Paul WB5AGF
New Head-Fier
My interest in headphones goes through periods of activity and then inactivity. Ten years ago (2012) I bought a pair of Sony MDR-7509HD Headphones and then 'put-them-away' (I don't remember why). Quite recently I pulled-them-out-of-a-box (being rather surprised as I'd forgotten them) and began to analyze their performance.
What I have found is that their frequency response is very bothersome ... there is a 'hole' in the 200 - 500 Hz range (per reviews that I've found on-line) that results in the headphone's acoustic signature giving the peculiar sensation of the sound being 'hollow'. If I dial-in an appropriate amount of gain in the 'Equalizer APO' software on my PC then the MDR-7509HDs sound fairly good so I feel reasonably confident that the 200 - 500 Hz 'hole' is the problem.
I've been working with some other Sony headphones to learn how their frequency responses are derived and I'm of the opinion that roughly 80 percent of how a pair of headphones sound comes from the driver. The physical environment that the drivers are mounted in certainly contributes to the sound but you can only 'pull' a driver's performance so far (the old expression about not being able to 'make a silk purse out of a sow's ear' comes to mind).
When I went looking for the marketing hype from Sony back when the MDR-7509HDs were released much was made of the 50mm drivers (after pulling off one of the ear pads, and then looking at the driver in one of the ear pieces, it appears as though Sony was trying to create some unique sound signature but I don't know what that would be). The MDR-7509HDs are the only earphones I've seen where a special structure was molded into the ear piece where a bit of intentional leakage from the ear piece cavity to the opening facing the listener's ear took place. Some other Sony earphones I've looked at have a series of holes around the driver where all but one of the holes (typically) are blocked with a tape-like material. In the MDR-7509HD there is a 'duct' where the leakage takes place.
I've tried completely blocking the leakage path (from the closed ear piece housing to the outside) and the characteristic sound didn't seem to change very much.
Does anyone know if there is some peculiarity to the physical structure of the 50mm drivers used in the MDR-7509HD Headphones which lead to the 'hole' in the frequency response or have I not yet stumbled onto some cunning bit of design in the earpiece housing which is causing it ?
(signed)
Paul, WB5AGF (my Amateur Radio Call)
What I have found is that their frequency response is very bothersome ... there is a 'hole' in the 200 - 500 Hz range (per reviews that I've found on-line) that results in the headphone's acoustic signature giving the peculiar sensation of the sound being 'hollow'. If I dial-in an appropriate amount of gain in the 'Equalizer APO' software on my PC then the MDR-7509HDs sound fairly good so I feel reasonably confident that the 200 - 500 Hz 'hole' is the problem.
I've been working with some other Sony headphones to learn how their frequency responses are derived and I'm of the opinion that roughly 80 percent of how a pair of headphones sound comes from the driver. The physical environment that the drivers are mounted in certainly contributes to the sound but you can only 'pull' a driver's performance so far (the old expression about not being able to 'make a silk purse out of a sow's ear' comes to mind).
When I went looking for the marketing hype from Sony back when the MDR-7509HDs were released much was made of the 50mm drivers (after pulling off one of the ear pads, and then looking at the driver in one of the ear pieces, it appears as though Sony was trying to create some unique sound signature but I don't know what that would be). The MDR-7509HDs are the only earphones I've seen where a special structure was molded into the ear piece where a bit of intentional leakage from the ear piece cavity to the opening facing the listener's ear took place. Some other Sony earphones I've looked at have a series of holes around the driver where all but one of the holes (typically) are blocked with a tape-like material. In the MDR-7509HD there is a 'duct' where the leakage takes place.
I've tried completely blocking the leakage path (from the closed ear piece housing to the outside) and the characteristic sound didn't seem to change very much.
Does anyone know if there is some peculiarity to the physical structure of the 50mm drivers used in the MDR-7509HD Headphones which lead to the 'hole' in the frequency response or have I not yet stumbled onto some cunning bit of design in the earpiece housing which is causing it ?
(signed)
Paul, WB5AGF (my Amateur Radio Call)
