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

Glad you're OK with it Terry.

OK -consensus is achieved. I'm not about to ignore Greg's advice, so I'll shift to using internal dimensions. Also, general opinion seems to be that the F/R plots are wanted, so I'll begin to post those too. Remember that the suck-out in the mid-bass and the response ripple / comb-filtering (particularly the latter) are greatly over-estimated. Fair point though -they are useful to give a general idea of the response curve.

Best
Scott
 
GM said:


Greets!

Its Fs is too low, but doubling CSA and adding an 8" x 8" vent yields 95 dB half space eff. down to 30 Hz. Not too shabby for a 10".

GM

Those are pretty amazing specs for a cheap sub. You could practically use a passive x-over with many fullrangers (not that you'd want to.) Too bad those from the sub forum won't likely venture over here. It seems to me that one could fold a sub another time if needed, as driver height (from the floor, not position in the line) really doesn't matter much.

Paul
 
Greets!

Yeah, you can fold a sub up like a pretzel without affecting its intended BW. Indeed, it's an advantage since it will acoustically damp the line's HF harmonics into a ~bandpass looking alignment. I did a folded up corner loaded Adire Tumult ML-Voigt that was near 100 dB efficent/16 Hz and rolled off above ~150 Hz. Acoustic gain and small size is mutually exclusive though, so even folded up it was much larger than most folks will tolerate.

GM
 
GM,

Good Morning. Is the enclosure you described in post 194 a MLTL?
Am I correct in assuming that I need to stuff the line from the top to just below the driver with wool or similar material on the order of .25-.50 LBS/CU FT? Do you recommend lining the internal walls with felt? Does this enclosure require internal bracing? Thanks for the info. I mocked this enclosure up in cardboard and it fits perfectly in my listening room. I am ordering a pair of Hemps tomorrow and will start construction next weekend. Will report back when finished.

James
 
Greets!

Technically it's a corner loaded 90 deg wall angle conical horn with an acoustic pathlength = to whatever the ceiling height is plus an end correction, or ~35 Hz for an 8 ft height.

I would start with just a 1" thick layer of acoustic fiberglass on the top, back, and down one side about half-way.

You always want to brace the driver area (I either use dowels of a double thickness baffle with the backside chamfered at ~45 deg) and driver, and the top is where most of the pressure is in a pipe, so doubling up or adding a massive decorative top of marble or similar is a good idea, but the CSA is >12" square, so as long as it's built out of at least 19 mm no-void plywood you're fine.

GM
 
http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm

Fs 104 Hz
Qms 5.021
Vas 3.27 L
Cms 0.721
Mms 3.2 g
Rms 0.421 kg/s
Xmax 1 mm
P-Diam 84.85 mm
P-Vd 0.00565 L
Qes 0.915
Re 6.9 ohms
Le 0.58 mH
Z 8.3 ohms
BL 4.0 Tm
Qts 0.774
1-watt SPL/m 88 dB

Does the NSB 49 cent driver lend itself to a BIB? I have 10 of these and want to build a BIB for my kids room. My 8 year old won a portable CD player at the arcade for his 5-1/2 year old brother and they want to build a stereo with it as the source – and a cheapo SI amp to power it all.

They want to paint flames on the cabinet.
 
I finished building a pair of BIBs. Size is 70" x 12" x 18". Thus far I've tried Fostex 208EZ and 168 Sigma, Visaton B200 and Lowther DX55. Later I will try F200A and Axiette.

I know this is not the ideal approach to optimize a particular driver. However, I like the idea of larger cabinet that would let me try different drivers, especially since I don't have cabinets for all of them.

The bass loads quite nicely in my room with all the drivers, save for the Lowther 5". However, I think there is a suckout/thiness in the midrange (that GM was alluding to when using the 8" ers). Fostexi seems the best balanced, but uninvolving. Visaton has a definite suckout, and overpowering bass output. Lowther, is fast, clear and exciting, but alas not enough bass. A coil in series helped a lot and this is what I'm listening to now.

