View Full Version : Avoiding the silly practice of re foaming speakers
Light Dependant Resistor
15-05-2015, 06:54
Hi
Here is an image of a AR driver needing work, but can we put an end to the
IMO silly practice of refoaming. 14770
As you just need to do it again and again likely every year , no wonder the refoaming businesses are there
rubbing their hands together, so can we collectively put an end to this silly practice please.
Much better is to use rubber surrounds, as compliance is better still and they do not wear out.
here is my own AR7 with rubber surround, perfect and set to last at least 20 years or more
14771
I refoamed some JBL Control 5's last year. From the online trawl of forums there was some suggestion that changing from foam to rubber can change the sound (not specific to the JBL) so I stuck with foam. I gave these to my godson and in any event it is too soon to know how long they will last. I also had a pair of JPW AP2's (which I also, to my regret, gave away) which had previously been refoamed, I must have had these for 4 or 5 years and they were fine. Why would you need to refoam every year?
changing from foam to rubber can change the sound
Why would you need to refoam every year?
Yup.
I'm not a fan of foam for roll surrounds but:
1/ You certainly don't have to do it every year - every 15 years more like it.
2/ Most foam roll surrounds are more compliant, not less, than the rubber equivalent.
3/ Foam and rubber foam surrounds will have different compliance (flexibility) and will terminate the edge of the cone differently - both of these aspects will have an impact upon the sound.
Light Dependant Resistor
15-05-2015, 08:10
I refoamed some JBL Control 5's last year. From the online trawl of forums there was some suggestion that changing from foam to rubber can change the sound (not specific to the JBL) so I stuck with foam. I gave these to my godson and in any event it is too soon to know how long they will last. I also had a pair of JPW AP2's (which I also, to my regret, gave away) which had previously been refoamed, I must have had these for 4 or 5 years and they were fine. Why would you need to refoam every year?
Foam is such a silly substance, it deteriorates and perishes, why install something that is behind your back
rotting away.. it doesn't make sense. Original AR drivers had cloth surrounds and from what I see are good
for 45 years or more. So foam is not representative of how these speakers should sound
( neither is rubber but it is better than foam )
How many Kef b110 do you see the rubber failing on ? .. I don't think any . Foam crept in to the market place and needs moving, starting with this silly refoaming caper, lets bring back proper workmanship to speakers.
Audio Advent
15-05-2015, 14:13
Materials have changed and modern foam doesn't rot as badly as before (and may not rot at all in the right conditions).
Foam surrounds didn't "creep in" they were used on purpose for it's particular properties for particular driver designs! It's 10 times lighter than rubber for a start and it controls the cone completely differently to other types of surround.
Kef B110s are not the best midrange in the world and I'd argue that their capabilities are quite a bit behind todays modern drivers, many of which require foam surrounds for their performance. Rubber does harden though and lose it's compliance and then change the sound of the speaker over the years.
Seems a bit of a particular bug bear to have, going to war with the past.... It's too late! The thing that is annoying you, 30 year old speakers with rotten foam, happened err... 30 years ago and today is different.
The AR drivers which were made with foam were designed with foam and are supposed to sound as they do with foam. Those with cloth were designed with cloth and sound like they're supposed to when fitted with cloth. The foam ones were not designed as cloth and then they just changed the surrounds later - the spider and much else will be different too.
Rubber will rot out the same as foam.
awkwardbydesign
08-06-2015, 10:27
Rubber will rot out the same as foam.
Really? What Brings you to that conclusion?
walpurgis
08-06-2015, 10:48
Really? What Brings you to that conclusion?
I wondered about that too.
I've seen and owned Kef and Tannoy drive units over forty years old with perfect rubber roll surounds that were as pliable as new. I still have some that have not even the slightest sign of hardening or surface break down. Unlike just about every older foam surround I've seen. Which either go hard and crumble, like old JBLs and ARs do, or go soggy and sticky and collapse as the Tannoy 12" & 15" HPD surrounds did.
