Hi, For the last few days I have been struggling with how good and how poor headphones sound. I have been listening to a variety of music with a small variety of headphones with MSRP of (approx) less than $180. Specifically (in alphabetical order), I have been listening to . . . JVC HA-RX700 Senal Sound SMH-500 Sennheiser HD 558 Superlux HD668B Superlux HD681 According to their respective manufacturers, these cans include the following specs (copied from respective website, packaging or box) . . . JVC HA-RX700 . . . . . . . . . Sensitivity 105dB/1mW . . . . . . . . . . . . . . . . Impedance 48 ohms Senal Sound SMH-500 . . . . Sensitivity 101 dB +/- 3 dB (@ 1 kHz/mW) . . . . Impedance 58 ohms @ 1 kHz Sennheiser HD 558 . . . . . . SPL 112 dB (1 kHz/1 Vrms) . . . . . . . . . . . . . . Impedance 50 ohms UPDATING initial posting of Sennheiser HD 558 specs to also read . . . Sennheiser HD 558 . . . . . . SPL 99 dB (1 kHz/1mW) . . . . . . . . . . . . . . Impedance 50 ohms Superlux HD668B . . . . . . . Sensitivity 98dB (SPL/1mW) . . . . . . . . . . . . . Impedance 56 ohms Superlux HD681 . . . . . . . . Sensitivity 98dB SPL/mW . . . . . . . . . . . . . . . Impedance 32 ohms While I understand these (and other) manufacturers manipulate Sensitivity or SPL ratings to enhance product marketing, I do not understand how to quantify the differing units. For example, while I understand dB/1mW represents decibels per one milliwatt, I do not understand how "dB/1mW" compares to "1 kHz/1 Vrms" or "1 kHz/mW" or "dB/mW." I have read many threads regarding an industry standard for Sensitivity and other specifications. I have also read volumes of reviews at this website and other websites whom claim to test headphones (using a variety of components) and present Frequency Response graphs or curves. Unfortunately, similar to the manufacturers, these websites do not use identical components to test the headphones they choose, and their Frequency Response graphs are often (if not always) different, and the units associated with the Frequency Response graphs vertical axis differ as well (e.g. Amplitude (dB), Amplitude (dBr), Relative Response in dB, dB V/V (smoothed 1/3 oct), etc). I may be wrong, but I believe dBr means dB Relative or Relative dB . . . and if so, they ARE the same. But then there's dB V/V . . . where the vertical axis range is -50.0 to 0.0 incremented at 5.0 through this range. I have no idea how to relate dBr to V/V . . . particularly when dBr graphs vertical axis has a midpoint of zero, 0, and then positive dB above, with negative dB below - a majority of the graphs I found use this standard. Ideally, for my analysis, I would love a single website that has Frequency Response graphs (or curves) for each of the above headphones, but that is not the case. If it were, then I would assume any idiosyncrasies would be consistent throughout the testing and that, relatively speaking, any errors would be consistent from one manufacturer to the next - but I've probably said too much there. For my analysis, what I have done thus far is measure the amplitudes associated with 30, 60, 120, 250, 500, 1K, 2K, 4K, 8K and 16K Hz. Next, for each FR graph using the respective amplitudes (ignoring the dBr or V/V units), I normalized all frequencies to 1K Hz . . . meaning, I zeroed 1K and then added or subtracted the differences between it and the other frequencies. Using photoshop software, given the graphs available (online and or from the manufacturer) I believe my measurements are very accurate and consistent within logarithmic scales. Using a DAC amplifier with digital graphic equalizer (with dB fine tuning to more than 0.1 dB per frequency) and an MP3 player with digital graphic equalizer (with dB fine tuning to 0.1 dB per frequency), I conducted my tests. Conducting my listening tests, I chose the Senal SMH-500 as my benchmark - both for listening and quantifying amplitudes across the frequencies noted above. Next, I documented the graphic equalizer (G.E.) dB setting for each frequency noted above. Then, for each frequency, I added the G.E. dB to the "Relative Response in dB" values obtained measuring the dB amplitudes (described above). The resulting (addition) dB value, per frequency, was then used as a baseline for each of the other headphone manufacturers (noted above). For example . . . at 2K, using the SMH-500 graph, I measured an amplitude of approx 115.62 dB and 110.00 at 1K . . . normalizing to zero, I used an amplitude of 5.62 dB for 2K . . . and at 2K the G.E. setting was 3.30 dB . . . 5.62 plus 3.30 yields 8.92 dB for 2K. Using 8.92 dB for 2K as a baseline, and the measurements for each of the headphones (noted above), I adjusted the G.E. settings to compensate for higher or lower amplitudes obtained from the respective manufacturers FR graphs. For example, at 2K, using the HD668B graph, I measured an amplitude of approx -0.15 dB, and after normalizing 1K to zero, the resulting amplitude measured appox 2.08 dB at 2K. Using the SMH-500 benchmark value of 8.92 dB for 2K, I set the G.E. at 6.84 dB for HD668B. This same approach was implemented across each of the frequencies noted above. In essence, regardless of impedance (which primarily effected volume levels), I wanted to ensure each headphone was producing the same approx SPL at each of the frequencies noted above. While my methods may be exceedingly elementary, and perphaps unscientific, I must say the results have been stunning and surprising. In short, I am astounded by how similar these cans sound when their output dB's are supplemented (as described above) using a G.E. I should add that the audio quality does vary when compared to the Senal cans . . . JVC and Superlux - very little, Sennheiser - not terribly significant (no surprise given the MSRP is nearly 3X the other cans). For me, in this instance, quality of sound represents how my ears perceive each note or how a chord runs in or bleeds out, along with clarity and smoothness, and where subtle notes or riffs can be heard with one pair of cans, but not the other(s). For critical listening, audio quality is very important to me. But for day to day listening, I have to say I am astonished by how G.E. settings manage to create such similarity between each set of cans. My tests included FLAC and 320 kbps CBC rips of a variety of artists I enjoy listening to and tracks I know well. I know there are other specifications to quantify, but at this time I am happy with what I have achieved thus far. That said, I would like to get a better understanding of how to correctly quantify the units "dB/1mW" an "1 kHz/1 Vrms" and "1 kHz/mW." Has anyone here quantified frequency response curves in the manner I described, implemented and tested? Thanks in advance for your comments. CurlySue P.S. For those interest in the FR graphs I used, below you will find links for three of them: Senal SMH-500 . . . http://i60.tinypic.com/2a7dgsz.jpg Sennheiser HD 558 . . . http://i62.tinypic.com/34doqiq.jpg Superlux HD668B . . . http://i61.tinypic.com/2r70ig6.jpg P.S.S. How cool is this - I just received an email from my boss where he has been corresponding with Sennheiser regarding their specifications . . . Good Morning NAME REMOVED, Thank you for contacting Sennheiser Technical Support. My German colleagues said that it was one hundred (100) mW. NOTE: These headphones are 50 Ohm headphones and hence designed to work off a much less powerful audio signal. These models were specifically designed for use with less powerful audio devices (like portable devices) and portable inline amps. If you are looking for something that will handle a strong signal then you should consider the HD 650 which are 300 Ohms and will handle 500 mW max nominal continuous input power. Have a great day. NAME REMOVED . . . and the 50 Ohm headphones referenced in the above email are Sennheiser HD 558 - which apparently are good to only 100 mW. After learning from MindsMirror (noted below) THAT makes me want to re-evaluate my interest for Sennheiser HD 558 cans. 100mW? Really?!?! WOW . . . that has got to be an industry low for entry level audiophile cans . . . 100mW . . . they MUST be joking.