New to speaker building and I have a question

[GVSS]

I am thinking of building a center channel speaker for my home theater system. I am familiar with series vs parallel wiring but I am very confused by how they affect overall system impedance.

i.e. - if I have a 8 ohm midrange and an 8 ohm tweeter connected to a 2-way crossover, will the overall impedance of the whole speaker system be 8ohms, 4ohm, or 16 ohms?

I have searched for hours on the net and I haven't been able to find a clear cut answer.

Any help is appreciated

Thanks

GVSS

[oneplustwo]

I think it depends on how your crossover is wired. If in parallel, it will be 4 ohms. If in series, it will be 16 ohms. There's also the resistance of the crossover components themselves to consider. Also, impedance can change with frequency so there's another twist. What's the impetus to your question? Are you going to design your own center channel? If not, you can just look at the impedance curves of whatever design you're replicating to understand what your amplifier will need to contend with.

(I'm still new to this myself so I'm only about 25% sure anything I said made sense.)

[GVSS]

Basically I'm trying to build my own center channel speaker to fit into my entertainment center, so I have specific dimensions that I need to adhere to. I want to use a pre assembled crossover so I can just build an enclosure and assemble the speaker. I don't want to make my own crossover.

Now to the question.

I need to know what the impedance of my tweeter and woofer should be to have an overall impedance of 8 ohms.

Hope this helps

Thanks!

GVSS

[ch83575]

The answer is different for speakers connected to a crossover as opposed to "wired in parallel/series". If your drivers are attached to a crossover the system impedance will not drop much below the impedance of the driver within that drivers passband... as long as the crossover is well designed. So, if you have a single 4 ohm woofer and 6 ohm tweeter you could very well design a crossover that does not drop much below 4 ohm in the mid-bass and then climb to a nominal 6 ohm in the treble.

The confusion arrises when you are sending the same signal to two drivers. Then you use the same technique as determining series/parallel resistances (add in series, 1/r1+1/r2=1/r_eq in parallel). Nice thing about speakers is that you are usually paralleling two of the same thing, which is equivalent to 1/2 of the original impedance. So, if you have two 4 ohm woofers wired in series and a 6 ohm tweeter your final system impedance could easily be 8 ohm in midbass dropping to 6 ohm in treble. Again, it also depends on crossover implementation, but these are the basic ideas.

Hope that helps,
Chad

[ch83575]

Basically I'm trying to build my own center channel speaker to fit into my entertainment center, so I have specific dimensions that I need to adhere to. I want to use a pre assembled crossover so I can just build an enclosure and assemble the speaker. I don't want to make my own crossover.

Now to the question.

I need to know what the impedance of my tweeter and woofer should be to have an overall impedance of 8 ohms.

Hope this helps

Thanks!

GVSS

Sorry to be the one to do this... some people take it as a bit of a let-down, but here it goes: no amount of careful speaker selection will ever make a stock crossover sound great. I say great because sometimes with really well behaved drivers it could sound ok, but never great. If you don't want to design your own crossover you should look at the designs on this website in the missions accomplished section. If you don't even want to build the crossovers (afraid of burning down the house with the soldering iron... or maybe the fumes) you can even buy great kits with crossovers already assembled from madisound. Its kind of the party line around here, but people say it for a reason: if you aren't going to invest a lot of time, energy and money in designing your own custom crossover you are best served by building a finished design by a competent designer.

I hope you enjoy your first build.

-Chad

[ThomasW]

+1

Use of generic crossovers is a bad idea. If you don't want to design your own, build a proven design from a known designer.

[---k---]

Paul's site has several good resources for people considering building their own speakers for the first time:

http://sites.google.com/site/undefinition/diy