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Shelbyturbo1989
07-12-2006, 06:56 PM
I am planning on building a set of stereo speakers. I have been trying to learn how to design crossovers for them but am having a very difficult time understanding how to calculate the final impedance of the assembled speaker. I would like to end up with an 8 ohm speaker, but the only setup I can come up with ends up as a 4 ohm design. Currently, I am planning on having each cabinet contain:

Two 8 ohm tweeters
Four 8 or 4 ohm mids
Two 8 ohm woofers

I looked at the designs on parts express and tried to make sense of how the impedance the builders claim adds up, but to no avail.

A general layout of how this would be possible would be greatly appreciated. Any input on the order/type of network to use would also be a great guide my understanding. Thanks.

Vic

Beat_Dominator
07-12-2006, 07:09 PM
My first question is why 2 tweeters per cabinet? It's a rare thing to need that much output in the higher registers. It seems to me that the 2-8ohm woofers and 2 tweeters is causing the problem as they would be wired to 4ohm before the x-over.

joetama
07-12-2006, 07:24 PM
Do, the two tweeters in parallel (=4 ohms) and the two woofers in parallel (=4 ohms). Then do two of the 4 ohm mids in series (=8 ohms) then put the two together in parallel (=4 ohms)
Then cross them all over in a 3 Way X-over. With that many drivers you are going to need a good deal or wattage so 4 ohms would be better for you.

Is there a reason you also want to go with such a complex speaker design? You could spend the same money, but on better drivers and have a much more simple system that would totally kick ***.....

Shelbyturbo1989
07-12-2006, 11:08 PM
Here is my initial design:

http://thumb7.webshots.com/t/36/37/2/81/33/2111281330065614607FYdsIb_th.jpg (http://community.webshots.com/photo/2111281330065614607FYdsIb)

The two holes in the middle are where the tweeters would be placed. The reason for the complex design is because I listen to heavy metal/rock at high volumes. I haven't experienced a set of speakers with only a few drivers that I liked the sound of when they started to get loud. To me it seems that the larger number of drivers allows them to produce more sound without having to exhert them as much, thus making for better sound (kind of like a line array). This is mostly based off of intuition however because I've only been fortunate enough to hear only a few high end systems (often not with my musical tastes).

If I use two 4 ohm woofers in series, four 4 ohm mids in series/parallel to get 8 ohms, and drop down to one 8 ohm tweet I will be able to get my desired 8 ohm speaker. I am unsure if the single tweeter will be able to keep up though...

jlaine
07-16-2006, 12:06 PM
95% of the time a single tweeter will keep up with multiple midwoofers/midranges due to driver sensitivity and auditory sensitivity relative to the midrange(s).

Actual impedance is going to be a factor of the drivers used, enclosure applied, and crossover network itself. If you aren't comfortable designing your own crossover (which it sounds like you aren't yet) and want this done - I suggest contacting places like Madisound/Adire Audio/Etc. and have your design custom made by them - that way you know exactly what you are getting.

Decipha
07-16-2006, 12:09 PM
how can you learn if some one else does it for you? I say trail and error... just don't give up, if you are truely determined to get the sound you want with enuff time money patience and knowledge you will... anything is possible

jlaine
07-16-2006, 12:12 PM
how can you learn if some one else does it for you? I say trail and error... just don't give up, if you are truely determined to get the sound you want with enuff time money patience and knowledge you will... anything is possible

Because if you don't see it done right, you'll never have a grasp as to what you are doing and why. The proven designers out there are thurough, have the equipment to test the drivers, and will explain what was done and why. That type of knowledge is worth the cost when you can not only get the design, but get your questions answered as to why.

Trial and error can be saved for less expensive projects, I wouldn't do something as permanent as these as a blind hit and miss - start with something smaller for that - component set for the car or something easily modified.

JimJ
07-16-2006, 02:20 PM
Kind of the same advice I'd give someone starting out in amp building - don't try to tackle something huge like a 211 triode amp with 1kW+ voltages going around...you're liable to waste a lot of money on parts and stand a good chance at getting hurt.

You don't have to worry about getting killed working on a speaker like this, but the same principle applies. That's a really complicated design to start out with, and I'd take Josh's advice. Hell, even if they just give you a schematic and you buy all the parts, they've done the legwork for you. Then it's just a matter of soldering everything together.