CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

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Author Topic: The headphone technology thread...  (Read 5537 times)

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ultrabike

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Re: The headphone technology thread...
« Reply #50 on: April 15, 2015, 08:12:51 AM »
Quote from: purr1n on April 15, 2015, 06:42:15 AM
Interesting - forgot about the sealed / pressure aspect of orthos. (open-back, but a sealed arrangement, not dipole "open" where the backwave interferes with the front.)

You could argue the greater mass / greater momentum "fights" against the increasing force / pressure as the diaphragm is displaced from zero position.

If the pressure is represented by the Incredible Hulk (stronger as he gets displaced more), a thin low mass diaphragm would be like Loki charging at him, and a thick high mass diaphragm would be like Ironman in Hulkbuster armor.

They way I see it, the driver diaphragm and the air volume may be seen as a single mass. The compression of this whole mass is what we hear. The compression may not be uniform in 3-D space.

How the diaphragm and it's physical properties (surface area, thinness, composition, tension...) affect the sound is proly a complicated and frequency dependent matter. I've seen some stuff here and there about it:

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/630#post_8783923

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/585#post_8738868

Regarding bass, consider the case of leaky dynamic headphones. The dynamic driver designed for these cans may have relatively more displacement freedom and may be able to compress quite a bit of air in the ear vicinity up to a certain low frequency floor w/o seal. However, low bass may still be hard to drive for leaky cans relative to other cans that offer better seal characteristics. Leaky HD600s for example don't go as deep and may have higher distortion in the low frequencies. Same with AKG 7xx and Beyer DTxx0s. Some orthos and electrostats maybe open back, but they may not be leaky, and maybe able to go low in frequency, as long as a good seal is provided. I still remember that LCD-X and the Stax impressions/measurements.

Quote from: gurubhai on April 15, 2015, 07:46:00 AM
I think what Marv is saying that the thin stat diaphragms when tensioned tend to gain an inertia which negates the speed/acceleration benefit of their lower mass. They end up requiring to overcome an initial threshold before they start moving which might mean that at some very low level signal the diaphragm may not move at all and end up losing that low level information.

That is indeed an interesting thought.
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MuZo2

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Re: The headphone technology thread...
« Reply #51 on: April 15, 2015, 08:39:30 AM »
Thinner the better is not always true , low-frequency characteristics are closely related to stiffness and equivalent mass of the system.
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Tachikoma

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Re: The headphone technology thread...
« Reply #52 on: April 15, 2015, 03:19:29 PM »
An electrostatic driver membrane has resistance to movement due to tensioning, but that's linear, whereas inertia implies that it works more like a cliff.

Edit: Basically what OJneg said. The resistance should be perfectly linear at the starting point, and should increase exponentially at large excursions.

Re: Reactance of electrostatic drivers, Frank Verwaal (http://home.kpn.nl/verwa255/esl/esl_home.html) says that due to the proximity effect, which increases bass SPL at very close distances, an electrostatic headphone should have a flat frequency response with a constant voltage drive, whereas electrostatic speakers need a constant current drive to sound flat.
« Last Edit: April 15, 2015, 04:08:24 PM by Tachikoma »
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ultrabike

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Re: The headphone technology thread...
« Reply #53 on: April 15, 2015, 04:07:17 PM »
Maybe the trade off (for sealed cans) is not so much about whether the diaphragm can reproduce low frequencies or not (at least up to a certain point because things will likely tank eventually), but about how efficiently it can do it as a function of frequency. Perhaps thinner diaphragms with sufficient tension and stiffness may do well in mids and treble, but may become inefficient in the bass area. The frequency at which the bass will dramatically drop off may also be a function of diaphragm thickness.

This may seem obvious to some, but wasn't so much for me.

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Anaxilus

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Re: The headphone technology thread...
« Reply #54 on: April 15, 2015, 04:13:25 PM »
Well, the Stax Omega is one of the greatest phones ever for mids (if not the greatest ever) but the bass was always lacking to me. More so than it's modern counterparts the 007/009. I actually find that properly driven the 009 can really kick up the bass impact with the right synergy. I have bounced the driver off the stators before using the right amp and this track:

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Tachikoma

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Re: The headphone technology thread...
« Reply #55 on: April 15, 2015, 04:26:50 PM »
I think, having the diaphragm too thin means that the "non-linear" point comes up at a lower SPL than a thicker diaphragm made of the same material. Bass signals tend to be larger in amplitude than high frequency signals in music, so those signals reach the "non-linear" boundary sooner, which translates into a thin sound. All this might be negligible if we could make diaphragms out of spider silk or graphene though.
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Anaxilus

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Re: The headphone technology thread...
« Reply #56 on: April 15, 2015, 04:35:34 PM »
So we need a Michelin headphone with carbon nanotubes.
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Solderdude

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Re: The headphone technology thread...
« Reply #57 on: April 15, 2015, 04:37:16 PM »
In that case measuring the FR at 60dB and 90dB the bass levels should differ and distortion should rise.
Tyll's plots of the SR009 at 80 and 90dB show the SR009 has low distortion in the bass and the distortion gets better (lower) at a 10dB higher SPL.
No sign of 'clipping' at 90 dB, but who knows at 100dB.



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Use your ears to enjoy music, not as an analyser.

Tachikoma

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Re: The headphone technology thread...
« Reply #58 on: April 15, 2015, 04:41:52 PM »
Not really, as long as it operates completely within the linear region of the diaphragm material. Also, an electrostatic driver does not have increased bass distortion because given the same signal amplitude, the excursion is the same as it is at high frequencies.

I just came up with this explanation about 15 minutes ago, so I don't really know if I'm right. :P
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ultrabike

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Re: The headphone technology thread...
« Reply #59 on: April 15, 2015, 04:57:33 PM »
Quote from: Solderdude on April 15, 2015, 04:37:16 PM
In that case measuring the FR at 60dB and 90dB the bass levels should differ and distortion should rise.
Tyll's plots of the SR009 at 80 and 90dB show the SR009 has low distortion in the bass and the distortion gets better (lower) at a 10dB higher SPL.
No sign of 'clipping' at 90 dB, but who knows at 100dB.

That's proly due to noise floor in the equipment pre-amps. Likely the non-linear distortion levels do rise.

Quote from: Tachikoma on April 15, 2015, 04:41:52 PM
Not really, as long as it operates completely within the linear region of the diaphragm material. Also, an electrostatic driver does not have increased bass distortion because given the same signal amplitude, the excursion is the same as it is at high frequencies.

I just came up with this explanation about 15 minutes ago, so I don't really know if I'm right. :P

Nah, I think electrostatic drivers do have an excursion increase for low frequencies vs high frequencies.
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