[rhythmdevils]

It's a bit more complicated than that because a fully open back ortho becomes less efficient when you add damping materials.  I'd say you could also think of it as the driver having to work harder to push against the added resistance (damping materials) behind the driver. 

 

[sluker]

On another note,
I just broke off the original solder joint on one of the drivers. I tried re-soldering but I cant get the solder to stick to the contact pad.Is there a trick to this? I tried the usual techniques (applying flux) but nothing works. Is the driver toast? That would be a shame as it is in perfect shape otherwise.

 

[mrspeakers]

On another note,
I just broke off the original solder joint on one of the drivers. I tried re-soldering but I cant get the solder to stick to the contact pad.Is there a trick to this? I tried the usual techniques (applying flux) but nothing works. Is the driver toast? That would be a shame as it is in perfect shape otherwise.

 
You need a quality iron with a fine, very hot tip to pull this off.
 
A) Get a great solder wick and QUICKLY clean the old goop off the pad.  Radioshack will have it.
 
B) Use some 60/40 VERY THIN rosin core solder, pre-tin the iron tip and then solder that sucker, FAST.  If you take too long the pad will melt.
 
PM me if you have any questions.

 

[nick n]

you can try some silver conductive epoxy and that will work. Even bonds to aluminum and seems to have very little difference than a solder joint, in fact if you wanted to do both sides then you will know you have the same conductivity specs, but you won't hear a difference I don't think. I used some on a pair of electrets to reattach a lead to an aluminum stator that wouldn't take a solder bond.
 
Only thing is the stuff is ~ $40 ish for the two part set, and you'll have more than a lifetime's worth.
 
http://www.mgchemicals.com/products/8331.html
"...It is primarily used as a solder replacement for bonding heat-sensitive electronic components...Its primary applications are repair and assembly of electronics in microelectronics and optoelectronics. It is used in the automobile, aerospace, marine communication, instrumentation, and industrial control equipment industries."

 

[bluemonkeyflyer]

micmacmo,
 
I obtained some of your unobtanium Grodan rock wool today. I finished a retrofit of one of my BMF V8's to Dr. micmacMo specs. I removed the cotton from the cups and the Transpore from the back of the drivers. I substituted a 1x6.5x7 cm wedge of rockwool custom fit around the shock absorbers and compressed a "cavity" to accomodate the headband hanger screw compartment. I then applied a 3x3 cm piece of thin microfiber lens cleaning cloth directly over the white driver paper. I kept the stock baffle port open and closed off all but 1/8 inch of the lowest cup vent slot with tape from the outside. Shure 840's, 2x7 cm Acoustipack Lite strips in the side cup "wells', Dynamat with felt overlay around the ear side of the drivers, and flush loaded baffles completed the mod. I'm listening now and this setup is KickA**!  I'm enjoying your mod right now and this is a comparable mod configuration for people who cannot find the cotton and Transpore that we use.  Great mod!
 
Quote:

One isotope of Unobtainium I've wanted to get my hands on for awhile is rock wool. Joelpearce mentioned it many months ago as a cup dampener and said he had it leftover from a construction project. It turns out that it's not just sold in bulk for construction but also commonly used in the plant nursery and hydroponics industry as an artificial "soil" for germinating seeds. 
 
I went to a hydroponics shop in town (I now know where marijuana grow-ops get their equipment) and picked up some 3-inch and 4-inch cubes of rock wool. Cheap. It's made by Grodan with a 70 kg/m^3 density (vs the Roxul Safe'n'Sound fiber Joel used with its 40 kg/m^3).
 

 
 
I cut 1-cm-thick slabs and cut them to fit into the bottom of the cups and around the hanger "hump," thusly:
 

 
I tried the rock wool with various materials on the back of the driver (on top of the stock white material). The only effect of these over-the-driver materials was to enhance or decrease the mids and treble, from about 1 kHz up (no effect on lower mids or bass). Plush microfiber (from a dusting cloth) gave the brightest sound, then, in descending order, thin/smooth microfiber (from a lens cleaner), dense cotton (from a nursing pad) and stock material alone.
 
The thin microfiber with the rock wool gave the flattest frequency response and, to my ears, the most pleasing sound. 
 

