The Joudas project

[trevordj]

Your acoustic phase alignment with this xover is not so good.

Wolf

Thanks Wolf, how about this one?

[trevordj]

I think maybe the wave-guide is affecting the woofer response. You can compare factor data maybe and see, or place something over the wave-guide, and remeasure.

With the sealed box response I posted above, the woofer is in a completely separate box from the waveguide. The response looks weird to me too... I don't know how to make it look not weird though.

[rpb]

With the sealed box response I posted above, the woofer is in a completely separate box from the waveguide. The response looks weird to me too... I don't know how to make it look not weird though.

I just looked at PE measurements, and it appears to be the woofer.

It would take more parts, but sometimes adding a notch makes things easier. Not always though. On the woofer... Try a notch using 2mH, 40uf, and about 10 ohms, in series with each other, and across the woofer terminals. Part values are WAG starting point. Experiment! Might be a waste of time though. Center the notch around 1k. The rest of the woofer xo will need to be changed a lot with the added notch.

[trevordj]

I just looked at PE measurements, and it appears to be the woofer.

It would take more parts, but sometimes adding a notch makes things easier. Not always though. On the woofer... Try a notch using 2mH, 40uf, and about 10 ohms, in series with each other, and across the woofer terminals. Part values are WAG starting point. Experiment! Might be a waste of time though. Center the notch around 1k. The rest of the woofer xo will need to be changed a lot with the added notch.

Alright, I messed with it a bit, how does this look? How much phase alignment should there be at the crossover point? Also, should I be worried about that on axis rise in output above 10k on axis?

[rpb]

Getting tough for suggestions. Here's a WAG. Just think of it as practice. I may be barking up the wrong tree. Add a 2 ohm resistor in series with the 20.8uf cap. See if that will soften the shape of the woofer roll-off a little. Or.. try a 3rd order filter on the tweeter. I'm guessing, so...?

[trevordj]

Getting tough for suggestions. Here's a WAG. Just think of it as practice. I may be barking up the wrong tree. Add a 2 ohm resistor in series with the 20.8uf cap. See if that will soften the shape of the woofer roll-off a little. Or.. try a 3rd order filter on the tweeter. I'm guessing, so...?

I’ll keep playing with it.

I put together the ported boxes tonight. I’ll let them sit in the clamps overnight. The box turned out really nice. -Trevor

[trevordj]

lol, well there is always this...

[Wolf]

Do not use this last network. That 44 ohm resistor and 0.26mH coil will be across the amplifier outputs and the resistor will get HOT. The phase was better in the first one after I mentioned the phase alignment than the 2 following.

Later,
Wolf

[trevordj]

Do not use this last network. That 44 ohm resistor and 0.26mH coil will be across the amplifier outputs and the resistor will get HOT. The phase was better in the first one after I mentioned the phase alignment than the 2 following.

Later,
Wolf

Thanks Wolf! That last network was posted mostly as a joke.

[Wolf]

I don't know why it's a joke, as I've done similar before. More parts are not always a bad thing.
Wolf

[trevordj]

I don't know why it's a joke, as I've done similar before. More parts are not always a bad thing. Wolf

The notch filter I put on the tweeter is centered around 13kHz mostly as the joke. Granted, half of me thought maybe I had stumbled onto something that might work. As you know, I have zero experience building passive crossovers so when, for example, someone like you looks at a crossover network and can tell from the schematic that something will get hot I have zero clue why that is. It is super intimidating posting this stuff when there is 100% chance of looking foolish. I’m having fun learning though and I do appreciate your experience and input. -Trevor

[a4eaudio]

I don't think you look foolish at all. You look like someone trying to design their first crossover who acknowledges they need help.

[rpb]

The notch filter I put on the tweeter is centered around 13kHz mostly as the joke. Granted, half of me thought maybe I had stumbled onto something that might work. As you know, I have zero experience building passive crossovers so when, for example, someone like you looks at a crossover network and can tell from the schematic that something will get hot I have zero clue why that is. It is super intimidating posting this stuff when there is 100% chance of looking foolish. I’m having fun learning though and I do appreciate your experience and input. -Trevor

That's why you should post these x-overs. You will learn more! No one will think less of you. In fact, a large percentage here can't do their own xo.

There's a handful of tricks that come in handy, but they may not be used by many. There's a hundred ways to do a speaker xo. The trick is finding the best compromise. There is no best x-over really. Some are clever. Some are complicated. Some use a minimal number of parts, but would be better with more parts. Sometimes it's a budget compromise. sometimes it's a small box, and room is scarce. I hate small speakers. There's no room for a 12 part xo!. Well, there is, but it's harder.

[trevordj]

Ok guys, some more updates for today. I cleaned up the boxes after glue up and got the drivers and ports mounted.



I also wanted to try a different iteration of the XT25 tweeter in the horn. I forgot I have two XT25SC90s in storage. I read something about removing the flange so I went for it. The first one, I ruined. The second one was a success though.



I drew up a 3D model of a mounting bracket in Fusion 360 and cut it out.




Using this will allow more flush mounting in the horn throat. I’m hoping that will help with some of the measurements. I read a thread on here where this exact tweeter was used in this waveguide with good results. -Trevor

[trevordj]

I took some measurements in the ported box with the different tweeter.



Woofer looks as expected, ugly above 1500hz. Measurements are at 0, 30, and 60 degrees





Tweeter looks better in my opinion, the ringing/cone breakup/horn honk above 10k is gone.

[trevordj]

I came up with a couple crossover sims, I am interested in your feedback. The first is complicated but has good phase alignment and manageable impedance across the board.



The other crossover has more even directivity but lower impedance and less optimal phase alignment on axis. At 30 and 60 degrees phase alignment looks good though.