Superlux HD668B Review (headphone)

[L5730]

@abm0 Thank you for those links and your thoughts. Well, whilst I say comfort could be improved, it would seem I am one of the more lucky people who can tolerate these headphones in their stock form - over 4 hours listening last night and the only reason to take them off was because I went to bed. However the house is cool (central heating was off) and it's not Summer yet !!!

@solderdude, it's interesting how just changing the pads to velvet (velour) pads smooths things out a fair bit, reducing the 4k dip and also the ~6k peak. I appreciate your efforts in your reviews and am going to give the tissue paper mod a try - it's essentially free and easily reversible. Looks like you got a pair with very good channel matching!
When comparing HD681B vs HD668B, am I correct in interpreting your data to say that the HD681B is the sonically preferable (assuming EQ's to the same target) or has the 668B managed to shift the distortion that little bit higher to ~5k (coarseness difference)? Bass extension seems to be better on HD681, and less of a 4k dip and marginally louder/more efficient?
I suppose comparing the two, after testing, developing an EQ filter for each and then level matching would be a bit beyond reasonable expectation seeing how these things cost so little and there will be unit-unit variations that could wipe out the universal usefulness of an EQ filter if made too specific.

Strange that it seems the models made for other brands Samson/Presonus etc all seem to be 32 ohm models - HD681 variants? Rather than a 56 ohm HD668 variant. Could be a number of reasons for that, all of which could be nothing to do with the actual sound!

I suppose the take home point is that one can certainly tweak these cheap things for a decent base level benchmark of sound quality.

 

[solderdude]

I suppose, once EQ'ed to a similar target the only difference between HD681 and HD668B will be wearing comfort and amplifier load (32 and 65ohm).
The toilet paper mod also works in the same way for the HD681.

Without EQ the HD681 has deeper bass and more 'neutral' mids where the HD668B is a bit 'warmer/fuller' in the mids. Can't say who likes what tonal balance better though.

 

[FlanjeUK]

@FlanjeUK Thank you for your input and the AE link. They look awfully deep/full, but if they are squishy I guess that won't put additional pressure on the head/ears. How about the inner size, is it smaller than the original pads or is there more 'ear room'?
Ah, I think I see your review - you got the "cool and sweat" ones too.
Might be worth buying a coupe of different ones, I've a feeling we'll be grabbing another pair of Superlux headphones for the house.

I was going to take a picture to show the difference but I realised the inner ear hole is basically identical to the original, I never thought about that dimension as I have small ears lol

 

[L5730]

@solderdude
I just took the earpads off, removed the black sponge discs (observed which way 'round they went, different surface texture slightly) and cut some discs from 3-ply tissue paper. A dramatic improvement over stock without EQ, of course, which makes the treble acceptable, although dare I say it sounds a little woolly - likely only 2-ply is all that is required and I could just rip a layer off and try again - it's free to try!
Still needs a little lift ~ 3-4k for clarity, a passive filter of any kind won't fix that.

...
I made the toilet paper mod by Solderdude long ago after reading his great article about "taming the trebles" and since then i always enjoyed listening to these phones for the little money they cost. I recently tried the eq profile for the HD668B with velour pads (obviously after removing the toilet paper) and it sounds nice but in the end I prefer using it without eq with the paper mod since it's more simple and I don't have to apply negative preamp needed by the eq.
...

This. A quick and easy mod like the tissue paper one allows for easier connection to other devices without EQ and maybe with less output power, should one want to. This is a strong point in favour of that direction in my thinking.

It does make me wonder sometimes, with such easy and inexpensive mods with clear improvements why a company doesn't just manufacture something like that in the first place. Probably numerous factors and sourcing the right kind of material to baffle the driver only to find that source discontinue for something else could send product variance quite wide. Who knows, I am not nor ever been in manufacturing so can only guess at reasons.

 

[mc.god]

@solderdude
I just took the earpads off, removed the black sponge discs (observed which way 'round they went, different surface texture slightly) and cut some discs from 3-ply tissue paper. A dramatic improvement over stock without EQ, of course, which makes the treble acceptable, although dare I say it sounds a little woolly - likely only 2-ply is all that is required and I could just rip a layer off and try again - it's free to try!
Still needs a little lift ~ 3-4k for clarity, a passive filter of any kind won't fix that.

I agree, 2-ply is the optimal compromise for my liking, tried 3-ply and they became a bit muffled and lost spatial sensation, but it's all to one's personal preference.
And I admit, I'm too lazy too take off and on the pads every time so I ended applying the paper directly over the foam disc, don't know if some little wrinkle it makes can affect much the sound

 

[L5730]

Yep, 2-ply (or 1-ply if someone actually likes more treble/is older with hearing loss) does the trick. I guess the trade off is some 'speed' of sound with the tissue mod.
After messing about with EQ after the latest tissue paper mod, I've found the HF seems more smoothed so doesn't need any help as it sounds pretty smooth relatively speaking but it certainly helps having a boost just under 4k, quickly cutting afterwards. Pops vocals out of the recess they seem to be in.
Perhaps I should have gone for the HD681 as I have a slow 2.5dB drop ~100 Hz, with a 4dB boost @ 20Hz - kind of turning the lower end of things more into what the HD681 offers in more or less stock form. Haha.

