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
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
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
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
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
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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
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
Thanks Chris. Yeah, after three rounds of antibiotics the leg finally healed. MRSA is nasty stuff. Wasn't able to do a veggie garden this year, etc. I'm really glad I'm able to get back to doing fun things again.
I'm building the BIB's out of OSB as test cabinets since 100 bucks of chipboard to test out a loudspeaker idea is a lot less expensive than five or six sheets of high quality plywood. This week I'm going to line parts of the enclosures with wool felt, stuff the peaks with acousta stuf, put a layer of it on the bottom as well and hopefully I'll be able to put the final sides on the cabinets next weekend. With the JBL 2220 midwoofers they should be right around 101db 1W/1M! Think they'll make bass?
Assuming the OSB doesn't buckle! 
MRSA is indeed nasty stuff! Doing phys-ed on my left arm [I'm a lefty] and right leg from an attack earlier this Spring that did a lot of nerve damage, so another year I thought I could finally get caught up on property maintenance, maybe finally do a bit of speaker DIYing 'down the tubes'. Thankfully got some really good neighbors, so at least not having to pay 'robber baron' prices to do yard work, etc..
Regardless, glad you got it wooped and able to resume this bodacious sub system!
GM
MRSA is indeed nasty stuff! Doing phys-ed on my left arm [I'm a lefty] and right leg from an attack earlier this Spring that did a lot of nerve damage, so another year I thought I could finally get caught up on property maintenance, maybe finally do a bit of speaker DIYing 'down the tubes'. Thankfully got some really good neighbors, so at least not having to pay 'robber baron' prices to do yard work, etc..
Regardless, glad you got it wooped and able to resume this bodacious sub system!
GM
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Well, if you're building the sim I did, 18 W in stereo up against a decently massive wall sims > 125 dB from ~27 Hz, so if just an inside wall they may not load well down low, but mid-bass will be loud live concert level. Just the thing for hard rock, heavy metal, etc..
This is pretty decent pressure, so definitely need divider board cross bracing over ~70% of its axial length beginning at the throat and mouth ideally and with driver bracing.
GM
This is pretty decent pressure, so definitely need divider board cross bracing over ~70% of its axial length beginning at the throat and mouth ideally and with driver bracing.
GM
Thanks! When they were laid down on the saw horses I didn't really get a sense of how big they were until I stood them up on end. I have a picture of a couple of friends of mine standing inside them with room to spare!
I don't plan on playing them that loud but I'm going to be hooking them up to a pair of W4-AM monos which put out around 20W per channel. I'm thinking of converting them to 6B4G's as it looks like I can just alter the bias and the tubes will plug right in. The output transformer is 10K center tapped so I can just use the 16 ohm taps with these 8 ohm speakers.
I definitely plan on installing some bracing.
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