From the alignments B4, QB3, C4, SBB4 and BB4 I prefer clearly the last, when I want to have a high efficiency sat box with tuning frequency between 55Hz and 110Hz together with an additional high pass filter.
In Richard H. Small's paper "Vented-Box Loudspeaker Systems" (Part I-IV) under
https://sdlabo.jp/archives/Vented_Box_Loudspeaker Systems_Part_1-4.pdf
there are only small information on page 322 concerning this to find (actually only scorned resp. derogative):
Similar effects occur with other alignments. It is not difficult to see why the vented enclosure is sometimes scorned as a "boom box" when it is realized that the values of QT required are much Iower than the majority of woofers provide [15, Table 13] and that a historical emphasis on unity tuning ratio regardless of compliance ratio often results in erroneously high tuning.
Otherwise I will not find anything about the BB4 alignment.
OTOH such an alignment is obtained when the surface area of vented port corresponds to that of the diaphragm area from the bass transducer resp. driver, as long the volume of cabinet is below approximately 100 liters - for an example check out the mid-bass unit, left side on last image in post #5 under
https://www.diyaudio.com/community/...oofer-precision-devices-pd2150-inside.197034/
Along with a high pass filter one will get very clean and tight bass in the area between 60-200Hz so as a very high efficiency character.
In the frequency area between 20Hz and 120Hz I have a lot of experience with high pass filtered BB4 alignments.
Thus the most important question is for me currently up to which maximum possible frequency area one can operate according such an alignment without having to accept any disadvantages in sound quality. This I haven't check until now.
This I want to know because I'm thinking about a vented box with BB4 character with Fostex FE83 - go to
https://www.fostexinternational.com/docs/speaker_components/pdf/FE83NV2.pdf
and a very small volume (tuning frequency maybe 200-300Hz so as highest possible efficiency.
Thanks in advance for an advice.
P.S.: under
https://www.diyaudio.com/community/threads/loudspeaker-alignment-questions.42386/
there are no information to find concerning this.
In Richard H. Small's paper "Vented-Box Loudspeaker Systems" (Part I-IV) under
https://sdlabo.jp/archives/Vented_Box_Loudspeaker Systems_Part_1-4.pdf
there are only small information on page 322 concerning this to find (actually only scorned resp. derogative):
Similar effects occur with other alignments. It is not difficult to see why the vented enclosure is sometimes scorned as a "boom box" when it is realized that the values of QT required are much Iower than the majority of woofers provide [15, Table 13] and that a historical emphasis on unity tuning ratio regardless of compliance ratio often results in erroneously high tuning.
Otherwise I will not find anything about the BB4 alignment.
OTOH such an alignment is obtained when the surface area of vented port corresponds to that of the diaphragm area from the bass transducer resp. driver, as long the volume of cabinet is below approximately 100 liters - for an example check out the mid-bass unit, left side on last image in post #5 under
https://www.diyaudio.com/community/...oofer-precision-devices-pd2150-inside.197034/
Along with a high pass filter one will get very clean and tight bass in the area between 60-200Hz so as a very high efficiency character.
In the frequency area between 20Hz and 120Hz I have a lot of experience with high pass filtered BB4 alignments.
Thus the most important question is for me currently up to which maximum possible frequency area one can operate according such an alignment without having to accept any disadvantages in sound quality. This I haven't check until now.
This I want to know because I'm thinking about a vented box with BB4 character with Fostex FE83 - go to
https://www.fostexinternational.com/docs/speaker_components/pdf/FE83NV2.pdf
and a very small volume (tuning frequency maybe 200-300Hz so as highest possible efficiency.
Thanks in advance for an advice.
P.S.: under
https://www.diyaudio.com/community/threads/loudspeaker-alignment-questions.42386/
there are no information to find concerning this.
I’d say not suited to vented at all.
A series of sims: sealed, 5/2.5 litre reflex. A lot of ugly sims.
For clarity the sealed, and a not as bad as the rest vented.
Looks to be a good candidate for (big) sealed, or better yet midTL out the back.
dave
PS: those ‘TLA’ alignments were convienient way posts in the days when we figured things out pencil and paper. Now we can easily explore the continuum of alignments.
A series of sims: sealed, 5/2.5 litre reflex. A lot of ugly sims.
For clarity the sealed, and a not as bad as the rest vented.
Looks to be a good candidate for (big) sealed, or better yet midTL out the back.
dave
PS: those ‘TLA’ alignments were convienient way posts in the days when we figured things out pencil and paper. Now we can easily explore the continuum of alignments.
