2nd order LR series xover formulae

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Calculating Zeta...2nd order

Can anyone point me to the formula for calculating Zeta for a 2nd order series crossover????

Found the 1st order formula st John Kreskovsky's site.
From the searching I've done, most seem to have put 2nd order series xovers into the too hard basket?
Most calculators will do 1st order but not 2nd.

Cheers,
Pete McK
 
Re: Calculating Zeta...2nd order

PeteMcK said:

From the searching I've done, most seem to have put 2nd order series xovers into the too hard basket?

Cheers,
Pete McK

Not so much too hard, just not much point.

A series x-o is for "combining" drivers, not for controlling and separating them.

If you need to use a 2nd order series x-o, then use the one discussed on this page..... it gives the necessary control while still combining the drivers quite well.
http://users.tpg.com.au/users/gradds/SeriesXO/series_cross-overs9b.htm

If your drivers need more control than a 1st order series of a 2nd order AR series offers, then you should be using a parallel x-o, not a series x-o.
 
Hi,
I am jumping in without my wings, since I haven't read Art's article.

L-R requires even pole filters and a Q=0.5 for the phase response to match across the crossover region.

I don't think that L-R can be achieved by mixing single and two pole filters.

If going active, this is easily achieved by cascading a pair of Butterworth Q=1/root2 filters giving the required Q=0.5 and cascading ensures that even order poles are met. Passive is a whole other ballgame. Pay special attention to errors resulting from non resistive loads on the crossover and non zero source impedance (less of a problem).
 
Andy, "A series x-o is for "combining" drivers" - aren't all crossovers?...but I think I understand where you're coming from; Parallel are easier to calculate & control the response because each section acts independently.

"If your drivers need more control than a 1st order series of a 2nd order AR series offers, then you should be using a parallel x-o, not a series x-o." Why?- that sounds like consigning it to the too hard basket...

I think it's just that because the sections in a series are interdependent, there's more to consider, & the calculations are harder. With an appropriate design tool (calculator + graphical simulator) it could be easier. As I'm trying to work out the series xover I'll be using, I'm also making up a simple? calculator for 2nd order series...

I'm going down this path because I want to try a series xover just for the he** of it (all those raves on your site :); I think the drivers I've got are suitable, and I want to go 2nd order on the tweeter because the xover point will be low (~1500Hz). I've got all the parts, will be hotting up the iron in the next few days.

Cheers,
Pete McK
 
PeteMcK said:
Thanks for the responses guys.
I've checked those sites, but they don't have exactly what I'm looking for; Guess I'll have to visit a library and check out some engineering tomes....

Pete McK

Pete,

My entry for the recent "Puget Sound! DIY Speaker Contest" used a combination 1st and 2nd order series crossover. The actual crossover design was done by Dave Rosgaard (The 200% Norwegian). He used a program that he has spent a couple of years developing. Are you looking for a crossover for a specific combination of drivers or just trying to come to terms with a reliable method of calculation?

BTW: my entry placed 1st in class and second overall for Best Sound in the contest. Not bad for a real budget speaker :^)
Best Regards,
TerryO
 
Apologies to Pete

I should have read further, your posting right before mine answers the question, sorry.

I really don't understand what all the excitement with modelling and calculating is about. I found out, after the speaker contest, that my arch-enemy, Dan Wiggins, told my neighbor (the fancy-pants Microsoft exec) that I was hopelessly "old school" when it came to designing speakers! Ha, just because he doesn't understand cubits and has problems using an hourglass for speaker measurements doesn't mean that it won't work!!!!:whazzat:

Best Regards,
TerryO
 
PeteMcK said:

"If your drivers need more control than a 1st order series of a 2nd order AR series offers, then you should be using a parallel x-o, not a series x-o." Why?- that sounds like consigning it to the too hard basket...

No, its just that generally, if corrections are required, they need to be done on one driver without influencing the other driver.

IMO. You are missing the whole point if you, for some reason, what to make major corrections to a driver when using a series x-o. ;-)

ps.. Pete, I note you are Sydney.. feel free to visit if you are ever up Newy way. contact first though !!
 
Cal Weldon said:
Terry,

Don't listen to those enemy types, especially the evil Dan Wiggins.

You and I can continue to use our "tin can and string" personal communicators. Let them laugh. We know they work just fine. They just don't know the secret of the special string and non- oscillating single ended cans. Oops, I just let it out.


Thanks Cal,

I needed that. It's so lonely for us "Back to the Future" types beset on all sides by those cunning, calculating devils, that it's often hard to remember that we hold the moral high ground. Let them do their worst, we can sit in our personal pyramids wearing our tin-foil caps, secure in our knowledge of the Arcane.

Best Regards,
TerryO
 
PeteMcK said:

I'm going down this path because I want to try a series xover just for the he** of it (all those raves on your site :); I think the drivers I've got are suitable, and I want to go 2nd order on the tweeter because the xover point will be low (~1500Hz). I've got all the parts, will be hotting up the iron in the next few days.

Cheers,
Pete McK

The second order AR with a big thick wire coil will provide pretty good protection to the tweeter. Probably not a good idea to use the WES coils (18g) if you are crossing that low, you need as low DCR as you can get or you will get a shelf on the tweeter cut off. I think Equinox have some 2mm wire they can wind for you.
 
I tried the AR crossover ( 1st order ) some while ago and was pretty impressed but I always felt nervous about turning up the power, due to the low crossover for the tweeter. I had considered the " 2nd ", but never got round to it. I eventually returned to the parallel network for peace of mind. But with the recent discussions about the potential benifits of using " waveguides " and the improvements gained, lower distortion, lower allowable crossover etc, I think another look at the AR network is on the cards. Possibly" series " networks in general may benifit from waveguide use, what do you think ?
 
Hi Terry,
'Are you looking for a crossover for a specific combination of drivers or just trying to come to terms with a reliable method of calculation?'
yeah, a bit of both. Do you have any more details on your xover? It's interesting to see how others go about it.
Re: calculations - well, I'd rather avoid them too, but it gets you to a reasonable result faster. I'm not really a tweeker, I'd rather be drinking lager and listening...:)

Andy,
'generally, if corrections are required, they need to be done on one driver without influencing the other driver. ' Good point. Actually I'm not trying to make any corrections (although there's a slight peak in the woofer at ~ 1600Hz I'd like to avoid, but it doesn't sound audible at present with woofer full range & just a cap and resistor on the tweeter...).

I'm occasionally up Maitland way, so wouldn't mind a side trip to swap some ideas. Probably won't be in the near future though.

Cheers,
Pete McK
 
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