Phergus_25 said:
Thanks. By the looks of it I'll have to wing it too. For example the second internal deflector (part "7" in the drawings) is smth like 2.5 in short if the headroom to the top of the speaker (i.e. distance to the part 8 in the drawing to be more exact) is to be 4.12 in (105 mm).
Anyway, will post the 1:1 scale drawing as soon as I'm done with it.
Thanks,
Florian
CC volume
As promised, here comes the first picture of the drawing. I started an album at: http://picasaweb.google.com/florian.otel/A126HornBuildingPictures
Profile is drawn at 1:1 scale (noted dimensions in mm). Ply is 18 mm thick.
The CC:
(for a clear/full scale pic plus several pics of the same CC see the album link above)
While the dimensions match the ones listed pages 3--5 in the PDF (except some odd millimiters in the vertical dimensions on page 4), the area of this CC profile adds up to 111.775 cm^2. For a 15.5 cm wide front baffle the CC volume becomes 1.732 liters, quite a bit less than the recommended 2.2 liters.
Ideas ? Am I missing smth ? Greg, how did you get yours to be 2.2 liters ?
Florian
As promised, here comes the first picture of the drawing. I started an album at: http://picasaweb.google.com/florian.otel/A126HornBuildingPictures
Profile is drawn at 1:1 scale (noted dimensions in mm). Ply is 18 mm thick.
The CC:
An externally hosted image should be here but it was not working when we last tested it.
(for a clear/full scale pic plus several pics of the same CC see the album link above)
While the dimensions match the ones listed pages 3--5 in the PDF (except some odd millimiters in the vertical dimensions on page 4), the area of this CC profile adds up to 111.775 cm^2. For a 15.5 cm wide front baffle the CC volume becomes 1.732 liters, quite a bit less than the recommended 2.2 liters.
Ideas ? Am I missing smth ? Greg, how did you get yours to be 2.2 liters ?
Florian
Well my method was pretty barbaric, which could haev lead to some error, but I wouldent have throught it would be half a liter of error.
I took a bag when I had my speakers half done and put it inside the CC and filled it with water untill it was full. Once it was I took the bad of water and measured it. It filler a one liter container over twice.
Sorr that my method dosent lend its self to being too scientific
I took a bag when I had my speakers half done and put it inside the CC and filled it with water untill it was full. Once it was I took the bad of water and measured it. It filler a one liter container over twice.
Sorr that my method dosent lend its self to being too scientific
Your method might actually have been more accurate then my measuring. However it might be, an error of 0.5 liters is quite a lot, so it must be smth else ...
Anybody, any ideas ?
TIA,
Florian
Anybody, any ideas ?
TIA,
Florian
while i think the bag of water is quite good you could measure / calculate the volume in e.g. cubic centimetres and then convert to litres.
Re: CC volume
The only drawing that may have the correct CC is the jpg on page 2 (?) with the supraBaffle (nope is is at 1,84 litres).
What Chris & i did was extend the top, open up the back, and then fill the CC with irregular stuff (including wavy wood) to bring it down to size). The expanded chamber is ~2.57 litres,
dave
FlorianO said:
The only drawing that may have the correct CC is the jpg on page 2 (?) with the supraBaffle (nope is is at 1,84 litres).
What Chris & i did was extend the top, open up the back, and then fill the CC with irregular stuff (including wavy wood) to bring it down to size). The expanded chamber is ~2.57 litres,
dave
Attachments
In the 3D visualization i just used the 1.8x litre chamber -- you can see the added void behind which gives room to expand (and to my mind cleans up the look of the top of the horn).
Perhaps Ron will comment.
dave
PS: sorry fpr the big pic -- it was handy)
Perhaps Ron will comment.
dave
PS: sorry fpr the big pic -- it was handy)
If you construct a too-small chamber you can always bulild a thicker suprabaffle and use the added space to expand the chamber forward. An extra 18mm sheet with a 15.5*15.5cm cut-out gets you .432 liters bringing you up to ~2.15liters. Chamfering the driver hole should get you the rest.
Sean
Sean
well I suppose my measuring was off that much. So what is the diff in the smaller CC size? Im veryhappy with the sound im getting and prob wont rip into them. but I could see adding a thick piece of wood and a thick SB to give it some more air.
-greg
-greg
Some like it some dont . Adding a 1.4" T( 2 layers of .7") x 12.7" W baffle will allow a lower roll off of the horn action and a more IB type response from approx 260hz on up which can give vocals a bit more relastic sound. The bevels on the SB and trailing edges are just for less diffraction.
