Ideal qts to be .5 I read, can't remember where.
doesn't make much sense to me. Horns are to like low qts .
doesn't make much sense to me. Horns are to like low qts .
Quick newbie question - if i have a driver fs 53, vas 37.02 & qts .25 the calc gives me a height of 166cm.... ideally I would like a height of approx 210cm to use the ceiling more... now I'm probably getting confused, but do I just drop the fs value in the calc to get it taller? Or is there more adjustments I have to make?
Cheers.... Tony
Cheers.... Tony
Tony,
What I did on GM's suggestion was to extend the four sides to the length I needed and then put the inner baffle at the height calculated by the bib calculator. I have an 8ft tall box with the inner baffle at the location for 50hz. Hope that makes since.
What I did on GM's suggestion was to extend the four sides to the length I needed and then put the inner baffle at the height calculated by the bib calculator. I have an 8ft tall box with the inner baffle at the location for 50hz. Hope that makes since.
Ah ok, so use the calc figures for driver height, internal baffle placement and WxD, but just increase the height?! Thanks!
Correct; here's the SS math/example: http://www.diyaudio.com/forums/full...se-fostex-craft-handbooks-59.html#post1191596
GM
Yeah, when extending these by changing Fs one needs to adjust height based on desired zdriver offset to keep it at the desired L*0.217 or 0.42 and then use a top hat if still too far away.
GM
Yes, I made my top hat by extending my four sides. That was a cleaner build for me and less work.
I have 8 foot tall bib's with 9 foot ceilings and that loads the room very well.
I have 8 foot tall bib's with 9 foot ceilings and that loads the room very well.
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The inverted BIB looks interesting, what kind of dimensions would I be looking at and how does it sim?
Hi all
I want to build a BIB with Fostex FE208EΣ and FT17H, my old house has the ceiling at about 3.70m, so I must build an inverted BIB.
BIB calculator v1 gives Zdriver=34.783"≈88.35cm, BIB calculator v2 gives the same Zdriver=88.35cm, nevertheless it also gives a corrected value of CorrectedZdriver=82.77cm.
From where came from the corrected value? Is it optimized in some form?
My second doubt is about the optimum Zdriver=0.217*L vs Zdriver=0.416*L, with the former it is easier to invert the BIB; with the later not so much, the driver should be at about 180cm from the floor, too much.
Thanks in advance.
I want to build a BIB with Fostex FE208EΣ and FT17H, my old house has the ceiling at about 3.70m, so I must build an inverted BIB.
BIB calculator v1 gives Zdriver=34.783"≈88.35cm, BIB calculator v2 gives the same Zdriver=88.35cm, nevertheless it also gives a corrected value of CorrectedZdriver=82.77cm.
From where came from the corrected value? Is it optimized in some form?
My second doubt is about the optimum Zdriver=0.217*L vs Zdriver=0.416*L, with the former it is easier to invert the BIB; with the later not so much, the driver should be at about 180cm from the floor, too much.
Thanks in advance.
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I ran the Alpair 7P (forgot to mention driver in original post) through the v2 BIB calculator and got this:
Line Length 80.15
Zdriver 17.39
Sm – Terminus Area (sq. in.) 83.18
Wood thickness 0.71
Baffle thickness 0.71
Does anything change if I wanted to create an inverted BIB? The 40 inch height wouldn't be well loaded by the ceiling, so I assume inverting it is the way to go.
Good question, I don't have any of this loaded, so can't see them and don't remember there being any revisions to my design routine.
IIRC, L*0.217 is from the Japanese book, though is correct enough for the 5th harmonic, ditto L*0.416 for 2/5ths, which provides a bit smoother response [less damping required], but a bit lower output as the trade-off. You can put it at the 3rd harmonic also, L*0.349.
Regardless, pipe horns are nothing if not flexible, so adjust the BIB to suit whatever driver location, listening height by changing the [Fs] spec as required, though of course if a specific tuning is required, such as to [Fs], then you may have to get creative to make it all work out.
BTW, with such a low Qts driver, if you plan on using passive EQ to flatten it out over a wide BW, then ideally the cab needs to be designed with this higher Qts'.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
GM
So essentially there isn't a generally optimal Zdriver location when inverted? Also if anyone has the time to all my Alpair 7PeN it would be much appreciated. Thinking about an inverted BIB.