 

 
(Note the apparent "ridge" at 60 Hz in the heat graph. I'm not sure what that is but it's consistent across all my mods involving rock wool. I can't hear it, though. Maybe that's why Purrin truncates his amazing waterfall charts to ignore the lower end of the spectrum?)
 
This mod measures similarly to my mods involving absorbent cotton in the cup and plush microfiber over the stock white driver material. However, I think this sounds a little more open (although I'm not sure what I'd need to measure to convince myself that it is truly so! 

 )   I'll stick with this mod until I find some fault with its sound and start mod'ing again. 
 
 
 

 

[mrspeakers]

Quote:

It's a bit more complicated than that because a fully open back ortho becomes less efficient when you add damping materials.  I'd say you could also think of it as the driver having to work harder to push against the added resistance (damping materials) behind the driver. 

 
True, but I think that is a different effect.  
 
I haven't played with open-back systems, and I know you have, so I defer a bit on this, but I would guess the effect is less dramatic...  
 
My quick SWAg would be in an open-back there'd be a 2-4dB reduction in output as I would think that what's really going on is impedance matching the "load" on both sides of the driver to improve linearity.  In the T50, the impedance in the closed cup is probably already pretty changing less as the air in the cup already is effectively a significant load, so it's a second order effect.  I'm just guessing and can't prove it, so caveat emptor...  Whaddya think?

 

[kalbee]

@slurker: try defogger repair paint. I think it was wje that uses it with much success. Use a few layers of it, then epoxy it for safety.


Well in a closed cup, considering isodynamic drivers output the same on both orientations, we can assume near full reflection at the same volume. Having two identical sound pressure level sources gives a total of +3dB to your ears, though some frequencies suffer from cancellation I guess. For all decay in back waves result in a lower gained SPL until the difference is negligible. Though technically it takes about 3dB changes for the human ear to percieve difference?? So this probably doesnt play a big part in it. The other part should be due to air resistance I think. I have a open back ortho and it definitely is sensitive to how porous the back damping is. To some point I will feel air waves being pumped into my ears... Talk about punchy.

 

[micmacmo]

Quote:

micmacmo,
 
I obtained some of your unobtanium Grodan rock wool today. I finished a retrofit of one of my BMF V8's to Dr. micmacMo specs.
...
I'm listening now and this setup is KickA**!  I'm enjoying your mod right now and this is a comparable mod configuration for people who cannot find the cotton and Transpore that we use.  Great mod!

 
You just made my day. Glad to hear it worked and sounded good!
 
Quote:

On another note,
I just broke off the original solder joint on one of the drivers. I tried re-soldering but I cant get the solder to stick to the contact pad.Is there a trick to this? I tried the usual techniques (applying flux) but nothing works. Is the driver toast? That would be a shame as it is in perfect shape otherwise.

 
So all the original solder is gone? If not, I'd recommend leaving it in place. I'd make sure the wire and the soldering iron are both well tinned. Make sure your iron is at at 300 C. But try again.  
 
Otherwise, MrSpeakers advice is consistent with my own experience. The pad is aluminum, I've been told, and that makes resoldering onto the naked pad a bit more difficult. Use a clean, well tinned iron. When I had this problem, I set my iron to 300 C. Work to get a blob of solder to stick to the pad first. Then solder down the wire (don't forget to tin the wire first). I thought I'd made a good connection several times, but my multimeter said otherwise. I had to resolder the wire several times, but it's fine now.  

 

[sluker]

Unfortunately the original solder is what came off the pad. I have tried over and over to get a blob to stick with no luck. I think I will buy some defogger repair and give it a shot.
Thanks for all the advice everyone.

 

[soundstige]

If it's just the original solder "blob" that came off, you're fine. As long as the pad itself didn't detach from the terminal, in which case you have a more or less unusable driver. Heat and speed are your friends, and try tinning (adhering solder to) the wire you want to affix before contacting it to the pad.
Quote:

Unfortunately the original solder is what came off the pad. I have tried over and over to get a blob to stick with no luck. I think I will buy some defogger repair and give it a shot.
Thanks for all the advice everyone.

