Feel free to ask questions. I'll do my best to answer.


Tuesday, September 24, 2013

Old Creative Computer Speakers

I've always graphed speaker that have been considered good or great by many audio enthusiasts.  Just for comparison I did a set small computer speakers.

I chose these little Creative speaker simply because someone I know has them in everyday use.

I didn't move the speaker around as I normally would and I did them fullrange in my QuasiAnechoic Chamber.

Well here we go:

  Tone controls adjusted for bass emphasis, Flat, and for treble emphasis:

Overlaid:

Time domain stuff:



This time I decided to make impulses of this speaker so that others might be able to get a glimpse of what these sound like by using the convolution process.  I accidentally bumped my microphone in the process so I rechecked to see my new measurement and then I'll compare it to the measurement of the impulse:


Pretty much identical if I could get them to size up exactly.

Thursday, September 19, 2013

Anechoic Chamber


That's a waste high view from the entrance
It made of Roxul covered by local fabrics.  Approx 2meters cubed. 

ADAM A3 for first go round with stuffed ports


All well and good, but what's in measure in there?










Sunday, July 14, 2013

Behind the Headphone Measurements

Here's the 'in room' measurements made with the microphones not in my ears and in the sweet spot:

Then The Microphones placed in my ears sitting in the sweet spot:


Time domain Change of the right ear via waterfall plot:


Time domain of all four measurements via RT60:



That's about it.  Took just over 4,000 words.

Saturday, July 13, 2013

Headphone Frequency Response Repository

After getting what I wanted, I decided I better store some graphs somewhere safe and accessible.  Notice that most of these are definitely usable headphones, but they all have strengths and weaknesses.  I'll give these and some others reviews and graphs as I can.

German Maestro GMP160

Beyerdynamic Custom One Pro

Creative Aurvana Live!

Beyerdynamic DT235

Beyerdynamic DT1350

mad Dog version 3.2

Sennheiser HD598

Note 100 Ohm output impedance 
Sennheiser HD518

Shure SRH 840


Wednesday, June 26, 2013

Finally, the ultimate frequency curve for a neutral headphone!

AS stated in this AES paper from Harman: http://www.aes.org/e-lib/browse.cfm?elib=16768  the current target curves don't line up very well with what we hear from our stereo.  I have been trying with great pain to get sound equal to my stereo through headphones.  It has essentially been fruitless up until now.

I took a set of binaural mics from Sound Professionals, placed them in my ears, sat in the sweet spot of my calibrated home theater and took some measurements--lots of measurements.  My first day curve looked like this:

  Another round a few days later(RED):


 And yet another a few Days Later with Audyssey's Dynamic Volume in use(GREEN):

Things of note about These graphs: These are the average of both ears, below about 1000-2000Hz, the room is in total control, above there it's the head position.  You can see that little transition on the graph.  That just happens to be the wavelength of the width of the head(approx 2000Hz).  You shouldn't want to see any of those little wiggles below 2000 Hz and definitely not the 220Hz dip.

So what headphones did I have that measure like this on my head?

NONE.

I was able to get my grubby hands on a set of Beyerdynamic DT235 which sounded a little dark to me and I took and further modified my German Maestro GMP160 to more closely line up with my curve.  Then the Sennheiser HD598 which probably sounds the most correct to me. Here's what I got:






If you smoothed these out a bit:


I'll update this with more headphones and IEMs before long.

Tuesday, May 28, 2013

German Maestro GMP160 part 2

So I decided to modify the housing of the GMP160.  I liked my EQ mod, but it sure would be nice to be able to use these cans for everything without a high powered EQ.  You can see the into to this here.

After about a million mods and measurements, I ended up with this:
Here's my mod vs. the Mad Dog 3.2:
:)

But it's still not good enough!  I think that 8k region needs attenuating.  It just doesn't seem to track well with what I hear.  More work must be done.

