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PostPosted: March 4th, 2021, 5:26 pm 
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Actually the current phase. I've had these for 3-4 weeks. Originally using the DEQX for the crossover, earlier this week I finished a passive crossover for the top box. Either way, they sound great. Remarkably similar sound to the same components in a poorly designed, actually not designed, box I've been using for quite a while. The bottom is a Dayton Ulti-Max 10". Substantial output, clean and deep - f3 is about 20 Hz. The bass from the top box is better than I expected, usable output to about 35 Hz at any level I'm likely to listen to. I designed the enclosures, but a friend who owns a mill work shop built them. My woodworking skills are pretty rudimentary, theirs are top notch. They're building a couple of enclosures for one of the Dayton 12" reference series woofers, the same model Tom used in the eggs.


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PostPosted: March 4th, 2021, 6:02 pm 
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Looking good Dave. I have been very happy with the 12" Dayton Reference drivers in the eggs. Right now I'm putting up the acoustic treatment panels in the room. There are 14 up on the ceiling and some walls so far. Only 24 more to go. It is a very difficult project, especially the ceiling panels. I'll open another thread when it progresses further.


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PostPosted: March 4th, 2021, 10:02 pm 
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DaveR wrote:
Actually the current phase. I've had these for 3-4 weeks. Originally using the DEQX for the crossover, earlier this week I finished a passive crossover for the top box. Either way, they sound great. Remarkably similar sound to the same components in a poorly designed, actually not designed, box I've been using for quite a while. The bottom is a Dayton Ulti-Max 10". Substantial output, clean and deep - f3 is about 20 Hz. The bass from the top box is better than I expected, usable output to about 35 Hz at any level I'm likely to listen to. I designed the enclosures, but a friend who owns a mill work shop built them. My woodworking skills are pretty rudimentary, theirs are top notch. They're building a couple of enclosures for one of the Dayton 12" reference series woofers, the same model Tom used in the eggs.

That looks a quite substantial ribbon tweeter -or- does it serve a major portion of the mid-range as well? What is the crossover frequency?

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PostPosted: March 5th, 2021, 10:36 am 
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It's the Aurum Cantus G1. I'm crossing over at 1450 Hz with a 24dB Linkwitz Riley filters.

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PostPosted: March 5th, 2021, 11:32 am 
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DaveR wrote:
It's the Aurum Cantus G1. I'm crossing over at 1450 Hz with a 24dB Linkwitz Riley filters.

I would think a large ribbon like that could be crossed over at a lower frequency, but looking at the manufacturer's data -- not so.

Too bad -- the crossover point is smak-dab in the middle of the mid-range -- bummer!

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PostPosted: March 5th, 2021, 12:09 pm 
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First like to say it is looking really good. Put a nice finish on the cabinets and importantly, get some outriggers on the bass module so that it has better stability, hate to see the stacked enclosures tumble over. Suggest checking out Soundocity https://soundocity.com/.

It is challenging to use an classic MTM arrangement with such a large tweeter/midrange, as but with sufficient listening distance, and using DSP, perhaps it will work out just fine. In spite of the fact the crossover is in the midrange (not the best place), at least it is physically low enough to better fit the driver spacing (1450 Hz is a wavelength of 237 mm or 9.31 inches). My memory is a bit rusty, but I think one wants to get the center to center distance between the midranges to be at or less than this value to minimize lobing issues. I may have that wrong, maybe the center of the midrange and center of tweeter...

Fun to do a speaker project. Good luck finishing it up!

David


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PostPosted: March 5th, 2021, 12:19 pm 
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The drivers are time aligned and in phase with each other at all frequencies. The mid drivers are very stiff and light so they're very fast and a great match to the ribbon. I've looked for info about MTM and ribbon tweeters but have been unable to find anything. The center to center distance of the three drivers is just under 7.5 inches which, based on what I've read, is good. However, all those rules assume the tweeter is a point source and the ribbon is not. I am going to try a TMM arrangement before too long to see if there is a discernible difference.

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PostPosted: March 5th, 2021, 1:07 pm 
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DaveR wrote:
The drivers are time aligned and in phase with each other at all frequencies. The mid drivers are very stiff and light so they're very fast and a great match to the ribbon. I've looked for info about MTM and ribbon tweeters but have been unable to find anything. The center to center distance of the three drivers is just under 7.5 inches which, based on what I've read, is good. However, all those rules assume the tweeter is a point source and the ribbon is not. I am going to try a TMM arrangement before too long to see if there is a discernible difference.

A lot depends on the viewpoint. Your ribbons can be considered a "point source" horizontally with wide dispersion. With the narrow long ribbon vertical dispersion it just may work for you.

The proof of the "pudding" is the sound and whether or not you can identify the crossover point when listening to music. Does the sound seem like it is coming from one driver rather than three?

If not -- I would suggest that maybe 24-db/octave slopes may be too extreme.

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PostPosted: March 5th, 2021, 1:41 pm 
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One of the most important things is that the radiation pattern of the drivers match going through the crossover. If not, imaging and timber can suffer. I agree with Walt that with non-matching patterns, a shallower slope is preferable for some aspects although I am not a fan of shallow slopes in general. I had a similar problem trying to match a Heil AMT with a cone midrange because of the differences in radiation patterns at the crossover range. I originally used a 48 dB/octave slope and it was bad. I eventually went to 12 dB/octave which provided enough overlap to hide the mismatch problems. The best solution in my opinion is to go with matching patterns and use a high slope.

Tom


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PostPosted: March 5th, 2021, 2:39 pm 
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The separation of the drivers needs to be as small a fraction of the wavelength at the crossover frequency as you can manage.


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