GM said:
I'm really impressed by this formula (as well as with corresponding Lr of 0.217) - it fits to every speaker I've played with (from Qts=0.16 to Qts=2.2 & from 3" to 18" speakers) and the response given is always optimal.
This is really one of the best contemporary founding for DIY people - BIB design become easier and more predictable than f.ex. ported or even closed box and this whatever speaker you use
BTW, I've found another nice speaker position for your equation: at Lr=0.117: "horn" action is more present and, important, sounds very good (less ripples, more mid impact and impedance peak is also better aligned).
I'd like to ask one question regarding folding: why the interior panel stops exactly at a=b=c=d/2 (referring to http://www.zillaspeak.com/bib-howtobuild.asp): the expansion of the line is not regular in such case. I've seen TC used is in his original BIB but I haven't found any explanation for it. Is it for simplicity or is it based on some other reason?
Greets!
I believe T.C. just copied a Japanese design and you're right, the expansion isn't linear with his BIB, but I drew it out to scale since the math is 'Greek' to me and found that if the width:depth ratio was 2^0.5 (~1:1.4142) that it was 'close enough', so what I recommend, but anyone with AutoCad or similar and knows how to do this with it can double check me: http://www.users.bigpond.net.au/ggoodacre/centauri/diy/hornfold.html
Regardless, there's been many built using a variety of ratios including these two and all are claimed to sound good, so as always YMMV.
GM
I believe T.C. just copied a Japanese design and you're right, the expansion isn't linear with his BIB, but I drew it out to scale since the math is 'Greek' to me and found that if the width:depth ratio was 2^0.5 (~1:1.4142) that it was 'close enough', so what I recommend, but anyone with AutoCad or similar and knows how to do this with it can double check me: http://www.users.bigpond.net.au/ggoodacre/centauri/diy/hornfold.html
Regardless, there's been many built using a variety of ratios including these two and all are claimed to sound good, so as always YMMV.
GM
dmason said:I have also been playing with USB digital, a Scott Nixon CHIBI UFO, this with a JFET buffer, which made all the sense in the world, especially with our beloved but tweaky flea amps. Color me converted.
Hard disk streamed audio is to CD player, what SET is to bipolar transistor, AFAIAC...
Off topic again but thought I would report - finished my USB DAC, would be very similar to the Scott Nixon but bigger power supply with dedicated regulation for each chip/stage.
To my great surprise I cannot tell the difference between it and my Philips CD880 with super clock/NONOS mod/AD844 i/v stage. Clearly the HDD/PC based source has a lot of potential - the DAC chip in my CD880 (TDA1541A S1) is reckoned to be way better than the TDA1543 in the USB DAC. More listening needed.
Oh, and my FE208EZ Sigma/T90A super tweets have arrived. The immediate question comes to mind - how to mount the T90A? At the moment all I can think of is clamped to the side of the box just above the supra baffle, or with a notch taken out of the supra baffle. Suggestions?
Chris
I just simulated this driver using MJK`s TL offset driver sheet. Peaks at 40Hz and hangs at 50-60Hz. Is the Qts too low for BIB?
By the way, what is the current gold standard for BIB simulation? I didn`t follow the thread.
http://www.ciare.com/pdf/catalogo/CM165NDA.PDF
Oliver
By the way, what is the current gold standard for BIB simulation? I didn`t follow the thread.
http://www.ciare.com/pdf/catalogo/CM165NDA.PDF
Oliver
el`Ol said:
Greets!
Not really sure what defines the 'gold standard', but TC's original line length, driver location is a reasonable compromise for a wide range of Fs drivers.
Yeah, you'll need some EQ on this driver and place it in the corners if you want it to go low with any semblance of tonal balance. Anyway, using the formulas here: http://www.diyaudio.com/forums/showthread.php?postid=1229324#post1229324
L = 89.76"
Sm = 22.93"^2 (4.03" W x 5.69" D)
a-b-c = 2.85"
zdriver = 19.47"
So looks like it's not even big enough to mount the driver........
