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Fostex T50RP Incremental Mods and Measurements - Page 120

post #1786 of 1796
Quote:
Originally Posted by Armaegis View Post
 

 

I was going by the assumption that we weren't going to be messing with atmospheric conditions enough that we'd have to break out the ideal gas law :tongue: (though I suppose one could figure out how to implement underwater listening if that would improve the listening experience somehow... maybe sulfur hexafluoride would be easier)


Nitrogen bleeding pads, of course.:)

 

The point being that modding takes on a very few complexions if you pull back and look at it as a system. Acoustic reflection or absorption, or changing the medium density whether it be with cotton (ick) or some more resilient material or by increasing pressures before or after the driver. In essence, actually tuning a driver relies on being able to alter the speed that sound travels. 

post #1787 of 1796

I'd agree with you in the area of the cups with all the stuffing and damping and voodoo, but in that extremely small range that the waveguides are acting, I don't think it's a factor (I could be wrong though?)

 

I do foresee an issue of coherence. The profile of each hole (which I'm mentally treating as mini-horns) changes how much volume of air the driver at that point sees. If there are holes with different profiles, then the loading changes a little bit across the holes which I think would lead to higher distortion.

post #1788 of 1796
Quote:
Originally Posted by Armaegis View Post

I'd agree with you in the area of the cups with all the stuffing and damping and voodoo, but in that extremely small range that the waveguides are acting, I don't think it's a factor (I could be wrong though?)

I do foresee an issue of coherence. The profile of each hole (which I'm mentally treating as mini-horns) changes how much volume of air the driver at that point sees. If there are holes with different profiles, then the loading changes a little bit across the holes which I think would lead to higher distortion.
but like I said before. Doesnt that already happening because of more active area of centre of diaphragm? Also I think that such wide horns/funnels will overlap each other and will look like those guides with sharp spikes between vents. There was one design in G series with wider geometry (mostly to compensate longer gaps between vents 2.5mm and 3.5mm)
post #1789 of 1796

Nice brainstorming and discussion here. But hopefully someone just makes open source .

post #1790 of 1796
Quote:
Originally Posted by ZGLISZCZ View Post


but like I said before. Doesnt that already happening because of more active area of centre of diaphragm? Also I think that such wide horns/funnels will overlap each other and will look like those guides with sharp spikes between vents. There was one design in G series with wider geometry (mostly to compensate longer gaps between vents 2.5mm and 3.5mm)

 

Even though the driver flexes more in the middle, at least the air resistance is consistent across the surface. If you change this, it's basically like adding an extra force acting on the surface which will add distortion. (or maybe I'm just talking out of my rump)

 

I think sharp spikes between vents is fine... or rather, as long as the geometries permit the waves from each hole to merge cleanly with its neighbour, that's what matters. Maybe that works with spikes, maybe it works better with an added round taper, maybe it needs some felt in between, I'm not sure.

post #1791 of 1796
Quote:
Originally Posted by Armaegis View Post
 

 

Even though the driver flexes more in the middle, at least the air resistance is consistent across the surface. If you change this, it's basically like adding an extra force acting on the surface which will add distortion. (or maybe I'm just talking out of my rump)

 

But doesn't all that felt (and other materials) dots in the centre that I can see on various mods work this way? BMF concept was relatet to some sort of "hump" shape in the centre, I probably messed up this concept on my guides;) but he was saying that he tested that and it did work for some reason. anyway I agree with you that most safe option is with same geometry for each vent. Also thanks to all you guys that started discuss this. Soon first printed pairs of G series should arrive, it might put some light on that.

post #1792 of 1796
Quote:
Originally Posted by ZGLISZCZ View Post
 

But doesn't all that felt (and other materials) dots in the centre that I can see on various mods work this way? BMF concept was relatet to some sort of "hump" shape in the centre, I probably messed up this concept on my guides;) but he was saying that he tested that and it did work for some reason. anyway I agree with you that most safe option is with same geometry for each vent. Also thanks to all you guys that started discuss this. Soon first printed pairs of G series should arrive, it might put some light on that.

