Salt Peanuts Posted January 21, 2009 Report Posted January 21, 2009 Well, various felt works differently with different headphones. T20v2 needs dense felt as they are bass heavy in stock form, so do YH-100 and HP-50/YH-3 it seems. YH-1 need something that is more transparent as they don't have as much bass to begin with and heavy felt can kill the bass that is there instead of tuning it. I discovered after playing with different felt and materials that the denser the felt the faster and snappier the headphones will be and the tighter the bass will be, but it will also reduce in quantity. Just the type of info I needed before I head off to a fabric store for T50RP, thanks!
Dusty Chalk Posted January 21, 2009 Author Report Posted January 21, 2009 Well, various felt works differently with different headphones. T20v2 needs dense felt as they are bass heavy in stock form, so do YH-100 and HP-50/YH-3 it seems. YH-1 need something that is more transparent as they don't have as much bass to begin with and heavy felt can kill the bass that is there instead of tuning it. I discovered after playing with different felt and materials that the denser the felt the faster and snappier the headphones will be and the tighter the bass will be, but it will also reduce in quantity.This coincides exactly with what my thought exercise of superimposing a sloped filter on a the frequency response you've described is. If you start the slope too high, you thin out the bass too much; if you start the slope too low, you accomplish nothing; one basically wants to shoot for a "sweet spot" of attenuation of the peak you described with the slope, but before the slope gets too high (as with lowering frequencies) and attenuates too much bass. If I remember correctly, this is the same sort of thing that bass reflex math yields. So which would it have more of an effect on -- the 40's (closed design) or the 50's (open design)? That's the main reason I got both. I'm more of a closed design guy, but if the 50's yield better sound, I'll stick with those.
faust3d Posted January 21, 2009 Report Posted January 21, 2009 Keep in mind that damping also improves the speed and transient response over entire frequency range, for planar drivers, and this turns out to be a great side-effect in addition to the flat frequency response.
Dusty Chalk Posted January 21, 2009 Author Report Posted January 21, 2009 Yeah, that makes sense -- reduces resonance by acting as a braking mechanism.
Smeggy Posted January 22, 2009 Report Posted January 22, 2009 Just be cautious with it. I actually managed to damp a set in a way that the sounded real nice, but way too fast and detailed. It was very, very distracting. Sometimes you can get too much of a good thing. Description.... imagine a 12 person brass section playing 20 feet in front of you. Now imagine those same twelve surrounding you no more than 3 feet away. Same tune but one is totally too much.
The Monkey Posted January 22, 2009 Report Posted January 22, 2009 Where does one source mineral wool for this specific application? I see it for sale in board form, but not in, um, fluffy form.
Smeggy Posted January 22, 2009 Report Posted January 22, 2009 (edited) look for mineral wool roll, or blanket. or felt or batting.. Edited January 22, 2009 by Smeggy
wualta Posted January 22, 2009 Report Posted January 22, 2009 Alright, so to test my understanding: it's not to absorb acoustic backwave, but to act as sort of a broad "notch" filter? Except that wouldn't wind resistance continue to go up with lower frequencies (I.E. wouldn't it act as a broad sloped filter)? Well, a broad notch isn't a notch any longer, but never mind. The felt's not acting as a filter in the sense that its effect can't be duplicated by any EQ, no matter how sophisticated. The bass-reflex analogy isn't valid, I'm afraid. The idea is to draw out and absorb the stored energy in the diaphragm that's due to its fundamental resonance. The felt acts preferentially to reduce the Q of that resonance. Its other effects, luckily, are what just about every ortho-type headphone driver we've come across needs. But you're right, the more the diaphragm tries to move, the greater the effect of the felt. The response curve does change-- it flattens out-- which could also be done with EQ. But without the felt, the bass would continue to be poofy and slamless. This lack of diaphragm control extends into the midrange, but by the time we're into the treble, the diaphragm is barely moving and the felt's effect as a shock absorber is nil. It does reflect some treble energy but not much. It probably absorbs more than it reflects. The bass reflex idea applies to a side effect of damping with felt-- moving the fundamental resonance upward in frequency due to the compliance change caused by the tiny trapped volume of air between the diaphragm and the felt. Overdamping starts to lop off the bass, akin to overtensioning an electrostatic diaphragm.
Dusty Chalk Posted January 22, 2009 Author Report Posted January 22, 2009 Thanks for taking the time to explain that to me.
Dusty Chalk Posted January 22, 2009 Author Report Posted January 22, 2009 You have no idea the crazy lengths some of us go to.... Thanks, you have totally ruined me, I can't look at something now without wondering...just going through the deals at amazon: Microfiber...neoprene...cashmere...batting... ...of course, in my case, it's with complete lack of experience, so I guess I just gotta get in there and start trying stuff. Because although although you guys are tweaking the stuff based on the frequency response stuff, I have to wonder if the small enclosures aren't still a problem in terms of the waveform coming off the back, and reflecting back past the driver into the ear, combining with the waveform coming off the front won't have some sort of comb-filtering effect as well, so I'm thinking something has to minimize the amount of reflection, no? Or are you just assuming the extant design (whatever the original manufacturer has done to minimize reflection) keeps it from doing so (combined with the driver not letting a lot of information past it)?