 

[mrspeakers]

Quote:

So all the original solder is gone? If not, I'd recommend leaving it in place. I'd make sure the wire and the soldering iron are both well tinned. Make sure your iron is at at 300 C. But try again.  
 
Otherwise, MrSpeakers advice is consistent with my own experience. The pad is aluminum, I've been told, and that makes resoldering onto the naked pad a bit more difficult. Use a clean, well tinned iron. When I had this problem, I set my iron to 300 C. Work to get a blob of solder to stick to the pad first. Then solder down the wire (don't forget to tin the wire first). I thought I'd made a good connection several times, but my multimeter said otherwise. I had to resolder the wire several times, but it's fine now.  

 
I find it is usually better to remove the old solder...  If the alloys are too different, or the solder is just too "used" it may not work out too happily, plus you may end up with so much solder the thermal capacitance rises and increases the chance of a melted pad even if you are in/out fast...

 

[nick n]

Is basically everyone in here using store-bought available pads?
What I am specifically wondering , has anyone rolled their own and experimented with smaller openings, and also wondering how things change up from ~40mm center openings and upwards.  I'll give a stock pair a shot with some leather pads I made for something else. Think they have~40mm centers.
 
I know everything is tweaked for the pads used more or less.
 
Obviously soundstage will suffer somewhat. I'll get around to testing in a day or so.

 

[kalbee]

nick, I plan on rolling pads somewhat based on the HM5 pads; so for now I am waiting for them to arrive to start analyzing and making changes from there!
My endeavor with HP-1 pads have failed thus now and I can only say that my pleather is too thick for the smaller scale pads (one more variation or two I plan on trying). Kind of didn't bother for the HG2001 unless I start trying that suggested supra-to-circumaural baffle adapter.

 

[hans030390]

micmacmo, which mod configuration have you found works best with the 003 pads? I'm a bit lost on everything you've done and for which pads. And are you using actual 003 pads, or do they happen to be the spare HM5 pads you can purchase?

 

[micmacmo]

Quote:

micmacmo, which mod configuration have you found works best with the 003 pads?
...
And are you using actual 003 pads, or do they happen to be the spare HM5 pads you can purchase?

I'm using actual 003 pads. 
 
I had to think about which mod I preferred. Of the two mods I consider distinctive, I think I'd suggest the thin microfiber/rock wool mod over the plush microfiber/cotton mod. Two my ears, they both sounded very good and measured well. But there are some practical considerations that cause me to favour the rock wool-based mod. 
 
My results with the rock-wool mod have been reproduced by BMF but he couldn't get the microfiber/cotton mod to work to his liking. 
 
Plus, with the microfiber/cotton mod, it requires that you use specific materials with little room for variation. And, as we all know, there's a lot of variation in cotton filling. Everything from teased cotton balls to absorbent cotton and cotton from nursing pads. And I got lucky with the plush microfiber I used. I found it at a discount store and haven't seen anything identical since. 
 
On the other hand, Grodan rock wool is readily available in small amounts and the company says the density is uniform at 70 kg/cubic meter. Rock wool does a good job of mopping up the backwave and resonance in the cup. And the lens cleaning cloths I use are everywhere and they're cheap. Although they have a large variation in porosity, I view this as being a good thing with this mod. You can swap out different samples of microfiber and tune the upper end of the spectrum to your liking. And you're not limited to microfiber (see chart below). My hypothesis is that the more porous the driver covering, the warmer the sound. The less porous/more reflective the material, the greater the emphasis on the mids and treble. (You can judge the porosity/permeability just by blowing threw the material and assessing the resistance.)
 
Here's what I mean. The chart below plots the frequency response of the rock wool mod using four different driver-cover materials. Note how the response curves begin to diverge at around 1 kHz. The plush microfiber gives the greatest treble boost, then, in descending order, lens-cleaning microfiber, cotton from a nursing pad and a naked driver (covered only with the stock white material). This rank order is pretty consistent with how I'd compare the materials using the aforementioned and patented MoBlow® test.
 

 
I think the semi-rigid nature of rock wool could also mean that mods will be more durable and less likely to shift. But that's conjecture.