Why foam surround?

[RAM_Designs 5,000+ posts]

Whatchoo doin' out the Dome anyway, lol? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Lol, I was thinking the same thing.

Anyways, keep up the good conversation guys.

 

[Electrodynamic 10+ year member]

But what if we kept the target efficiency or compliance static, and the resulting thickness between the two materials varied, is that still comparing apples to oranges?

Due to the nature of the aforementioned statement about me not being able to safely say that foam is more compliant than rubber I made the latter post. Now you’re asking if compliance and sensitivity stay the same with two wildly different surround materials and thicknesses can you not compare the two? Yes you can compare them. My response was to someone nit-picking what I wrote about compliances between the two materials. Doing what you asked about is extremely difficult and has a high probability of negatively impacting the design goals of the driver (one may be wider than another, have a different profile, etc, all of which affect the compliance curve, not just the overall Cms figure). It can be done, but it's difficult to do, which is what I said in my previous post. Some times it is imperative to use foam or a soft cloth (depending on the application and design needs) to obtain a certain compliance which rubber cannot be made thin enough without impacting the durability of the surround. Of course you can change your spider weave or material or both to combat the surround compliance, but it's a mix (remember when I said "balancing act"?) of the two that shapes the overall compliance curve and gives you the overall compliance of the driver. A lot of the time it's just easier to select a surround based on what you need.

While we're on this topic, can you control and change the size of the size of the bubbles in the foam, while keeping the thickness static, to influence the compliance?

Yes. Different foams affect the compliance even if the thickness stays the same (which goes for rubber as well).

 

[ciaonzo 5,000+ posts]

Due to the nature of the aforementioned statement about me not being able to safely say that foam is more compliant than rubber I made the latter post. Now you’re asking if compliance and sensitivity stay the same with two wildly different surround materials and thicknesses can you not compare the two? Yes you can compare them. My response was to someone nit-picking what I wrote about compliances between the two materials. Doing what you asked about is extremely difficult and has a high probability of negatively impacting the design goals of the driver (one may be wider than another, have a different profile, etc, all of which affect the compliance curve, not just the overall Cms figure).

I do realize that, I was being a tad facetious. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
I wasn't trying to force the requirement of both efficiency AND compliance targets tracking perfectly with each other, just one or the other for the sake of an example.

My piece in all this was just to say that with all my experience with foam and rubber over the years, I've learned my lesson. I take very good care of my things and they last me nearly forever. Of the two materials, only foam surrounds have been a point of failure WITHOUT abuse being a factor. Factor in abuse and there's no way foam would be my choice. Over-excursion is a fact of life sometimes, and a rubber surround will fare better if the suspension is the limiting factor in the design. Some drivers are motor-limited and some are suspension-limited, I realize that. I also realize guys like Jacob and yourself are very good at finding a nice balance when it comes to that, so mistakes or abuse would be the most likely cause for ripped foam. In my experience though, rubber survives what foam can't.

I keep touching on thickness because I'm of the opinion that the spider should be the main component of compliance and that the surround should affect it very little, essentially offering the least amount of resistance to movement while maintaining just enough thickness to resist cavitation and provide the required centering. The majority of foam surrounds force a higher resonance than I like, but in fairness I have come across a few rubber ones that do the same.

 

[ciaonzo 5,000+ posts]

Forgot to mention I appreciate the very strong point you made concerning the overall compliance curve and not simply the resulting CMS figure. I'm sure that introduces many new variables that I simply have no real-world experience with.

 

[Electrodynamic 10+ year member]

Forgot to mention I appreciate the very strong point you made concerning the overall compliance curve and not simply the resulting CMS figure. I'm sure that introduces many new variables that I simply have no real-world experience with.

No problem. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif It's essential to engineer for the shape of the curve no matter what your target audience is. Either you want it extremely flat for zero suspension induced distortion or you actually may want the oposite - a non linear curve for disrtion for your target audience. Or you may want the suspension to tighten up before soft part or hard part bottoming out, etc.

 

[ciaonzo 5,000+ posts]

Indeed.

 

[Vagomire 10+ year member]

I have a pair of kenwoods with foam surround and they both cracked and ripped due to the cold weather and over-stretching of the surround.

My buddy has the samne system and his woofers cracked as well. I will not be buying a woofer with foam surround ever again..

 

[Bass911 10+ year member]

For all you guys out there that plan on keeping subs with rubber surrounds for 10-15 years, try rubbing ArmorAll into the surround. I've done it a few times, but weather is not a serious issue where I live.

 

[SPLaudio 5,000+ posts]

^ armorall will help release the glue surrond to cone, a no no...

 

[audio_phill 10+ year member]

to support the longevity of good foam, my realistic Mach 1's (1979 model first release run) my foam still looks new. Probably thanks to Climate control and no UV exposure, but they look as if they've never even been played and I've beat the **** outta these things lol.

Lack of coloration wise, I pull for NBR... love the stuff lol.

 

[Cali_Screw 10+ year member]

Speaking of all this, any one know where i can find some 10" cones with rubber surrounds for a 3" coil //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif?

 

[Bass911 10+ year member]

^ armorall will help release the glue surrond to cone, a no no...

I don't put it anywhere near the glue, unless you think the ArmorAll somehow travels through the rubber to the glue. Btw, I've never had any glue failure in my life.

 

[Reimers 10+ year member]

i`ve had several old cerwin vega woofers whit foam surrounds. have only had one give up on me yet. that was on an 19 year old 12" woofer

 

[Suicide Bobb 5,000+ posts]

I love Pioneer's foam surround ish...feels extremely durable, and surprisingly high quality...makes me want one tbh

 

[subzero 5,000+ posts]

I like the looks of accordion surrounds, and the JBL's I have are from 86' Still good as new

I think it is a paper surround coated with slime