I was searching for something to do with these headphones and stumbled open this thread. Apparently there is adjustment to allow the ear cups to further from the headband. I gave it a fairly strong pull and it wasn't moving for me (but then again it took me multiple attempts to seat a tight expansion card in an old Amiga1200AGA way back when). Has anyone actually got adjustment to work?
https://www.reddit.com/r/headphones/comments/imuyoa

 

[mc.god]

I was searching for something to do with these headphones and stumbled open this thread. Apparently there is adjustment to allow the ear cups to further from the headband. I gave it a fairly strong pull and it wasn't moving for me (but then again it took me multiple attempts to seat a tight expansion card in an old Amiga1200AGA way back when). Has anyone actually got adjustment to work?
https://www.reddit.com/r/headphones/comments/imuyoa

Can't be of help here, my Samson have the headbad from HD681 and is fully extensible and adjustable.
Amir too said that the 668 is not adjustable.

 

[solderdude]

Has anyone actually got adjustment to work?

It is 'self adjusting' and is what the 'wings' do.
• Comfortable, self-adjusting headband pads
The metal rods are clamped. They are not designed to slide.
All you can do is bend the metal wires of the wings a little.

 

[L5730]

@solderdude Thank you, it's fine, they fit my head out of the box - thankfully! I wondered just what on earth was being said on that reddit about sliding the plastic or the ear cup down - nope. I see two screws, but I have no desire to undo them.
Strangely the left head pad seems to be ever so slightly forward pointing so when I put these on it always catches the front most wire rod. Not a problem, I know it happens and expect it now. Starting to see more of the shortcoming of the low price point - but I'll bet that there are much pricier headphones that feel much worse even if fit and finish might be better.

 

[OnLyTNT]

It is 'self adjusting' and is what the 'wings' do.
• Comfortable, self-adjusting headband pads
The metal rods are clamped. They are not designed to slide.
All you can do is bend the metal wires of the wings a little.

Errrm, those wings on my 668B are sliding, a bit hard to slide thou and when you slide them you can feel they set in place.

 

[solderdude]

The wings can slide 'inwards' but not the metal rods of the headband.
When you adjust the wing position (more towards the middle of the head) it does not change the height much, only where the pads touch the head/hairs.
These metal rods also carry the signal to the right cup b.t.w.
I think the rods is what @L5730 was talking about.

 

[L5730]

@OnLyTNT Haha, I did mean what Solderdude said, the metal rods, as that would allow more circumference in general, however thank you for affirming that those little 'wings' do adjust. I tried when I got these and they wouldn't budge. I just tried and again and whaddayaknow they do pull out! I kinda pulled one quite a way out and then had a hard enough time getting it back in. Certainly not going to be an easy task to incrementally adjust them out.

This is what I come up with (foobar2000 Graphic Equalizer) after the 2-ply tissue paper mod.
Created in a different EQ program and 'cloned' by applying pink noise simultaneously through fb2k and ReaRoute and in the DAW with EQ, comparing live averaged spectrum of the two.

See attached .txt file. Rename and remove '.txt' false extension used for allowing attachment.

Also EqAPO (used foobar2000 with DirectSound and a virtual cable for EQ cloning).

Preamp: -4 dB
Filter: ON LSC Fc 30 Hz Gain 2 dB Q 1
Filter: ON PK Fc 77 Hz Gain -4 dB Q 0.5
Filter: ON LSC Fc 105 Hz Gain 2 dB Q 0.7
Filter: ON PK Fc 3500 Hz Gain 4 dB Q 1.9
Filter: ON PK Fc 4800 Hz Gain -1 dB Q 1.6
# Fix channel imbalance SuperluxHD668b
Channel: R
Preamp: -1.5 dB

Quite a relaxed sound now, without EQ (but with tissue) there is just a lack of vocal clarity and emphasis - the singer's feel like they've been mixed out. Also the bass bloom tend to muddy things and wallow. However, it's not a terrible sound without EQ (with tissue). I suppose each set will vary a bit so tweaks may be needed to get it just right. It's a shame the distortion is high right at or around the area where it's a bit lacking emphasis (~4 kHz). Oh well, these are cheap!

I should point out that without having any testing apparatus or having my hearing quality assured, what sounds like it works for me maybe useless to the next person even with the same unit of headphones. I am basing my deductions from the fantastic work done by folks like our host here and Solderdude, as well as what my ears tell me. Add in unit variations and there is only a limited merit to my personal EQ. But hey, we aren't looking for professional mastering grade repeatable accuracy, we're just enjoying the music!

