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GoTo measurements of Beyerdynamic headphones

Beyerdynamic: DT150 (250Ω)
Beyerdynamic: DT250 (250Ω)
Beyerdynamic: DT770 Pro (250Ω)
Beyerdynamic: DT990 Pro (250Ω)
Beyerdynamic: DT990 (600Ω)
Beyerdynamic: DT1350
Beyerdynamic: T50P

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  1. mkrzych says:

    Nice article and measurements. How do you perceive Beyers T90 in case of the characteristics? What kind of amp would be kind of perfect match for them?

    • Solderdude says:

      Well I haven’t measured one, just briefly heard one a while ago.
      I thought they were somewhat ‘better’ in the bass and mids as the DT990 (its cousin).
      I found it too ‘peaky’ in the treble, even more so than DT990 whcih I find slightly ‘smoother’ in the treble.
      There is no amplifier that can undo the peak BUT it could be lowered with acoustic damping.
      As the T90 is 250 Ohm and has a reasonable efficiency an amplifier that has a decent voltage swing (so not the average phone) should be enough.
      Should you want a bit more warmth then an amplifier with a high (between 100 and 300 Ohm) output resistance could add 2 dB’s more lows which relatively will lower the mids and treble peak.

      • Solderdude says:

        Another option to lower the treble peak is by making the T90 filter which lowers the treble peak ONLY to more ‘realsitic’ levels, dampening felt is not as ‘precise’.
        Below the link to the filter circuit.

        • mkrzych says:

          This T90 filter is quite nice idea. I have a DAC with the headphone section based on OPAMP and know that some caps could be changed and they don’t increase or lower the bass. They adjust the damping of the lower frequency to suit different headphone drivers
          design. There is no specific value, but 15nF to 47nF covers the range.
          33nF is for flat damping. This I suppose is cap and resistor in series in the opamp feedback gain. So changing them could be also an option, but I don’t have exact schematic and can only rely on PCB paths.

          • Solderdude says:

            Adding a resistor + capacitor in the feedback path will certainly lower the treble levels.
            The values will depend on the feedback resistance in the path, attenuation you want and from which frequency. Also it is only 6dB per octave so only good for headphones that need shelving.
            In the case of T90 this isn’t problematic and may work quite well.
            It may not be the best idea if that amp is used with other headphones as well though unless you can switch it off easily again.
            Changing the FR (quickly) to more accurately suit a headphones characteristics is what the Kameleon is all about.

            • mkrzych says:

              What you exactly mean by “headphones that need shelving”? Yes, the problem that with this amp I also use different cans. I have recently also discovered that in my Marantz amp the headphone out is just straight from the discrete amp section going to the HP jack via the 2W resistor and it sound pretty damn good, is it possible?

              • Solderdude says:

                Shelving is a word used in studio and EQ and means a drop (or increase) of the frequency response below (for a low shelve) or above (for a high shelve) a certain frequency.
                Usually with a fixed amount of gain.

                Speakers amplifiers with a headphone out (especially the older units) simply created a HP out by connecting the speaker output of the amplifier circuit via a (relatively) high resistor value.
                The output R of these HP outs can vary between 100 Ohm and 600Ohm.
                The effect this has depends on the impedance plot of the headphone.
                In case of the T90 the impedance rise around 100Hz is substantial meaning that, by means of voltage division, the headphone receives a not-flat frequency response that may reach +4 to +5 dB of bass increase and +1 dB of upper treble.
                Of course this depends on the output resistance of the headphone out.
                The higher this is, the greater the change (for some headphones).
                It is my experience that this ‘euphonic’ change (increased bass and slight upper treble) usually works out for the better for most Beyer headphones.

                • mkrzych says:

                  In my case it’s Marantz PM6004 with 330 Ohm 2W resistor in serie to the headphone output jack. Consulted in the service manual.

                  • Solderdude says:

                    That will give a + 3.3dB boost around 100Hz (where the bass usually resides)
                    At 50Hz and 300Hz the boost is around +1.5dB.
                    This is audible as a ‘warming up’ and having slightly more ‘body/weight’ to the sound.
                    It becomes a tad more U shaped.
                    No boost in the upper treble to speak of because there is less inductance due to Tesla ‘tech’ (less windings = less inductance = less treble lift for higher output R amplifiers)

                    • mkrzych says:

                      Man, you’re very good at that! Indeed, Marantz out is slightly warm sounding with good body/weight added to the sound than my DAC out, but in the same time is rather mellowed, condensed with not so wide soundstage and little lack of sub-bass.

                      Hard to say what could be the best and easier to do? U shaped FR I have read somewhere could be quite good, but could also take some “air” from the music perceived as less treble.

                      I am thinking if LP G109 connected to the recorder out of my Marantz will bring any difference without any modifications to the T90.

  2. mkrzych says:

    BTW, do you think that dedicated amp like Lake People G109 could be the best option for T90’s to sound neutral as possible?

    • Solderdude says:

      With the peak adressed (filter or felt modifications) the V109 will deliver the goods IMO.
      The Marantz will be somewhat more ‘mellow’ and ‘full bodied’ sounding but less neutral.

      What could be interesting is that it would appear as though the left HP out could easily be modified to a higher output R (say 120 Ohm) by cutting 2 traces and adding 2 resistors.
      Given the max output voltage of these amps you could even go higher in output R to 330 Ohm if so desired.

  3. mkrzych says:

    I have found finally the spot with my DAC modifying the opamp feedback loop with 22nF/25K in series leaf and 15K gain resistor in parallel to the series leaf (as I could read from the PCB paths). It’s now kind of sweat spot, where the bass has an impact and body not loosing the control and lowering a bit the top end. It gives the very neutral sound as I hear it now. Need some more time however.

    • Solderdude says:

      This basically creates a +3.5dB bass boost between 10Hz and 100Hz and is ‘flat’ again from 1kHz up.

      • mkrzych says:

        Is it bad thing in your opinion? I have found that dedicated A20 amp has 120 Ohm output resistance which may tame the treble and that’s why people are saying that’s one of the best match for T90’s. I can still hear the brightness on some records (old ones) time to time, but it’s kind of sweat spot (almost 😉 found. Now to change the pot in my DAC for plastic conductive from Vishay – hoping it will improve channel balance and eliminate scratchy sound on the el’cheap one soldered now. BTW, what do you think about LMH6672?

        • Solderdude says:

          the treble peak isn’t addressed though, just masked because of the bass boost. Bass boost isn’t the same as 120 Ohm output does, I think the boost is preferred when you like the sound.
          The LMH6672 is intended for a 50 Ohm line driver for digital signals.
          It can be used for audio though but the very high slewrate might be problematic with some PCB layouts/applications and possibly show ringing/oscillation.

          This can happen when this opamp is used in signal follower mode (unity gain) so for me it isn’t a recommended 1 to 1 replacement for lots of opamps.
          I do like the current capabilities for things like C’Moy type amplifiers.

          • mkrzych says:

            Could it be perceived and audible as shimmering of the driver somehow? I know that for the implementation of my DAC headphone section 33nF is considered to be ‘flat” – stock response, so I guess soldering 25nF will lower the treble peak a bit and adding in the same time slight boost in the bass region, guessing preferable for open back cans.

            • Solderdude says:

              I think the shimmering is a T90 treble resonance problem.
              I don’t know where the capacitances are in the circuit and what functions they have.

  4. mkrzych says:

    BTW, the opamp in my DAC is LMH6672. Quite unusual I guess.

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