Re: Re: Re: Re: Re: Bofu Bib
Well, I don't know if it's a good idea or not, but I know if you use the calculator it's a ~24 ft^3 cab regardless of path-length (height), so you won't be wishing for more acoustic gain.
Shrinking it to ~12 ft^3 will require either floor loading or a large vent cutout. Ditto a ~6.8 ft^3 vented variant which is about the smallest BIB that will have probably enough acoustic gain to not need any BSC.
Anyway, the bottom two sims use a 3/4" baffle thickness vent in a blocked off terminus (Sm):
GM
planet10 said:
Well, I don't know if it's a good idea or not, but I know if you use the calculator it's a ~24 ft^3 cab regardless of path-length (height), so you won't be wishing for more acoustic gain.
Shrinking it to ~12 ft^3 will require either floor loading or a large vent cutout. Ditto a ~6.8 ft^3 vented variant which is about the smallest BIB that will have probably enough acoustic gain to not need any BSC.Anyway, the bottom two sims use a 3/4" baffle thickness vent in a blocked off terminus (Sm):
GM
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bought a pair of the BOFU drivers 2 weeks ago to try in the EPI 200 speakers i have. while the outer dimension of the BOFU fits the cabinet, the inner dimension was too large! love to try these speakers with the 12" Polk PRs in the cabinets. oh well...
so, it will be necessary to build some new cabinets. is there a way to get the BiB results in a 48" tall box and maintain the equivalent 12' line? of course this would mean a "deeper" box. i'd rather not have a 6' box in the room. 4' is ok though.
so, it will be necessary to build some new cabinets. is there a way to get the BiB results in a 48" tall box and maintain the equivalent 12' line? of course this would mean a "deeper" box. i'd rather not have a 6' box in the room. 4' is ok though.
Why not just build the Nelson Pass BOFU TL? It is 38" tall, 10" wide and 20" deep and provides good bass extension. http://homepage.mac.com/tlinespeakers/FAL/downloads/Pass-BOFU-TL-map-300408.pdf
i saw this one and was interested. however, i thought of making the length 48" instead of the 38" and wondered how this might sound? the pipe length would wind up being ~12' and would give about the same bass extension as the BiB with only a 4' cabinet height.
any thoughts?
It would give you quite a bit less bass gain I'd think, but I don't find the bass lacking with the "normal" version of Nelson's design (though I lined the first section and added some build features) so your version should have that little bit extra that truly makes a subwoofer optional in many rooms.
now wait a minute. the BiB has a 12' line. this would also be about 12'. how is this different?
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The many meanings of the word TL can get confusing, sorry. In this case any QW resonantor with terminus equal to or less than the start
A BIB is usually classified as a tapped horn. The expending line means that the line has to be longer to meet the Fs of the driver.
If a line has constant cross-section, then L = WL(Fs)/4 (ignoring end correction which makes it shorter).
If the line xSection gets smaller towards the terminus, then L < WL(Fs)/4
If the line xSection gets larger towards the terminus, then L > WL(Fs)/4
How much in the last 2 cases depends on the taper ratio. Just looking at the subtables in the MJK alignment tables will quickly give you an idea.
dave
A BIB is usually classified as a tapped horn. The expending line means that the line has to be longer to meet the Fs of the driver.
If a line has constant cross-section, then L = WL(Fs)/4 (ignoring end correction which makes it shorter).
If the line xSection gets smaller towards the terminus, then L < WL(Fs)/4
If the line xSection gets larger towards the terminus, then L > WL(Fs)/4
How much in the last 2 cases depends on the taper ratio. Just looking at the subtables in the MJK alignment tables will quickly give you an idea.
dave
didn't realize the BiB was considered a TH/taperflex. must have missed this point. i thought there was some discussion on "just how/why the BiB worked".
ok, i'll bite on this one. what about a mod to the pass design? swap ends.
invert the box. put the terminus where the woofer is and put the woofer where the terminus is, properly sized, of course.
ok, i'll bite on this one. what about a mod to the pass design? swap ends.
invert the box. put the terminus where the woofer is and put the woofer where the terminus is, properly sized, of course.
BOFU BiB update
well, i bought a pair of the B20 speakers december and was all set to have a cabinet maker make a set for me. gave him the plans and never heard back.
so it seemed the project might stall a while. it did until i found someone on the diyAudio was giving away a pair of the Hedlund cabs for free! all i had to do was drive to get them.
the B20s now rest in these cabs and after a few mods sound really good! next i'll add the piezo tweeter mod.
so the BiB might just have to wait a while now.
and it seems to me that there is a similarity in the rough shape of the TL between the BiB and the Hedlund. of course the Hedlund opens into the room from a "proper" scoop.
no doubt the BiB is far simpler to make than the Hedlund. the BiB line is longer than the Hedlund and is reported to have a slightly lower response.
but these seem to me to be almost the same thing, bar the aesthetics.
well, i bought a pair of the B20 speakers december and was all set to have a cabinet maker make a set for me. gave him the plans and never heard back.
so it seemed the project might stall a while. it did until i found someone on the diyAudio was giving away a pair of the Hedlund cabs for free! all i had to do was drive to get them.
the B20s now rest in these cabs and after a few mods sound really good! next i'll add the piezo tweeter mod.
so the BiB might just have to wait a while now.
and it seems to me that there is a similarity in the rough shape of the TL between the BiB and the Hedlund. of course the Hedlund opens into the room from a "proper" scoop.
no doubt the BiB is far simpler to make than the Hedlund. the BiB line is longer than the Hedlund and is reported to have a slightly lower response.
but these seem to me to be almost the same thing, bar the aesthetics.
they are very rough. they were prototypes and unfinished MDF.
nothing snazzy like some are.
