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GM
diyAudio Member

Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
 Originally Posted by freddi although not simmed correctly*, it looks like a BIGBIB with 2220 would do 100dB- 102dB@30Hz 1 Pi 2.83v w. ~440 liter internal airspace, assuming the older alnico "A" is close to "H" in spec. (* - used a 4.25M long positive flare T-line with 0.41 offset for that guesstimate)
​Sounds about right, my [parabolic] BIB sim is ~890 L/4.65 m long and averages ~108 dB/30 Hz/m/1pi/2.83 V, though again it's probably going to be lower due to HR being a bit optimistic unless it's one heck of a well sealed, massive/rigidly constructed, space.

GM
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Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 12th October 2018, 10:01 AM #62 freddi   diyAudio Member     Join Date: Aug 2005 tried another but don't have a grasp of how to do it this time I set the horn area at 0.41*path at Sd (does that make any sense??) - then just adjusted things so the schematic looked what assume is about the right shape to finish the expansion I feel like I've been to the Pa Kettle school of mathematics and flunked tell me how to do these BIB things
 12th October 2018, 03:09 PM #63 GM   diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. Instructions: The BIB default alignment is Fs/2, so input Fs, Vas, Qts' and it auto calculates everything you need to input it into HR/whatever. The basic math is: Vb = 20*Vas*Qts'^1.25 Qts' = Qts + any added series resistance [Rs]: mh-audio.nl - Home If it's too short or too long, i.e. too far from the ceiling or too close, then change 'Fs' until you get the desired folded height. For really high Fs drivers or just want a smaller floor loaded model, just change 'Fs' to suit. If it's sheer size/'footprint' is too big for the intended app, then change Vas for relatively minor adjustments and/or Qts' for major ones, though may not adequately protect the driver enough in high power apps. L*0.217 is the original/standard driver offset with L*0.41 being MJK's alternate when a flatter overall response is desired, though may not adequately protect the driver enough in high power apps. For compression loaded, i.e. very close to the floor or ceiling, then one of these ML-horn/ML-TQWT driver offsets may be better overall, though again, the further down the less the driver protection at higher power: L*0.349, 0.424, 0.50 - 0.60 GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents. Last edited by GM; 12th October 2018 at 03:12 PM.
 12th October 2018, 11:39 PM #64 freddi   diyAudio Member     Join Date: Aug 2005 is that QTS' ^1.25 "separate"? I got a huge figure (like 35 cubic feet) with QTS'= 0.241 (rg = 2ohm) and 2220A's Vas of 297.3 liters
 13th October 2018, 12:43 AM #65 GM   diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. No, ~35.46 ft^3 is correct. Conical pipe horns mostly load by air mass volume alone, so air not being very heavy............. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
 13th October 2018, 01:05 AM #66 freddi   diyAudio Member     Join Date: Aug 2005 hey GM - I certainly appreciate the info and clarification - add some wood to 35.46CF and that's a whopper. 4 ohm Rg would raise 2220A QTS' to 0.3. A K alignment formula might be handy too - think they're only relegated to certain size limits. Last edited by freddi; 13th October 2018 at 01:09 AM.
 13th October 2018, 02:11 AM #67 GM   diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. You're welcome! High time I consolidated all the info I posted piecemeal as required. Apparently these cab alignments aren't ancient history just yet. Judging by the HR sim, one could probably do well enough with ~35*0.707 = ~25 ft^3, just will have several dB less power handling down really low where the room may already be boosting too much anyway. The extra acoustic loading I factored in was more for 'FR' drivers where even Fs/2 with next to nothing power handling was going to normally be > 20 Hz. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

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