True, dont need it for home use.
The HF sensitivity is only 90 dB/1m at 2.83V. That is just as sensitive as stock. I think it is caused by too high compression and poor sealing of the throat chamber, making it larger in volume than intended, which lowers HF efficiency.
The drawback of lower compression ratio on the MF, is bigger ports. This probably will cause more possible interference between the HF sound and the MF ports. But it will be evaluated.
i think i failed in keeping the main path to the exit equal expansion rate. Its all over the place. From 0.8 to 0.97 cm2/cm and back to 0.8. Also, this happens at 26 mm from the HF driver and at 47.5 mm. This corresponds to the dip in the HF fr and polar at 3.3 k and 1.8 k.
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That does seem plausible if the expansion rate changes are happening at the 1/4 wavelength distances. Was the expansion rate more uniform on the prototype that did not have the dip?
Sneak Peek!
New version of the CCDIY
MF and HF crossed over @4kHz, 2nd order and EQ-ed with APO equalizer.
First is Fourier decay
second is Burst decay
Distortion is at 102 dB nominal
To be continued...
New version of the CCDIY
MF and HF crossed over @4kHz, 2nd order and EQ-ed with APO equalizer.
First is Fourier decay
second is Burst decay
Distortion is at 102 dB nominal
To be continued...
At 1 meter?
You may want to test at a lower level also to see what's inherent to the design and what's just pushing too hard. The relatively high 2nd harmonic has me curious.
2.83 V or 86 dB at 1 meter are also common levels to test at. At lower levels it can be helpful to use a closer microphone distance for the distortion measurement, so the noise floor is farther below the signal level. This can introduce frequency response errors at times, but that's usually a reasonable trade-off. You don't want the microphone so close that you're out of the microphone's linear range either though. 110-115 dB is usually a good upper range to be at, though some microphones can take more.
yes. i use this distortion measuring setup for assessing the loading of the diaphragms. i compare the distortion at about 100 dB to see if the port entry shape loads the diaphragm evenly, so some load is needed. for example, below you find a comparison of the way of loading and distortion of the MF driver in newest version and the last version. the last version has the dust cap cut away and only has port entries at the middle of the conical part of the diaphragm. this caused a lot of distortion. the newest version has the dust cap still attached and the port entry more spread over the cone area and partially the dust cap. this is the region where the diaphragm is stiffest and has the lowest chance to pick up inter modal stuff, like close to the surround of the driver.
Between the versions, there is no change in compression ratio, throat volume and no change in the path towards the 1.4 inch exit.
I also did the same modification to the HF port entries. also, i made the HF a radial slit phase plug which has a transition form radial slot to the annular path to the 1.4 inch exit.
PS: the cross section can make the paths look weird, as seen in the newest versions HF phase plug.
I will try! thanks for the insights
latest version without dust cap:
PS: the fundamental is shown as 88 dB, but it should be 100 dB nominal for 500 to 2k. there is a big dip in the FR of this version
New version with dust cap and spread port entry:
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I realize that the dip didnt go away fully. I think it is because the helmholz resonator effect of the mid ports on the HF sound is less, thus creating a smaller dip. The dip at 3.3 k is not a problem though. The mid goes up to 4k easily. Would love to extend the mid to 5 k but thats for later.
The latest version is about as good as i want it to be.
I looked up the DCX464 distortion: at 104 dB 1m, mic at 10 cm from horn mouth. The following was measured by Audioexpress
MF:
HF:
As lately measured, the THD of the ccdiy at 104 dB is about 1.5 to 2%. Thats a succes, i think. So, the only thing to finish sound wise is the stored energy in the MF and HF decay graphs around 3 to 5khz.
Cooling, durability, print quality would be the next step after sound.
I have a question of the community: what would you like to see next on this project/subject?
I looked up the DCX464 distortion: at 104 dB 1m, mic at 10 cm from horn mouth. The following was measured by Audioexpress
MF:
HF:
As lately measured, the THD of the ccdiy at 104 dB is about 1.5 to 2%. Thats a succes, i think. So, the only thing to finish sound wise is the stored energy in the MF and HF decay graphs around 3 to 5khz.
Cooling, durability, print quality would be the next step after sound.
I have a question of the community: what would you like to see next on this project/subject?
Yes I listened to it, but i don't have any good reference gear or experience. So would love to have someone test it.
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Thinking about changing the mid driver from the lavoce FSN030.72 (sd of 33,2 cm2) to the smaller FSN020.71F (18 cm2). As seen earlier, third order harmonics increase for the lower frequencies at moderate SPL. This is probably the paper cone having non piston like behaviour because of the high-ish compression ratio of 8:1. Also, I cant change the port area of the mid because of higher frequency sound (from the HF driver) interacting more with the increased port size. Could the 3rd order come from something else?
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Im thinking about the future of this project. Would love to go open cource but im scared it may fade into a dead and lost community project. Also could go commercial with production as a hifi/studio driver or sell plans to fund the hobby (Will provide resources if i go this route to pay back the community as it also helps me).
Would love to hear your 2 cents.
Would love to hear your 2 cents.
Keep it as a hobby. Otherwise you will end up in the rabbit hole that "conventional audio by loudspeakers" is in first, and will be in the second quarter of the 21th century.
If it's good enough and has true value, it won't. And if so, it will not have any commercial success either...
//
Team up with others, so it depends not from you only!
If you make it 'open source' then it could be thought of as having 'low value' which unfortunately is something related to human psychology. On the other hand, if you try to go big, you'd be crushed by the bigger players who'd then fund some 'internet reviews' criticising your product etc. .
In my opinion, you could be somewhere in the middle so as to not get noticed by your rivals but still make some business, at least until you get paid for your troubles, especially if a considerable amount of your time / effort has gone into this.
Either way, you'll need production (CAD/CAM) facilities from where considerably cheaper copies of your design would eventually reach the market.