Crossovers - where to start? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 157 Old 01-01-13, 02:59 PM
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Re: Crossovers - where to start?

I'm going out for a bush walk this morning.
I will check your values if you like when I get back.

Cheers,
Bill.

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post #12 of 157 Old 01-01-13, 07:37 PM
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Re: Crossovers - where to start?

I found this out about your Morel mdt 28 tweeters. Apparently from the guy that designed them.

At this point, we decided not to sell the cabinet systems for the time being and instead began developing high quality raw drivers. About a year later my staff and I came out with our first driver design called the ‘MDT-28’ tweeter. It still is our best selling tweeter. I took this design to Meir in Israel and told him this was the tweeter we needed to sell. We decided to produce it. Now it is called the ‘MDT-30’ and ‘MDT-30s’ (these are basically the same tweeter). Around the same time, Meir, changed the cosmetics of the Dynaudio 8” woofer and Dynaudio tweeter and made them under the Morel names ‘222-D’ and ‘MDT-27’. As time passed, Meir and I developed many other drivers.

This would be the specs on your tweeters http://www.morelhifi.com/old/products/pdf/mdt%2030s.pdf.
Even if you dont use these in this project it could be handy for another project.
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post #13 of 157 Old 01-01-13, 07:43 PM
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Re: Crossovers - where to start?

It seems your values are not quite right and the attenuation for the tweeter needs to be done closer to the driver itself so it doesn't affect the total impedance of the system.

For a 2.2kHz crossover you need the following circuit followed by an L Pad to drop the level to match the full-range driver. (I have used 1dB as an example, you may need more.)

R1 and R2 are calculated in the second diagram.

Also remember to reverse the polarity of the tweeter as a second order butterworth causes a 180° phase shift at the crossover point.

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Crossovers - where to start?-l-pad.jpg

These tools are available here: http://www.apicsllc.com/apics/Misc/filter2.html

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post #14 of 157 Old 01-02-13, 02:51 AM Thread Starter
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Re: Crossovers - where to start?

moo cow! I went to the Morel site also, I thought I would have to send a email (and never hear back).

I've heard that the 28 and 30s are the same, the plate is .5mm thicker on the MDT-30.

I don't know about the Vifa tweeter...never found a place for it (never tried this hard either). It has a knee bend slope, the tweeter is off and running at 2,500hz.
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post #15 of 157 Old 01-02-13, 03:06 AM Thread Starter
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Re: Crossovers - where to start?

Aye Crumba..I needed to reverse the tweeter leads??? - I all most knew that.

I'll try the morel tweeter with this xo.

The woofer coil is .9, 18 gauge (now) using, lost some of the robust bass, I'll look for thicker wire coils and go with the 8.1mH / 6uF cap.

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post #16 of 157 Old 01-02-13, 03:26 AM
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Re: Crossovers - where to start?

Quote:
Odougbo wrote: View Post
Aye Crumba..I needed to reverse the tweeter leads??? - I all most knew that.

I'll try the morel tweeter with this xo.

The woofer coil is .9, 18 gauge (now) using, lost some of the robust bass, I'll look for thicker wire coils and go with the 8.1mH / 6uF cap.
I have done that in the past, as well as a few others....

The inductor is 0.8 mH and the lower the resistance the better.

With Butterworth crossovers the odd ones - 1st, 3rd ,5th etc are in phase.
The even ones 2nd, 4th etc are out of phase.

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post #17 of 157 Old 01-02-13, 04:44 AM Thread Starter
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Re: Crossovers - where to start?

Found some Erse 14gage, almost .8 (7.9mh)

btw, here's a pic of the ports-on-side.

[this is a different box]

I'm having a blast with these, the flares enhances the low end a bit. Can only do this with Gen, while in fabrication - i.e. trim down as needed.
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post #18 of 157 Old 01-02-13, 10:14 AM
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Re: Crossovers - where to start?

Did you do the flare or is it machine done?

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post #19 of 157 Old 01-02-13, 10:55 AM Thread Starter
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Re: Crossovers - where to start?

Odougbo is Jedi Master of tuning semi built boxes.
It works - it's fun!!


Nothing fancy here - Jig saw.

I cut the flares much closer together and then trimmed the back edge.

Clamped it all together: 4 flares and both sides & check tuning.

repeat as necessary

I think its tunned to 60hz, don't remember, whatever WinIsd came up with.

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post #20 of 157 Old 01-02-13, 11:21 AM
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Re: Crossovers - where to start?

You certainly have done a good job on it.
I gave up on using a jigsaw, except to create templates that I then finish with files and a router.

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