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Just listened to some Fostex T50RPs today... WOW! - Page 254

post #3796 of 10601

I have never heard a pair of Stax but really want to. I have been reading a lot about Sigmas lately and they are exactly what I want, something that projects sound so it sounds like it is coming from in front of you. No matter what the sound stage on my headphones sounds like, it isn't realistic because it sounds like I am sitting in the middle of the stage and the instruments are around me. As cool as this sounds, it isn't like really being there. The Sigmas are earspeakers a la K1000's that angle the driver a ton. I wish I could get a listen to them, but I doubt that will happen anytime soon. I do need to try to listen to the K-1000's at the NY show though.

 

I've got supplies coming for a recable now. Going a little overboard I think, but it should be interesting. Look for some BR777 style results sometime next week.....

post #3797 of 10601
Quote:
Originally Posted by micmacmo View Post

Just curious, Armaegis. Do you think that vibration damping the cup is ineffective? (From my own experience, I found that plasticine in the baffles and getting a good seal with the pads made the most significant contribution to my sound quality.) 

 


I would say inefficient... dynamat is not really designed for absorbing pressure waves. It it meant for absorbing mechancial vibrations, which will thusly reduce the sound emanating from those vibrating surfaces. It primarily does so by converting vibrational energy into heat via shear (sort of like sliding) of the goop between the two layers (which is why you have to leave the foil there), but it also does so via simple mass loading since the heavier a body is, the less it wants to vibrate.

 

The thing is, absorbing the vibration in the cup doesn't stop the driver/baffle from generating those vibrations, which is where you really need it if you want to get the best driver response (especially in the bass, due to inertia).

 

You want the driver and connected baffle plate to be as stable as possible, so that all the energy goes purely into producing pressure waves instead of vibrating the driver assembly. Since bolting the driver directly to your skull is not an option most people will choose, nor is a strong mechanical support (ie: clamp like a mofo), your best bet to ensure driver stability is to mass load it. The heavier the assembly is relative to the diaphragm/cone/whatever, the better the driver response will be. This is basically physics and conservation of momentum, simplified of course as we are neglecting the elastic and damping properties (both electrical and physical) of the driver.

 

Now once you've minimized the resultant vibrations, you still want to reduce the remaining ones from going any further or reflecting around the structure (and we're still talking purely mechanical vibrations, nothing acoustic yet). This is where the vibration dampers like dynamat come into play. Ideally in this case, you would put them near the point of incident or at the point of maximum flexure. Since vibration dampers are also generally heavy, they can also serve as mass loaders.

 

Now in terms of acoustic damping, you've got the backwave from the driver, and the secondary wave emanating from surfaces due to vibration of the enclosure. There's also vibration generated in the enclosure due to backwave from the driver hitting the cup, which could conceivably go all the way back down and affect driver response, let's call this tertiary wave for lack of a better term. The backwave should be controlled from your cup filler and felt/foam/magicpixiedust lining in the rear cup. The secondary wave should be minimized in the first place from the mass loading and vibration damping of the driver/baffle. Tertiary wave should more or less be negligible assuming you did everything else right.

 

For acoustic damping, all materials have their own reflective and absorptive indexes. In general, softer and more porous materials have better absorption, and harder and more dense materals reflect more. Dispersion is sort of an in between factor. For general damping, you want pressure waves to pass through progressively denser materials for maximum absorption efficiency. No need to go crazy though; less is more oftentimes. Shapes and specific arrangements shouldn't do too much; it's more the overall percentage and/or combined absorptive/reflective value that matter. The notable exception here is damping that goes between the driver and your ears, as that specifically tunes the sound reaching your ears. Arrangements and shapes here can make a difference as it affects the sound waves that touche different parts of your ear.

 

Then there's the specific layering directly behind the driver itself. This is impulse control, as it's sort of like immediate backwave reflection that affects driver response. I assume (optimistically) that the manufacturers have already figured this part out in the design of the driver, so I generally don't mess with it. If I ever put anything behind it, it's light and porous so I don't affect the driver too much. Either that or I'm replacing the default filter because I accidentally removed it.

 

Jebus I'm rambling now. Anyhow, here's the tl;dr version.

1) mass load the driver assembly - make it heavy, add vibration dampeners nearby if possible

2) acoustically damp the chamber by removing hard reflective surfaces and/or putting some filler in; 100% coverage isn't really necessary; minimally just the area behind the driver would be ideal

All of this is so that you hear just the driver response as cleanly as possible. Keep it simple, keep it clean.

