Without any of my info/software available, about all I can say is that a vented pipe horn [ML-BIB or small notched iBIB] needs the driver down from the closed end 50-56% to minimize the amount of stuffing required to smooth it out and if the terminus cutouts sum to large enough to mimic a BIB, then around 42%, so what percentage down is your original and 'mistake'?
GM
Compression chamber [sealed] to create a FLH or low pass filter chamber to make it an offset driver BLH?
Assuming the latter, I'm not aware of any, but IIRC Hornresp can sim it to see if it's worth the effort.
GM
IBiB Question
So I have finished my pair of BiBs. I have FE166E and FE166En drivers to use. Both have plenty of hours. I sized the cabinet for a Fs of 50Hz and a raised Qts to account for my SET amp. I have an extended top hat and left them 8 ft tall to try and work with my 9 ft ceilings. That said I just can't get them quite right. Maybe it is because the horn mouth is 8 ft in the air. Maybe it is because they are not close enough to the ceiling. I did add an internal baffle to add acoustic resistance and that helped to fill out the sound, but they are just not blending the horn mouth and the driver very well. Something is not quite right.
So I am thinking of going inverted BiB. So what is the rule of thumb for coupling to the floor. Assuming I do the bottom with radius cut outs like on a Metronome speaker what is the sizing on the cutouts. Is it open area = Sm?
I will try and post a pick of the current BiBs.
thanks,
So I have finished my pair of BiBs. I have FE166E and FE166En drivers to use. Both have plenty of hours. I sized the cabinet for a Fs of 50Hz and a raised Qts to account for my SET amp. I have an extended top hat and left them 8 ft tall to try and work with my 9 ft ceilings. That said I just can't get them quite right. Maybe it is because the horn mouth is 8 ft in the air. Maybe it is because they are not close enough to the ceiling. I did add an internal baffle to add acoustic resistance and that helped to fill out the sound, but they are just not blending the horn mouth and the driver very well. Something is not quite right.
So I am thinking of going inverted BiB. So what is the rule of thumb for coupling to the floor. Assuming I do the bottom with radius cut outs like on a Metronome speaker what is the sizing on the cutouts. Is it open area = Sm?
I will try and post a pick of the current BiBs.
thanks,
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BiB with internal baffle
As I said these boxes were made to a Fs of 50Hz so the folded height is 68" plus I have 28" of unexpanding section on top to get to a total height of 96". I had added cross braces of 1"x1" going from side panel to side panel to add some stiffness. So I thought why not attach an internal baffle using the cross braces in the top section. The baffle is 24" long and the full width of the box and solid. It has air gaps on each end and the open area is almost Sd. Slightly bigger I believe. Because of how it is mounted, it is removable and I can adjust the angle and therefore the air gaps on each end.
I originally installed the internal baffle before I updated my amp. My amp now has bigger output transformers and it plays about an octave lower. I just did this mod within the last week so I need to play with the baffle angle again and try removing it. Currently the Bib's are offline.
sketch attached
As I said these boxes were made to a Fs of 50Hz so the folded height is 68" plus I have 28" of unexpanding section on top to get to a total height of 96". I had added cross braces of 1"x1" going from side panel to side panel to add some stiffness. So I thought why not attach an internal baffle using the cross braces in the top section. The baffle is 24" long and the full width of the box and solid. It has air gaps on each end and the open area is almost Sd. Slightly bigger I believe. Because of how it is mounted, it is removable and I can adjust the angle and therefore the air gaps on each end.
I originally installed the internal baffle before I updated my amp. My amp now has bigger output transformers and it plays about an octave lower. I just did this mod within the last week so I need to play with the baffle angle again and try removing it. Currently the Bib's are offline.
sketch attached
Attachments
Hmm, we're in 'uncharted territory' as I've only simmed this type in Hornresp, which has no ceiling option and it looked really good overall at various driver/terminus delays, so seemed a reasonable option for really high ceiling apps; whereas mine were laid out to either have the driver at the floor, vent at the ceiling, which created a phantom image part way up the wall and not meant for >120 Hz reproduction and the folded ones good up to a 500 Hz XO were driver at a vertical odd harmonic room mode along with the mids/HF horn and the vent in the bottom corner.
Right off the 'top of my head', try a bed pillow, rolled up blanket or similar wedged at an angle to create a well damped corner reflector with, without the baffle. Might experiment with different materials if it shows promise; otherwise fiddle with internal stuffing to limit HF out the terminus and lose some bass in the process by making it semi-aperiodic.
GM
Hope you continue to be a 'guinea pig' 😉 for the high ceiling option, but understand if you don't.
It's a function of swept effective 'baffle' [terminus] area and circumference and I have some math that works 'good enough' for most folks, but not available to me for awhile yet, so all I can say is to find it empirically like I use to before computers.
Someone [use to?] have a webpage with some testing/results he did WRT down-firing woofers that would speed things up a bit, but didn't find anything just now other the R-O-T for round vents of Hg [gap height] = Dv [vent diameter], though this is meant to be enough to not pre-load it as is normally desirable for a iBIB, not to mention will really jack it up off the floor.
GM
On the Frugalphile website there is a IBiB speaker with Karlson slot. It notes "open area = Sm". Since I don't remember these specifically mentioned in the BiB thread, I don't know if they have been made or if they did how they worked. So for an IBiB does open area = Sm?
