CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

Lobby => Headphone Measurements => Topic started by: stratocaster on November 24, 2014, 05:13:32 PM

Title: Open T50RP
Post by: stratocaster on November 24, 2014, 05:13:32 PM
Inspired by the new open-back Fostex T500RP, I decided to experiment on my own open version. Woudn't have thought it could work, but it did. Drivers are damped and I was using HM5verlour pads. These sound really balanced and smooth.

Title: Re: Open T50RP
Post by: aufmerksam on November 24, 2014, 05:45:53 PM
Ha! Those look awesome. I like the upgrade to less-cheap headband compared to your other creations, especially the added strain-strap.
Title: Re: Open T50RP
Post by: Marvey on November 24, 2014, 05:47:38 PM
Wowza!

But as I feared, the small driver doesn't like pushing bass in an OB.
Title: Re: Open T50RP
Post by: Claritas on November 24, 2014, 06:08:03 PM
Very nice work! Ishcabible was trying to help someone in Boston (?) with a similar project. Both of us thought it was pretty unlikely to sound decent. What damping scheme did you go for?

I can't wait till Marv or Tyll measures TH500RP and puts that thread out of its solitary misery.
Title: Re: Open T50RP
Post by: spoony on November 24, 2014, 06:13:28 PM
That's very interesting, great work!
Title: Re: Open T50RP
Post by: RexAeterna on November 24, 2014, 06:42:36 PM
Amazing job strat. Always was thinking of making my t50rp open but my carpeting skills is shit. Stuffing my cups with high density fiberglass did good enough job for me.
Wowza!

But as I feared, the small driver doesn't like pushing bass in an OB.
Bass looks fine to me. I think it was smart using the thick pads. Headphones are coupled dependent.  I was thinking replacing my shure 840 pads with some omegas or something one day but probably never gonna get around doing it.
Title: Re: Open T50RP
Post by: stratocaster on November 24, 2014, 07:10:22 PM
What damping scheme did you go for?
You have to dampen the driver quite tightly. I used a layer of felt, topped with some damping paper and another layer of foam that keeps the damping felt/paper pressed against the driver.
The pads are essential. I have been testing pads extensively, and as all of you know the pads make a huge difference. Those who say this isn't so should see the wildly different frequency response plots when you swap pads (see attached pic of alpha pads on the same setup)  I always start with pad rolling to see which pad has the best potential for the driver. The secret is synergy. Synergy between driver plus pads plus enclosure. Damping will do the rest of what is possible within this combination.
Title: Re: Open T50RP
Post by: Solderdude on November 24, 2014, 08:02:05 PM
Nice work ! (yet again) on the wood and most likely the sound.
Would have loved to hear that one....

Having a rig really pays off when modding.
I believe it is almost obligatory if you want to get it right.
They are a great 'handle on reality' when modding by ear.

The seemingly high distortion in the lower frequencies isn't distortion but is caused by a poor S/N ratio of the used mic/pre-amp.
Doesn't really matter for CSD's nor for FR measurements.


Title: Re: Open T50RP
Post by: spoony on November 24, 2014, 08:18:29 PM
I have been testing pads extensively, and as all of you know the pads make a huge difference.
Have you played with the Shure alcantara pads?
Title: Re: Open T50RP
Post by: stratocaster on November 24, 2014, 08:47:45 PM
Have you played with the Shure alcantara pads?
No, I haven't.
Title: Re: Open T50RP
Post by: riker1384 on November 25, 2014, 12:08:33 AM
So, since there's a whole industry of modded closed T50RPs, any chance that someone will sell something like this?

Although, after mods, done in small quantities, it could end up in HD600 price territory. Does it have any advantages over those?
Title: Re: Open T50RP
Post by: stratocaster on November 25, 2014, 06:35:15 AM
So, since there's a whole industry of modded closed T50RPs, any chance that someone will sell something like this?
Although, after mods, done in small quantities, it could end up in HD600 price territory. Does it have any advantages over those?
In my opinion there is nothing you can  recommend  as unequivocally as a (used) HD600. In fact it has been my reference headphone for quite some time now and I always find myself trying to tune my headphones to its sound signature. As for an open T50, there are hours and hours of work involved and I doubt - if you do that on a small scale - that they could be sold as cheap as a (used) Hd600. Sonically my open T50RPs are a step ahead of my HD600, comfort is better with the Senns though.
Title: Re: Open T50RP
Post by: RexAeterna on November 25, 2014, 03:04:16 PM
You have to dampen the driver quite tightly. I used a layer of felt, topped with some damping paper and another layer of foam that keeps the damping felt/paper pressed against the driver.
The pads are essential. I have been testing pads extensively, and as all of you know the pads make a huge difference. Those who say this isn't so should see the wildly different frequency response plots when you swap pads (see attached pic of alpha pads on the same setup)  I always start with pad rolling to see which pad has the best potential for the driver. The secret is synergy. Synergy between driver plus pads plus enclosure. Damping will do the rest of what is possible within this combination.


