Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

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#2,961
Godzilla said:
One problem having the BIBs in a small listening room is image size. The BIBs throw a very large image which totally overwhelms the room sometimes. For example, James Taylor Live sounds like the musicians are on a stage 50 feet wide. The sound of the audience applauding is huge. This CD has a warm, lush sound. Also on Fleetwood Macs live album Dance, the stage also seems very large. This CD is a bit bright. Sitting in a room I know is 10 feet wide doesn’t help unless I close my eyes and relax. So I need a proper chair for the room. Smaller scale performances can be very convincing. Regina Spektors On the Radio sounds very real putting her and the piano in the room with me. Diana Krall, Eva Cassidy, Holy Cole, also sound scary real. The image the BIBs throw into the room is up, down and all around.
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😀
 
#2,962
just another quck question, 🙂 do you think the new Tangband W4-655A....

http://www.spectrumaudio.de/breit/tangband/tangbandW4655A.html

Nennimpedanz/Gleichstromwiderstand: 8/6,0 Ohm
Resonanzfrequenz: 70 Hz
Gütefaktoren(Qms/Qes/Qts): 4,35 / 0,36 / 0,34
Äquivalenzvolumen(Vas): 5,1 Liter
Effektive Membranfläche(Sd): 57 cm²
Antriebsfaktor(BL): 5,73 Tm
Schwingspulenüberhang(Xmax): 3 mm

will work in the BIB for the Tangband W4-1320SB

Nennimpedanz/Gleichstromwiderstand: 8 / 6,8 Ohm
Resonanzfrequenz: 75 Hz
Gütefaktoren(Qms/Qes/Qts): 1,50 / 0,48 / 0,37
Äquivalenzvolumen(Vas): 5,99 Liter
Effektive Membranfläche(Sd): 57 cm²
Antriebsfaktor(BL): 4,8 Tm
Schwingspuleninduktivität(Le): 0,01 mH
Schwingspulenüberhang(Xmax): 3,0 mm

From the BIB website.......
Tangband 1320SB 4" Bamboo
-L = (Line length) 100"
-Zdriver = Driver 20" down from sealed end of cabinet
-Sm = 38"^2

thanks 😀
 
#2,964
thanks, could not get it to work for me though, is this right?

for the Tangband W4-655A

Fs = 70 Hz
Vas = 0.18 ft^3
Qts = 0.34

L = 13464.54/2/70 = 96.175"
folded height = 96.175"/2 = 48.09"
Vb = 20*0.18*0.34^1.25 = 0.93 ft^3
Sm = 0.93*1728/96.175 = 16.7"^2

i keep getting a really small Vb and Sm :xeye:
 
#2,973
GM said:

L = 13464.54/2/70 = 96.175"
folded height = 96.175"/2 = 48.09"
Vb = 20*0.29*0.445^1.25 = 2.10804 ft^3
Sm = 2.10804*1728/96.175 = 75.751"^2
depth = SQRT((75.751*SQRT(2)) = 10.35"
width = 75.751/10.35 = 7.319"
zdriver = 96.175*0.217 = 20.87"
a-b-c = 10.35/2 = 5.175"
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GM said:
Greets!

Well, you did the math right, but with a small Vas (especially a fractional one) you need to round off with several more decimal places, which in your case is going to more than double 'Sm'.

GM
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Greets!

Well, this is what I get for making a snap judgment based on what a program calcs. :headbash: The example I did had a wrong formula, but the right answer since I just copied it from a calculator, so at least the sim is OK. You followed the formula without noticing mine had a wrong answer, so got a wrong answer. 🙁

I posted Sm = 2.10804*1728/96.175 = 75.751"^2, but we're only interested in its gross Vb, so to get 'Sm' we need to divide it by its folded height, or 48.088" in both my example and your design, so for my example:

Sm = 2.10804*1728/48.088 = 75.751"^2

WRT to my snap judgment about using extra decimal places, just ignore it since the difference is actually acoustically insignificant. 🤐

GM
 
#2,976
Q for GM

--is there any merit to the idea of a bipole BIB for the 4.5 drivers mounted on the wide side, magnets physically connected?

Would you double Vb?

The increased SPL would also be nice giving you ~92db speaker, and enhanced ability to contour, lifting the lower response abit. I am thinking bipole HempTone 4.5, floor loaded, wide baffle, stylish design, like TC's108 BIB sideways...

Thanks as always for your sagacity:wiz:
 
#2,977
Greets!

Yes, closely coupled magnets are a plus since they slightly increase motor strength and have the side benefit of acting as mutual bucking magnets, creating a shielded composite driver if needed, and of course the bipole layout cancels out most of the driver's rocking vibrations, though this is probably moot with 4.5" FR drivers as long as the cab is made from typical high quality plywood. OTOH, small, limited Xmax drivers in a bipolar layout allows the use of a thinner than normal material thickness, maybe putting more exotic materials within the budget.

Yes, double Vb.

Since I prefer acoustic solutions to acoustic problems, I always espouse having plenty of acoustic gain for tuning flexibility. Obviously, this typically costs more than electrical EQ, but unless it's a near-field or MUZAK app the lower distortion achieved is well worth it IMO.

Wide baffle bipolar floor loaded folded pipe horn....... my kind of efficient, simple to build DIY speaker! 🙂

GM
 
#2,978
I thought you might like that idea...

I too would prefer acoustic solutions, as always, however, in a "drag and drop" world, contouring can be fun for the whole family.

"Candy is dandy, but liquor is quicker" --Ogden Nash

pretty much sums that up.

Folks, the Tone Tubby HempTone(tm) 4.5's are a REAL eye opener. Four of these in the aformentioned build looks like one of The Best compromises I have yet seen, over a long time. The drivers are expected quite soon, I believe. They are this shape and color 😀
 
#2,979
Scottmoose said:
Another option though that could be very interesting: the Tang Band W4 1320SB bamboo coned 4" drivers. Their specs look excellent (and that's a real compliment, coming from me), and perfect for a scaled down version of this TQWT (they look cool too!). They cost $40 each, about mid-way between the Pioneer and the Fostex, so could be achievable on a small budget.

Try with these cabinet dimensions (assuming 3/4" build material) of: external depth: 10 1/2". External width: 5 1/2". Cabinet height of 60" and an overall line length of 120". Driver mounted 31 1/2" from the base. That's a bit long for them, but the original cabinet was over-long for the RS drivers, and as these Tang Bands have a very considerable 3mm Xmax, they should be OK with the load, and also have enough excursion to produce reasonable bass. I'd guess a cut-off point of around 40Hz in-room -not bad for a little 4" driver methinks. In fact -I think I'll buy a couple myself and give it a whirl. And no, I'm not joking!

Cheers for now
Scott
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Did you ever build these Scott? You did mean 31 1/2" off the floor and not from the sealed end right?
 
#2,980
Bib tweak update attn: GM

Today I went to the billiard supply place
and asked if they had any cutoffs, roll ends or
the like for making pennant- shaped felt baffle.
The guy said they keep most of the trim for doing
rails _but_ he found one piece and the long side is 53
inches which looks to be just about enough for
the length of an FE127e BIB.

Any final suggestions before I cut cloth?
 
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