Do BIBs need a larger room to perform well? My listening room will be my bedroom, I can place them against the wall and 3 feet from the corner, and I would be about 1-3 meters away from the speakers.
I'm reading the thread, currently on page 103, but it's hard to find much on inverted BIBs.
Do BIBs need a larger room to perform well? My listening room will be my bedroom, I can place them against the wall and 3 feet from the corner, and I would be about 1-3 meters away from the speakers.
I'm reading the thread, currently on page 103, but it's hard to find much on inverted BIBs.
None comes to mind ATM and haven't built one per se, just a variant with a restricted vent [Av = Sd], but some folks have and reported back, so searching the forum should turn some up.
Well, you could build it unfolded and add a 'top hat' extension per some earlier posts to get it close enough to the ceiling.
GM
It would be more aesthetically pleasing if it was inverted, that's one reason I'm thinking BIB. That, and the reports of how good the bass is with this enclosure.
Just to make sure I understand this right, an inverted BIB is built the same way as a normal bib, just flipped upside down. I'd make a stand for it, or legs, and was debating between how high off the ground it should sit, 4 inches, 6, etc..
I will try to search the forum for any iBiB posts.
Just to make sure I understand this right, an inverted BIB is built the same way as a normal bib, just flipped upside down. I'd make a stand for it, or legs, and was debating between how high off the ground it should sit, 4 inches, 6, etc..
I will try to search the forum for any iBiB posts.
Inverted or not, there's several options at its odd harmonics.
Not really, if anything it's theoretically better in smaller rooms where there's normally more room gain.
That's what the thread and forum search features are for. 😉 Ditto Google.
GM
Thank you. I will experiment with different heights from the floor to find out which works best. I read somewhere someone had it 1 inch off the floor, so I'll start there.
Thanks for all the help.
Thanks for all the help.
Please forgive my ignorance, I am a newbie on this, my first suspicion was that the correction is due to non-zero internal wood thickness, anyway I will trust in your calculations.
Your wisdom never cease to amaze me, thanks a lot!
Understood, I will take 0.217*L, and now I know why...
Bring these drivers to town will cost me an arm and a leg, so I think to tune with the Fs value would be a right choice, what is your opinion regarding the low Xmax?
Interesting, I didn't know about such malabars, indeed I plan using passive EQ, but without series resistance fortunately.
Thanks again.
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You're welcome!
FWIW: http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-110.html#post4903502
GM
You're welcome!
Could be, been so long since I've had Excel loaded and memory is mostly past tense nowadays. Regardless, to double check it, here's the example folks used to calculate it back when there was just a drawing to look at:
Fs = 70 Hz
Vas = 0.29 ft^3
Qts = 0.445
Vb = 20*Vas*Qts^1.25
L = 13464.54/2/70 = 96.175"
folded height = 96.175"/2 = 48.088"
Vb = 20*0.29*0.445^1.25 = 2.10804 ft^3
Sm = 2.10804*1728/48.088 = 75.751"^2
depth = SQRT((75.751*SQRT(2)) = 10.35"
width = 75.751/10.35 = 7.319"
zdriver = 96.175*0.217 = 20.87"
a-b-c = 10.35/2 = 5.175"
If you're going to drive it with a high output impedance tube amp [high series resistance], then tuning to multiples of [Fs] is desirable, though seems to me that there's been some super low Qts, low Xmax drivers tuned to Fs and still performed well, but personally wouldn't consider it unless corner loaded and these may have been as I imagine I would have cautioned them too.
Hmm, what passive EQ can you use that doesn't include some series resistance?
GM
You make it seems very easy, a detailed calculation is all that one wants, thanks again.
So far you did read my mind, twice! 😀
Indeed I will use a high output impedance (in the order of 1Ω) valve amplifier.
OK, understood.
If amplifier output impedance do not count as passive EQ series resistance, here Mr. Nelson Pass did some calculations for a start:
6moons audio reviews: First Watt - An Introduction by Nelson Pass
This is good for me because I have just an old scope and a couple of multimeters...
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