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Fostex T50RP Incremental Mods and Measurements - Page 38

post #556 of 1156

Damn, I was hoping you didn't do anything irreversible! Oh well, if I fiddle with it and have anything worth talking about, I'll bring it back here.

post #557 of 1156

It shouldn't make *that* much of a difference... just shove a piece of felt on top and see how it sounds. I for one am leaning more towards front side damping these days, mostly because it's so much easier than opening up the cups every time rolleyes.gif

post #558 of 1156
Quote:
Originally Posted by Armaegis View Post

It shouldn't make *that* much of a difference... just shove a piece of felt on top and see how it sounds. I for one am leaning more towards front side damping these days, mostly because it's so much easier than opening up the cups every time rolleyes.gif

Absolutely. Last night I tried just adding a disk of stiffened felt and it didn't change the sound much. I got some extra DT770 pads lying here so when I get home from work I'm going to take the dust protector disk and lay that in under the Alphas... If my hypothesis is correct, the bass should definitely go up and the treble should mellow out a little.

post #559 of 1156

i just got some dog pads; prefer the 840 pads.  Was going to give people here first dibs before I post them in the FS forums.... PM me.

post #560 of 1156

Switched back to 840 pads.

 

*bows down to 840 pads*

post #561 of 1156

You've given up on the Alpha pads? 

 

I'm listening to my modded T50rp's with the Alpha pads right now and I actually like what I'm hearing. I haven't listened to them in a week, but coming back to them they sound good. My least favorite part of what I am hearing is the upper mid-bass, and lower mid-range. They just seem to be too strong in this area and sound congested here. I had the same issue here with the 840 pads though as well. If not for this one flaw I'd like them a whole lot. I guess they are just to warm. 

 

Has anybody figured out how to decrease the response in this area without EQ? 

Quote:
Originally Posted by Thujone View Post

Switched back to 840 pads.

 

*bows down to 840 pads*


Edited by jasonb - 5/13/13 at 5:36pm
post #562 of 1156

My Alphas were causing a lot of sibilance with my setup. They also had a midbass peak that recessed the lower mids a little -- didn't notice this as much until I got the 840's back on. I went through some amp/DAC switching so I wanted to try the original modding setup with the 840s and I love what I hear. My friend is about to mod his first pair of T50RP's and he already has the Alphas, so I'm gonna convince him to fine tune them and he'll have mine to compare to. If I like his mod, I will definitely switch back to the Alphas.

post #563 of 1156

Hmmm, I'm not hearing any sibilance. The treble on mine is smooth and extended, and just a tad darker than I'd really like. If there was about 3db less in the 150-300hz area I'd be extremely happy with them right now. They just sound a little too busy in this small area.

 

Does anybody know what a second layer of the stiffened craft felt on the back side of the driver would do?


Edited by jasonb - 5/13/13 at 6:18pm
post #564 of 1156
Thread Starter 
Quote:
Originally Posted by jasonb View Post

Hmmm, I'm not hearing any sibilance. The treble on mine is smooth and extended, and just a tad darker than I'd really like. If there was about 3db less in the 150-300hz area I'd be extremely happy with them right now. They just sound a little too busy in this small area.

Does anybody know what a second layer of the stiffened craft felt on the back side of the driver would do?

Not sure about your mod config and audio chain but, generally, an extra layer of felt should further damp them. A 4 mm modified bass port will lower the FR centered around 100 Hz by 3 or 4 dB, in my experience. As always, your results and opinions may well differ.

Good luck with your tuning.
post #565 of 1156

I'm honestly not hearing much of a difference between a fully open rear(with the stock felt) and a bass port even smaller than 4mm.  

Quote:
Originally Posted by bluemonkeyflyer View Post


Not sure about your mod config and audio chain but, generally, an extra layer of felt should further damp them. A 4 mm modified bass port will lower the FR centered around 100 Hz by 3 or 4 dB, in my experience. As always, your results and opinions may well differ.

Good luck with your tuning.
post #566 of 1156
Thread Starter 
Quote:
Originally Posted by jasonb View Post

I'm honestly not hearing much of a difference between a fully open rear(with the stock felt) and a bass port even smaller than 4mm.  

