[spritzer]

The pads will also have a huge impact on the sound with all planars.

 

[ludoo]

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif I would guess that the 50 uses drivers that were maybe not up to HP-3 spec. It's entirely possible that sub par drivers were used for these giveaway phones. After all, I believe they were just meant as organ phones.

It may be, but a large difference can be explained either by a different tensioning of the driver membrane, or by the driver relaxing with intense use.

I might be wrong, but I left them playing at moderately high volume and they seem to sound better. Will report again tomorrow night. And probably recable them, as their cable is really awful: solder does not take and pools around it.

Oh, and one last thing: sooner or later I guess we need to find a way of making pads if we want to continue enjoying old phones. You wrote something about memory foam once, I tried looking for it but the sizes that can be bought are too thick. Anybody knows a way of cutting it with some precision?

 

[ludoo]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif The pads will also have a huge impact on the sound with all planars.

Yes, that's undoubtedly part of the problem. But the differences are too big to be explained only by the worn pads. And the mechanical sound made by my HP3's diaphragm clearly tells us that their drivers are extra-lose. Let's see if the HP50's diaphragms relax with some use.

Oh, and another difference: the HP50s have no white thin gasket between the driver and the baffle.

Edit: and they have round paper discs between the driver and the baffle.

 

[spritzer]

Quote:

Originally Posted by ludoo /img/forum/go_quote.gif Oh, and another difference: the HP50s have no white thin gasket between the driver and the baffle.

So the drivers aren't airtight? Baffle leak with worn out pads is a recipe for crap sound...

 

[ludoo]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif So the drivers aren't airtight? Baffle leak with worn out pads is a recipe for crap sound...

Well, they snap in the baffle so there's no space around them. Plus, the white gaskets are not that useful: they are very thin and pretty hard. Will try to seal the drivers tomorrow if the drivers loosen up a bit.

 

[Faust2D]

I guess it should not be hard to make pads out of leather and foam. I bet it will be time consuming since you will have to cutup leather and foam and then somehow put them together, glue might work but sewing might be better.

 

[ludoo]

Quote:

Originally Posted by Faust2D /img/forum/go_quote.gif I guess it should not be hard to make pads out of leather and foam. I bet it will be time consuming since you will have to cutup leather and foam and then somehow put them together, glue might work but sewing might be better.

Yes, I was thinking along those lines. I need to find some thin pleather and moemory foam, then sewing is no problem, boring but not that hard.

 

[wualta]

We have an interesting puzzle here. First, and this was years ago now, Duggeh won an HP-50A, converted it to stereo, did some desultory damping and pronounced it the most testicular (ie, bass-capable) headphone he'd ever heard and a jolly good deal.

Round 2 came months later: The two Ericks, G and J, had to wrestle to the ground the question of whether the HP-50A had a different driver from the one in the HP-3 on which it was based, because they sounded so different. Or maybe not. We didn't get complete closure on that one, as I recall, but the reptilian part of my brain smelled a kink in the curve of spacetime, to thoroughly mix a metaphor, and filed the controversy away for future gnawing.

Round 3: Recently, everyone seemed to have an HP-3 but me and nice bass-heavy ones at that, so I thought, wow, it's safe to own an HP/YH-3 now, the controversy is settled. They're bassy. Finally I got one on eBay (thanks to the community supporting me on the bid), unwrapped it and found it to sound perfectly normal, very YH-1ish, nothing like the YH-100 some had compared it to. Way-dumb-innit, I expostulated, sumpin' ain't right! I say that a lot.

So we come to Round 4: Ludo finds two HP-3 variants which should sound the same, or, if they differ, it's the HP-50 that should have more bass... but for some reason it doesn't, and I have this funny feeling he's right about the low "tension" (supposedly the corrugated diaphragms aren't tensioned, but there are other ways to get to the same lower resonant frequency and bassy sound) of his HP-3's diaphragm.

Why my HP-3 doesn't have the same sound his has... I have no idea. But nothing in my disassembly and examination of my HP-3 would so far indicate that there's a backwave leak or some other defect that's causing the difference. I suspect we're dealing with two distinct drivers or at least two distinct tolerance groups. I emphasize that at this point that's still a mild-arse guess. I hope more of this subfamily of headphones shows up so we can get to the bottom of this, once and for all time. Should be a hoot.

 

[Faust2D]

Somehow I always suspected there were variations.

 

[smeggy]

Interesting observations on the 3/50. Shame these are so old, I doubt anyone involved with them would even remember.

Anyway, I'm going to give Ludo's newest felt find a try soon. I also found some thinner wood plugs that happen to be almost the exact size of the felt. I grabbed a bunch of PC speaker grills and bought some 1.5" tag rings.

Together they look like this...

I'm hoping this will be the best combination yet. I'll find out when the new drivers and pads arrive. Hopefully ludo will approve of the new look and it will appease his Italian design sensibilities

 

[ludoo]

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif Anyway, I'm going to give Ludo's newest felt find a try soon.

It's actually the first felt I found and I used it in the infamous baling wire sandwich. I always thought it was too thick and hard to be of any use, but after your experiments with the other thick felt I thought of sending you a piece just in case.

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif I'm hoping this will be the best combination yet. I'll find out when the new drivers and pads arrive. Hopefully ludo will approve of the new look and it will appease his Italian design sensibilities

They are beautiful. Can't wait to know how they sound.

Quote:

Originally Posted by wualta /img/forum/go_quote.gif I suspect we're dealing with two distinct drivers or at least two distinct tolerance groups.

I will try to take pics of the drivers side by side, as they look different: the HP3 magnets are perfect without a spot of rust and look slightly darker, where the HP50 drivers have some rust on the magnets and look slightly grayish in shade.

