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Ok guys – time for the midrange volume measurement. For this you join me inside on the workbench. No sunburns today!
Tweemid baffle is just taped in place to make sure none of our fancy volumetric beans get away.
Make sure, after measuring, to put your Penta in the sun so it can dry out.
This turned out to be one of the more fun days I have had with a project recently. Bizarre yet satisfying!
Results are 29.8 net kg of water which translates to 29.8L for the woofer volumes (including ports!).
Next up we will probably get out the beans for measuring the twee-mid volume.
The filling took so long because the scale kept turning off causing us to reset. So filling actually took a few attempts!
Once full, the entire speaker + water weighed 38.8kg.
Guys, if you haven’t thought to wash out your speakers, I highly recommend it. This particular pair were mega gross. Keen eyes will spot the frequent occurrence of critters here and there throughout the photos.
Ok now that most of the leaks are stopped up long enough / well enough for this test, we continued…
After a few minutes of filling we started to notice some spots that were leaking. This expected but I did miss some big ones – I forgot to patch the pass-throughs for the tweemids and the display. So pause and go for a reset! The grass around the office could use it honestly.
Here goes nothing! The thought of becoming “that guy” who filled a penta with water was starting to sink in haha.
Ok everybody, the moment has finally arrived. Time to tackle the silliest task of this project! Its time to measure the internal volume of the cabinet.
The dry weight is 9kg.
Usually when reverse engineering speakers, the office gang and I use uncooked beans of some kind. This time we decided to use water.
Lastly is the progress on the teardown of the donor speaker. I have finally de-wired the cabinet and pulled the stuffing out.
Of course the crossover and wiring harness will get reused but we need to get the cabinet empty in order to reverse engineer the volume. Stay tuned for this!
De-pinned the display connector in order to pull the cables back through the baffle.
Making sure everything gets labeled before I forget where everything goes! Pictures (and other Pentas) will serve as back up resources haha.
Slowly easing out the stuck-in crossover boards.
Separating the display harness from the speaker harness (no need for it here, at least this time around).
What the full harness looks together (speaker and display harness combined, as it is built in the speakers).
Speaking of printing, here are the first goes at attempting an orientation for a build on an FDM style machine.
Sadly my Ender 5 Plus is currently down for repairs but I’ll be running a test soon. Currently sliced at 0.25mm layer and 0.4mm nozzle for now. Might bump the nozzle up after the machine repair but haven’t decided yet. Currently at 36hr print time with healthy build parameters for strength!
Well everyone, lots of random updates for you since BeoWorld went dark during the transition to the new forum so here goes….
First up is the updates on the twee mid module – slowly getting the module modeled up. Had to model the tweeter and now all that’s left is to get the bosses and fixings modeled in so I can take it for a test print.
Thanks, Ed! Many unexpected little details hiding in there.
Edit: Adding the photos here for posterity.
Flipping the tweemid module over I can get that misalignment to 120-ish mm. Seems pretty reasonably to me.
Also I recently learned that the crossovers are 700Hz and 3kHz. 700Hz is pretty high (for voice) so the 2×2 woofer config is here to stay I think.
First sketch of the box. Plenty of room to spare, inside volume is 43L at the moment. According the BeoWorld the Penta has a “net volume of 32L”.
Not including the tweemid sticking out, the box dimensions are 534W*319L*330H. It will shrink in the next few iterations as I learn more about the original but I’d love to hear if it should morph one way or the other proportionally (for non Ikea Kallax applications for example).
Really didn’t like the look of the thin chamfered ring elements on the two outer most midranges. I lifted these, roughly, from the original tweemid module.
Decided to redesign the whole module with a bit more of an integrated appearance in the surfacing department. Still working out some details but this new version seems easier on the eyes.
The woofers are placed together in order to reduce any comb filtering. I don’t currently have a bunch of off-axis listening positions in the room yet but we are still decorating and the couch is about to be swapped out for a much larger one where one might be seated very far off axis.
I did a quick sketch showing the current alignment. Currently the midrange array is only 173mm off axis. The listening/viewing distance is quite long (I’ll measure it later) so I don’t think this misalignment is significant at the moment.
I should add, my TV is quite large – 75 inch nominal size.
