I posted this in another thread, and this is a new thread to discuss measurements:
http://www.diyaudio.com/forums/showthread.php?threadid=57435
Just so happens that most of my better speaker systems have drivers with rubber surrounds. 2 different 10" drivers in commercial systems seem to have become very stiff, one system is over 15 years old the other over 10, both bought used. I measured Fs of one driver and it was close to 50 Hz, 49 IIRC which indicates that the suspension is more than 3 times stiffer than it should be.
Pete B.
http://www.diyaudio.com/forums/showthread.php?threadid=57435
Just so happens that most of my better speaker systems have drivers with rubber surrounds. 2 different 10" drivers in commercial systems seem to have become very stiff, one system is over 15 years old the other over 10, both bought used. I measured Fs of one driver and it was close to 50 Hz, 49 IIRC which indicates that the suspension is more than 3 times stiffer than it should be.
Pete B.
KEF B139 Measurements Manufactured in 1975 - Measured in 2006
I pulled out a used pair of KEF B139s (SP1044) from storage with manufacturing dates from 1975 and measured the T&S parameters.
The compliance is 60% of the advertised parameter supplied by KEF. This is better than what I'm seeing in US manufactured drivers, but still a significant change. It's possible that different types of rubber materials were used.
I do not have measurements from ~1979 when I got them, they've been in storage since then. I don't recall if Linkwitz's SB article has measurements of B139s or not, but it would be good to get some older data as a reference:
(tables loose formating here on the forum, am I missing something?)
KEF B139-SP1044 UNIT SAMPLE: PLB#1 1/10/06
UNIT DATE: 28-Apr-1975
KEF
Delta M 15.75 Spec
Fshift -14%
Fs 32.6 25
Vas 98.1 164
Re 6.52 6.2
Qe .52 .4
Qm 4.6 5.5
Mms 42.8 43.5
no .63
SPLref 90.0 (half space) 84 (full space)
Bl 10.5 12.3
Qts .46 .37
Cms .56 .93 (calculated)
Compliance error compared to spec = .56/.93 = .6
========================================================================
KEF B139-SP1044 UNIT SAMPLE: PLB#2 1/10/06
UNIT DATE: 7-May-1975
KEF
Delta M 15.75 Spec
Fshift -14%
Fs 31.3 25
Vas 101 164
Re 6.2 6.2
Qe .48 .4
Qm 4.2 5.5
Mms 45.0 43.5
no .63
SPLref 90.0 (half space) 84 (full space)
Bl 10.7 12.3
Qts .43 .37
Cms .58 .93 (calculated)
Compliance error compared to spec = .58/.93 = .6
I pulled out a used pair of KEF B139s (SP1044) from storage with manufacturing dates from 1975 and measured the T&S parameters.
The compliance is 60% of the advertised parameter supplied by KEF. This is better than what I'm seeing in US manufactured drivers, but still a significant change. It's possible that different types of rubber materials were used.
I do not have measurements from ~1979 when I got them, they've been in storage since then. I don't recall if Linkwitz's SB article has measurements of B139s or not, but it would be good to get some older data as a reference:
(tables loose formating here on the forum, am I missing something?)
KEF B139-SP1044 UNIT SAMPLE: PLB#1 1/10/06
UNIT DATE: 28-Apr-1975
KEF
Delta M 15.75 Spec
Fshift -14%
Fs 32.6 25
Vas 98.1 164
Re 6.52 6.2
Qe .52 .4
Qm 4.6 5.5
Mms 42.8 43.5
no .63
SPLref 90.0 (half space) 84 (full space)
Bl 10.5 12.3
Qts .46 .37
Cms .56 .93 (calculated)
Compliance error compared to spec = .56/.93 = .6
========================================================================
KEF B139-SP1044 UNIT SAMPLE: PLB#2 1/10/06
UNIT DATE: 7-May-1975
KEF
Delta M 15.75 Spec
Fshift -14%
Fs 31.3 25
Vas 101 164
Re 6.2 6.2
Qe .48 .4
Qm 4.2 5.5
Mms 45.0 43.5
no .63
SPLref 90.0 (half space) 84 (full space)
Bl 10.7 12.3
Qts .43 .37
Cms .58 .93 (calculated)
Compliance error compared to spec = .58/.93 = .6
Hi PB2,
I have a pair of Focal 8K515 since 1992. Measured Fs was 30-31Hz.
Today, with the same temperature they are Fs= 50Hz !!!!
Another wf, the seas P17RCY declared 37Hz if I well remember, today
is 68 Hz !!!( at 22 celsius)
And the correct bass-alignement with perfect data.........
Indeed fun, don't you know?
Cheers,
inertial
I have a pair of Focal 8K515 since 1992. Measured Fs was 30-31Hz.
