[Odougbo]

Hey all & Happy New Year!

In the pic is a TB W5-1611SAF, full range; however the high end is very week.

Getting good robust sound, bass/mid and would like to add tweeter to brighten them up.

The TB woofer is 8ohm-90db and have some MDT-28s, 8ohm-91db. (could order new tweeters)

I see there a host of on line calculators - this one almost seems to easy:

http://www.diyaudioandvideo.com/Calculator/XOver/

Never had much luck with xo design, but lots of caps/coils here - where to start?

I'm assuming the TB is going to need a 12db slope, since it's a full range.

Thanks in advance for any advise!

 

[robbo266317]

They are a close match in sensitivity. Do you have the specs for the 28s. I looked online but could not find them.

 

[Odougbo]

Sorry no specs on the Morel - I did look from them also...nada.

Which is hard to believe, must be a million of them out there.

Thanks

 

[Odougbo]

No luck on the Morel (again).

I'd order a new set - PE has 100+ tweeters:
http://www.parts-express.com/cat/tweeters/17

Where would be a good xo point to start? 4,000?

Sorry no specs on the Morel - I did look from them also...nada.

Which is hard to believe, must be a million of them out there.

Thanks

 

[robbo266317]

Since the other driver is full range then that would be reasonable, along with the fact that the 29 has a stated response of Frequency response: 1,800-20,000 Hz. So you could, theoretically, use a first order crossover at 3,600 Hz.

Assuming (rightly or wrongly) that the 28s has similar specs then a second or third order crossover at 4kHz would fit nicely.

 

[Odougbo]

Thinking out loud here - I do have a pair of Vifa's that I never used.

D27TG-05-06 Specs are easy to find:
http://www.parts-express.com/pdf/264-524.pdf

 

[robbo266317]

They should be good also.
Looking at their graph you could cross them at 2.5kHz and above with any order crossover.
Again 4kHz is fine.

 

[Odougbo]

The vifa tweeter (link) has a 6 component xo - is Fc[HZ] the xo - 3,500hz?

 

[Odougbo]

I did piece together a xo - it's a little scary :gulp:

I used the tweeter xo from the PDF for the vifa tweeter.

The woofer I tried different coils/caps using the 2nd order Butterwoth 2200hz.

I think the tweeter is a bit "louder" than woofer,,,btw.

 

[Odougbo]

update:

Added 4R @ Vifa tweeter (whew) The tweeter is a bit harsh, but better with attenuation.

The xo point is 2200 - easy to hear that.

They are sounding okay...some imaging.

I guess I could upgrade the parts, e.g. using small iron core bobbin(s) for tweeter.

 

[robbo266317]

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

Cheers,
Bill.

 

[SirKevi]

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 30s.pdf.
Even if you dont use these in this project it could be handy for another project.

 

[robbo266317]

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.






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

 

[Odougbo]

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.

 

[Odougbo]

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

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.

 

[robbo266317]

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

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.

:rofl: 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.

 

[Odougbo]

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.

 

[robbo266317]

Did you do the flare or is it machine done?

 

[Odougbo]

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.

 

[robbo266317]

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.