I would of just used some fiberfill/pillow stuffing with combination of open cell foam if something really needed to be in the cups. Don't want too much density ehen working with open baffles/cups. Foam factory is great place to get different types of foam at different densities.

But how you did it worked out fantastic as well so, you know...


Title: Re: Open T50RP
Post by: Deep Funk on November 25, 2014, 03:26:15 PM
That is impressive.
Title: Re: Open T50RP
Post by: spoony on November 25, 2014, 06:31:15 PM
Strato: Have you tried these pads with a closed mod?
Title: Re: Open T50RP
Post by: stratocaster on November 25, 2014, 06:53:29 PM
Strato: Have you tried these pads with a closed mod?
Yes I did, I am enclosing a quick comparison of the FR curves. The closed version was not bad, and I am sure that one could straighten out the FR curve of the closed version with some effort. It's just that I wanted to try an open setup.
I am really curious about measurements of the Fostex T500RPs  ...
Title: Re: Open T50RP
Post by: spoony on November 25, 2014, 07:00:15 PM
Thanks, looks like these pads are a great match with the T50RP.
Title: Re: Open T50RP
Post by: Ishcabible on November 27, 2014, 09:35:50 PM
Very nice work! Ishcabible was trying to help someone in Boston (?) with a similar project. Both of us thought it was pretty unlikely to sound decent. What damping scheme did you go for?

I can't wait till Marv or Tyll measures TH500RP and puts that thread out of its solitary misery.

The problem with the configuration was that the guy making the cups was adamant about using really thin cups so I couldn't really damp them at all. He's planning on using thicker cups from now on to let me experiment, and hopefully it turns out this well!
Title: Re: Open T50RP
Post by: stratocaster on November 30, 2014, 07:48:31 PM
Just 'opened up' my Ebony T50RPs. Using modified HM5 pleather pads this time, overlay enclosed. Makes me wonder why I hadn't thought of that modding move earlier...



Title: Re: Open T50RP
Post by: spoony on December 02, 2014, 07:34:29 PM
Wow, what did you do to those pads?
Title: Re: Open T50RP
Post by: dreamwhisper on December 02, 2014, 09:03:04 PM
Is that freq response adjusted for HRTF?

I greatly admire your work by the way. Keep it up. :money:
Title: Re: Open T50RP
Post by: stratocaster on December 03, 2014, 04:31:52 PM
Since I am not doing in-ear measurements,  I am not using any compensation.  I am using a rig that was inspired by Solderdude's. Pic is enclosed. I kind of 'calibrated' my rig with measurements that Solderdude did of my headphones on his rig and checked if my rig produced the same results.

As for the pads, I am experimenting on some pad mod at the moment. Measurements seem very promising  but I want to do some further tests before I post more about it.
Title: Re: Open T50RP
Post by: rklm on December 16, 2014, 05:03:24 PM
I was just finishing up the CAD for a laser-cut can design for the t50rp driver when I came across this post... and now you've got me thinking that changing my design might be for the better!

Is the baffle in your open mod solid or porous?

Like... For example... Here is a screen cap of my vectors (closed can):
(click to show/hide)

Below the main structures are the alternates for an open can:
(click to show/hide)

Also... What made you choose that enclosure? Are there any physical dimensions (besides the walls of the cans which you mentioned earlier) that are particularly conducive to better audio quality?

Great post, by the way!
Title: Re: Open T50RP
Post by: stratocaster on December 16, 2014, 05:47:24 PM
I just used some enclosures I had lying around. The baffle is solid wood, without any vent or port. I am using a modded pad, though. It seems to work with the closed T50RPs too.
Recently I bought a used Mayflower T50RP, which sounded and measured horrible btw. I left the damping untouched, just applied my pad and the attached pic shows how it measures compared to my open T50.

Yellow is open T50, red is closed Mayflower. Both setups use the 'StratoPad'.




 
Title: Re: Open T50RP
Post by: rklm on December 16, 2014, 05:57:09 PM
Wow... That is incredible.

I guess I have to look into pads a bit more.

