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Multi-Way Conventional loudspeakers with crossovers

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Old 5th April 2004, 06:58 AM   #1
nrgy is offline nrgy  United States
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Join Date: Mar 2004
Location: Redmond
Default Need help creating parts list...

As I continue my venture into the DIY world, naturally I become more and more confused. I figure its best to create a shopping list of parts I need with the help of this board, so at least I will have something to reference off of for future projects. (plus things always become more clearer once I start to put pen to paper, so to speak) But before I begin, I'm even having trouble finding books on the topic of loudspeaker design. I've found several, however it seems that most of these use technical terms that are way to advance for a complete newbie (ie. Loudspeaker Design Cookbook), from the reviews I've read anyhow. Any recommendations, especially books that cover crossover design from scratch.

Ok, onto my project (which exists only in my head as of now): Please correct me if my understanding of any particular area is incorrect.

I posted before I want to create a pair of 2-way bookshelf speakers. For now, I would like to make this a complete DIY project, rather than a kit, mostly for the experience/fun/challenge. I've decided to go with a Vifa woofer and tweeter for this project. For simplicity, I'm trying to purchase most of my parts from PartsExpress.
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Driver Selection
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The woofer, while not absolute, I'm thinking of using the TC series 4-1/2" - http://www.partsexpress.com/pe/pshow...=297-344&DID=7 or perhaps the 5-1/2"

Do I go with the standard woofer or a shielded woofer? I'm not quite sure I know the difference.

Also, when it says power handling 20 watts RMS/60 watts max, does this mean I have to use a receiver rated at less than 60 watts? If so, then I might step up to the 5-1/2".

As for the tweeter, I am considering one of the Vifa classic series. I'm not sure what would be sufficient, however, the soft or metal dome. The aluminum dome seems to have a broader frequency range, so perhaps that is the one I should go for - http://www.partsexpress.com/pe/pshow...=264-512&DID=7

Again, uncertain about whether to go shielded or unshielded.

So to recap, assume the Vifa TC 5-1/2" Midbass woofer and the Vifa Classic 1" aluminum dome tweeter.

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Crossover Components
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This is still a very muddy area for me. First off, when using WinISD to calculate crossover components, I don't get the same numbers as other crossover designs. For example, I looked at Parts Express Dayton 2,500hz crossover schematic, ( http://www.partsexpress.com/pdf/260-142s.pdf )and tried to replicate this crossover in WinISD just to see if I was using the program right. So I went to the crossover calulator, clicked on the Passive 2-way 2nd order, and plugged in the numbers.

Frequencies: Bass cutoff - 2,500 hz / Tweeter cutoff - 2,500 hz
Drivers: Bass Z - 8 ohm / Tweeter Z - 8 ohm

L1 = .72 mh
L2 = .36 mh

C1 = 11.254 uF
C2 = 5.627 uF

Now the schematic for the 2-way 2nd order 2,500 hz crossover says:

L1 = 1.02 mh
L2 = 1.02 mh

C1 = 3.98 uF
C2 = 3.98 uF

Why are these numbers so different? What I am doing wrong here? This seems like this would be a fairly simple/generic 2nd order crossover to calculate.

Ok, now if some could help me actually figure out what parts I need for a 2nd order crossover. And would a 2,500 hz crossover point work with the drivers I had in mind?

I don't mean for people to do my homework, but I really don't know where to begin when picking crossover components, even if I am told the correct L1, C1, etc. numbers. Could someone create a parts list from PartsExpress of all the parts I would need to create a crossover? I was thinking of just buying a finished crossover just to have something in my hand to look at, but I would like to try this first and see if I have any luck.

Also, I'm assuming a Zobel network and L-Pad attenuator are needed. Is there a basic explanation of how I arrive at these numbers? I see WinISD as an L-Pad calculator, but I'm confused on what "Needed attenuation" means. What is this number that I input?

I believe that is all for now. I know this is probably too many questions to answer in one post, but I appreciate any responses I get.
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Old 5th April 2004, 07:16 AM   #2
diyAudio Member
 
Join Date: Mar 2003
Location: brisbane queensland
I dont know if it will help but it is still worth a read

http://www.speakerbuilder.net/web_files/Articles/xover article/xpointmain.htm

Have you throught about trying the vifa p17wj-00-08 mid woofer with the d25 AG-35-06 tweeter. there are a lot of different designs using these two drivers on the web .

Attenuation is the difference in db between to drivers ex the p17 is 88 db & the d25 tweeter is 91 db in sentivity so you want to attenuate the tweeter by 3 db { If I am wrong some please correct me }

The only reason to go with the shielded is if you plan to put them close to or on top of your television.

you can try this as well

diyAudio reference speaker project

here is another site to try
http://ccs.exl.info/calc_cr.html
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