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Fostex T50RP Incremental Mods and Measurements - Page 23

post #331 of 1215
I finally got around to grabbing a hole punch for the bassholes in the stiff felt over the driver. I put ten 1.8mm holes in each. I also cut small 1/4" bass ports in the stiff felt over the vents. The results are, like the last bowl of porridge, just right.
post #332 of 1215
Quote:
Originally Posted by PhaedraCorruption View Post

Someone should give Mr.Clean Magic Erasers a try. I don't have any on hand but I just stumbled across the fact that they are made from this stuff: http://en.wikipedia.org/wiki/Melamine_foam which is also sound foam. 

At least a couple people tried this muuuch earlier on in the thread...couldn't tell you how long ago, but I think it was abandoned.

post #333 of 1215

Try a treble reflector in above shape and punch a hole in stiff felt at the center for bass. 

post #334 of 1215
Quote:
Originally Posted by kingoftown1 View Post

At least a couple people tried this muuuch earlier on in the thread...couldn't tell you how long ago, but I think it was abandoned.

Indeed, seems that wool-type materials have significantly better absorption than foam materials. So it's likely preferrable to use fiber instead of foam as cup filler. Though still, impedance matching is present, so a boundary layer of foam (e.g. in cup wells) would be beneficial. That could also explain improvement brought by "ladder rungs" in DBVs - they provide another intermediate impedance between foam and fiberglass, better matching them.

However, there is a place for foam, IMO. It could be used under the pads as a structural angler and sound absorber under the earpads - where fiberglass won't work well due to not enough stiffnes and elasticity. Also I personally use a slice of melamine foam backed by rigid luffa sponge to evenly press felt against the driver.

MuZo2
A good idea! A "semi-transparent" reflector.
I have also been thinking about using a covered treble reflector, i.e. not just pressing an completely airflow-stopping material against the driver, but also using a thin, 0.5mm layer of felt between it and the driver. Don't know what the effect could be, though, really.
post #335 of 1215

I'm actively searching out some acoustipack lite alternatives :) I'll update if I find anything good!

post #336 of 1215
Quote:
Originally Posted by Nevod View Post
MuZo2
A good idea! A "semi-transparent" reflector.
I have also been thinking about using a covered treble reflector, i.e. not just pressing an completely airflow-stopping material against the driver, but also using a thin, 0.5mm layer of felt between it and the driver. Don't know what the effect could be, though, really.

 

    Ok in my iterations I have done following
1) Used disc/square like BMF, mids were good but found bass to be lacking and also some harshness on high
2) Used pattern above and bass is stronger but still some harshness on the highs
3) Used very soft tissue which is in microns placed over treble reflector and felt and it removes the harshness.

I will add some pictures and measurements during weekend.

post #337 of 1215

I have been toying with the idea of making wooden cups, ala Smeggy.  Does anyone know of any plans or a guide to do this?  I know that Smeggy said, at one time, that he would share his plans, but I don't think he ever did.  My thought was to transfer most of the DBV#3 mods to wooden cups and go from there.

post #338 of 1215

Well guys, I found what I was looking for.  Now I just have to decide whether to do it, how to go about it, and if it would be worth the effort.  I think I will probably do some reading on basic speaker design before I expend much effort..
 

post #339 of 1215

Any recent word on where some of the "real" Rite Aide cotton can be had? No stores around here, I'd love to buy enough for 1 pair of headphones from someone.

post #340 of 1215
I've been playing around with variations of dmv#3 for a while and have been using masking tape to assemble it between mods. Tonight I have put the screws in and I have lost something. It does not seem as vibrant. Has anyone else encountered this. Buy the way It was fairly tight and there were no gaps in the masking tape.
My current incarnation is dmv#3 with 4 holes in the felt over driver and a 16mm diameter reflector, I've tried a few things to get more bass but every time I do they lose clarity, I might try muzo2's star reflector next. How big was the hole in the felt when you tried it and what was the diameter of the star?

I got a pair of t50rp's of eBay and they arrived today. Yuk. Give me dmv#3 anyday.
post #341 of 1215
Thread Starter 
Quote:
Originally Posted by jiminy View Post

I've been playing around with variations of dmv#3 for a while and have been using masking tape to assemble it between mods. Tonight I have put the screws in and I have lost something. It does not seem as vibrant. Has anyone else encountered this. Buy the way It was fairly tight and there were no gaps in the masking tape.
My current incarnation is dmv#3 with 4 holes in the felt over driver and a 16mm diameter reflector, I've tried a few things to get more bass but every time I do they lose clarity, I might try muzo2's star reflector next. How big was the hole in the felt when you tried it and what was the diameter of the star?