Adding 4 ohms series R, should flatten it out considerably:
L = 89.76"
Sm = 62.79"^2 (6.66" W x 9.43" D)
a-b-c = 4.71"
zdriver = 19.47"
Still, it 'wants' 8 ohms series R in a longer, bigger corner loaded pipe, but bottom line, my SWAG is its low Vas will probably make it a marginal performer in a BIB regardless of alignment.
GM
GM said:
Thanks. yes, entirely agree about closer the better for tweeters. But the mechanics of hole mounting througth baffle could be difficult - these tweets are very long and heavy.
A quick scale drawing with FE208 dia. 230mm, cab external width 260mm, shows I can achieve the tweet within 30mm from the 208 if I clamp it to tha cab with a notch in the supr baffle located about "10 o'clock". I think 30mm distance will be quite acceptable.
Moth BIB ?
I just purchased 2 New stock Moth Cicada drivers for my next project:
VAS: 58 ltr.
QTS: 0,67
MMS: 11 gr
FS: 50 hz
Diameter is 16cm (SD = 201 cm2)
This is a fairly high QTS lowther look-alike. Efficiency is said to be 94 dB, but tests show 92...
Would this be a good candidate for BIB, Would enclosure have to be big?
Thanks.
Daniel
I just purchased 2 New stock Moth Cicada drivers for my next project:
VAS: 58 ltr.
QTS: 0,67
MMS: 11 gr
FS: 50 hz
Diameter is 16cm (SD = 201 cm2)
This is a fairly high QTS lowther look-alike. Efficiency is said to be 94 dB, but tests show 92...
Would this be a good candidate for BIB, Would enclosure have to be big?
Thanks.
Daniel
GM: Broad rules of thumb?
GM, seeing as you appear to be the "sim master" when it comes to these things (BiB's) can you provide any rough rules of thumb when it comes to tweaking dimensions and distances?
I mean, basically, you can play with 3 values, those being: line length, mouth area and position of the driver along the line.
Obviously there are tradeoffs as far as gain, response flatness, low end emphasis and tuning frequency.
Which parameters affect which attributes and how?
I'm looking at this from a point of view that if you were going to modify the design and you were happy to forgo a little bass for the sake of a smoother response, which tweaks to the dimensions and distances would you apply? Or if you wanted more bass boost but didn't mind if it was a touch lumpy then you can achieve that by modifying what?
Is it possible to apply broad rules of thumb at all?
GM, seeing as you appear to be the "sim master" when it comes to these things (BiB's) can you provide any rough rules of thumb when it comes to tweaking dimensions and distances?
I mean, basically, you can play with 3 values, those being: line length, mouth area and position of the driver along the line.
Obviously there are tradeoffs as far as gain, response flatness, low end emphasis and tuning frequency.
Which parameters affect which attributes and how?
I'm looking at this from a point of view that if you were going to modify the design and you were happy to forgo a little bass for the sake of a smoother response, which tweaks to the dimensions and distances would you apply? Or if you wanted more bass boost but didn't mind if it was a touch lumpy then you can achieve that by modifying what?
Is it possible to apply broad rules of thumb at all?
Re: Moth BIB ?
Greets!
'New', as in recently made with measured specs, or 'new' as in bought awhile back and never been used (NOS)? The reason I ask is that some measured units have a much higher Qts than the published specs (9.6 Qms/1.3 Qes/1.09 Qts), which would make for a humongous (~46.11 ft^3) BIB, not that your specs' ~24.832 ft^3 is svelte.
Anyway, your specs would work, not sure about the higher Qts ones though, I don't recall simming any this high.
GM
Daze said:
Greets!
'New', as in recently made with measured specs, or 'new' as in bought awhile back and never been used (NOS)? The reason I ask is that some measured units have a much higher Qts than the published specs (9.6 Qms/1.3 Qes/1.09 Qts), which would make for a humongous (~46.11 ft^3) BIB, not that your specs' ~24.832 ft^3 is svelte.
