The 669g project upgrade the 665g project, the acoustic screen is rigid and the acoustic transformer use paper. More bass, less distortion.
More information and more projects 621g 665g 666g 667g at link Claudio Gandolfi - MDD, http://www.claudiogandolfi.it/dw/diy.pdf
At link Best 669g images
My site is: Claudio Gandolfi - MDD
My current working hypotheses are described on the page acustica.
The last projects reported in the full range and planars-and-exotics section:
54m42 54m42 an MDD project (42 alveolar polypropylene wave guides on one driver)
other documentation is published at 54m42
34c9 Compact aluminum project
34c9 a MDD full range speakers.
https://www.claudiogandolfi.it/34c9.html
66c9 66c9 a low-cost MDD project (paper waveguide for educational use)
https://www.claudiogandolfi.it/66c9.html
22D7 Two drivers per channel for a 3D effect
22D7: four MDD systems for a 3D effect with omnidirectional speakers
https://www.claudiogandolfi.it/22d7.html
22M7 Simple and inexpensive wide-band rigid PVC project.
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-4.html#post6006473
other documentation is published at 22M7.
22C71L8 One driver per channel with waveguides applied to the two sides of the cone.
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-5.html#post6017746
other documentation is published at 22C71L8.
MDDHX135 an MDD project with the HX135 driver
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-6.html#post6124020
other documentation is published at MDDHX135.
MDD3FE25 an MDD project with the 3FE25 driver
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-8.html#post6170069
other documentation is published at MDD3FE25.
More information and more projects 621g 665g 666g 667g at link Claudio Gandolfi - MDD, http://www.claudiogandolfi.it/dw/diy.pdf
At link Best 669g images
My site is: Claudio Gandolfi - MDD
My current working hypotheses are described on the page acustica.
The last projects reported in the full range and planars-and-exotics section:
54m42 54m42 an MDD project (42 alveolar polypropylene wave guides on one driver)
other documentation is published at 54m42
34c9 Compact aluminum project
34c9 a MDD full range speakers.
https://www.claudiogandolfi.it/34c9.html
66c9 66c9 a low-cost MDD project (paper waveguide for educational use)
https://www.claudiogandolfi.it/66c9.html
22D7 Two drivers per channel for a 3D effect
22D7: four MDD systems for a 3D effect with omnidirectional speakers
https://www.claudiogandolfi.it/22d7.html
22M7 Simple and inexpensive wide-band rigid PVC project.
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-4.html#post6006473
other documentation is published at 22M7.
22C71L8 One driver per channel with waveguides applied to the two sides of the cone.
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-5.html#post6017746
other documentation is published at 22C71L8.
MDDHX135 an MDD project with the HX135 driver
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-6.html#post6124020
other documentation is published at MDDHX135.
MDD3FE25 an MDD project with the 3FE25 driver
https://www.diyaudio.com/forums/pla...nidirectional-single-drive-8.html#post6170069
other documentation is published at MDD3FE25.
Last edited:
The hurry to go on holiday made me make a post too synthetic. Now I want to describe the speaker with more detail.
669g is a transmission line acoustic box. A first wave guide is made of wood, others 9 side by side and of different length in paper.
The combination of the parts makes it possible to reproduce frequencies below 50 Hz using a 3FE25 speaker from the Faital-Pro which has a declared Fs of 110 Hz.
The paper part reduces the resonances of the air contained in the rigid part for two reasons.
1) The system works with sound wave paths of different length, from a minimum of 130 cm to a maximum of 200 cm.
2) Folded paper is an inelastic material. When it is deformed by the pressure of the sound waves passing through it, it acts as a damping material normally applied inside the transmission lines.
The most important task of the 9 paper waveguides is another: to emit attenuated, delayed and coherent secondary waves with respect to the primary emission of the underside of the loudspeaker.
Secondary waves are emitted by exploiting the deformation of the paper wave guides and the oblique cuts.
The waveguide acoustic transformer is the technology that exploits the radial deformation of the paper waveguides.
The waveguide acoustic diffractor is the technology that uses the diffraction of oblique cuts.
The delays range from 3 to 7 milliseconds.
The 669g loudspeaker and those of the 6XXg series are the only ones able to implement this functionality without resorting to electronic delays or multiple loudspeakers.
The same acoustic result can also be obtained with a DSP, an array of speakers, the D'Appolito configuration and with large membranes.
