Been reading through this thread and decided to have a go.
this is for a very small, like 6sq Meter-study and replacing PC-desktop speakers.
Is Faital Pro 3FE22 3" speakers a good choice to put in a 50 x 50cm Cornu? (20" x 20"), thinking like 7cm (2,75") for the inner walls..
Will this sound good? Want a real fast and rapid response and some bass would be nice, without overtaking the small room..
Think I'll use 4mm LitePLY (Birch) (or perhaps 8mm regular Birch PLY, depending on whats at store) and Softcore of 5mm for the channels which I already have.
Can also go and source Peerless TG9FD or Dayton Audio PS95-8, Dayton Audio DMA90-4, Dayton Audio DMA80-4 (or Faital Pro 3Fe25) - would any of these be any better?
this is for a very small, like 6sq Meter-study and replacing PC-desktop speakers.
Is Faital Pro 3FE22 3" speakers a good choice to put in a 50 x 50cm Cornu? (20" x 20"), thinking like 7cm (2,75") for the inner walls..
Will this sound good? Want a real fast and rapid response and some bass would be nice, without overtaking the small room..
Think I'll use 4mm LitePLY (Birch) (or perhaps 8mm regular Birch PLY, depending on whats at store) and Softcore of 5mm for the channels which I already have.
Can also go and source Peerless TG9FD or Dayton Audio PS95-8, Dayton Audio DMA90-4, Dayton Audio DMA80-4 (or Faital Pro 3Fe25) - would any of these be any better?
Any of the above drivers are good and use between 20x20in to 24in x24in. Depth from 2.5in to 3.5in. It’s quite forgiving and adjust with stuffing to taste. The 3FE25-8 is an especially great driver with balance, smooth response, and nice highs. 3FE22 has more powerful motor ideally suited for horn loading. However, I think 3FE25 would work just fine and save some $.
I have read about half of the thread and have a pretty good understanding of some of the general rules of thumb around relationships between driver, throat, and baffle sizes.
There are lots of tried and true combinations that I could easily copy but where is the fun in that. So I am thinking of using a 4" SBacoustic coax with and active crossover to try something a bit different. I was leaning towards a 24x24" baffle size but am still on the fence about depth. The general rule of thumb would suggest a thickness around 4"-4.5" but the driver being used has a low QTS (0.33) which I believe is suitable for a bit more compression. I like the idea of a thinner enclosure, maybe 2.5"-3", but I am unsure if that is pushing it too far.
Would anyone be able to model this for me? I don't have any experience with the horn modeling software.
4″ SB12PFCR25-4-COAX – Sbacoustics
There are lots of tried and true combinations that I could easily copy but where is the fun in that. So I am thinking of using a 4" SBacoustic coax with and active crossover to try something a bit different. I was leaning towards a 24x24" baffle size but am still on the fence about depth. The general rule of thumb would suggest a thickness around 4"-4.5" but the driver being used has a low QTS (0.33) which I believe is suitable for a bit more compression. I like the idea of a thinner enclosure, maybe 2.5"-3", but I am unsure if that is pushing it too far.
Would anyone be able to model this for me? I don't have any experience with the horn modeling software.
4″ SB12PFCR25-4-COAX – Sbacoustics
Code:
Nominal Impedance 4 Ω
DC resistance, Re 3.1 Ω
Voice coil inductance, Le 0.26 mH
Effective piston area, Sd 45 cm2
Voice coil diameter 25.4 mm
Voice coil height 15 mm
Air gap height 5 mm
Linear coil travel (p-p) 10 mm
Magnetic flux density 1.0 T
Magnet weight 0.40 kg
Net weight 0.86 kg
Free air resonance, Fs 58 Hz
Sensitivity (2.83V/1m) 87 dB
Mechanical Q-factor, Qms 4.07
Electrical Q-factor, Qes 0.36
Total Q-factor, Qts 0.33
Moving mass incl. air,Mms 4.5 g
Force factor, Bl 3.8 Tm
Equivalent volume, Vas 4.8 liters
Compliance, Cms 1.66 mm/N
Mechanical loss, Rms 0.4 kg/s
Rated power handling* 30 W
I gave the cornu horn an initial attempt will I wait for my supplies ship. I had some old Logitech speakers with 3" drivers kicking around so I decided to do a 24"x3" enclosure with 1/4" MDF and foamcore.
Are there any construction tips for ensuring the front baffle is fully sealed? I was able to hot glue the foam core channels with pretty good success but attacting the front baffle was just rolling the dice. I went with the expanding Gorrila glue to attach the front baffle and placed lots of weight on it when it dried. I'm not confident that the channels made a good seal though.
I did my best to ensure that all the foamcore channels were the same height by using a steel ruler and sharp utility blade to cut them.
