The Headcase Stax thread

[spritzer]

Yup, that's 120V. 

[Nifrigel]

Did anyone try making custom pads for the SR-007? I'm glad to share the experience.

 

I own the SR-007 SZ1 with heavily used brown pads. At first I wanted to buy modern (black) STAX earpads per Birgir's advice, however they are pricey, especially if you take into account the shipping cost from Japan to Russia. So I decided to ask the local guy (nickname snorry on the Russian forum) to make custom earpads for my SR-007. This guy is experienced in modding planar magnetic headphones (he even built some nearly from scratch) and he also has the necessary measurement equipment.

 

First of all, the grills were removed from the earpads.

The grills turned out to have strong windage and very poor permeability. Try to blow through it keeping your hand behind it and you won't feel any air coming through. On one hand, it isolates the membrane from reflections, on the other hand it supposedly degrades microdynamics and conceals everything above 10 kHz. We decided to change the grills with more transparent ones, that according to snorry already proofed itself to be useful in his planar magnetic projects.

 

Different materials and forms were tried. Here's what I've decided to stay with.

The form remains roughly the same, however new earpads are more rigid, they don't flatten on head unlike the original ones. Because of this they keep the driver slightly further away from the ear while sitting tight and comfy. This slightly improves the bass. The notch is oval, this form was chosen experimentally for its most balanced FR. Velour strips were added to the internal side of the earpads to reduce reflections of high frequencies.

 

Here is the measurements.

Old earpads:

Note the channel imbalance, it's caused solely by the earpads. No doubt, not every single pair of brown MKI pads out there are as terrible as mine, however that's what I got.

 

New earpads:

The channel imbalance is gone, the bass roll-off is more gentle and there is no midbass emphasis anymore. HF now go well beyond 10 kHz. The second-order harmonics level is slightly lower than before.

 

There was also a more SR-009-like variant with a little peak near 1 kHz:

This forwards the vocals a bit, however I prefer mids to be flat.

 

I want to thank Birgir who strongly advised changing the earpads. That really helped to make already great headphones ever better.

[Hopstretch]

Quality!

 

Do you have a picture of the headphones with the new pads installed, please?

[spritzer]

That is very cool indeed!! 

[Nifrigel]

Here are some pictures. Unfortunately, when in comes to photography I have neither equipment, nor skills.

[Tachikoma]

That's neat, have you tried just replacing the foam in your old earpads?

 

I think taking the springs out of the old earpads improves both the HF and LF response (possibly by improving the seal), and I see that you aren't using them with your new earpads. Is there any change in the soundstaging with the new earpads?

[n3rdling]

Nice mods

[nopants]

pretty interesting work, it sounds like we stone agers using the standard pads can just swap the cloth grills to get some of the benefits

 

I'm a bit hesitant at the thought of exposing the driver to more dust though

[Tachikoma]

Some people have advocated using legging socks to replace the grill material.

[Dusty Chalk]

You maniac, you took measurements and everything!

[kugino]

a few more questions about this 717 amp that i bought used...i'm wondering if i should return it b/c it's a bit more worn than was stated...and the L/R volume doesn't seem to work.

 

so, the casing is bent in a couple of places. the top cover has a bit of a dent, which i can live with, but the back casing is curved inward a bit, leading me to believe it was dropped or something:

 

 

the 717 has independent L/R volume knobs, i believe, and they should sit flush with one another (at least from what i've seen in other pics online). on this unit, the L/R knobs cannot sit flush with one another -  the inner L knob is recessed and cannot come out any further. looking at the internals, the plate is crooked near the potentiometer and perhaps this is causing the inner L ring/knob to be recessed. furthermore, when i turn the L ring, nothing happens. turning the outer R knob increases/decreases the volume together, but i cannot control L and R independently. is this an easy fix or something more problematic?

 

 

 

any thoughts? should i return to the seller and get my money back? or are these minor things that can be easily remedied? thanks!

