Hi -
I'm finally building my 'ultimate' audio speakers, where I plan to use two K145/E145 cone woofers per channel. I am also planning to use the coconut shell charcoal box compliance enhancement approach (supposedly can be at least doubled by this approach) which models out to give about 32 hz response in a 10cu ft closed box (no ports!) with the correctly sized DC blocking input capacitor, but I realize that the cones of the two woofers would probably be the main ingress for external atmospheric moisture which would significantly degrade the compliance enhancement far earlier than needed. I will add a scheme to make it easy to replace the desiccant when that happens, though.
So what I am looking for is a minimum mass material I can apply to the cones to prevent external moisture to travel through them (and make them impervious to humidity changes, also). I want to keep the total mass added per cone no more than 2 grams, and would like it to add a bit of damping also if possible, since it would need to be there to block water vapor.
The E145 cones are very low mass, with a Mms of only 55 grams and I want to keep their actual mass as low as possible, so any black shiny goop which would add dozens of grams is out. There is only a need for a surface layer if it can provide a moisture proof barrier - the back of the cone will be kept at probably less than 10% RH with a powerful desiccant.
It's interesting that literature says that bulk paper such as speaker cones are made out of have about a 6-7% increase in mass due to water under normal atmospheric conditions. If I can add a light vapor barrier to the outside of the cone, it seems I could cancel its weight increase due to removal of the moisture through the rest of the cone with this desiccant.
I am a bit leery of standard moisture barrier sprays such as acrylic since they may not work so well acoustically, especially wrt damping and that I might need to add too much weight wise.
Anybody have suggestions as to what might be the best moisture barrier material?
I'm finally building my 'ultimate' audio speakers, where I plan to use two K145/E145 cone woofers per channel. I am also planning to use the coconut shell charcoal box compliance enhancement approach (supposedly can be at least doubled by this approach) which models out to give about 32 hz response in a 10cu ft closed box (no ports!) with the correctly sized DC blocking input capacitor, but I realize that the cones of the two woofers would probably be the main ingress for external atmospheric moisture which would significantly degrade the compliance enhancement far earlier than needed. I will add a scheme to make it easy to replace the desiccant when that happens, though.
So what I am looking for is a minimum mass material I can apply to the cones to prevent external moisture to travel through them (and make them impervious to humidity changes, also). I want to keep the total mass added per cone no more than 2 grams, and would like it to add a bit of damping also if possible, since it would need to be there to block water vapor.
The E145 cones are very low mass, with a Mms of only 55 grams and I want to keep their actual mass as low as possible, so any black shiny goop which would add dozens of grams is out. There is only a need for a surface layer if it can provide a moisture proof barrier - the back of the cone will be kept at probably less than 10% RH with a powerful desiccant.
It's interesting that literature says that bulk paper such as speaker cones are made out of have about a 6-7% increase in mass due to water under normal atmospheric conditions. If I can add a light vapor barrier to the outside of the cone, it seems I could cancel its weight increase due to removal of the moisture through the rest of the cone with this desiccant.
I am a bit leery of standard moisture barrier sprays such as acrylic since they may not work so well acoustically, especially wrt damping and that I might need to add too much weight wise.
Anybody have suggestions as to what might be the best moisture barrier material?
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I don't have experience in this area and don't know the best, but here r some links for clear or black wet coating and some coating after a repair service of unknown origin.
Thanks for the input. I'm looking at butyl rubber sealants at the moment.
It's interesting, but a lot of coatings that provide water proofing because of surface tension effects will still let water vapor through, which I don't want. Supposedly butyl rubber is both water and gas vapor impermeable and stays flexible. So far, it seems to be available mostly in brush or caulk form. If I can thin it out enough, I might be able to paint a light coating onto a speaker cone.
Another thing is I want to stay away from water based coatings which could wet and damage the cone.