Anyway, your specs would work, not sure about the higher Qts ones though, I don't recall simming any this high.
GM
Re: GM: Broad rules of thumb?
Greets!
Not me, the more computer savvy young'ns have left me in the dust.
Anyway, 'L' affects Fp, Vb; 'Sm' both gain BW and Vb; 'zdriver' from max to least gain BW, which sets overall response smoothness. As you can see, Vb is the biggie, so all else being equal, adjusting 'Sm' the F3 point just like a BR alignment. Locating 'zdriver' as close as practical to the throat yields the max gain BW, ergo the least at the mouth. Standard BIB 'zdriver' is 'L'*0.217, Scott's smoother sub BIB alignments are at 'L'*0.416. MJK has derived some based on pipe action for his 'Classic TL Alignments' pdf that may be of use and of course you can sim your own. Note that in my experience, max flat (smoothness) occurs somewhat lower than any of the published positions, moving towards the mouth with increasing aspect ratio, so the shorter the pipe for a given 'Sm', the lower the driver position and vice versa.
GM
DrewP said:
Greets!
Not me, the more computer savvy young'ns have left me in the dust.
Anyway, 'L' affects Fp, Vb; 'Sm' both gain BW and Vb; 'zdriver' from max to least gain BW, which sets overall response smoothness. As you can see, Vb is the biggie, so all else being equal, adjusting 'Sm' the F3 point just like a BR alignment. Locating 'zdriver' as close as practical to the throat yields the max gain BW, ergo the least at the mouth. Standard BIB 'zdriver' is 'L'*0.217, Scott's smoother sub BIB alignments are at 'L'*0.416. MJK has derived some based on pipe action for his 'Classic TL Alignments' pdf that may be of use and of course you can sim your own. Note that in my experience, max flat (smoothness) occurs somewhat lower than any of the published positions, moving towards the mouth with increasing aspect ratio, so the shorter the pipe for a given 'Sm', the lower the driver position and vice versa.
GM
Hi there !
I'm having a thought of using the BiB in combination with a front loaded horn attachted. (horn is a B.D. design Oris 150)
So basically I only want everything below 150Hz attentuated.
(BiB as backloaded basshorn, Oris 150 as frontloaded midhorn)
Driver would be the Hemp FR8C.
Now should I move the driver towards the closed end to reduce
it's effect in higher frequency's or is it the other way 'round ?
At what position should the driver be ?
Cheers,
Empee
I'm having a thought of using the BiB in combination with a front loaded horn attachted. (horn is a B.D. design Oris 150)
So basically I only want everything below 150Hz attentuated.
(BiB as backloaded basshorn, Oris 150 as frontloaded midhorn)
Driver would be the Hemp FR8C.
Now should I move the driver towards the closed end to reduce
it's effect in higher frequency's or is it the other way 'round ?
At what position should the driver be ?
Cheers,
Empee
Greets!
I believe you mean 'accentuated' (boosted), though in this case better to say attenuate (roll off) the BW above 150 Hz. Tough language, English, even for us natives, so a 'hats off' to all you folks that 'speak' it so well overall as a secondary language.
Anyway, moving the driver to the closed end as much as practical maximizes both the total gain and its BW, so as it's moved down the pipe the lows and their harmonics are increasingly rolled off, ergo you want it at the closed end and electrically roll off the unwanted BW for max efficiency or further down for a flatter, though lower efficiency response. FWIW Scott uses L*0.416 for his 'sub' BIBs.
That said, the BIBs as designed don't have enough Vb to support end loading without significant 'ripple', so I don't recommend doing it without simming/adjusting 'Sm' till it's reasonably smooth in the intended passband. Scott's location is a good trade-off between LF gain and smoothness on average, but I believe with simming you can get a better response overall to 150 Hz by moving the driver even further down.
