Makes the box stiffer, more massive, both a good thing, though there's much more to be gained by doing the sides of a BLH horn instead and just use a supra baffle for the driver.
As previously noted, thick baffles, wide range drivers require the rear of the baffle to be chamfered out at least 45 deg to allow the entire open area of the rear of the driver to be exposed/'breathe'.
???? Tweeter in the back?
GM
As previously noted, thick baffles, wide range drivers require the rear of the baffle to be chamfered out at least 45 deg to allow the entire open area of the rear of the driver to be exposed/'breathe'.
???? Tweeter in the back?
GM
Hi GM, thank you very much for your kind help, and a lot of patience. 🙂
OK, understood.
My woodwork skills does not allow me to make a circular cut chamfered at 45º, what about the idea on post#5631, i.e. the supra-baffle with the right diameter and the front, say 4cm bigger?
Well, it is a little embarrassing, but I have no instruments to put the tweeter in phase, so this idea did sound good to me
http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-246.html#post1150391
http://www.diyaudio.com/forums/full-range/233591-tweeter-top.html#post3444073
But you are the master, so I will follow your recommendation.
OK, understood.
My woodwork skills does not allow me to make a circular cut chamfered at 45º, what about the idea on post#5631, i.e. the supra-baffle with the right diameter and the front, say 4cm bigger?
Well, it is a little embarrassing, but I have no instruments to put the tweeter in phase, so this idea did sound good to me
http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-246.html#post1150391
http://www.diyaudio.com/forums/full-range/233591-tweeter-top.html#post3444073
But you are the master, so I will follow your recommendation.
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I always double up the front baffle. It strengthens the front and places the magnet away from the inner baffle. I've also mounted a tweeter on the back of my BIBs with good results but you must pull the speakers away from the corners or it doesn't work at all.
Thank you very much!
Seems to me that tweeter placement is very hard to do well in a BIB, two contradicting conditions...
I could not read the whole thread, but I think have read that a floor loaded BIB could work near the wall, i.e. no need corner placement.
No contradicting conditions for that. Godzilla chose the back of the enclosure due to his specific needs.
BiBs ideal location are corners and/or as close to the walls as possible, with a performance hit in the low bass when not in a corner. Floor loaded BiBs have the same requirements.
We are talking of exciting the oscillation modes of the room, and the best place to do that in rectangular rooms are the corners followed by the walls.
Of my two BiBs one of them is corner loaded while the other one is only wall loaded. The difference in low bass response is noticeable as is the cone displacement magnitude for the drivers.
Here are two photos of my setup taken from the listening spot. General view and ceiling/corner emphasis. Please forgive the mess.
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![IMG_20170607_115211805[1].jpg](/community/data/attachments/574/574117-a36a98c6ced7b857e84d78f4288fab39.jpg?hash=o2qYxs7XuF)
![IMG_20170607_115203327[1].jpg](/community/data/attachments/574/574107-f25ea38731d4e603861044daba2322a1.jpg?hash=8l6jhzHU5g)
It wouldn't be my first choice since the flat 'step' creates a ~infinite set of reflections over a narrow range, so if done this way, best to line it with a fairly dense material. That said, I've never experimented, so may not be acoustically strong enough to audibly affect performance, but 'God' is in the details, so might as well make sure since it's cheap, easy to do.
FWIW, I didn't have a router during my speaker building 'career', so chamfered the driver holes with a really coarse half round bastard rasp. Rips up the [ply] wood really good, making an uneven back cut with a lot of reflective surfaces to randomly diffuse them, the theoretical ideal AFAIK. A good way to vent any frustrations too! 😉
One way to physically align a tweeter is to offset to the outside of the [mids] woofer relative to the listener by however much it takes depending on the speaker's toe-in [if any] and how wide the listening position is.
No, just an advanced DIYer; I've been around audio, speaker design masters [among others] and I assure you I'm not one.
GM
Tweeter or super tweeter with such a wide air gap to the front? The latter is fine for top end 'air' since it has a very high XO point, but my limited experience with much lower XO points sounded anywhere from 'confusing' to downright 'two toned' as the XO was shifted downward.
GM
The latter is by far the main reason for wall/corner loading, especially smaller drivers with a low Xmax and doubly so when using Markaudio or similar that have virtually no audible distortion to indicate the driver is very close to hitting its mechanical limit [Xmech].
GM
He also said that you must pull the speakers away from the corners or it (tweeter arrangement) doesn't work at all.
Here is the contradiction, if you put the BIBs in the ideal location, tweeters on the back wont work.
Beautiful speakers!
Mess??? What mess?
Obviously you do not know a high entropy environment, aka my house... 😛😀
OK, understood, and thanks again.
That is not my preferred tool, but the new problem is that driver support screws will left with its end on the air.
I do not like any randomness, on the contrary I like the symmetry, so what about an eight-pointed star, with screws at each end? Should be this a good average?
Anyway, all for the sound...
On the last weekend I did some advance with Arta Software, my webcam microphone is not the great thing but to see some minimum in the frequency response (tweeter out of phase for tuning) I think it will be enough.
In addition to be one of our superhero of the forum, you are modest!
No words...
popilin,
Please refer to the attached - an example of a chamfer I did keeping some material for the screws to dig in. This was for an Mark Audio Alpair 10 driver.
Which driver are you planning to use?
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Hi zman, you save me for another drawing, that is exactly the idea, thanks!
I am planning to use the Fostex FE208EΣ with the FT17H, cutting at about 10KHz with a capacitor, 0.47μF or so, not calculated yet.