It's interesting, but a lot of coatings that provide water proofing because of surface tension effects will still let water vapor through, which I don't want. Supposedly butyl rubber is both water and gas vapor impermeable and stays flexible. So far, it seems to be available mostly in brush or caulk form. If I can thin it out enough, I might be able to paint a light coating onto a speaker cone.
Another thing is I want to stay away from water based coatings which could wet and damage the cone.
Weird concerns.. Do you live in a 100% humidity area?
Beyond mass concerns, Adding goop/doping the cones.. be it it with Laquer or PVA or one of those horrid black "cone paint' concoctions.
You WILL alter the sounds of the driver. Likely not for the better.
IF goops enhanced.. then all major driver makers would at least offer it as an option.
That said; Plastic cones are waterproof.. sound crappy imo, but waterproof nonetheless.
Beyond mass concerns, Adding goop/doping the cones.. be it it with Laquer or PVA or one of those horrid black "cone paint' concoctions.
You WILL alter the sounds of the driver. Likely not for the better.
IF goops enhanced.. then all major driver makers would at least offer it as an option.
That said; Plastic cones are waterproof.. sound crappy imo, but waterproof nonetheless.
I have used silicone spray many times to waterproof paper cone drivers, use the one that is suitable for waterproofing maps etc. and rather than spaying it direct on the cone, spray it into the lid of the spray can and let some of the solvent evaporate and then apply it with a brush, you can probably get it from outdoor or sailing outlets or online, or you can use some of the off the shelf treatments that you can get from the speaker outlets like parts express, but they might add too much mass.
Hi-
Normal humidity, but I want to create a very low humidity situation inside the enclosure (< ~ 25%) to allow the coconut shell charcoal to work best to increase the enclosure compliance. I plan to use a desiccant from CRL Laboratories meant to keep window module internal humidities low to prevent condensing, to reduce the cabinet RH and prevent the charcoal from adsorbing water which it would rather do than air molecules.
I plan to add an arrangement to be able to fairly easily change out the desiccant on a regular basis - being able to keep water vapor out might mean I would need to do that only once every couple of years.
As you mentioned, I am a bit concerned about possible negative audible effects of adding a compound to the cones - I might try adding the compound to a test driver first just to make sure nothing bad happens. A little loss above 1khz wouldn't be a problem, since I plan to xover ~ 450 hz. I figure that if I add 2 grams or less of this material per speaker, that it won't affect the cone mass significantly.
Silicone spray is great for keeping liquid water off the cone, but will not stop gasses (including water vapor) from passing through it to a great extent, from what I've read.
Normal humidity, but I want to create a very low humidity situation inside the enclosure (< ~ 25%) to allow the coconut shell charcoal to work best to increase the enclosure compliance. I plan to use a desiccant from CRL Laboratories meant to keep window module internal humidities low to prevent condensing, to reduce the cabinet RH and prevent the charcoal from adsorbing water which it would rather do than air molecules.
I plan to add an arrangement to be able to fairly easily change out the desiccant on a regular basis - being able to keep water vapor out might mean I would need to do that only once every couple of years.
As you mentioned, I am a bit concerned about possible negative audible effects of adding a compound to the cones - I might try adding the compound to a test driver first just to make sure nothing bad happens. A little loss above 1khz wouldn't be a problem, since I plan to xover ~ 450 hz. I figure that if I add 2 grams or less of this material per speaker, that it won't affect the cone mass significantly.
Silicone spray is great for keeping liquid water off the cone, but will not stop gasses (including water vapor) from passing through it to a great extent, from what I've read.
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Try some cheap hairspray (test first on paper). Woodworkers use this to seal and stop chipout on soft timbers.
Cheers G.
Cheers G.
The other technically advanced idea I can remember was a continuous rubber membrane from (Dunlop or Michelin, I can't remember) applied to the roof, a friend used in the construction of his house.
What's the point of building a different cone if you have to alter/treat it changing it's fundamental conditions and behavior/characteristics. Better if you start with the material (like PP) that you need to be waterproof.
