Mr. Pass, how much power would be required to drive these 15" beasts?
I've been thinking of the F4 to drive them but am wondering how much less I can get away with?
I've been thinking of the F4 to drive them but am wondering how much less I can get away with?
WRT baffles, I prefer to keep the baffle peak above the driver's bandwidth, for each driver (read separate/minimal baffles). The benefit is smoother off axis response - operating a driver above the baffle peak causes ripples in the off axis response.
I agree with MJK, the Alpha 15a in a H-frame is a very good place to start.
One of the first considerations for choosing a mid driver is its volume displacement - if you want to cross below 250Hz, you need a driver 6" or larger. You also have to consider its Xmax. Martin's worksheets are very good at predicting the volume displacement you need for a given xo point and SPL level desired.
One of the things that gets overlooked is the drivers power handling - for many mid drivers (6" and 8"), it is common to max out the power handling before maxing out the volume displacement. In the lower midrange (100-400Hz), dipole roll off greatly reduces the drivers sensitivity, requiring a large amount of power (via EQ) to smooth the FR. High QTS helps with this, but there aren't really many high QTS mid drivers. Only the most sensitive pro drivers (rated 95dBSPL+) max out the power handling at the same time as volume displacement (again, for 6" and 8" drivers).
Anyway, OB is a totally different ballgame than box speakers. MJK's and John K's worksheets are indispensable to well designed speakers. I found 'the Edge' and XLBaffle to be inaccurate. LinkwitzLab is a great resource, and he has posted a few Excel spreadsheets there that can be helpful too, particularly the 'closedbox' one.
I agree with MJK, the Alpha 15a in a H-frame is a very good place to start.
One of the first considerations for choosing a mid driver is its volume displacement - if you want to cross below 250Hz, you need a driver 6" or larger. You also have to consider its Xmax. Martin's worksheets are very good at predicting the volume displacement you need for a given xo point and SPL level desired.
One of the things that gets overlooked is the drivers power handling - for many mid drivers (6" and 8"), it is common to max out the power handling before maxing out the volume displacement. In the lower midrange (100-400Hz), dipole roll off greatly reduces the drivers sensitivity, requiring a large amount of power (via EQ) to smooth the FR. High QTS helps with this, but there aren't really many high QTS mid drivers. Only the most sensitive pro drivers (rated 95dBSPL+) max out the power handling at the same time as volume displacement (again, for 6" and 8" drivers).
Anyway, OB is a totally different ballgame than box speakers. MJK's and John K's worksheets are indispensable to well designed speakers. I found 'the Edge' and XLBaffle to be inaccurate. LinkwitzLab is a great resource, and he has posted a few Excel spreadsheets there that can be helpful too, particularly the 'closedbox' one.
Yes, I've had the opportunity to play with the 15 and 12
AE woofers, both very excellent.
Hi Nelson,
Have you had occasion to try a low Qts woofer on OB w/ the F1? I wonder if the ability to dial in the amount of dampening needed would allow a good bit of flexibility in choosing a woofer. Thanks.
Regards,
John
Have you had occasion to try a low Qts woofer on OB w/ the F1? I wonder if the ability to dial in the amount of dampening needed would allow a good bit of flexibility in choosing a woofer. Thanks.
Regards,
John
In fact the 'school' is about keeping each drivers working range significantly below the first dipole null of the corresponding baffle. The relation between baffle width and driver diameter is just a consequence of this. In real life this goal can not be achieved for frequencies above 7 kHz because of the physical size of even the smallest tweeters.
Who is saying that 'it is the only way to design an OB'? For a two-way system with a limited amount of EQ your way is the only one to get the best result possible IMHO.
Above 'school' definitely calls for a three way (or even four way) system with a sizable amount of low end EQ for midrange and tweeter.
Consequently it is not a rival philosophy to yours but a sort of 'upgrade'. Whether the supposed improvement in reproduction quality does justify the increased complexity and cost is up to the individual.
Xlin = 11 mm p-to-p ? Isn't that a bit small for an 18'' woofer??
Seems quite normal to me, if you look at normal pro woofers
Twice the Xmax of Eminence Alpha15
And many other Eminence woofers
I suggested SM118N because of the Qts of 0.49
The new 12" Beyma SM212 is rare with 14mmXmax, and low distortion
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