This is what i found in my studies on CC volume in BLHs.
The most natural occuring sound is produced in IBs and OBs with regards to the driver performance. The reason is no or minimul loading so the designed in electromechanical action will not be affected. But for proper LF response you have to load at lower frequencies. The trick is to design in a point or point on intersecting curves that allow the unloading at a given frequency which will produce vocal ranges in an un loaded manner. The smaller the CC the higher frequency the horn action and the higher the unloading point. Now you have to consider that very little radical changes occurs at a point on a given FR curve as its more a roll in and roll off over a range of frequencies of the horn action as well as the unloding range which is a curve on the FR. When the unloading occurs in too high a range some find the sound compressed.
ron
ron
This is what i found in my studies on CC volume in BLHs.
The most natural occuring sound is produced in IBs and OBs with regards to the driver performance. The reason is no or minimul loading so the designed in electromechanical action will not be affected. But for proper LF response you have to load at lower frequencies. The trick is to design in a point or point on intersecting curves that allow the unloading at a given frequency which will produce vocal ranges in an un loaded manner. The smaller the CC the higher frequency the horn action and the higher the unloading point. Now you have to consider that very little radical changes occurs at a point on a given FR curve as its more a roll in and roll off over a range of frequencies of the horn action as well as the unloding range which is a curve on the FR. When the unloading occurs in too high a range some find the sound compressed.
ron
ron
well maby i just like the coloration, but I LOVE these things. Much more than my Audio-technica W5000s [$700 pair f headphones]
Part 2 of the above:
Another factor is cone control in the loading/unloading curves. I am a big believer in cone control as if there is a lesser loading at low frequencies the cone movement gets excessive and affects the higher frequencies as cone position will be altered when a higher frequency sine wave is introduced. This is most evident at higher volumes as the cone displacement has to compensate for less loading of the horn action.
One major advantage of smaller drivers is less breakup over a given frequency range that larger area cones. This can be cured by stiffer cone materials, but if that entails a denser material then you are moving more mass. Its either that or a good structural support design of the cone like in the Fostex Sigma series.
The sum total is its all a balance of trade offs. Properly balanced you can achieve a reasonable efficency with somewhat of a linear FR curve.
ron
Another factor is cone control in the loading/unloading curves. I am a big believer in cone control as if there is a lesser loading at low frequencies the cone movement gets excessive and affects the higher frequencies as cone position will be altered when a higher frequency sine wave is introduced. This is most evident at higher volumes as the cone displacement has to compensate for less loading of the horn action.
One major advantage of smaller drivers is less breakup over a given frequency range that larger area cones. This can be cured by stiffer cone materials, but if that entails a denser material then you are moving more mass. Its either that or a good structural support design of the cone like in the Fostex Sigma series.
The sum total is its all a balance of trade offs. Properly balanced you can achieve a reasonable efficency with somewhat of a linear FR curve.
ron
Re: Re: CC volume
Dave,
Thanks for chipping in. Comforting to know I didn't screw up (very high probability for that).
Wrt increasing the volume of the CC I was thinking along the same lines as in your picture. It will both give me the cosmetics and the added volume (and maybe a side effect in improved cabinet bracing ?)
OTOH I can very well go for the SB and get the added volume that way.
Or maybe lee' bit of both 🙂
Ron, thanks for commenting on the CC volume, highly appreciated.
Florian
planet10 said:
Dave,
Thanks for chipping in. Comforting to know I didn't screw up (very high probability for that).
Wrt increasing the volume of the CC I was thinking along the same lines as in your picture. It will both give me the cosmetics and the added volume (and maybe a side effect in improved cabinet bracing ?)
OTOH I can very well go for the SB and get the added volume that way.
Or maybe lee' bit of both 🙂
Ron, thanks for commenting on the CC volume, highly appreciated.
Florian
On the calculation of the CC of the A126 vrs the A166.
I designed the A166 first. I was in the process of changing the programming for the Austin principal. On the A166 i actually used a slide rule for calculation (present from Dad ,he used it in his college days, i used it in HS) instead of a si fi calculator or program.(added note, i guess true old time geeks belonged to the slide rule club,science club, physics club ect ect.)
Now to all of you youngins out there a skide rule just gets close in exacting values and never hits dead on. That combined with actual hand drawn scale dwgs (later converted to CAD) actually produced a better end result. Computer programs can have errors.
Now i am a techo nut and work in a higher field of technology, but when i finish with a hand dwg and have crunched the numbers by hand i have a greater amount of pride in the finished product and there is a given amount of art (as close as i will ever get to art anyway).
