Comparing iPhone and Rotary sound quality

[tallguy58]

Here's a vid I found on You Tube. Kind of hokey, but he tried.

https://www.youtube.com/watch?v=0IEPWIESE34

Here are a few links to older Bell Telephone films for some of the newer members:

How to Dial a Phone:  https://www.youtube.com/watch?v=PuYPOC-gCGA

Dialing Tips:   https://www.youtube.com/watch?v=APcODrfhcVQ

The Town and the Telephone:  https://www.youtube.com/watch?v=Q7N8vqyO7pc

[Slal]

Fun watching the old 'shorts' or news reels.  Liked the giant dial she used to demonstrate...

As for You-tube comparison-- realize it's just a fun exercise, but would've been better if he'd used a recording & same levels (say 0 Db) otherwise you can't really match them & see.

Sine wave or 'scope' view didn't have a *scale* either which would be nice. ; )

Still, Hi-Fi geek that I am, did some screenshots & popped them into photoshop.

Touch tone (WE 2500?) have a greater frequency range?  Looking at blue peaks & valleys -- looks to have highest 'treble.'

I-Phone's wave looked a little more narrow. Maybe it filters out some of that treble that people might find annoying.  Think the guy mentioned something about it sounding better.

At home, funny thing is-- have gone from one cordless that warbles to 5 rotaries that sound like I'm in a clock shop at noon.  Now the 'warble' seems out of place & find self reaching for cell.  ; )

Anyway thanks for posting.

--Bruce     

[Phonesrfun]

The iphone may have a better overall frequency response and better reproduction characteristics than a 500/2500 due to the later technology microphone employed.  The 500/2500 has a carbon microphone (T1), and carbon mics are lousy at high fidelity reproduction.  The problem with cell phones is really the whole transport system of digitizing the signal, augmented by the standard problems of sending/receiving a signal wirelessly.

For telephone work, the fidelity is not really of high importance.  The frequency response of the carbon T1 mic is nominally 300 to 3000 Hz, and fairly flat.  Old Bell system publications such as the Bell System Technical Journal have that information published.  The T1 was designed in the 1948 to 1949 timeframe just for the introduction of the 500, so it's withstood the test of time.   A carbon mic usually sounds real good, and we don't really hear the "fuzzy" distortion that a carbon mic creates when we are talking on the phone. 

But try to patch that same signal from a phone with a carbon mic into a PA system or over the air on a radio, and the carbon mic's fuzzy characteristics really start to come through.

So, on frequency response and fidelity, a phone with a carbon mic will lose every time.  When it comes to reliability and understandability, the 500/2500 will shine every time.

The 500 and 2500 use identical voice components and have identical characteristics as each other.  (Subject to the quality of the individual T1 microphone.  There can be vast differences in mic quality this far out from the original manufacture dates).

Interesting graph.

[Scotophor]

Slal, is your screenshot supposed to be both phones reproducing the same sound? It seems to me that the blue and red lines start out very similar but quickly diverge, as if there was some kind of speed issue in the neighborhood of 10% difference between the displayed signals. Stretching the red wave until it more closely matches the blue one at the right side of the screen would provide a more meaningful comparison.

[Slal]

Hi Bill.  Interesting about the characteristics of the T1 mic.  Wonder where I'd find a comparison (if there is one) between T1, F1 & N1?  So many technical articles... They are called 'BSP's?  Wouldn't know where to start!

Scot, you're correct of course.  Sine wave comparison meaningless except to get rough idea of peaks & valleys.  Guess if you *really* wanted to compare them, have to calibrate deck with ref. sig-- lets say 440Hz @ 0-- and set deck's record levels at zero or a little less to allow for "head room."

Then, you'd need a *recorded* sound clip at a set 'gain' or volume.  Otherwise you can't control for changes in the guy's speech.  "How are you today?"  Would look one way of course.  "HOW ARE YOU TODAY!"  Would be quite another!  As said, it was just a fun exercise-- too many variables were left out (imho.)

But back to "How to" clips, this one goes back even further & might be fun.   Music sounds so *serious* though. : )

http://www.youtube.com/watch?v=naQ9EMJEv0U&feature=youtu.be 

Anyway thanks for replies & enjoy week everyone

--Bruce