[symphonic]

Today I took the velour pads off of my pair of Audio Technica AD700s to clean them. I used that as an opportunity to see how they would sound with the Beyerdynamic gel pads. I was hoping for a bit of extra bass + comfort. Tweaking the Fostex T50RP has shown how important the pads are.
 
...I measured the response using my in ear WM61a microphone and Room EQ Wizard, driven by a Xonar DG. It was ridiculous. My head was rumbling from 20 Hz to about 400 Hz (a straight line) before the frequency response came back down to Earth. The overall sound was unbalanced but there was 
 
I'm thinking now that Audio Technica has tweaked these to be moderately bass light on purpose. The drivers on these headphones are huge, so there's nothing to stop bass response if the pads allow it. Padless, they are bassier than the Fostex T50RP (also padless). My expectation now is that the bass can response can be extended on the AD700 by sealing the pads a bit better - either new pads or adding something to seal the sides. The huge airy sound might suffer, but it already has that in spades.
 
Hopefully I'll find time to play with these and post some results with different ear pads. 

 

[Digital-Pride]

Nice!  Keep us updated on your findings.

 

[TMRaven]

I did this to my DT990s with Denon pads.  While I wouldn't say the bass got stronger, but it made the headphone dark.  Darker than dark.  It turned into a black hole.
 
 

 

[symphonic]

Yes the balance really was messed up with the gel pads. What I have in mind at the moment is to adjust how much air can vent from the velours so that more pressure can build up. I'm stitching some other pads for my T50RPs - I can measure those on the AD700s when they are ready.
 
AD700 pads on the T50RPs make them VERY bass shy. 
 
Quote:

I did this to my DT990s with Denon pads.  While I wouldn't say the bass got stronger, but it made the headphone dark.  Darker than dark.  It turned into a black hole.
 
 

 

 

[Phos]

The stock pads make them essentially open front headphones.  They don't seal at all stock.  

 

[DVDRey]

 
Quote:

The drivers on these headphones are huge, so there's nothing to stop bass response if the pads allow it.

 
Its not really the size of the driver that makes the difference, but how drivers are tuned. A 35mm driver can have more bass than a 50mm driver, but, of course, with similar settings a bigger driver ll have bigger bass.
 
AD700 is bass light, even with the best changing, their driver ll not have the bass from the pro700MKII, also a 53mm driver.

 

[symphonic]

Once the velours have dried out I'll post a plot of no pads vs stock pads - you're right, the stock pads are crazy leaky. Then I'll wrap some cling wrap around them and see what happens.
 
EDIT: I'm back with some plots, using an in ear (blocked ear canal) WM61a microphone via my Xonar DG. I didn't set the absolute dB scale. Volume settings are the same throughout.
 
First up - no pad in purple vs the stock pad in green. This is my left ear. The stock pad really is quite linear!

 
Next up, the Beyerdynamic gel pad in blue vs the stock pad in green. The gel pad totally captures the bass pressure but isn't so kind to the mids.

 
Now the Superlux 668b vinyl/pleather pad in purple vs the stock one in green. The FR is more reasonable here and probably could be tuned pretty nicely.

 
Next I wrapped cling wrap around the edge/rim of the stock pad for a makeshift seal. The result is in yellow. Similar to the Superlux 668b pad except without the 2-3kHz dip. 

 
What do you guys think? It seems that if I want more bass I just need to make a removable belt to go around the stock pads. Boom!

 

[symphonic]

Updated with measurements. ^ 

 

[Phos]

This makes me wish I had thrown in a set of W1000 pads for my AD700's in with the W5000 pads I'm getting for my A900's.  

 

[kingpage]

How does your DIY in-ear WM-61A look? The cable wasn't in the way?

 

[symphonic]

Here's what my prototype looks like. At some point I will make custom moulds to hold them, for absolute consistency of placement. Consistency between measurements on different days is still good though.
 
Such a little cable is basically transparent for audio and also doesn't prevent a good seal. 
 
I made these to tune my T50rp woodies, and also for speaker/HRTF measurements. So far it's a good investment! I don't have a pre-amp yet but it's not even really necessary. You get a good enough signal to noise ratio straight into a sound card. 
 
 

Quote:

How does your DIY in-ear WM-61A look? The cable wasn't in the way?

 

 

[kingpage]

That looks simple and nice.
 
Here's some testing rig that caught my eyes.

Source: http://www.johncon.com/john/wm61a/
 
It seems a few other people use plastic tubes to act as an ear canal, but then different lengths give us different high frequency peaks. I have been reading up on the reflection/absorption coefficient of human skin. Human skin is acoustically rigid with a close to 1 reflection coefficient for frequencies between 1khz and 6khz. Using something hard wouldn't be a bad idea actually. It's really trade-off between an actual ear shape for the right reflection or an artificial tube for the right distance and resonator.
 
I forgot that REW5 is free. I don't feel like registering...  Could you upload it to megaupload for me please?

 

[TMRaven]

 
That is a very nice frequency response chart.  Almost looks like an AKG701 with less sub-bass rolloff.  Must show pics of how you modded the actual thing!

 

[SanjiWatsuki]

Wow. That's impressive. I wonder if a similar effect to the Superlux pads could be had from using AKG K240 pads. 

 

[symphonic]

Sorry for the delay in responding - had a hectic few days.
 
I thought a little about the tube idea as well, which might be good for IEMs. With open headphones, the blocked air canal measurement has a chance to work well because the ear canal will be introduced correctly on playback if the ear chamber is close enough to free air. For closed headphones I think that you really need the mic close to the ear drum. Smyth Research use blocked measurements so I'm hoping that they are good enough. 
 
@TMRavan - the yellow curve there is just with a layer of cling wrap around the outsides of the pads. Right now the T50RPs are my priority but I'll play more with these as well. First up is comfort - so adding stuff in the ear pads to get them off of the ears. If that seals some air then the bass response should be elevated as for these curves. Then I'll probably add a detachable pleather rim to the ear pads
 
The AD700 pads are so acoustically transparent that I would think any of the velours from other pads would add bass response. Unfortunately I don't have any real life friends with other pads to try. Note, though, that the AD700 pads are oversized - roughly 11 cm I think.