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Help me figure out something about the Grado HP 1000 driver: the piston-like part in the back

post #1 of 5
Thread Starter 

Hey I was wondering if any of you drivers savvy people could help me out on the subject of the Grado HP 1000 driver:


Pictures, then I'll explain


It's about this driver ("black star", you might have heard about it):


View from the back (the driver is inside the HP 1000; HP 1000 is the headphone on the right duh! :P)



And against the driver of the RS-1 you saw above; the HP 1000 driver is on your right



I'm pretty sure that the magnet of the HP 1000 driver is ring shaped, mainly because of the fact the dark grey (~charcoal) color stripe-patterned textile, in the center and that you can see through the dome (in the above photo) can also be seen from the back of the driver (in the  following picture, top left photo; it looks like some kind of air filter). And the magnet goes around it.



But the "ring" magnet of the driver (that I've separated between two parallel grey lines in this picture) is just to give you an idea of the physiology that we're studying, and not exactly what I want to ask you driver savvy people about.


What I want to ask you about is the black part on the back of the driver which surrounds that "air filter". It is the blue dotted part in the picture above (same top left photo). It sticks out of the rest.


A Head-Fier told me yesterday that he pushed the volume up to dangerous levels on his HP 1000 (not while listening) to be able to observe the driver in action, which he did successfully without any reversal of fortune. Now what has been troubling my mind during the last 24 hours is that he witnessed the black part in question move like a piston in synchronization with the diaphragm as it became visible that the latter was pumping higher volumes of air.


Personally I wouldn't say it did that because it was broke, I just think that it is a feature of the driver – otherwise the anatomy of the driver would be plainer and there simply would not be a useless "black part" that can break. If this black part can move, it is not glued in place. It is either (a) "free" to move in and out and has as only attachment point the diaphragm, or (b) held in place only by some kind of flexure to the body of the driver it is anchored in and moves in reaction to the air that the diaphragm pushes against it. a+b could also be happening together.


In all these cases, it's clear that the diaphragm and the "black moving body" work in tandem.



Questions: is it something you have already heard about (any of you knew the HP 1000 drivers were doing that)? do you know of any other driver making use of a similar principle, "diaphragm-body coupling"?


I do guess that it was made this way for the better of sound quality, but do you know or conceive specifically which component of it is being improved here: tolerance, clarity, bass? On a mechanical / acoustical point of view, what does this do more than slowing down the diaphragm?


Can you interpret better than me how this is all worked out and or held together structurally? is there an important detail that I'm missing / overlooking?


Finally can you help me sort out all the mess of this photo:


It's a sandwich (I'm starting from the top):

– thick white layer: it is the plastic rigid capsule/main body for the driver

– thin dashed/shallow orange line with something slightly gold colored under it; if there really is a flexure holding the "black part", this could be it

– shiny metal "elongated dough nut": the ring magnet?

– thinner full orange line: the voice coil? please feel free to correct me

– green ring with yellow reflection: I have no idea, what about you?



Thank you for telling me what you think about my reasoning and explaining me what you understand about this driver.

Edited by devouringone3 - 11/19/12 at 3:50pm
post #2 of 5

I'm a little surprised no one posted anything in here for you devouring.. Have you found any more info? Knowing you, I bet you have.

I'm lucky enough to have a pair of sr100 with the hp1000 drivers in them, on my head (sent to me for a little work).. They are very joe grado. They sound like a more "audiophile" pink to me.. I think I prefer the slightly more laid back/smoother pinks from what I remember.. But these are very cool man, very cool indeed.

I'm going to be refurbishing this pair with a new cable and some new lettering and a matching red grille :) Should be sweet when I'm done!

I'm not even positive you'll see this bump, I probably should have sent a PM. Oh well, more people need to know about these anyways.

post #3 of 5

After neglecting my HP1000 for a few weeks, i exercised them yesterday, and even after 4 years of ownership, they still blow me away.

post #4 of 5
Thread Starter 

Wow I accidentally stumbled upon this you bumping this when I reached this thread for a photo to reply to you in private messages, lol.


Yes, I think I mostly figured out with thelostMIDrange when he modded extensively with the vibrating back-disk and reported me the acoustic results.


Basically that piston-vibrating radiator is a gateway to modulating / modding the behavior of the diaphragm of the front, which should appeal to modders given that them and the HP 1000 were from the same era, lol ;) ThelostMIDrange did manage to tune the pair I donated to his liking... but he still prefers his particular pair of pink drivers from a vintage SR60 by a fair margin.




Of course it's really just a big hypothesis, and this drawing (mainly the placing of one rigid and one elastic point of physical attachment) was strongly inspired by the findings of and experiment thelostMIDrange backed with my experience looking at photos of the drivers and reading what others had to say about it. And the triggering element of my quest, me trying harder to elucidate this driver's principle of functioning, was this crazy dangerous experiment done by a Head-Fier http://www.head-fi.org/t/428230/my-new-joseph-grado-hp2i-hp2is/150#post_8868082

post #5 of 5

Very interesting stuff. I messaged stacker to see if he can hear any distortion with the bass like I do on the pair of sr100 sitting on my desk right now.

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