JoeBob said:
This is exactly how you make an active tube XO.
Active Tube XOs
The heath XO-1 is a good example.
dave
Hi Bob,bob4 said:
For compression drivers, definitely no. In this instance if you use a shallow rolloff at the recommended xover frequency, and put a decent amount of power into them, the diaphrams will hit the phase plug, and dent them, or if you use TADs, shatter the beryllium diaphram. The lower the frequency a compression driver has to produce, the more excursion required, and like all drivers, distortion is proportional to about the square of the excursion, so keep it as low as possible. In a domestic situation, you can get away with a lot. My compression drivers are specced for 800W continuous at 400Hz with a 24db HPF at 400Hz. I use 6dB at 400, but seldom see 2W at home, so I'm still not going near the excursion limits.
Cone drivers front hornloaded will flap around madly if you put too much LF into them below the Fc of the flare, and it may not damage them, but could set up FM distortion within their passband and make them sound crappy. At the top end the mass corner of the driver, and it's inductance will eventually form about a 12dB rolloff, but it might not be that much on axis, making pattern control in an array difficult.
Ported boxes, sound best rolled off below the port frequency IMO. At the top end the large cones will start to beam and breakup, interfering with the performance of the units above in the system. Roll them off hard.
So in summary, no, rolloff the individual elements in a PA system out of band. Saves on wasted amplifier power too. The only exception I could think of would be in an installed system that was way over designed for the application, say something that was capable of supporting a loud rock band, and only ever did girl and guitar type performances. In that case it might sound better: might not too, and you want to be sure no one ever booked a thrash band for the room.
I had a chance to play with one of <a href="http://bpgprod.sel.sony.com/Professional/webapp/ModelInfo?m=0&sm=0&p=10&sp=89&id=55637">these</a> for a couple of weeks recently, and it sounded great when used in a PA application as I could dial everything in very well, but annoyed me at home on the Khorns, which sound better passive 6dB on the mid/high, and the bassbin run wide open..
Cheers
Another way to make exactly the same:planet10 said:
Use a Dual OP-amp
and put the Crossover between the 2 buffer amplifiers.
As gain is only 1 - the eventual effect on signal quality
would be minimal - you can say the OPamp is transparent,
doesn't effect signal to measurable degree
low cost - mininmal space - no complicated Power supply
even possible to use a couple of batteries.
There are OP amps (CMOS) - Complementary MOSfet output stage= PNP+NPN
that only consumes LESS than 10uA - 0.00001 Ampere
A litium battery would supply such an OPamp
for Years and Years.
CMOS OPamps - shouldn't this be heaven
for all our MOSFET - Loving Fellows
/halojoy wants to know more
Just figured out what WOFTAM means....
In my unenlightened days, I utilized a Crown VFX-1 active crossover with my ssssssolid sssssstate amps and thought I was really onto something.
Later on I made the mistake of using it between the drivers of the VOT with two tube amps.
If one ever needs a demonstration of just how horrible inserting solid state devices into the signal path can be, just try doing something like that!!!
Lee
In my unenlightened days, I utilized a Crown VFX-1 active crossover with my ssssssolid sssssstate amps and thought I was really onto something.
Later on I made the mistake of using it between the drivers of the VOT with two tube amps.
If one ever needs a demonstration of just how horrible inserting solid state devices into the signal path can be, just try doing something like that!!!
Lee
Industry's best kept secret
Frank,
thanks for the answer,
Brett, I will be using it to cross over between my subs and Mid/Hi CAbs at about 300 Hz or so. The tops are 2way, 15" / 1" , so the HF driver won't get in trouble. And I won't be using it forever, just until I can afford something better.
thanks for helping out everybody, I'll build the thing and tell you how I liked it.
Frank,
thanks for the answer,
I was just wondering if it would be efficient enough.....fdegrove said:Hi Bob,
Pssssst...
Industry's best kept secret...
Bob..Why shouldn't it?
Ciao,
Brett, I will be using it to cross over between my subs and Mid/Hi CAbs at about 300 Hz or so. The tops are 2way, 15" / 1" , so the HF driver won't get in trouble. And I won't be using it forever, just until I can afford something better.
thanks for helping out everybody, I'll build the thing and tell you how I liked it.
Simple enough to build, and as I'm on christmas vacation..... 
Yes exactly that.
But I can live with Brett's answer. I think for people listening areasonable levels it would work out fine.
In my younger days however I had peak levels of about 10 Watts or even more into a horn driver (O.K. I myself regard SPLs like this as insane as well nowadays !!) that was crossed over at 500 Hz. In this case a first order crossover would have definitely been insufficient.
Regards
Charles
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