The old methods are not as fast or exacting as the new technology and i find that the young engineers are little more than button pushers who really dont have to think.
Maybe something is missing?
ron
I designed the A166 first. I was in the process of changing the programming for the Austin principal. On the A166 i actually used a slide rule for calculation (present from Dad ,he used it in his college days, i used it in HS) instead of a si fi calculator or program.(added note, i guess true old time geeks belonged to the slide rule club,science club, physics club ect ect.)
Now to all of you youngins out there a skide rule just gets close in exacting values and never hits dead on. That combined with actual hand drawn scale dwgs (later converted to CAD) actually produced a better end result. Computer programs can have errors.
Now i am a techo nut and work in a higher field of technology, but when i finish with a hand dwg and have crunched the numbers by hand i have a greater amount of pride in the finished product and there is a given amount of art (as close as i will ever get to art anyway).
The old methods are not as fast or exacting as the new technology and i find that the young engineers are little more than button pushers who really dont have to think.
Maybe something is missing?
ron
Very possible Ron. I'm 28, and come from a generation for whom the government of the time decided didn't need to be taught math, physics, art, English literature, history, or much of anything else to be honest. This does not please me, as I've spent the last decade since leaving school, in addition to going through university etc., trying to compensate for the gaps. Time I could have better spent building on what I should have had in the first place.
Oddly enough I actually own a slide-rule. I bought it a couple of years ago. It's in front of me now, on the desk. I confess I don't use it very much (probably should use it more), but it's there, and it's not just an ornament.
Oddly enough I actually own a slide-rule. I bought it a couple of years ago. It's in front of me now, on the desk. I confess I don't use it very much (probably should use it more), but it's there, and it's not just an ornament.
Though I confess to never having used a slide rule for critical calculations, they were incredibly useful as a pedagogical tool.
When I taught math, I often tried to bring out the slide rule for instruction on logs. After seeing on, andx using it for simple tasks, kids got logs and the log rules, quickly.
Sean
When I taught math, I often tried to bring out the slide rule for instruction on logs. After seeing on, andx using it for simple tasks, kids got logs and the log rules, quickly.
Sean
Well ron, I am old enough to actually have used a slide rule but was young enough to embrace computers wholeheartedly quickly after. Still, I was very fortunate to be literally hammered with maths and "absolutely no slide rules, tables, or electronic devices" during hours and hours of maths and physics classes.
That is why I actually have recomputed all the dimensions around the CC (and its volume) using pen, paper and basic geometry 🙂. Faster than learning some new CAD program -- and more exact 🙂. While posting the resluting dimensions with 0.001 mm precision is of limited practical use (to say the least) some number freaks newbies like me might take confort in that someone did double-checked the numbers 🙂
To sum it up: My current idea is along Dave's suggestion: Slide backwards the top part of the CC _and_ add the SB consisiting of one or two 18 mm (.7 in) plywood layers while keeping the hole in the front baffle to flush fit the driver (in order to experiment both w or w/o the SB).
One more uneducated question: Did I understand it correctly that filling a (slighly) oversized CC with corugated stuff like egg cartons / polyfill / profiled absorber "sponge" is equivalent to reducing its volume ? The reason I'm asking is compensating for the extra volume when e..g. adding a dobule-layered SB.
I wil try to post the computed metric dimensions of the CC, areas and volumes as soon as I can get a decent drawing of the lot -- haven't learned Google sketchup yet, and haven't used any CAD in decades...
Rgrds,
Florian
That is why I actually have recomputed all the dimensions around the CC (and its volume) using pen, paper and basic geometry 🙂. Faster than learning some new CAD program -- and more exact 🙂. While posting the resluting dimensions with 0.001 mm precision is of limited practical use (to say the least) some number freaks newbies like me might take confort in that someone did double-checked the numbers 🙂
To sum it up: My current idea is along Dave's suggestion: Slide backwards the top part of the CC _and_ add the SB consisiting of one or two 18 mm (.7 in) plywood layers while keeping the hole in the front baffle to flush fit the driver (in order to experiment both w or w/o the SB).
One more uneducated question: Did I understand it correctly that filling a (slighly) oversized CC with corugated stuff like egg cartons / polyfill / profiled absorber "sponge" is equivalent to reducing its volume ? The reason I'm asking is compensating for the extra volume when e..g. adding a dobule-layered SB.
I wil try to post the computed metric dimensions of the CC, areas and volumes as soon as I can get a decent drawing of the lot -- haven't learned Google sketchup yet, and haven't used any CAD in decades...
Rgrds,
Florian
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