Drive units can be fitted with surrounds of a type other than those originally specified without problems. Tannoy did just this, as their dual concentrics evolved for various applications. The 12" ceramic magnet models had either corrugated hard edge cones or foam roll surrounds. The 12" Monitor Gold had doped pleated edges or rubber roll or foam surrounds, with the basic cone geometry and paper cone pulp type not changing.
only speaker surrounds ive ever had go were foam ones. just sold a set of old tannoy e11 s with rubber surrounds and they were absolutely mint rubber wise.
Yes rubber will eventualy perish/crack, how long I supose depends on the grade, modern "rubber" is usually some form of thermo plastic elastomer as real rubber from the tree is rarely used these days. The thing is, long before it gets as bad as cracking it will have become stiff and useless as a cone surround. When it comes to cars, be it a windscreen suround, door seal or even tyres, I've seen them all dry out and break up on classic cars. Modern materials are better, but we will just have to wait and see how they age.
This is the one of the bass drivers from my Celestion 66 renovation, they were both gone.
http://www.jkwynn.co.uk/Project_Images/66/66_04.jpg
awkwardbydesign
08-06-2015, 13:18
Yes rubber will eventualy perish/crack, how long I supose depends on the grade, modern "rubber" is usually some form of thermo plastic elastomer as real rubber from the tree is rarely used these days. The thing is, long before it gets as bad as cracking it will have become stiff and useless as a cone surround. When it comes to cars, be it a windscreen suround, door seal or even tyres, I've seen them all dry out and break up on classic cars. Modern materials are better, but we will just have to wait and see how they age.
This is the one of the bass drivers from my Celestion 66 renovation, they were both gone.
http://www.jkwynn.co.uk/Project_Images/66/66_04.jpg
If you want go generalise based on personal experience, I would have to mention the numerous KEF B139s from the '60s which have been fine. In another field, Moto Guzzis from the '70s need all their rubber seals replacing, while Hondas don't.
walpurgis
08-06-2015, 13:27
Yes rubber will eventualy perish/crack, how long I supose depends on the grade, modern "rubber" is usually some form of thermo plastic elastomer as real rubber from the tree is rarely used these days. The thing is, long before it gets as bad as cracking it will have become stiff and useless as a cone surround. When it comes to cars, be it a windscreen suround, door seal or even tyres, I've seen them all dry out and break up on classic cars. Modern materials are better, but we will just have to wait and see how they age.
This is the one of the bass drivers from my Celestion 66 renovation, they were both gone.
http://www.jkwynn.co.uk/Project_Images/66/66_04.jpg
You don't want to be pulling the cones about like that if you intend replacing those rubber surrounds.
As for automotive rubber parts. That's a different story. They are exposed to all sorts of contaminants and plenty of UV.
The sixties KEF B139 had foam surrounds. They moved to rubber around 1970. Coincidentally, I have two near mint pairs of the BD139 ABR sitting in front of me right now. Each has perfect rubber surrounds.
My point is that you can not genaralize, eg "rubber surounds don't rot", they quite clearly do.
Some types are going to be better than others thats all and like cars, speakers are exposed to a variety of climatic conditions depending on their use/siting. So even within the same product you will find differing ageing effects. I have a perfectly good pair of Celestion 66 bass drivers from the same period, maybe one set were exposed to sunlight for long periods, who knows. Nicotine and aerosols may also have an adverse effect.
I don't know if you can get new surrounds for the 66's but I picked up a pair of clean and closely matched drivers (frequency sweep) for £80 so it wasn't worth messing with these.
The thing is ALL driver surounds age and even if the suround is intact that doesn't mean it is performing as intended, this applies to foam or rubber also rubberised cloth and doped cloth, its not what it looks like that matters.
Doped cloth is the way forward.
Oddly perhaps, in many ways I think you are right. I've been thinking about the original thread post and also my response. In retrospect u think ithe OP's stance could be described as 'let's not use foam because it's a roll surround material with a very finite life' and this much is definitely true. No matter what you do to preserve a foam surround it will rot and decompose (20 years in the UK but only a few years in the tropics).
