Why foam surround?

[VWBobby 10+ year member]

Nice.... That's why a lot of the older drivers have a lower FS and a higher SPL/DB per watt. The suspension and surround was a lot less stiff than the subs of today.

Personally I have some subs that are around 10 years old now that are still running fine. No cracks/tears. I think the only times I've seen a foam surround tear/crack prematurely (before 10 years) is when it was abused with SPL comps or was installed in a dark colored trunk with extreme hot/cold for years on end.

 

[Haunz 10+ year member]

Most modern foam surrounds will last a LONG time as well since they are treated much better than old ones were. For example... I am not aware of any SI Mag drivers with a rotten surround and some of those are ~8 years old dating back to the v.1 Claw model and are still in usage today...

Its funny you mention this because I've reconed a couple SI mag V1s that had the foam split where the surround meets the cone...

I think its important to note that not all foam and rubber surrounds are created equal, both can come in a variety of formulations... generally speaking though, rubber is going to be the tougher material and will last longer and take more abuse, and I personally prefer a good quality butyl rubber surround over anything else...

 

[Haunz 10+ year member]

Although, I do like the idea that Pioneer is using with the layer of mesh or whatever in between two very thin layers of foam. Haven't tried it but it looks decent.

Looks like that surround might be made of nomex to me... //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[SPLaudio 5,000+ posts]

normally if there is a tare where the cone meets surrond its from the surround not allowing enough excursion or the spiders are beat and allowing futher cone travel than calculated...

 

[sundownz Pro Seller]

Its funny you mention this because I've reconed a couple SI mag V1s that had the foam split where the surround meets the cone...

The splitting at that joint is typically caused by excessive excursion as I had covered in my original post -- it's not simply a result of simply being foam or rotting away due to time. The v.1 Mag was rated for 600-watts RMS which would never allow that to happen -- of course at 100% or more of rated it opens up the possibility.

I've seen the same on my SA-8 surround in that exact spot in same situation with excessive excursion -- tooled up a new surround with a bit more capacity and eliminates that //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Yes, a rubber surround wouldn't tear at the same level but you can work with foam to make that impossible as well. Of course operating drivers outside of their intended range can cause damages - that isn't a surprise.

 

[Electrodynamic 10+ year member]

Its funny you mention this because I've reconed a couple SI mag V1s that had the foam split where the surround meets the cone...

The original Mag v1's only had issues with user abuse. They were rated at 600 watts and splitting the foam surround came from over excursion / excessive power. The later models (v2's and v3's) had a different formulation and shape foam surround that could handle more abuse. That, and all of the soft parts were upgraded along with different coils and motors.

Foam vs. rubber comes down to engineering goals. Foam is more compliant than rubber. Rubber can take more physical abuse. Foam is more efficient than rubber. Designing a speaker is a balancing act. Our surround material choice is based on compliance requirements, sensitivity desires, and excursion requirements.

 

[Haunz 10+ year member]

I can't comment on how the subs were used or possibly abused... but it was the same model sub from two different people with the same problem...

It also must have been the V2 because they were 1kw subs... (IIRC 3" D2 coil with about a 60mm wind of alumium wire)

my bad...

 

[Haunz 10+ year member]

Foam vs. rubber comes down to engineering goals. Foam is more compliant than rubber. Rubber can take more physical abuse. Foam is more efficient than rubber. Designing a speaker is a balancing act. Our surround material choice is based on compliance requirements, sensitivity desires, and excursion requirements.

I totally agree.. except that I'd be careful when stating things about sensitivity and compliance.... A thin rubber surround can easilly be more compliant and lighter weight then a thick foam surround...

I think it breaks down to the materials available from your manufacturer, along with design goals, when building with 'off the shelf' parts...

 

[denim 5,000+ posts]

Surprised it took until the 21st post to bring up compliance.

 

[Electrodynamic 10+ year member]

I can't comment on how the subs were used or possibly abused... but it was the same model sub from two different people with the same problem...

It also must have been the V2 because they were 1kw subs... (IIRC 3" D2 coil with about a 60mm wind of alumium wire)

my bad...

All versions of our Mag's used a 3" coil. The v1's were still rated at 600 watts. Just because it has a 3" coil doesn't automatically make it a 1k watt driver. And two drivers out of a few hundred isn't too shabby. From that particular batch I think 3 came back to us and all of the failures were from blatant abuse - it had nothing to do with the material of the surround was made of only. And as I previously stated, the composition and shape of the foam surround was changed after the v1's.

 

[Electrodynamic 10+ year member]

I totally agree.. except that I'd be careful when stating things about sensitivity and compliance.... A thin rubber surround can easilly be more compliant and lighter weight then a thick foam surround...
I think it breaks down to the materials available from your manufacturer, along with design goals, when building with 'off the shelf' parts...

Yes you would be correct with that statement when you compare apples to oranges (thin rubber to thick foam). However, per the same thickness, foam is more compliant than rubber. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Bob Saget]

Jacob pwned you fools //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[ciaonzo 5,000+ posts]

Looks like that surround might be made of nomex to me... //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

I'm not sure what that is between the layers of foam, I remember it was a sandwich though. Something thin and strong between two thin layers of foam, lol. Fabric maybe.

Surprised it took until the 21st post to bring up compliance.

I was referring to compliance with my reference to a low Fs in post #14. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ciaonzo 5,000+ posts]

Jacob pwned you fools //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

I don't think Jacob is interested in pwning anyone, lol. He always offers an objective and constructive point of view, and we always listen because he's got the experience under his belt.
Whatchoo doin' out the Dome anyway, lol? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ciaonzo 5,000+ posts]

Yes you would be correct with that statement when you compare apples to oranges (thin rubber to thick foam). However, per the same thickness, foam is more compliant than rubber. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

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?
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?