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

Jump to Latest
#4,242
opinion

I've proceeded to to give the peak some stuff (pretty tight) and
the bottom a bit-- very light in comparison.. not compressed at all.

The only difference in that treatment right now is behind the driver.

The Big Bib is surprisingly flatter than the honkiness of the smaller build.

Also I'm trying to correct for soundstage which I get virtually none of.

But I want to correct the lack of flatness first.

The opinion I'm requesting is on the behind the driver treatment: could that be the sole cause of the difference?

Mounting is also different: one in the big cab is screwed down flat.
The smaller one is screwed down to washers to prevent bending
of the frame around the foam seal to the cut out.

Both builds are chamfered at the driver cut out.
 
#4,243
I had soundstage problems when I had mids leakage through the terminus. I use the BIBs one in a corner and the other in the middle of a wall, against that wall. Both slightly toed in.

I have stuffed from the point (quite tight) to about one inch under the driver (not too tight) with polyfill. The stuffing at the bend is about 2 inches polyfill, non compressed. I have a previous lining with 2-3 mm grey car felt, that I left there out of lazyness.
 
#4,245
ghpicard said:
I had soundstage problems when I had mids leakage through the terminus. I use the BIBs one in a corner and the other in the middle of a wall, against that wall. Both slightly toed in.

I have stuffed from the point (quite tight) to about one inch under the driver (not too tight) with polyfill. The stuffing at the bend is about 2 inches polyfill, non compressed. I have a previous lining with 2-3 mm grey car felt, that I left there out of lazyness.
Click to expand...

There is much less than 2 inches in the bottom (at the bend) now.
I have one change I want to do there.

I made up another one of these Pioneers with Damar on the cone-- for some reason I didn't do the dust cap-- and cut out 2 of the four basket legs. Cutting out legs is better done on a six legged driver I think, but it's something I wanted to try just for grins.

The cones on these are black. What would be a good white liquid and applicator to do a bit of EnAbling? White Out(tm) came to mind because I have some from typewriter days that is still sort of fresh.

:whazzat:
 
#4,246
loninappleton,

White out has been used, clear, low tack tape has been used (PDAN can tell you how) and acrylic model paint with pigment or without is being used. Applicator solutions have been numerous and if you are really good with a paint brush, that is one sort already tried.

However, the easiest to learn to use and one with considerable weight of experience behind it, is the tried and true calligraphy pen and Poly S flat, clear or pigmented, acrylic model paint, found in almost all train and plastic model hobby shops. Ed Lafontaine, here on the forum, has a kit of pen tips, holder and required chemicals, available for a very reasonable price. There are a number of sites that have a tutorial on how to do the spots successfully.

I have attached a text file with all known EnABL posts below, for your viewing pleasure.

Bud
 

Attachments

#4,248
not off topic yet

This is not extraordinarily off topic yet but picking through
all the EnAbl stuff is pretty daunting.

Let's face it: my mind doesn't work right jumping around like that.

So I am making that one here and suggest that the Enabl kit--
type that into search-- will take you to Ed La Fontaine's thread and
where to get Enabl stuff in a kit.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=119676


I'm still reading through the five or more pages in the kit thread and I bookmarked that.

Back on topic I installed my modded Pioneer cheapie with the leggs removed and the Damar job from this afternoon. No harm done that
I can tell but I have to set up a good a/b test to confirm any improvement.

It is sort of fun though-- if you have a few sacrificial drivers to
practice on.
 
#4,250
Some progress on the BIB Jr. for Pioneer.

I switched out the fiberfill at the bottom (bend) for some
egg crate foam. The foam is in there cut to fit pretty tight.

I'm still testing if this gets rid of the honk but still gives good horn action. On first listen the honk seems to have diminished significantly
but there are other music sources to check to know if good music reproduction is there too.
 
#4,251
Sawdustfull summer behind and I finally got my BiBs ready.

Speakers are 70inch tall as ScottMoose suggested, and I must agree they're not ugly at all.
Width is 225mm and Depth 545mm, which gives me little extra to low end.
With a little padding inside of them the sound they produce is excellent.

Summertime well spent, coverd with sawdust...
 

Attachments

  • speak1.jpg
    speak1.jpg
    34.1 KB · Views: 1,282
#4,252
mightym said:
GM, Thanks for your reply.

How about a columnar-in-the-corner M19 variant?

This would be rather difficult to achieve.........

..........is there any available weblink that might illustrate the proper uses of an WTW alignment..........

I've seen others refer to "comb filtering" and "lobing (?)"
Click to expand...

Greets!

You're welcome!

Not really, but if you're serious about pursuing this, then start a new thread.

Not aware of any per se, but where little tweeters are mating to large drivers, then you ideally need to be pretty far away from them as you can hear them as two distinct point sources and WRT multiples, that's best delt with by a bipolar layout with the rear one rolled off, i.e. 2.5 way to act as acoustic BSC.

'Comb filtering' is a summing of BWs far enough out of sync (phase) that they create a series of peaks/nulls 'sawtooth' type of response. 'Lobing' is when multiple sources are beaming the same BW, so it's what causes comb filtering. Even if they sum well on axis, if you don't have a flat power response off axis also, then comb filtering increases with increasing off axis angle, ergo either coincident or proper WG designs at least in our acute hearing BW is a worthwhile performance goal.

GM
 
#4,260
Yeah, it's a really simple, flexible design routine. There's some 'sub' BIB designs buried in the thread, maybe I can find them and get them split out into a separate thread where they will have more exposure. Frankly, the few pipe horns I built were all 'sub' horns with OTC 350 or 500 Hz XOs as I never considered them as viable for 'FR' drivers alone from a theoretical POV due to their excessive 'ripple' (by my standards). Apparently I was wrong.........

GM
 
You must log in or register to reply here.
Top Bottom