Do you know what BB4 stands for or where it originates? If it really stands for boom box, it is exactly what Thiele and Small tried to avoid.
This is Thiele's famous table of loudspeaker alignments with reasonably flat responses:
The fifth- and sixth-order alignments require a first- or second-order electrical high-pass filter somewhere in the signal path.
He also found a way to interpolate between the alignments (see the last two columns), so in that sense he did explore the continuum of alignments, and didn't even need a computer for it.
This is Thiele's famous table of loudspeaker alignments with reasonably flat responses:
The fifth- and sixth-order alignments require a first- or second-order electrical high-pass filter somewhere in the signal path.
He also found a way to interpolate between the alignments (see the last two columns), so in that sense he did explore the continuum of alignments, and didn't even need a computer for it.
I've never seen (and I still don't see) anything 'disparaging' or 'scornful' in Small's work. BB4 is an abbreviation for 'boom box' and the reference apparently taken as an insult I've always read simply as an observation about the perceieved acoustic charactertistics of underdamped vented box / bass reflex alignments with no correction applied.
Small was writing in essence an academic scientific / engineering paper derived from his doctoral thesis under Thiele, so in general his language is quite precise, although also slightly selective since he does not really reference the fact that quality examples of prior acoustically efficient vented boxes would almost always be adjusted or damped to avoid excess ringing (usually the result of an underdamped Fb). It was in his interest to present his superb work in the most positive light -without making specifically misleading statements. But it's important to view it in context too -it builds upon foundations laid by Thiele, Novak and others. Be that as it may -nothing really wrong with some of the filtered alignments if that's what's preferred. I suspect the main reason they never took off in popularity is simply because of the added complexity, and relatively few know about them today. Plus, with the advent of software modellers, in many cases people simply never felt the need.
Small was writing in essence an academic scientific / engineering paper derived from his doctoral thesis under Thiele, so in general his language is quite precise, although also slightly selective since he does not really reference the fact that quality examples of prior acoustically efficient vented boxes would almost always be adjusted or damped to avoid excess ringing (usually the result of an underdamped Fb). It was in his interest to present his superb work in the most positive light -without making specifically misleading statements. But it's important to view it in context too -it builds upon foundations laid by Thiele, Novak and others. Be that as it may -nothing really wrong with some of the filtered alignments if that's what's preferred. I suspect the main reason they never took off in popularity is simply because of the added complexity, and relatively few know about them today. Plus, with the advent of software modellers, in many cases people simply never felt the need.
BB4 is just an alignment -it happens to include a high pass filter network as a functional part of it, and within a broad range of characteristics it can in theory be applied to a very wide range (most) drive units if you felt like doing so. I was basically just reflecting on its lack of popularity, which I suspect is due to following three reasons:
1/ It's quite obscure, and not everyone has even heard of it
2/ Added complexity (and cost), especially if done passively. And
3/ With the advent of easily accessible / freely available software modellers, most designers no longer needed to rely on a series of fixed tabulated alignments, but could rapidly model an essentially infinte range of possiblities, and for the majority of people there was variety enough in that, without them ever needing to use or even investigate more complex / esoteric filtered alignments like BB4.
1/ It's quite obscure, and not everyone has even heard of it
2/ Added complexity (and cost), especially if done passively. And
3/ With the advent of easily accessible / freely available software modellers, most designers no longer needed to rely on a series of fixed tabulated alignments, but could rapidly model an essentially infinte range of possiblities, and for the majority of people there was variety enough in that, without them ever needing to use or even investigate more complex / esoteric filtered alignments like BB4.
As GM said.
You had to ask.
BB4 is easy enough: 4th order Boom Box. Although it also gets a bit hazy. On the face of it, the above is 'it'; as far as I remember, BB4 & SBB4 orginated with Hoge. However -somewhere along the line, it apparently occured to some bright spark that since it's a nominally peaking alignment at Fb, it could be filtered in a similar way to what Thiele had previously proposed for a number of 5th & 6th order alignments, so you can sometimes find variations done like that -which is probably a better way of using them & is what I understand the OP was referring to using. It's not strictly part of the acoustic alignment in itself, but it's a way of using it to reasonable effect, like the slightly higher order alignments Thiele came up with, so they sometimes get tacked together.
You had to ask.