I'm not a fan of foam for roll surrounds but:
1/ You certainly don't have to do it every year - every 15 years more like it.
2/ Most foam roll surrounds are more compliant, not less, than the rubber equivalent.
3/ Foam and rubber foam surrounds will have different compliance (flexibility) and will terminate the edge of the cone differently - both of these aspects will have an impact upon the sound.
Exactly this. It is not a silly practice at all but is done to improve compliance and increase the Fas value for the drive unit, allowing lower resonant frequency/better bass response.
You will change the free air resonance, and mechanical compliance if you change the designed surround so the speaker wont work the same with the same crossover and cabinet (it may well be close enough, it may not, but it will be different).
A good foam surround treated with UV inhibitors, as many quality ones are these days, can last 20 years easily. I have never ever heard of any foam surround lasting just one year, and refoaming companies don't exist....just companies who will re-foam speakers (there's a difference), and trust me, those that do it, don't earn a hell of a lot of profit for doing it and I very much doubt if any of them "rub their hands with glee" because it's one of those pain in the a**e jobs; most (including myself) cover their time and that's it. Its not an especially nice job to do and great care is required to do the job properly and neatly.
You cant expect any electro-mechanical device to last forever, and just as your cars need annual servicing at far greater cost than perhaps you can buy a pair of speakers for these days, I'd hardly describe a speaker cone re-foam every 20 years as extraordinary or bad.
There are new more exotic polymers being experiment with for surrounds but a good foam surround does the job well without drastically altering mechanical properties until the point it requires replacing, unlike SOME rubber and doped paper surrounds which do.
I take great care to keep accurate records for many types of drive units that come in, and compare against manufacturer's data where possible. In the case of most drive units, suspension and surround compliance does tend to change with age, the suspension becoming more compliant and the surrounds more or LESS compliant depending upon material used. The net effect is that the speaker characteristics slowly drift with age, whatever surround you use, with time and use.
Hi
Here is an image of a AR driver needing work, but can we put an end to the
IMO silly practice of refoaming. 14770
As you just need to do it again and again likely every year , no wonder the refoaming businesses are there
rubbing their hands together, so can we collectively put an end to this silly practice please.
Much better is to use rubber surrounds, as compliance is better still and they do not wear out.
here is my own AR7 with rubber surround, perfect and set to last at least 20 years or more
14771
What a silly post - foam does not rot within one year here in Europe (& I doubt anywhere so quickly), it is not a massive job to change surrounds & I would never be interested in a set of speakers that were foam and are now rubber...they are no longer as the manufacturer designed them.
Richard
Neil McCauley
28-07-2015, 18:38
Hi
Here is an image of a AR driver needing work, but can we put an end to the
IMO silly practice of refoaming. 14770
As you just need to do it again and again likely every year , no wonder the refoaming businesses are there
rubbing their hands together, so can we collectively put an end to this silly practice please.
Much better is to use rubber surrounds, as compliance is better still and they do not wear out.
here is my own AR7 with rubber surround, perfect and set to last at least 20 years or more
14771
I suspect you might be correct although that said, I have no direct personal experience to apply to this. However, I know a man that does; Mr Dave Smith at http://vintagegale.com/index.php
Had rubber break on me a couple of times...
awkwardbydesign
29-07-2015, 08:04
The sixties KEF B139 had foam surrounds. They moved to rubber around 1970. Coincidentally, I have two near mint pairs of the BD139 ABR sitting in front of me right now. Each has perfect rubber surrounds.
The racetrack version from 1965 had a rubber surround. I have had several.
I'd tend to try and replace a damaged or degraded surround with something as close to the surround they were manufactured with as I could get. Then, originality is preserved as far as possible, and the original specification for the driver is most likely met.
Do it again in fifteen years? If necessary - it's hardly the most arduous job, is it?
Ninanina
30-07-2015, 23:06
I'd tend to try and replace a damaged or degraded surround with something as close to the surround they were manufactured with as I could get. Then, originality is preserved as far as possible, and the original specification for the driver is most likely met.