Today, with the same temperature they are Fs= 50Hz !!!!
Another wf, the seas P17RCY declared 37Hz if I well remember, today
is 68 Hz !!!( at 22 celsius)
And the correct bass-alignement with perfect data.........
Indeed fun, don't you know?
Cheers,
inertial
There are a number of detrimental things which happen to polymers with age (and rubber surrounds are polymers also --elastomers).
1
The substance slowly continues to polymerize. Molecules grow larger, connect to each other, and cross-link. this increases the hardness and reduces elasticity. It also leads to shrinking and cracking.
2.
The polymer begins to de-polymerize. Longer molecules break up into smaller ones, again, leading to a degradation of physical properties.
3.
Oxydation. Oxygen permeates the polymer and reacts with some of its molecules resulting in an oxydized product. This product has a higher molecular weight (by incorporating the oxygen atom), and is less elastic.
4.
Microorganisms
Bacteria grow especially well on surfaces, better on porous surfaces. Humidity can allow microbes of all kinds to form a microenvironment in the porous rubber substance, where they may release acids (their waste products), just like they do in your mouth, causing cavities. The acids can slowli degrade the physical properties of the rubber surround.
The above may not be a complete list of the things that happen to a polymer speaker suspension, but there are some steps to reduce or prevent damage.
1.
Avoid exposue to light, especially fluorescent light and daylight. UV destroys ALL polymers effectively.
2.
Avoid temperature extremes, like 85 F summer and 15F winter. Keep speakers in the same living space where a person is comfortable.
3.
avoid high humidity.
4 spray the surrounds with a silicone-based conditioning product (like Armor All) to keep moisture and oxygen out of the rubber. Spray BOTH sides -- you have to get behind the speaker element.
I've started spraying after I've seen my expensive speakers from 1985 die from surrounds that started to crack and crumble.
Joseph Hynes
1
The substance slowly continues to polymerize. Molecules grow larger, connect to each other, and cross-link. this increases the hardness and reduces elasticity. It also leads to shrinking and cracking.
2.
The polymer begins to de-polymerize. Longer molecules break up into smaller ones, again, leading to a degradation of physical properties.
3.
Oxydation. Oxygen permeates the polymer and reacts with some of its molecules resulting in an oxydized product. This product has a higher molecular weight (by incorporating the oxygen atom), and is less elastic.
4.
Microorganisms
Bacteria grow especially well on surfaces, better on porous surfaces. Humidity can allow microbes of all kinds to form a microenvironment in the porous rubber substance, where they may release acids (their waste products), just like they do in your mouth, causing cavities. The acids can slowli degrade the physical properties of the rubber surround.
The above may not be a complete list of the things that happen to a polymer speaker suspension, but there are some steps to reduce or prevent damage.
1.
Avoid exposue to light, especially fluorescent light and daylight. UV destroys ALL polymers effectively.
2.
Avoid temperature extremes, like 85 F summer and 15F winter. Keep speakers in the same living space where a person is comfortable.
3.
avoid high humidity.
4 spray the surrounds with a silicone-based conditioning product (like Armor All) to keep moisture and oxygen out of the rubber. Spray BOTH sides -- you have to get behind the speaker element.
I've started spraying after I've seen my expensive speakers from 1985 die from surrounds that started to crack and crumble.
Joseph Hynes
Hi Joseph,
I have noted that also cloth-surround ( PRO-drivers) are more stiffer after many years.
I believe that with the right "painting" it can return like "news".
Could you indicate me a generic sostance to apply for the cloth?
Some people talking about silicone, but what type of it ( if it is important, perdone me I understand nada about chemistry).
Thanks advanced,
Inertial
I have noted that also cloth-surround ( PRO-drivers) are more stiffer after many years.
I believe that with the right "painting" it can return like "news".
Could you indicate me a generic sostance to apply for the cloth?
Some people talking about silicone, but what type of it ( if it is important, perdone me I understand nada about chemistry).
Thanks advanced,
Inertial
Thank you Joseph, very informative. Turns out my dad is also a chemical engineer and a retired polymer expert so I hear a lot of this talk. Do you know if silicone oil in general is as good as Armor All?
Any products that might help after the damage is done, I don't have any that are cracked and falling apart just loosing their compliance.
I'd like to ask, if you don't mind what brand drivers those are with surrounds that cracked. I'll try to find out what type of rubber was used.
Thanks again,
Pete B.
Any products that might help after the damage is done, I don't have any that are cracked and falling apart just loosing their compliance.
I'd like to ask, if you don't mind what brand drivers those are with surrounds that cracked. I'll try to find out what type of rubber was used.
Thanks again,
Pete B.