GM
I believe you mean 'accentuated' (boosted), though in this case better to say attenuate (roll off) the BW above 150 Hz.
Tough language, English, even for us natives, so a 'hats off' to all you folks that 'speak' it so well overall as a secondary language.Anyway, moving the driver to the closed end as much as practical maximizes both the total gain and its BW, so as it's moved down the pipe the lows and their harmonics are increasingly rolled off, ergo you want it at the closed end and electrically roll off the unwanted BW for max efficiency or further down for a flatter, though lower efficiency response. FWIW Scott uses L*0.416 for his 'sub' BIBs.
That said, the BIBs as designed don't have enough Vb to support end loading without significant 'ripple', so I don't recommend doing it without simming/adjusting 'Sm' till it's reasonably smooth in the intended passband. Scott's location is a good trade-off between LF gain and smoothness on average, but I believe with simming you can get a better response overall to 150 Hz by moving the driver even further down.
GM
GM said:Greets!
I believe you mean 'accentuated' (boosted), though in this case better to say attenuate (roll off) the BW above 150 Hz.
Anyway, moving the driver to the closed end as much as practical maximizes both the total gain and its BW, so as it's moved down the pipe the lows and their harmonics are increasingly rolled off, ergo you want it at the closed end and electrically roll off the unwanted BW for max efficiency or further down for a flatter, though lower efficiency response. FWIW Scott uses L*0.416 for his 'sub' BIBs.
That said, the BIBs as designed don't have enough Vb to support end loading without significant 'ripple', so I don't recommend doing it without simming/adjusting 'Sm' till it's reasonably smooth in the intended passband. Scott's location is a good trade-off between LF gain and smoothness on average, but I believe with simming you can get a better response overall to 150 Hz by moving the driver even further down.
GM
I appreciate you both GM and Scott for this wonderful thread and all the help and design given.
In the past I was given by Scott box dimensions for a FE164 that I still have and wish to make a BIB with them.
Some post back Planet10 seemed concerned about the ripple saying that they would be audible under some circumstance. Could someone run a sim to see how much ripple this setup is going to show?
FE164 main parameters:
Fs 50 Hz
Qts 0.31
Qms 4.0
Qes 0.34
Vas 32.2 L
SPL 92 dB/W mt
New BIB Project
Hello All,
Just getting ready to build a new set of BIB's. These are set to be put in-wall for a simple home theatre application in a friends house. He does not want much, but loved the sound of the set I am currently using. I wanted to check with everyone and see what their feelings are on the dimensions I came up with. It looks like they will work decently.
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=297-462&CFID=1961992&CFTOKEN=34187854
This is the drive being considered. Can not find any reviews on it, so taking a leap. These are the dims I came up with:
Fs 63.000
Vas 0.2
Qts 0.380
Line Length 106.861
Folded Height 53.431
Vb 1.193
Sm 38.596
Depth 7.388
Width 5.224
zdriver 23.189
a-b-c 3.694
The drivers do have a small VAS, more like a 4" than a six, due to the cuttout for the mid/ribbon assembly.
so, If anyone has the time, I would greatly appreciate your feed back.
Hello All,
Just getting ready to build a new set of BIB's. These are set to be put in-wall for a simple home theatre application in a friends house. He does not want much, but loved the sound of the set I am currently using. I wanted to check with everyone and see what their feelings are on the dimensions I came up with. It looks like they will work decently.
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=297-462&CFID=1961992&CFTOKEN=34187854
This is the drive being considered. Can not find any reviews on it, so taking a leap. These are the dims I came up with:
Fs 63.000
Vas 0.2
Qts 0.380
Line Length 106.861
Folded Height 53.431
Vb 1.193
Sm 38.596
Depth 7.388
Width 5.224
zdriver 23.189
a-b-c 3.694
The drivers do have a small VAS, more like a 4" than a six, due to the cuttout for the mid/ribbon assembly.
so, If anyone has the time, I would greatly appreciate your feed back.