It really starts with two carboard pipes one inside the other
I use a Philips 6-6.5" fullrange driver.
Diameter of he outer pipe is 1.5 the effective cone diameter (in my particular case 200mm) the length is 4 times diameter and distance to the floor 1/10 diameter. Inner diameter is 0.6 M-wall tickness. I used a 120mm pipe and that is close enough to the calculated 116mm i get with a 4mm thick outer tube. Lenght of inner tube is 0.6h in my case 480mm. Nominal lower frequency limit is 35000/h in mm here 44Hz. The actual tuning frequency is slightly above this. The proportion of diameters of inner to outer pipe should be kept at >0.5 and<0.7 and the h>at least 3 times M to behave as a proper pipe. But otherwise the design scale well up and down over a wide range.
To get the end stoppers you need some MDF or wood. some wool cables and glue is also needed. I added some damping foam and bitumen pads in the top of the outer pipe and some crossbraces at the open end of the pipe.
This is how it looks assembled, I had a glue cartridge that was about to dry up so I was very liberal with it. 😉
And then some damping material and cables
Connector and 3 legs
I used a fabric that had that vintage look and a black foam top.
Notes:
1.A elastic fabric sewn as tube with a snug fit was pulled over the tube and then stapled at both ends on the inside of the tube.
2. The top baffle is recessed the hight of the driver and the thickness of the foam cover.
3. Using a scissor to cut away some fabric before drilling is a good idea as the the drillbit never stops tearing up the cought fabric...
Measuring it with Woofer Tester 3 shows a fundamental resonance at 70 Hz as well as a damped third harmonic at 210 Hz and the fifith harmonic at 350 Hz. With no damping material the harmonics is far more visable.
The driver has a sticker AD3710M but it looks like a later generation in that series of drivers.
They really sound quite nice, largely due to the this little gem of a driver. I simply like to listen to music with these drivers, a far cry from say Philips 9710 that need a lot of taming to sound good.
This folding og pipes could also be used to make bass-traps🙂
I use a Philips 6-6.5" fullrange driver.
Diameter of he outer pipe is 1.5 the effective cone diameter (in my particular case 200mm) the length is 4 times diameter and distance to the floor 1/10 diameter. Inner diameter is 0.6 M-wall tickness. I used a 120mm pipe and that is close enough to the calculated 116mm i get with a 4mm thick outer tube. Lenght of inner tube is 0.6h in my case 480mm. Nominal lower frequency limit is 35000/h in mm here 44Hz. The actual tuning frequency is slightly above this. The proportion of diameters of inner to outer pipe should be kept at >0.5 and<0.7 and the h>at least 3 times M to behave as a proper pipe. But otherwise the design scale well up and down over a wide range.
To get the end stoppers you need some MDF or wood. some wool cables and glue is also needed. I added some damping foam and bitumen pads in the top of the outer pipe and some crossbraces at the open end of the pipe.
This is how it looks assembled, I had a glue cartridge that was about to dry up so I was very liberal with it. 😉
And then some damping material and cables
Connector and 3 legs
I used a fabric that had that vintage look and a black foam top.
Notes:
1.A elastic fabric sewn as tube with a snug fit was pulled over the tube and then stapled at both ends on the inside of the tube.
2. The top baffle is recessed the hight of the driver and the thickness of the foam cover.
3. Using a scissor to cut away some fabric before drilling is a good idea as the the drillbit never stops tearing up the cought fabric...
Measuring it with Woofer Tester 3 shows a fundamental resonance at 70 Hz as well as a damped third harmonic at 210 Hz and the fifith harmonic at 350 Hz. With no damping material the harmonics is far more visable.
The driver has a sticker AD3710M but it looks like a later generation in that series of drivers.
They really sound quite nice, largely due to the this little gem of a driver. I simply like to listen to music with these drivers, a far cry from say Philips 9710 that need a lot of taming to sound good.
This folding og pipes could also be used to make bass-traps🙂
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OK bigger pictures and added one of the driver as well. I will get a scale and measure so that I get equal amount of wadding in both pipes and see if they match better than now.
I also plan to buy the PE OmniMic measurment system, that will help the tweaking,perhaps, those omnidirectional speakers are hard to measure.
I also plan to buy the PE OmniMic measurment system, that will help the tweaking,perhaps, those omnidirectional speakers are hard to measure.
You could do some 180 degree reflectors, by simply creasing an oval piece of plexiglass with a heatgun and a ledge, then put it at a 45 degree angle over the cone (oval to compensate for anisotropy). This would improve room behaviour, highs and allow the speaker to be placed near room boundaries better.
In the original articles they suggest experiments with reflectors. The problem is that the midiTrike sound quite light as it is. With the small round baffle there is a 6dB loss below 600 Hz and reflecting more hight frequency sound can cause a even "lighter" balance. Mind you it has nothing of the shrillness like the 9710 it simply would need som fatter low end to even up the balance. Perhaps I can make a passive filter to shelve down everything above 600 Hz...
Added a baffle step compensation filter calulated values are 3.5 Ohm and 1mH, for a 6 dB step at 570 Hz. I used 4.7 Ohm and 0.85 mH as that is what I had at home, remember this is a low cost project. For the Zobel calculated values are 20 microF and 4.4 Ohm I used 20 MicroF and 6.8 Ohm. Keeping it vintage and low cost I use very old electrolytic caps and some of the wires are not even copper and very very thin ( harvested from some old speaker crossover wires). So much for ultra fidelity plastic caps and foil coils...
Green curve is driver as it
Pink curve shows the effect of adding the Zobel, even if the resistance is 50% high it still works well the driver impedance is much flatter and reach 5 Ohms at 12 kHz instead of 2 kHz.
Blue curve shows the baffle step added to the mix. At the nominal cutof the impedence difference is about 1.5 Ohm and between 1.5 and 20 kHz it is pretty constantly 4 Ohms.
It sounds better with a better bass to higher range balance. Is there room for improvements? Sure is, but this was a major step forward. I would like to get a lift in the last two octaves as the driver is facing upwards...
Perhaps I shall look into reflectors, it never ends does it 😉
Green curve is driver as it
Pink curve shows the effect of adding the Zobel, even if the resistance is 50% high it still works well the driver impedance is much flatter and reach 5 Ohms at 12 kHz instead of 2 kHz.
Blue curve shows the baffle step added to the mix. At the nominal cutof the impedence difference is about 1.5 Ohm and between 1.5 and 20 kHz it is pretty constantly 4 Ohms.
It sounds better with a better bass to higher range balance. Is there room for improvements? Sure is, but this was a major step forward. I would like to get a lift in the last two octaves as the driver is facing upwards...
Perhaps I shall look into reflectors, it never ends does it 😉
brill!
a few years ago I played with putting an FE167 in a succession of cones to approximate an elongated horn. I gave up because it seemed overly complicated. Well done for persevering.
who dares wins.
a few years ago I played with putting an FE167 in a succession of cones to approximate an elongated horn. I gave up because it seemed overly complicated. Well done for persevering.
who dares wins.
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