I'm currently planning to make a pair of 2-way open baffle speakers;-fullrange and woofer.
The woofer (Eminence Alpha 15A), will be powered by a 45 watt Quad Vena II solid state amp, and the fullrange (Coral Flat 8 II) by a 2A3 SET-tube amp.
The fullrange is 101dB and the Eminence is 97dB so the fullrange will need to be brought down to the same level as the Eminence.
Only problem is the 2A3 amp is only 3 watts or so, but I've been thinking this may work none the less.
So,-the total system will have a sound pressure level of 97 dB at 1 watt/1 meter distance (3 feet).
At 2 watts the level will be 100 dB at the same distance.
6 feet away we're talking 94 dB, and at 12 feet (listening position) the sound level will be 91 dB, and take note that the 2A3 amp will still have some juice leftover.
91 dB is considerably louder than a freight train at 100 feet distance (80dB) so it will hopefully be loud enough.
My listening room is roughly 15 by 15 feet, so not a concert hall.
I will mostly use the system for TV sound and for listening to music now and then,-not heavy rock mind you.
As I see it the little 2A3 amp may be sufficient to power those Coral fullrange speakers above 200 Hz or so, but I may be out on a limb here so please feel free to correct me if I'm wrong.
The woofer (Eminence Alpha 15A), will be powered by a 45 watt Quad Vena II solid state amp, and the fullrange (Coral Flat 8 II) by a 2A3 SET-tube amp.
The fullrange is 101dB and the Eminence is 97dB so the fullrange will need to be brought down to the same level as the Eminence.
Only problem is the 2A3 amp is only 3 watts or so, but I've been thinking this may work none the less.
So,-the total system will have a sound pressure level of 97 dB at 1 watt/1 meter distance (3 feet).
At 2 watts the level will be 100 dB at the same distance.
6 feet away we're talking 94 dB, and at 12 feet (listening position) the sound level will be 91 dB, and take note that the 2A3 amp will still have some juice leftover.
91 dB is considerably louder than a freight train at 100 feet distance (80dB) so it will hopefully be loud enough.
My listening room is roughly 15 by 15 feet, so not a concert hall.
I will mostly use the system for TV sound and for listening to music now and then,-not heavy rock mind you.
As I see it the little 2A3 amp may be sufficient to power those Coral fullrange speakers above 200 Hz or so, but I may be out on a limb here so please feel free to correct me if I'm wrong.
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Remember that the 3W amplifier limit will be for the peaks, not for the average level.
Average level will be from 10dB to 20dB lower, depending on the music and recording.
Average level will be from 10dB to 20dB lower, depending on the music and recording.
Yes, the average level will be much lower but if the 2A3 amp is too small I'll build something beefier at a later stage.
I don't play very loud, but if it doesn't work out the 2A3 amp will find its use for other things.
In a real room (as opposed to an anechoic chamber) the attenuation of sound does not follow the inverse square law (which BTW is 6dBspl for a doubling of distance, not 3). On the other hand you'll have quite a lot of room gain.
TV sound is heavily compressed.
TV sound is heavily compressed.
Yes, that's why I'll take my chances on a 2A3 SET-amp.
I've built tube amps before and repaired and modified a ton of guitar amps, even wound power x-formers and output iron.
But,-I've never tried direct heated triodes. I'm very curious about those relics from the past and I'd love to build something in that category.
This is what I noticed that the sound from the TV is very compressed. I thought it was the audio equipment's fault. I thought that these high-end TVs do not have that anymore.
It's either in the video recording itself, or done by the station. The TV doesn't have a compressor in it.
What are you going to do for equalization. OB is a nasty set of compromises to be met. Have you read Linkwitz on this subject? But then again, a full range with a whizzer cone, the response is all over the place no matter what you do. Mock it up and see what happens!
Have you considered how to deal with the difference in gain?
Have you considered how to deal with the difference in gain?
I've run a 89dB sensitive speaker (a fullrange MLTL without sub) from an 7.5w solid state class A amp and that was enough for a room of 3.5x6.5x2.5m (11feet 6inch x 21feet 4 inch x 8feet 3inch roughly) and that was enough for my neighbours to complain. Your space is a bit smaller i think, and your driver is +10dB more sensitive so that should be similar. 90dB in such a room is very loud, and count that room gain add some db to it.
tvrgeek: Yes, drivers do have whizzer cones, and are presently mocked up on OSB boards with wings. They sound OK,-at least to my ears.
As for the difference in gain there are two easy possibilities: -Bringing down the full range level in the crossover, or by bi-amping and make the amp for the full range units have a high pass filter in its input circuit.
As for the difference in gain there are two easy possibilities: -Bringing down the full range level in the crossover, or by bi-amping and make the amp for the full range units have a high pass filter in its input circuit.
The coral units are presently driven by a Quad Vena II, 45 watts and it doesn't take much on the volume control to make them sound very loud.
I think the 2A3 amp could be worth a try.
