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Stax SR-507 investigation


spritzer
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We all knew this was going to happen but I've taken the SR-507 I got less than 24 hours ago apart. :D Stax does warn about any and all tampering voiding the warranty so don't try this at home kids.

First off, lets remove those driver housings from the arc assembly (they just pull out like on the two other Lambda designs). Here are the 507 name plates:

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Now lest lift up the four corners of the earpads and remove the screws which fix the baffle to the back grill. The baffle just pulls out and we are greeted with this:

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Now this is very different from the other Lambdas, gone is the aluminum baffle with the driver glued onto it and now we have a molded plastic baffle with a cradle for the driver to sit in. I'm not sure what plastic it is but it is very stiff. Like I said above, Stax warns about the warranty being void if one tries to tamper with the headphones which would explain this:

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Now this just confirms what I thought as soon as I opened up the headphones, the drivers are not glued together but rather just stacked together inside the shell. This is how the SR-Omega is assembled, also the SR-007 and the SR-003. Throwing caution to the wind I remove those 4 screws:

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Here we can see the silicone o-ring used to seal the back of the driver and the new chrome look of the metal plate used to hold the dust cover in place. Now it's time to put my hunch to the test and see if the dust cover is glued to the stator:

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Indeed it is not though there is some compound used between them. This gives us a direct view of the stators which appear to be coated metal plates, similar to the newer stator design introduced in 1994 with the Lambda Nova Signature. Since I don't happen to have a clean room to do stuff like this I tried to keep the drivers uncovered for as short a time as possible. There are glue pads on the end of the driver so I decided not to mess with them and try my luck exposing the diaphragm. From the side view offered where the connections the diaphragm is still mounted to two solid brass rings like on all the other Lambdas.

Now we take a look on the other side of the driver. With the new earpad design this is quite simple, just use a knife to lift up the cloth cover and you can see the protective mesh:

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This is the same silver colored material found on the post 2004 models. The arc is also new and very substantial if a bit uncomfortable for somebody with a gigantic head like me.

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They need a lot of parts to make this one work and plenty of screws. None of the cost cutting seen in the post 1994 arc assembly here. Now they are back together and needless to say, they work perfectly. :)

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I wonder if the stack in the mold can get a decent seal and retain the diaphragms tension on the long run as the glued stack of the old lambdas could.. otherwise the whole thing looks pretty thought-out!

But what is the problem with the headband you mentioned? did they reduce the adjustable area?

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That looks much better to me than what was there before. If "none of the cost cutting" is there, I wonder if that isn't a sign Stax are doing well.

They are doing well and there is also the small matter of this being a rather expensive headphone...

I wonder if the stack in the mold can get a decent seal and retain the diaphragms tension on the long run as the glued stack of the old lambdas could.. otherwise the whole thing looks pretty thought-out!

But what is the problem with the headband you mentioned? did they reduce the adjustable area?

The stack is held firmly in place by the silicone o-ring so there will be no baffle leak. The diaphragm is fixed exactly like it is done on all the other Lambdas so it will not loose tension. On a normal Lambda the stators are just glued to the brass rings so the odds of a baffle leak is higher here since the glue does fail with age. I've split enough drivers in my day...

The arc now has fixed clicks and it is designed differently so instead of the headpad being in a C shape over the head and pushing towards the arc when worn, the new one has the headpad under more tension so it is almost flat. At the biggest setting there are about 30mm from the top of the headpad to the arc so it looks just a bit odd when worn... :palm: It isn't exactly fair to compare the fit of my well worn SR-404's or let alone my highly customized SR-007 but I do feel the SR-507 at all times. This might get better with more use or it might continue to annoy me.

So how does it sound?

Well it is a Lambda so the bass is slightly boomy, they are forward (though the BHSE does tame them a bit), the soundstage is a bit hazy and they present a bit of false detail which should be buried in the mix but isn't.

As it stands now they are a good Lambda but without having a SR-SC1, 404LE or a LNS here it is hard to say whether it is the best Lambda ever made. The brightness off the KGSS (with a rather dull source) does count against them but the lack of excessive bass boom is a welcome thing.

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No ground in electrostatics which is why Stax made a virtual ground in the SR-Omega for safety reasons.

