Hi there: Thanks for posting the link to your MLTL for RS 40-1354 and other small drivers. Any recollection of the T/S for the 1354 driver? Really liked your concept for acoustic BSC. I do not like the idea of hanging circuits on to a FR driver...defeats purpose of simplistic single driver FR IMHO. I'm sure todays highenders would insist on 25# of gold for mass loading. ...regards, Michael
You're welcome!
https://web.archive.org/web/20030804183041/http://melhuish.org/audio/parameters.htm#radioshack
Me neither and FWIW, they measured +/- 3 dB 40-12.5 kHz/half space on axis using MLS at the Meet where the photos were taken, so didn't do too bad using just my ears. Anyway, over-toe'd in a bit in room the crowd was pretty impressed, especially with how much [toe tappin' according to some] bass they put out in such a large carpeted room well away from any walls.
In the apt. and now a ranch style house's 'great' room along with about 16 yrs of near 24/7 break in, they are even better.
I have a pair tweaked like his that if I ever do any more building they will be in BIBs along with super tweeters to add some top end 'air'.
GM
Oooooh, we're finishing the last scheduled house project next weekend, so BIB-building-time after that!
Always takes longer, doesn't it? But it turned out nice and now it's time for some more BiB's.
Pre-finished particle board, standard sizes. Once I showed two sizes in a sketchup model of our living room (one for the 8" tangband and one for the 12" Eminence), my wife was foolish enough to say the bigger one looked better in relation to the furniture. Of course I jumped on that. Not much to design with these standard boards, although I still had doubts about bracing. I the end, I followed the Hobby Hifi guidelines, which state that a panel needs bracing if it's wider than about 10 times its thickness. I simply determined (ball park) where width exceeded panel width and put in some braces. I doubled up the front baffle. Driver mount is going to be a removable panel, because I want to be able to try different drivers.
Now it's just a matter of getting the boards, sawing to length, drilling lots of holes for dowels and glueing together. No outside screws this time, hope that works out. First time...
Pre-finished particle board, standard sizes. Once I showed two sizes in a sketchup model of our living room (one for the 8" tangband and one for the 12" Eminence), my wife was foolish enough to say the bigger one looked better in relation to the furniture. Of course I jumped on that. Not much to design with these standard boards, although I still had doubts about bracing. I the end, I followed the Hobby Hifi guidelines, which state that a panel needs bracing if it's wider than about 10 times its thickness. I simply determined (ball park) where width exceeded panel width and put in some braces. I doubled up the front baffle. Driver mount is going to be a removable panel, because I want to be able to try different drivers.
Now it's just a matter of getting the boards, sawing to length, drilling lots of holes for dowels and glueing together. No outside screws this time, hope that works out. First time...
Attachments
Playing with cabinet size
This may have been already covered in this giant thread, but a quick question - if a BIB is shortened in length (due to WAF), what is the likely impact? For example, for a driver with a Fs of 46Hz, a BIB will have a line length of 146" and the cabinet will end up ~ 73" in height. What happens if it is made 64" tall (line length 128")? Assumption is that cabinet volume will remain same (that means a wider and deeper cabinet, but shorter).
This may have been already covered in this giant thread, but a quick question - if a BIB is shortened in length (due to WAF), what is the likely impact? For example, for a driver with a Fs of 46Hz, a BIB will have a line length of 146" and the cabinet will end up ~ 73" in height. What happens if it is made 64" tall (line length 128")? Assumption is that cabinet volume will remain same (that means a wider and deeper cabinet, but shorter).
It will not go as low. That's about it. Personally, if it's standing upright, I would take it as high as you can. It doesn't take any extra floorspace and extended range never hurt anyone.
Not quite! Further from the ceiling, the quicker it unloads, driver goes 'clank' off the pole piece faster than anyone can hit the 'kill' switch since these are normally tuned below Fs. 🙁
+1 I keep saying this, but sadly, few do it, presumably because of increasing size, but I posted [somewhere] that just adding a secondary 'top hat' to get it near/at the ceiling further loads the driver against over excursion, yet none have tried it AFAIK.
GM
GM,
I didn't do the bolt on top hat, but per your recommendation I extended mine up to 8ft tall ( with 9 ft ceilings). After all if you are starting with a 4x8 sheet of plywood, a 8 ft tall box is easier to make than one that is shorter. Less cuts!
And I love the way these speakers load the room. Not sure how to describe it, but I have never had speakers do that.
Thanks again
I didn't do the bolt on top hat, but per your recommendation I extended mine up to 8ft tall ( with 9 ft ceilings). After all if you are starting with a 4x8 sheet of plywood, a 8 ft tall box is easier to make than one that is shorter. Less cuts!
