Now that we have some discussion of different drivers as well as possible starting points for dimensions, I wonder if we might look at some places to look for improvements of the basic design. After all, Terry saw his build as nothing but a starting point.
In my ignorance of TQWP's, a few ideas come to mind:
1) Everyone with an understanding of these designs seems to agree that having the closed end of the pipe come to a sharp point is a bad idea. How about truncating it? It complicates the very simple construction of the BIB slightly, but some people seem willing to put a whole lot of effort into the things, so this doesn't seem like too much extra work.
2) Corner boards in the fold. Some have commented that they doubt they'll make much difference. Other's that have experimented with other folded pipes testify that they do make a difference. Even without a deep understanding of these particular designs, it makes sense that those sharp corners and flat bottom can only cause unwanted anomalies.
I once had the opportunity to listen to two TQWP's that were very similar except that one was folded and one was not. The unfolded version was the winner without doubt; it presented much more clear sound while the folded one got a little muddy sometimes. I doubt I would have noticed it if I didn't A/B it with the unfolded version. The difference might have been due to a lot of things, but I have to think that part of it was because of the fold. Reducing the impact of the fold seems like a worthwhile way to spend some effort.
3) The mouth opening. It was suggested early in this thread that sloping the opening back (pointing towards the back wall) would increase the mouth area and possibly bring some benefit. I have to think that if the speaker is positioned tight against the room wall, then we would want to slope the opening towards the front. We're not looking to increase the reflections off the wall, but to use the wall to increase the effective mouth area.
I've attached a diagram giving an idea of how I think these changes might be included.
In my ignorance of TQWP's, a few ideas come to mind:
1) Everyone with an understanding of these designs seems to agree that having the closed end of the pipe come to a sharp point is a bad idea. How about truncating it? It complicates the very simple construction of the BIB slightly, but some people seem willing to put a whole lot of effort into the things, so this doesn't seem like too much extra work.
2) Corner boards in the fold. Some have commented that they doubt they'll make much difference. Other's that have experimented with other folded pipes testify that they do make a difference. Even without a deep understanding of these particular designs, it makes sense that those sharp corners and flat bottom can only cause unwanted anomalies.
I once had the opportunity to listen to two TQWP's that were very similar except that one was folded and one was not. The unfolded version was the winner without doubt; it presented much more clear sound while the folded one got a little muddy sometimes. I doubt I would have noticed it if I didn't A/B it with the unfolded version. The difference might have been due to a lot of things, but I have to think that part of it was because of the fold. Reducing the impact of the fold seems like a worthwhile way to spend some effort.
3) The mouth opening. It was suggested early in this thread that sloping the opening back (pointing towards the back wall) would increase the mouth area and possibly bring some benefit. I have to think that if the speaker is positioned tight against the room wall, then we would want to slope the opening towards the front. We're not looking to increase the reflections off the wall, but to use the wall to increase the effective mouth area.
I've attached a diagram giving an idea of how I think these changes might be included.
Attachments
Some interesting points well raised. I'd classify them as being closer to horns though than TQWTs -see the intro. Jeff, the pages look fantastic BTW -a massive vote of thanks on behalf of us all for designing and hosting them.
Hmm. So=0 is often seen to be automatically bad. I was guilty of that assumption too until a few months ago when Greg opened my eyes somewhat. It's not. In fact, it can have some real advantages. Trouble is, it's a right pain to design an So=0 design properly to get the benefits without getting clobbered by the problems it can have unless you've very careful. The trunkated types are easier. A trunkated BIB could be interesting, though the expansion is a little different. I've never felt the need, as I've been happy with my So=0 types but it might be worth looking into. Greg, Martin, guys -any thoughts?
Re the corner boards, I'm not sure. I tried them in one project and didn't hear any benefit, or measure any difference, but that's not to say you wouldn't of course. Then again, bass frequencies aren't likely to be that fussy anyway, but there's certainly room for experiment -I was using some spectacualrly cheap Electrovision drivers at the time that were hardly hifi quality, which probably rendered the experiment moot.
Peter -glad they're going together soon. Enjoy! You're not going to loose out on anything with the very fractionally shorter line-length BTW. Everything else is effectively the same, so there's very little in it. That's just me having some fun trying to squeeze the last drop of low-end out of the thing whilst not causing it to bottom out.