However, I was thinking about two possible non-electrical solutions:

1) Front loading the Lowther with the hope of boosting the midrange while at the same time rolling the trebel and/or

2) Adding another driver (as previously mentioned).

Any comments?
 
Your experiences tally with mine, though I've never personally found Fostex units boring... the suck-out will always exist to an extent due to the driver position, though it's usually around 100-200Hz, give or take 20 or so. Front loading the Lowthers could be interesting. Not something I've looked into though. The original 208Sigma or the new 206ES-R could be possible options too. I've a pair of Lowther PM6Cs on order for testing in various enclosures too...

Godzilla -the Fs is too high for a large enclosure (well, a long one anyway). You could build a rather short pair though! Make for an interesting stand-mount!

Best
Scott
 
My BIBs internal dims are 71" x 10.5" x 15.5" and with the B200s the bass is overpowering, which makes suckout more apparent. The suckout can be mitigated by moving the BIBs away from the corners. However, in an unexplainable way produces "fun" sound. Just don't critique the sound, like listening to Ray Brown's the bass go bim and then BOOOM(!).

bimBOOOM!bimBOOOM!bimBOOOM!... fun but not realistic.

Based on GM's tips, the cab must "swamp" the drivers vas, fs between 40Hz to 50Hz, and in the original BIB driver size should be around 5". GM recommended doubling the originals width for the Hemp FR8, which has a similar vas (big) and surface area as the B200. So, you are looking at a Super big BIB cab.

The little Lowther produces the most interesting sound. The tradeoff is less bass extension. Mr. Lowther said that Lowther recently changed the suspesnsion producing more bass.

Scott, please post your results with the big Lowthers when you get them. I suspect they might work really well in the BIBs having smaller vas then B200 and less x-max.
 
Godzilla said:
http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm

Does the NSB 49 cent driver lend itself to a BIB?

They want to paint flames on the cabinet.


Greets!

Flames, cool! My first paying 'job' at age 12 was painting flames on various folks cars, cycles (both bi- and motor-), several hotrods, bowling bags, and even a couple of mailboxes! Great way to learn how to use the airbrush and touch-up gun I got to paint my models. Fun times! :)

Anyway, give it a try, it looks as good as the BiB sims except tuned higher due to its higher Fs. The sim is solid to ~55 Hz, so in-room should make it into the 40s easy if the specs are reasonably accurate:

L = 84.5"
open end = 55"^2
driver down 36" from pointy end

Due to its length, leaving it straight with the pointy end on the floor and fabbing a stand to support it is probably best.

GM
 
one1speed said:
That's pretty cool. You know, I wonder if you could do a BIB with 3 or so drivers per side. Would that work out? Or would time delay become an issue?

Greets!

It's not my 'cup-o-tea', but some folks don't find the 'phasiness' objectionable, so as always YMMV. You can always use a 2nd order XO around 4 kHz if its too distracting. Due to the extra displacement though, you could tune it lower and EQ it flat to amaze folks with how low dinky little high Fs drivers can play.

GM
 
ultrakaz said:

1) Front loading the Lowther with the hope of boosting the midrange while at the same time rolling the trebel and/or

2) Adding another driver (as previously mentioned).

Greets!

1) If there's not enough bass, then a FLH will just make it sound much more bass-shy.

2) This is what I'd do, maybe even two to ensure they have a similar 'attack' as the Lowther.

GM
 
Corloc said:
I'm wondering if someone could spell out the dimentions needed for the visaton B200 in BIB. I fond GM's sugestion to Scottmoose, but I'm not sure of the folding or the driver position.

Chris

Greets!

I assume you mean this ML-TQWT (not BiB):

L = 113.38"
SO = 2.036"^2 (terminates to a point actually)
SL = 265.464"^2
xO = 0.6825 (77.38")
density = 0.2 lbs/ft^3
rp = 3.25"
lp = 1.5"

You fold it in half and the driver will be 36" up from the bottom on the side with the vent. IOW it's way down the pipe due to the very high aspect ratio of ~130.38:1. The vent is so large, just make it full width at the bottom with a 1.5" top ledge/stiffener. Divide 33.138" by the cab's internal width to find its height.

GM