Hi jh,
I too had 'one of those days' yesterday and it continues today......
I really cant find anything on Overkill Audio, the one link I've found is dead
Is forum member 'Overkill Audio' one and the same?
Some of your comments / info are pretty much as I suspected.
Other bit's I have 'sorta' pondered over but lacked knowledge - now you mention length of enclosure / wavelength :/
The parable there, for me, is 2 stroke tuned pipes
As for finding the best damping scheme - ain't that always a PITA no matter the shape?
Give me a sketch / drawing / pictures and I'll see if I can come up with a way.
I've thought of making the 'whole thing' from some form of Paper + whatever mushy.
I'm going to see 'my foam man' next Tuesday for a quote and float a few things past him regarding plug construction (to keep costs down )
I too had 'one of those days' yesterday and it continues today......
I really cant find anything on Overkill Audio, the one link I've found is dead
Is forum member 'Overkill Audio' one and the same?
Some of your comments / info are pretty much as I suspected.
Other bit's I have 'sorta' pondered over but lacked knowledge - now you mention length of enclosure / wavelength :/
The parable there, for me, is 2 stroke tuned pipes
As for finding the best damping scheme - ain't that always a PITA no matter the shape?
Give me a sketch / drawing / pictures and I'll see if I can come up with a way.
I've thought of making the 'whole thing' from some form of Paper + whatever mushy.
I'm going to see 'my foam man' next Tuesday for a quote and float a few things past him regarding plug construction (to keep costs down
)Hi Danny, your 'English' is quite good indeed, and your meanings are quite clear so, 'no problems'!
Your first attempt is a lot better than mine, Danny - I started with a jigsaw and routed for cutting out the rings, glue and nails and sanded and filed each ring - used a planer on the outside and this is similar way to you - it's okay when the Crossover is above about 400Hz but not so good below that, with the 'chipboard/particle board that I used as it adde4d it's own characteristic sound to the speaker that couldn't be eliminated and this is also where I found out about the differences between a spherical, parabolic and hypex shape of the front of the chamber ad the benefit of the internal driver mounting for front 'flush edge'
My next one was worse as I tried 7 Baltic ply laminated timber sheets - that kept me out of mischief for quite some time! And it cracked, split, and everything you can imagine but it did sound much, much better so I built a vertical press like the old hand printing presses and tried again and a finished 'teardrop' shape similar to yours but 18" dia and about 24" long with soft industrial motor mounts for a suspension, and so on ....
Evening Sippy,
The 'open pipe' (a la 2 stroke motor bike exhaust idea) is quite reasonable and like these things, there's enough flexibility to adjust them a lot - if you see it as a closed pipe resonant pipe (like a 'pan pipe' for example) the standing waves length reduces to 1/4 the lowest frequency you're to reproduce, or at designed Crossover freq anyway)
So, for my 125 Hz this is about 24" long and if the density of the damping increases in a non-linear way, this can be reduced even further but runs into the problem of limiting the peak peak transients and you get that dynamic compression result that you're trying to get rid of (or I am anyway!) and this is where that low mid frequency has added to the difficulty a lot, as you can imagine.
So, the idea was to add some flexibility to the rear part of the chamber and I found at that 10mm thick paper-mache was really ridged/stiff (used the PVA glue) like fibre glass, but harder, and rang like a bell not like a softer damping material at all!
So, the next one contained damping fibre, lead shot, all sorts of 'junk' stuff but didn't change much even when I just taped this rear shape to the front half sphere with musician's 'gaffa tape' (that black fabric super stick 2" wide tape)
So I found an expert in fibre glass who loves playing with carbon fibre racing car panels that has is designing some moulds for a prototype front and rear fibre glass 'skins" and we'll add strength and limit vibrations, etc by adding the poly-concrete inside and still enable an inner sleeve to the 'tail' out of a softer paper-mache mix for a more controlled damping - the guys out here recon I'm a bit nuts about all this but with high efficiency drivers you can an amazing improvement in the increased level of transient response with much smaller power compression.
For the reduction of those nasty cone resonances I've used a partial version of the EnABL technique developed by Bud and it's also here on diyAudio and the guys in Canada are pretty clued up on all this - works like a charm.
Soon, we'll be seeing a whole series of high efficiency drivers that have little cone resonance at all and even lower distortion but still maybe at the cost of reducing the freq range like in the FAST system that I use.
Some articles are back in the AES papers some years ago and even back further (1930s!)are the designs done by the German audio industry - Carlson theory is also applicable here too and Ted Jordan did quite a bit of work on back chamber acoustical impedance (strawcell filters, etc) - the Epsilon design papers are still up on the net, I think, and contain years of development and application methods.