Do it again in fifteen years? If necessary - it's hardly the most arduous job, is it?
Exactly...
I would not touch a driver that had a rubber surround when the manufacturer specified foam, and vise versa... I am sure the original manufacturer was much better at deciding which surround was perfect for the driver characteristics than myself... :)
awkwardbydesign
31-07-2015, 07:53
Exactly...
I would not touch a driver that had a rubber surround when the manufacturer specified foam, and vise versa... I am sure the original manufacturer was much better at deciding which surround was perfect for the driver characteristics than myself... :)
Unless you wanted a different characteristic, of course.
if someone sneaked in to your house and replaced your foam surrounds with rubber, put the grilles back on and left, would you notice the sound had changed next time you sat down to listen?
I have my doubts.
if someone sneaked in to your house and replaced your foam surrounds with rubber, put the grilles back on and left, would you notice the sound had changed next time you sat down to listen?
I have my doubts.
Maybe not the sound but the red hot grilles would soon be a give-away.
if someone sneaked in to your house and replaced your foam surrounds with rubber, put the grilles back on and left, would you notice the sound had changed next time you sat down to listen?
I have my doubts.
Indeed, and I expect the same is true of the vast majority of jaw-dropping, veil-lifting, game-changing tweaks that everyone gets so excited about. It'd be the ultimate blind test; difficult to arrange, of course.
It is one of the scarier concepts in hi-fi, isn't it?
Just imagine if someone had been in and put your directional cables in the wrong way round and you never noticed?
Just imagine if someone had been in and put your directional cables in the wrong way round and you never noticed?
How would you not notice? The music would be playing backwards :ner:
How would you not notice? The music would be playing backwards :ner:
And then Satan would appear, which would be a dead giveaway.
No, Satan only appears if you play some Judas Preist backwards. Don't ask me how I know that...
Girl with guitar backwards you 're pretty safe. Indeed i'm told that's how she prefers it.
I thought it was Chicago:eyebrows:
https://www.youtube.com/watch?feature=player_detailpage&v=XJxSP3LC9BA
jandl100
07-08-2015, 08:38
Back to the OP .... from my non-technical and probably naïve viewpoint, if you change the stiffness of the connecting surround material then you change the ability to move of the cone - i.e. its efficiency. Leaving the accompanying other drivers the same there will be a mis-match in levels between the drivers. I'd expect this to be audible.
I'm sure someone will know tell me why my simplistic reasoning is flawed. :lol:
walpurgis
07-08-2015, 09:05
Back to the OP .... from my non-technical and probably naïve viewpoint, if you change the stiffness of the connecting surround material then you change the ability to move of the cone - i.e. its efficiency. Leaving the accompanying other drivers the same there will be a mis-match in levels between the drivers. I'd expect this to be audible.
I'm sure someone will know tell me why my simplistic reasoning is flawed. :lol:
Whilst there may (or may not) be a change in bass output levels due to surround stiffness changes, the "accompanying drivers" will be crossed over at higher frequencies where the output (efficiency) of the main driver into the midrange is unlikely to be significantly affected by a change of surround compliance, due to the reduced cone excursion required. I doubt you'd hear much difference, if any.
Audio Advent
07-08-2015, 16:41
Whilst there may (or may not) be a change in bass output levels due to surround stiffness changes, the "accompanying drivers" will be crossed over at higher frequencies where the output (efficiency) of the main driver into the midrange is unlikely to be significantly affected by a change of surround compliance, due to the reduced cone excursion required. I doubt you'd hear much difference, if any.
Foam is used on midranges too.
Different surrounds change break-up mode frequencies, change the absorption of the wave in the cone material and will affect how the spider suspension damps the cone too.
I would reckon a top speaker designer would possibly choose to use a different driver altogether or design the crossover differently if they discovered the drivers were now being manufactured with different materials.
Now, how much of a difference you'd hear in reality would need to be actually tested - I don't think one can really second guess that or logically work out how much someone would notice.
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