But the difference is not only in the quantity of bass: what the HP3 have which I did not find in the other orthos I tried (HP50, YH1, SFIs, Pro30) is spatiality: they have soundstage, the sound has depth, instruments are placed with some precision in space. And the sound has much more weight or body or whatever you want to call it.

 

[ludoo]

As promised, I took pics last night while modding Kabeer's HP50s. Here is a guide on how to replicate my mod, with a slight difference at the end for the bassy versions. All pics are clickable to get the large size images.

1. Find the baffle clips
=================

The first thing you have to do is find the clips that keep the baffle locked in place. In the following pic I have inserted three pieces of paper in my HP3s to pinpoint the clips locations.



Finding them is pretty easy, and you don't have to destroy the pads to do so: use the above pic as reference; rotate the cup so it's in the middle of its range of motion; drag a small screwdriver along the baffle edge lightly pressing it down; when you don't feel the baffle resisting, press down slightly and cut the sticky tape with the screwdriver.

Edit: the single entry HP-50 variants have additional clips near the cable entry and exit points. An image of the baffle of an HP-50 is here.

2. Remove the tape covering the baffle edge
=================================

Now for the most boring part of the mod: the adhesive tape is slightly larger than the baffle, with the result of keeping it glued to the cup. Using the same small screwdriver, go along the baffle circumference and push the tape towards the center of the baffle so as to free it. Do it lightly, and push it only the minimum necessary. In the following pic you can see the partially liberated baffle on top, and the tape still glueing it to the cup on the bottom.



3. Remove the baffle
================

You are now ready to open the phones. Do it gently, as you would not want to break the plastic, or worse letting the drivers fall down and break. Keep in mind they are not fixed to the baffle, so as soon as you open the cups they will fall out.

With the small screwdriver you used earlier, press the clips holding the baffle towards its centre, then apply some leverage to raise it. You might need to hold onto the pads to keep the baffle raised until you have unlocked all three clips. Once the baffle is raised, gently wiggle it until the bottom part (where the cable enters the cup) comes away free. Again, do it gently near a horizontal surface, with something soft beneath to catch the driver if it falls down.



4. Preparing the main damping layer
===========================

Grab some thick felt, I used Smeggy's felt which as you can see is very thick.

Edit: for the bass-light versions (usually the HP-50 variants), keep the stock foams and use a light, dense felt in place of Smeggy's thick felt. An image of the damping layers for the bass-light versions is here, keep in mind that the thick felt at the bottom of the pic is only used as a comparison against the damping scheme for bass-heavy versions (the one described below), and is not used for bass-light versions.



Place it flat on a table, place the cup on top of it, and draw a circle.



Cut the circle of felt on the inside of the line you just draw, as the cups are smaller inside than out. You might need to trim it a bit to make it fit, but don't trim too much as it's better to press its edges firmly to make it fit so it will stay snugly in place. Place the circle of felt in the earcup and mark the positions of the four supporting posts.



Remove the disc and cut out the four holes for the posts. In my HP3s I used a sharp xacto knife (remember, don't drag it on the felt but press it down with a lot of force to make small incisions, or it will take you all night to cut the holes), for the HP50s I used a hole puncher instead which is way faster.



5. Damp the earcups
===============

Grab a small fluffy ball of cotton wool and damp the cavity in the back of the earcups. I think you could also use bluetak though I don't like the sticky mess it makes. Don't use too much cotton wool, just enough so that the felt does not flex in the center.



Now insert the thick felt disc. Be careful that the cotton wool does not move. Press the disc edges firmly with your fingers so it does not move and stays reasonably flat. You should be able to clearly see the four posts lined up with the top surface of the felt disc.



6. Tuning
================================

If you are lucky enough to have one of the "bass heavy" variants like my HP3, add a thin disc of dense woolen felt on top of the thick one (edit: if you have a bass-light version, add one or more thin discs over the stock foam, which in turn goes over a thin layer that dampens the earcup vents). I cut a smaller disc, about the size of the SFI drivers (36mm) that mostly fills the space between the four posts. You can try changing the material and size of this disc to tune the sound of your headphones.

7. Close the phones
===============

Fit the baffle back by inserting it first at the bottom, where the cable and cable stopper are. You need some force to close it, and you should hear the clips snapping back in place. If they don't, push them gently towards the baffle edge with the small screwdriver, then try again.
 
8. Addendum
==========
 
The above was written before Kabeer and I developed our theory of "differential damping". It still works well as a starting point for bass heavy phones, but often you end up overdamping them slightly. What you need to do in that case -- and what you should also do for bass light HP3/HP50 using lighter felts -- is cut a hole in the disc right next to the driver, the one made of thin felt not the one made of thick felt damping the cups. Shaping the hole, making it larger or smaller, allows you to fine tune your damping.
 
As for cables, the old Yamaha cables often give a dark sound which does not help with the orthos' natural tendency of muting treble. The best "normal" (meaning not snake oil or expensive) cable we've found is Mogami mini quad: it increases detail and clarity and gives a slight treble boost, and will set you back only a few euros/dollars per phone.
 
Final words of advice: always use a pair of phones as reference, as it will be impossible to judge your changes to the damping scheme otherwise; always use natural fibers, synthetic felts modify the sound in unpleasant ways.

 

[wualta]

Excellent tutorial. Thanks much.

 

[Kabeer]

Great guide ludoo, nicely written

 

[dBel84]

Indeed, that will be very useful for future reference.


@ Smeggy ; just fantastic - you keep pulling the aces out of your sleeve. Remind me never to play poker with you.
One question; does the plug sit directly ontop of the driver or is there another layer of felt beneath that? I really need to keep some form of mod diary so that I know what has been tried and more importantly, what you have found to work best..dB