 

/soapbox

post #3798 of 10601

I just made a suspension headband using an old wide leather belt.  I had to buy slightly longer screws it attach it which replaced the two large Phillips head screws on either side of the headband above the cup.  There's a definite improvement in wear-ability.  Not so much pressure right on the top of the head, its more evenly distributed.  I don't think I'll be adding a pad. 

post #3799 of 10601

I just read your post.  It's as if I just had a peak behind the Wizard's curtain.  I'm copying this post and adding it to my Mod Archive.  Feel free to "ramble" on, any time.  

beerchug.gif
 

Quote:
Originally Posted by Armaegis View Post

I would say inefficient... dynamat is not really designed for absorbing pressure waves. It it meant for absorbing mechancial vibrations, which will thusly reduce the sound emanating from those vibrating surfaces. It primarily does so by converting vibrational energy into heat via shear (sort of like sliding) of the goop between the two layers (which is why you have to leave the foil there), but it also does so via simple mass loading since the heavier a body is, the less it wants to vibrate.

 

The thing is, absorbing the vibration in the cup doesn't stop the driver/baffle from generating those vibrations, which is where you really need it if you want to get the best driver response (especially in the bass, due to inertia).

 

You want the driver and connected baffle plate to be as stable as possible, so that all the energy goes purely into producing pressure waves instead of vibrating the driver assembly. Since bolting the driver directly to your skull is not an option most people will choose, nor is a strong mechanical support (ie: clamp like a mofo), your best bet to ensure driver stability is to mass load it. The heavier the assembly is relative to the diaphragm/cone/whatever, the better the driver response will be. This is basically physics and conservation of momentum, simplified of course as we are neglecting the elastic and damping properties (both electrical and physical) of the driver.

 

Now once you've minimized the resultant vibrations, you still want to reduce the remaining ones from going any further or reflecting around the structure (and we're still talking purely mechanical vibrations, nothing acoustic yet). This is where the vibration dampers like dynamat come into play. Ideally in this case, you would put them near the point of incident or at the point of maximum flexure. Since vibration dampers are also generally heavy, they can also serve as mass loaders.

 

Now in terms of acoustic damping, you've got the backwave from the driver, and the secondary wave emanating from surfaces due to vibration of the enclosure. There's also vibration generated in the enclosure due to backwave from the driver hitting the cup, which could conceivably go all the way back down and affect driver response, let's call this tertiary wave for lack of a better term. The backwave should be controlled from your cup filler and felt/foam/magicpixiedust lining in the rear cup. The secondary wave should be minimized in the first place from the mass loading and vibration damping of the driver/baffle. Tertiary wave should more or less be negligible assuming you did everything else right.

 

For acoustic damping, all materials have their own reflective and absorptive indexes. In general, softer and more porous materials have better absorption, and harder and more dense materals reflect more. Dispersion is sort of an in between factor. For general damping, you want pressure waves to pass through progressively denser materials for maximum absorption efficiency. No need to go crazy though; less is more oftentimes. Shapes and specific arrangements shouldn't do too much; it's more the overall percentage and/or combined absorptive/reflective value that matter. The notable exception here is damping that goes between the driver and your ears, as that specifically tunes the sound reaching your ears. Arrangements and shapes here can make a difference as it affects the sound waves that touche different parts of your ear.

 

Then there's the specific layering directly behind the driver itself. This is impulse control, as it's sort of like immediate backwave reflection that affects driver response. I assume (optimistically) that the manufacturers have already figured this part out in the design of the driver, so I generally don't mess with it. If I ever put anything behind it, it's light and porous so I don't affect the driver too much. Either that or I'm replacing the default filter because I accidentally removed it.

 

Jebus I'm rambling now. Anyhow, here's the tl;dr version.

1) mass load the driver assembly - make it heavy, add vibration dampeners nearby if possible

2) acoustically damp the chamber by removing hard reflective surfaces and/or putting some filler in; 100% coverage isn't really necessary; minimally just the area behind the driver would be ideal

All of this is so that you hear just the driver response as cleanly as possible. Keep it simple, keep it clean.

 

/soapbox



 

post #3800 of 10601
Quote:
Originally Posted by sharkz View Post

No matter what the sound stage on my headphones sounds like, it isn't realistic because it sounds like I am sitting in the middle of the stage and the instruments are around me. As cool as this sounds, it isn't like really being there. 