Interesting!
Hmm, the Hedlunds I've seen were all designed for Lowthers which would require a much smaller filter chamber, so the horn/driver acoustic XO would be much too high, i.e. have too much overlapping BW between horn HF output and driver lower mids = broadband peak in this BW composed of comb filtered response which typically makes this transition sound 'muddy'. Then again, since the B20 isn't exactly a high resolution reproducer, it may not be all that noticeable unless you're listening for it.
Anyway, these two designs are an apples n' oranges comparison since the Hedlund has a filter chamber and a compression expansion horn while the BIB has neither.
If the Hedlund was designed for the B20 though, then it should in theory be audibly superior SQ wise to the BIB.
GM
the B20 is offset from the front of the cabinet by 2.25" in order to provide ample clearance for the driver. it is stuffed with polyfill, probably about .25#of it. and i used the speaker gasket seal around the driver. this probably negates the filter chamber effect.
originally the offset was 1.5" and the sound resulted in "husky" sounding voices with poor bass. also the "original" damping material (eggshell foam) and original wiring were replaced.
while the headlund has a slick curved area at the top, what i meant by the similarity in the line between them and the BiB is that the headlund looks like a modified inverted BiB with a scoop at the bottom.
it seems to me that there is little difference in the line between these two whether sloped or curved since a flaring occurs at the "turning point" in the line (the point where the sound moved up in the BiB or down in the headlund).
as for the filter chamber effect, the inside of the headlund is similar to the very top of the BiB in that at some point the front and the back meet at a single point with very little clearance. so i believe this is "negligible". to me the largest difference is the scoop.
regardless of whether this is ideal or no, these sound real good for all types of music i've listened to on them and good for listening to dialogue only. as someone has said in these posts - the B20s are not fatiguing. i can listen to them all day.
originally the offset was 1.5" and the sound resulted in "husky" sounding voices with poor bass. also the "original" damping material (eggshell foam) and original wiring were replaced.
while the headlund has a slick curved area at the top, what i meant by the similarity in the line between them and the BiB is that the headlund looks like a modified inverted BiB with a scoop at the bottom.
it seems to me that there is little difference in the line between these two whether sloped or curved since a flaring occurs at the "turning point" in the line (the point where the sound moved up in the BiB or down in the headlund).
as for the filter chamber effect, the inside of the headlund is similar to the very top of the BiB in that at some point the front and the back meet at a single point with very little clearance. so i believe this is "negligible". to me the largest difference is the scoop.
regardless of whether this is ideal or no, these sound real good for all types of music i've listened to on them and good for listening to dialogue only. as someone has said in these posts - the B20s are not fatiguing. i can listen to them all day.
>>> the B20s are not fatiguing. i can listen to them all day.
Me too. Add the tweeter to make it sound even better! Unless you compare the B20 to something better it always sounds balanced and mellow. Just imagining the B20 in a Hedlund cracks me up... that they are made from mdf seems fitting for this application... but it would not surprise me if you popped a Lowther into one of the cabinets, compared and preferred the B20 because of it's overall laid back character. Maybe you can fine tune the Hedlund's, finish them off and own something really unique. Enjoy them!
Godzilla
Me too. Add the tweeter to make it sound even better! Unless you compare the B20 to something better it always sounds balanced and mellow. Just imagining the B20 in a Hedlund cracks me up... that they are made from mdf seems fitting for this application... but it would not surprise me if you popped a Lowther into one of the cabinets, compared and preferred the B20 because of it's overall laid back character. Maybe you can fine tune the Hedlund's, finish them off and own something really unique. Enjoy them!
Godzilla
couldn't recall who said this first - listening to the B20 w/out fatigue. but that's an important aspect. try listening to klipsch speakers without fatigue?
the original owner had lowthers in them!
the humor of the situation is well noted: a cheap driver installed in prototype cabs designed for an esoteric driver at a cost of the gas to get the cabs, the drivers, and the few mods that will be made. < $200 and they sound spectacular! the little red engine that could, huh?
these cabs are 1" mdf to boot! they do need some stain and do need some mods. probably use one of the latex outdoor "earth colored" stains similar to an adobe color at some point. the top curve is "bumpy" due to the mounting surfaces and would require a bit of sanding. this would require the speakers would be out of commission for a while.
the one thing that the hedlunds really need help with is the framing support. how to accomplish it without being obtrusive even more so that a 7' pair of cabs in the room? these use angle brackets mounted along the back to the floor for a stand.
and i do need to redo the offset mounting plates due to a discovery that the router circle cutter doesn't cut circles < 8" in diameter. i made one of the makeshift jigs for the router out of the 3/16" fiber board but need to make a better one as this slipped a bit. also will probably use plywood for the new offsets.
might even do better with a small "box" on the front of the cabs instead of the offset. kinda like the swans mounting box.
but can't get to anything for a while due to necessary outdoor projects.
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