[funkle II]

Sorry if this has been discussed. I searched these (and other) forums and didn't find much on this, so have started a new post. I find my AQ Nightawks to be mostly articulate, but I noticed that some tracks containing mostly mids with not much high or low frequency content, like solo piano recordings, seemed muddled and distorted. When I ran a variable frequency generator in an attempt to find the offending frequency range, I noticed that there was a +/-165hz ring that existed from around 100hz to 1000hz. It is sort of a ghost note that occurs along side whatever frequency is being played within that range. It is strongest right at 165. There are also some additional intermodulate notes that become apparent when toggling between low, medium & high setting on my amp. I tried this with two different signal chains and other tone generators and had the same result. Out of curiosity, I tried some other headphones as well. It turns out that they do the same thing around the same frequency, but a little different. Not sure if this is something going on in my own hearing, other equipment or in the headphone, but I did read that all headphones do have a resonant frequency, which comes up when testing their response. Has anyone else noticed this, or care to try this themselves?

Experimenting with the PEQ in Roon, I set a band-stop at 165hz (essentially a narrow, but complete cut at a selected frequency). This has removed much of the muddled mids with little negative side effects, and made solo piano listenable on these headphones.

 

[Scgorg]

The resonance frequency of a headphone is typically aiming to be as low as possible for an over-ear design (acoustic engineering is all about tradeoffs, however, so nothing is quite that simple). The majority of over-ear headphones, and probably also the Nighthawk will have a resonance frequency in the 50-100hz range barring some extreme outliers (the RAAL SR1A has a resonance frequency of under 30hz for example). The resonance frequency is where both the drivers acceleration and excursion are at their highest. Excursion is constant below resonance but drops above resonance while acceleration is constant above resonance but drops below it (at a rate of 12dB/octave).

In a pressure chamber the excursion is the determinant of SPL. In other words the constant excursion below resonance means that a driver will be flat below resonance while it drops above. This is the opposite of free air (speakers/earbuds/"earspeaker" type designs) where the acceleration is the determinant of SPL (so bass rolls off but high-frequency extension is good). What is important to note is that a driver can be working both in a pressure chamber and in free air at the same time, as it is frequency dependent. In short, the smaller the chamber the higher the frequency it will work under pressure chamber conditions is. Some people reading this might now think "so then drivers drop off above resonance at a rate of 12dB/octave similar to what speakers do below resonance frequency?" which is precisely correct. Because the pressure chamber effect depends on volume, however, this means that many of our beloved over-ear headphones work as if they were in free air at high frequencies and pressure chamber at low frequencies, thus making it possible to get an extended frequency response on both ends without going to the extremes that speakers do (good luck finding a speaker with the extension of a sealed front volume electrostat or planar)!

Now you might be thinking that this has absolutely nothing to do with what you are hearing, which is true! The resonance frequency of the headphone shouldn't have any impact on the sound by itself, certainly not in the way you are describing. Dynamic headphones usually have a rather large impedance hump at their resonance frequency which should actually help avoid things such as this, due to an even higher damping factor than the rest of the frequency range. What you are hearing might be any number of things, but it is very doubtful that it is related to the resonance frequency of the driver.

 

[Oscarilbo]

wrong post