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-   -   SA-8 v.3 In Development : Getting Close ! (https://forum.realmofexcursion.com/sundown-audio/78081-sa-8-v-3-development-getting-close.html)

sundownz 10-27-2014 09:25 AM

SA-8 v.3 In Development : Getting Close !
 
Got my first prototypes in for the v.3 revision of the SA-8 -- it took quite a bit of consideration to figure out how to make some improvements to the design but I think we are on the right track :

http://www.sundownaudio.com/misc/pro...s/IMAG1176.jpg
* Newly tooled surround with an improved shape / slightly bigger overall size... this is a new shape I have been testing with for a while that is a bit more linear than the old shape. It allows a small but noticeable amount of extra throw.

http://www.sundownaudio.com/misc/pro...s/IMAG1177.jpg
* We removed the vent ring to reduce the total depth by 10mm -- since this reduces the cooling capability a bit we added gap vents (next photo). I did use appropriately sized drilled vent holes to maintain a degree of pressure in the under-spider cavity to help push air to the gap vents and keep velocity high. I tweaked and tuned the vent hole size on the SD-2 8" model already.

* A second but major benefit is this will help improve QC pass rates by reduced spider to top plate distance; thus reducing the chance for coil tick (fewer yard sale units thus steadier inventory).

* The magnet stack increased to 50mm from 40mm -- and we reduced the back plate from 25mm to 15mm (removed the 10mm bump) to keep overall motor depth the same. A marginal increase in BL will be seen.

* New magnet boot isn't tooled yet but will be for production.

http://www.sundownaudio.com/misc/pro...s/IMAG1178.jpg
* It's a tight fit in this motor due to the thick shorting ring... to get the surface area I wanted I used 16 gap vents @ 2.5mm each as wider vents wouldn't fit between the pole and shorting ring. Also each vent is flared to keep the flow quieter.

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There are a few other tweaks to the way the suspension goes together, standard XL leads, and a few other little tricks in the motor that you cannot see -- all in all should be a nice little upgrade to the SA-8 driver.

I still need to tweak the stiffness a bit as it ended up a bit too stiff on the first two prototypes... so that is still under-way. I expect them to come out some time around the end of the 1st quarter next year (so end of March or so). Until then the v.2 will be in full stock and shipping as normal.

sundownz 10-27-2014 09:53 AM

Re: SA-8 v.3 In Development : Getting Close !
 
Woops... brain fart it's actually only 5mm total shallower -- too many protos on the mind! Still a small reduction :)

Took a photo side by side to show the surround difference too:

http://www.sundownaudio.com/misc/pro...s/IMAG1181.jpg

http://www.sundownaudio.com/misc/pro...s/IMAG1182.jpg

sundownz 11-11-2014 12:50 PM

Re: SA-8 v.3 In Development : Getting Close !
 
I measured a production v.2 and a newly re-built v.3 with the final compliance side-to-side with the same amount of play time (neither is fully broken-in). Just to compare... looks like we nailed the stiffness based on FS... and we see a drop in Qts due to the higher BL (also higher sensitivity) :

http://www.sundownaudio.com/misc/pro...s/IMAG1185.jpg
BL^2/RE = 70.17

http://www.sundownaudio.com/misc/pro...s/IMAG1243.jpg
BL^2/RE = 85.78

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I don't trust the Woofer Tester as an "end all be all" of spec measurement either so don't read too far into it... but comparing on the same day back-to-back I can tell if my design goals are being met :)

The spec on our web-site for the SA-8 v.2 was done with a Klippel machine after full break-in for reference.


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