Regards
Scott
Hmm. So=0 is often seen to be automatically bad. I was guilty of that assumption too until a few months ago when Greg opened my eyes somewhat. It's not. In fact, it can have some real advantages. Trouble is, it's a right pain to design an So=0 design properly to get the benefits without getting clobbered by the problems it can have unless you've very careful. The trunkated types are easier. A trunkated BIB could be interesting, though the expansion is a little different. I've never felt the need, as I've been happy with my So=0 types but it might be worth looking into. Greg, Martin, guys -any thoughts?
Re the corner boards, I'm not sure. I tried them in one project and didn't hear any benefit, or measure any difference, but that's not to say you wouldn't of course. Then again, bass frequencies aren't likely to be that fussy anyway, but there's certainly room for experiment -I was using some spectacualrly cheap Electrovision drivers at the time that were hardly hifi quality, which probably rendered the experiment moot.
Peter -glad they're going together soon. Enjoy! You're not going to loose out on anything with the very fractionally shorter line-length BTW. Everything else is effectively the same, so there's very little in it. That's just me having some fun trying to squeeze the last drop of low-end out of the thing whilst not causing it to bottom out.
Regards
Scott
yeah...
so I was thinking of doing on this build a multi layer back panel but stepped. kinda like the horn mouths on fostex reccommended back horns. it would be easy to do with no mitre, like me.
to make the top end of the compression chamber not a point, I stuffed a little with some dense wool peices.
benifit of strike panels is that they could be filled with sand for good floor coupling and solidity.
this horn design is sooo cool. sooo adaptable. they just sound fun too.
in either case, I am pretty sure that some of the right angles in alot of horn designs are meant to be seen as obsticles to higher frequencies and not so with bass frequencies. it is a natural low pass filter... something to think about. that right angle designs might have less high frequencies coming out of the horn than curved designs. not so much in this design because the coloured wave hits the ceiling and disperses before the ear. it varies I guess. horns are very tricky and rarely behave precisely as modeled I guess. it is hard to generalize, repeat for the sake of scientific method, etc. even frequently I have found that to me, personally, the coloured wave is both fun and desirable in many designs. especially if the tone of the wood is up to snuff. see terry cain's IM-bens for proof of potential of the use of this wave.
photos on the way...
Clark
so I was thinking of doing on this build a multi layer back panel but stepped. kinda like the horn mouths on fostex reccommended back horns. it would be easy to do with no mitre, like me.
to make the top end of the compression chamber not a point, I stuffed a little with some dense wool peices.
benifit of strike panels is that they could be filled with sand for good floor coupling and solidity.
this horn design is sooo cool. sooo adaptable. they just sound fun too.
in either case, I am pretty sure that some of the right angles in alot of horn designs are meant to be seen as obsticles to higher frequencies and not so with bass frequencies. it is a natural low pass filter... something to think about. that right angle designs might have less high frequencies coming out of the horn than curved designs. not so much in this design because the coloured wave hits the ceiling and disperses before the ear. it varies I guess. horns are very tricky and rarely behave precisely as modeled I guess. it is hard to generalize, repeat for the sake of scientific method, etc. even frequently I have found that to me, personally, the coloured wave is both fun and desirable in many designs. especially if the tone of the wood is up to snuff. see terry cain's IM-bens for proof of potential of the use of this wave.
photos on the way...
Clark
Greets!
To find the theoretical acoustic path of a folded pipe you find the center of the cross sectional area (CSA) at all points along the line, so down the middle for straight constant area sections and the SQRT of the inside radius times the outside radius for curved bends. For the BIB's corners, calcing the diagonal CSA's apparent 'curved' center from the corner to the end of the baffle board is close enough.
Note that the BW below a corner's passband is acoustically large enough that sharp corners have no audible impact on the pipe's performance, which in round numbers is a frequency = < ~13560" (34442.4 cm)/WL/pi (the WL's diameter), which is often (mis) quoted as < 1/3 WL in folded design discussions on the various forums, so the smoother and larger the fold's radius, the greater its passband, ergo for long pathlengths in back loaded designs, they are to be avoided like the plague since the terminus's output will be increasingly out of phase (time) with increasing frequency. IOW, sharp, abrupt folds act as acoustic low pass filters, attenuating unwanted HF output from exiting the terminus.
