Fostex T50RP Incremental Mods and Measurements

[wje]

Quote:

The cotton is frustratingly important. Seriously, I couldn't believe how important.. It's just dumb cotton, right? 

 
It's kind of like the whole argument about high fructose corn sweetner vs. cane sugar.  While, yes, they both can make a beverage tasty; one is truly "more" natural and has proven itself for many, many years ... and, there is no real good substitute for that.

 

[bluemonkeyflyer]

Quote:

http://www.mp3forkidz.com/mic/mod.html
 
This is link to linkwitz mod.
 
I used Riteaid cotton balls, Separated them evenly and layered  them in cups. Not sure how much weight they are.Followed the DVB #3 instructions for rest of the steps.

Thanks for the link.
 
RE: Rite Cotton Balls -That can work. FWIW, I like to start with 2x7x7 cm (1.7 g.)  Rite Aid Natural Absorbent Cotton OR 2x6x7 cm (1.5 g. = 10 separated layers). I use a $20 digital scale with calibration weight I picked up from Amazon last year. Seems to work great and helps me channel balance from Left to Right as well as standardize my mods. A scale might come in handy for you.
 
RE: Your lack of treble - Could be you don't have enough cotton and/or you haven't "fluffed" them enough. You could also try a larger treble reflector such as going from 18 mm to 20 mm. If you punched any holes in your stiff felt, you could try fewer holes or smaller holes. Whatever tweaks you make be sure to only do one at a time or you won't know what works and what does not work in your mod.  
 
Quote:

The cotton is frustratingly important. Seriously, I couldn't believe how important.. It's just dumb cotton, right? 

 
Yes, the right cotton "Density:Fluffiness" factor is important. Dense, matted cotton just does not perform like Rite Aid Natural Absorbent Cotton or other brands properly prepared.

 

[nicholars]

Looking at these FR graphs it would appear that these are pretty bass light out of the box...
 
But simply by adding some tape to the cups with a bass port and changing the pads they actually look like they have a very good bass response right down to about 20hz?
 
I was just wondering if someone who has tried these mods could tell me if this is the case? Or are the graphs being misleading?
 
I am thinking of getting some T50rp + some new pads and doing the basic mods, I am a little concerned that they may not have enough bass response after reading comments about the bass response from people on the stock versions....
 
Do these have good bass with the basic mods? Certainly looks like they do from the graphs anyway.
 
 
Also has anyone tried these with shure or beyer velour earpads?

 

[chinook9]

Quote:

Looking at these FR graphs it would appear that these are pretty bass light out of the box...
 
But simply by adding some tape to the cups with a bass port and changing the pads they actually look like they have a very good bass response right down to about 20hz?
 
I was just wondering if someone who has tried these mods could tell me if this is the case? Or are the graphs being misleading?
 
I am thinking of getting some T50rp + some new pads and doing the basic mods, I am a little concerned that they may not have enough bass response after reading comments about the bass response from people on the stock versions....
 
Do these have good bass with the basic mods? Certainly looks like they do from the graphs anyway.
 
 
Also has anyone tried these with shure or beyer velour earpads?

 
 
I believe you are correct about the bass response.  I have the DBV#3 just as described earlier in this thread, including the tape over the ports with the 1mm x 3mm vents.  I have not yet tried blocking the small port that is up next to the driver.  
 
I do most of my testing using Pink Floyd and Dire Straits and there is really low bass on a few of those tracks.   I have been impressed that the planar drivers can do this well on the low end. 

 

[PhaedraCorruption]

I removed the stock white paper on the back of my drivers awhile ago and I think I may have lost them. Anyone have any ideas what would act as a good substitute for the stock stuff? 
 
I have tried thick wool felt, transpore, and micropore already with very little luck. Perhaps a different configuration would do better?

 

[bluemonkeyflyer]

I removed the stock white paper on the back of my drivers awhile ago and I think I may have lost them. Anyone have any ideas what would act as a good substitute for the stock stuff? 


 


I have tried thick wool felt, transpore, and micropore already with very little luck. Perhaps a different configuration would do better?

This thread --> Page 17 -->. Post 244

 

[PhaedraCorruption]

Quote:

This thread --> Page 17 -->. Post 244

Perfect. Thanks!
 
 I get this godawful dip at around 4.43k. Anyone have any ideas of how to remedy this?
 

 

[MuZo2]

Quote:

Perfect. Thanks!
 
 I get this godawful dip at around 4.43k. Anyone have any ideas of how to remedy this?
 

Is this with stock pads ? If you see graphs from 1st page you can see changing the pads to shure or FA-003 will help.

 

[PhaedraCorruption]

Quote:

Is this with stock pads ? If you see graphs from 1st page you can see changing the pads to shure or FA-003 will help.

