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yeah, it's a lot easier to do your own designs if you're building a SS amplifier - lots of knowledge is published in great detail, lots of designs to borrow from and free Spice simulations to support it. You see many crazy ideas and a lot of interesting projects.
But for speakers I don't think it's limited to empirical work - there's the famous spreadsheets from Martin King, although I understand some investment in time and effort is needed to get the most out of them.
Anyhow, I figure the BVR is worth exploring.
In my case, for a narrower box for my sister, I think I could scale a Derwent down - albeit at the expense of breathing space for the back of the driver. I believe the design can't really be chopped up into pieces, I suspect it has to be modelled as a 'whole' but I think a little experimentation with the length of the short 'vent' between the interior volume and the horn section would allow some empirical tuning if I built it. And my ears may never know if I get it a little wrong
But for speakers I don't think it's limited to empirical work - there's the famous spreadsheets from Martin King, although I understand some investment in time and effort is needed to get the most out of them.
Anyhow, I figure the BVR is worth exploring.
In my case, for a narrower box for my sister, I think I could scale a Derwent down - albeit at the expense of breathing space for the back of the driver. I believe the design can't really be chopped up into pieces, I suspect it has to be modelled as a 'whole' but I think a little experimentation with the length of the short 'vent' between the interior volume and the horn section would allow some empirical tuning if I built it. And my ears may never know if I get it a little wrong
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I am also from the 'make it and find out' school. I do love to understand what I am doing though and have been pursuing the design of my own modelling tools to look at some of these 'penumbral' loading systems. I use the MJK worksheets and Akabak mainly, and both are very useful.
Good luck with your BVR! Let me know how it turns out.
Rgds
blakkmeister
ps., should add that there are a lot of people here who give freely, both advice and designs.
Good luck with your BVR! Let me know how it turns out.
Rgds
blakkmeister
ps., should add that there are a lot of people here who give freely, both advice and designs.
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Don't know!
I would guess MJK's worksheets.
If you can't interpret the sims, you're dead in the water, so to speak.
After spending hundreds of hours, and more hundreds (thousands?) of dollars on material to perfect a design, why would you. Especially, if you're afraid someone is going to steel your design and market something based on it.
jeff
I think that it is not a case so much that BVRs are under represented as not recognized when you see them.
Scott did bring the Olson/Nagaoka aesthetic to their design.
As to designing these, Scott (and others) have their own proprietary tools, but there is still an element of extrapolation based on experience.
MJK does not take into account all the factors in a BVR like Scott's, while it should be able to deal with ones with vents that have vent aspects closer to 1 (like the replikons). Akabak might be able to model them
dave
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I remember reading that before MJK there was a lot of old wives tales floating around about how to design a TL (or MLTL) box and now, with MJK's work, there is some clarity and understanding about this approach so it's much easier for DIY'ers to jump in. Even if building a proven speaker plan, it's nice to know how the darn things work.
If the BVR is in this camp, where we don't really know what we're doing unless we have the kind of experience Scott has - and which quite frankly I have no possibility of acquiring - then we may also be stuck with hearsay as to how to design for this type of box. And so the DIY community can not advance the art, it is limited to building proven plans. I wonder if MJK would be interested to turn his spotlight on this type of enclosure and make it more accessible to us
I don't know anything about Akabak, but I just read that it's ancient and needs a special environment to run in.
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I wonder if MJK would be interested to turn his spotlight on this type of enclosure and make it more accessible to us
As i understand it Martin
s model is 1D, and to cover off the high aspect ratio of the start of Scott's vents, the model would need to be 2D or have a fudge factor that recognizes this in the geometry and then adjust for it. The latter would likely require a bunch of empirical tuning of the fudge factor.
DOS i believe. Could well be easier to run DOS on a Mac now than under the latest versions of windoz.
dave
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DOS - oh my gosh, I'm not going there.
Let me put my question in another way - BVR - if this is essentially a bass reflex design, with a big vent, then the box is still a tuned volume. The key parameter is therefore the frequency that the box is tuned to and providing that the tuning frequency is where the designer wants it, the thing should sing just fine. There will be some subtleties lost, things that Scott has incorporated into his design that mortals don't understand, but the fundamental performance should be very closely related to how the box is tuned.
If this is the case, then it's not such a challenge to allow for some empirical adjustment of the vent prior to final glue-up, especially if I use one of Scotts' designs as a starting point.
What am I missing here ?
Let me put my question in another way - BVR - if this is essentially a bass reflex design, with a big vent, then the box is still a tuned volume. The key parameter is therefore the frequency that the box is tuned to and providing that the tuning frequency is where the designer wants it, the thing should sing just fine. There will be some subtleties lost, things that Scott has incorporated into his design that mortals don't understand, but the fundamental performance should be very closely related to how the box is tuned.
If this is the case, then it's not such a challenge to allow for some empirical adjustment of the vent prior to final glue-up, especially if I use one of Scotts' designs as a starting point.
What am I missing here ?