 

Maybe a coincidence, but I've never liked putting dots* on the drivers. While it could objectively make the FR seem flatter, something always felt off to me. Perhaps due to distortion? Or maybe I'm drawing imaginary lines to support my notions :cool:

 

*the non-permeable kind. Soft breathable materials are different and I think act more as filters rather than affecting the acoustic compliance.

post #1793 of 1796
Alright, so I think I'm going to make the jump and build a measurement rig. I was thinking of seeing if I could ship my cans to BMF to measure, but then I'd have no good cans, and I would probably shrivel up and die inside before they came back.
There seems to be a significant imbalance from left to right. I found part if it was volume, for some reason my computer makes the left louder, and then the Schiit stack made it worse. Much in that was an easy fix, just lower or raise the volume in respective channels. But there still is a bit of separation issues, and just seems off.


Besides shipping to where BMF is from me would be more then the rig as a whole anyways.

After reading the tutorials, seems actualy much easier then expected. One problem is that the mic used is discontinued, available on eBay of course. But I think I found a decent enough replacements. Both recommended by digikey to replace the Panasonic

http://www.digikey.com/product-detail/en/0/668-1453-ND?CSRT=3822134383143723175

Ther other one is pretty much the exact same, $4 cheaper, but the sensitivity on the cheaper one is +/-4db, vs the more expensive one is -35db period apperently
post #1794 of 1796
Thread Starter 
Quote:
Originally Posted by SeEnCreaTive View Post

Alright, so I think I'm going to make the jump and build a measurement rig. I was thinking of seeing if I could ship my cans to BMF to measure, but then I'd have no good cans, and I would probably shrivel up and die inside before they came back.
There seems to be a significant imbalance from left to right. I found part if it was volume, for some reason my computer makes the left louder, and then the Schiit stack made it worse. Much in that was an easy fix, just lower or raise the volume in respective channels. But there still is a bit of separation issues, and just seems off.


Besides shipping to where BMF is from me would be more then the rig as a whole anyways.

After reading the tutorials, seems actualy much easier then expected. One problem is that the mic used is discontinued, available on eBay of course. But I think I found a decent enough replacements. Both recommended by digikey to replace the Panasonic

http://www.digikey.com/product-detail/en/0/668-1453-ND?CSRT=3822134383143723175

Ther other one is pretty much the exact same, $4 cheaper, but the sensitivity on the cheaper one is +/-4db, vs the more expensive one is -35db period apperently

I tried those PUI mics when Panasonic discontinued the WM61-A. They measure very differently. Not a problem once you determine the offsets or compensation / corrections And measure relative to your own measurements only.

Check the ebay seller I recommended in FIMM. They're authentic and cheap. If he's out, PM me and I'll send you a couple.
post #1795 of 1796
Quote:
Originally Posted by bluemonkeyflyer View Post


I tried those PUI mics when Panasonic discontinued the WM61-A. They measure very differently. Not a problem once you determine the offsets or compensation / corrections And measure relative to your own measurements only.

Check the ebay seller I recommended in FIMM. They're authentic and cheap. If he's out, PM me and I'll send you a couple.

 

FIMM apparently on hiatus. I don't see anything posted on ebay.

 

I see a great many WM61-A being sold. Anyone have suggestions for a seller selling the real thing?

 

It is my intent to build two meters. One for me and one for a friend.

 

Thank you.

post #1796 of 1796
Thread Starter 
Quote:
Originally Posted by htr2d2 View Post

FIMM apparently on hiatus. I don't see anything posted on ebay.

I see a great many WM61-A being sold. Anyone have suggestions for a seller selling the real thing?

It is my intent to build two meters. One for me and one for a friend.

Thank you.

Look in Post 1 of this thread under the section about making a measurement kit. The Japanese ebay seller with authentic mics is listed there.
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