[jaycalgary]

I have together and working pretty good. I didn't bother to paint them. I really wanted to hear what they would sound like. I recycled the old grills for now and just used hot glue to hold the wires. Hope they don't get confused for Grados. They are solid and it really shows in the bass department. The best way I can think of describing it is if a bass head headphone is like hitting with a rubber sledge hammer these ones are hitting like an iron hammer. The notes that should be finished are finished nothing fuzzy. Anything with strings or brass just sounds great but that seems pretty standard with the 407's. I think the treble is a bit hot though. They are loosening up the dustcovers are not as tight as they were when I got them. I will have a pair of O2 Mk1 soon and should be able to figure out more.
 

 
 
 

 

 

 

 
 

 

[edstrelow]

I can't tell from your pix but are the drivers mounted ahead of the ears facing backwards in other words like the true Sigmas or are they  beside the ear?

 

[chinsettawong]

NIcely done! 

 
How do you like the sound?
 
Wachara C.

 

[moodyrn]

From the pics, it appears they are facing the right way.

 

[John Buchanan]

Agreed. The 4th photo shows that without the mineral wool. Nice job.

 

[jaycalgary]

They are fairly close to the sigma shape but lower profile. The angle of the drivers are a couple degrees steeper. I think if I ever do it again I would go almost 90 degrees because I have the drivers a lot closer to the ears than normal sigmas. They go right through the aluminum plate the earpads are mounted on. So on the inside its less than 2mm to the driver dustcover. I will post a pic and you can see how it goes through the aluminum plate. I found the best insulating technique so far. I cut mineral wool against the grain at about quarter inch then insulated the first layer with lots of compression so its really tight. Then a 2nd layer on top that's loose and really porous. The other problem is with the plastic case and flimsy aluminum cover that Stax mounts the drivers in. I think they added a hollow boomy coloration by doing that. It might be the aluminum plate on the back. They left a nice sized ridge with a gap all around the driver that might be reflecting sound back in. Even so they sound really nice to me and really like the midrange. It is more forward than the O2's but more immediately likable. I just have a Srm-1/Mk-2 at the moment but am going to upgrade in the future. The O2's sure have major bass.
 

 

 

 

 

[jaycalgary]

I have really been throwing spaghetti at the wall just hoping something will stick and have some decent sound. I am sure I have been incorrect at more than a few things on this thread and much of it is trial and error. None of the ways I tried insulating with mineral made the drivers sound the way they should. I tried anything and almost everything and after getting the O2's came to almost giving up hope on them figuring the new drivers just won't work in the Sigma configuration. I probably would have been incorrect with that also. The problem seemed to be with the drivers but other people have 407's and they like the sound. What gives then? There was only one thing I forgot about that makes my drivers different when they were 407 Lambdas. The fabric liner that was in the earpads. Very lucky I kept them and also very lucky they fit back in. I think Stax may have took them in consideration when designing and tuning these new drivers. Even in the 407's taking this fabric disc out probably changes the sound for the worst.
 

 

[edstrelow]

This is  a very interesting project because I think we really need to see what variations in the basic Sigma design will sound like.   What you really need is the ability to compare your phones with an existing Sigma Pro or Sigma/404.  I assume you do not have such a phone?  This would give you some clue as to what is the sonic effect or your shape modifications and how much mineral wool to use.

 

[edstrelow]

This is  a very interesting project because I think we need to see what variations in the basic Sigma design will sound like.  There is little or nothing out there in the way of a Sigma-type design to compare these with.    What you really need now is the ability to compare your phones with an existing Sigma Pro or Sigma/404.  I assume you do not have such a phone?  This would give you some clue as to what is the sonic effect or your shape modifications and how much mineral wool to use.  Are there any meets in your vicinity where this could be done?

 

[jaycalgary]

Well I agree and I find it a fun hobby to make the housing. I did have a pair of Sigma pro's not for long they needed updating to sound decent. A broken pair just sold on ebay
http://offer.ebay.com/ws/eBayISAPI.dll?ViewBids&_trksid=p4340.l2565&item=250863339302
I put a bid but glad I didn't get them. I think I am pretty close to bang on with the materials I have been using they are super stiff and I think that matters a lot. I was thinking the 407/Sigmas were a lost cause sound wise because when I would add enough mineral wool to make the bass ok the midrange would go bad. I just upgraded from a Musiland 02 soundcard  to a decent W4S Dac2 and so far it has been a game changer.  I can add enough mineral wool to have ok bass and midrange. Someday when I get them together nice and if the sound seems good someone can hear them and compare. I now have O2 Mk1's I enjoy quite a bit also.

 

[edstrelow]

DUPLICATE POSTING

 

[edstrelow]

That set on Ebay sold for $494.00 and it was being sold as defective for parts!  Either someone wanted to fix them as Sigma pros or they are also planning an upgrade.
 
Was there anything wrong with your Sigma Pro's or did you just not like the sound?
 
I have a set of pros as well as the Sigma/404 and  there are significant differences in the sound.  The Sigma/404 has somewaht more detail and bit more bass and treble. The Sigma pro has a more prominent mid-range.  Still the 2  have  a lot in common.

 

[moodyrn]

Still can't believe someone paid that much for a defective pair. I had a pair of normal bias I only paid 450.00 for. I know the pros command more but nearly 500.00 for a broken pair?

 

[TruBrew]

Yes, the prices are two high. I really want a pair but not at what people seem to want. There is a normal bias pair on eBay right now for 500GBP. I mentioned this on the other Sigma thread, but it seems more appropriate here. Actually, I am not sure why this thread is not in the DIY section, but no matter. 
 
Someone should try and more faithfully recreate the. Maybe the materials are the problem. I am sure with all the measurements taken, that someone could create a 3D model of the Sigma housing. Then a company like shapeways.com can build them for us. Or any 3D printing company for that matter. Shapeways is just the only one I know of. Just make an adjustment to the model so it accepts the new headband. Then you can buy a SR-404, and move it into the new enclosure. That would cut out a huge portion of the cost. 
 
Now, who is willing to try. If I was a DIY kind of person I would definitely be trying. I am hoping one of you will so that I can buy a pair from you. 

 

[ujamerstand]

Dude. That's exactly what I've been thinking too. I'm just worried that the shapeway plastic won't be rigid enough as we've seen back in a couple pages. Some structural analysis needs to be done.