[Tachikoma]

I've heard of the knob coming off too easily in these amps, but never a case where the "inner knob" won't come out. It sounds like it was dropped and that somehow bent the potentiometer.

[arnaud]

The more I read about these pad mods here and there and from the little experience I had making acoustic simulations of stat drivers, the more I get convinced that half the baffle is in the quality / design of the earpads than transducer / housing assembly?! 

 

How did you measure the headphone response / how was the compensation curved derived if I may ask? The flat baffle measurement rig I was working on was great to compare different phones together but getting a good seal wasn't easy (which would show as much deviation between trials as your L/R ear old pads) and I certainly would not get a flat curve with the SR009 or Omega 2 like you get here.

 

cheers,

arnaud

[spritzer]

The volume knob is press fit for the front half but the back is fixed with a grub screw.  Take off the front panel and you can access the screw and fix it in place. 

 

The rest is all shipping damage but Stax amps are very easy to damage in this way.  Flimsy aluminum that needs to be supported properly. 

 

The more I read about these pad mods here and there and from the little experience I had making acoustic simulations of stat drivers, the more I get convinced that half the baffle is in the quality / design of the earpads than transducer / housing assembly?! 

 

How did you measure the headphone response / how was the compensation curved derived if I may ask? The flat baffle measurement rig I was working on was great to compare different phones together but getting a good seal wasn't easy (which would show as much deviation between trials as your L/R ear old pads) and I certainly would not get a flat curve with the SR009 or Omega 2 like you get here.

 

cheers,

arnaud

 

The baffle is the crucial aspect of all dipoles so the pads are indeed a part of it here.  Well that would also include the head as this is a sealed baffle design. 

[chinsettawong]

But, the JK Float style headphones sound pretty good even without any seal.  There is plenty of bass too.

Edited April 21, 2015 by chinsettawong

[spritzer]

Well articulated bass it is not, more in the boom, boom style of the King Sound. 

 

What they did though is to move much more air to make up for the baffle or rather lack-thereof. 

[drp]

Kugino wrote: "Any thoughts? should I return to the seller and get my money back?"

 

Return to seller and buy one of the project-cased versions of the KGSSHV on Birgir's website for the low price of 2K plus shipping. You'll be happier, and more importantly, your 007s will be happier.

 

For my HV, it took longer to unwrap his mondo packaging than it did to set up the amp; better chance of it getting to you safely.

[nopants]

maybe I should buy one of Birgir's amplifiers so I can reuse the packaging as a bomb shelter

[kugino]

 

Kugino wrote: "Any thoughts? should I return to the seller and get my money back?"

 

Return to seller and buy one of the project-cased versions of the KGSSHV on Birgir's website for the low price of 2K plus shipping. You'll be happier, and more importantly, your 007s will be happier.

 

For my HV, it took longer to unwrap his mondo packaging than it did to set up the amp; better chance of it getting to you safely.

 

haha...yeah, believe me, i've thought about it. still might, though i've opened up the 717 and figured out what's going on with this thing. man, i'm not sure what happened to this amp, but there are a lot of dented and bent places in the casing. but from what i can see/hear, the electronics are perfectly fine, so i'm going to see if i can straighten out some of the casing and will probably keep it as it was a pretty good deal. if anything, it would be a great second amp for the living room or office if/when i decide to pick up a kgsshv in the future.

 

for example, check out the front plate. how the hell did this get bent like that?

 

[nopants]

I like the layout of the inside, certainly some ideas for future builds

[John Buchanan]

Ouch!

[luvdunhill]

Now where did I put those ISA motherboards ...

[rx79ez08]

That is an impressive amount of force.

[spritzer]

It will take a lot of work to make that right.  I'd just return it as so much of the resale value is gone.  This isn't a Cavalli amp after all... 

[kugino]

i just contacted the owner to ask for a refund. i imagine he might hem and haw, but hopefully paypal will help make it right. after i readjusted the L/R knobs they didn't track very well. at low volume levels the L side was louder, but as i increased the volume, the R side got louder...so they increased/decreased at different rates. we'll see what happens...stay tuned...