For my next attempt, I am thinking of using MDF for the channels too with kerfs for the bends. At least this way I can hope to get a consistent channel height by running it all through the table saw at the same time.
Are there any construction tips for ensuring the front baffle is fully sealed? I was able to hot glue the foam core channels with pretty good success but attacting the front baffle was just rolling the dice. I went with the expanding Gorrila glue to attach the front baffle and placed lots of weight on it when it dried. I'm not confident that the channels made a good seal though.
I did my best to ensure that all the foamcore channels were the same height by using a steel ruler and sharp utility blade to cut them.
For my next attempt, I am thinking of using MDF for the channels too with kerfs for the bends. At least this way I can hope to get a consistent channel height by running it all through the table saw at the same time.
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For standard height and faster build, what about this
I bought a roll of this for when I decide to build a Cornu since it has the advantage: 1. standard height, 2. Flexible without kerfing, 3. Because a rougher surface than Foam-core, it will attenuate more of the HF, 4. faster build 5. more top/bottom surface area for glue.
Concrete 4" high divider at HD Big Box store. about .35$ a foot.
But maybe a problem with the rougher surface? What do you think?
I bought a roll of this for when I decide to build a Cornu since it has the advantage: 1. standard height, 2. Flexible without kerfing, 3. Because a rougher surface than Foam-core, it will attenuate more of the HF, 4. faster build 5. more top/bottom surface area for glue.
Concrete 4" high divider at HD Big Box store. about .35$ a foot.
But maybe a problem with the rougher surface? What do you think?
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That's interesting. I was thinking of doing something similar but couldn't find the right material that was cost effective. There were some rubber options but the cost was too high. I think it could work granted there is enough rigidity to it and it doesn't buckle. I think just by the nature of the design and the fact that channels extent in every direction you should be ok. Try it and let us know.
When I was concerned about full contact, what I did was to lay a bead of Carpenter's PVA on the foam edge and loosely lay into that 1 cm strips of ordinary paper. That created a shelf to add another layer of PVA before placing the baffle.
Far more inexpensive and way more effective than using weatherstripping.
Far more inexpensive and way more effective than using weatherstripping.
Because you have been diligent about your reading but not done all, this might help. I laid the paper over the foam core after adding glue to the edges.
A homemade jig can help you get the cutting right.
In this pic, I found it easier to overlay the glue with paper and cut out the 1 cm shelves easier. Make sure you do the entire process one speaker at a time to ensure the glue is still pliable.
A homemade jig can help you get the cutting right.
In this pic, I found it easier to overlay the glue with paper and cut out the 1 cm shelves easier. Make sure you do the entire process one speaker at a time to ensure the glue is still pliable.
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Ready to start my first Cornu (TC9FD18 based 20"-ish by 3"-ish)
Thinking about various improvements mentioned in past 2797 posts... One, on increasing cavity area to improve mid range, didn't seem to get much traction. Back in Feb 2014 when Mr X broached the idea Don Hills in post 1308 suggested "If building from scratch, just make it a bit bigger. Maintain the same path lengths, and make the central chamber larger diameter." but there didn't seem to be any further comments or suggestions on that suggestion.
Simple maths suggests that doubling the cavity diameter gives around 4x the volume.
I took a quick look at the Cornu Spiral PDF and by cutting it into quarter segments and moving those quarters apart to create a bigger cavity space and reconnecting the spirals. It seems the cavity gets bigger while the throats stay the same and the length increases a bit. All seem good. For my Plywood fronts and back blanks I can increase the cavity diameter by about 90mm without any trouble (20" to 23.5") which roughly increase the cavity volume by ~5x but adds around 600mm to horn length. The horn length could be reduced a bit by "unwinding the spiral" if necessary.
What am I missing?
DonJ
(BTW - What a great thread, inspirational and with true leaders)
Thinking about various improvements mentioned in past 2797 posts... One, on increasing cavity area to improve mid range, didn't seem to get much traction. Back in Feb 2014 when Mr X broached the idea Don Hills in post 1308 suggested "If building from scratch, just make it a bit bigger. Maintain the same path lengths, and make the central chamber larger diameter." but there didn't seem to be any further comments or suggestions on that suggestion.
Simple maths suggests that doubling the cavity diameter gives around 4x the volume.
I took a quick look at the Cornu Spiral PDF and by cutting it into quarter segments and moving those quarters apart to create a bigger cavity space and reconnecting the spirals. It seems the cavity gets bigger while the throats stay the same and the length increases a bit. All seem good. For my Plywood fronts and back blanks I can increase the cavity diameter by about 90mm without any trouble (20" to 23.5") which roughly increase the cavity volume by ~5x but adds around 600mm to horn length. The horn length could be reduced a bit by "unwinding the spiral" if necessary.
What am I missing?
DonJ
(BTW - What a great thread, inspirational and with true leaders)