Joseph Hynes said:
I think every country has on the market some form of silicone spray.
The sprays for waterproofing boots in Northern Europe should work.
In the South, the sprays for conditioning leather shoes, handbags and furniture should have similar composition.
It's important to look for a product containing silicone, because this is a man-made material which lasts almost forever, and does not attract pests. Conditioning products not based on silicone often contain natural waxes and oils which have limited lifetime.
They must have some leather seats inside those Alfa-Romeos and Lamborghinis in Italy, Si? So there must exist products to condition and protect them.
Joseph
The sprays for waterproofing boots in Northern Europe should work.
In the South, the sprays for conditioning leather shoes, handbags and furniture should have similar composition.
It's important to look for a product containing silicone, because this is a man-made material which lasts almost forever, and does not attract pests. Conditioning products not based on silicone often contain natural waxes and oils which have limited lifetime.
They must have some leather seats inside those Alfa-Romeos and Lamborghinis in Italy, Si? So there must exist products to condition and protect them.
Joseph
Armor All has gotten some bad press but I don't know if the claims are valid. I wonder if it has additives that do more for the shiny look and take away from the preservative qualities or perhaps cause some damage, this is pure speculation on my part.
How about this product:
http://www.bhphotovideo.com/bnh/con...446&is=REG&addedTroughType=categoryNavigation
Pete B.
How about this product:
http://www.bhphotovideo.com/bnh/con...446&is=REG&addedTroughType=categoryNavigation
Pete B.
richie00boy said:
I have a bottle of Armor-All from U.S. containing silicone, but it is not intended for car interior -- tires only.
I mentioned ArmorAll just as an example of the kind of product I'm thinking of, not a specific brand recommendation.
There is unfortunately no solid information out there about how any product performs at preserving speakers, so we are in uncharted waters.
I guess the relevant points are:
watchout: the product may slowly impregnate into the area surrounding the cone, causing ugly oil stain marks. It may also impregnate into the cone (if paper) causing an ugly stain and possibly reducing the stiffness of the cone.
I've shellacked my cones before conditioning the surrounds, and tape-masked the enclosure to prevent over-spraying and seepage. Oily stains have a way of seeping very very slowly, so you may only know you-ve oversprayer a year later.
For my next pair of speakers, I'm actually considering using clear silicone sealant sold for rimming widows -the kind that remains elastic.
I figured I would apply it with my finger into the surrounds, leaving a very thin film, and removing the excess.
Joseph
I mentioned ArmorAll just as an example of the kind of product I'm thinking of, not a specific brand recommendation.
There is unfortunately no solid information out there about how any product performs at preserving speakers, so we are in uncharted waters.
I guess the relevant points are:
watchout: the product may slowly impregnate into the area surrounding the cone, causing ugly oil stain marks. It may also impregnate into the cone (if paper) causing an ugly stain and possibly reducing the stiffness of the cone.
I've shellacked my cones before conditioning the surrounds, and tape-masked the enclosure to prevent over-spraying and seepage. Oily stains have a way of seeping very very slowly, so you may only know you-ve oversprayer a year later.
For my next pair of speakers, I'm actually considering using clear silicone sealant sold for rimming widows -the kind that remains elastic.
I figured I would apply it with my finger into the surrounds, leaving a very thin film, and removing the excess.
Joseph
Just a couple comments from a polymer dude:
The breakdown mechanisms are much as Joseph said. Degradation from UV, ozone, oxygen, sulfur, and just plain age are all present, but to a greater or lesser degree depending on the actual polymer. His suggestions on protecting the drivers by their environment are very sound ones.
All polymers are not created equal. They have different breakdown paths and require different sorts of solutions. Aftermarket products are not generally terribly effective- for example, silicone can make a degraded surface look better, and may even penetrate and plasticize a material, but it is absolutely transparent to oxygen. And the newly plasticized degraded material will NOT behave in the same way as the virgin material. It may be better than nothing, but... And because all base materials are different with different breakdown mechanisms and different reactivities to treatments, it is impossible to have the one magic bullet treatment that protects all materials from all insults. General statements like, "Armor All is bad" should be largely disregarded.
Unfortunately, the real solution is better surround materials technologies. What I see out there is pretty crude and unsophisticated. But cheap and well-known, which are indeed virtues.
As with a phono cartridge (which also have elastomers that degrade over time), when a surround ages, it needs to be replaced (or the driver does, sadly).
The breakdown mechanisms are much as Joseph said. Degradation from UV, ozone, oxygen, sulfur, and just plain age are all present, but to a greater or lesser degree depending on the actual polymer. His suggestions on protecting the drivers by their environment are very sound ones.
