[Armaegis]

Should be enough for one headphone...

 

[micmacmo]

Armaegis, do you subscribe to the idea that you don't need to cover the whole cup surface with a mass dampener? 

 

[Armaegis]

Like most things, there are diminishing return. I'm sure that covering the entire surface would yield "better" results, but if I can achieve 80% of that with a quarter coverage, I'll go with that option for simplicity and lighter weight. 

 

[micmacmo]

I ask because this Web page says that people are needlessly thorough in their coverage with constrained layer dampeners. The author's arguments make sense. In my past mods, I've covered every visible surface, but maybe that's not necessary. Maybe I can can get away with damping the central area of large flat surfaces. Thanks for the idea!

 

[Armaegis]

I see some people peeling the foil off the dynamat, which doesn't make much sense to me. The foil is the constraining layer; without it, the goopy stuff is significantly less effective and is primarily damping by mass instead of vibration absorption. If you're doing that, you might as well stick to putty. 

 

[micmacmo]

I learned something new there. Thanks. The (misguided) thinking is that the aluminum serves as a flat surface that will itself "reflect" sounds.

 

[Armaegis]

Quote:

I learned something new there. Thanks. The (misguided) thinking is that the aluminum serves as a flat surface that will itself "reflect" sounds.

Well yes, the aluminum will reflect... you have to pick the lesser of evils there. That or layer felts and stuff inside (which most people do). For optimal use of dynamat, it really should be on a surface outside of the sound chamber... but it wouldn't look very nice on headphones that way. 
 

 

[wualta]

Any flat surfaces (aluminum or goo) will indeed reflect sound. So cover 'em with felt or don't let 'em be flat. Add facets to reflect the sound away from the diaphragm and break up standing waves. Pretend the inside of your headphone is a stealth fighter undergoing radar tests at Lockheed. Study photos of geodes. Avoid parallel walls and symmetrical shapes.
 
That's a very handy site, micmacmo. Thanks for bringing it to our attention.

 

[rhythmdevils]

My feeling is that if you had your orthos damped (acoustically) to the point that enclosure vibration was a problem, you would have a very very nice headphone and probably wouldn't need to bother with the mass damping.  I just don't think that any of the things that bother me about any of my vintage orthos are caused by enclosure vibrations.  But I could certainly be wrong, as I often am with the crazy world inside an ortho...

 

[Armaegis]

I am of the opinion that chamber damping and reflective surface damping have a greater effect on the mids and highs, while mass-damping has a greater effect on the bass. 
 
Low frequencies need a really stable/fixed point to hold the driver in order to generate a clean response, and headphone frames are inherently not that stable unless they clamp like a mofo or are very heavy. Dave Rat in some of his youtube videos showed various headphone low end responses improving significantly when the cups were touched to a solid object, in essence anchoring them. 
 
Now mass damping the baffle plate or whatever the heck you call the plate that the driver is attached to; the stiffer and less prone to vibration you make it, the better your overall headphone response should be. Since the baffle is typically attached to the cup with a few screws, mass damping the cup works to a degree because the system is connected, but you'd be better off taming the vibrations nearer the source (assuming there's space to do so... which sometimes there isn't if the drivers are large and/or the cups are small). 
 
I've always felt that the use of dynamat on the inside of headphones was a little bit backwards, though it works incidentally rather than intentionally. It's supposed to go something like this... incident surface --> gooey stuff (the butyl adhesive) --> constraining layer (the foil). By putting dynamat on the inside, we are significantly reducing sound coming in from the outside, and reducing vibration in the cup caused by the driver itself. Backwave pressure from the driver will be reflecting off the foil, though will also happily not transfer (or a minimal amount of) that energy into the cup and vibrate the driver. So it works in that sense, but I think we'd be better served with an absorptive foam there instead.
 
Of course, I could just be talking out of my rear facing flapper at this point. I've got plenty of the science, but not enough of the doohickeys to play with. 

 

[micmacmo]

Quote:

Pretend the inside of your headphone is a stealth fighter undergoing radar tests at Lockheed. 
 
That's a very handy site, micmacmo. Thanks for bringing it to our attention.

Thanks for the imagery and the smile. I'm glad I had something to share in return.
 

 

[nick n]

waaaaay back on page 275 ludoo says:
"always use natural fibers, synthetic felts modify the sound in unpleasant ways."  so it will be ok with tunes that have a lot of synthesizers?

