Major Contradiction, Can you replace foam surrounds with Rubber Surrounds on Speakers ???

Sure you can. They're yours to do as you please. Is it advisable? Probably not. Its part of the cone's suspension with different properties. Kinda like replacing a Ferrari's suspension. That can be done too. Will it be better? Probably not, especially since the mfg spent time researching the best suspension materials.  I'd stick with the OEM.

Then proceeded to call the well regarded Miller Sound in PA, who is recognized to one of the best in the Industry to do the replacing of speaker surrounds.

You got some GREAT advise from a professional rebuilder, why are you asking.

You got some generic advice from a rebuilder who probably did not consider how the product was used in application, in your specific model of speaker.

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Like I said, Twice NOW. the OP got some great advice from a professional builder.

dletch2, before you make comments MAYBE you should read a tad closer.

If you change the surround it WILL change the driver. There has been a few thread about getting Wilsons refoamed and they didn’t preform correctly. NOT CLOSE.. They were sent in AGAIN and refoamed to correct the issue.

As I recall it was behind not using WILSONs foams, they didn’t even go to different type.. It was the "Wilson" surround that DID make the difference..

Like timlub I’ve done a slough of VC/Cone swaps, Surround, hundreds.
Surrounds are kinda 101 for the DIY.

Unless you’ve listened to a surround swap, I just wouldn’t go there..

Get the surrounds from Wilson if you liked the performance you had.
Get the surrounds from someone ELSE if you want to change the sound..

BR will reduce the efficiency of the speaker.. Don’t believe, THEN READ..

A speaker manufacture will tell you just that.. Change the surround change the efficiency...
I do have some speakers with silicone surrounds.. Close in efficiency.

BR rubber is TOUGH, but not known for speed. Fabric on the other hand is probably the fastest and toughest.. Butyl Rubber works really well with high excursion drivers, Foams just won’t hold up.. Sense when did Wilson start using High Excursion drivers? Medium excursion and HIGH efficiency..

Happy Happy...

I like @artemus_5 analogy, and just to simplify it.

I called my local garage and asked if I could use Winter tires in the Summer, of course they said yes....

FYI - Wilson doesn't sell or do re-foaming, they use to suggest a third-party, but not sure if they do that now because that place has closed (orange county speaker repair). Lots of other places sell the re-foam kit though.

Keep in mind that just replacing the foam surround is only half the job. Best practice in most cases is to replace both the spider and surround. The spider is the more critical of the two suspension elements.

Keep in mind that many posting here...and even many repair shops don't really know what they're doing. The workmanship...or lack thereof..is evidence of that.

I believe, and this is foggy, that the answer is that the majority of the compliance in a driver is the spider on the inside, next to the magnet. The foam or rubber ring we see on the outside is normally the one that contributes the least amount.

I would agree with this.  The weight of the entire driver plus the weight and the "spring" strength of the spider will dictate the resonance frequency of the woofer.  This applies to port size tuning.  I don't think rubber/foam surround will affect the weight or spring/flex of the driver and have very little impact on resonance frequency.

Now the type of surround can definitely impact much higher frequencies (such as anything above 400-500 hz) because it affects the natural damping of the speaker vibration resonance.  This may have impact on frequency response or crossover design.  If it's a woofer on a 3-way speaker, then I wouldn't worry about replacing surround with rubber.