As another note, you can use liquid glass the only material that is waterproof, that I know of. I don't know about vapor (the gases form you want to prevent also). Usually the materials (not rubber) used in garments are pervious to perspiration or "waterproof breathable fabric" usually water repellent and water vapor permeable. link
What's the point of building a different cone if you have to alter/treat it changing it's fundamental conditions and behavior/characteristics. Better if you start with the material (like PP) that you need to be waterproof.
As another note, you can use liquid glass the only material that is waterproof, that I know of. I don't know about vapor (the gases form you want to prevent also). Usually the materials (not rubber) used in garments are pervious to perspiration or "waterproof breathable fabric" usually water repellent and water vapor permeable. link
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At least one KEF study found online had them maintain the performance of a 8.6L box in a 5L box with 2.2L of ACE charcoal introduced. Does this mean you'll need to get your hands on ~124L of charcoal per box?
http://francis.audio2.pagesperso-orange.fr/acewp.pdf
Personally, I'd stick with polyfill/Acousta-stuff to yield a ~25% increase in apparent Vb without much of the hassle ACE, especially scaled-up to 10cu.f boxes, would seem to entail.
http://francis.audio2.pagesperso-orange.fr/acewp.pdf
Personally, I'd stick with polyfill/Acousta-stuff to yield a ~25% increase in apparent Vb without much of the hassle ACE, especially scaled-up to 10cu.f boxes, would seem to entail.
I probably have about 100L of coconut charcoal per box. I was able to buy from a wholesaler for about $190 US enough for two speakers. Also, I will use some sort of poly fill for much of the remaining volume (primarily to damp reflections) so I expect to approach the compliance of a 20 cu ft box.
KEF in their paper doesn't make it totally clear how much humidity deteriorates compliance, or at what RH their compliance enhancement chart is taken, but another of their charts show roughly five times the water adsorbed at a RH of 50% and above compared to 25%, and I am hoping to achieve the lower figure. I bought a 5lb can of CRL molecular sieve desiccant which reportedly tends to hold RHs to the 10% range until it is saturated. I plan to set it up so that about 1lb can be installed in each speaker through a couple of ports in the rear panel. Open the lower port to let the old stuff out, close it and then open the upper port to add the new stuff, then close it.
Activated charcoal is fairly messy stuff to handle while being installed, but once it's in place, it merely adds some weight to the speaker. For my application, the difference between 18 cu ft and 9 cu ft would be a fairly dramatic reduction in the size of the cabinet - for instance, with 1" Baltic Birch Plywood, this would translate into a roughly 50" tall x 18" wide x 22" deep enclosure which is a decent size in my environment for a floor mount enclosure with two 15" woofers and a MID/HF horn - twice that volume could increase each dimension by 25%, and the extra weight in plywood needed for the larger cabinet might make up for the weight of the coconut charcoal in the smaller cabinet. Plus, there would be more bracing issues to deal with in the larger enclosure.
KEF in their paper doesn't make it totally clear how much humidity deteriorates compliance, or at what RH their compliance enhancement chart is taken, but another of their charts show roughly five times the water adsorbed at a RH of 50% and above compared to 25%, and I am hoping to achieve the lower figure. I bought a 5lb can of CRL molecular sieve desiccant which reportedly tends to hold RHs to the 10% range until it is saturated. I plan to set it up so that about 1lb can be installed in each speaker through a couple of ports in the rear panel. Open the lower port to let the old stuff out, close it and then open the upper port to add the new stuff, then close it.
Activated charcoal is fairly messy stuff to handle while being installed, but once it's in place, it merely adds some weight to the speaker. For my application, the difference between 18 cu ft and 9 cu ft would be a fairly dramatic reduction in the size of the cabinet - for instance, with 1" Baltic Birch Plywood, this would translate into a roughly 50" tall x 18" wide x 22" deep enclosure which is a decent size in my environment for a floor mount enclosure with two 15" woofers and a MID/HF horn - twice that volume could increase each dimension by 25%, and the extra weight in plywood needed for the larger cabinet might make up for the weight of the coconut charcoal in the smaller cabinet. Plus, there would be more bracing issues to deal with in the larger enclosure.
