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Everything posted by Ricci

  1. Making the cabs smaller will reduce the efficiency and sensitivity a little. Should not affect the FR shape or extension much. It's only 10mm. Make sure you check that the driver will still fit after subtracting 10mm though. A 21" driver frame is already very tight in this box width. Have you thought about adding a bit of extra wood to hold the grilles instead of modifying the cab width? I'm interested in seeing what you have going on with the steel baffles too. Good luck! I will see if I can get a hold of Kyle about your picture bandwidth questions.
  2. With 726cm of vent area and 35m/s max velocity, port compression should be minimal. If I had to guess I'd say about 2dB port compression and that is only at maximum output. Reducing the output 3dB does wonders. I hope no one is running cabs at maximum! If you do you need more cabs. Airspeed will grow with the lower tuning options. There is nothing that can be done about it due to the physics. Have you read Collo's works and the JBL whitepapers on ports? One take away is that larger vent area will support larger air speeds with less chuffing and compression. With the modern hi
  3. Sort of but it's more complicated than that. HR considers each boundary an infinite wall. This isn't true even with a bunch of cabs outdoors.
  4. Hey Kipman... the port area listed is exactly what the area of the vents are. There is no fudge factor. Your calculation must be off a bit. 24" width, two 18mm side panels and three 12mm vent dividers. Length is 102cm effective calculated off of the sketches inside of Solidworks. Of the port calculation styles you linked only the 3rd and 4th from the left are worth using. Mixing #3 and #4 is worthwhile. The rest are inaccurate. I've designed, built and tested a bunch of designs with similar ports and that's how I've determined what results in a close match. Use #3 from the attachment for
  5. Also that's a bunch of BLUE subs!
  6. The primary mechanism will be 8 bolts into the baffle face with inserts, or screws could be used. 3 other screws would come into the end grain of the cover struts. 1 each through the 2 sides and the top. The holes would be pre-drilled to avoid splitting. A 4th would be pre-drilled and run at a 45deg angle into the vent panel. The main holding force would be the fasteners into the baffle. The other 4 screws would mainly be to keep those 4 struts from vibrating. As shown here.
  7. I already factored in the extra proximity effect when I made my comments. That panel will need to be about 26cm to get the effective vent length in the sim. Looks like it is about 18 -20cm at most. Port bracing should always be accounted for. It reduces your effective vent area and multiple vents also tune a little higher than one big vent. At the end of the day we are probably talking a difference of a few Hz difference in the tuning, but even that can make a difference. S1 starts at the wall where the panels pinch together. Do you have 8 or 9 cm there before getting to the
  8. Do you still have the SKRAM? I'm interested. I need to get one to test.
  9. I think you are the first person who has said that the chest pound is missing. Is it possible that what you are looking for is occurring in frequencies that are above the sub band? What some guys would refer to as the MBM range (100-200Hz) Are you using them outdoors, at home, big venues? Is it possible that you have acoustics issues contributing?
  10. A couple of things that I see to double check. Not sure the horn section has 133cm of length? It's a little hard to judge from the drawing scale. Could be close. Also seems like the L12 length of 37cm is possibly a little too long. SKRAM is 28cm. Is there an extra 9cm length there? Again hard to tell for sure from the drawing. I think you may need 2 or 3cm more on the overall height to get the overall volumes in the sim. Depends on bracing, etc... though. Vent doesn't look long enough to effectively be 96cm to me? Based on your dims and port area provided the panel that
  11. I use the Voxengo spectrum analyzer as an investigative tool for mixing sometimes. How is the delay plugin?
  12. Thanks for letting us know. At least you tried.
  13. Yes. It's not that the LW1400 would not work, but it would not be my first choice and I would want to be careful with the overall volume until figuring out what it could take.
  14. It's probably not a huge issue but I have seen a number of drivers with large shifts from coil center. Some were current drivers. I left a JBL 2269H sitting on it's face with 700g+ of magnets on the cone for a year to get it back to center rest position. It was probably 5 or 6mm inwardly set when I got it. It can and does happen. Back in the day it was probably a bigger issue with much shorter xmax and looser suspensions. On a modern woofer with 15mm xmax and a really tight suspension an offset of 1 or 2 mm isn't a big deal. Be more careful on drivers with a softer suspension, shorter xmax an
  15. LW1400 has a cone that is rather light and flexible for a 21". I'd be careful putting it into a cabinet which increases the pressures on the cone. S1 has a marginal impact in this type of design. Whether 300cm or 30cm. I wouldn't worry about it much. Especially at the cost of making the cab heavier or more complex.
  16. Should be fine. They are more similar than different. This one just has much less path length and gain from the front section to keep the size down.
  17. Not sure yet. Likely to be better than a direct radiator but not as good as my other designs since the driver is so close to the exits and visible from some angles.
  18. That's one of the tradeoffs of this arrangement. Could always flip them once a year.
  19. Have you considered an arrangement similar to this?
  20. Droogne, Since you have additional height you can work with, that helps immensely. 60x65x100cm should be enough for a hybrid 6th or whatever these are called lately. Keep your HR sim at about 285L and you should be in the ballpark. Keep in mind that air volume is limited and any volume taken up by the front section has to come from the back section and the ports. A bigger front section= less low bass / higher vent velocities, but can produce more upper and middle bandwidth output and lower air velocity in the front section A bigger ported chamber and ports is the exact opp
  21. Lucky dog! Quite the "toy" collection there.
  22. Since the 21DS115 is 2.2 ohm DCR I usually do consider it as 2ohm nominal. Voltage sensitivity is a tricky subject since speaker cab impedance is all over the map. Still useful but not as much as many make it out to be IMO. With that said I was trying to maintain 95ish dB at 30Hz from this cab with nominal 1W voltage. The size makes it difficult. The Edge sim was for a single cab. I threw it together quickly. A mirrored cab shows about 1dB of gain at 40Hz another 1dB over the single cab by 70Hz and an additional 1.5dB 100-200Hz.
  23. This question has a rather complicated and long answer. The simplest way I can explain it is that the S1 value is the minimum cross sectional area of the air volume in front of the driver cone at the center dust-cap. Technically there really isn't an S1 as typically defined since the driver radiation expands in 360 deg in that axis. The driver is placed in an OD rather than ND arrangement but the exit is closer to an ND arrangement. In some ways it is also similar to a traditional ported bandpass chamber. I modeled it all three ways and surprisingly there is little difference between the
  24. I wish we were closer I'd take you up on that! Especially after seeing those shop pics. Honestly I have a lot of educated guesses about the top end behavior of the front section but little in real data. It should be predictable in the bass range. Outside of that who knows...Disc diameter is 20.5" so there shouldn't be any cancellation issues until well outside of the sub range. Here's a couple of FR images. Akabak sim with the front section separated into 8 waveguides each with 12 or so segments and the 4 vents all modeled separately. The comparison FR is from HR. The two are
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