Low impedance (Sundara) w/ high output impedance (Scarlett 2i2) - bad idea?

[spelte]

Looking at getting the Hifiman Sunduras which have an impedance of 32 ohms as I believe. The problem is my audio interface is a Scarlett 2i2 (4th generation) which has a high output impedance of around 50 ohms. Would this be a bad idea to pair with the Sunduras?

I got the Scarlett over the Motu M2 as it was a bit cheaper and has better preamps and features that are useful for when I play the electric guitar. Apparently, it also has a better DAC than the Motu because Focusrite decided to upgrade the underperforming DACs from the 3rd gen.

Would using the Scarlett which has a high output impedance not be a good idea to pair with the low impedance Sunduras? Should I return the 2i2 to get the Motu just for the lower output impedance and sacrifice the other benefits of the Scarlett? Or should I just spend the extra $100-200 for a dedicated dac/amp (not preferred, but I guess if it's the only choice, it'll have to do)

 

[staticV3]

Hi @spelte! Welcome to ASR.

In part due to the high output impedance and therefore high internal losses, the 2i2 4th Gen can drive the Sundara to "only" 105dB SPL Peak.

That means that the best case average SPL while playing fully mastered music will be about 80-90dB SPL.

Still loud, but perhaps not impressively loud.

On the bright side, the Sundara's flat impedance response means that the Scarlett's high output impedance will not affect the Sundara's tonality.

Btw, the Motu M2 has an issue when recording and using headphones, so perhaps not ideal: https://www.youtube.com/watch?t=2532&v=gMuA-2FbJxE

If you want an interface with an excellent headphone Amp built-in, then consider the Topping E2x2 or E2x2 OTG: https://topping.pro/

 

[spelte]

Hi @spelte! Welcome to ASR.

In part due to the high output impedance and therefore high internal losses, the 2i2 4th Gen can drive the Sundara to "only" 105dB SPL Peak.

That means that average SPL while playing fully mastered music will be about 80-90dB SPL.

Still loud, but perhaps not impressively loud.

On the bright side, the Sundara's flat impedance response means that the Scarlett's high output impedance will not affect the Sundara's tonality.

Btw, the Motu M2 has an issue when recording and using headphones, so perhaps not ideal: https://www.youtube.com/watch?t=2532&v=gMuA-2FbJxE

If you want an interface with an excellent headphone Amp built-in, then consider the Topping E2x2 or E2x2 OTG: https://topping.pro/

Since the Sundara's have a flat impedance response, it won't affect the tonality of the Sundara's at all? If so, that's great news!

As highlighted by Julian Krause in this video (

), it looks like "certain" lower impedance headphones get a huge shift in frequency responses. If the Sundaras are exempt from this, which headphones would be actually affected by the higher output impedance? I'm guessing IEMs would not be a good match with the 2i2

Regarding the MOTU M2, it looks like the Scarlett 2i2 is a better choice for me at this moment due to the ongoing problems with it, is that correct? For the Topping E2x2, I'm guessing it also has a low output impedance like the Motu M2 which would be better for driving low impedance headphones, but if the Scarlett's high output impedance doesn't affect the Sundaras specifically, would going for the Topping E2x2 actually be a worthy "upgrade"? I'm not eyeing on other headphones other than the Sundaras except for (potentially) the Sennheiser 600s or 6XXs which have a high impedance, which shouldn't be much of a problem for the 50ohm output impedance of the 2i2 as the Sennheisers are 300ohms.

My only real worry with the new Scarlett 2i2 is really with the high output impedance affecting the Sundaras, so if it doesn't, I'm hoping to keep it as these have some features (e.g. Auto Gain and Safe mode) which are pretty useful when using the guitar which I'm guessing the Topping interfaces lack. I'm willing to switch to the Topping E2x2 if it provides substantial upgrades in terms of audio quality over the 2i2, however. I'm not TOO worried about the volume if it is loud enough - I don't really listen to music deafeningly loud.

 

[normgr00]

Without doing the math I think the diffrence between 32 and 50 ohms is not much. I suspect you would need a diffrence on the order of magnitudes to ,matter (more than 10x).