I got a pair of t50rp's of eBay and they arrived today. Yuk. Give me dmv#3 anyday.

 

Yes, I have noticed a difference when tuning with masking tape to secure the baffles to the cups compared to using the screws. IME, going from tape to screws increases the bass which may effect the perceived bass:treble "ratio." I find that I lose some treble and gain some bass when I switch from tape to screws. I don't know if this effect is due to the slight difference in the amount of compression of the dampening materials (greater compression when using the screws), better seal with the screws, or a combination of the two. It seems counter-intuitive to me because I would expect greater compression to emphasize the treble. Whatever, 5 to 10 mm compression of cotton/fiberglass is about "right" for me.

 

Whatever is going on, I try to compensate for this compression effect by using about 5 mm less thickness of cotton when tuning and using masking tape to hold the baffles to the cups. I always make sure I apply positive pressure against the baffle "face" and the back of the cup when applying masking tape around the rims, overlap each tape segment, and press the tape into the rim groove and then fold it over onto the rounded part of the baffle "face."  I do this in an attempt to get the closest approximation to the compression when using the screws. No matter how careful I am, however, I always see some "spring" by pressing on the baffles after applying the tape all the way around the rims.

 

You could try removing 5 mm (just a few layers) of cotton and re-test using the screws to hold the baffles to the cups. Next, replace the 5 mm of cotton you removed and Add another 5 mm of cotton, and re-test...compare to what you heard with your initial build and after removing 5 mm of cotton. Go with the setup that sounds best. 

 

You may also be able to compensate for the "compression effect" by altering the size/number of holes in the stiff felt and/or the size of the treble reflector. I've found that more/larger holes=more bass and larger treble reflector=more treble. Only 1 mm difference in size of the "bass boost" holes and 2 or 3 mm difference in size of the treble reflectors results in significant differences in the sound. Consider, as well, making a temporary "bass port" by applying a strip of masking tape on the outside of the cup vents. There is a guide for making a temporary bass port in Post #1 of this thread. Also, there's a guide for making a permanent bass port. Note that a "bass port" decreases bass quantity a little bit while tightening or improving bass quality.

 

See "Tuning Suggestions" in Post #1 of this thread after "Simplified and Consolidated DBV #3 Pictorial, located after Graph #55.  Make only one tuning "tweak" at a time because each mod component interacts with all the others. The only way to assess a tuning tweak is in isolation. IME/IMO, proper preparation of the cotton and fiberglass is crucial for euphonics...see the associated guides.

 

Good luck and YMMV, of course.

post #342 of 1215

Has anyone tried the Mr. Speakers Alpha pads with any of the DBV mods.  It seems that the 840 pads fit my head OK, but a tighter fit might help and I know the 840 pads are a little loose below my ears.

post #343 of 1215
Quote:
Originally Posted by chinook9 View Post

Has anyone tried the Mr. Speakers Alpha pads with any of the DBV mods.  It seems that the 840 pads fit my head OK, but a tighter fit might help and I know the 840 pads are a little loose below my ears.

 


I'm using the Dog Pads on a variation of the DBV 3, while waiting for the alpha pads to arrive. Right now, they're very comfortable, and adds a nice and subtle boost to the bass. I can only imagine that the alpha pads would be even better based on the testimonies by beta testers of the alpha pads.

post #344 of 1215

This thread was infinitely helpful for my mods. Thanks.

 

Would anyone care to describe what adding plasticine does to the sound? OP's graph depicting it also included the felt and acoustipack.

post #345 of 1215
Quote:
Originally Posted by BobSaysHi View Post

This thread was infinitely helpful for my mods. Thanks.

 

Would anyone care to describe what adding plasticine does to the sound? OP's graph depicting it also included the felt and acoustipack.


This is for baffle mass-loading, essentially making the baffle itself heavier and better able to deal with vibrations ( more resistant ) that would affect the driver itself in a minor way. Like what some folks do with ultra-heavy speaker stands they fill with sand and marble footings etc. Ensures the driver is unaffected as much as possible by any extra vibrations that would come from the baffle plastic.

  Basically.

 

There was recent talk also  of not bothering with this, and/or using rigid struts from carbon fibre instead to strengthen/stiffen the baffle rears up. I am sure you'll get some various opinions as to which is best, hopefully with reasonings why.

 

Oops I may have read the post of yours wrong, apologies .  You probably already know that stuff  and were looking for direct comparisons between plasticine and no plasticine sonic differences. I would think possibly ever so slightly cleaner sound? though I only ever tried the puttied version out. Seemed the easiest way to eliminate a possible variable. If my second set has nothing I will try that as is.


Edited by nick n - 2/13/13 at 8:23pm
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