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Fostex T50RP Incremental Mods and Measurements - Page 5

post #61 of 580
8/6/12 at 8:31am

just curious whether youve tried how the bare stock cans sound without the back cups installed. So meaning totally free air in design. And also how do the 840 pads sound with the same totally open back design/no mods on driver except to take off the cups altogether

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post #62 of 580
8/6/12 at 8:56am
Thread Starter 
Quote:
Originally Posted by donunus View Post

just curious whether youve tried how the bare stock cans sound without the back cups installed. So meaning totally free air in design. And also how do the 840 pads sound with the same totally open back design/no mods on driver except to take off the cups altogether

 

Yes, I have. As you might expect, they sound thin with no bass. Am I correct in assuming you're interested in free-field measurements, perhaps for calculating your HRTF?

 

Here's the Measurement Chain:  

 

MacBook Pro with REW > McIntosh MX-136 pre/pro for pre-amp > Dacmini with 1 ohm output impedance for amplification > Panasonic Electret Mic > Phantom Power Supply > MacBook Pro for analysis and graphing by REW

 

If there is any interest, I can upload "windowed" vs free field measurements for T50RP and B&W 803S tower speaker using the same Measurement Chain.

 

I made a "windowing chamber" using a cardboard box and took measurements. The back of the driver was separated from the back of the chamber by ~20 cm, IIRC.

 

Next, I taped the same Panasonic electret microphone on a tripod and measured free field response of my B&W 803S at 1 meter. Before doing so, I moved the speaker to the center of the room with at least 8 feet clearance all the way around the speaker. 

 

This was not my project. A friend requested these specific measurements for calculating his HRTF.

 

I also have pictures of the "windowing chamber" aka cardboard box.  LOL

 

I will measure the open back stock T50RP with Shure 840 pad and post the results on the database at Post #1.

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post #63 of 580
8/6/12 at 9:05am

Does this can have to or should have an amp that can maximize its potential?

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post #64 of 580
8/6/12 at 9:10am

Great, thanks! I was just curious more than anything because based on speakers like magnepan magneplanars, they like to be positioned at least a few feet away from the wall for them to sound their best. The bass actually gets thin when you stick them beside the wall unlike dynamics which gives the opposite boomy sound when stuck beside the wall. I was thinking maybe what if a deeper cup enclosure was built for the fostex cans. maybe something like 2 inches deep? :)


Edited by donunus - 8/6/12 at 4:24pm
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post #65 of 580
8/6/12 at 10:17am
Quote:
Originally Posted by haquocdung View Post

Does this can have to or should have an amp that can maximize its potential?

 

Yes, I think an amp is highly desired when using the T50s.  When stock, the efficiency is high - up in the 98dB range.  However, after the damping materials and modifications get applied, the efficiency drops to 92dB, or close to that level.  Through the modification process, the Fostex is turned into an orthodynamic beauty.  And, as with most - if not all orthodynamic headphones, an amp is a great piece of gear to piece with them.

 

Also, keep in mind, the orthodynamic drivers are capable of handling a lot of power.  They can handle more power from an amp than a regular headphone, with dynamic drivers.  The Fostex T50, when stock, specs of it handling 3,000mW of power.  There was just another headphone with dynamic drivers that I was reading about - I believe the AKG K701, which is rated to handle 200mW of power.  That is quite a large variance.

 

I really think that if anyone is looking for a pair of headphones that doesn't need an amp, they should just focus on some IEMs.  Stick with in-ear earbud headphones.  Even an efficient headphone, will still love the current supplied by an amp and perform better with a better body to your music when the amp is used.

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post #66 of 580
8/6/12 at 1:21pm

I disagree, I don't think an amp fixes anything with the T50rp, it just makes them better.  They sound great out of an ipod.  Just not to their full potential, but they'll never get to their full potential, a better amp and source just gets them closer to it. 

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post #67 of 580
8/7/12 at 3:25pm

Hello guys,

 

It's my first post here: very nice forum!!!! 

I'm sorry for my english but I'm from Italy.

 

Looking at the first post of this 3d i suppose that the best waterfall should be the N. 9 because all ends in 200ms.

 

It's correct?

 

Calibro.

 

PS Compliments to BMF !!!!

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post #68 of 580
8/8/12 at 5:55am
Thread Starter 
Quote:
Originally Posted by calibro View Post

Hello guys,

 

It's my first post here: very nice forum!!!! 

I'm sorry for my english but I'm from Italy.

 

Looking at the first post of this 3d i suppose that the best waterfall should be the N. 9 because all ends in 200ms.

 

It's correct?

 

Calibro.

 

PS Compliments to BMF !!!!

 

Number 9 is fast, yes, but it likely still has resonance problems since it's stock + modified bass port, only. DBV #2 is also fast, And flat.

 

If you care to try any of my mods, I recommend DBV #2 as described in Post #1 of this thread. Go to the sections describing the mod configuration for DBV #1 and DBV #2.  Look at Graphs 56-61.

 

Follow the written guides for DBV #1 with DBV #2 mods Plus one little change:

 

Install the Transpore, or cut a rectangle of the desired size from a glossy magazine cover, and place one or the other Under the stiff craft felt. This change increases treble without effecting bass/mids. Use thin double sided tape on the driver grid lines to hold the paper in place.  Implementing this one change to the configuration may require reducing the amount of cotton/fiberglass you use.

 

Every mod must be tweaked, individually, even when you follow anyone's mod configuration Exactly.

 

Best wishes

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post #69 of 580
8/8/12 at 9:19am

Thank you for the replay!!!

 

It seems a little bit strange that the N. 9 waterfall (that don't use damping material) is faster than the following (that uses damping material).

 

What do you think about=?????

 

;-)

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post #70 of 580
8/8/12 at 9:41am

So I decided to recable my T50-RP, big mistake.  The wires came loose, so I figured I will just solder the wire back in, well, the warning is true.  Soon as I put my solder iron on solder, the film melted out, and the entire thing is ruined.

 

Oh well, now my bass-heavy set is gone, and I am left with my bass-light set.  I am thinking of getting another one and modding it.

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post #71 of 580
8/8/12 at 5:32pm

It's possible to use a Musical Fidelity A1 Class A integrated amp (20 watt X2) with those Fostex T50RP ??

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post #72 of 580
8/8/12 at 5:39pm
Quote:
Originally Posted by calibro View Post

It's possible to use a Musical Fidelity A1 Class A integrated amp (20 watt X2) with those Fostex T50RP ??

 

Yes, but watch the volume level.  The Fostex T50s are capable of handling 3,000mW of power.  Other dynamic headphones are at times, only capable of 200mW for total power.  Again, keep an eye one the volume level.

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post #73 of 580
8/8/12 at 5:44pm

You'd most likely suffer some serious hearing damage before the fostex blow.  Just recable those bad boys to balanced.

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post #74 of 580
8/8/12 at 6:01pm

Your ears will blow out before the Fostex will.

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post #75 of 580
8/9/12 at 7:17am

OK, I understood that I've to watch at volume level !!!!   So no problem with the power.

 

My Musical Fidelity A1 was modded by Aurion Audio in Italy (no op amps, full discrete class A circuit, Alps blue pot, low feedback, improved power supply and caps, cc coupled, ecc...).

 

Do you think the quality will be enough for a Fostex T50RP ???

Or the headphones amps has more sound quality than a speaker amp?????

 

Thank you !!!!

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