I would not worry about this diffrence , but if you want to know what happens when there is a mis-match: The issue with impedance mis-matching is this. Think of both the current and the voltage going to the headphones, or speakers as sign waves. When the impedance of both are exactly the same, the sign wave for voltage, and current, are perfectly synchronized with each other. The sound created is not from the voltage, or the current, but from the power. Power = voltage x current. When the output impedance of the amp is different from the input impedance of the speaker then the current sine wave can lag behind or precede before the voltage sine wave. If power = current x voltage, and the impedances match, the high point of both the sign waves come together at the same time. Example: A current of 10 multiplied by a voltage of 10 = a power of 100. You can also think of this a a sign wave, a power sign wave that is of an amplitude of the two multiplied by eachother. When the two sign waves shift, and the maximum amplitudes do not line up, when the voltage is at 10, the current would not yet be at 10, so you would have 10 x 9 = power of 90. You just lost some of your power. The effect is frequency dependent so lower frequencies are less effected. The math is not complicated but I don't have time for that now. To do a proper calculation you would need not just the resistance on ohms but impedance which is expressed in ohms at a specific angle. Manufactures do not publish that, it must be measured. Some impedance differences for audio equipment can be 1000 ohms, but those differences are between inputs and outputs that are based on voltage, not power. These mismatches do not matter between components that are not power based. What I mean is that the output of a DAC (a voltage) goes into an amp input, and the amp bases it's job on input voltage, not power, so in that situation it matters little. Amp takes a voltage input and produces a power output, ~ amp input,- voltage based, amp output, - power based. But between an amp and speakers it matters because speakers and amp output are based on delivering power. To complicate matters, speaker impedance changes across the frequiency spectrum, and that is why speakers will never be perfict, and we can tweek speakers infinatelly with billions of diffrent results, a capitalists dream.

 

[staticV3]

The E2x2 can play more than twice as loud as the 2i2 4th Gen, using the Sundara.

+11.5dB, to be precise.

Also, while the Scarlett's output impedance won't affect the Sundara's steady-state response, it is said that low damping factor can cause time-domain issues like low bass decay (though I haven't personally seen measurements thereof).

 

[spelte]

Appreciate the responses!

Seems like the only problem now is low bass decay (not exactly sure what that is) but it seems like it isn't as big of a problem as it initially seemed to me.

 

[staticV3]

Seems like the only problem now is low bass decay (not exactly sure what that is) but it seems like it isn't as big of a problem as it initially seemed to me.

See "Damping Factor: Effects On System Response" by Dick Pierce.

In it, he concludes a damping factor of 10 to be completely sufficient, with even 5 being technically good enough.

For reference, the E2x2 would give you a damping factor of 38 while the 2i2 gives you 0.8 damping factor.

 

[spelte]

Looks like the E2x2 is a far better choice if my main concern is the headphones' performance. Took a quick look at the Topping interfaces, and it seems that it doesn't have many of the features that are useful for me outside of the headphone department. I guess the only way to truly find out is to buy the Sundaras and try them out myself with the 2i2.

 

[xophere]

I mean I assume you are enjoying this analysis but there are several $100 amps that will easily resolve any questions here and support any can or iem you could throw at them. Maybe it would be better to be done with it?

 

[spelte]

I mean I assume you are enjoying this analysis but there are several $100 amps that will easily resolve any questions here and support any can or iem you could throw at them. Maybe it would be better to be done with it?

For sure, but I was really just wondering if the Scarlett 2i2 that I had just bought for other purposes could drive some nice headphones too. My biggest concern with the high output impedance of the 2i2 was really audio quality and accuracy, so if there proved to be no discernable difference in tonality of low impedance headphones with this interface, I just found buying another piece of equipment, even on the more budget-friendly side to be a waste of money. As I said earlier, I don't listen to music all that loudly, so if buying a dedicated headphone amp only provides louder sound, and only louder sound, it would be useless in my case.

I think in the future, if I do become invested into the audiophile headphone space, I could buy a nice dedicated amp, but I'm really just planning on using this setup for light mixing purposes and some casual music listening on the side, so I didn't really want to spend another $100-200 on something I wouldn't get much benefit from.

 

[xophere]

I did really like the moto M2 I had but was frustrated it didn't work well with Linux.