I was looking at these (http://www.ebay.com/itm/1-pair-New-Replacement-ear-pad-cushion-For-Sony-MDR-XB1000-Headphones-ear-pads-/251509460098?pt=US_Replacement_Parts_Tools&hash=item3a8f21cc82) for the sake of ridiculousness and comfort... but if the sound quality is changed that much, something more specific and open might just be the way.

Did you notice a significant change in clarity/imaging/sound stage between the open t50rp and the mayflower with the same pads?
Title: Re: Open T50RP
Post by: stratocaster on December 16, 2014, 06:07:10 PM
It is a  Mayflower V2, which normally comes with some velour pads. But my set came with the HM5 leather pads of the Mayflower V3 and it measured like this...
Picture 2 compares Mayflower V2 (red), Mayflower plus Alpha Pads (purple) and Mayflower with HM5 velour pads.
Title: Re: Open T50RP
Post by: spoony on December 16, 2014, 06:10:11 PM
I just used some enclosures I had lying around. The baffle is solid wood, without any vent or port. I am using a modded pad, though. It seems to work with the closed T50RPs too.
Recently I bought a used Mayflower T50RP, which sounded and measured horrible btw. I left the damping untouched, just applied my pad and the attached pic shows how it measures compared to my open T50.

Yellow is open T50, red is closed Mayflower. Both setups use the 'StratoPad'.

That's pretty awesome, so all that has to be done is to tame the honk at 1 KHz with some damping and install a pair of stratopads, huh?

Following the business philosophy around headphone forums you should be charging $500 for the pads alone :boom:
Title: Re: Open T50RP
Post by: stratocaster on December 16, 2014, 06:19:28 PM
Did you notice a significant change in clarity/imaging/sound stage between the open t50rp and the mayflower with the same pads?

Actually they sound pretty much the same. The closed ones have a little more energy in the mids and are a tad less balanced. I will have to look into that and see if this can be dealt with by changing the damping.
Title: Re: Open T50RP
Post by: spoony on December 16, 2014, 06:26:40 PM
Is your last iteration based on the HM5 pleathers?
Title: Re: Open T50RP
Post by: rklm on December 16, 2014, 06:31:24 PM
Ok. I guess acrylic is cheap, so I will just have a set of open backs and closed backs cut, and I can play with it from there.

I am really surprised to see the graph of the mayflowers with the alpha pads... those pads are so highly regarded... but that FR curve is practically sporadic in comparison to the measurements from your custom pads before.

Do you plan on parting with the secrets to your pad mod?  8)
Title: Re: Open T50RP
Post by: spoony on December 16, 2014, 06:36:04 PM
Do you plan on parting with the secrets to your pad mod?  8)

He already did (http://www.head-fi.org/t/618659/fostex-t50rp-incremental-mods-and-measurements/1470#post_11129039) (not sure if last iteration).
Title: Re: Open T50RP
Post by: stratocaster on December 16, 2014, 07:07:00 PM
Is your last iteration based on the HM5 pleathers?

No, I prefer the velour pads. The highs are smoother with them.
Title: Re: Open T50RP
Post by: rklm on December 16, 2014, 07:11:36 PM
Ah, I found it here (http://www.head-fi.org/t/618659/fostex-t50rp-incremental-mods-and-measurements/1470#post_11129039)

Btw, you sir, are a gentleman and a scholar.

I am so excited to play with this configuration now!
Title: Re: Open T50RP
Post by: spoony on December 16, 2014, 07:56:17 PM
No, I prefer the velour pads. The highs are smoother with them.

Nice, did you spend a lot of time tuning the open-cell foam vs felt thickness on your new pads?, is it critical for balanced response?
Title: Re: Open T50RP
Post by: stratocaster on December 16, 2014, 08:19:13 PM
Nice, did you spend a lot of time tuning the open-cell foam vs felt thickness on your new pads?, is it critical for balanced response?
If you have this sound-leaking felt ring between baffle and pad, you have to adjust the damping behind the driver to achieve a good balance. If you dampen your driver tightly, this may result in elevated highs. Then you can try to bring down the FR curve from 3 - 10 kHz with a layer of foam in the pad bottom. I tested/measured the effect of several materials and foam (like the one in a Grado S-cush) does the job best.
Title: Re: Open T50RP
Post by: spoony on December 16, 2014, 10:11:29 PM
In your last iteration are you still using that foam donut on the 'ear side' of the pad?
Title: Re: Open T50RP
Post by: stratocaster on December 17, 2014, 05:14:58 AM
In your last iteration are you still using that foam donut on the 'ear side' of the pad?

Yes.