Mission 707

[flyingtele]

I just bought a pair of Mission 707's needing a refoam for about $6, needless to say I was well happy with my purchase.
However, upon removing the woofers, I noticed that one of the cones was stuck, and then saw the magnet was cracked through its centre, so that speaker must have been dropped from a height.
So my plan is to find an old junk speaker that has a ceramic magnet of the same dimensions, dismantle the magnet assembly of both drivers and install a new magnet. Then carry on with the re-foam. I will make a post when I have the bits to repair the driver. Most people would chuck the old one out and replace it if it needs a new magnet, but I enjoy repairing things even if its not the easiest or most economical method, due to personal enjoyment and knowledge/experience to be gained.

But, that's not what this post is about. Something peculiar that caught my attention was the design of the front firing port used. Rather than a conventional port/vent with a duct, its some sort of plastic plug with many holes of much smaller diameter, much like a honeycomb but with round tubes rather than hexagonal.
Im assuming that many small ducts would tune the cabinet to the same freq. as a single duct of the same lenght and with an equivalent mouth area, but what was the idea behind it?
Anybody know if it was some special design feature or more likely the designers trying out a new concept? I dont have my camera to hand, but will post some more detailed photos when I can.

They look to be a decent well made speaker, looks as if they use a Vifa D19 tweeter re-branded as Mission, and have an 8" mid/bass. Cabinet has thick and well braced plastic/composite front and the rest is simply thick particle board. Anyone have any experience with this model?

[seagrasser]

This was said about the 770's that employed a similar port design. Seems like a way to get away with a smaller port diameter.

"A stylistic as well as performance related update to the design was the use of a cellular port instead of the rather crude 'tunnel port' of old (through which one could clearly see the acoustic wadding inside). The principle of the cellular port design is to reduce turbulence and the characteristic 'chuffing' sound of ports as the air mass inside them is excited."

[seagrasser]

By the way, your magnet idea needs to take into account a lot of variables including gap height and voice coil diameter which are fairly specific to a particular woofer design. Might be better finding a replacment driver with a rotted surround and repairing the surround.

[Inductor]

Originally Posted by flyingtele

...
Im assuming that many small ducts would tune the cabinet to the same freq. as a single duct of the same lenght and with an equivalent mouth area, but what was the idea behind it?
Anybody know if it was some special design feature or more likely the designers trying out a new concept? I dont have my camera to hand, but will post some more detailed photos when I can.
...

No, actually is not the same. When the ducts get small in diameter it affects the overall in a different way. ("French" formula)

[flyingtele]

Originally Posted by seagrasser

By the way, your magnet idea needs to take into account a lot of variables including gap height and voice coil diameter which are fairly specific to a particular woofer design. Might be better finding a replacment driver with a rotted surround and repairing the surround.

Maybe I didn't explain it as well as I could have, I intend to use the original top plate and pole piece, all I would be replacing is the ceramic magnet part itself. Not a complete magnet assembly off another driver, but rather just the magnet material itself. I am able to dismantle and re-assemble magnet assemblies with 'live' magnets, so the only hard part really is finding a donor of the same dimensions. Most important dimension is the height, but it shouldn't be too hard to match it up to another driver.