I'd be pretty pleased about being able to go to 126L with WAF being taken into consideration
Tony.
Volume really isn't a limit - its form factor and your ability to *sell* it.
Perhaps the easiest way is with an in-wall design. Only a few DIY'ers seem to do that though.
Because it is best to have the drivers at xover display an identical radiation pattern. It is easy to see why.
Suppose a middriver that already is in the region where it starts to beam (above circumference of cone > 1 wavelength) crossed over to a tweeter (which at that frequency radiates in 4 pi). It will now only be possible to have a flat FR at one unique listening angle. At smaller listening angles, the middriver will tend to be too loud, and at larger angles it will become too soft in the crossover region. This is by the way the reason why in well designed two ways, the tweeter is mounted in a waveguide that ensures it has a radiation pattern at crossover that matches that of the midwoofer.
Please do the calculations yourself, and you will find that a 5 inch midrange has to be crossed over fairly low, and that you need another, smaller driver to cover the gap between the tweeter and the 5 inch midrange. Or, alternatively, you have to correct the radiation pattern of the tweeter with a waveguide to match that of the midrange. Not so easy to get right without an adequate measuring environment.
Andrew,
Take for example a 5 inch midrange, circumference is about .4 meter, corresponding to a wavelength of 875 Hz. Above this frequency, the driver will move from 4pi to 2pi radiation. This is a gradual shift, so at let's say 1600 Hz, the driver will radiate in the shape of a forward lobe. Outside that lobe, the driver will radiate less energy than inside, but it is a continuum of course. Hence the custom to demarcate the boundary of the lobe where SPL has fallen by a set number of dB.
Now, cross it over to a tweeter, which typically is much smaller. It will radiate in 4pi at crossover, so at different listening agles, the SPL will be constant.
So, now you have two drivers @ crossover, the middriver that has a gradual shift in SPL in function of listening angle, and the tweeter that has a constant SPL at different listening angles. Result: you can only get a flat FR at one specific listening angle.
Take for example a 5 inch midrange, circumference is about .4 meter, corresponding to a wavelength of 875 Hz. Above this frequency, the driver will move from 4pi to 2pi radiation. This is a gradual shift, so at let's say 1600 Hz, the driver will radiate in the shape of a forward lobe. Outside that lobe, the driver will radiate less energy than inside, but it is a continuum of course. Hence the custom to demarcate the boundary of the lobe where SPL has fallen by a set number of dB.
Now, cross it over to a tweeter, which typically is much smaller. It will radiate in 4pi at crossover, so at different listening agles, the SPL will be constant.
So, now you have two drivers @ crossover, the middriver that has a gradual shift in SPL in function of listening angle, and the tweeter that has a constant SPL at different listening angles. Result: you can only get a flat FR at one specific listening angle.
Thanks moondog, will read the thread for sure. This audio hobby keeps on getting more and more interesting.I'd be pretty pleased about being able to go to 126L with WAF being taken into consideration
Tony.
Yeah, 126L is quite big and my WAF situation was risky I can say. In fact, its more like she do not agree but now the wood is cut so there'S no turning back, shell get use to it!
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