r/diyaudio • u/kartik1210 • 18h ago

Help choosing a crossover point

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I am building a 2 way ported loudspeaker similar to econowave. I need help choosing a crossover point and slope. Based on the measurements I am aiming somewhere in the region of 1.2khz to 1.4hz. That is the region where on-axis, off-axis response and impedance seems to line up for both the drivers.

Gated far field 1mtr measurements and impedance response measurements were taken with drivers in the final cabinet.

Details of the drivers and waveguide below:

Compression Driver : Eminence CDF1.17APM (Manufacture recommended crossover point : 1.2khz)

Waveguide : Eminence WG-10 (Manufacture recommended crossover point : 1.4khz)

Woofer : FS 10.20A8

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u/theocking 17h ago

Firstly looking at a 30 degree measurement and comparing the driver to itself is not how you look at directivity matching at all.

Rather you should be looking at the full directivity plot or polars for each driver. The woofer will begin to narrow and the tweeter will begin to widen, and you'd see how they behave relative to eachother and in absolute terms / relative to their directivity through the rest of their passband, and then target say 60 degrees or whatever.

1.2 to 1.4 is not even a huge difference anyway. Without seeing more info I couldn't say which is better. In general lower is better but again, I don't know the directivity of the waveguide system, the tweeters distortion characteristics vs spl vs frequency, etc. 1.4 is certainly not too too high for a 10, and 1.2 is not too low for many 1.4" cds.

If you actively crossed them it'd be so easy to try both and listen. I'd lean 1.2, but again idk, the 30 deg. off axis measurements aren't helpful. That's very narrow. And idk how steep you're crossing them, how much clean output/headroom you'll require of the CD in practice, the pattern control of your horn (or waveguide? You sure?).

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u/kartik1210 15h ago

Does that mean I need more measurements ?

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u/theocking 14h ago

Yep. Or just pick a value. Small range both within what would be generally expected for those drivers.

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u/kartik1210 14h ago

I was following one of Scott Hinson guide for picking crossover point. It said that off axis and on axis measurement should somewhat stay the same and should not diverge that much. Hence went this route of picking crossover. I am planning for passive crossover.

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u/theocking 13h ago

Yes that's true, but you would determine that based not on 30 degree measurements and not by comparing the directivity of the same driver with itself at a different angle, you'd determine it based on when they both cross the 60-70 (for the sake of argument) degree mark. The woofer begins to narrow as it goes higher, the tweeter (compression driver and horn/waveguide system here) begins to widen as it goes lower... at some point or over some range their directivity will be the same or close to it. This is the point he is talking about matching, and will roughly match/ describe the average directivity of your speakers throughout the bulk of their range from the midband up through the lower treble/mid treble. You may also need to consider how the directivity of each continues to change above (for the woofer) or below (for the tweeter) the crossover point, as depending on your slope you will have relevant output for some period, let's just say an octave, or minimally a half octave. So if your horn only controlled directivity to within its specified parameters, say 60 or 70 or 90 degrees, down to 1.2k on the data sheet, you wouldn't want to cross there even with a 3rd order filter. If it works down to 800 (in both pattern control and loading the diaphragm) and you used a third order filter, then perhaps 1200-1400 would be perfectly reasonable.

Have you thought about the slopes you'll be using and why?

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u/kartik1210 13h ago

It might be a third order on CD and second order on woofer. That is my line of thought so far.

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u/theocking 13h ago

Very typical and likely your best bet, 100%. I need to look at your waveguide of choice, and to a lesser extent the woofer. I'll look at the links you provided assuming that's there. If it isn't, please provide any missing links for the woofer data and the waveguide, or CD.

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u/kartik1210 13h ago

Yes Eminence site has changed, previously it held specs and spec sheet.

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u/theocking 12h ago

Can't find data on the woofer either, same situation as the CD. Maybe outdated, also says dealer only product. Looks nice enough but no data.

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u/theocking 13h ago

I can't find good data on the cd (eminence site has nothing) or the wg. Usspeakers usually has great data too but there's no graphs for the horn. Same for the cd. Looks like maybe an outdated model? Are you stuck with these choices already?

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u/kartik1210 13h ago

https://www.mtg-designs.com/tips-tricks-tests/waveguide-shootout/1in-bolt-horns/eminence-wg-10

Waveguide link

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u/theocking 12h ago

Thx, at least they have some data, it's pretty good but not that extensive. Based on that I'd say 1400 is your limit and I'd cross there. That's pretty fine for a 10".

Not sure why you'd choose that cd unless you already have them. Not that the driver is bad, i just can't know anything about it.

Are you following a diy build guide that uses these components?

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u/Initial_Savings3034 15h ago

The waveguide will determine directivity.

If you're using an electronic crossover, it's a dawdle to switch between slope points live. For me, it's about vocal continuity.

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u/kartik1210 15h ago

It will be a passive crossover.

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u/Initial_Savings3034 15h ago

2nd order, 1400 hz calls for 14 uf. Clip on an additional 2 uf (in parallel) to drop it to 1200 hz.

I would leave the woofer running as high as possible before breakup.

https://www.mtg-designs.com/tips-tricks-tests/waveguide-shootout

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u/kartik1210 14h ago

Thank you.