swt61 Posted January 22, 2009 Report Posted January 22, 2009 I've been curious about the ShamWow, or any man made shammy material. I found that thick, dense felt worked quite well for the YH-100, but not sure yet what will work well on the T50RP driver.
wualta Posted January 22, 2009 Report Posted January 22, 2009 Cackle cackle! Yes, now you're doomed to do what Smeggy and I have been doing for years: prowl up and down the housewares and auto accessories aisles in department stores and hardware stores and dollar stores, looking at everything as potential damping or absorbing material, buying strange assortments of stuff, filling boxes with it at home, and finding that most of it is no more effective than plain ol' felt, yea, even unto eternity. "Picture of a latter-day Flying Dutchman.. sailing.. into the Twilight Zone." And yes, enclosure reflections are considered to be a big problem for precisely the reasons stated. Peter, you don't by any slim chance have relatives who live or lived in Buffalo NY, do you?
mypasswordis Posted January 23, 2009 Report Posted January 23, 2009 Just be cautious with it. I actually managed to damp a set in a way that the sounded real nice, but way too fast and detailed. It was very, very distracting. Sometimes you can get too much of a good thing. Description.... imagine a 12 person brass section playing 20 feet in front of you. Now imagine those same twelve surrounding you no more than 3 feet away. Same tune but one is totally too much. I'm actually getting some of this problem with my T50RP. It's more like 10 feet if 20 is optimum (I prefer more in real life, brass instruments are really freaking loud), which is still too close for me, except for music that calls for immediacy. Not sure what to do, I didn't damp too much and I finally got it to around the right frequency balance for me. I still need to swap in a bigger reflex dot somewhere. Doesn't matter if I can't fix it, this close sound is something some of my other headphones don't do well. I can hear bad editing done very clearly (mainly grafts), which is hilarious. If anyone else has the CD I'm currently listening to, Viktoria Mullova's Shostakovich/Prokofiev 2 CD, 2nd mvmt of the Prokofiev, 1:10 in. I admit, I'm guilty of bad editing myself.
mypasswordis Posted January 23, 2009 Report Posted January 23, 2009 Nevermind, it's more like 15 feet, which is fine. Once I swap in a bigger reflex dot I think it's good to go. Once I do that, I'll be sure to compare it to my T40v1.
Kabeer Posted January 23, 2009 Report Posted January 23, 2009 Heh, nice thread. Since you are looking at anything and everything, maybe we should take on the opinions of an acoustical engineer, someone who can give better direction for us to take. Btw Smeggy, I have used a polyester women's dress material in my HP-50S, which is basically a coarser and cheapass kinda silk I would think.... I have also tried the cotton pads, you might have to remove the top and bottom layer from them, like Tomek has done, because they are a thicker paper, and might choke the sound.... I am no expert, but I think combinations of different felt densities and reflex dots can pretty much achieve everything! The polyester I use sharpens up the whole spectrum a little without losing too much bass, so I use them as tuning discs, but it colours the sound a bit. And the only occasion I used paper inside the earcup it sounded HORRIBLE, just like you expect someone putting paper inside your earcup lol.
Kabeer Posted January 23, 2009 Report Posted January 23, 2009 I use only electrical tape in my final Orthodome. No wool, no felt, no tissue. So you added a big reflex donut, and no damping :S? So this would assume the SFI doesnt really require and damping, and just a big treble boost?
ludoo Posted January 23, 2009 Report Posted January 23, 2009 Oh wow, we really needed a third ortho thread to keep track of. As for felts, what I think makes it good for our purposes (and here I may repeat something wualta has already said) is that it has incredible density, while still allowing air to pass. And in my limited experience (about 20-30 different types of fabrics/felts) I'm pretty convinced that natural fibers are better at absorbing energy than shiny synthetic fibers, which might be why kabeer's fake silk does nothing much to bass. One other thing to note is that placement has as much to do with the damping results as the kind of material you are using. We basically have three "damping zones", each one with different effects: the driver itself; the vents (if any); the inside surface of the cups (and baffle, maybe). While the first two are similar in that they trap air pressure, and just offer different effectiveness (the nearer the felt to the driver, the larger its effect), damping the inside surface of the cups just kills reflections. Two different things, which sometimes might be combined as in the "standard" bass heavy HP-3 mod which uses a very thick disc of felt (smeggy's felt) to both damp the back of the earcups and the vents. A second, finer kind of placement is where you apply damping on the drivers: we found out with kabeer that by varying the damping density on different areas of the driver, you can roughly select which frequencies you damp. So by making donuts, or a combination of donuts and discs, you can for example raise the treble without killing off too much deep bass, using felt instead of a reflex disc/dot. My experience with the Yamaha I have/had and with the T20v2 is that usually you need a dense, thin layer pressed against the driver (kept in place with foam in the HP50, smeggy's felt acting also as a spring in the hp3, the driver assembly in the t20v2), and another, usually lighter layer (or two) for the vents and cups. Then it's a matter of finding a balance between vent damping and driver damping.
Duggeh Posted January 25, 2009 Report Posted January 25, 2009 So you added a big reflex donut, and no damping :S? So this would assume the SFI doesnt really require and damping, and just a big treble boost? Actually this solution wrestles the treble of the SFIs under control and brings out a fuller bassier sound, with one more hole uncovered the space in the headstage opens right up but I get headaches from the treble. The heavier I damp the SFI driver the more treble it kills, to a point.
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