Have you read the Spawn intro on the FH site? That will point you to other (explicit) BVRs? Many small horns, for that matter, a daline, are BVRs.
dave
There’s a good size library of published literature in speaker, TL, horn design theory dating back to at least the 1920s, though never seen any for MLTLs per se since apparently Olson didn’t see his late ‘40s vented tower/column speaker as sufficiently different enough from a pure reflex to justify patenting it. Then there’s his and others technical books on acoustical loading as well as musical instrument design and the plethora of professional technical papers from dozens of authors over the ensuing decades.
Regardless, you seem to understand BVR/BLH loading at its ‘fundamental’
.GM
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thanks ! - this was a very useful thread. Just gets me more interested in the BVR approach and the possibility of designing one to the outer dimensions of the totem arro based on an EL-70 or CHR-70 driver. I will give this further thought!
Note that that like (and others) have been in the Spawn section of frugal-horn.com (home of Scott's BR) for 4 years...
dave
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I guess it's a case of better late than never.
There are so many different names and so many different speaker designs that for most part I have not been able to 'see the wood for the trees'. I found the same with amplifier design, fancy names for all the different circuits - cascodes, cascades, White followers, capacitance multipliers etc. and it was quite awhile before I could see the whole picture and the connections between them all.
I'm seeing that you can't categorize speakers along clear lines either, it's all a spectrum. Take the FH3, is it a horn, or is it a BVTL (big vent transmission line) or is it both and something else besides !
Actually now that I think of it, perhaps the FH3 is easier to scale since it's mostly a TL and all I need to do is keep the CSA and length the same... hmmm, a little knowledge is a dangerous thing
And now that I think about what I'd like in terms of form factor (totem arro) it's not clear that it will behave as a reflex enclosure when so long and thin, it's bit between a TL and a BR. Can one add a big vent to a Pensil ?
There are so many different names and so many different speaker designs that for most part I have not been able to 'see the wood for the trees'. I found the same with amplifier design, fancy names for all the different circuits - cascodes, cascades, White followers, capacitance multipliers etc. and it was quite awhile before I could see the whole picture and the connections between them all.
I'm seeing that you can't categorize speakers along clear lines either, it's all a spectrum. Take the FH3, is it a horn, or is it a BVTL (big vent transmission line) or is it both and something else besides !
Actually now that I think of it, perhaps the FH3 is easier to scale since it's mostly a TL and all I need to do is keep the CSA and length the same... hmmm, a little knowledge is a dangerous thing
And now that I think about what I'd like in terms of form factor (totem arro) it's not clear that it will behave as a reflex enclosure when so long and thin, it's bit between a TL and a BR. Can one add a big vent to a Pensil ?
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Scaling is actually easy once you understand the physics of the situation, but unless you have the math skills to work it out long hand or have a fairly unique way of looking at such things, it's not intuitive.
Trust me, I know, as scaling horn pictures using a Pantograph in my teenie-bopper years and loading them with a variety of used tabletop radio, TV, etc., drivers is how I got started and as you can imagine, I got some rather strange sounding speakers that had just about convinced me to give up on such 'flights of fantasy' as my mom called them when one day I lucked up big time! I happened to find an oval driver that sounded good enough in one of my largest scaled horn cabs [Altec 211, I learned several years later] once stuck in a corner that it became the rage within my 'circle of influence', with a number of copies made, 'hooking' me on this hobby.
Of course I had no clue how to reverse engineer it, much less scale it, that was still ~ a decade away before I'd accumulated enough knowledge since I couldn't do the math in the textbooks loaned from the Ga. Tech library.
Now that I know approximately what its driver specs was and that it still lives on as a staple of car audio, I've considered building another one to see how bad it really was referenced to 'FR' driver HIFI as we know it today. Since all we had available were various AM radios to drive them, I'm guessing the ~flat source BW was limited to ~ a phone's ~250-2500 Hz BW, so anything but 'full-range'.
GM
Trust me, I know, as scaling horn pictures using a Pantograph in my teenie-bopper years and loading them with a variety of used tabletop radio, TV, etc., drivers is how I got started and as you can imagine, I got some rather strange sounding speakers that had just about convinced me to give up on such 'flights of fantasy' as my mom called them when one day I lucked up big time! I happened to find an oval driver that sounded good enough in one of my largest scaled horn cabs [Altec 211, I learned several years later] once stuck in a corner that it became the rage within my 'circle of influence', with a number of copies made, 'hooking' me on this hobby.
Of course I had no clue how to reverse engineer it, much less scale it, that was still ~ a decade away before I'd accumulated enough knowledge since I couldn't do the math in the textbooks loaned from the Ga. Tech library.
Now that I know approximately what its driver specs was and that it still lives on as a staple of car audio, I've considered building another one to see how bad it really was referenced to 'FR' driver HIFI as we know it today. Since all we had available were various AM radios to drive them, I'm guessing the ~flat source BW was limited to ~ a phone's ~250-2500 Hz BW, so anything but 'full-range'.
GM
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