And I love the way these speakers load the room. Not sure how to describe it, but I have never had speakers do that.
Thanks again
That's a big reason why I modified the plans for my Fostex fe108ez BIB's years ago, to be inverted and fire towards the floor in or near room corners instead of the ceiling.. The smaller BIB's are just way too short to effectively load up firing for sure. I've also seen many using their BIB's along side equipment stands and such, well away from corner's, ceilings, walls etc.. Not what they were designed for, and probably better to built a different design imo.. It's like using a corner horn design well out from the corners or any boundary's etc..
Cool! Makes sense to me. FWIW, the BIBs I did way back when were designed using a different math routine specific to make the horn room height, then cut the top off at 'x' angle sloped front to back as required to allow it to be tilted into place, which de facto yielded a nice big summed [1pi] loaded 'vent' area on either side with a bit of lossy 'squish' loading at the top, 'killing two birds with one stone'.
'Effortless' is how I describe large, acoustically efficient systems. 😉
You're welcome!
GM
Yeah, I look at some of those and wonder if they have EQ to protect them or just never play them > ~1 watt. Then again, I've repeatedly been surprised at how much distortion folks like/will tolerate. I mean a quick listen to the world's #1 selling consumer speaker systems 'tells the tale'.
I've only auditioned one BIB floor loader [FE127 IIRC] and was pretty underwhelmed, ditto the builder, but then we perched them on the corners of a long, sturdy built, 'L' shaped corner workbench and sitting in the 'sweet spot' they really rocked for such a small 'limp wristed' driver.
Maybe if the drivers had been angled up to fire at ~ear height?
GM
So, what should the space between terminus and floor (or ceiling in inverted) be? In an inverted BIB it would be easy to just put it on some feet and leave say 0.5-1.5" all around the terminus. But then the mouth area would be reduced to possibly less than the designed terminus.
Another way: is there a factor to apply that relates the mouth area and distance to floor/ceiling? Some of us can not load into corners, so just a wall/floor or wall/ceiling load is possible.
Thanks!
Another way: is there a factor to apply that relates the mouth area and distance to floor/ceiling? Some of us can not load into corners, so just a wall/floor or wall/ceiling load is possible.
Thanks!
You want to make it more rear firing for floor loading. So extend the front and sides of your bib cab approx 10-12 or so inches past the terminus.. That's all I did with the fe108 plans.. I forget what the plan dims for it were, but I made the front and sides 60'', and the backside as per the proper length for that BIB. Also doing that brought the driver up to a better ear height than per the normal dims for a fe108 BIB cab.. I'll try and post a pic to an inverted cab Terry Cain did, if it doesn't post just search Terry Cain BIB in images, and you'll see one that's made inverted with fancy side work on them that do not extend all the way to the floor like mine etc..
There is probably a proper math formula to calculate going inverted, I just winged mine at the time and played with a bit of stuffing etc.. You'll see in the pic of TC's BIB, that you can just leave your rear panel length the same as your particular plans say for your chosen driver, and then extend the sides and front lengths to allow for down firing etc.. My cabs had the side and front panels all the way to the floor like you'd see in almost any floor stander out there, the only difference was the back panel was left to fe108 BIB spec etc.. So the ones I made were more like a rear firing horn, although the rear exit cavity was not calculated mathematically in any way.. TC's is I'm sure, and most likely sound better than mine did.
BIB1-1.jpg Photo by muaddibb | Photobucket
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Late edit to my last post: The cab pic I posted of TC's BIB is his take for the fe108 in a BIB.. I was going to scroll cut the sides of my cabs like he did to experiment, but never got around to it.. I haven't used my BIB's now for quite sometime due to moving, and the arrangement I need to use now cannot be near or in room corners etc.. I'd like to offer thanks to the late Terry Cain, for it was that pic that inspired me to make my cabs inverted at the time. Also it made much more sense when you see how short the BIB's for smaller drivers are, as you're basically just dumping the sound half way up a wall or room, rather than closer to a ceiling or floor etc. Driver height can also be an issue as well with the smaller BIB's.
Yes, that's one way, the other is to calculate the terminus end correction [Ec] to find AFAIK the theoretical point where floor/ceiling loading begins in earnest, so any closer theoretically puts it in compression mode and up to the user to find what performs best overall in their app beyond this point.
Ec = Rp*0.613
where:
Rp = pipe/terminus radius
Example:
terminus is 15" x 10.6":
Ec = 0.613*[15*10.6/pi]^0.5 = 4.36"
Not having any useful test gear beyond various pairs of ears at the time, it would be nice to have some actual measurements to lend some [in]validation [hint, hint 😉], so that it can be fine tuned if need be.
GM