The paper waveguides make the omnidirectional emission 360 degrees in the horizontal plane,
The Robin srl has filed the European Patent for the technologies of the acoustic waveguide transformer and the waveguide acoustic diffractor.
For personal use, the project is allowed to be replicated.
Another aspect that may be of interest to a DIY is the subsonic resonance support.
A steel L supports the wooden waveguide to which the loudspeaker is fixed.
The system oscillates at about 1 Hz and has a high enough Q to acoustically isolate the wave guides from the floor to the audible frequencies.
6XXg speakers are not commercially those who want to listen can build a couple for personal use.
I published a post to modify with the technologies of the acoustic transformer and of the acoustic diffractor with a multimedia system 2.1.
The reproduction is not HiFi but the effect of secondary waves is perceived.
621g near zero euro project
In alternative, those interested can contact us to create a pair of customized prototypes.
In the home page more information on the operation of the 4 sections of the acoustic load.
home
In the page the measurements on the 6XXg series speakers.
misure
in the acoustic page my working hypotheses used in the development of the speakers.
installazione
669g is a transmission line acoustic box. A first wave guide is made of wood, others 9 side by side and of different length in paper.
The combination of the parts makes it possible to reproduce frequencies below 50 Hz using a 3FE25 speaker from the Faital-Pro which has a declared Fs of 110 Hz.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The paper part reduces the resonances of the air contained in the rigid part for two reasons.
1) The system works with sound wave paths of different length, from a minimum of 130 cm to a maximum of 200 cm.
2) Folded paper is an inelastic material. When it is deformed by the pressure of the sound waves passing through it, it acts as a damping material normally applied inside the transmission lines.
An externally hosted image should be here but it was not working when we last tested it.
The most important task of the 9 paper waveguides is another: to emit attenuated, delayed and coherent secondary waves with respect to the primary emission of the underside of the loudspeaker.
Secondary waves are emitted by exploiting the deformation of the paper wave guides and the oblique cuts.
The waveguide acoustic transformer is the technology that exploits the radial deformation of the paper waveguides.
The waveguide acoustic diffractor is the technology that uses the diffraction of oblique cuts.
The delays range from 3 to 7 milliseconds.
The 669g loudspeaker and those of the 6XXg series are the only ones able to implement this functionality without resorting to electronic delays or multiple loudspeakers.
The same acoustic result can also be obtained with a DSP, an array of speakers, the D'Appolito configuration and with large membranes.
The paper waveguides make the omnidirectional emission 360 degrees in the horizontal plane,
The Robin srl has filed the European Patent for the technologies of the acoustic waveguide transformer and the waveguide acoustic diffractor.
For personal use, the project is allowed to be replicated.
Another aspect that may be of interest to a DIY is the subsonic resonance support.
A steel L supports the wooden waveguide to which the loudspeaker is fixed.
The system oscillates at about 1 Hz and has a high enough Q to acoustically isolate the wave guides from the floor to the audible frequencies.
6XXg speakers are not commercially those who want to listen can build a couple for personal use.
I published a post to modify with the technologies of the acoustic transformer and of the acoustic diffractor with a multimedia system 2.1.
The reproduction is not HiFi but the effect of secondary waves is perceived.
621g near zero euro project
In alternative, those interested can contact us to create a pair of customized prototypes.
In the home page more information on the operation of the 4 sections of the acoustic load.
home
In the page the measurements on the 6XXg series speakers.
misure
in the acoustic page my working hypotheses used in the development of the speakers.
installazione
Neat stuff! I did a design of something related here:
The PANPIPE (Pentahorn) BLH Speaker
Never built it though - yours looks like a perfect foam core project. Paper might rattle like a reed and add a sound like reed woodwind instrument or kazoo.
Also, a similar effect might be achieved with a long tapered Karlson aperture which has been added to the end of some TL’s.
The PANPIPE (Pentahorn) BLH Speaker
Never built it though - yours looks like a perfect foam core project. Paper might rattle like a reed and add a sound like reed woodwind instrument or kazoo.
Also, a similar effect might be achieved with a long tapered Karlson aperture which has been added to the end of some TL’s.
I thank xrk971 for the reference to BLH which suggested an acronym suitable for the 6XXg series speakers: FLP (Front-Loaded Pipes). All speakers have frontal sound load and at least two waveguides. The first is rigid or semi-rigid and smooth inside. The second is radially deformable by the pressure of the sound waves that cross it and maximizes the phenomenon of acoustic diffraction. The second waveguide can be decomposed into several waveguides of different lengths.