As for my uncut uninverted Bibs, I will continue to tune them. I remember when I built my first BLH, a BK-16 kit from Madisound, and my first thought was "oh my God what have I done?". It sounded terrible and I was pretty deflated. After some tuning, they sound great. But it took time and patience. Now, the speakers completely disappear. They are very musical and dynamic. I listen to a lot of blues and they are great for that. They just sound right.
So I was hoping my Bib would be similar but bigger. They do play bigger and deeper, but the speakers do not disappear. I distinctly hear the individual drivers.
Thinking through individual things I have done to improve the Bibs, it does appear that increased Q is common. Be that from adding series resistance or longer runs of speaker wire. So that is why I added the baffle. Maybe mass loading it some. I will try the pillow option and continue to play with the baffle angle or remove it altogether.
So does increased stuffing above the driver lower the high pass filter for the terminus mouth? Will I get less high frequencies out the horn mouth?
thanks for you responses GM. I always learn something from your posts, but I have to read them several time slowly to understand.
As for my uncut uninverted Bibs, I will continue to tune them. I remember when I built my first BLH, a BK-16 kit from Madisound, and my first thought was "oh my God what have I done?". It sounded terrible and I was pretty deflated. After some tuning, they sound great. But it took time and patience. Now, the speakers completely disappear. They are very musical and dynamic. I listen to a lot of blues and they are great for that. They just sound right.
So I was hoping my Bib would be similar but bigger. They do play bigger and deeper, but the speakers do not disappear. I distinctly hear the individual drivers.
Thinking through individual things I have done to improve the Bibs, it does appear that increased Q is common. Be that from adding series resistance or longer runs of speaker wire. So that is why I added the baffle. Maybe mass loading it some. I will try the pillow option and continue to play with the baffle angle or remove it altogether.
So does increased stuffing above the driver lower the high pass filter for the terminus mouth? Will I get less high frequencies out the horn mouth?
thanks for you responses GM. I always learn something from your posts, but I have to read them several time slowly to understand.
You're welcome!
Near enough, all these different numbers mostly just mean how much stuffing may be required.
GM
Near enough, all these different numbers mostly just mean how much stuffing may be required.
GM
You're welcome!
Yeah, I can be a tough read for the less educated and have the same problem when I go to certain sites such as DIY antenna design, which has even more abbreviations, etc., and far more technical than anything in DIY speakers.
Yes, the end of a TL/horn is a terminus/mouth and its area is often referred to as 'Sm' or 'Am' and some others over the decades that I forget now.
Whether it's the right amount of total cutout area really depends on how it performs, so ideally needs to be found empirically by trying different gap heights, then once found, calculate the perimeter area to find the total amount to be cut out. Of course if you do the cutouts, then this will shorten the 'tophat' length, so will alter it a bit, though down low the room dominates, so seriously doubt that any difference will be noticeable at the LP except less/no mids, HF due to firing into thick carpet, area rug or similar.
No way a simple pipe horn is going to sound like a mid-bass BLH until both are stuffed to a fare-thee-well, though the pipe horn should theoretically perform better overall due to its higher gain over a wider BW, but this assumes corner loading, so rolls off earlier as it's moved away from it and arguably will be harder to dial in than the BLH.
More damping in the top half of the pipe covers a wider BW, so damping unwanted mids/HF from escaping the cab is done at the terminus/vent unless you want to damp down some of its [mid] bass too and reflections back through the driver is done behind/around it.
WRT 'disappearing'; speakers need to be tonally balanced, so not sure it's possible with a BIB's long time delay unless you can either damp down its upper mass corner [2*Fs/effective Qts] or lower it with some series resistance, which the point of diminishing returns can be found empirically with a cheap 25 ohm pot, then replacing it with a fixed grid of small, high quality resistors.
Some of the really large cabs I've built or just designed employed a damped top and a 'hanging blanket' of fiberglass insulation draped diagonally across the cab to damp all sides unilaterally except the bottom where the vent is, so somewhere in this thread I suggested making a triangular shaped 'blanket' to drape across/down the terminus part [all the?] way down to the bottom, which worked really well for at least one member, so search 'loninappleton' for more details.
Adding a rounded over supra baffle often helps as does a 'tweeter' damping ring around the driver.
GM
Thanks again, GM! Playing with the stuffing is actually half the fun. 🙂 The first time I did it with my young son we played test tones, then played with the stuffing and compared and just played til we liked it, My girlfriend is happy to and looking forward to the process too ... cheers! 😀
I'd like to echo ToddD's comment above: it's always a pleasure and an education to read GM's posts on here ... acronyms, abbreviations an' all!
Thanks! Glad I can sometimes 'peel back the veil of ignorance' [as Tom Danley sometimes says] in the hope that folks can make an informed decision in a world of marketing obfuscation, hyperbole, promoting self interest, etc., not to mention the outright lying of the 'bottom feeding' 'ne'er-do-wells'.
GM
GM
+1. 🙂
Way too much drivel in audio at the moment (and has been since probably the '70s), so it's people like GM who are invaluable.
959,000+ views on this thread to date, so we're approaching the round million. 😀