 
Out of curiosity: Is this still a commonly held belief?
What would said UNPLEASANT effects be? I've seen plenty of pics with the fake stuff in here.
 
I have no idea what the stuff I used is. I can sort of understand that as looking at stuff like that under microscopes shows a difference: texture/surface details
 
Oh well it pays to read I know, but 1202 pages....  I guess i need to start from the beginning.. 4 pages a day should only take what? just under a year?  Perfect. I can avoid life for a year.
 
 

 

[wualta]

Not to take anything away from Dave Rat, but I've long been puzzled by the assertion that drivers have to be bolted to perfectly rigid baffles to produce good bass. In the speaker world this has given us spikes meant to solidly anchor speaker cabinets. But the question arises: doesn't this require that earpads be solid as well? Either that or headphone cups would have to be massive to prevent bass-robbing motion. Just sayin'. Askin', really.
 
I don't recall ludoo's support of his felt doctrine, but natural fibers in audio (usually we're talking wool here) do have an advantage when it comes to absorption when used in bulk. I'm not sure what he means when it comes to thin layers, where I'd expect mere porosity to dominate the audible effects; we should ask him. I'm still waiting for someone to try, say, cat fluff as a damping medium ("Why is this headphone making me sneeze?").

 

[Armaegis]

Quote:

Not to take anything away from Dave Rat, but I've long been puzzled by the assertion that drivers have to be bolted to perfectly rigid baffles to produce good bass. In the speaker world this has given us spikes meant to solidly anchor speaker cabinets. But the question arises: doesn't this require that earpads be solid as well? Either that or headphone cups would have to be massive to prevent bass-robbing motion. Just sayin'. Askin', really.

 
Any force produces an equal and opposite reaction right? At the higher frequencies it isn't as crucial since the support structure doesn't really have the time to move before the reverse side of the sinewave balances it out. Bass frequencies though need the rigid support since they occur at a rate where the physical movement of the driver will now have an effect on the sound produced.
 
No the earpads don't need to be solid... (you probably know all this, but for the sake of any newcomers reading)... there are a couple factors at play when you consider vibrational damping, and for the moment I'm just talking about mechanical vibration, not acoustic/pressure waves. Mass damping is simply adding mass. Making the support element heavier relative to the driving element means the support structure moves less, which makes the driver more stable and more of its energy goes into purely producing sound rather than shaking itself back and forth. Very closely related to mass damping is mechanical coupling; which is like adding mass indirectly. The other main element to look at is internal damping, which is a material's inherent ability to absorb vibration. In general (though terribly over simplified), softer materials absorb better than hard materials.
 
Adding stuff like dynamat serves as a double whammy, by adding physical mass to the support, and that added mass itself has very strong absorptive qualities.
 
Now consider your head, which is mechanically coupled to the headphones via the earpads. Now if you were truly hardcore, you could simply have the cups bolted to your skull (do a google image search for "halo neck brace"). Since I doubt most of us would go for that option, we'll settle for a moderate earpad clamp instead. A stiffer earpad would provide a stronger mechanical coupling, but there are comfort issues. A hard pad may also not comform to the face as well, which results in a poorer mechanical connection. A softer pad may comform better and thus improve coupling, but softer means a lesser connection, so less coupling... etc. The pad material itself also as an effect on internal damping and absorption. So really, it's all a balance.
 
Going from a purely science standpoint, I think the best arrangement for a pad would be to put dynamat on the outside of the baffle, butyl based adhesive (optional), then the pad.
 

 

[MDR30]

Quote:

Not to take anything away from Dave Rat, but I've long been puzzled by the assertion that drivers have to be bolted to perfectly rigid baffles to produce good bass. In the speaker world this has given us spikes meant to solidly anchor speaker cabinets. But the question arises: doesn't this require that earpads be solid as well? Either that or headphone cups would have to be massive to prevent bass-robbing motion. Just sayin'. Askin', really.
 

Who can resist the pragmatic Dave Rat shooting from the hip? Not I! His simple/advanced measurements tell us a lot. In this case the very telling difference of bass reproduction of the Sennheiser HD280 loose and fixed. I can sympathize with Wualta's common sense, but reality seems not to agree. Check out Mr Rat's findings:
 
http://www.youtube.com/watch?v=uHkb4bhdnRA&feature=related