GM
To find the theoretical acoustic path of a folded pipe you find the center of the cross sectional area (CSA) at all points along the line, so down the middle for straight constant area sections and the SQRT of the inside radius times the outside radius for curved bends. For the BIB's corners, calcing the diagonal CSA's apparent 'curved' center from the corner to the end of the baffle board is close enough.
Note that the BW below a corner's passband is acoustically large enough that sharp corners have no audible impact on the pipe's performance, which in round numbers is a frequency = < ~13560" (34442.4 cm)/WL/pi (the WL's diameter), which is often (mis) quoted as < 1/3 WL in folded design discussions on the various forums, so the smoother and larger the fold's radius, the greater its passband, ergo for long pathlengths in back loaded designs, they are to be avoided like the plague since the terminus's output will be increasingly out of phase (time) with increasing frequency. IOW, sharp, abrupt folds act as acoustic low pass filters, attenuating unwanted HF output from exiting the terminus.
GM
Hello everyone,
Been following this intresting tread for a while, and now I'm ready to try my first pair of diy speaker. The BIB looks like a fairly simple and promising unit to try.
Thanks everybody for the great investigating work on this subject.
I have a pair of fe-103 s to try out. They have been placed in cardboard box to break in for the last 3 monthes. I was originally want to put them in the bhorn2. Now i'm leaning toward the BIB.
I'm confused about the "correct" dim for the cab though. I read early on in the thread that the 103s can share the same dim as the TBs as in a 5.5 X 10.5 X 60 cab. But on Zilla's wsb site, the 103s are listed as with a line length of 85, which will translate to about 42.5 inside height, right? Which dim. should I follow.
Thanks again for everybody's great work on this subject. BTW, I made a cardboard BIB following the TBs size for 103e. The increase in spl is very noticable compare to cardboard BR they were in
If this is indicate of things then the proper built BIB 103 could be a pretty good outcome.
Tia
Have a nice weekend everyone
Lei
Been following this intresting tread for a while, and now I'm ready to try my first pair of diy speaker. The BIB looks like a fairly simple and promising unit to try.
Thanks everybody for the great investigating work on this subject.
I have a pair of fe-103 s to try out. They have been placed in cardboard box to break in for the last 3 monthes. I was originally want to put them in the bhorn2. Now i'm leaning toward the BIB.
I'm confused about the "correct" dim for the cab though. I read early on in the thread that the 103s can share the same dim as the TBs as in a 5.5 X 10.5 X 60 cab. But on Zilla's wsb site, the 103s are listed as with a line length of 85, which will translate to about 42.5 inside height, right? Which dim. should I follow.
Thanks again for everybody's great work on this subject. BTW, I made a cardboard BIB following the TBs size for 103e. The increase in spl is very noticable compare to cardboard BR they were in
If this is indicate of things then the proper built BIB 103 could be a pretty good outcome. Tia
Have a nice weekend everyone
Lei
>>> I'm confused about the "correct" dim for the cab though. I read early on in the thread that the 103s can share the same dim as the TBs as in a 5.5 X 10.5 X 60 cab. But on Zilla's wsb site, the 103s are listed as with a line length of 85, which will translate to about 42.5 inside height, right? Which dim. should I follow.
When i mentioned to Scott i was going to put the site together he asked me to hold off on the original dims he provided. My appologies for leaving them on. I didnt mean to cause confusion. Scott then graciously re simmed everything for accuracy and sent me the newer sims and dims to post.
http://www.zillaspeak.com/bib-fostex.asp
I would use the dims on the above page.
Seems you could also substitute the 108eSigma for the 103 which is a pretty cool upgrade path.
or the TB Bamboo and the Fostex 127e
Neat stuff!
When i mentioned to Scott i was going to put the site together he asked me to hold off on the original dims he provided. My appologies for leaving them on. I didnt mean to cause confusion. Scott then graciously re simmed everything for accuracy and sent me the newer sims and dims to post.
http://www.zillaspeak.com/bib-fostex.asp
I would use the dims on the above page.
Seems you could also substitute the 108eSigma for the 103 which is a pretty cool upgrade path.
or the TB Bamboo and the Fostex 127e
Neat stuff!
Greets!