Saturday, May 25, 2013

German Maestro GMP400

Loved these cans from the get go.  They have a fairly balance yet warm and revealing/spacious sound right out of the box and they are extremely comfortable.  When I first got the measurement rig working, fairly accurate, and repeatable, I put these up to see what was really going on.
 The frequency response is pretty uneven with 5 dB swings and one very deep notch around 1.8 kHz.  I really didn't want try to EQ this one.  It would require too many filters.  Anyway, I got fiddling with it today and changed every pad I could, turned it into the sealed version (or into a sealed version I suppose), changed the internal damping material, etc...  Eventually I was able to come up with something interesting.


Considerably smoother and consistent response!  IOW, this can now be EQed if I desire.  The best part about this is really the apparent size of the soundstage.  This is now the definition of envelopment!  The down side is an amp is mandatory, but fortunately I have one of those.  What I ended up doing is removing all the damping material out of the cup and adding 6 thin layers of 2"X2" gauze cut into circles.  I'll probably tweak it a little yet, but I am really pleased with the benefits.  Anyway, I'm sure I'll make an EQ setting for this, but the sound of it is fairly neutral now.

Friday, May 24, 2013

Beyerdynamic DT770M

This is my first measurement of these phones:

It disturbed me that the difference in the bass was so large--the left side has ample deep bass, the right side doesn't.  So I decided to do a little investigation.

First I took the headphones apart to measure the raw driver.  You can see I was unable to hold left side tight to the measurement rig b/c the wires are fastened pretty close to the housing and I have no desire to try to solder these again.
From this point forward, the red line will be the right, the left line will be in blue.  Anyway, the raw driver measurement doesn't show anything to be concerned about. Good news I thought.

Next I put the drivers in the housing without damping material just to see what would happen.
Eureka!  There's are bass problem.  So I was hoping it was just some problem with how the driver was seating in the cup.  I removed them both to add the damping material (plus an extra cotton ball), and sealed every potential air leak I could find hoping that the reseating would fix the problem.
Not exactly, but it did remove that 6kHz notch. :)

Ready to surrender for the day, I put the stock pads back on for another measurement to see how it might compare to the first measurement:

The extra cotton definitely changed the bass tuning a bit and changed the shape of the treble response.  I'm guessing the time domain would look a little better b/c of that.

Next I held them loose on the measurement rig to see what effects the seal has.
I contacted Beyerdynamic to see what they think and how to get it fixed.  Let me know if you have any suggestions.  I'm stumped.

Saturday, May 11, 2013

Jawbone Jambox

You see this little device reviewed on several sites around the web and it seems to get a lot of favorable impressions.  I had access to one for a few days and well, I had to see what this little thing could really do.  Let me just say that this is not a great sounding stereo.  It's not capable of the output anyone would reasonably want for great stereo.  That said, it's not horrible and can fit in your hand easily like a juicebox and puts out enough noise for near field listening.  It also has crosstalk cancellation in its circuitry that can be turned off and on by holding the + and - volume buttons down simultaneously for a few seconds.  That's a pretty cool feature!  The depth of field this juicebox can project is mighty provided you are fairly close to it(within a meter or so).  It unfortunately emits some electronic noise--which is a pretty common complaint it seems.  That's the biggest letdown of this device to me.

Putting it on a table, it sounds pretty weak in the low end, but certainly acceptable when on the floor.

Let's have a look at what the measurements say:
 This works out pretty well if you are reading on the floor or playing a video game.  The video games using binaural processing would be really cool.  The depth of sound field and envelopment is fun to say the least.

What if you city doesn't allow you to wear headphones while on your bicycle?  The awesome depth/envelopment made me question what this might sound like from my handlebars.  he he he....  Definitely too bright/thin, but with a little EQ, certainly acceptable if a little quiet overall:
Filters for Accudio look like this:
Filter 1:     20Hz   Gain -15dB  Bandwidth 1.47oct
Filter 2:     33Hz   Gain   -8dB  Bandwidth 1.00oct
Filter 3:     50Hz   Gain -12dB  Bandwidth 0.87oct
Filter 4: 1809Hz   Gain   -2dB  Bandwidth 0.24oct
Filter 5: 3522Hz   Gain   -4dB  Bandwidth 1.36oct

The three bass filter are there just to provide better power handling.  They really don't make any noticeable difference in the sound.