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I expect activated charcoal is special stuff, but didn't Thiele or Small prove you can only increase effective volume by 30% or so in a cabinet with all the stuffing in the world. Because after a certain point too much stuffing reduces the volume.
I'm probably missing something here though. 😀
I'm probably missing something here though. 😀
Hi,
Taking a 2001 white paper seriously is asking for trouble,
especially a very lightweight 7 page indulgence (IMO),
that has never seen the commercial light of day.
There is nothing good about about low mass bass drivers
other then high efficiency, with limited bass in big boxes.
rgds, sreten.
Adsorption of gas is the issue S7 is missing. I suspect
the moisture level required to make it work is too
low to be ever sensibly practical in a loudspeaker.
Taking a 2001 white paper seriously is asking for trouble,
especially a very lightweight 7 page indulgence (IMO),
that has never seen the commercial light of day.
There is nothing good about about low mass bass drivers
other then high efficiency, with limited bass in big boxes.
rgds, sreten.
Adsorption of gas is the issue S7 is missing. I suspect
the moisture level required to make it work is too
low to be ever sensibly practical in a loudspeaker.
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KEF is marketing speakers today using ACE, so they must see enough return on the technique to continue using it.
Also, I have a Basta! simulation of the 20cu ft sealed enclosure with two E145 equivalent drivers that used with the properly sized AC input coupling capacitor, shows over 95db/w/m response down to 30 hz which seems to be a decent starting point especially considering its improved LF transient response and group delay over a ported enclosure. I envision this as a sort of 2.5 way system, incidentally.
Also, I have a Basta! simulation of the 20cu ft sealed enclosure with two E145 equivalent drivers that used with the properly sized AC input coupling capacitor, shows over 95db/w/m response down to 30 hz which seems to be a decent starting point especially considering its improved LF transient response and group delay over a ported enclosure. I envision this as a sort of 2.5 way system, incidentally.
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Hi,
Nothing wrong with 2nd order sealed. Nothing wrong with 3rd order (series cap).
Nothing wrong with 4th order ported. Each can be used to best advantages.
95dB only makes sense with a flea powered amplifier or a huge acoustic space
with a bigger amplifier, and complicates driver choices for the mid upwards.
It is PA territory, and not "ultimate" speaker design IMO.
rgds, sreten.
Nothing wrong with 2nd order sealed. Nothing wrong with 3rd order (series cap).
Nothing wrong with 4th order ported. Each can be used to best advantages.
95dB only makes sense with a flea powered amplifier or a huge acoustic space
with a bigger amplifier, and complicates driver choices for the mid upwards.
It is PA territory, and not "ultimate" speaker design IMO.
rgds, sreten.
Everybody has their own opinion of what 'ultimate' is - I basically meant this would be the best quality speaker that I planned to build to provide a musically satisfying experience.
Probably Le Cleach (one of whose flares I am now fabricating an oval concrete horn form to) and TAD (of which I will use the TD 4001) would tend to disagree with you that this is merely 'PA territory'.
Even the renowned Klipschorn falls to the lower 90 db range at 30 hz in its own corner of the woods. Basically, this design is intended to play in the dynamic range and efficiency ballpark of the Klipschorn and Altec A7 while being able to fit in the footprint usually associated with a conventional floor standing speaker. So, will fit in many living areas, vanishing dynamic compression, consistent lateral dispersion through the midrange and high end, good phase response even in the bass and all alnico magnets. What's not to like?
Btw, I built 8 'ACE' type HT speakers about 3 years ago. They are a semi -line array of 9 3 1/2" aluminum cone drivers each (4mm Xmax). People who have heard them are surprised when I mention that there is no SW in the system since they cover the range from 40 hz - 15 Khz by themselves. Incidentally, I've now come to find most BR tunings to be annoying both in frequency response and transiently.
