Crossover design for 2-way 3 driver system

Hi,

I'm planning to build some speakers using two 5.25" woofers and a dome tweeter in each box. The woofers I have are 8 ohms, and I have two types of tweeters to choose from. One pair are 6 ohm, the other are 8 ohm.

My question is about wiring the two woofers to the crossover.

What's the best way to connect the woofers if I want the system impedance to be 8 ohms? In series the impedance doubles, in parallel it's cut in half, correct? Should I have bought 4 ohm woofers and then connect them in series? Is there a way to do it with 8 ohm woofers?

The woofers are Peerless Vline BC14WG79-08.

Should I use the 8 ohm or the 6 ohm tweeters, or does it matter? The 6 ohm are the better drivers, they are Vifa D25AG77-06. The 8 ohm are Vifa D19TD-05-08.

Any help or advice is appreciated.

Thanks.
 

Pano

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Paid Member
2004-10-07 6:05 am
Panama
Hi and welcome to the forum.

Is there a reason you need an 8 ohm load? Does your amp or crossover need it? If not, then go with the 2 woofers in parallel for a 4 ohm load. This will have many advantages. In theory you may end up with a higher SPL out of the 2 paralleled woofers than those tweeters, (at a given voltage) but once crossover and baffle losses are taken into account, you should be darn close.
 
I think you are stuck with 4 ohms speakers, speaker systems that is.

There is no way to make two 8 ohm speaker equal 8 ohms. Four is easy enough, nine is easy enough, but not two.

Still if we assume you have a half-way decent stereo amp, and one of a few good AV amps, a 4 ohms speaker should be no problem.

Next, are you designing the crossovers, or are you buying them off the shelf?

I would suggest against buying them. When you get this you are stuck with somewhat generic values.

Since you have decent drivers, you can look at the spec sheets and determine the impedance at the crossover point and use that as your design parameter.

Also, no reason why the woofer and tweeter can't have different impedances, you just have to design the filter/crossover that effects a give driver to match the impedance of that given driver. In you case, a combined 4 ohms on the bass, and 6 ohms on the tweeter are not problem, just design each section for the associated impedance.

Steve/bluewizard
 
Awesome, thanks for the info!

Right now I'm using a vintage Superscope A-260 stereo amp. I'm not 100% sure if 4 ohm speakers are ok with it or not, but I plan to buy something else soon, so I'll make sure it's ok with 4 ohm speakers.

I'm going to design the crossovers myself. I won't even consider buying off the shelf.

I have some test equipment (VTVM, digital LCR, Audio Generator), a book on speaker building, and some software to do the calculations, so I should be ok.

Thanks for those links streten, there's some great info there. Many of those sites I would have never found just by searching the net myself.