Re: Crossover design choice - seeking your input!
Hey Jack,
IANAPCD (I Am Not a Passive Crossover Designer), but I suppose it would be accurate to say I am an active crossover designer. I don't know that it's accurate to say that a passive can do things an active can't, except perhaps for some impedance flattening (and that's of arguable value except in the HF). When you only have one amp channel available then yes, you need a passive crossover. But that's not technical ability, that's cost cutting. A good passive crossover is almost like a powered loudspeaker sans limiters and protective high pass... plug in the box and go, no need to worry that the settings are right. The basic acoustic stuff is the same, just the way you get there is different. There's a low cost of entry to build a mediocre passive, and the more you want it to do the more it's going to cost. Almost any DSP can do pretty much anything you'd want to be doing to a loudspeaker, but you need to pay at least a certain amount to get into that club.
To be fair, if you asked me what the "crossover point" was on any of my tunings I'd have to look at a final acoustic measurement, what I put into the DSP would probably sound weird to you... of course, the best part is coming back to a tuning to discover that someone has "fixed" my "wrong" crossover points.
Here is the deal on passive vs active.
First the old active analog from TDM, Biamp, JBL etc are basisaly a “One Trick Pony”
They have High-pass, Low-pass, Band-pass and that is about it.
The exception was the added EQ for CD horns.
Next we have the DSP (active digital).
Typical being the DBX driverack family
This would have several different types of “knee” on a xover such as LR, Butterworth, etc.
In addition it would have several to many full Parametric EQ.
The PEQ gave you some flexibility.
Now on to Passive. Start with using the proper filters for a 4th Order LR at 8 ohms.
Add a 2nd Order Butt.
With passive xovers transform all the area between those two curves is available.
You can get something close using the DSP. Start with the high-pass and low-pass you need and then add as many PEQ as necessary.
You will find that the interaction between all those PEQ filter may become a problem.
All this said for your DIY I vote for an active solution.
Either a self-powered box or an outboard DSP such as a Driverack.
My reasoning is that if we have to go to a different driver the DSP can be easily adjusted.
It also gives the DIY enthusiast something to play with and learn from. I don’t see very many people rolling their own passive xover.
In the end I suppose you should offer both if possible.
On drivers, everything starts with the quality of the drivers you pick.
Spend some money here.
If you use a cheap driver the most expensive xover will not cure it.
That said I will play devil’s advocate.
A friend has a Yamaha waveforce.
It uses an Eminence 15”, a Eminence 1” throat compression driver and a large conical horn.
He bought them not working with part of the xover fried.
He asked me to find the fault and use the old parts as much as possible because he did not have the money right then.
After I was done I used about 75% of the caps and inductors to get a fairly smooth response.
Out of all his speakers he rents out and uses this pair more then all of his speaker boxes.
NOTE: A big part of the sound is that conical horn.
If you feel you can live with 60-degree us a conical horn if possible. I say this because most of the conical horns I have seen have been both small a narrow.