Their 'ball' mid chamber on top of the cylindrical 12" bass chamber was my first 'target project' in this area.
We're re-inventing the wheel again, guys! Cabasse, too - the list goes on ...
Oh yes, a mention here about matching the driver to the amp - there's a guy called Eduardo de Lima (Audiopax) that developed amplifiers based around the idea of 'variable output impedance' and is certainly worth a good look - some more on this on the Rod Elliot 'esp' site, I think.
Your first attempt is a lot better than mine, Danny - I started with a jigsaw and routed for cutting out the rings, glue and nails and sanded and filed each ring - used a planer on the outside and this is similar way to you - it's okay when the Crossover is above about 400Hz but not so good below that, with the 'chipboard/particle board that I used as it adde4d it's own characteristic sound to the speaker that couldn't be eliminated and this is also where I found out about the differences between a spherical, parabolic and hypex shape of the front of the chamber ad the benefit of the internal driver mounting for front 'flush edge'
My next one was worse as I tried 7 Baltic ply laminated timber sheets - that kept me out of mischief for quite some time! And it cracked, split, and everything you can imagine but it did sound much, much better so I built a vertical press like the old hand printing presses and tried again and a finished 'teardrop' shape similar to yours but 18" dia and about 24" long with soft industrial motor mounts for a suspension, and so on ....
Evening Sippy,
The 'open pipe' (a la 2 stroke motor bike exhaust idea) is quite reasonable and like these things, there's enough flexibility to adjust them a lot - if you see it as a closed pipe resonant pipe (like a 'pan pipe' for example) the standing waves length reduces to 1/4 the lowest frequency you're to reproduce, or at designed Crossover freq anyway)
So, for my 125 Hz this is about 24" long and if the density of the damping increases in a non-linear way, this can be reduced even further but runs into the problem of limiting the peak peak transients and you get that dynamic compression result that you're trying to get rid of (or I am anyway!) and this is where that low mid frequency has added to the difficulty a lot, as you can imagine.
So, the idea was to add some flexibility to the rear part of the chamber and I found at that 10mm thick paper-mache was really ridged/stiff (used the PVA glue) like fibre glass, but harder, and rang like a bell not like a softer damping material at all!
So, the next one contained damping fibre, lead shot, all sorts of 'junk' stuff but didn't change much even when I just taped this rear shape to the front half sphere with musician's 'gaffa tape' (that black fabric super stick 2" wide tape)
So I found an expert in fibre glass who loves playing with carbon fibre racing car panels that has is designing some moulds for a prototype front and rear fibre glass 'skins" and we'll add strength and limit vibrations, etc by adding the poly-concrete inside and still enable an inner sleeve to the 'tail' out of a softer paper-mache mix for a more controlled damping - the guys out here recon I'm a bit nuts about all this but with high efficiency drivers you can an amazing improvement in the increased level of transient response with much smaller power compression.
For the reduction of those nasty cone resonances I've used a partial version of the EnABL technique developed by Bud and it's also here on diyAudio and the guys in Canada are pretty clued up on all this - works like a charm.
Soon, we'll be seeing a whole series of high efficiency drivers that have little cone resonance at all and even lower distortion but still maybe at the cost of reducing the freq range like in the FAST system that I use.
Some articles are back in the AES papers some years ago and even back further (1930s!)are the designs done by the German audio industry - Carlson theory is also applicable here too and Ted Jordan did quite a bit of work on back chamber acoustical impedance (strawcell filters, etc) - the Epsilon design papers are still up on the net, I think, and contain years of development and application methods.
Their 'ball' mid chamber on top of the cylindrical 12" bass chamber was my first 'target project' in this area.
We're re-inventing the wheel again, guys! Cabasse, too - the list goes on ...
Oh yes, a mention here about matching the driver to the amp - there's a guy called Eduardo de Lima (Audiopax) that developed amplifiers based around the idea of 'variable output impedance' and is certainly worth a good look - some more on this on the Rod Elliot 'esp' site, I think.
Just tried WinISD Pro Alpha, runs fine on Win 7, although I could not exit the program. Everything else seemed to function.
Maybe this will help you, I'm using WinISD 0.50a7 on Win 7 Pro.
Help file runs as expected, sims work, just the close issue. Just downloaded today as I wanted something to compare with my impedance measurements.
My older WinISD files were on an older O.S. Win XP to be exact. I could add my driver, run some tests on it and checked the help function.
Help file runs as expected, sims work, just the close issue. Just downloaded today as I wanted something to compare with my impedance measurements.
My older WinISD files were on an older O.S. Win XP to be exact. I could add my driver, run some tests on it and checked the help function.
I have a photo somewhere of an early arrangement - will see about uploading it - will give you an idea about how cumbersome/crazy big the air chokes get when you passive Xover at about 120Hz!