1) Everyone?! I know lots of pro and well regarded DIY horn designers that feel the corollary is true, but WTFDTK?
2), 3) I addressed these in previous posts.
A properly designed/built folded back loaded pipe sounds no different than its straight version. You can't just fold something up willy-nilly and expect optimum performance unless it has a very narrow BW.
Anyway, so far I haven't bothered to think in terms of improving the BIB's design beyond adapting it to dissimilar drivers, which for the most part has been limited to ~mimicking TC's half space simmed FR and impedance plots. The other ones I've done really shouldn't be a part of this thread and why I suggested a separate one along with a separate webpage.
With a depressingly short 'short term' memory, I don't recall what I posted that led you to this conclusion, but I certainly didn't mean to imply that it's any harder to design them than a truncated version. The only good acoustically related reason that comes to mind at the moment to use a truncated one is that it allows the driver to be optimally placed closer to the horn's throat for the smoothest response, ergo a high compression ratio (CR) TQWT is required to optimally place the driver at the closed end.
Remember, the top of a closed pipe is its acoustic throat, ergo its area defines its HF corner frequency, or 'Flh' in horn design-speak, so a pointed terminus has a theoretically infinite BW/highest potential gain and a maxed out end loaded TQWT has a BW centered at DC/no potential gain. The theoretically infinite number of variations in-between these two AFAIK unattainable extremes are for tailoring it to best meet the intended app's performance requirements.
Bottom line, without ~accurate measurements using the same driver BIB/electronics in a variety of different shaped/size rooms and locations within said rooms, trying to design audibly more accurate versions (as opposed to 'different', or in someone's opinion) is pretty much an exercise in futility IMO so 'color' me done' on this subject until a lot more hard data is available.
As always though, YMMV.
GM
Dave Cigna said:
1) Everyone?! I know lots of pro and well regarded DIY horn designers that feel the corollary is true, but WTFDTK?
2), 3) I addressed these in previous posts.
A properly designed/built folded back loaded pipe sounds no different than its straight version. You can't just fold something up willy-nilly and expect optimum performance unless it has a very narrow BW.
Anyway, so far I haven't bothered to think in terms of improving the BIB's design beyond adapting it to dissimilar drivers, which for the most part has been limited to ~mimicking TC's half space simmed FR and impedance plots. The other ones I've done really shouldn't be a part of this thread and why I suggested a separate one along with a separate webpage.
Scottmoose said:
With a depressingly short 'short term' memory, I don't recall what I posted that led you to this conclusion, but I certainly didn't mean to imply that it's any harder to design them than a truncated version. The only good acoustically related reason that comes to mind at the moment to use a truncated one is that it allows the driver to be optimally placed closer to the horn's throat for the smoothest response, ergo a high compression ratio (CR) TQWT is required to optimally place the driver at the closed end.
Remember, the top of a closed pipe is its acoustic throat, ergo its area defines its HF corner frequency, or 'Flh' in horn design-speak, so a pointed terminus has a theoretically infinite BW/highest potential gain and a maxed out end loaded TQWT has a BW centered at DC/no potential gain. The theoretically infinite number of variations in-between these two AFAIK unattainable extremes are for tailoring it to best meet the intended app's performance requirements.
Bottom line, without ~accurate measurements using the same driver BIB/electronics in a variety of different shaped/size rooms and locations within said rooms, trying to design audibly more accurate versions (as opposed to 'different', or in someone's opinion) is pretty much an exercise in futility IMO so 'color' me done' on this subject until a lot more hard data is available.
As always though, YMMV.
GM
This is a craft question:
I have been running into all sorts of mental problems
;-)
with the build itself: how to get a square fit with
pieces that will be butt jointed rather than mitered.
Most 1x6 I see in stores is cupped or crooked.
and that stuff in shrink wrap, who knows (?)
I have no bisquit cutter but that's one possibility.
Splines are another. Spacers and clamps, if used
carefully might solve some of the wavy gravy
problem.
I have been running into all sorts of mental problems
;-)
with the build itself: how to get a square fit with
pieces that will be butt jointed rather than mitered.
Most 1x6 I see in stores is cupped or crooked.
and that stuff in shrink wrap, who knows (?)
I have no bisquit cutter but that's one possibility.
