Hi,
I'm starting my first project that will be mine from design on. So I decided to get a pair of Visaton BG20, because they are cheap and decent, and I can't f** up that many things.
Because I kind of like the design of Zu-audio speakers, I decided to try modeling something that would look kind of similar and perform good.
I've made a fully parametric model in Autodesk Fusion 360, so I can easily make changes.
The box has internal measurements of:
volume: 80L
bottom: 35x35cm
top: 28x28cm
height: 80cm
driver position: 18cm from top
port size: 40cm2, lengt is thickness of material, which is 18mm, located on the bottom of the box.
Attached are a sketch and fr plot.
I would really appreciate opinions on the design before I go searching for a CNC guy.
The only thing I'm not yet quite sure about is port placement. Floor-firing port is good because it looks sexy, but I'm afraid it might affect sound quality too much.
And another question: surface mounting the driver, or flush mounting? Do Zu and some other manufacturers go surface to get bulkier look, or do they have any sonic reasons?
I'm starting my first project that will be mine from design on. So I decided to get a pair of Visaton BG20, because they are cheap and decent, and I can't f** up that many things.
Because I kind of like the design of Zu-audio speakers, I decided to try modeling something that would look kind of similar and perform good.
I've made a fully parametric model in Autodesk Fusion 360, so I can easily make changes.
The box has internal measurements of:
volume: 80L
bottom: 35x35cm
top: 28x28cm
height: 80cm
driver position: 18cm from top
port size: 40cm2, lengt is thickness of material, which is 18mm, located on the bottom of the box.
Attached are a sketch and fr plot.
I would really appreciate opinions on the design before I go searching for a CNC guy.
The only thing I'm not yet quite sure about is port placement. Floor-firing port is good because it looks sexy, but I'm afraid it might affect sound quality too much.
And another question: surface mounting the driver, or flush mounting? Do Zu and some other manufacturers go surface to get bulkier look, or do they have any sonic reasons?
Attachments
I'd say go and get some cheap plywood or similar, hack up quick'n'dirty box and see how it works. Once you know how it behaves in the real world, build a nice version of the box.
A down firing port isn't necessarily bad. It has the advantage that some of the midrange garble emitted from the port is attenuated by reflections on the floor, or even absorbed in the carpet (if you have one). Also, changing the distance between the floor and the speaker will allow you to adjust the port tuning (the volume between the floor and the bottom of the speaker is part of the port).
Your computer model shows only the low frequency part. What about equalizers/filters (driver peaks, baffle step, etc.)?
Scottmoose made a simulation for the BG20 in a metronome enclosure that looks similar in shape and design http://www.diyaudio.com/forums/full-range/85410-metronome-23.html maybe it will help you in your task. 🙂
BG20 sounded good in my fake "Druid" I ran it without that tweeter (oddly a variant of Eminence's APT80) as the original Eminence B102 was the wideband in my my project. The bottom of the cabinet is "open", subjective tuning accomplished by varying the base to floor gap via spike height
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Making a quick and cheap box first is the general idea. The danger is then just stucking with an ugly box in the living room. 🙂
Yes, I've only modeled to 1000Hz, but onward from there, it's the driver, not so much the box? Am I right? And the driver is all choppy and weird in the highs. Probably will have to add a tweeter, but want to hear the dirty version first. I'm not big on crossovers.
I will need to add a BSC circuit, but will design and test it with listening tests. Someone suggested 1mH and 5-7Ohm in another thread. Will see, I've never put anything between amps and drvers before.
Thank you for your input, I will try to find some time to chew through the thread. Or at least the part that concernes bg20. The metronome is a lot higher, if I'm right, and utilizes the taper for amplification. In my model, the taper is probably just enough to reduce some of the back wall reflections.
BG20 sounded good in my fake "Druid" I ran it without that tweeter (oddly a variant of Eminence's APT80) as the original Eminence B102 was the wideband in my my project. The bottom of the cabinet is "open", subjective tuning accomplished by varying the base to floor gap via spike height
No bottom sounds like a good idea. Reduces the guesswork.
No tweeter? So just the driver and amp? Any circuit to tame the highs? I not, was it listenable? What kind of music did it like?
