Background
See attached 2 (rather dusty) photos of an old open baffle opposing-driver sub-woofer project, I want to resurrect.
It uses:
Of note, in this kind of speaker, one needs to connect the drivers out-of-phase.
It worked great and matched very well with my large aluminum honeycomb DML main stereo speakers.
Next step
I have all the parts to construct a second one of these.
I don't have an extra stereo amplifier.
Key specifications of the drivers:
Questions
I have a stereo amp: Hypex NCore 2x125W 4 Ohm
I used this amp to drive this sub in the past (one channel to each driver)
Can I use this amp to drive two of these open baffle opposing-driver sub-woofers (each has 2 drivers)?
If yes, how do I wire them to the drivers (especially given I need each subs drivers driven out of phase).
Alternatively, I can buy another Hypex NCore 2x125W 4 Ohm, but I'd rather not if I don't have to.
Thoughts appreciated.
See attached 2 (rather dusty) photos of an old open baffle opposing-driver sub-woofer project, I want to resurrect.
It uses:
- a pair of 15" PrueAudioProject woofers, which PureAudioProject had Eminence optimize for open baffle.
- spacers to connect the drivers
- wrought iron table legs from which to hang the drivers
- rubber tie downs as the suspension
Of note, in this kind of speaker, one needs to connect the drivers out-of-phase.
It worked great and matched very well with my large aluminum honeycomb DML main stereo speakers.
Next step
I have all the parts to construct a second one of these.
I don't have an extra stereo amplifier.
Key specifications of the drivers:
Questions
I have a stereo amp: Hypex NCore 2x125W 4 Ohm
I used this amp to drive this sub in the past (one channel to each driver)
Can I use this amp to drive two of these open baffle opposing-driver sub-woofers (each has 2 drivers)?
If yes, how do I wire them to the drivers (especially given I need each subs drivers driven out of phase).
Alternatively, I can buy another Hypex NCore 2x125W 4 Ohm, but I'd rather not if I don't have to.
Thoughts appreciated.
Why are the woofers set apart. I saw something similar years ago with KEF B139 but cones together.
You should be able to drive two drivers connected in parallel from the Hypex amp. The drivers are 8 ohms nominal, so two in parallel will give a 4 ohm nominal load, which should not be a problem for the Hypex. Connect the amp to the first driver, and connect the first driver's terminals to the second driver's terminals, pos to neg and neg to pos, to give opposite phase.
There needs to be a gap between the drivers so the output can add. I've known KEF139 drivers used in sealed isobaric configuration. Maybe that's what you're thinking of?
I know that this is different than the Ripole design that uses opposing bass drivers but each driver has a very small, sealed cabinet behind it. I believe that he goes by Jazzman, and is a member here. I have always wanted to build at least one of these, yet the drivers may no longer be available.
The LINN Isobaric chambers are connecting the two woofers cones in series, The ones that you show is in open air, that is the part I don't understand.
I'm pretty sure that's not what the OP is doing, since he says the drivers are connected out of phase. The two cones move in the same direction at the same time. Two dipoles arranged like this add their output. Celestion did it with the system 6000 decades ago.
(If the two cones moved against one other, you'd get quadrupole radiation, which has even greater LF cancellation.)
(If the two cones moved against one other, you'd get quadrupole radiation, which has even greater LF cancellation.)
ianbe, I asked why there is a gap between the cones, I would have mounted them solid against each other, what is the advantage.
The advantage is 6dB output. (Yes, it's just two drivers in parallel, but in an arrangement that saves space, compared to mounting them one above the other.)
If you mounted them together without a gap, you still use double the power of one, but wouldn't get the extra 6dB.
The drivers operate out-of-phase in an opposing-driver configuration.
They generate energy (sound waves) from both sides of each driver.
Where would the energy go if one bolted the fronts of the drivers together?
As I understand it, the output from the two drivers adds - there's double the driver area, after all.
Is it really double the driver area? If some one stood right in front of me and our shadows overlap, is there double the area. Sorry I try relate things to real world, I am not so sharp. If they where side by side I would agree without a doubt. It seems that only the rear of these cones would radiate the sound like a single driver with front and back hardly double the cone area. The out of phase will still wrap around and, I think cancel
If the cone pulsate away from each other you are trying to create a sound sphere, which I think is a good thing similar to an instrument or drum in free air.
I will try setting it up in the morning I have two BD139s. I think two woofers in tandem will not create the same SPL as two woofers side by side. There may be a slight different in frequency response, but even that I doubt. It is worth the try, I am looking for a small subwoofer to support the little LS3/5 on my desk and two open frame woofers if the idea works would be great especially made with four bolts only. It would be the simplest woofers ever.
The low frequency wavelengths are so long compared to the driver size the orientation makes no difference.
Either orientation would result in a +6dB gain, +3dB from doubling radiating surface and +3dB from doubling power.
Phase and polarity are not interchangeable terms.
The reversed cone to cone orientation, reversed polarity drivers operate acoustically in phase with each other.
If the drivers orientation was reversed, magnet to cone, the drivers would be wired in polarity to operate acoustically in phase with each other.