In the 669g loudspeaker the loudspeaker sends the frontal emission into the first rigid waveguide. The sound waves coming out of the rigid guide are sent inside the 9 deformable waveguides and then in the environment maximizing the acoustic diffraction.
I want to highlight some differences with respect to the project: "PANPIPE (Pentahorn) BLH Speaker". The first is that part of the waveguide of the 669g speaker is deformable and inelastic, therefore suitable for dampening the resonances of the air inside.
This is the measurement of the 669g speaker impedance, the black line is detected with the deformable paper waveguides mounted, the green line is detected with the only rigid wooden waveguide. The damping effect of the paper guides is clearly seen. A secondary effect of the paper guides is to increase the average length of the sound wave paths and reduce the center frequency of the peaks.
In the attached file "669g 2018 08 02 ta left" the red line shows the frequency response with the deformable paper waveguides installed, the green line shows the effect of the lack of paper guides.
The graphs are different from the results of the simulation of the project "PANPIPE (Pentahorn) BLH Speaker".
A second difference is that the emission at high frequencies in the PANPIPE is concentrated in a frontal lobe, in the FLP diffusers the emission is omnidirectional in the horizontal plane.
If the purpose of the paper guides were to optimize the frequency response, the FLP speakers would be just a bizarre and complicated system to make an acoustic speaker. It would be much simpler to use at a DSP.
The primary purpose of the deformable paper waveguides in FLP diffusers is to emit secondary waves attenuated, delayed and consistent with the primary emission of the rear side of the loudspeaker. You can read my working hypotheses on the acoustics of FLP loudspeakers at:
installation
I have not tried using foam. It could work for the rigid part, possibly with some reinforcement outside. I do not think it's suitable for making the waveforms deformable by the sound waves that cross them, maybe it could work using sheets less than 1 mm thick.
The current limit of the 669g project is not the paper but the problems related to the precision and quality of the numerous gluing. I intervened a few times to add glue between the waveguides. These are tens of contact lines for a total of several meters of gluing. Increasing the volume can cause annoying vibrations. The prototype in the photo plays well up to 90 dB in a 4 x 4 x 3 room.
On youTube you can listen to some non-professional recordings of the 669g speakers.
YouTube
In the 669g loudspeaker the loudspeaker sends the frontal emission into the first rigid waveguide. The sound waves coming out of the rigid guide are sent inside the 9 deformable waveguides and then in the environment maximizing the acoustic diffraction.
I want to highlight some differences with respect to the project: "PANPIPE (Pentahorn) BLH Speaker". The first is that part of the waveguide of the 669g speaker is deformable and inelastic, therefore suitable for dampening the resonances of the air inside.
An externally hosted image should be here but it was not working when we last tested it.
This is the measurement of the 669g speaker impedance, the black line is detected with the deformable paper waveguides mounted, the green line is detected with the only rigid wooden waveguide. The damping effect of the paper guides is clearly seen. A secondary effect of the paper guides is to increase the average length of the sound wave paths and reduce the center frequency of the peaks.
In the attached file "669g 2018 08 02 ta left" the red line shows the frequency response with the deformable paper waveguides installed, the green line shows the effect of the lack of paper guides.
The graphs are different from the results of the simulation of the project "PANPIPE (Pentahorn) BLH Speaker".
A second difference is that the emission at high frequencies in the PANPIPE is concentrated in a frontal lobe, in the FLP diffusers the emission is omnidirectional in the horizontal plane.
If the purpose of the paper guides were to optimize the frequency response, the FLP speakers would be just a bizarre and complicated system to make an acoustic speaker. It would be much simpler to use at a DSP.
The primary purpose of the deformable paper waveguides in FLP diffusers is to emit secondary waves attenuated, delayed and consistent with the primary emission of the rear side of the loudspeaker. You can read my working hypotheses on the acoustics of FLP loudspeakers at:
installation
I have not tried using foam. It could work for the rigid part, possibly with some reinforcement outside. I do not think it's suitable for making the waveforms deformable by the sound waves that cross them, maybe it could work using sheets less than 1 mm thick.
The current limit of the 669g project is not the paper but the problems related to the precision and quality of the numerous gluing. I intervened a few times to add glue between the waveguides. These are tens of contact lines for a total of several meters of gluing. Increasing the volume can cause annoying vibrations. The prototype in the photo plays well up to 90 dB in a 4 x 4 x 3 room.
On youTube you can listen to some non-professional recordings of the 669g speakers.
YouTube
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