2 way crossover design help

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Looks like there was never a second PDF for the 4ohm. Madisound sent the 8ohm sheet; they should be the same according to MS.
(same as you found Sy7)

4K! That's up there yes? Well above the xo range?
 

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It's interesting that 4 ohm speakers don't seem to have the AAL3 resonance problem at around 4-7.5kHz which 8 ohm midbass speakers have, depending on what they are made of. It does look like a notch isn't necessary with the 4 ohm units (W170S) I looked at.

Vibration analysis

That all looks very nice to me, and I don't see much more tweaking there, though the 1.5R bass resistor is possibly on the large side for a 4 ohm unit. I'll probably start with 1 ohm with hindsight. The 3R/10R attenuator is right on the Vifa XT25 given its unique properties. It does look like the time-aligned modelling tends towards first-order treble, but that would be making what Lynn Olson calls a "Little Girl With A Guitar" speaker that sounds terrible with complex music. :cool:

Enjoyed this thread. It's firmed up some ideas for me. Thanks. :)
 

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Nephew came over for the day yesterday, he's getting into speakers etc. We hooked up several pairs and these were hands down the best; maybe my set best ever!

[the Vifa tweeter is very nice - you may want to pick up a pair before the price goes up]

Nephew's a computer guru and set up the wireless TV in seconds; we moved the RCAs cables around and watched a "streaming movie " Bourn Identity

Holy Cow...I didn't see this coming but the speakers sounded like they are angry little possessed monsters, bass like a sub woofer, shaking widows, crazy sound everywhere!!

D**m shame they don't make these little drivers anymore - I know the DIYers would love these (they were only $25 each).

Thoughts on bass: I don't know, I'd be worried messing with that.
btw -, dust cap was removed and cone has silicon layer.

Still fooling around with cap for tweeter - need the bigger size(s) to bring out the detail. I'm thinking the 6uf is to large and using a 4.7uf with a piggy back 1.0uf.
(I may add a toggle switch to the 1uf).

Also need to order some new caps in the 5 - 5.5 range.
 
I used a 2.2 bass resistor in the last set - I do think I like that one better.

I'm going to order some parts today anyway - I'll get an assortment of the smaller ones.

Ended up using a 12uf cap (vs. 15uf) I don't remember why that happened..

Bolted together a third pair - the darker wood set, and going to use a Morel MDT-30 for tweeter.

Edit...Morel is 8ohm 89db - Vifa 4ohm 91db :-/











It's interesting that 4 ohm speakers don't seem to have the AAL3 resonance problem at around 4-7.5kHz which 8 ohm midbass speakers have, depending on what they are made of. It does look like a notch isn't necessary with the 4 ohm units (W170S) I looked at.

Vibration analysis

That all looks very nice to me, and I don't see much more tweaking there, though the 1.5R bass resistor is possibly on the large side for a 4 ohm unit. I'll probably start with 1 ohm with hindsight. The 3R/10R attenuator is right on the Vifa XT25 given its unique properties. It does look like the time-aligned modelling tends towards first-order treble, but that would be making what Lynn Olson calls a "Little Girl With A Guitar" speaker that sounds terrible with complex music. :cool:

Enjoyed this thread. It's firmed up some ideas for me. Thanks. :)
 
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Yikes...my HT room sounds like a dud now.

The wife and I have been listening to the pair of 2-ways for a few nights and now the 5.1 room sounds like there is no high end. I didn't see that coming....

The room with the 2 speakers has a china cabinet with a round glass door, getting a good echo for a rear channel effect (movies).

Correction to last post, the morel is the same 91db, but 8ohm; so the xo is never going to work as is.

I'll use the old 6bd xo for the tweeter; morel MTD 30 tweeter works well with a simple 3.3 cap and Lpad.
 
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. http://www.diyaudio.com/forums/multi-way/225310-system7-steve.html#post3277124
 
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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
 

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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...:)
 

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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
 
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