Yup. Thanks for the tip.
 
I just tried stuffing some foam under my pads to space them like the 840 pads would do.
 

 
 
I get this as a result.
 

 
 
For some reason ALL my measurements seem to be in the high DB range.. 

 

[MuZo2]

I guess that is because of REW setup

 

[bluemonkeyflyer]

Perfect. Thanks!

 I get this godawful dip at around 4.43k. Anyone have any ideas of how to remedy this?

Hard to say without more information. Please:

Describe your config in detail.
Post pictures.
Show the rest of your graph with all scales present.
What is the resolution of your graph?
Show a stock measurement you made.

 

[PhaedraCorruption]

This is where I'm at after opening the back vent(only stock felt installed) and removing some felt I had over the front of the driver.
 

 
 
I'll post my full mods tomorrow. 

 

[bluemonkeyflyer]

Quote:

Yup. Thanks for the tip.

I just tried stuffing some foam under my pads to space them like the 840 pads would do.





I get this as a result.





For some reason ALL my measurements seem to be in the high DB range.. 

Sorry. I should have linked this with the previous one.

Go to Post #1 in this thread and you will see links to my Google Docs. There you will be able to see how to configure REW.

On this graph, click the Gear icon at top right. Enter -70 in the offset window and click Add to data. Go to left vertical slider to pull the adjusted Graph down until you can see it. Then, adjust your resolution. You're currently at 20 dB intervals which gives an inaccurately flat FR. Click the Zoom in (+) button at the top Left of the graph window and change the resolution to 5 dB for a more accurate indication of your mod FR. After making these adjustments, you can now select the Waterfall and Spectrogram tabs at the top and generate these graphs to complete your analysis.
 
I'm guessing that when you change to 5 dB resolution that your graph will look pretty close to stock T50RP.

Hope this helps.

 

[PhaedraCorruption]

Quote:

Sorry. I should have linked this with the previous one.

Go to Post #1 in this thread and you will see links to my Google Docs. There you will be able to see how to configure REW.

On this graph, click the Gear icon at top right. Enter -70 in the offset window and click Add to data. Go to left vertical slider to pull the adjusted Graph down until you can see it. Then, adjust your resolution. You're currently at 20 dB intervals which gives an inaccurately flat FR. Click the Zoom in (+) button at the top Left of the graph window and change the resolution to 5 dB for a more accurate indication of your mod FR. After making these adjustments, you can now select the Waterfall and Spectrogram tabs at the top and generate these graphs to complete your analysis.
 
I'm guessing that when you change to 5 dB resolution that your graph will look pretty close to stock T50RP.

Hope this helps.

thanks for all your help.
 
I Just went through the guide but I have a couple of questions.
 
Why did you choose to calibrate the soundcard with the phantom power supply as a package and not just the soundcard alone as suggested by the REW setup guide? 
 
Also, in the guide why did you suggest to plug the OUT from the phantom power supply to the MIC IN on the computer and not the LINE IN? Is this because the macbook you were using at the time only has a MIC IN and no LINE IN? 

 

[bluemonkeyflyer]

Quote:

thanks for all your help.
 
I Just went through the guide but I have a couple of questions.
 
Why did you choose to calibrate the soundcard with the phantom power supply as a package and not just the soundcard alone as suggested by the REW setup guide? 
 
Also, in the guide why did you suggest to plug the OUT from the phantom power supply to the MIC IN on the computer and not the LINE IN? Is this because the macbook you were using at the time only has a MIC IN and no LINE IN? 

 
It's been 18 months since I read through REW's setup instructions. I don't remember the specifics about what was recommended, then, and the instructions may have changed. I'll have to check the current setup instructions. I do remember calibrating both ways, though, and saw no significant difference between looping the sound card alone vs adding the phantom power supply in the loop calibration. I chose to go with calibrating the sound card with the phantom power supply because there was no apparent difference and I figured it wouldn't hurt to remove any bias that might be associated with the phantom power circuit. Others who were/are also using REW for headphone measurements concluded that calibrating with the phantom power in the loop seemed the best way to go, too.  They're on this forum and may have some comments to share based on their experience. In any case, the measurements I made of my Stock T50/40/20RP's and my LCD2's are similar to other published measurements, with slight differences as shown in the graphs. Take the graphs as FWIW and YMMV, etc., and compare them to one another, not to others' measurement graphs; the same caveat applies for each individual's measurements.
 
RE: MIC IN vs LINE IN - I stated "MIC IN" because my MacBook Pro icon is a "Mic" but to be more accurate should have said "LINE IN." Sorry for any confusion.
 
Were the settings adjustments I suggested for your graphs helpful? If you tried them, what did you find?