BB4 is easy enough: 4th order Boom Box. Although it also gets a bit hazy. On the face of it, the above is 'it'; as far as I remember, BB4 & SBB4 orginated with Hoge. However -somewhere along the line, it apparently occured to some bright spark that since it's a nominally peaking alignment at Fb, it could be filtered in a similar way to what Thiele had previously proposed for a number of 5th & 6th order alignments, so you can sometimes find variations done like that -which is probably a better way of using them & is what I understand the OP was referring to using. It's not strictly part of the acoustic alignment in itself, but it's a way of using it to reasonable effect, like the slightly higher order alignments Thiele came up with, so they sometimes get tacked together.
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In the German book from elektor (concerning speaker diy projekts) "Aufbau - Umbau - Nachbau" - go to the first both images in post 25 under
https://www.diyaudio.com/community/...speaker-design-and-construction.182366/page-2
so as seventh image under
https://winboxsimu.de/reload.html?Lit_Info.html
the BB4 was mentioned and explain more in detail.
I will try to rent this book next time and will scan the associated pages.
When I recall right there was mantioned that in general not filtered BB4 alignments are prefer for instrumental loudspeakers as part of a combination with a musical instrument (such as an electric bass guitar) to get special sound character - similar like this model under
https://www.glockenklang.de/en/products/bass_systems/take_five.htm
But I don't know whether just this model is a really BB4 alignment.
Not amazing, as people do the weirdest things for electric guitar amplifiers: apply soft clippers, hard clippers, deliberately design amplifier stages to have a bias point that shifts with the signal in such a way that it causes more distortion, current drive loudspeakers without any equalization and without any motional feedback, basically everything you don't want in HiFi equipment.
In your opening post, you wrote: "high efficiency sat box with tuning frequency between 55Hz and 110Hz together with an additional high pass filter." According to post #2, your driver has a Qts of 0.78, which is close to the 0.81 needed for Thiele's alignment 12, fifth-order Chebyshev using a first-order high-pass filter. Why not try that? You get a -3 dB frequency of 108 Hz with the box tuned to 122 Hz then, using a 271 Hz first-order high-pass.
In your opening post, you wrote: "high efficiency sat box with tuning frequency between 55Hz and 110Hz together with an additional high pass filter." According to post #2, your driver has a Qts of 0.78, which is close to the 0.81 needed for Thiele's alignment 12, fifth-order Chebyshev using a first-order high-pass filter. Why not try that? You get a -3 dB frequency of 108 Hz with the box tuned to 122 Hz then, using a 271 Hz first-order high-pass.
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If you want the originator of the BB4 alignment, as I mentioned above it's basically one Hoge derived & others later (if they felt so inclined ) have done assisted / filtered variations of a la Thiele's, and later Keele's 5th & 6th order variations.
The original paper was to the AES back in June '77 ('A New Set of Vented Loudspeaker Alignments'); he's got a condensed version up on his site here: http://www.wjjhoge.com/Electroacoustics/bb4/bb4.html
) have done assisted / filtered variations of a la Thiele's, and later Keele's 5th & 6th order variations.The original paper was to the AES back in June '77 ('A New Set of Vented Loudspeaker Alignments'); he's got a condensed version up on his site here: http://www.wjjhoge.com/Electroacoustics/bb4/bb4.html
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Because the max. possible SPL is too low compare with a tuning frequency of e. g. 250 Hz or even 300 Hz - maybe realized with a vented port which has a sufficiently large surface (for a f3 of 200-250Hz).
But because I have no idea whether this is possible in general, I started this thread.
P.S.: Thank you very much for the URL
http://www.wjjhoge.com/Electroacoustics/bb4/bb4.html
In this case I have additional found the attached PDF so as this URL's:
https://www.andyc.diy-audio-enginee...y-audio-engineering.org/vented-box/index.html
https://sound-au.com/articles/cscaling.htm
https://www.diyaudio.com/community/threads/the-many-parallel-tda7293-ace-bass-amp-project.264726/
https://www.diyaudio.com/community/...fer-using-a-cap-instead-of-a-resistor.273701/
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A German translation of this paper under
https://sdlabo.jp/archives/Vented_Box_Loudspeaker Systems_Part_1-4.pdf
was published in the magazine ELRAD (not ELEKTOR - one of the special issues concerning HiFi loudspeakers - go to the attached cover images, but please note that I don't know if this showed images are exact of the issue I am looking for).
Who know the issue No and maybe an URL for download ?
https://sdlabo.jp/archives/Vented_Box_Loudspeaker Systems_Part_1-4.pdf
was published in the magazine ELRAD (not ELEKTOR - one of the special issues concerning HiFi loudspeakers - go to the attached cover images, but please note that I don't know if this showed images are exact of the issue I am looking for).
Who know the issue No and maybe an URL for download ?
