Crossover Help - Epique & BZ Project

[jml]

Happy Holidays All!

I got around to taking some measurements for my Dayton Epique and BZ project over the past couple days. I spent a few hours doing some modeling in XSim, and it's clear that I'm going to need some help from the experts here. I've come up with a couple designs that get a decently flat response, but am consistently running into the same few problems:

1) Impedance dips below 4 ohms at 3khz and above
2) a lot of noise in the overall frequency response at both crossover points
3) I've been able to tame the peek on the E160CF with a notch filter (or by rolling it off with a 3rd order filter), but I keep ending up with it crossed very high (like 5-6khz). It seems like whenever I pull the crossover point lower, I run into both FR and Z issues.

If anyone is interested/willing to help out with some modeling, I'd love to be shown what I'm doing wrong hahah! Attached are the measurements. These were taken on-axis from 1M with the "blended" omnimic option.

Thanks in advance for the insight!

Joe

[jml]

5 file limit per post, here is the FRD for the woofers.

[Wolf]

It's the tweeter. They have an unusual impedance profile. Your best bet is to attenuate them with at least a series 2 ohm resistor.
Wolf

[DeZZar]

Can you provide the positioning of the drivers on baffle and the on axis measurements of each of the woofers, along with individual woofer ZMA?

Do you have off-axis measurements for all drivers out to 90 degrees?

[jml]

Thanks for the feedback! I tried adding in a resister on the tweeter network, and it did help with the impedance at the higher frequencies, but didn't deal with the dip at 2-3khz. Plus, I think I'm going to need all the output I can get out of the BZ.

Regarding addition measurements. I did not measure each of the 4 epique subs individually - would that add a significant benefit over measuring the summed performance after they're wired up? I will try and do some off-axis measurements this week and post.

Below is the current state of the crossover. I've got the crossover points where I want them. I cleaned up a lot of the noise at the mid/tweet crossover by inverting the tweeter polarity. I scrapped the notch filter in this version, because the mid is attenuated so much at 4-5khz that it wasn't necessary anymore. I still haven't solved the impedance dip at 2-3khz.

I've attempted to attach the XSim DXO file here by changing the file extension to PDF. You should be able to download it and change it back to DXO to open in XSim.

Cheers!

Joe

[Wolf]

The dip you have at 2.3k is the sum of the 30uF and 0.1mH resonance. I would try flipping the 5.6uF and 30uF places.

The mid breakup is only down about 10dB, so this needs to be notched to hit the -25dB minimum or -40dB better point.

Wolf

[Chris Roemer]

Try this in your software (all 2nd order):
Ribbon HP: 6uF series cap, 0.50mH shunt coil (to gnd) - can't really seem to afford any attenuation due to quad woofers
CFmid bandpass: 0.50mH series coil (w/a "tank" across the coil - being 4ohm resistor in series w/a 1.5uF cap) followed by the OTHER series component - a 68uF cap, then both shunts: 6mH coil, and 4uF cap - so far, no attenuation on mid either?
Quad LP: 8mH (cored) series coil, and a 47uF shunt cap (to ground)

Some softwares won't allow the BP components to run series-series-shunt-shunt BUT, it SEEMs to me (over the years) that this can help prop up the impedance - not sure exactly why.
Fcs near 400 and 3kHz. Z should stays mostly above 5ohms (pretty flat, too).
Not w/out its issues, but maybe another starting pt.?

[rpb]

What Wolf said! That's trouble leaving it as shown.

[jml]

Try this in your software (all 2nd order):
Ribbon HP: 6uF series cap, 0.50mH shunt coil (to gnd) - can't really seem to afford any attenuation due to quad woofers
CFmid bandpass: 0.50mH series coil (w/a "tank" across the coil - being 4ohm resistor in series w/a 1.5uF cap) followed by the OTHER series component - a 68uF cap, then both shunts: 6mH coil, and 4uF cap - so far, no attenuation on mid either?
Quad LP: 8mH (cored) series coil, and a 47uF shunt cap (to ground)

Some softwares won't allow the BP components to run series-series-shunt-shunt BUT, it SEEMs to me (over the years) that this can help prop up the impedance - not sure exactly why.
Fcs near 400 and 3kHz. Z should stays mostly above 5ohms (pretty flat, too).
Not w/out its issues, but maybe another starting pt.?

Chris:

My sincere thanks for the suggestion! Below is the modeled result - assuming I followed your instructions correctly. This definitely cleaned up the issue with impedance, I have not attempted to optimize the FR in this at all (yet). I'll play with this topology a bit and see what I come up with.

Thanks again!

Joe

[rpb]

Try flipping the polarity of the mid-range.

[jml]

Try flipping the polarity of the mid-range.

Yep, flipping the polarity addresses the nulls. Flipping the mid created a lot of “noise” in the midrange, but I was able to address the woofer null by adjusting values, and the tweeter null by flipping the tweeter polarity.

is there any unintended consequences of flipping the polarity?

Cheers!

Joe

[jml]

below is a tweaked version that cleans up some of the FR issues from the prior post. I have 50% of the components to build this crossover already laying around, so I'm going to order the rest and do some listening and measurements.

Cheers!

Joe

[jml]

Greetings!

So I received the crossover components, and wired everything up. It was immediately clear that the midrange and tweeter were completely overpowering. I grabbed the Omnimic and confirmed that they were running as much as 10db over the woofers. I thought perhaps I had measured the woofers at a different volume level by accident when I did the FR sweeps, so I took new measurements of the individual drivers, and they showed the same thing - that no padding should be necessary on the mid/tweet, and in fact, that the woofers would potentially overpower the mid/tweet. In reality, I needed quite a bit of padding to get the mid and tweet aligned and flat with the woofers.

I'll post the current FR graph in a bit. Any ideas what I may have done wrong with my individual driver measurements? Do the different test tracks potentially ahve different volume levels? I used the ful sweep and then the base removed sweep for the tweeter.

Cheers!

Joe

[jml]

Here is the FR plot on axis with the padding and a few other adjustments in place. I’ve also included a picture of my mess of a test rig. My wife has informed me that I can no longer use the office as my workshop, and I need to move to the basement haha!

Joe

[jml]

Good Evening!

I've been doing a lot of tweaking with this project over the past few weeks. I've built a few variations that sound (and measure) OK, but still don't feel like I've gotten it perfect. I took some new measurements today and tweaked the previous crossover design quite a bit. What do you guys think about the below?