I got my drivers yesterday, and must say, they look like a hell of a lot of driver for 35€. I can't wait to hear them. 🙂
I think it did pretty well on Muddy Waters "Folk Singer" I had a ring of bonded Dacron between the whizzer and main cone. Its more bearable "naked" than say an Audio Nirvana 10 without a correction circuit.
graphs of de-whizzered BG20 look real good - one could roll in an appropriate tweeter around 8KHz or a bit higher.
graphs of de-whizzered BG20 look real good - one could roll in an appropriate tweeter around 8KHz or a bit higher.
Ring of bonded dacron? I'm not sure if I imagine exactly what you mean, but probably some kind of isolation? I thought about modifying the whizzer - to make a cap or modify its appearance in a way (i can 3d print almost anything - sturdy and light), so that 2k+ would be a bit less directional, and thereby not as pitchy. Makes sense or not?
I used a small strip of bonded Dacron long enough to wrap under and around the whizzer - here's a scrap on a BetsyK to illustrate. I think it tends to damp some of the junk coming off that section of the cone.
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Okay, thanks, get it. Will be something to investigate if the speakers shout too much.
What is with the surface vs. flush mounting of the driver? I think I know the theory, and in theory, flush mounting is better than surface. But then... why do some commercial speakers utilise surface mounting?
What is with the surface vs. flush mounting of the driver? I think I know the theory, and in theory, flush mounting is better than surface. But then... why do some commercial speakers utilise surface mounting?
choice of flush vs surface mounting can depend the designer's goals. Bastanis rear mount and "shades" part of the wideband speaker's surround but also flares the opening. I don't if it matters much with larger fullrange which tend to "beam" in the treble region. Planet10 could tell the subjective effects.
Since I play with Karlson type, I would even put a tweeter behind a lens - if it improves the high frequency horizontal dispersion without too many cavity resonances.
wool felt was one thing sometimes used on the front of a cabinet to reduce reflections - doesn't seem to show up much these days,
Flush vs Surface
Flush mounting tweeters
Bastanis picture
http://www.6moons.com/audioreviews/bastanis/hero2.jpg
Harry F. Olson on enclosure shapes
http://www.dwdrums.com/images/moonmic/olson_direct-radiator-loudspeaker-enclosures.pdf
Since I play with Karlson type, I would even put a tweeter behind a lens - if it improves the high frequency horizontal dispersion without too many cavity resonances.
wool felt was one thing sometimes used on the front of a cabinet to reduce reflections - doesn't seem to show up much these days,
Flush vs Surface
Flush mounting tweeters
Bastanis picture
http://www.6moons.com/audioreviews/bastanis/hero2.jpg
Harry F. Olson on enclosure shapes
http://www.dwdrums.com/images/moonmic/olson_direct-radiator-loudspeaker-enclosures.pdf
I shoebox tested the BG20 today, and compared it to a Mark Audio CHR70 in a frugelhorn.
What I found is totally expected, and I still believe that this is a turd that can be polished.
It is a lot louder than chr70. Has some powerful bass movement, I felt it with my fingers, but obviously couldn't hear it because it was in a small women's shoes box. Has a very unpleasant shout somewhere "in the delta" (folk singer reference😉). It has absolutely nothing to show in the presence and brilliance band.
What to do? My idea: remove the whizzer, leave the bg20 unfiltered, add a tweeter, filter out the LF.
What I found is totally expected, and I still believe that this is a turd that can be polished.
It is a lot louder than chr70. Has some powerful bass movement, I felt it with my fingers, but obviously couldn't hear it because it was in a small women's shoes box. Has a very unpleasant shout somewhere "in the delta" (folk singer reference😉). It has absolutely nothing to show in the presence and brilliance band.
What to do? My idea: remove the whizzer, leave the bg20 unfiltered, add a tweeter, filter out the LF.
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it should sound less hopeless when you get some bass to balance things. Then you could decide to try a filter to soften the presence area or trim/eliminate the whizzer as in some of the klang+ton projects. When the whizzer goes, you'll need to roll in a helper tweeter around 8-9KHz.
you can try putting polyfil between the whizzer and cone - don't know if that would tame what you don't like or not.
look at this thread where there's a graph of a de-whizzered BG20 - the response looks a lot like a B200
BG20 - Höhen berauben - Visaton Diskussionsforum
Here you go - a project with a proper notch filter - look at stock response vs response with the filter:
http://blogsandprojects.com/visaton-bg20-single-driver-speakers/
you can try putting polyfil between the whizzer and cone - don't know if that would tame what you don't like or not.
look at this thread where there's a graph of a de-whizzered BG20 - the response looks a lot like a B200
BG20 - Höhen berauben - Visaton Diskussionsforum
Here you go - a project with a proper notch filter - look at stock response vs response with the filter:
http://blogsandprojects.com/visaton-bg20-single-driver-speakers/
An externally hosted image should be here but it was not working when we last tested it.