I must say the 507 is growing on me with the APL/BHSE setup. It's no Omega in terms of soundstage, bass, midrange presence or detail retrieval but for the price it eats a HD800 for dinner and stands up to the HE60. Now the real test will be moving back to "budget amps" such as the 717, KGSS and SRM-1 Mk2. Hell I'll throw in the SRM-T1 and the small portables to the mix...

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Just glue them down with polyurethane and be sure to let it cure at room temperature for 24hours. I then apply a second layer on the outside of the drivers to make sure they aren't leaking. We are all about overkill... :)

As for the 507, I like them more and more which for me is the true mark of something great. Feed them a complex bass line and they do show their limitation but the lack of the "Lambda boom" is a very welcome thing. The midrange is more forward then a Omega but it is very similar to the HE60, with no etch or shouting. I've moved on to the SRM-1 Mk2 running balanced off the APL and it still sounds just lovely. I'm just letting Foobar run on random to try pretty much anything I can throw at them. I'm not quite ready to declare this the best ever Lambda but it is bloody close... :o

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And it is great that the SR-307 may well be nearly as good for much less (the pads probably make some difference though, cable should mean little). I guess the SR-207 does not use the same drivers like with the previous generation (despite looking more similar).

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Just glue them down with polyurethane and be sure to let it cure at room temperature for 24hours. I then apply a second layer on the outside of the drivers to make sure they aren't leaking. We are all about overkill... :)

See I thought laser cutting some pieces to essentially bolt the driver to the baffle was overkill. Though I may pick up some polyurethane tomorrow on your recommendation.

Also leaning more and more towards one of these newer lambda models as the reviews come in.

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Pressing the driver down with some thick lump of aluminum will probably hurt performance more than it helps since you will have to deal with unwanted reflections.

As for the new models, the SR-407 should be the best value of the bunch. The low capacitance cable, the old but very comfy arc assembly and at less than 40KYen they are hard to beat. That is if Stax didn't fuck something up that is...

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Probably it's just me but I don't find the newer arc comfortable as it doesn't allow to bend the cups enough. It was not a problem with the SR-404LE's leather earpads but it is with the normal pads. Luckily, I have a Sigma headband which I can use on the Signature/404, that's much more like it.

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  • 4 weeks later...
  • 1 month later...

I got interested in the new stax... Before SR-303 and SR-404 used to be the same headphone, just differing in the cable. The 202 used different drivers. When I look at the specs, I might guess that the 507 is basically the same as the 407 but with the newer chassis and better pads. Now if the 307 was just the 407 using the chassis we already know from 303 and 404, I'd gladly take the 307 since I liked the 303 in terms of comfort. Does anyone actually know more than my wild guesses?

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I'm not aware of anybody that has opened up any of the other new models. If I spot a good deal on any of the new models then I'll take them apart as well but with the Yen still strong this isn't likely to happen.

We also shouldn't assume that these all have identical drivers as the SR-404, SR-404LE and SR-SC1 all should have identical drivers yet don't sound the same.

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I for one think the extra money went into the earpads, cable and arc assembly so the 407 should have the same driver. I sold my 507 to a friend here so if I ever get one of the other sets comparisons will be easy.

I ordered a pair of these yesterday from "Elusive Disc" (last day of the 10% off sale). Hoping your sale had nothing to do with the quality of the 507. At any rate, I'll get to do a "head to head " with the SR-303's and the ESP-950's. They'll also get a chance to go up against the LCD-2. Winner stays, looser goes.

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I owned a 303 for several months but sold it in the end. A bit lacking in bass and a bit too strong in the upper midrange or somewhere in that region. Sounded too "audiophile" to me if you know what I mean. Maybe I'll try the 407...

The 303 was very similar to the 404 and both have the annoying midrange etch. On the whole they aren't bad headphones except for that...

I ordered a pair of these yesterday from "Elusive Disc" (last day of the 10% off sale). Hoping your sale had nothing to do with the quality of the 507. At any rate, I'll get to do a "head to head " with the SR-303's and the ESP-950's. They'll also get a chance to go up against the LCD-2. Winner stays, looser goes.

I sold them simply because I saw no need to keep them. I do like how they sound but the comfort is lacking for my gigantic head and my only reason for having a Lambda here is for testing amps. I already have a SR-404 that somehow sounds bloody great (could be a SR-SC1 with the stickers removed) and it was far, far cheaper than the 507. Selling it to a local friend only made the deal easier since I can always borrow them. :)

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