Splines are another. Spacers and clamps, if used
carefully might solve some of the wavy gravy
problem.
Relax Greg, there's nothing wrong with your short term memory. It was reading one of your posts elsewhere a while ago that made me look into So=0 designs again after I'd abandoned them (incorrectly) as a bad job.
The bit of the post above re their design being awkward was based on my own (limited) experience with them. I've found in the past that the compression effects were somewhat tricky to predict / counter. Much less so now. But I still find them harder to get optimised than versions with trunkated throats.
Regards
Scott
The bit of the post above re their design being awkward was based on my own (limited) experience with them. I've found in the past that the compression effects were somewhat tricky to predict / counter. Much less so now. But I still find them harder to get optimised than versions with trunkated throats.
Regards
Scott
Hi
GM, would this be the correct line?
GM, I'm glad to read in your last postings, that there's no need to smoothen the corners, nor the pointed terminus. Too me, the facination and the beauty of the BIB design lies in it's simplicity!!! Six rectagular pieces of wood and one driver - no schnick schnack - plus a clever use of the environment (corner and celling). You hardly find something as beautifull these days, be it in design or in engineering.
best, LC
GM, would this be the correct line?
An externally hosted image should be here but it was not working when we last tested it.
GM, I'm glad to read in your last postings, that there's no need to smoothen the corners, nor the pointed terminus. Too me, the facination and the beauty of the BIB design lies in it's simplicity!!! Six rectagular pieces of wood and one driver - no schnick schnack - plus a clever use of the environment (corner and celling). You hardly find something as beautifull these days, be it in design or in engineering.
best, LC
GM said:
GM, thanks for your replay. I certainly wasn't attempting to start a debate!
I have read the entire thread as well as many others, here and elsewhere. But, as my technical understanding is still growing - and no where near as deep as I'd like - not everything is understood, never mind remembered. You might end up having to repeat yourself, possibly in different ways, possibly in more depth sometimes than others ....lovechild said:
It was indeed wrong
.... I shouldn't have messed with it. It only showed the length of the diagonal fold from inside the throat to the outside 'pointy' end, but not the "flow" of the Line... Where the Line starts as air pressure from the Throat -> down to the Internal Baffle Center... -> upwards to end of Line where the Mouth is.So for the Supra 215RTF example... Essentially a Hummer BiB.
L = 113"
So = 24.56" from the pointy top
Sm = 544"^2
20" (W) x 27.2" (D), then BiB height would be 70.1"
I see that the 165LB dims/response graphs are now included in Godzilla's page. Nice.
http://www.zillaspeak.com/BIB-Supravox.asp
Are dims published there also usable with the 165GMF? Or should I just stick to the one GM graciously provided?:
L = 105.93"
Sm = 220"^2
driver down 23.03" from the top.
Thanks. Happy Easter....
http://www.zillaspeak.com/BIB-Supravox.asp
Are dims published there also usable with the 165GMF? Or should I just stick to the one GM graciously provided?:
L = 105.93"
Sm = 220"^2
driver down 23.03" from the top.
Thanks. Happy Easter....
fred76 said:
It was indeed wrong
So for the Supra 215RTF example... Essentially a Hummer BiB.
L = 113"
So = 24.56" from the pointy top
Sm = 544"^2
20" (W) x 27.2" (D), then BiB height would be 70.1"
That BiB height and Depth has a line length of 133.4 if I have read the diagram correctly. You have ignored the half circle at the bottom. It is 21.4 inches.
I get a calculated height of 58.9 inches.
Sean
I just made a spreadsheet to check myself. For small depths and long line lengths dividing the line length by 2 generates a number slightly shorter than it should be. For shorter line lengths or larger depths error can accrue quickly with rough estimates.
The spreadsheet is simple. Input line length, So, Sm and Depth. It outputs Width and Height and driver Height. Please check for errors as it is late.
Note that with the FE-166 that range of all useable values only alters height by less than an inch. With the Supra 215 the Height varies about 2 inches over all reasonable values.
Sean
The spreadsheet is simple. Input line length, So, Sm and Depth. It outputs Width and Height and driver Height. Please check for errors as it is late.
Note that with the FE-166 that range of all useable values only alters height by less than an inch. With the Supra 215 the Height varies about 2 inches over all reasonable values.
Sean