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Will try them with filters, because this looks good, even though filters are a major mindfck for me. I just don't like them. They are like condoms... don't make things that much worse, but they just stay somewhere in the head, reminding of their existence.
Freddi, thanks, you are being very helpful. If you ever come to Slovenia, don't worry about beers.😉
Freddi, thanks, you are being very helpful. If you ever come to Slovenia, don't worry about beers.😉
I just realized we didn't quite understand each other in the previous posts. I said there seems to be absolutely no presence, not that it is too hot. Now I wonder - is it possible it was because the box was too small and it dampened the cone movement too much? Could it affect HF at all?
Or do I better order the tweeters right away? 😉
Or do I better order the tweeters right away? 😉
It is a german homepage but the OP made some stuff with the BG20:
boxen.html
There are some german projects using the BG20 in a 2way system.
They removed the conewhizzer and added a magnet on the back to use it more as a mid-woofer. Lautsprecherbausatz CT 230 von Klang+Ton
and a second project with a small FR as mid-high:
CT 273
and as a last project from them:
Aurum
I hope you will find some information useful and can implement something in your project 🙂
boxen.html
There are some german projects using the BG20 in a 2way system.
They removed the conewhizzer and added a magnet on the back to use it more as a mid-woofer. Lautsprecherbausatz CT 230 von Klang+Ton
and a second project with a small FR as mid-high:
CT 273
and as a last project from them:
Aurum
I hope you will find some information useful and can implement something in your project 🙂
The problem with the BG20 can be seen in the simulation tool from Visaton -> BoxSim
The speaker begins with high frequency beaming >5kHz, in an angle >5° the highs are dropping extremely.
For the money it is a nice FR to play with, especially in different enclosures (BR, BL-Horn, CB) but speaking in terms of HiFi it is only a midwoofer...
The speaker begins with high frequency beaming >5kHz, in an angle >5° the highs are dropping extremely.
For the money it is a nice FR to play with, especially in different enclosures (BR, BL-Horn, CB) but speaking in terms of HiFi it is only a midwoofer...
Meaning highs are too loud on axis, and totally dissapear off axis? Then the whizzerectomy+smaller FR or tweeter should be a serious option.
I have an extra pair of FRS8 at home which I don't like in a needle, so I could use those. The sensitivity is the same as with frs5x, which is used in a project you gave a link for.
Exactly what i'm talking about 🙂 If you are absolutely on axis fine, but some degrees off axis all heights are away. With an additional small fullrange you can create a very simple XO - 2nd order for the BG and 1st order for the FRS8. Would be a nice project with good learning process!
when BG20 was introduced into the US, its price was ~$23.50 and a very good value - now its nearly $38 - still a good value. Gradient Acoustics AX08 at ~$US60 has a more extended top end but also a higher qts to consider. A modest helper tweeter (perhaps Dynavox copy of CTS?) could work with BG20, or remove its whizzer and add the tweeter. Seems to me any 8 inch fullrange would beam sharply on its top (?)
Gradient AX08 on and about 30 degrees off in-room
Gradient AX08 on and about 30 degrees off in-room
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This all got me thinking outside of the box, and I am not sure if it can actually be done.
So the speaker goes narrow and loud when approaching highs. WHAT IF: I could somehow alter the whizzer cone so that it would beam the HF energy wider. With that, the loudness would decrease as well. I would need to do a lot of reading to do it, but it might be worth it. I could print (or have it machined from aluminium) some "device", similar to what tangband drivers have in the centre?
You may say I'm a dreamer... and all that.
So the speaker goes narrow and loud when approaching highs. WHAT IF: I could somehow alter the whizzer cone so that it would beam the HF energy wider. With that, the loudness would decrease as well. I would need to do a lot of reading to do it, but it might be worth it. I could print (or have it machined from aluminium) some "device", similar to what tangband drivers have in the centre?
You may say I'm a dreamer... and all that.
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