Xover design help

[kelticwizard]

Have not found the site yet. Looking for one. I could say, "Find a nice textbook on AC circuits" but I would bet the info is on the internet, and it only takes a few paragraphs to explain.

How does theta degrees fit in? Well,

A) if 0 degree or 360 degrees is exactly right-add two values that are either 0 degrees or 360 degrees apart and you get twice the amplitude

and

B) if 180 degrees is exactly wrong-add two values together 180 degrees apart and you get zero

then

if two values are added together that are not 0, 360 degrees or 180 degrees apart, then they must come out being something between twice the amplitude or zero amplitude. That value theta tells us what.

PS: It is not linear. It goes according to a sine wave.

[kelticwizard]

Pinkmouse:

Thank you so much for the formula for the notch filter. Man, you are one precise guy-you take the value for 2 pi out to four decimal places!

One thing, though. Looking over the equation, I see that the formula includes F or Frequency and C for Capacitor value. But the notch filter also includes an inductor, which is normally labelled L. Yet the formula for the notch filter contains no mention of L for inductance.

Since the inductor has just as much to do with the phase angle as the capacitor, are you sure there is no value for "L" in that equation? Or has the value of L already been converted into terms of F and C in the equation as written?

Just asking before I start figuring, (my math skills are limited enough as it is, LOL).

[kelticwizard]

Bose:

Haven't found the webpage for you yet but here is nice web page about crossovers that I think you might like. Explains a lot. It tells you at what level crossovers the drivers should be compared to the midpoint at various configurations: each driver should be 3 dB under the midpoint for first order crossovers, 6 dB under for second order, etc.

http://www.traymann.free-online.co.uk/xover_2.PDF

[pinkmouse]

oops...

The bracketed bit should be:

(1/6.2832FL -......FC)

Talk about sad, when I was about 10 years old, I could recite pi to 100 decimal places

p.s. Anyone know of an equation editor on the Mac OSX? (don't say M$ office!)

[kelticwizard]

Originally posted by pinkmouse


Talk about sad, when I was about 10 years old, I could recite pi to 100 decimal places

Don't tell me, let me guess. Your parents sent you away to one of those famous British boarding schools? Is that what they make those kids do there? (In America, the parents would sue the school for "Neuron Overload Abuse" or something).

Now, one more thing. I take the value of this equation for any frequency that is whithin the notch filter's range, correct?

I can get the phase angle of any woofer at any frequency just by plugging the Thiele small parameters into Subwoofer Simulator, a freeware program written by F4ier, a member of this forum.

Once I establish the phase angle for the frequency selected before the notch filter is added, do I just add that value to that value from this formula? So if the reactance is -20 degrees at the selected frequency before I add the notch filter, and the equation yields a value of +15 degrees with the notch filter, do I have a total phase angle with the notch filter of -5 degrees?


Anyhow, is the equation written correctly below?

p.s. Anyone know of an equation editor on the Mac OSX? (don't say M$ office!)

I would think that your fellow moderator, Planet 10, would be the man to ask for that one.

[Bose(o)]

Originally posted by kelticwizard
Bose:

Haven't found the webpage for you yet but here is nice web page about crossovers that I think you might like. Explains a lot. It tells you at what level crossovers the drivers should be compared to the midpoint at various configurations: each driver should be 3 dB under the midpoint for first order crossovers, 6 dB under for second order, etc.

http://www.traymann.free-online.co.uk/xover_2.PDF

Thanks a lot Wiz, hopefully I can help you out on a project of your own some day.

[prash]

Sorry to butt in, but are you guys going to build the xover with the manuf. specs? How about actual measurements which will be quite diff from the "marketing" dept figures of the mfrs.

unless, I dont know, Audax has more precise numbers or something.

Just curious.

[pinkmouse]

Yup, Wiz, that's the one!

After thinking on this for a while, I'm not sure if we need to worry about phase angle too much, or even sorting out that peak. It might be worth while for a first cut just going for a 3k crossover with a standard second order Xover, or at least waiting on the in box measurements of the mid/bass driver, just to seee how bad it is in reality.

The reason I thought this was that I was going through a load of old back issues of Hi-Fi mags, and many commercial speakers have much worse dips and lumps than this, so although it may look nasty, it may not work out in reality to be so bad.

Hmmm, I don't know...

Now, one more thing. I take the value of this equation for any frequency that is whithin the notch filter's range, correct?

AFAIK- the phase change is maximal at the centre frequency of the filter, and alters in proportion to the slope of the filter. As for the rest, yes!


Regarding Pi, no i was just a sad kid!

[Kram]

Wow, I was surprised to see so many replies after my absence from the Internet over xmas, Thank you to you all.

kelticwizard
I will try that cap value that you suggested for the time being, then I will try whatever more complex xover you guys come up with later on. and we will see if i can hear the difference.

Thank you
Kram