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Morel "Duet Fortissimo": Because I need another project!

baco99

baco99

AK Subscriber
Subscriber
So, many of you know about the "fire pile rescue of 2013." These Morel Duet cabinets were part of that rescue mission. After a few months of assembling parts and looking at options, I finally started this custom Duet project that I am calling the "Fortissimo."

These cabinets feature some rebuilt Morel MDT-30 tweeters. New voice coils installed and new ferrofluid.

The woofers are Morel HU621 which are not ideal for this small sealed enclosure, but are very close to ideal. I picked them up from another AK member along with crossover plans

The crossovers feature Dayton audio Caps and air core inductors for a 6 DB/octave crossover at 3000Hz.

If all sounds well, the cabs will get refinished completely. I just got one side completed last night and soldered up the other crossover this morning. So far so good!

Hoping to hook up with thedelihaus to compare his factory correct Duets with the Fortissimos.

What do you all think?

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halo71 said:
Great looking cabinets! I wish those were on my projects list!
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The cabinets need a little work. Remember, these were haphazardly thrown into a giant pile of brand new speaker boxes. Luckily, these were at the very bottom of the pile, covered with a tarp and protected by a massive pair of JBLs that were left to rot.

There's some very minimal swelling on the bottoms, and some dings to the veneer, but very serviceable.

The crossover boards were salvaged from a set of Morel MLP-501 cabinets that were completely water logged save for the crossover boards. All of the crossover components are new, just using the old boards and binding posts.

The box is a very interesting shape. They angled the bottom so that the face is canted a few degrees back for time alignment.

I plan to finish #2 this morning.

The real Duets, in Cherry, sell for $2500/pair!!!!
They use a Morel MDT-33se tweeter and MW-167 woofer.
http://www.renaudio.com/homeaudio/Duet.htm

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Quick update!

I got both speakers assembled, crossovers done, woofers have been countersunk to sit almost flush with the face of the cabinet. I haven't refinished them yet, but I want to demo them for a while first.

First impressions after assembly were that the high end was WAY too laid back. The 4.7 ohm resistor ahead of the tweeter on the crossover was probably too high of a value. I changed the 4.7 to 1.1 ohm on one speaker and compared the two. Night and Day difference. The high end opened up considerably. The whole speaker has better balance. The tweeter voice coils are new, with new ferrofluid. I think with some break-in on the whole setup, things will be sounding pretty good.

Once both speakers had the 1.1 ohm mod done, I auditioned them together and I am very happy with where this project is headed. I have no idea yet whether these sound like real Duets or not, but they certainly sound like "monitors". Very balanced, calm-cool-collected type of sound. Nothing is overdone and every intricate detail of the music can be heard.

I'm very excited to hook these up to the main system, no subwoofer, and give them some real power and real volume.

Anyone have any music suggestions for a speaker like this? What's really going to make them shine, and also show their flaws?
 
baco99 said:
I have no idea yet whether these sound like real Duets or not, but they certainly sound like "monitors". Very balanced, calm-cool-collected type of sound. Nothing is overdone and every intricate detail of the music can be heard.
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Excellent. Just how they should be. :thmbsp:
 
By now, many of you are familiar with my living room.

First listen!

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I still feel that the high end is attenuated too much. Might lower that first resistor from 1.1 ohm to 0.55 ohm to open things up more at the top.

But the overall detail and balance is incredible.


Also, the stands are maybe 4-6" too high, but they are fantastic pieces. DP Audio from Denmark, sand filled.



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Hey! Just wanted to offer a quick update. I noticed some "bottoming out" on the low end when pushed hard and asked for some help at diyaudio. Those guys have been a huge help in allowing me to understand how these speakers are working.

At the end of the day, the crossover looks good, but the bottoming out issue has to do with the Xmax of the driver being only 3.5mm and it going beyond its limits under 40Hz. I am working to try to find a remedy. Options are:

1) Reduce the internal volume of the box by adding some "ballast" like bags of sand for example.

2) Port the box, as the modeling software shows this driver is more capable when ported vs sealed.

3) Add a high-pass filter at 50Hz and run a subwoofer.

4) Change drivers. The Morel MW164 or MW166 are the drivers originally used in this box, so perhaps I can source some second-hand. Or search for other brands that will work and have a higher Xmax to handle the types of music I like without a subwoofer.

Here are some simulation plots of the speaker based on the modeling software. I have not done any equipment-based testing.

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Interesting stuff! I am learning a lot.
 
cratz2 said:
They definitely get the cratz2 seal of approval! :thmbsp:
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Thanks! It's been great to give some new life to these discarded boxes. I originally set out to build myself a replica Duet, and it's turned out to be more of a one-off DIY. But they sound quite good. A little more tinkering and I'll be able to test them against real Duets.
 
baco99 said:
...

2) Port the box, as the modeling software shows this driver is more capable when ported vs sealed.
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Please, No!!!!



baco99 said:
...3) Add a high-pass filter at 50Hz and run a subwoofer...
Click to expand...


This will fill out the bottom end nicely.



baco99 said:
...

4) Change drivers. The Morel MW164 or MW166 are the drivers originally used in this box, so perhaps I can source some second-hand.
Click to expand...

I may be able to help you here my friend. I have a pair of the MW-160 woofers. The MW-160s used foam surrounds and those will need to be re-done.

The MW-160s added a rubber surround (same size surround as the 160s) and became the 164s. Cone material is the same, magnet structure a bit beefier on the 164s. Call me later.:D
 
When your stuff travels the interwebz....

Incidentally, I have some measurements of these speakers now. Need to dig them out.

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