All polymers are not created equal. They have different breakdown paths and require different sorts of solutions. Aftermarket products are not generally terribly effective- for example, silicone can make a degraded surface look better, and may even penetrate and plasticize a material, but it is absolutely transparent to oxygen. And the newly plasticized degraded material will NOT behave in the same way as the virgin material. It may be better than nothing, but... And because all base materials are different with different breakdown mechanisms and different reactivities to treatments, it is impossible to have the one magic bullet treatment that protects all materials from all insults. General statements like, "Armor All is bad" should be largely disregarded.
Unfortunately, the real solution is better surround materials technologies. What I see out there is pretty crude and unsophisticated. But cheap and well-known, which are indeed virtues.
As with a phono cartridge (which also have elastomers that degrade over time), when a surround ages, it needs to be replaced (or the driver does, sadly).
Silicone spray lubricant
Thank you all for the suggestions.
This is an automotive silicone spray lubricant, the chemical composition is listed at the bottom:
http://householdproducts.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&id=7007009
Somehow it's major ingredient: "Aliphatic petroleum distillate" does not sound like silicone.
Would this be an acceptable silicone preservative for these surrounds?
Pete B.
Thank you all for the suggestions.
This is an automotive silicone spray lubricant, the chemical composition is listed at the bottom:
http://householdproducts.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&id=7007009
Somehow it's major ingredient: "Aliphatic petroleum distillate" does not sound like silicone.
Would this be an acceptable silicone preservative for these surrounds?
Pete B.
PB2 said:
I have mentioned this in another thread here: I bought a pair of Seas 17 cm woofers with the milky translucent cones on ebay which probably date from the late 80s, early 90s. Surrounds are absolutely shot, brownish, glazy surface, deep pores and an fs around 100 Hz. The might be from natural rubber from DKM (Dr. Kurt Müller of Krefeld) as most European drivers of the time. I will have to check if they bear the typical SR... type number.
Other than that, I only have a few Peerless CSX and Vifa XT18 drivers with slightly hardened and brownish surfaces bought off ebay in the case of the Peerless and from an OEM designer who had had them for a couple of months in the case of the Vifas. In both cases, the degradation was only superficial and could be removed with alcohol and glycerine.
Glycerine is said to reduce down rubber! I think using breaking fluid for cars is a better option. This liquide contains precerving agents for rubber,as there are many rubber gaskets in the hydralic breaking system of a car. Silicone based stuff may help if we are talking vinyl rubber(don´t know if it´s called so in English).
In every case, please be very careful and apply only small amounts. E.g. silicone shouldn´t be able to enter contacts , because of its insulating properties
In every case, please be very careful and apply only small amounts. E.g. silicone shouldn´t be able to enter contacts , because of its insulating properties
As a kid, Back in the 1980's, I would carry home old TV sets thrown in the garbage and take them apart. Many of these had manufacturing dates in the 1940's.
It was a certainty that the speakers outlived the sets they were in. Some of the speakers I recovered were large 25-30 cm round and oval drivers, preserved in excellent condition, behind well-made grilles of woven fabric. The cones (of paper) were impeccable, and the edge suspension, made of rolled cloth impregnated with some shiny tar, were unaffected by many years of use. It gave me the impression that speakers last forever.
Ok, the response didn't go lower than 120Hz, but at least they didn't age as poorly as some of today's products.
Seems I was not the only one to notice that speakers last forever (if well made) Manufacturers found this a serious drawback.
Moral of the story:
Don't buy used speakers that are more than 10 years old, or, better yet, don't buy used speakers at all!
For the owner of a decaying speaker, the temptation to sell it on Ebay instead of throwing it away is enormous. He has payed good money for it, and is very distressed at the thought of junking it. It's his baby. He's grown up with it. Junking it is too painful. No, we must find a loving home for this gem...
Joseph
It was a certainty that the speakers outlived the sets they were in. Some of the speakers I recovered were large 25-30 cm round and oval drivers, preserved in excellent condition, behind well-made grilles of woven fabric. The cones (of paper) were impeccable, and the edge suspension, made of rolled cloth impregnated with some shiny tar, were unaffected by many years of use. It gave me the impression that speakers last forever.
Ok, the response didn't go lower than 120Hz, but at least they didn't age as poorly as some of today's products.
Seems I was not the only one to notice that speakers last forever (if well made) Manufacturers found this a serious drawback.
Moral of the story:
Don't buy used speakers that are more than 10 years old, or, better yet, don't buy used speakers at all!
For the owner of a decaying speaker, the temptation to sell it on Ebay instead of throwing it away is enormous. He has payed good money for it, and is very distressed at the thought of junking it. It's his baby. He's grown up with it. Junking it is too painful. No, we must find a loving home for this gem...
Joseph