That is because it is a "dumping material-free box".
Advantages of no dumping material
･cost down
･simple build
･powerful and dynamic sound
･effective use of the sound from the back of the cone (high efficiency)
I don't understand this cabinet design. The split design part, OK, I understand what it's goal likely is.
But it's not really a "horn" right? because both of the the exits of the cabinet are small.
Normally with a back-horn design, the back wave channels expand to it's maximum size at the exit point of the cabinet.
But here it does not. So it's some kinda of hybrid horn-BR/TL design?
Also the dual/split BH design, is a much more complicated to build so presumably there is a big advantage here?
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@nandappe Have you ever experimented with adding a big supraBaffle ?
You could try using styrofoam (styrene sheet) material first until you find the size and shape you like then build them with wood.
https://www.diyaudio.com/community/threads/suprabaffles-wavelaunch.86636/post-1005557
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It looks unnecessary complicated 12 and 26 could be replaced by an extension of 11 and 21 and 28 by an extension of 18.
Otherwise it is a quarter wave pipe/transmission line. The positive flare lower the Q of the fundamental resonance and also increase the frequency compared to a straight pipe. The constriction at the opening offset the increase in frequency. If the pipes work independently the dips and peaks due to harmonics will occur at different frequencies for the two pipes and then hopefully improve the sound compared to a "mono pipe"
It would be interesting to see some measurements of pipe output and nearfield measurements of the driver. My Decca corner horn sounded surprisingly good without any damping material in it, so it might work.
Otherwise it is a quarter wave pipe/transmission line. The positive flare lower the Q of the fundamental resonance and also increase the frequency compared to a straight pipe. The constriction at the opening offset the increase in frequency. If the pipes work independently the dips and peaks due to harmonics will occur at different frequencies for the two pipes and then hopefully improve the sound compared to a "mono pipe"
It would be interesting to see some measurements of pipe output and nearfield measurements of the driver. My Decca corner horn sounded surprisingly good without any damping material in it, so it might work.
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Gonna be a tight fit. You'll probably need to double up on the baffle thickness (or suprabaffle maybe) at the driver location. CHP-90 has a much larger Vas than typical 4" drivers, so might actually work better in FHXL. Dave will know.
jeff
@nandappe I listened to this recording compared to your recording of the SB20FRPC30-8 + DDVP-20 with the same music and I hear no big differences. Maybe in front of them (not over Youtube) you can hear big differences?
Anyway, I think that says a lot that the CHP-90 in this cabinet can have bass response essentially equal to the SB 8" driver. But this makes me wonder if maybe the DDVP-20 isn't the most ideal cabinet for the SB 8" driver?
Duct attached to horn openings are effective in "alleviating BH quirks and improving loose bass" and have been used since the 1990s.
I do not need a "Big Supra-Baffle". I want my baffle to be as small as possible.
