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Headphones sensitivity, impedance, required V/I/P, amplifier gain - Page 3

Quote:
Originally Posted by HalidePisces

I'm working on it.

Quote:
If you don't mind me asking, how was the gain calculated? It seems to be 104 - S@1V.

Yes. 110 dB is the target. The sensitivity is converted from manufacturer specs (often with 1 mW input) or taken from measurements and converted to 1V input. Since the source is assumed to output twice that (2 V), we have to subtract 6 dB.

You can also attack this from another angle: 110 - (X + 20*log10(2 / voltage_required_to_reach_X_dB)).

Quote:
Originally Posted by stv014

The gain calculation assumes a source output voltage of 2 Vrms. For lower voltage (portable) sources, obviously more gain is needed.

Right. If you use a DAP that outputs 1V you have to add 6 dB. If it outputs only 0.5 V add another 6 dB.

or add: 20*log10(2 / X) where X is the Vrms of your source.

Edited by xnor - 6/18/13 at 1:31pm

I've added the requested headphones and updated the numbers of some others.

Quote:
Originally Posted by HalidePisces

The impedance of the Bose QC15 is very high...

Yes, it's a noise canceling headphone with an integrated amplifier. It rises to about 15 kOhm at 100 Hz and drops to about 1 kOhm at 1.5 kHz.

Edited by xnor - 6/18/13 at 1:24pm

Integrated #13 into a graphic in #1. Not sure if dB SPL is the right unit. Is there such a thing as LU SPL? Would that even make sense?

Found the information for SHURE's SE535: http://www.shure.com/americas/products/earphones-headphones/se-models/se535-sound-isolating-earphones

Sensitivity: 119 dB SPL/mW

Freq. Range: 18Hz – 19kHz (Pretty much perfect)

I believe it's only 15 or 18kHz that most people can generally hear up to anyways, I forget, but this exceeds both of those expectations anyways. And 18Hz is very low, you're not going to be hearing under that.

Pretty amazing specs though for an earphone... I just wanted to look it up based on the information I seen in your table. :)

It's definitely one of the most sensitive/efficient in-ears. About 133 dB SPL theoretically with just 1V is crazy.

Edited by xnor - 6/29/13 at 3:53pm
Quote:
Originally Posted by AceInfinity

Freq. Range: 18Hz – 19kHz (Pretty much perfect)

High-frequency extension seems to depend a bit on seal, ear canal, etc., but just an FYI, that 19 kHz is (like with many many other sets) pretty optimistic, depending on your perspective.

Audibility for people aside, check the actual response. It's not like you're getting similar energy up top as you are through most of the range.

http://www.innerfidelity.com/images/ShureSE535.pdf

http://rinchoi.blogspot.com/2013/05/shure-se535.html

I have a pair of speakers in my basement that have a sensitivity of 105 dB @ 1W. The setup is also using an active crossover, and 3 different amps for each range of frequency. I was never an earbud or a headphones guy though, so this thread was interesting to see these numbers at least. :)

I'm getting a lot of mileage out of this collection of data. I link to it all the time when people ask questions about amp A with headphone B.

http://outpost.fr/audioconverter/

The converter values match xnor's measurements / calculations.
Edited by skamp - 7/18/13 at 3:46am

I couldn't believe the impedance of the QC15, but then I looked at the measurements over at innerfidelity.

That's one helluva impedance swing!

What the hell?

Is that some anomaly from the noise cancelling or something?

se

M4U2 and SL300 and Fanny Wang Custom 3000 have similar impedances. Yes, the integrated noise canceling / amplification circuitry results in a high impedance at low frequencies.

My guess/explanation: A crossover separates low frequencies, where cancellation works, from high frequencies. Low frequencies are amplified using the internal amp incorporating the inverted signal from the mics (to cancel outside noise), resulting in high impedance. High frequencies are "looped through" resulting in lower impedance (approaching that of the driver).

Makes sense. Thanks!

se

Quote:
Originally Posted by skamp

http://outpost.fr/audioconverter/

The converter values match xnor's measurements / calculations.

Nice tool!

Cheers

I should post in this thread since I keep losing it within my bookmarks and I always want to refer back to this. XD

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