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Old 16th December 2012, 07:00 PM   #1
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Default Stargate

In this thread I'm going to document another 'quick and dirty' project of mine.

Here are the goals of this project:

1) Good phase coherency. I think this is important as it improves articulation. And when you improve articulation, voices are easier to understand, percussion sounds more realistic, and it seems to reduce listener fatigue.
2) One of the odder aspects of this project is that it will have two stereo channels in one enclosure
3) Efficiency should be a bit higher than normal. As usual, it's going to be horn loaded.
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Old 16th December 2012, 07:06 PM   #2
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Some of you may have noticed that the titles of my threads usually have nothing to do with the speaker that's documented. The reason that I do this is that it makes it really easy to look up old projects. (It's a lot easier to remember the name of a thread like 'Square Pegs' or 'Sunshine' than Twelve Inch Woofers In My Dash - CARSOUND.COM Forum)

The name of this thread is a tip of the hat to Eugene Jarvis, one of my computer programming heroes. In an interview (Eugene Jarvis) he talks about how Stargate was an evolution of Defender. This project, obviously, is an evolution of some of my loudspeaker projects. BTW, the interview is lulz, here's one of my favorite quotes:

"After "Defender," Williams' first video game, came out and was such a huge hit, management decided that if one team could design a huge hit, 100 teams could design 100 hits. It was basically the monkey and typewriter approach to game design. So a huge new facility was constructed--Kedzie--with a beehive of offices. Since the edict went out to staff up quickly, an army of warm bodies were hired. Whereas I designed "Defender" in an abandoned factory in complete isolation, now I was subjected to twenty stereos playing "Disco Duck," all the while gagging on Cannabis fumes from the turned-on masses."

(I'm a programmer in my day job, so I find Jarvis' observations about the tech world amusing.)
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Old 16th December 2012, 09:52 PM   #3
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'stargate' is basically a VTC Paraline, sliced in half.

Click the image to open in full size.
Click the image to open in full size.
this is a Paraline

Click the image to open in full size.
This is a stargate. I'm only showing one half of it; in my car it's mirrored, with two stereo channels in a cabinet that's about 50cm wide.

In the pic, we see the following:

1) it's a Paraline sliced in half
2) There are two reasons that it's sliced in half:
a) a Paraline gives you narrow directivity in one dimension, and wide directivity in the other. For instance, it's possible to get directivity that's close to 180 degrees in one dimensions, but zero degrees in the other. This is handy for 'underdash horns' where we want narrow vertical directivity to reduce reflections off the car doors, but wide directivity to allow the horn to be placed a couple feet lower than optimal. (Optimally, it would be at ear level, on the dash.)
b) my 'stargate' has two stereo channels in one chassis, so we want very narrow directivity to keep the left from 'bleeding' into the right
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Old 16th December 2012, 09:56 PM   #4
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some pics of it coming together:

Click the image to open in full size.
I printed the stargate on my laser printer. Basically just print it, then copy it to the plywood horn

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Click the image to open in full size.
My girlfriend says it looks like a pair of boobs :P

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Click the image to open in full size.
It's about an inch thick

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My favorite way to line up the throat of a horn. A plexiglass mounting plate. Thanks to Geddes for the idea.

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Here's a pic of the device, to give it some scale. Those are 5cm midranges.
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Old 16th December 2012, 10:03 PM   #5
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Been watching all things Unity, Synergy, Paraline for a few months now. I am very interested in this build. I always look forward to your post, there is always something special happening in your builds. I often wonder if I think about all these ideas, what type of information overload your brain must stay in!

Revolution!

Steve
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Old 17th December 2012, 03:09 AM   #6
Bare is offline Bare  Canada
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Interesting notion. But the Headphone sized drivers of clearly inexpensive mfg Don't seem promising or even IMO worth the effort of even chopped up door skin ply.
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Old 17th December 2012, 04:09 AM   #7
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Quote:
Originally Posted by Bare View Post
But the Headphone sized drivers of clearly inexpensive mfg Don't seem promising or even IMO worth the effort of even chopped up door skin ply.
We know, we know... nothing less than a 15" Tannoy can possibly do the job.

dave
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Old 17th December 2012, 04:42 AM   #8
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Quote:
Originally Posted by Bare View Post
Interesting notion. But the Headphone sized drivers of clearly inexpensive mfg Don't seem promising or even IMO worth the effort of even chopped up door skin ply.
Probably one of the trickiest challenges in a Unity horn is getting the woofer to mate up with the midrange. If your mid is too big, you get a trough in the response around 1500hz. (Check out the thread 'suitable midrange for unity horn')

That leaves a couple options:

1) use a big compression driver and cross over low

or

2) use very small midranges

I prefer option 2. If you use a 'conventional' compression driver, it tends to roll off around 16khz, and I prefer the 'sparkle' you get with smaller compression drivers like the CDX1-1425

If you have the space, option 1 is perfectly viable.

Unfortunately, this opens up another can of worms, which is that you need a larger internal height in the Paraline, which rolls off the highs. (Which are *already* rolled off due to the choice of a larger compression driver.)

Long story short, I like option two.
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Old 17th December 2012, 11:10 PM   #9
winslow is offline winslow  United States
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Bummer, thought you were going to use the 18Sound drivers like VTC uses.
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Old 18th December 2012, 01:57 AM   #10
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Stargate sound from my Williams Black Knight works fine,
but the voice board intermittently drops part of words.

Last edited by kenpeter; 18th December 2012 at 01:59 AM.
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