Sound Professionals SP-TFB-2 Binaural Microphone

This small binaural microphone sits inside the ear’s concha and can be used to measure headphone response on real human heads. The microphone only partially obscures the ear canal.

https://www.soundprofessionals.com/cgi-bin/gold/item/SP-TFB-2

Couple of notes regarding how to use this mic…

  • The mic is sold in regular and high sensitivity variants. I’m using the regular sensitivity one and it seems to work fine.
  • I tried running the mic through a cheap USB mic adapter and that didn’t work very well. The mic needs some plugin power (low voltage phantom current) and I think that adapter wasn’t giving it enough juice. I’m now running it into a Zoom H1N and that’s working much better, not least because the H1N has a preamp with adjustable gain.
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It’s too early for me to decide whether this thing is any good, but here’s some data, uncompensated with psychoacoustic smoothing applied.

A few observations:

  1. This makes the HD58X look warmer, slightly bassier and darker than the HE4XX, all of which agrees with my hearing.

  2. The HE4XX has noticeably more 8.5 KHz than the HD58X, which agrees with other measurements I’ve seen

  3. There’s no weird 4 Khz dip like on my MiniDSP E.A.R.S. :clap:

  4. You don’t see the boosted 1-5 KHz region that you see on HATS, I think because that’s mostly ear canal gain which doesn’t come into play here.

  5. There’s a big dip at 6700 KHz, which is the center point of concha gain. The mic sits in my concha, so it makes sense that I’m not benefiting from concha gain, but this is even worse because it’s dipped. Adding some EQ boost at 6700 KHz does (tentatively) seem to make stuff sound clearer/less grainy for me, so perhaps part of this feature is actually my own ear shape. I’ll have to do some more experimentation with my other ear and maybe my wife if she’ll play ball to see how much of this feature is me and how much of it is the mic.

  6. Both headphones look even more severely rolled off in the bass than what my E.A.R.S. and other people’s measurements show. I took these measurements wearing rather thick glasses and, unlike the E.A.R.S., I’ve got hair, so the roll off seems plausible.

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It looks like this thing might be useful for CSD waterfalls too. It shows that the HE4XX has some undamped resonances that the HD58X doesn’t, which agrees with measurements I’ve seen at https://diyaudioheaven.wordpress.com/.

HD58X

HE4XX

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From what you’ve posted, it looks like this is a very viable option for measurements. Especially for a hobbyist.

Thanks for posting.

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So, to get a better calibration, I measured the output from my room-corrected studio monitors (JBL LSR305 plus Rockville APM10b subwoofer) by measuring with the mic outside my ear and also in my ear, yielding the following:

It’s not quite optimal (lots of squiggles even after doing psychoacoustic smoothing), but it does show that there is a bit of ear gain in the 1-5 KHz region. Interestingly, it also shows that there’s some loss around 6-7 KHz, perhaps because of some interaction between my concha and the mic(?)

Turning the in-ear LSR305 measurement into a target curve, I’m able to EQ the HE4XX against this, yielding …

Comparing this to oratory1990’s professional measurements on a real HATS, we see various points of agreement.

  1. Sub-bass is rolled off (no surprise)
  2. Area around 1 KHz is a bit north of Harman neutral
  3. Area around 2 KHz is way south of neutral, though my measurements the gap centered around 500Hz higher than oratory’s
  4. Both show a big dip around 6 KHz, though mine is about 1 KHz higher than oratory’s
  5. Both show a peak around 8.5 KHz
  6. Both show a dip around 10 KHz

So far, I’d say this gets a lot closer to the big boy rigs than did my MiniDSP E.A.R.S. !

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That’s pretty spectacular given the price.

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