Phase reversed coherence on cheap monitor systems, Behringer and 002?

[Quantum J Audio]

Hi,

I was checking some mic amps I built recently and noticed when flipped the phase I was experiencing some bass roll off. 

I eventually worked out that this was happening in the monitor path, a Behringer minimon).  Inverting the phase on a source recorded outside my system using a plug-in results in the same outcome.  This occurs on headphone and monitor o/p's.

On discussing this with  a friend, he also discovered his 002 does exactly the same.  I know these are both cheap monitoring systems, but can anyone explain why cheap units are causing a slight bass roll off.

We both are considering a monitoring DIY build, but would want to avoid something that might create the same outcome.

 

[RuudNL]

When you listen to yourself on a headphone, you hear two things:
Your own voice 'inside' your head AND your voice through the headphone.
You will notice a difference in LF response when the headphone is 'out of phase' with the 'direct' signal through your head.
Also you will notice that is easier to speak or sing when both signals are in phase.
In fact YOU are the only person hearing the difference. If you let somebody else listen to the same headphone, he or she won't probably hear any difference!

 

[MagnetoSound]

Inverting the phase on a source recorded outside my system using a plug-in results in the same outcome.  This occurs on headphone and monitor o/p's.

... can anyone explain why cheap units are causing a slight bass roll off.

While Ruud's comments are valid, if this is indeed happening with pre-recorded sources as well, it may well be that they have skimped on cap values.

 

[okgb]

or less likely that there is poor loading , less than optimum impedance match
[ although you'd think this unlikely in this day & age  ] the first & only time I plugged something into
an Alto product , it had an obviously un-natural sound to it , that cheap or bad ??

 

[Quantum J Audio]

When you listen to yourself on a headphone, you hear two things:
Your own voice 'inside' your head AND your voice through the headphone.
You will notice a difference in LF response when the headphone is 'out of phase' with the 'direct' signal through your head.
Also you will notice that is easier to speak or sing when both signals are in phase.
In fact YOU are the only person hearing the difference. If you let somebody else listen to the same headphone, he or she won't probably hear any difference!

Definitely not in my head, as it is happening on monitors too.  Also happens on two setups in two different places with two engineers.  A 002 system and an HD system with a behringer minimon.  We've never heard this on large format consoles.  Just on our more affordable home setups.

or less likely that there is poor loading , less than optimum impedance match
[ although you'd think this unlikely in this day & age  ]

Certainly possible.  You pay peanuts we seem to be getting monkeys. 

The quest for a suitable and affordable DIY solution continues.

Thanks for your comments.