Must try MOD - Foam inside the stamped steel baskets - YES!

xschop

I'll disagree as this mod has changed my mind on building billet frame baskets with only 1/4" dia. cylindrical uprights.

If Polk designed the new Legend drivers with even cast frames, I'd own a set. As for me I've NEVER heard Najee sound as accurate on any of my older Polks, even the ChimeraPolks.

F1nut

VR3 wrote: »

I think you guys are over analyzing this one a little bit :-p

Understatement of the year.

xschop

Live a little F1, if I donate the 99 cent foam, would that help your apprehension?

48 spokes is a little daunting lol.

Gardenstater

Try it you'll like it! Is that simple enough? If anyone sees the Grinch Who Stole The New Mods in their neighborhood please report to the authorities (kidding!)

xschop

xschop wrote: »

Sorry F1, I've just begun. There's still performance to be had. I'll be relocating the terminal tabs next to remove them from the equation. I don't like them blocking the windows.

Didn't cost a dime, dremeled off tab rivet, cut an extra width insulator from the same .090" PVA foam, redrilled above basket 1/8" hole and 8-32 stainless machine screw. Then re-soldered leads to factory tabs after bending them downwards a bit. Windows are completely unobstructed and the leads pivot without any restriction.
Sorry for over thinking....

BlueFox

What do the red symbols mean?

Toolfan66

Wouldn’t it have been easier to just bend the tab up, and just pop rivet it back on? You could have put two small cuts next to each side of the tab where the radius is, this should make it easier to bend that tab up to your desired angle.. I’m just not sure if the leads would be long enough without re-soldering to the tabs like you did. But if by chance they were/are, no extra hole to drill, don’t have to cut off tab, and no soldering..


BlueFox: 14k plus posts, and you don’t know what those red marks are? You should turn in your audio card. 😂 it’s the positive side of the driver.. BTW, I was just teasing..

xschop

I tried that. The rivet doesn't let it bend correctly out of the window.

Bluefox, that's real special.

pitdogg2

BlueFox wrote: »

What do the red symbols mean?

🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️
🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️

Toolfan66

xschop wrote: »

I tried that. The rivet doesn't let it bend correctly out of the window.

Bluefox, that's real special.

My suggestion was to still take the old rivet out, make two small cuts, one on each side of the tab where you see the radius, this will help bend the tab up to your desired angle, and pop rivet the tabs on the opposite side, if the leads are long enough for you to do so. This would eliminate a few steps that you did, and might look a little better, but it all comes down to the leads..

Toolfan66

pitdogg2 wrote: »

BlueFox wrote: »

What do the red symbols mean?

🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️
🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️

Red symbol = Positive
Blue symbol = Negative


😃😀😅😂🤣

xschop

There was barely enough lead length to do it this way, I wanted to cut down the tabs that the leads are now soldered to, but no dice.

Jazzhead

I did this mod and am pleased with the results. To my ears it removes some "smear" from the music, resulting in greater resolution/detail in the midrange and lower frequencies. It's an instantly recognizable improvement, not one of those changes you make that takes time to sink in. Since the outer drivers on my original RTA-12's are already utterly, completely damped (a comb filtering mod) I was worried about going too far with the damping, but I'm not hearing that. However, I intentionally don't have a very large strip of Sonic Barrier behind the inner "unaltered" drivers. I'm guessing this mod does what's advertised - it mitigates the sound bouncing inside the baskets which corrupts the primary soundwave coming from both the front and rear of the driver (sort of like diffraction?) Doing the mod is tedious, but once you get rolling, Dremeling tabs and cutting/placing the foam (I used 1/8 in.) isn't too bad. I did mine in front of the cabinets (on a bar stool) without unsoldering them (a time saver). For those of you with many more midwoofers to "treat" my sense is that if you can muster up the endurance you will be rewarded.

One question for those of you that would know - does an improvement in midwoofer performance (such as above) result in a corresponding improvement in PR performance? My sense is that the lowest frequencies were benefiting as well.

Gardenstater

Thanks for keeping an open mind and giving it a try and I'm glad it worked as well for you as it has for me! I too noticed an improvement in bass but I did not report it because I was halfway thinking it was still that I was not used to the effects of xschop's semi rings and I also was not so sure the Armacell would absorb low frequencies so well.

It is plausible that to whatever extent it does reduce those reflections, it will help clean up the MW cone movements in those frequencies as well, but it may make the backwave transmission to the passive a wee bit more coherent. Some of the reflections inside the basket can come back and hit the cone, but some of them can also escape through the windows with a time delay and phase change, thus muddying the passive behavior. Just a theory.

We know that open cell is a better absorber of sound in general but closed cell (like the Armacell) may have equal or better performance in the lower frequencies, on an equal thickness basis. Still researching that and info is scant.

gp4jesus

To those that need a little more confirmation - it WORKS!

I got to hear George’s system w/ one modded and one unmoved channel - THIS IS a simple, VERY inexpensive, worthwhile mod.

Armacell is closed cell? Please suggest an open cell product for this mod?

Side note: I can’t recall any discussion of open versus closed cell foam from my July ‘21 visit. I’m not questioning the validity of the same - it makes SENSE. Closed damps the physical. Open absorbs or damps sound.

Do this to all shielded drivers to damp the riiiiinging shields…

https://us.v-cdn.net/5021930/uploads/editor/6z/i11syvrozytc.jpg


Thank “G!” Tony

Gardenstater

Cool Tony! Now put some on the inside When you can find time that is

Rob used 2mm "Silly Winks" foam sheet from Hobby Lobby, which he believes is an open cell. Had to be applied with a thin layer of PowerGrab to ensure longevity, which may help damp the basket some.

