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Advent masonite frame woofer foam recommendation

I suspect that some surrounds made in China that are available for wholesale purchase are molded from foam that is determined by the factory, not the customer. I can't say for sure because I've only had surrounds made for me in the USA to my specs.

A wholesale buyer of made-in-the-USA surrounds can have surrounds made to order for resale on the retail market that might not replicate original compliance if that wholesale buyer makes the wrong choices in the thickness of the foam being molded, the roll width, or both. The manufacturer can supply the wholesaler with samples of surrounds they make to show the wholesaler what tooling they have. It is then up to the wholesale buyer to tell the manufacturer what they want. That buyer needs to know what they want to get it right. For one example, they need to know if what they want is molded from 3/8" polyether or 7/16" polyether. It does make a difference in compliance. The buyer might make the wrong choice, but they're not going to trash 500 or 1,000 parts because they are "close enough for most people".
 
rmoreau61 said:
Poorly constructed sentence on my part:sigh:. What I meant was, if I have the wrong surrounds in now, replacing them with the right surrounds would cause books and lights to fall, general mayhem etc. The current surrounds actually do cause one of my ceiling fixtures to vibrate - something I never experienced before these speakers. One of my projects is to re-seat that fixture (maybe some liquid nail or RTV or something).
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OK cool. :thmbsp: Didn't mean to sound kinda snarky.

Doug
 
When Fs dropped from 25 to 17, what happened to Qts and Vas? If only Fs changed, there would be a drop in sensitvity. If Vas increased, sensitvity might stay the same, but you'd need a bigger enclosure for similar F3. And so on. I would not be looking to decrease Fs unless it put me closer to original specs, along with Vas and Qts. Do we know what those specs should be?
 
JRhoBurton said:
When Fs dropped from 25 to 17, what happened to Qts and Vas? If only Fs changed, there would be a drop in sensitvity. If Vas increased, sensitvity might stay the same, but you'd need a bigger enclosure for similar F3. And so on. I would not be looking to decrease Fs unless it put me closer to original specs, along with Vas and Qts. Do we know what those specs should be?
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What really matters is moving mass and motor strength regarding sensitivity and most other parameters, and neither of those are going to change due to different foam. We also want the compliance as high as possible so that the box air compliance dominates. We want Vas as large as possible. Qts is going to change because it is dependent on Fs. What matters in the end is the in system Fc and Qtc. A higher compliance edge will provide the lowest possible Fc.

I've always used the one on the left in Carl's picture. I ordered that foam probably 10 years ago, the woofer measured very well with Fs below 20 Hz and I never took the chance to order any other. I've used the same on both types of woofers and it has measured very well everytime. Carl's advice is good and just happens to confirm that I did the right thing using the higher compliance foam in all applications.
 
Higher compliance foam in acoustic suspension systems is almost ALWAYS better. That's what Kloss was trying to achieve. The trapped air in the enclosure MUST dominate.

Doug
 
Doug G. said:
OK cool. :thmbsp: Didn't mean to sound kinda snarky.

Doug
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No snark taken. As soon as I submitted that comment, I read it and thought "Oh, that was clear as mud." I had to head out the door to help my daughter start moving out of school so I let it go. I was not at all surprised to see a comment on it. I can't help but chuckle over it.
 
Doug G. said:
I realize the typical user cannot measure the compliance of any given surround but he can judge by observing whether the surround can support itself or not. If you hold the surround by one side and it doesn't droop of its own weight, it's too stiff.

Let's be practical.

Doug
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I've never done the droop test but will give it a try.
 
I learned this lesson the hard way when I bought generic foam for my Boston A60s instead of the proper floppy filleted foam.

Instead of effortless bass at low volumes, you had to crank it up to get the same amount.
 
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