Headphone CSD waterfall plots - Page 27

Well your opinion doesn't change what I think about them but it is nice when other people who have my headphones like them as well. I usually try to send people headphones that I own that other people would also enjoy. I would probably never ask Anax if he wanted to hear my DT880 if he never heard of it unless it was something he requested :P

It did however help since I was planning on putting wood cups and wanted some opinions on whether i should do them or not but Anax does seem to think ti will improve as do others so easier decision that way :)

Actually we did talk about having your phones measured if you recall the PM, I wasn't being a stealthy ninja about it.  

I actually have Metal and Wood housings for my 225 drivers so I have a choice.  I think wood is the better choice for my case.

I would always welcome the opportunity to hear the HE4 and DT880.  I have fonder memories of the 880 than the T1 I heard.

I am surprised the housing material makes any difference, Marv do you have any comparison tests with just that as variable ? No change in geometry, nor driver, just the housing material ( same thickness obviously)

Quote:

Originally Posted by Anaxilus 

Actually we did talk about having your phones measured if you recall the PM, I wasn't being a stealthy ninja about it.  

 

I actually have Metal and Wood housings for my 225 drivers so I have a choice.  I think wood is the better choice for my case.

 

I would always welcome the opportunity to hear the HE4 and DT880.  I have fonder memories of the 880 than the T1 I heard.

Well I must have missed it although I do remember measurements being in the PM after I sent them to Tyll but not sure about before.

lol HE4 and DT880 :) trying to take all my headphones! Although I do have my T50RP but that's a work in progress in terms of mods and hopefully to be done this weekend. Maybe after I get my Magnums back I could send you both so you have them to compare.

Quote:

Originally Posted by purrin 

 

 

John Grado knew what he was doing with the wood cups:

 

http://www.head-fi.org/t/566929/headphone-csd-waterfall-plots/105#post_7735041

 

No results for metal cups though - and no don't feel like taking my HP1000s apart for another experiment even though I hate (not soundwise, but flexiblity and user-friendly wise) the APS cables already on them.

 

I'll post overheads just for the heck of it.

I can bring my metal cups and wood cups and you can stimulate yourself as much as you like.  

Marv, isnt't the mushroom cup different shape from the standard plastic one? In particular the shape of the opening to outside? In regards to the John Grado line, you really cannot assume difference come from the exotic material because drivers might be slightly tuned and/or  earcup dimensions modified. For instance, rs1 cup is slighly deeper than rs2 isn't it?

Honestly, there's no magic in all this, the grados make use of helmholtz resonator effect to make their cans lively (with no damping on the outer cavity), I doubt of strong coupling with structural resonances in the frame ( where wood would help due to higher material damping). You get also varying surface absorption going from machined aluminum to more rough wood cup, but that's marginal.

I notice the 2k peak is still there in the liberated driver, could you describe the setup? If there's effectivelny no chamber in that test then it's a driver resonance, which is unexpected ( the mushroom cup made it shift by 500Hz ). 

The 2kHz peak seems clearly related to earcup acoustic resonance (gone in the liberated driver, tamed with felt lining).

The 4 and 5.5kHz peaks seem dominated by driver resonances (although it could also be combined to higher order acoustic resonance) since we see them with the liberated driver test. So then it begs the question: by what kind of magic sprinkle a wood cup can help tame the 5.5kHz resonance compared to stock plastic or aluminum? If we consider the following:

1. Structural damping provided by the frame: unlikely as the inertial forces from the diaphragm motion barely excite the frame. Plus, plastic has no less internal damping than wood (aluminum has very little self damping though).

2. Radiation from the frame. I feel this is also negligible but somehow the frame (I mean the earcup solid part) gets acoustically excited and resonate. If with some bad luck the structural resonance matches the acoustic and / or driver resonance than it could possible be visible in the SPL response (20dB down or something). Considering we're looking at CSDs, if the frame damping is small, I guess we can see it in the decay graph even though this "secondary" radiation path is 20dB compared to the radiation from the driver itself (because it's 20dB down, it doesn't show up in the standard FRF graph).

Number 2 is plausible actually. Well, I see no other way than try it through simulation and see if I can reproduce such scenario......

Quote:

Originally Posted by arnaud 

I am surprised the housing material makes any difference...

Really?!

Were you being sarcastic?

Edited my post: iphone issue, will review later...

Is this reasonably close to the original dimensions of the SR80 cup? (from headwize sr80 mod page): 

Started a simulation with some approximate geometry:

> Housing: P.E 3mm, 50mm diameter, 20mm tall (height between diaphragm and outlet), 40mm diameter ring on the outlet

> Diaphragm: 0.5mm PET, 40mm diameter, flat, assumed to be 5mm away from ear

> Earpad: some basic foam, 50/60mm inner/outer diameter, 10mm tall

> Ear surface: assumed flat / rigid for now

I have a problem with the mesh so I won't post results now but I can already see the following:

> Acoustic resonance:  2kHz, then 4kHz and 6kHz (outer chamber)

> Diaphragm resonances (listing the first radial modes only as the other ones don't radiate efficiently I believe. Anyhow I can check this later with the model): 1kHz (piston mode (0,1) as illustrated here: http://www.kettering.edu/physics/drussell/Demos/MembraneCircle/Circle.html ), 3.5kHz (0,2) , 6kHz (0,3)

> Housing resonances: start as early as 1.5kHz but they seem to cancel out except for the "breathing" mode of the cylinder at 6kHz (example here: http://www.kettering.edu/physics/drussell/Demos/radiation/radiation.html )

Interestingly, the SPL shows 2 main peaks: 1kHz (I assume due to the piston mode of the diaphragm) an 6kHz (I assume due to the breathing mode of the cylinder). I am pretty sure the housing is mainly responding to acoustic excitation (rather than the direct mechanical excitation of the diaphragm) but will investigate later.

In any case I may have to eat humble pie if I can see the effect of the housing resonances on the coupled system response ;)

Before I proceed with cleaning up the model, can anyone confirm / correct the dimensions of the housing if possible? Here's a view of the current assumed geometry (I have to keep it simple as I have only little spare time in the evenings to look at this):

It's a sunny Monday over here