Probably Le Cleach (one of whose flares I am now fabricating an oval concrete horn form to) and TAD (of which I will use the TD 4001) would tend to disagree with you that this is merely 'PA territory'.
Even the renowned Klipschorn falls to the lower 90 db range at 30 hz in its own corner of the woods. Basically, this design is intended to play in the dynamic range and efficiency ballpark of the Klipschorn and Altec A7 while being able to fit in the footprint usually associated with a conventional floor standing speaker. So, will fit in many living areas, vanishing dynamic compression, consistent lateral dispersion through the midrange and high end, good phase response even in the bass and all alnico magnets. What's not to like?
Btw, I built 8 'ACE' type HT speakers about 3 years ago. They are a semi -line array of 9 3 1/2" aluminum cone drivers each (4mm Xmax). People who have heard them are surprised when I mention that there is no SW in the system since they cover the range from 40 hz - 15 Khz by themselves. Incidentally, I've now come to find most BR tunings to be annoying both in frequency response and transiently.
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The only thing I can agree with you (that I know of) if not aligned properly. (I have no more info from you for that assertion.) 🙂
BR tuning develops a characteristic 'attack' where the port doesn't really start contributing until about the 2nd cycle of resonance. Then, also, the faster response falloff below cutoff has become more noticeable to me after listening to closed box systems with similar cutoff frequencies. The latter effect become much more noticeable when the BR tuning frequency starts going above 40 hz.
Polypropylene cones are heavier than most paper based cones and tend to handle less power also - I don't know of any similar sized PP cone speaker that is even close to being as efficient as a JBLK/E 145, and I don't recall any that come with an alnico magnet, either, although someone could correct me if I'm wrong here.
IMO, one of the advantages of very efficient drivers is that the max amount of energy that they can store as resonances in themselves or elsewhere in the system is relatively less compared to their sonic output, and they tend to sound 'cleaner' as a result, everything else being equal. There are plenty of clean sounding low efficiency drivers also, but higher efficiency improves that situation.
Polypropylene cones are heavier than most paper based cones and tend to handle less power also - I don't know of any similar sized PP cone speaker that is even close to being as efficient as a JBLK/E 145, and I don't recall any that come with an alnico magnet, either, although someone could correct me if I'm wrong here.
IMO, one of the advantages of very efficient drivers is that the max amount of energy that they can store as resonances in themselves or elsewhere in the system is relatively less compared to their sonic output, and they tend to sound 'cleaner' as a result, everything else being equal. There are plenty of clean sounding low efficiency drivers also, but higher efficiency improves that situation.
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I coat my cones with thinned shellac. The solvent for shellac is alcohol, which evaporates quickly. Shellac is waterproof when applied to wood, but I don't know how waterproof it is on paper. Probably depends upon how much you apply.
Hi -
Can you describe the sonic effect that shellac has on the cones you treat with it? Shellac appears to be resistant to the transfer of water vapor also, from what I read. It might be a good alternative to butyl rubber if it is desired to add stiffness, perhaps. Probably the more of what ever it is that one adds, the more resistant to water vapor transfer it becomes, but I assume that a reduction of say, 90% of the untreated transfer rate would be worth it. The question would be how to determine that before determining what amount to put on the speaker cone. I was assuming add 2 grams max per woofer and just go with the result, but that's not totally a 'safe' method if improving the speaker's response is also a goal as well as reducing water vapor transfer.
Can you describe the sonic effect that shellac has on the cones you treat with it? Shellac appears to be resistant to the transfer of water vapor also, from what I read. It might be a good alternative to butyl rubber if it is desired to add stiffness, perhaps. Probably the more of what ever it is that one adds, the more resistant to water vapor transfer it becomes, but I assume that a reduction of say, 90% of the untreated transfer rate would be worth it. The question would be how to determine that before determining what amount to put on the speaker cone. I was assuming add 2 grams max per woofer and just go with the result, but that's not totally a 'safe' method if improving the speaker's response is also a goal as well as reducing water vapor transfer.
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