A sweep of DT770 Pro shows FLAT BASS RESPONSE - what's wrong?

[va3ttn]

I just performed a sweep of Beyerdynamic DT770 Pro headphones
(mine is a very old 600 Ohm version) from 1 Hz to 200 Hz.

From what I read, I expected to find a very exaggerated
low frequency response, but found nothing of a kind.

According to this sweep:
* -3 dB frequency is ~22 Hz
* -6 dB frequency is ~15 Hz
* YES, they do have some response on 5 Hz
* NO, I didn't find any significant low frequency bust,
frequency response was quite flat, and the largest peak
was merely 1 dB at 50-90 Hz, which is pretty negligible.

Measurement procedure is described in the attached picture.

So, I must have done something very wrong

All comments are welcome.

EDIT:
Just checked equipment flatness from microphone input:
10 Hz : -1.65 dB
20 Hz : -0.45 dB
30 Hz : -0.19 dB

So, it's not equipment fault. Perhaps the microphone?

Could it be that my DT770 Pro actually has a flat bass response

 

[milkweg]

Why is there such a big spike at 50hz? It shows 6db spike. That seems odd. They are Pro model which means they are for studio use so should be flat. That's why I am second guessing some people who say 990 (2005) are better than 990pro. I prefer a flatter frequency response than one that accentuates the lows or highs.

 

[va3ttn]

Quote:

Originally Posted by milkweg /img/forum/go_quote.gif Why is there such a big spike at 50hz? It shows 6db spike. That seems odd.

As explained in the picture, spikes at 50 Hz and 121 Hz
are due to room noise, nothing to do with headphones.



Quote:

Originally Posted by milkweg /img/forum/go_quote.gif They are Pro model which means they are for studio use so should be flat.

Well, it's a well known fact here that DT770 Pro
headphones are bass-heavy, which is contrary to my results.

Therefore, I must be wrong. But where?

 

[Fitz]

How do these measurements compare to the rest of the frequency response? Your results only show that the bass itself is fairly linear (typical for headphones), but not how loud or soft the bass is compared to the rest of the spectrum.

 

[Punnisher]

I believe the bass heavy version is the 770 pro 80ohm. I have that model and indeed the bass is very heavy.

The other models that are 250ohm and 600ohm are though to be more natural sounding. I haven't heard those though.

 

[Acix]

The signal above the 0db boost as from 50-130 (bass + low mid).

 

[va3ttn]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif How do these measurements compare to the rest of the frequency response? Your results only show that the bass itself is fairly linear (typical for headphones), but not how loud or soft the bass is compared to the rest of the spectrum.

The response continues flat toward 1 kHz or higher.
That's why I zoomed on the most interesting part of spectrum.

 

[Fitz]

1KHz is still not enough to get an idea of the overall frequency response, you'll want to go to at least 10KHz.

 

[va3ttn]

Quote:

Originally Posted by Acix /img/forum/go_quote.gif The signal above the 0db boost from 50-130 (bass + low mid).

That only 1 dB or less, which is not bass-heavy by any stretch of imagination.
Actually, it's quite difficult to notice such a small change
even when one knows it's there.

Please pay attention to the vertical scale.
It's only 1 dB per division, not 10 or 20 as in other sweep diagrams.

 

[va3ttn]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif 1KHz is still not enough to get an idea of the overall frequency response, you'll want to go to at least 10KHz.

Overall frequency response is beyond me at the moment.

There is no point in attempting 10 kHz measurements
before I get everything in place in the bass region.

Was anybody able to confirm "bass-heaviness" of DT770
Pro by his own measurements?

 

[Fitz]

That's the whole point though... you can't tell if they're bass heavy or not by measuring a very limited frequency range. You have to take the measurements at different frequencies relative to the measurements as a whole; they don't have very much meaning in isolation.

 

[va3ttn]

DT770-2006 response on HeadRoom site is fundamentally different from my sweep:

They got a much more spectacular response with 8 dB notch
on 45 Hz, where the wavelength is over 7 meters.

Well, I couldn't imagine a way for such a simple oscillatory system
to have a response as complex as having this narrow notch
at 45 Hz, and my sweep shows nothing of a kind,
just an ordinary well-behaved high pass response.

 

[va3ttn]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif you can't tell if they're bass heavy or not by measuring a very limited frequency range.

10 Hz to 1000 Hz is NOT a very limited range as far as the bass in concerned.
Actually, it's more than we need to judge the presence or absence of bass-heaviness.

In other words, whatever the response over 1 kHz,
it cannot make the sound bass-heavy (or bass-light).
This property is defined in concrete long before we reach 1 kHz.

 

[Fitz]

It's also a different headphone and measured in a different manner.

I'm not sure why you're so against measuring a full sweep of the frequency response?

 

[Fitz]

Quote:

Originally Posted by va3ttn /img/forum/go_quote.gif 10 Hz to 1000 Hz is NOT a very limited range as far as the bass in concerned. Actually, it's more than we need to judge the presence or absence of bass-heaviness. In other words, whatever the response over 1 kHz, it cannot make the sound bass-heavy (or bass-light). This property is defined in concrete long before we reach 1 kHz.

I just applied a high shelf eq to attenuate all frequencies above 1KHz, playing music through some smallish bookshelf speakers that have a fairly limited bass response. Guess how they sound? Dark, muddy, and bassy.

EDIT: Listened that way for a couple minutes to adjust, then turned off the filter, making them sound painfully bright and thin by comparison. All this just by adjusting the frequencies over 1KHz. I thought it was supposed to be "defined in concrete" within the sub 1KHz frequencies?