Unity Horn - budget drivers, active x-over

[chrapladm]

That would be awesome and I look forward to his 6 driver design. Under 24" is awesome.

[jmorken]

Oofda! It's been a crazy few days at work and coming home to fiddle with the this project has been a lot of fun.

I tried a bit more filler using modelling clay and gave it a shot. It looks pretty good. I did power response measurements measurements every 5 degrees and it looks to have excellent constant directivity EXCEPT directly on axis (raw HF response, measurements are offset for clarity). At about 4khz there is a dip on axis that is not evident anywhere else. Perhaps this a result of using a compression driver with a convergent phase plug design rather than spherical. Are there any free tools available to make those fancy polar plots?
The crossover was tricky. You're right Tom, having more overlap would have made things easier. I ended up pushing the D220ti's down to a 1200hz 2nd order BW filter. The mids use a 1st order filter for high and low pass. I'm curious what kind of filters Red Spade is using in his design.

I set it up with an old Peavy 15" bass cab I had around and a behringer active crossover. This crossover setup didn't match great, but it was fun to listen to. The first thing I noticed was the transient response. I'm a drummer, and this is the closest I've heard recorded drums sounding like the real thing. I was battling all sorts of noise going pro +4 line level gear to the -10 minidsp back into +4 pro amps so that kind of spoiled things. For reference, I have a home studio with JBL LSR4328P monitors in a well treated control room. I'm excited to get them setup properly in my living room.

I have two pairs of 15" woofers That I've been holding on to: EV EVM15B-Proline's and McCauley 1560B's. The EV's are more efficient, the McCauley's go lower. Over the next few weeks I'll be finishing both horns and ordering another MiniDSP to properly manage the 15's and eventual do a multisub setup.

[jmorken]

Originally Posted by chrapladm

What were the external dimensions of the horn? Sorry if you said it already.

I have a sketchup model available here. My dimensions are based on information available here.

[chrapladm]

I clicked on the link and it sent me to the sketchup web page from google. Cowans link worked fine. Have always wanted to try one of these builds but it seemed to complicated.

[rvrazvan]

Nice! Trial and succes method always gives good results.
Can you imagine an unity horn with a AMT hf driver, rather then a compression driver ?
I think that would be the ultimate unity horn

[jmorken]

Originally Posted by chrapladm

I clicked on the link and it sent me to the sketchup web page from google. Cowans link worked fine. Have always wanted to try one of these builds but it seemed to complicated.

Derp. Here's the zipped sketchup file. I guess there is a time-out for editing posts.

It's not super pretty, but it's useful. The important thing was generating the dimensions and miter angles for each piece.

[chrapladm]

Thanks for that. The building process I think I could handle but drilling the correct size holes for said drivers seems like that would take me a very long time to figure out.

[jmorken]

Some corrections (now that I'm not watching a movie and posting at the same time):
-The power response plot is both drivers with an earlier crossover. No EQ.
-I used an LR24 for the HF crossover, not a BW12.

I'll probably fiddle some more to get a lower order HF crossover to work. It will end up asymmetrical as I think the LR24 HF is the closest match to the Mid's slope with its 1st order filter.

[NYCOne]

Originally Posted by jmorken

At about 4khz there is a dip on axis that is not evident anywhere else.

I'm definitely not the guy to comment on the 4KHz issue expertly, but I'm obsessed with building a set of these horns and I came across this excerpt from another thread:

"When the new horn shape that Nick used was made, it also took a bit to get the kinks figured out. Where the mid holes are, there is a small impedance discontinuity (due to the change in cross section), making the holes as small as possible makes this as small as possible. At about 4 KHz, that location in the horn is governing the directivity in the 4 KHz area and that causes a reflection. This reflection causes the dispersion pattern to widen temporarily at 4 kHz which because the acoustic power spread over a wider angle produces a "hole" (the notch you saw) exactly on axis. This notch is not present off axis fwiw. The reflection can be eliminated (or at least its effects once the sound exits the mouth) by placing 4 small foam absorbers at the right location on the mouth and then the dispersion and amplitude response at 4 kHz are "fixed" without other impact. Even when not "fixed" the effect is minor and a narrower slice in frequency than one can discern."

It's attributed to Tom.

[Tom Danley]

NYCone posted a quote about the dip;

While I don’t remember saying that precisely, it is right and like I explained somewhere here, he had filled in the corners more than we did. It would be worth going back and examining the shape of the upper range as you add the corner fill, while having a lot looks good, you may have gone past the optimum amount.

Jmorken, what are you using to figure out the crossover for these?

Remember when you have the crossover right, there is no (or little) phase shift through crossover, it looks like a single driver.
Best,
Tom