Measurements of my modded sets consistently show a 3 dB attenuation between ~ 90 to 150 Hz when I install a 4 mm bass port at the center of one of the 4 cup vent slots; the rest of the slots and remainder of the one with the bass port are sealed. I usually put it on the second one from the bottom. This works for me on T20/40/50RPs. Maybe you're under damped for your "ears and gears?" That's about all I can suggest.

Best wishes.
Edited by bluemonkeyflyer - 5/14/13 at 12:24am
post #567 of 1156

i currently have too much hissing highs or treble:

 

i didn´t cut the scotch tape(lengthwise in half) when applying so it covers a bit of the driver.i´m not sure if this hightens the "hiss"? i also put a reflex dot in the middle like in the tut and i covered the bass vent on the outside with tape and made a 3mm opening.

 

so my questions would be if the scotch tape works as a reflector too adding to the hiss and should i cut it in half? i also saw that transpore was uesed to fixate the felt but is it necessary if scotch double sided tape is underneath the felt.

 

i guess i´ll have to wait a while until alterations to the HP cos i ran out of dough:)

 

further mods are cotton balls and the usual paxmate filling the cup floor and adding plastillin to the driver enclosure.


Edited by superdux - 5/14/13 at 4:40pm
post #568 of 1156
If the double-sided tape is covering some of the driver's back side (i.e. it's not thin enough and sit slightly outside of the grid (see the picture plox)) that could be it, since it's not sonically porous. Looking at your post again, it could probably be this:
Quote:
i didn´t cut the scotch tape(lengthwise in half) when applying so it covers a bit of the driver

I also figure that the transpore tape around the felt would make it like a porous chamber, since transpore isn't absolutely opaque. What I mean is that I can blow air through it, while I can't with regular tape, for example. That, based on my limited knowledge on sound physics, will effect the sound.

Maybe BMF can chime in with a better response. :P
post #569 of 1156
Thread Starter 
Quote:
Originally Posted by superdux View Post

i currently have too much hissing highs or treble:

 

i didn´t cut the scotch tape(lengthwise in half) when applying so it covers a bit of the driver.i´m not sure if this hightens the "hiss"? i also put a reflex dot in the middle like in the tut and i covered the bass vent on the outside with tape and made a 3mm opening.

 

so my questions would be if the scotch tape works as a reflector too adding to the hiss and should i cut it in half? i also saw that transpore was uesed to fixate the felt but is it necessary if scotch double sided tape is underneath the felt.

 

i guess i´ll have to wait a while until alterations to the HP cos i ran out of dough:)

 

further mods are cotton balls and the usual paxmate filling the cup floor and adding plastillin to the driver enclosure.

Anything over the back of the driver directly dampens it. If the material is non-porous (like Scotch tape, self-adhesive felt, thin card stock, etc.) it will work like a reflector = reduce bass & increase treble. Generally, too much damping with foam, cotton, fiberglass, wool, etc. will reduce bass and increase treble.

 

Transpore tape was used in the early stages of Incremental Mods and Measurements only for securing the stiff felt to the driver. It is not needed if you use double sided tape but make sure the double sided tape does not cover any of the rear driver grid spaces.

 

Go to Post #1 in this thread, scroll down past Graph 55, and look at the photos in "Simplified and Consolidated DBV #3 Pictorial" and "Tuning Rules of Thumb."

 

Best wishes for successful tuning :)

 

Quote:
Originally Posted by jgray91 View Post

If the double-sided tape is covering some of the driver's back side (i.e. it's not thin enough and sit slightly outside of the grid (see the picture plox)) that could be it, since it's not sonically porous. Looking at your post again, it could probably be this:
I also figure that the transpore tape around the felt would make it like a porous chamber, since transpore isn't absolutely opaque. What I mean is that I can blow air through it, while I can't with regular tape, for example. That, based on my limited knowledge on sound physics, will effect the sound.

Maybe BMF can chime in with a better response. :P

 

Sounds about right to me.


Edited by bluemonkeyflyer - 5/15/13 at 5:58am
post #570 of 1156
Thread Starter 

FYI: I edited and moved all pictorials and tutorials to the bottom of Post #1. The modding guides are better organized and now easier to follow.

 

I have some additional editing to do and a few more pictures to update....eventually.

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