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34c9 a MDD full range speakers.
34c9 a MDD full range speakers.
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Old 15th September 2019, 07:12 PM   #31
claudiogan is offline claudiogan  Italy
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Quote:
Originally Posted by danb11 View Post
This sounds like a fascinating project. I'm interested in trying the 439h, which seems to have a good response down to 41hz, which appeals to me from my favourite driver 3fe22. I have a few lying around.
This version uses a lot of piping, which becomes quite expensive in steel, here in the UK. PVC box profile pipe is much better value.
Is there any reason you've used metal over plastic?
All the projects I presented use wave guides (tubes). All rigid and smooth pipes inside are suitable. From time to time I have chosen giving priority to parts of previous projects and to the cheapest and / or most comfortable materials to use. Wood, aluminum, rigid PVC and alveolar polypropylene are fine. I do not recommend paper or flexible PVC because deformations make the construction very complicated.

In the 439h project I had the wooden guide ready of the 669g project and I replaced the paper guides (too much distortion by increasing the volume) with aluminum, first with a linear and then logarithmic series. Extending the guides extends the response at low frequencies. In the 439h project there is the drawback that an important part of the high frequency energy is sent above the listener's head.

A compromise between bass response and treble diffusion is the 54m42 project (Thread 54m42 an MDD project (42 wave guides on a driver)). The guides range from 700 to 1400 mm and the resonance of the impedance is at about 65 Hz. The alveolar polypropylene has the advantage of being very economical compared to metal. To have the resonance of the impedance at about 40 Hz it must reach 2000 mm. I didn't do prototypes with lengths between 1000 and 2000 mm and I can't tell you if the treble feels good, nor confirm the 40 Hz. With alveolar polypropylene you can risk spending 30 euros for 2 meter strips, in the worst case they can easily be recovered and reduced in length.
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File Type: jpg 54m42 33 L09 FRZ.jpg (87.5 KB, 144 views)
File Type: jpg 54m42 16 right flangia.jpg (184.2 KB, 148 views)
File Type: jpg 54m42 13 right.jpg (81.1 KB, 145 views)
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Old 15th September 2019, 08:47 PM   #32
danb11 is offline danb11  United Kingdom
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Yes, I see now on your website you have used PVC pipes. I think I will try the 227h to see if I like the sound. Thanks Claudio.
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Old 15th September 2019, 09:12 PM   #33
claudiogan is offline claudiogan  Italy
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Originally Posted by danb11 View Post
Yes, I see now on your website you have used PVC pipes. I think I will try the 227h to see if I like the sound. Thanks Claudio.
With seven guides I suggest using this logarithmic series for the lengths: 552, 610, 673, 743, 820, 906, 1000 mm or proportional values.

See post 34c9 a MDD full range speakers.
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Old 15th September 2019, 10:21 PM   #34
elleman is offline elleman  Sweden
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Hello Claudio,

I did a 3d printable version of your 439h.

Did i understand correctly that the independent tubes start 700mm from the speaker?
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Old 15th September 2019, 10:59 PM   #35
pelanj is online now pelanj  Czech Republic
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Elleman, great idea! This could be a great way of constructing a larger one e.g. with 6 - 8" loudspeaker.

Edit: With the 3D printing - I wonder if the outer spiral could be made continuous and not in steps...and how would that work.

Last edited by pelanj; 15th September 2019 at 11:25 PM.
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Old 16th September 2019, 08:18 AM   #36
claudiogan is offline claudiogan  Italy
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Quote:
Originally Posted by elleman View Post
Hello Claudio,

I did a 3d printable version of your 439h.

Did i understand correctly that the independent tubes start 700mm from the speaker?
Hi Elleman
congratulations for the work and for the rapidity of the realization. Have you also foreseen the possibility of suspension with a bracket or is the magnet resting on the floor?

I have done many projects and with the acronyms not managed in an optimal way I have favored the confusion. I will try to make order on the site, in the meantime summary for the DIY.

The latest MDD designs have the shortest waveguide length of half the longest length. The series is logarithmic and changes if it is a prototype with 7, 9 or N guides. Another variable is the shape of the circular, square, arched waveguides, the shape influences only the mechanical construction mode.

By increasing the length of the guides the FR extends downwards, the increase in length has a drawback, the energy of the high frequencies emitted by diffraction is concentrated in the upper part. In the prototypes I found the following approximate values ​​of the first peak in the impedance module:
439h - max length 1.8 m, frequency 40 Hz
34c9 - max length 1.0 m, frequency 80 Hz
54m42 - max length 1.4 m, frequency 65 Hz
66c9 - max length 1.0 m, frequency 80 Hz

With 9 wave guides I used the logarithmic series 540, 583, 630, 680, 735, 794, 857, 926, 1000 mm compact series. If you want to extend the FR downwards, you can multiply everything by 1.4 or by 2, checking that you do not lose the high frequencies emitted above the listener's head. With the module system you've set up it should be simple.
Medium series 1.4 m: 773, 853, 942, 1040, 1148, 1268, 1400 mm
Large series 2 m: 1104, 1219, 1346, 1486, 1641, 1811, 2000 mm

Let me know how it sounds.
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Old 16th September 2019, 01:13 PM   #37
claudiogan is offline claudiogan  Italy
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Quote:
Originally Posted by elleman View Post
Did i understand correctly that the independent tubes start 700mm from the speaker?
The independent tubes start at 5-10 mm from the speaker in projects 34c9, 66c9 and 54m42.
They start at 700 mm in the 439h project.

With the measures indicated, the 439h project, with respect to other projects, has a greater extension on the low and less present highs.

Last edited by claudiogan; 16th September 2019 at 01:28 PM. Reason: integration
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Old 16th September 2019, 01:43 PM   #38
danb11 is offline danb11  United Kingdom
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Quote:
Originally Posted by elleman View Post
Hello Claudio,

I did a 3d printable version of your 439h.

Did i understand correctly that the independent tubes start 700mm from the speaker?
elleman, this is such an elegant solution! Is that a realistic mock up or a photograph of the printed waveguide? I would love to try this out myself, but my CAD skills are next to nothing.

I can see this idea catching on quickly. Hopefully we get some more interesting takes on build methods.
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Old 16th September 2019, 03:05 PM   #39
elleman is offline elleman  Sweden
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Originally Posted by claudiogan View Post
Hi Elleman
congratulations for the work and for the rapidity of the realization. Have you also foreseen the possibility of suspension with a bracket or is the magnet resting on the floor?
I was thinking maybe to hang it in a cord from the roof?

Quote:
Originally Posted by danb11 View Post
elleman, this is such an elegant solution! Is that a realistic mock up or a photograph of the printed waveguide? I would love to try this out myself, but my CAD skills are next to nothing.

I can see this idea catching on quickly. Hopefully we get some more interesting takes on build methods.
It is just a quick render. My CAD skills are not great but it took me about 2 hours before going to bed last night.

If you have any ideas, just put them on a piece of paper and i will happily transform it in to usable drawings.
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Old 16th September 2019, 03:39 PM   #40
danb11 is offline danb11  United Kingdom
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Originally Posted by elleman View Post
If you have any ideas, just put them on a piece of paper and i will happily transform it in to usable drawings.
I can only imagine getting it printed, built and measured will lead to the best feedback/improvements.
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