seas woofers and vifa tweeters, attenuate tweeter? - Page 2 - diyAudio
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Old 15th May 2012, 09:21 PM   #11
sreten is offline sreten  United Kingdom
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Location: Brighton UK
Quote:
Originally Posted by Rijaak View Post
Tmi. I dont have a degree in electrical engineering. Just a what my punch-card
computer designing father taught me growing up. It might help if I mention that
the enclosure Im thinking of is a 0.8 cu ft ported with polyfill and one tapered
3" port with 1.75" diameter.
Hi,

0.8 cuft vented will work with two L18's but somewhat bigger is a little better.
Still your heading towards a very poor speaker if you don't design it properly.

The planned x/o is appalling bad, totally wrong, and will sound hideous.

A very sad fate for $400 worth of very good (used properly) bass/mid units.

rgds, sreten.
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 15th May 2012 at 09:30 PM.
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Old 18th May 2012, 07:12 AM   #12
Rijaak is offline Rijaak  United States
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ok I've been trying to design a xover using passive crossover designer. I need to find the zma and frd files for the seas. I tried making my own, but something's wrong with the zma.
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Old 18th May 2012, 07:58 AM   #13
Rijaak is offline Rijaak  United States
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Okay here's the modeled frequency response of the new cross over that I designed. Its a two-way with the seas hooked up parallel and fourth orders. ImageShack® - Online Photo and Video Hosting

How does it look?
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Old 18th May 2012, 11:50 AM   #14
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Much better than the bose crossover! Still, I think it's too low for that tweeter. You should try again with atleast 2khz, 4th order.

Can you post some more screen shots of components you are using for the woofer and tweeter in PCD, phase etc? Did you model the baffle step and diffraction for the drivers?

Last edited by samadhi; 18th May 2012 at 11:58 AM.
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Old 18th May 2012, 12:33 PM   #15
sreten is offline sreten  United Kingdom
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Hi,

As Zaphs x/o is near 4th order L/R acoustic at 2KHz, (its slightly asymmetric
to make the vertical dispersion more symmetric), a good idea would be to use
the low pass section as is and modify the high pass to suit.
Hard to think of a better topology you could use. Electrically the high pass
is second order and the low pass is a 3rd order elliptical (Caeur) filter.

Seas
Click the image to open in full size.

Vifa
Click the image to open in full size.

The more extended low response of the Vifa needs a lower Q 2nd electrical filter
and you'll probably have to shift the electrical x/o point higher for the same target.
The L-pad for both is similar, perhaps R9=4.7R for the Vifa.
You may have to add a tweeter impedance peak compensation circuit.

Vifa distortion
Click the image to open in full size.

You should be OK with 4th order L/R @ 2KHz. Clearly trying to
go lower than 2KHz with this tweeter is counter productive.


rgds, sreten.

For info here is the Seas distortion
Click the image to open in full size.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 18th May 2012 at 12:51 PM.
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Old 18th May 2012, 01:43 PM   #16
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Quote:
..a good idea would be to use the low pass section as is and modify the high pass to suit.
Good idea indeed
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Old 18th May 2012, 02:43 PM   #17
Rijaak is offline Rijaak  United States
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Revised crossover ImageShack® - Online Photo and Video Hosting
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Old 18th May 2012, 02:46 PM   #18
Rijaak is offline Rijaak  United States
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I know that I'm crossing over the tweeter even lower now, but why is that bad? I thought the whole point was to get the flattest response curve possible.
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Old 18th May 2012, 02:55 PM   #19
Rijaak is offline Rijaak  United States
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The low pass was designed for bose 6.5" woofers, not the Seas. I thought that I could still use it before I learned more about how crossovers operate. (thanks for the links guys, I learned alot.) If I could get some more advice on why and how it needs improvements (in layman's terms please. Sreten I appreciate the help, but don't know enough yet to understand.) Also, what's baffle step defraction and how and why do I need to model it?
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Old 18th May 2012, 02:56 PM   #20
Rijaak is offline Rijaak  United States
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Also, whats all this about phase. It keeps coming up, but I don't understand.
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