For a pure top (mid/high speaker), you'd definitely want to go CB rather than BR. With that, and minimal depth to fit the drivers, the Solana can get to as close as, rough calculation, 12l rear net volume.
Simulated (in WinISD) as a 4th order bandpass, we can get to a result quite similar to the raw measurements; blue 6NDL38, green 6RS140, red the 6ND430 galucha named:
And Max. SPL (@ Xlin and AES power handling):
That would definitely lead to a very controlled horizontal off axis behavior.
That statement definitely hits home. Just very recently, I've printed a part, to test fit a different driver, especially clearance of the membrane to the waveguide at maximum excursion - and I can tell you, with no rear port to limit excursion, at full load at low frequencies, the front ports are basically a fan. Even in the midbass region, it still seemed like somewhat of an issue. Then again, nothing that should be unexpected, given your compression measurements showed up to 2,5 dB compression in the bass area.
That driver wasn't on my radar, but it should be a viable candidate as stoneeh mentioned. I'll make a note to add it to the next update to the guide.
I do think in the future I want to explore more modular, scalable approaches to point sources that can cover 200Hz-upwards. For the work I do in the soundsystems realm, there's a lot of appeal in getting a coherent, controlled directivity top that can cover precisely that range. It lends itself really nicely to crossover to a dedicated bassbin section covering 60-200Hz or somewhere around that. Maybe that will be a further iteration of the Solana that's more purpose built for high output and utilizing a 1.4" comp driver.
Presume that You heard port noise, was the port velocity over 17m/s? I believe Scott Hinson did some measurements on port noise vs velocity.
That's really not that easy of a question & answer. The amount of noise has to do with not just the air speed, but if the exit has rough edges etc which would disturb the air flow. And the issue of port noise is a completely separate one from that of port compression. As for noise, I may eventually do a video recording of the test I mentioned (driver at max. excursion, front port at full load) to just let everyone see, listen & judge for themselves.
This may be a dumb suggestion, and you may have already explored this but I had the thought of lining the front ports with a thin cotton, wool, or foam to reduce those high frequency resonances the ports have caused. I dont know how much it would affect performance in other aspects just a brainstorm idea.
I did attempt various arrangements of melamine foam inside the ports with the B prototype. Doing this did smooth out the response of the compression driver, and even increased midrange sensitivity of it. The cost however was significantly less bass output for the 6.5"s. I think that strategy may be more viable for 3-way MEHs where you aren't necessarily needing bass output from the midranges, although I may revisit the idea with different density foams/polyfil, etc.
10ms gate. Not SPL calibrated
Woofer response was taken indoors, so ignore the wiggles - more focused on the overall difference in sensitivity. 25 cycle FDW. Not SPL calibrated
10ms gate. Not SPL calibrated
Woofer response was taken indoors, so ignore the wiggles - more focused on the overall difference in sensitivity. 25 cycle FDW. Not SPL calibrated
I cut magic sponge discs to put in the four 3/4" mid-range ports on my syn10 , that has four 4ndf34's. Can't say it changed anything worth mentioning with the CD's response (dcx464), or the mids either really.
Edit: maybe you meant the influence the mid section ports have on the response of the compression driver; in this case, ignore my post. But if you meant what I initially assumed you meant, see below ⬇
Any type of resonator should only be excited at its desired (low Q) resonance (bandpass, quarter wave, Helmholtz, ...), not at its undesired (high Q) higher resonances (double wavelength modes).
For example, a bassreflex speaker with a tuning at 40 Hz and large enough port usually has the first standing wave occuring at somewhere around 200 Hz, so it needs to be crossed over significantly lower than that (recommended: an octave below or lower; in this example ~100 Hz).
Same principle here - we have the front ports of the mid section acting as a bandpass (with peak around 600 Hz), and we need to set a lowpass filter low and steep enough for any higher modes of the front ports to not get excited. This eliminates the need for any damping of the front port.
For example, a bassreflex speaker with a tuning at 40 Hz and large enough port usually has the first standing wave occuring at somewhere around 200 Hz, so it needs to be crossed over significantly lower than that (recommended: an octave below or lower; in this example ~100 Hz).
Same principle here - we have the front ports of the mid section acting as a bandpass (with peak around 600 Hz), and we need to set a lowpass filter low and steep enough for any higher modes of the front ports to not get excited. This eliminates the need for any damping of the front port.
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