I have a pair of each of Faital Pro 8hx150 coaxials and 18fh500 woofers. I have been thinking about putting them back to back magnets facing each other, nude open baffle at ear height. Delay can be added on DSP. Crossover around 300hz ish. Can you think of any major problems?
Hi MrKlinky,
are you sure? logic says wavelength is so long that pressure due to nearby subwoofer is about the same on both sides of the coax, hence no extra force on it. If it was closed box then yes, pressure outside would vary with the sub but not inside, so in this case there would be force to the coax cone? Or would it be due to velocity rather than pressure? Trying to think analog with dynamic microphones and how they work.
This is the case with all loudspeakers, including the tweeter on the coax, sffected by the woofer of the coax. Except between subwpofer and the open baffle coax woofer here? microphonics
I have no experience or knowledge on it other than the logic.
are you sure? logic says wavelength is so long that pressure due to nearby subwoofer is about the same on both sides of the coax, hence no extra force on it. If it was closed box then yes, pressure outside would vary with the sub but not inside, so in this case there would be force to the coax cone? Or would it be due to velocity rather than pressure? Trying to think analog with dynamic microphones and how they work.
This is the case with all loudspeakers, including the tweeter on the coax, sffected by the woofer of the coax. Except between subwpofer and the open baffle coax woofer here? microphonics
I have no experience or knowledge on it other than the logic.
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zmyrna - interesting idea!
It should work if you cross low enough. Dsp enables crossing a bit higher because of delay adjustment.
However the big woofer will change midrange's rearside radiation pattern, but how much must me measured!
Distortion might increase too in midrange.
It should work if you cross low enough. Dsp enables crossing a bit higher because of delay adjustment.
However the big woofer will change midrange's rearside radiation pattern, but how much must me measured!
Distortion might increase too in midrange.
I am thinking of 40-50cm distance between the front planes of the two drivers. Being a fully open design, I was hoping that they won't affect each other that much.
Pano, if the coax had a baffle, it would affect the front wave of the woofer. If the woofer had a baffle, it would block the back wave of the mid. Mid and woofer will be handling only 2 octaves each. A baffle would not add much. Plus the benefits of no baffle. I plan to use it with subs.
Juha, I have proposed back to back placement for a reason. I am hoping that the conical back side of the woofer and the basket would act as a diffuser. Being a ferrite driver with a large magnet, the coax already has a big obstacle on its back side. The woofer probably won't add much negatives.
Attachments
Not sure. But is there a benefit to out of phase with delay? Maybe this could benefit from using the Ripple Tank...
I've never found that to be a benefit, rather the opposite. But it will be interesting to see what you get. Even better to hear it, of course, but we take what we can get. 😉
Hi zmyrna, if you crossover say 200Hz, the wavelength is so long, about 1.5meters, the coax is almost acoustically invisible to the 18inch output. But the coax plays up to perhaps to 20cm wavelenth, which reflects and diffracts heavily on nearby objects like the big woofer behind.
One can wonder about the stuff in VCAD with ideal drivers, thats the absolute best ideal situation with no interaction between them. One can estimate if some construct /positioning was better than some other.
Here ideal naked 18" and 8" stacked , arbitrary crossover.
Here the big woofer is behind, and the same with flipped polarity
The crossover here is so low it doesn't make much difference. Tune closer to what you have in mind to gauge if its feasible system. If it is feasible like this, then you could quite quickly whip up a jig to measure in reality how it would work out, how much interference there would be and listen if its something to worry about.
One can wonder about the stuff in VCAD with ideal drivers, thats the absolute best ideal situation with no interaction between them. One can estimate if some construct /positioning was better than some other.
Here ideal naked 18" and 8" stacked , arbitrary crossover.
Here the big woofer is behind, and the same with flipped polarity
The crossover here is so low it doesn't make much difference. Tune closer to what you have in mind to gauge if its feasible system. If it is feasible like this, then you could quite quickly whip up a jig to measure in reality how it would work out, how much interference there would be and listen if its something to worry about.
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Curious if the rarefaction segment of the woofers' output will overcome the compression segment of the coaxial drivers' output. I can see a lopsided dipole pattern as a result ... on the wrong side no less.
Yes, I've tried that too! The unconnected speaker outputs a signal when excited. To suggest that a speaker close to another one would not be 'driven' by it implies that it is not subject to the changes in air pressure where it is positioned. The speed of sound is obviously finite and air is compressible, so the pressure wave front will hit one side of the cone before the other, therefore a force will be applied to it before the wave is diffracted around the cone and equalises on the other side. The cone movement will mimic that of the driving force but with a delay/phase change.
The 8" mid is about the same size as the magnet of the woofer. So it won't do much to the radiation of the woofer. The bigger concern imo is the woofer's effect on the backwave of the mid. However there will be 30-40cm between the two and the back surface of the woofer is not flat but conical. So my best guess is that it would work ok.
The back to back configuration will be quite bulky. I am currently looking for my next place to live. I will build and test the triaxial if I get a large living space. If not, I will probably go for a more traditional up down set up.
The back to back configuration will be quite bulky. I am currently looking for my next place to live. I will build and test the triaxial if I get a large living space. If not, I will probably go for a more traditional up down set up.