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Daganjah View Drop Down
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    Posted: 23 May 2021 at 8:32pm
Hi everybody 
im sorry for my bad english

i don't know if its the right place to ask but...

im new in the crossover world and i want to know if I can use the knowledge you have.
I want to build a crossover board but I do not know how to calculate the data to my board.
I want to build a 2-way crossover board for my tops.
i use b&c 12fw76 for the woofers
and the peavey 44xt 
i want to cross the frequencies at 700hz 
hope to get some help from you guys
thank you 
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Conanski View Drop Down
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You can build a basic passive crossover for those drivers.. but you're not going to like the results. What I suggest you do is biamp them and process it with DSP.
To make these drivers sound good they will need parametric EQ, time alignment, level matching, and CD horn correction... assuming the 44xt will be mounted on a CD horn. Some of this can be accomplished with passive components but just zeroing in the optimum component values is a laborous process. 
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Earplug View Drop Down
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There are several online calculators that will give you a basic circuit, eg:-


But that will be very basic - and as mentioned above, will be far from perfect. Also, 700Hz sounds very low a xover point. Why so low? The B&C will happily go much higher. 1500Hz-2000Hz would be far more sensible.

And you will have to derate the power going to the Peavey, besides the fact that I don't think that it will sound too good at those frequencies either.
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Buy a cheap MEMS mic like the Behringer ECM8000, Sonarworks XREF20, or easier still, the USB-powered UMIK-1 for < £100 and make some basic measurements of your drivers mounted in the cabinet / on the horn, solo.

Whack those files into VituixCAD (https://kimmosaunisto.net/ - free) and fiddle with component values all you like, with real-time updating of the complex results. You can even include off-axis data (you should).

A calculator based purely on free-air T/S parameters is barely getting you in the neighbourhood, let alone the ballpark.
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Conanski View Drop Down
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Originally posted by Earplug Earplug wrote:

Also, 700Hz sounds very low a xover point. Why so low? The B&C will happily go much higher. 1500Hz-2000Hz would be far more sensible.

No no no... this is a 2" exit CD, there is nothing wrong with a 700hz crossover here, in fact with DSP processing and the right horn this combo can perform really well.  
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Earplug View Drop Down
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Originally posted by Conanski Conanski wrote:

Originally posted by Earplug Earplug wrote:

Also, 700Hz sounds very low a xover point. Why so low? The B&C will happily go much higher. 1500Hz-2000Hz would be far more sensible.

No no no... this is a 2" exit CD, there is nothing wrong with a 700hz crossover here, in fact with DSP processing and the right horn this combo can perform really well.  



Yes - just a matter of taste really.

I don't think that an alu diaphragm is going to sound good at 700Hz - never mind the fact that it will not last that long. A lot more stress there.

If you go back 30 or 40 years, you will find some pro systems that used comp drivers at midrange frequencies, but often with mylar or phenolic diaphragms. I can't think of any pro system these days that would use a comp driver so low. It really makes no sense.
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Conanski View Drop Down
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Originally posted by Earplug Earplug wrote:

I don't think that an alu diaphragm is going to sound good at 700Hz - never mind the fact that it will not last that long. A lot more stress there.
Good point there but.. are these drivers original or have the diaphrams been replaced with something else.

Originally posted by Earplug Earplug wrote:

If you go back 30 or 40 years, you will find some pro systems that used comp drivers at midrange frequencies, but often with mylar or phenolic diaphragms.
I have heard more than a few systems from that era that would rip your head off but I'm pretty sure that was operator error and/or a lack of processing. I do like the sound of phenolic diaphrams but I don't have any complaints about the ti diaphrams in the big B&C comps I own so I know it can be done. I also have some big EV drivers that are a lot more aggressive sounding so without a doubt your milage does vary with this same as it does with many other things, but overall big comps crossed low has been a revelation for me, nothing else I have ever owned comes close to delivering the same midrange clarity. 

Originally posted by Earplug Earplug wrote:

I can't think of any pro system these days that would use a comp driver so low. 
All of the higher end RCF boxes use lower crossover points and they are well known for superb sound quality.
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