I have measured specs for my Alpair 7P, and the output impedance of my amp camp amp is 2.67 ohms. Using a website I found earlier in the thread this means the effective QTS is 0.904. When using the BIB calculator, should I take this into account?
Also, do the BIB calculators use the FS of the driver to set line length, or does the calculator use .707*FS to calculate line length?
One concern I have is that my driver, as it burns in, FS and QTS will lower. Should I stick with the measured numbers as they are, or should I use slightly lower numbers for FS and QTS. Guesstimate them, so to speak.
Thanks!
Also, do the BIB calculators use the FS of the driver to set line length, or does the calculator use .707*FS to calculate line length?
One concern I have is that my driver, as it burns in, FS and QTS will lower. Should I stick with the measured numbers as they are, or should I use slightly lower numbers for FS and QTS. Guesstimate them, so to speak.
Thanks!
Hmm, that's way higher than published + 2.67 ohms [0.688]; I thought MA drivers were close enough to use published to design by same as the early CSS models I have. For sure, if they break in like traditional drivers they won't drop nearly enough, so I guess either wait till broken in and remeasure or just use 0.904 and worse case it will be too big, so may need a bit more damping.
If you want to guess, FWIW I've been lucky using the mean of the choices [0.688*0.904]^0.5 = 0.789.
An example with all the math shows a full octave below Fs, so Fs/2: http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-113.html#post5085538
GM
If you want to guess, FWIW I've been lucky using the mean of the choices [0.688*0.904]^0.5 = 0.789.
An example with all the math shows a full octave below Fs, so Fs/2: http://www.diyaudio.com/forums/full...e-fostex-craft-handbooks-113.html#post5085538
GM
These were measured by Planet 10, they are enabled drivers. If I went with .789 as the QTS what would I potentially give up/gain? Also, can I tune to .707*FS? Or maybe in between, like .808? The drivers have a 4mm xmax, and I do not want to overwork them.
Again, I've zero experience with this particular pipe horn alignment or any experience with little drivers even in the alignment I used, but horns in general always have more passband 'ripple', LF roll-off than with a sufficiently large one, i.e. 'BIB' rules, so no gain, only losses, though whether anyone could hear the difference in room with one a bit smaller with such a high Fs driver? No clue.
Re tuning, you can tune it however you want, but below a driver's Fs the only control on it is the cab loading, hence the basic design is a full octave below Fs and with help from the room to further damp it, folks have proven that small, low Xmax drivers can put out considerable bass at < 1 W.
Excursion increases 4x/octave and this driver in half [2pi] space hits Xmax/1 W at ~83 Hz, so output drops ~12 dB/0.6 W/~41.5 Hz; that's a lot horn, room gain required to get just 1 W of output.
That said, another criteria is that there's only so much BW that can be horn loaded, so assuming a ~74 Hz Fs, 0.904 Qts', ~74*0.904/2 = ~33.45 Hz is the lower limit, then in theory the closer you tune to this, the better, but going in the wrong direction for you.
As you move tuning closer to Fs, then the horn must be proportionately 'fatter' since you still need the same net Vb as the longer one plus better room coupling to offset the shorter pathlength [make it more like a floor loaded BIB/MLhorn] or accept that it won't play as low before the driver hits Xmech [clank!] and passband 'ripple' is shifted higher up in frequency [these are basically two octave horns], which may require [much]more internal damping, further reducing [mid] bass output.
All things considered, I'm beginning to wonder if a BIB will work well in your app unless these will be played at background music levels. Only one way to know for sure though.
GM
Re tuning, you can tune it however you want, but below a driver's Fs the only control on it is the cab loading, hence the basic design is a full octave below Fs and with help from the room to further damp it, folks have proven that small, low Xmax drivers can put out considerable bass at < 1 W.
Excursion increases 4x/octave and this driver in half [2pi] space hits Xmax/1 W at ~83 Hz, so output drops ~12 dB/0.6 W/~41.5 Hz; that's a lot horn, room gain required to get just 1 W of output.
That said, another criteria is that there's only so much BW that can be horn loaded, so assuming a ~74 Hz Fs, 0.904 Qts', ~74*0.904/2 = ~33.45 Hz is the lower limit, then in theory the closer you tune to this, the better, but going in the wrong direction for you.
As you move tuning closer to Fs, then the horn must be proportionately 'fatter' since you still need the same net Vb as the longer one plus better room coupling to offset the shorter pathlength [make it more like a floor loaded BIB/MLhorn] or accept that it won't play as low before the driver hits Xmech [clank!] and passband 'ripple' is shifted higher up in frequency [these are basically two octave horns], which may require [much]more internal damping, further reducing [mid] bass output.
All things considered, I'm beginning to wonder if a BIB will work well in your app unless these will be played at background music levels. Only one way to know for sure though.
GM
It's down to a BIB or Pensil, and the Pensil is sounding like the safer build. I'll mount them on Open Baffles to burn them at first, and do some more research while they're burning in.
My listening room is small, and I usually will use them for music, at lower levels (75db max), and TV/HT, at similar SPL levels.
With these considerations, does that make the iBiB using the stock alpair 7p measurements something workable in my room. They will be placed up against the wall, 2 feet from corners.
I just really want to try a BIB (i listen mostly to folk, vocals, and old school R&B/soul music, some classic rock). If it fails, I can always try a different driver and move the alpair to a pencil.
With these considerations, does that make the iBiB using the stock alpair 7p measurements something workable in my room. They will be placed up against the wall, 2 feet from corners.
I just really want to try a BIB (i listen mostly to folk, vocals, and old school R&B/soul music, some classic rock). If it fails, I can always try a different driver and move the alpair to a pencil.