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Advent masonite frame woofer foam recommendation

spkrdtr

spkrdtr

spkrfixer
I do many refoams as part of my business and have access to speaker parts from the nation's largest speaker parts distributor who only deals with folks 'in the trade'.

The supplier offers two different foams for OLA woofers. One for the masonite frame and another for the metal frame woofer. During a recent refoam job on a pair of masonite woofers, I found what the customer gave me to 'fix' actually was a fairly new refoam job done with what appears to be the foam the distributor sells for that woofer. Before stripping the foam from the frames, I ran some WT2 tests to measure the Thiel/Small parameters.
I then installed the foams I normally use for the masonite frame woofer which are the same ones used for the metal frame woofer. Upon completion, I ran a second set of WT2 tests and found what I had suspected all along and that was the compliance was significantly increased with the use of the metal frame foams. Those foams fit both woofers but the Masonite foam sold by the distributor doesn't fit the metal frame woofer very well due to it's very narrow outer ring glue surface and that foams relatively wider outer glue ring.

Free air resonant frequency (Fs) of the 'bofore' woofers averaged 25 hz. The 'after' Fs averaged 18 hz. Now, that doesn't seem like much (-7 hz) when you consider the expansiveness of the 20-20,000 hz freq. range, but when you consider the reduction as a % of the 'before', it is quite significant at -28% which will result in improved bass extension over the 'before' foam.

So, for those planning to DIY refoam their masonite frame OLA woofers, I strongly suggest you opt for the metal frame woofer foam. I'm sure the internet sellers of OLA foams have both in stock, but would probably sell you the 25 hz foam if you simply told them you needed foams for the masonite frame woofers because that is what they are sold from probably the same distributor I buy from.

BTW, I don't sell foam.

Below is a pic of the two foams side by side. it's easy to tell them apart. Also note the slightly larger inside roll width (5/8 inch) on the metal frame foam vs the 9/16ths inch widt on the masonite frame foam.
 

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Can't we select the foam based on color? Seems the Masonite foam is a charcoal gray and the metal frame is closer to black.



More seriously, thanks for the info and running the tests.
 
I didnt know they sold different surrounds for the metal frame vs the masonite ring. The guy i bought mine from (rick cobb) sells the same foam for both
 
18 to 25 hz. is about half an octave. No small peanuts in the low bass frequencies.
From the picture the wider foam seems more translucent. Could it be because it's lighter/thinner than the narrow foam?
 
Blue Shadow said:
Can't we select the foam based on color? Seems the Masonite foam is a charcoal gray and the metal frame is closer to black.



More seriously, thanks for the info and running the tests.
Click to expand...

I wouldn't go by color alone to specify. Request "the metal frame foam that's the dark color with the narrow outer edge".... :-)
 
valvenator said:
18 to 25 hz. is about half an octave. No small peanuts in the low bass frequencies.
From the picture the wider foam seems more translucent. Could it be because it's lighter/thinner than the narrow foam?
Click to expand...

The foam on the right is lighter in color and not nearly as supple as the metal frame foam on the left.
 
spkrdtr said:
And which of the two I showed does he sell?
Click to expand...


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Im not sure. Here is a picture of it. Looks like the wider one (roll i mean)
 
spkrdtr said:
Below is a pic of the two foams side by side. it's easy to tell them apart. Also note the slightly larger inside roll width (5/8 inch) on the metal frame foam vs the 9/16ths inch widt on the masonite frame foam.
Click to expand...
That doesn't make any sense, Carl! The roll width should be the same for both woofers, and the surround on the right would be the right one for both. Maybe MWA found the surround on the left to be more desirable for the metal frame woofers because the OD is already trimmed by the manufacturer to fit the narrow basket mounting surface. I've used the wide outer edge surrounds on many of the metal basket woofers with no problems. I would be a little surprised if Rapid Die and Molding couldn't make the same surround with the trimmed OD without having to make a different set of molds or trim tooling, but that might be the case.
 
spkrdtr said:
Those look like the metal frame foam type.
Click to expand...


Well thats good then. I didn't have a problem installing mine but i noticed the foams that were on them before were wider on the masonite side. I think mine had been refoamed at least once
 
I have been stressing the importance of the correct compliance and roll size for a long time now. It doesn't matter for which Advent woofer a given surround is designated (other than the outer flange thing) as long as those two most important parameters are met.

High compliance (floppy) and 17-18 mm roll size to allow full cone excursion. It's amazing some of the surrounds sold allow anything less than 50 Hz to be reproduced considering the stiffness.

I have read time and time again from posters the surrounds they obtained "fit perfectly". That is only the beginning.

Some of the surrounds I have seen supposedly "correct" have been stiffer than any rubber surround I have ever seen. Foam surrounds were developed to get MORE compliance than rubber. Some manufacturers just don't know what they are doing or don't care.

Doug
 
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Doug G. said:
I have been stressing the importance of the correct compliance and roll size for a long time now. It doesn't matter for which Advent woofer a given surround is designated (other than the outer flange thing) as long as those two most important parameters are met.

High compliance (floppy) and 17-18 mm roll size to allow full cone excursion. It's amazing some of the surrounds sold allow anything less than 50 Hz to be reproduced considering the stiffness.

I have read time and time again from posters the surrounds they obtained "fit perfectly". That is only the beginning.

Some of the surrounds I have seen supposedly "correct" have been stiffer than any rubber surround I have ever seen. Foam surrounds were developed to get MORE compliance than rubber. Some manufacturers just don't know what they are doing or don't care.

Doug
Click to expand...

Sigh... rolls size is easily measurable. Compliance of a foam before installation is not for the DIY'r. There is a test standard for measuring compliance written by the Loudspeakers Manufacturer's Association but it requires special test equipment. I have bemoaned this fact in prior postings.
 
My ears tell me I've got the right foam.:music:

If it's the wrong foam, I'm almost certain books would start sliding off of shelves and ceiling fixtures would rattle their way out of the ceiling.:yes:
 
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
 
rmoreau61 said:
My ears tell me I've got the right foam.:music:

If it's the wrong foam, I'm almost certain books would start sliding off of shelves and ceiling fixtures would rattle their way out of the ceiling.:yes:
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This doesn't make sense. If you have a better surround in an acoustic suspension system, books and ceiling fixtures would be MORE likely to vibrate.

Doug
 
Doug G. said:
This doesn't make sense. If you have a better surround in an acoustic suspension system, books and ceiling fixtures would be MORE likely to vibrate.

Doug
Click to expand...

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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