[1GoodEar]

First, I am very new to this so any clarification on how to best ask these questions would be appreciated  Second, I did do a search, but did not find the answer.  If it has already been answered and it would be easier to just point me to the discussion thread I will look there.
 
A little background.  I have Shure 940s and a Fiio e7 DAC/Amp.  As most folks have already written, the bass is bit lacking on those headphones.  Which is the basis of where my question comes from.
I primarily listen to music from my iPad.  All the files I listen to are mp3s from iTunes.  They are all 256K encoding, which is obviously ok but not great.  I have no 320K, lossless, CDs, or any other form of music that could change the outcome.  I listen to various types of music, but the genre of the music did not change the perception of the difference I will be referring to.
 
I use an app on the iPad called "Equalizer"
 
Question: Can someone explain the science difference (if there is one) between "boosting" up the bass with a "bass booster" setting in the EQ app on the iPad vs doing the same thing within the amp?  I set the e7 to setting 1 on bass booster.  In each case I set the side i am not boosting the bass up with to a flat EQ.
 
The reason I ask the question is that when I increase the bass output with the EQ on the iPad, it sounds natural, and what I was hoping for and more in balance with the mids and highs for the 940s.  When I used the Fiio e7 to increase the bass, it sounded forced or unnatural.  (not the audiophile nor scientific terms I know, but those are the best terms I could come up with to describe what I was hearing).
 
For reference, I use the camera connector kit so the e7 is being used as a DAC as well as an amp on the iPad.  In the e7 there is a bass booster option; 0=off,  1, 2, and 3 for low, medium and high increases in the bass boost. 
 
While I realize a response I could get is, "if you like the response/sound your are getting from the EQ setting on the iPad, just use that."  While I get that, I am trying to learn if there is something I do not understand that would explain the difference in the sound.  I am an engineer by education so I understand tech details, but just not the science of how and why.  that is what I am trying to learn.
 
So if there is a reason for the difference, please help a newbie out

 

[EthanWiner]

What you might be missing is that equalizers have different frequencies, and also different bandwidths. A fully parametric EQ can give just about any curve. I don't know the specifics of what you have. This might help:
 
The Art of Equalization
 
--Ethan

 

[mikeaj]

Right, the relative amount of boost (cut) at every single frequency is quite likely to be different between one bass boost and another.  This is most likely the explanation.  E7 bass boost 1 setting increases the baseline volume by 1dB and the lowest bass by 2.5dB more (3.5 dB in all), with a gradual rolloff—it's still about 2.5 dB in all at 100 Hz, so it's boosting the midrange a bit too.  I don't know exactly what the software is set to do, but it could very well be boosting 5dB, 10dB, 2dB... who knows... and at different frequencies.
 
Even if the magnitude vs. frequency plot is identical, the phase vs. frequency may be different.  Some use linear phase filters; others use minimum phase; others may yet do something else.  Furthermore, some EQ settings in some devices may actually be doing something in addition to just EQ.

 

[1GoodEar]

Thank you. 
 
So are you saying there is not (or at least should not be) a difference between boosting on the iPad itself with the EQ vs doing it in the amp?
 
Being a bit simplistic, Wouldn't canned "bass Booster" EQ settings do basically the same thing within the low end freqs?  For ex, the EQ in the iPad boosts the low freqs between the bottom end up to 1000Hz.  The curve is concave downward with the peak at 40Hz being 6dB.  Then sloping downward gradually until the 156Hz mark at 4dB  156Hz is the inflection point changes the curve to be concave upward and brings the apmlitude down much quicker whereby the boost is near zero by 300Hz and slopes very gradually from there to zero dB at 100Hz.
 
I do not know what the EQ in the amp is doing though. 

 

[mikeaj]

It's a long story (don't ask), but there is a review of the E7 on the web that shows what the EQ settings do.  Actually, it could be multiple places, but search around for "E7 measurements" for a blogspot site and then search that page for "bass eq measurements" and you should find the graph eventually.
 
The E7's canned settings are quite different than what you're describing for the iPad.
 
It should be that you can find EQ in software and hardware that can be matched to do pretty much exactly the same thing, but these are definitely not matched like that.

 

[1GoodEar]

sorry missed a zero the last line should be a 1000Hz not a 100Hz
 
Thanks.  sounds like there is more reading I need to do to understand all the input factors that can change the output, thus affecting the sound.
 
I saw the link on the understanding Equalization, is there anything else that would be helpful to better understand what else is in play?