Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 23 - diyAudio
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Old 17th March 2006, 11:16 AM   #221
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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
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Old 17th March 2006, 02:15 PM   #222
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Quote:
Originally posted by GM


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
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Old 17th March 2006, 02:45 PM   #223
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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
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Old 19th March 2006, 04:28 PM   #224
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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
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Old 19th March 2006, 05:08 PM   #225
GM is offline GM  United States
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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
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Old 20th March 2006, 04:57 PM   #226
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http://www.partsexpress.com/projects...e/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.
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Old 20th March 2006, 06:45 PM   #227
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Flames on the speakers. Excellent. You must be a fun
dad. They'll drive you out of the house playing Teddy Bear's Picnic.


:-)
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Old 20th March 2006, 07:15 PM   #228
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LOL... my 8 year old son was switching between Tom Waits and Joni Mitchel the other day using the headphones... sounded pretty sibilant thru the headphones... it's a cheap Cody???

He was humming along.. HA!
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Old 20th March 2006, 07:39 PM   #229
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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?
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Old 21st March 2006, 01:14 AM   #230
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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?
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