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Masonite frame woofer foam recommendation


Carlspeak

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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.

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.

post-100237-0-97365000-1429807383_thumb.

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Wonder if this is one reason I was so underwhelmed by the OLA (masonite ring) I restored. Used all top-quality components, including the new inductors Pete recommended but did not think they were as good as the AR-2ax.

Live and learn.

Thanks Carl.

-Kent

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...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 reduced with the use of the metal frame foams.

...

So, for those planning to DIY refoam their masonite frame OLA woofers, I strongly suggest you opt for the metal frame woofer foam.

Hey Carl,

I agree, and have been using the more compliant surround for both woofers for some time now. In fact, Larry/Vintage AR is now only sending out that version in his kits.

Roy

I agree with Roy that more compliant s/b better. Carl, did you misspeak when you said the 'metal-frame' foam has reduced compliance?

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...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 reduced with the use of the metal frame foams.

...

So, for those planning to DIY refoam their masonite frame OLA woofers, I strongly suggest you opt for the metal frame woofer foam.

I agree with Roy that more compliant s/b better. Carl, did you misspeak when you said the 'metal-frame' foam has reduced compliance?

Ooops, I DID misspeak! Correction made. Thank goodness for the SW keeping the post editing capability indefinitely. Some forums don't.

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Thanks to donQ and Carl for the correction - - I had been so confused reading the original post that I was unsure of which product was being advocated. Now, it is very clear that the more compliant metal foam is the preferred product, but is that the foam on the left or the right of the pic in post #1? Despite the excellent pic, the most obvious difference is the width of the outer lip.

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Thanks to donQ and Carl for the correction - - I had been so confused reading the original post that I was unsure of which product was being advocated. Now, it is very clear that the more compliant metal foam is the preferred product, but is that the foam on the left or the right of the pic in post #1? Despite the excellent pic, the most obvious difference is the width of the outer lip.

The left one is the metal frame foam.

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The quality/compliance of the surrounds really has nothing to do with the woofer style. There have been good and crappy ones made for each type of woofer.

The important thing is to get very compliant (floppy) surrounds so the only real resistance to cone movement, in free air, is the spider. The cone should move with very little force applied. When installed, the dominant restoring force must be the trapped air in the cabinet. That is the essence of an acoustic suspension system.

Doug

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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.

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.

Out of curiosity, I measured the foam ring on my NAL woofer, it measured to be 28/32" according to my ruler. The source is http://www.ebay.com/itm/170576806406?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Actually I did refoam several OAL and NAL using other suppliers before. I felt the bass was not as deep nor easy going as the more recent two pairs of NAL refoamed using the supplier mentioned in the link.

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Yes, Rick is a known reputable and knowledgeable suppier of surrounds. I have been recommending him for years. RSSounds was also good but I don't know if they are still in business.

Doug

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Out of curiosity, I measured the foam ring on my NAL woofer, it measured to be 28/32" according to my ruler. The source is http://www.ebay.com/itm/170576806406?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Actually I did refoam several OAL and NAL using other suppliers before. I felt the bass was not as deep nor easy going as the more recent two pairs of NAL refoamed using the supplier mentioned in the link.

Just out of curiosity I ordered a set of those foams from Rick Cobb. I could use a couple more anyway. They arrived today and I found they match up perfectly with the metal frame foam in my initial post. This further adds proof that the pros all buy from the same source.

My intent for the OP was to alert folks to the possibility of getting the foam in the right side of my pic from a supplier who doesn't know the difference and just orders by product application (i.e. metal frame or masonite frame). Assuming they order from the same supplier as Rick and I, then they could get the 'metal frame' foam from that supplier.

If you measure your foam on the bottom (convex) side, I think you'll find they measure 5/8 inch wide.

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"If you measure your foam on the bottom (convex) side, I think you'll find they measure 5/8 inch wide."

I will take your word for it. I already had the foam installed so I could only measure the top side. Good to confirm I also used the same foam surrounds that would maintain the performance of these excellent Advent woofers.

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"If you measure your foam on the bottom (convex) side, I think you'll find they measure 5/8 inch wide."

I will take your word for it. I already had the foam installed so I could only measure the top side. Good to confirm I also used the same foam surrounds that would maintain the performance of these excellent Advent woofers.

Yes, you made the right choice and R. Cobb is very well regarded on many forums.

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