What if you are a conductor or orchestra member?  beerchug.gif

post #3801 of 10601

Entry level Stax would be very scared of the modified Fostexes... just presuming biggrin.gif

post #3802 of 10601

So as I got home from work the UPS guy also came and later today I can do the RP2 mod after I go out and get some electrical tape. I have the foam, modeling clay and dynamat. I'm hoping for it to be cleaner than previously but it's the sound that matters. 

 

Now I'm considering the suspension headband mod by LFF..just have to see what material to use now..

post #3803 of 10601

Thanks, Armaegis. There's a wealth of material here that I'll need to digest. I'm always amazed at what I learn just by asking. 

 

 

Quote:
Originally Posted by Armaegis View Post

I would say inefficient... dynamat is not really designed for absorbing pressure waves. It it meant for absorbing mechancial vibrations, which will thusly reduce the sound emanating from those vibrating surfaces. It primarily does so by converting vibrational energy into heat via shear (sort of like sliding) of the goop between the two layers (which is why you have to leave the foil there), but it also does so via simple mass loading since the heavier a body is, the less it wants to vibrate.

 

...

 

Jebus I'm rambling now. Anyhow, here's the tl;dr version.

1) mass load the driver assembly - make it heavy, add vibration dampeners nearby if possible

2) acoustically damp the chamber by removing hard reflective surfaces and/or putting some filler in; 100% coverage isn't really necessary; minimally just the area behind the driver would be ideal

All of this is so that you hear just the driver response as cleanly as possible. Keep it simple, keep it clean.

 

/soapbox



 

post #3804 of 10601
Quote:
Originally Posted by dogears View Post

Entry level Stax would be very scared of the modified Fostexes... just presuming biggrin.gif



You may actually be right. LCD-3 will likely be better than t50. We shall see. (Unveiling sometime tomorrow @ rmaf.)

 

Hopefully it's just 1k. I would have 0 respect for audez'e if they played along and wanted 1600 for it.. 1200 max.

 

Edit: Oph, lol WHADDYA know?!. They want 2k for it. deadhorse.gifI have lost  much respect for a once great headphone maker.


Edited by Hennyo - 10/13/11 at 3:37pm
post #3805 of 10601

Just got my T50RPs in! Planning on modding them tonight. They sound pretty bad stock, haha.

post #3806 of 10601
Quote:
Originally Posted by hans030390 View Post

Just got my T50RPs in! Planning on modding them tonight. They sound pretty bad stock, haha.


If you feel that stock sound is bad, maybe you won't like them after the mods.

The stock sound signature is quite freak, very pleasant sounding for long listening sessions, but nothing similar to Denon or other brands with huge amounts of midbass, though you can hear the sub bass pretty clear in the stock Fostex.

It's a very detailed headphone and revealing, even stock, but I know and understand that it's not for the vast majority of customers.
post #3807 of 10601

Originally Posted by SLaRe View Post

If you feel that stock sound is bad, maybe you won't like them after the mods.
The stock sound signature is quite freak, very pleasant sounding for long listening sessions, but nothing similar to Denon or other brands with huge amounts of midbass, though you can hear the sub bass pretty clear in the stock Fostex.
It's a very detailed headphone and revealing, even stock, but I know and understand that it's not for the vast majority of customers.


I personally found the stock really horrid sounding, w/ the felt before the drivers dipping a major notch around 2.5kHz and the cavernous cups providing a hollow plasticky mid-rangey sound and that bloated bass...yay! even blutack wasn't enough, it really took akasa, newplast & new earpads to make me happy.

 

post #3808 of 10601
Quote:
Originally Posted by hans030390 View Post

Just got my T50RPs in! Planning on modding them tonight. They sound pretty bad stock, haha.


^^ Mod away my friend! Enjoy them. =-)

 

post #3809 of 10601

Nice soapbox moment, and it looked pretty accurate to me.  L3000.gif  

 

A practical summary, though you didn't quite say it this way, is that acoustic foam is essential to control reflection, and for these phones reflections and standing waves are the biggest problem.  Any mod will require extensive reflection and standing wave reduction.  

 

Mass loading and damping via Dynamat/Plasticine/Etc. are good ways to control vibration but won't address reflection.  So mass loading by itself isn't advisable.  Mass loading is optional/good to have but requires the use of foam.

 

post #3810 of 10601

I too found the stock T50RP a quite weak contender.  It was bright(ish), lacked deep punch, had muffled highs and undetailed mids compared to other headphones I have.  However, when modified, they are something to never let go of. 

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