Personal patented?
Nah! I'm just your average 'hacker guy' that's played with this sort of chamber idea for far too long!
Personal patented?
Nah! I'm just your average 'hacker guy' that's played with this sort of chamber idea for far too long!
Ok guys.Second egg fiberglassed.First one sanded down some more.Realy smooth now.
ADVICE: AT YOUR OWN RISK!!
If someone wants to do the same...don't use 450g/m2 cloth.Its too much.Id use now something lime 250-300g cloth.Too much bumps to smooth out.
Next step body filler both and then some more sanding
Danny
ADVICE: AT YOUR OWN RISK!!
If someone wants to do the same...don't use 450g/m2 cloth.Its too much.Id use now something lime 250-300g cloth.Too much bumps to smooth out.
Next step body filler both and then some more sanding
Danny
2 layers of thinner cloth might have helped. I'm just glad you're making progress
.
This is the best way round the problem.
C'mon, use your imagination and think of big gloopy sticky teardrop.
'Tis a fool-hardy man that plays with a camera while slopping cat'd resin.
I did upload a pic yesterday...cant see it now....hmmm..
Yes if id oi it again i would use two layers of thinner cloth.Might have spared me the sanding
.Anyway during next week and weekend will be more snading on the second egg.
Will be using Isopon P38 filler.ease to sand and leaves smooth finish.
Danny
Yes if id oi it again i would use two layers of thinner cloth.Might have spared me the sanding
.Anyway during next week and weekend will be more snading on the second egg.
Will be using Isopon P38 filler.ease to sand and leaves smooth finish.
Danny
Option for group buy of teardrop enclosures?
Hi fellow tear drop fans!
I have a still have my Overkill Audio mold for the "The Prey" head units, they are very high quality commercial molds. Some more images in this review 6moons audio reviews: Overkill Audio Encore Speaker System
I would be happy to make them available for a limited edition run / group buy if there is enough interest, something like 20 pairs?
If Sippy has the time he could build them, if not I have a very good (Formula 1 approved sub-contractor) contractor who can quote for the production run.
The internal volume is varies from around 20 litres (10mm wall thickness) down to approx. 10 litres depending on wall thickness and internal dampening.
I went Overkill....25mm plus / minus 10mm wall thickness with a wavy asymmetric internal finish, three different layers of Sorbothane, leather and bitumen materials plus Twaron internal stuffing....The end result was 22Kg weight (with Manger driver) and 10 litre internal volume.
I can advise and give details of how to achieve a totally inert cabinet.
We are now experimenting with a smaller teardrop enclosure (3.5 litre internal volume) for our silk surround BMR driver, this will be a commercial product so not available for DIY, but might be available for a pre-launch limited edition group buy to beta test and get customer feedback?
Let me know if you guys are interested.
Cheers
Derek.
Hi fellow tear drop fans!
I have a still have my Overkill Audio mold for the "The Prey" head units, they are very high quality commercial molds. Some more images in this review 6moons audio reviews: Overkill Audio Encore Speaker System
I would be happy to make them available for a limited edition run / group buy if there is enough interest, something like 20 pairs?
If Sippy has the time he could build them, if not I have a very good (Formula 1 approved sub-contractor) contractor who can quote for the production run.
The internal volume is varies from around 20 litres (10mm wall thickness) down to approx. 10 litres depending on wall thickness and internal dampening.
I went Overkill....25mm plus / minus 10mm wall thickness with a wavy asymmetric internal finish, three different layers of Sorbothane, leather and bitumen materials plus Twaron internal stuffing....The end result was 22Kg weight (with Manger driver) and 10 litre internal volume.
I can advise and give details of how to achieve a totally inert cabinet.
We are now experimenting with a smaller teardrop enclosure (3.5 litre internal volume) for our silk surround BMR driver, this will be a commercial product so not available for DIY, but might be available for a pre-launch limited edition group buy to beta test and get customer feedback?
Let me know if you guys are interested.
Cheers
Derek.
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Hi Derek, that is a generous offer, thank you but...
I'm afraid that my whole budget for the build is probably less then the paint on those beautiful egg units of yours I could simply not afford any even if I wanted too much.
But I hope some guys will jump on the offer and buy the units to experiment with ar build their own interpretation of your design...
Danny
P.S.: I'd like to visit some UK audiophile gathering and meet you there...
I'm afraid that my whole budget for the build is probably less then the paint on those beautiful egg units of yours
I could simply not afford any even if I wanted too much.But I hope some guys will jump on the offer and buy the units to experiment with ar build their own interpretation of your design...
Danny
P.S.: I'd like to visit some UK audiophile gathering and meet you there...
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