulled the original woofs and replaced them with 12" Kenwood car audio woofers (the large Advent woofers used a 10" cone in a 12" basket), and bypassed the old internal crossover. With a little Linkwitz transform and some PEQ to notch out the room modes, they go right down to 15 Hz now, taking "Advent bass" to a whole new level.
As someone who rocked the stacked Advents for several years back in the late 70s (on a Crown DC-300), I remember the sound was not just louder after adding the second pair, but somehow stronger, more authoritative; although I hadn't learned enough at that point to really understand what I was hearing. Thankfully I have since moved on from that setup*, but I think what I was hearing was all about the wavelengths as has already been mentioned.
Assuming your power amp is up to the task, with 2 stacked loudspeakers of the same design (and typical home-stereo dimensions), the lower frequencies tend to sum more, while the higher ones tend to interfere more. So it would seem to me that compared to a single unit, the combined power output into the room would be a downward slope, adding closer to 6 dB at the bottom end and closer to 3 dB at the top.
Having identical doubled systems, I imagine the overall slope would be fairly smooth, by 1970s standards at least.
Surely it got a bit(!) ragged as frequency increased, but even that might've subjectively improved somewhat towards the top end as the interference modes got closer together. Not exactly today's recipe for pinpoint imaging of course, but I was just a kid back then and didn't really understand any of those finer points - I was just digging that funky new room curve, heh. Stronger & more authoritative, indeed! More is better, especially if it's skewed toward the bottom end! -- Jim
*Actually, I do still have 2 of my original Advents, sort of. I pulled the original woofs and replaced them with 12" Kenwood car audio woofers (the large Advent woofers used a 10" cone in a 12" basket), and bypassed the old internal crossover. With a little Linkwitz transform and some PEQ to notch out the room modes, they go right down to 15 Hz now, taking "Advent bass" to a whole new level.
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