Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 472 - diyAudio
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Old 17th November 2010, 07:58 PM   #4711
TerryO is offline TerryO  United States
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Quote:
Originally Posted by Pit Hinder View Post
GM, ALL of his scenarios are posssible, that´s what makes his books so frightening - forget the movies, they are dumbed down, keep reading the books.
I also like his books. Micheal Crichton studied medicine, although he has never practiced Medicine. I believe he began writing to pay for college, and by the time he graduated, he had become so successful as an author that he never turned back.

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TerryO
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Old 17th November 2010, 08:24 PM   #4712
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Yup. And his first book couldn´t be filed under "SciFi" - it was about it being impossible to have an abortion in Boston unless your parents were rich or MDs.
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Old 25th December 2010, 03:02 PM   #4713
rt68 is offline rt68  France
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Default Ikea BIB

Since a few months, we’re the proud owners of a pair of self-hacked Ikea BIBs with the new, strange-looking, Tang Band drivers.

Motivation. Our toddler was reaching for the drivers of our stand-alone loudspeakers, and we have a need for space and simplicity. We own Billy bookshelves and Benno CD/DVD elements. The choice for the BIB was made because they work against a wall, and the Ikea orientation because we wanted a design that integrates well with our bookshelves.

Design. The IkeaBIB is made by combining a Benno with a Billy. For two cabinets, you need three Bennos and two Billies (the 2,02 m tall version). The sides of the Benno CD elements are used as baffle, centerboard, back, bottom and plinth, all clamped and glued between the sides of a Benno. The ratio of this cabinet is close to 1:sqrt2. The maximum internal height is 1,92 m if you keep the plinth design of the BIB similar to the Benno/Billy variety. It is possible to shorten the length of the internal column to adapt to drivers with a higher Fs, you only need to keep an eye on the position of the driver with regard to the listening plane. The mouth area (Sm) of this design is about 63 sqi.

Drivers. We bought a pair each of the new Tang Band W4-1879 (Fs 55 Hz; length 1,56 m; Sm 63 sqi) and the W5-1880 (Fs 45 Hz; length 1,9 m; Sm 103 sqi).

Assembly. We kept it simple. With 1,92 m internal height, the cabinet is tuned at 45Hz, a little low for the W4, but still above the absolute minimum. The Sm is a perfect match for the W4. The W5 driver nicely fits the length of the cabinet, but would need a much larger Sm. All elements we used for construction come from the blue and yellow place. The spacer and baffle for the driver mount are made of a sandwich of chopping boards, and the fabric we glued to the front is cut from a panel curtain.

Contemplations. The loudspeakers are flanked by bookshelves that have the same height, but that have an additional top cabinet. We do not know if this extension of the “side wall” influences the coupling of the horn to the room. Does it lengthen the horn? Does it increase the effective mouth area? Some posters proposed diagonal mouths to the front, to the back, et cetera, but without comparison or measurement data, the merits remain speculation... In our case, the design was more or less set by the rules dictated above, and these circumstances would not change, so we decided to forego the speculation, but take the plunge and just build the things.

The sound. We have been running them for about two months now with the larger W5 driver in place (the W4 is still packed). The low end: if you've read this thread, no news. We do have the impression that there is a sag in the frequency response in the next octave band, but we don’t know whether that is the room, the placement or the lacking Sm. Our room does not sound particularly good with anything anyway.

On-axis, these Tang Bands sound transparent. Voice sounds uncolored and balanced. Off-axis, however, the sound becomes fuzzy, hazy and colored. They beam too much: with the loudspeakers flat against the wall, flanked by the Billy bookshelves, there hardly is any sweet spot at all… Maybe we still need to add more or better stuffing in the top and behind the driver to clean the mid-range, but the fuzz will unlikely go away.

Careful conclusion: it's the driver, stupid. Low end is a given in a BIB (minus some swings in the lower mid base…). For the rest, it is all about the driver's character. The choice for the new TB series was sheer curiosity – without one real-world review, and fueled by several threads filled with precise opinions, we figured they would be either good or bad, but certainly interesting. And now we know they probably are or at least can be all of those, depending on your application and disposition. With regard to the Ikea design, there is not much we can say. Can one build a better cabinet? No doubt. An easier cabinet? Don’t know.

Next steps. We'll try the W4 in the new year. We do not expect them to sound much clearer in the listening position, although the cone is flatter, so who knows... It will certainly be an interesting exercise to see if it tells us something about how length and Sm relate to each other. After that, we might think about trying a 168EZ or an Alpair 10 or 12, but since we do not know the sound any of these either…

One question. Could someone explain how we could remove the interference diffuser and perhaps also the cone diffuser? I'd like to better understand which part does what to the sound, but I'd hate to destroy the driver. Any suggestions are greatly appreciated.

Finally. A BIG, BIG thank you to all that contributed to this thread. You know who you are. Without the abundant amounts of information, knowledge, calculations, big lines, details, speculation, nonsense and jokes, we would never even have dreamed of embarking on this adventure. If not for this forum, we would now be listening to an old pair of Celestion 3’s tucked away between the books. Now, wait, eh… would they fit in this BIB?

Happy New Year to all.

Rt68

PS: A few images...

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Old 25th December 2010, 04:47 PM   #4714
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Very interesting. Let us know how the W4 turns out. It looks on paper to be a great driver for a BIB. That 55 Hz. is unusual for that size driver. Happy holidays.
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Old 25th December 2010, 09:50 PM   #4715
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Originally Posted by rt68 View Post
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Wonderful
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Old 26th December 2010, 04:52 AM   #4716
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Enjoy them! They are unique in every way!
Zilla
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Old 27th December 2010, 09:08 AM   #4717
rt68 is offline rt68  France
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Default wow, comments

@ motosapien: good point. your comment is an encouragement for driving past 'the store' for another set of chopping boards. will do so in the coming weeks.
@ krisrleifur - and, as you know, the acoustical feature in the baffle board challenges any cable modification one could think of.
@ Zilla - unique - nice ;-)
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Old 9th January 2011, 04:01 PM   #4718
rt68 is offline rt68  France
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Default W4-1879 update

Today we got to mounting the 4" versions of the new TB drivers.

2 observations:
- the mid base is completer, but the really low end obviously not the same as the W5. We suspect that the overall base sound is completer due to the better match with the Sm of the cabinet - less of a gap. The undertuning of the system does not seem to bother the 4". A plucked low E is there, not at full output, but pleasantly present. Impressive for a 4" driver...
- they beam less than the W5 version, but they still beam somewhat. The imaging is better than with the W5. When played-in, they could be quite nice, but we may become tempted to develop an Ikea subwoofer...

Alas, the fun with the 4" drivers was shortlived. During testing we found one of the drivers to sound distorted in the lower mid range. Turns out that the driver slightly touches the cone... so much for QC at TB. Hope we can still exchange the driver, but it may take a few months before I'm back across the pond.

Will post pictures of the driver and also a close-up of the cone later.
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Old 9th January 2011, 06:45 PM   #4719
rt68 is offline rt68  France
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Default Ikea BIB with W4-1879 image

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Old 9th January 2011, 06:50 PM   #4720
rt68 is offline rt68  France
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Default W5-1880 cone image

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Here a close-up of the TB confusor on the W5. The aluminum cone is flat with rounded edges. On the W4 they are chamfered, but only 30 degrees or so. If anyone cares, I'll try to take an image with daylight and a tripod.

Does anyone have a suggestion how to remove it (and replace it with a regular diffusor cone)?
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