Edit - I believe this is what he used @xschop

https://www.hobbylobby.com/Crafts-Hobbies/Basic-Crafts/Craft-Foam/Black-Self-Adhesive-Foam-Sheet---9"-x-12"/p/28642

OR?

https://www.hobbylobby.com/Crafts-Hobbies/Basic-Crafts/Craft-Foam/Black-Foam-Sheet---12"-x-18"-x-2mm/p/28626

I used the 1/8" Closed Cell Armacell which is marketed as heat insulation tape for piping:

https://www.homedepot.com/p/Armacell-2-in-x-30-ft-R-1-Foam-Insulation-Tape-TAP18230/100539553?keyword=armacell+gasket+foam+tape&semanticToken=21300000111_2019112209124893870_bbbn+21300000111+>++cnn:{0:0}+cnr:{7:0}+cnd:{4:0}+cne:{8:0}+cnb:{0:0}+cns:{5:0}+cnx:{3:0}+st:{armacell+gasket+foam+tape}:st+oos:{0:1}+br:{armacell}:br+rt:{gasket+foam+tape}:rt+dln:{553329}+qu:{armacell+gasket+foam+tape}:qu

PS: It might be something for some *intrepid* soul to try; a composite of this foam over the Armacell, giving around 5mm total thickness. I would bevel the edges near the window and surround with scissors prior to installation. Wouldn't be a bad idea to do an adhesion test for a while to ensure long lasting adhesion and this is pure experimentation here.

gp4jesus

If the adhesive on the foam is “iffy,” try contact cement or Tri-tix rubber cement. I’ve used contact cement w/ great success to Armacell interior closure walls, driver baskets, and magnet shields

Gardenstater

Thanks I will try that if mine ever fall off with only the Armacell PSA. So far it has been 6 mos. on one and 7 mos. on the other. The Armacell is light as a feather.

Gardenstater

@Jazzhead I meant to ask you what 1/8" thick foam did you use?

I did some measurements to the best of my ability with what I had I had to measure with, and for the closed cell Armacell I got 0.1345" thick and 4.6 lb/cu ft density.

Anyone wanting to experiment with alternative foams could use that as a reference point.

As far as open cell goes I found some Microcellular Polyurethane stuff at Grainger that is twice the density (10 lb/ cu ft) that might be interesting to try out. One thing that comes to mind with open cell is that it might not be any different in performance to the closed cell if it has a skin on it (could be sanded off??).

https://www.grainger.com/product/USA-SEALING-Open-Cell-497J78

Another option would be to stick with closed cell but go even lower density than the Armacell. This closed cell EVA at 2 lb/ cu ft might be something to try:

https://www.grainger.com/product/USA-SEALING-Water-Resistant-Closed-Cell-497K02

Jazzhead

I used some 1/8 inch self adhesive pipe insulating foam that I had around. It is closed cell and has a rough texture on the non-adhesive side.

Gardenstater

Thank you! So may or may not be Armacell. If not, probably something very close.

gp4jesus

Jazzhead wrote: »

I used some 1/8 inch self adhesive pipe insulating foam that I had around. It is closed cell and has a rough texture on the non-adhesive side.

Gardenstater wrote: »

Thank you! So may or may not be Armacell. If not, probably something very close.

I’ve used Pipe wrap* and Armacell. Pipewrap is stickier than Armacell. Pipewrap looks and feels like Armacell. Can’t say about the thickness or sound absorption but takes care of magnet shield ring.
* on my shelf

Jazzhead

I don't think what I used was Armacell, however it got the job done.

Gardenstater

Gardenstater wrote: »

Tony M wrote: »

I have seen some cast baskets that have thinner spokes. I wonder if that was done for this topic of reflections.

I think so no doubt. This patent is old and expired and anybody can do that now.

Just some confirmation @Tony M

SEAS Prestige Titan H1869-08 / L16RNX3 6" Aluminum Cone Woofer

L16RNX3 is a High Fidelity woofer with an injection moulded metal chassis, intended for bass reflex and closed box designs.

Optimized cone design combined with the stiff and light weight aluminium gives a high break-up point to allow for easier crossover design and wider bandwith than common aluminium cones.

Titanium voice coil former with a very long copper coil winding and a bumped back-plate for excellent force transfer, transient sound reproduction and large linear excursion.

A heavy copper ring below the T-shaped pole piece reduces non linear and modulation distortion.

Extremely stiff and stable injection moulded metal basket keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum.


https://www.madisoundspeakerstore.com/approx-6-7-woofers-seas/seas-prestige-l16rnx3-6-aluminum-cone-woofer-h1869-8-ohm/

Hansvelton

F1nut wrote: »

VR3 wrote: »

I think you guys are over analyzing this one a little bit :-p

Understatement of the year.

You sir are totally discounting the boredom of Covid Lifestyle....

Hansvelton

Toolfan66 wrote: »

My only issue with this mod is if you end up not liking it, it would be a major pain to reverse, if at all possible to reverse. Also doing 16 drivers doesn’t sound like fun at all..

I’m glad you like your findings, and having fun doing it..

I agree, and also feel that if the speakers were ever up to be sold, I would have to disclose that I put all that "Stuff" all over the drivers and and convince someone not that it does good, but that is does no harm....

Gardenstater

Those who are skeptical such as yourself, should simply wait for more people to do the mod and report back. There are only 3 of us now, and who knows, we may be suffering from confirmation bias or something 🤣

xschop

Sounds like a new magazine's on the horizon.... Audio Skeptic.

Gardenstater wrote: »

Those who are skeptical such as yourself, should simply wait for more people to do the mod and report back. There are only 3 of us now, and who knows, we may be suffering from confirmation bias or something 🤣

Gardenstater

Or The Pandemic Audio Skeptic because apparently modifying your speakers to sound better is linked to COVID somehow

xschop

...Chimeramods