2 way crossover design help

[ODougbo]

Always looking for good drivers that don't cost $100 each.

Peerless/Vifa/Morel have been good so far. I had a pair of Seas Prestige that were trouble (could have been something else I guess).

SOOO many driver to chose from, hard to pick one!

[balerit]

In my opinion all drivers are the same, I currently use el cheapos in my Camm DynaTones and they work well, it's how you test and use them that counts.

Voigt Pipe, DIY Tapered Quarter Wave Pipe (TQWP) loudspeaker plans - The Book Worm

[ODougbo]

Well I guess they are all the same in a global sense.

So your speakers remind me of some subwoofers - check posts 301 - 310:

Isobaric - less then $20

[wolf_teeth]

Originally Posted by balerit

The morel of the story is never mix speakers with different impedances and keep the woofer and tweeter sensitivities the same.

I'm sorry, but this is not a good rule of thumb. Mixing different voltage sensitivity and impedance is fine.
Later,
Wolf

[ODougbo]

Thanks Wolf,

I see that a 8ohm tweeter would need a smaller cap (1/2 the size of 4ohm)

2-Way Crossover Designer / Calculator

Is that all I need to change in the xo designed for the 4ohm tweeter?

[balerit]

Originally Posted by wolf_teeth

I'm sorry, but this is not a good rule of thumb. Mixing different voltage sensitivity and impedance is fine.
Later,
Wolf

Well then you are discounting 50 years of research by the top people in their field and it's statements like this that make a mockery of High Fidelity.

[system7]

A mockery indeed. Or not. Let's get back to ODougbo's speaker.

It does seem to me this is a very high inductance woofer. 0.8mH is a LOT for a 4 ohm unit. Usually you'd be around 0.4mH here.

It's gonna fight anything you do to roll it off with a small bafflestep coil.

That means you get a midrange peak when you add shunt capacitance unless you filter it very low. So you need some shunt resistance too.

My experience with high-inductance woofers is they filter best with a simple coil or a coil plus a Zobel, which here at 3.7R and 0.8mH is 4.7R and 35uF.

You then get left with a natural rolloff around 4kHz and a need to bring the treble in quite high at 4kHz.

Something to ponder. system7!! Steve!!

[ODougbo]

Steve,

Ahhh the plot thickens...I'm sure the woofer/tweeter xo is below 2K (but will check) The XT25TG30-04 says it goes to down to 1,500.

btw, back in the day when we made a bunch of these, we used a simple 6 db slope with a .7 coil (for the woofer).

Zobel network - is diagram correct?

I have the parts, large caps & resistors.

Thank you again

[system7]

Yup, the bass filter is right. Whether that sounds right is a matter for trial and error. The treble filter would need adjusting either for low slope or a high crossover frequency. It seems the polycone bass will have a natural rolloff around 4kHz.

The reason I complicated the issue is you were following my suggestion of reducing the crossover shunt resistor. Well, that might not work with a high inductance woofer at 3-4kHz, which yours is.

I think I would have to do some modelling with a suitable 4 ohm 0.8mH driver to see how it all works. My comments may not have been entirely helpful until that is done.

Usual random pictures...

[wolf_teeth]

Originally Posted by balerit

Well then you are discounting 50 years of research by the top people in their field and it's statements like this that make a mockery of High Fidelity.

Look around, mixing these considerations is done all the time, it's not just me.
I wouldn't for tube-amps, but that's a different story.
Later,
Wolf