 

[OnLyTNT]

Interestingly the plastic part holding both the rods and the wings also slides up and down and gives you the impression of adjusting the rods and helps nothing

 

[djigibao]

@OnLyTNT Haha, I did mean what Solderdude said, the metal rods, as that would allow more circumference in general, however thank you for affirming that those little 'wings' do adjust. I tried when I got these and they wouldn't budge. I just tried and again and whaddayaknow they do pull out! I kinda pulled one quite a way out and then had a hard enough time getting it back in. Certainly not going to be an easy task to incrementally adjust them out.

This is what I come up with (foobar2000 Graphic Equalizer) after the 2-ply tissue paper mod.
Created in a different EQ program and 'cloned' by applying pink noise simultaneously through fb2k and ReaRoute and in the DAW with EQ, comparing live averaged spectrum of the two.
View attachment 266573
See attached .txt file. Rename and remove '.txt' false extension used for allowing attachment.

Also EqAPO (used foobar2000 with DirectSound and a virtual cable for EQ cloning).
View attachment 266580

Preamp: -4 dB
Filter: ON LSC Fc 30 Hz Gain 2 dB Q 1
Filter: ON PK Fc 77 Hz Gain -4 dB Q 0.5
Filter: ON LSC Fc 105 Hz Gain 2 dB Q 0.7
Filter: ON PK Fc 3500 Hz Gain 4 dB Q 1.9
Filter: ON PK Fc 4800 Hz Gain -1 dB Q 1.6
# Fix channel imbalance SuperluxHD668b
Channel: R
Preamp: -1.5 dB

Quite a relaxed sound now, without EQ (but with tissue) there is just a lack of vocal clarity and emphasis - the singer's feel like they've been mixed out. Also the bass bloom tend to muddy things and wallow. However, it's not a terrible sound without EQ (with tissue). I suppose each set will vary a bit so tweaks may be needed to get it just right. It's a shame the distortion is high right at or around the area where it's a bit lacking emphasis (~4 kHz). Oh well, these are cheap!

I should point out that without having any testing apparatus or having my hearing quality assured, what sounds like it works for me maybe useless to the next person even with the same unit of headphones. I am basing my deductions from the fantastic work done by folks like our host here and Solderdude, as well as what my ears tell me. Add in unit variations and there is only a limited merit to my personal EQ. But hey, we aren't looking for professional mastering grade repeatable accuracy, we're just enjoying the music!

Why did you set R channel -1.5dB when in the test Amir put on the R channel +2.5dB?

 

[L5730]

@djigibao Haha, that is an offset for the left<>right channel imbalance in my set. Amir measured his and found his offset was even worse at 2.5 dB, whereas when Solderdude measured his set the channels matched quite well indeed. Jut the lottery of low price and lacking quality control.

The good news is that it is really easy to derive the L<>R offset (if any) yourself.
Just sum the channels of any music with a roughly central vocal to mono. Listen and the voice (and everything else) should sound exactly in the middle, not off to one side or the other.

You could get unlucky and find a rather large difference between the drivers across the frequency range, and so some frequencies maybe considerably imbalanced to others - which would be harder to fix, though not impossible.

@OnLyTNT That is quite interesting. My plastic bars don't move at the moment and I have little desire to force them. I did get both 'wings' out one 'click' and I think it's a slight improvement in comfort, well it couldn't get much worse, right?

My previous endeavours with EQ on the TakstarPro82 seemed to be quite forgiving of modern hyper compressed material. The recorded distortions were audible, but just not so bothersome. These Superlux HD668b (with tissue and EQ) don't tend to hide that grit so much (perhaps adding a little of their own), however they trade a better overall sound. Good recordings and dynamic material sounds quite pleasant.

 

[L5730]

A pair of HD681 (red) just arrived today - under £20 inc. shipping, would be rude not to try them against HD668b.
So this post is going slightly off topic.

There is a 0.5 dB channel imbalance, again louder in the right side (1.5dB for my HD668b pair). Easy to fix and most wouldn't notice unless looking for it. Much lower clamping force than HD668b and almost feels like these will slip off of my ears. Those metal conductors/headbands resonate like springs - going to need to dampen them on these HPs! (edit. a blu-tac sausage tying the two together at the top works like a champ. to deaden them).

Unlike the first impression of the HD668b, these do sound like treble cannons and less-than-great recordings make for a tiring experience.
They do have an immediate wow factor of making more atmospheric music feel like it's as wide as spread arms - Roxy Music's Avalon shines.
The sub-50Hz low end seems stronger than HD668b (might be because I have a expectation of that), but the warm 'cloud' of the HD668b is missing, resulting in a faster and tighter punchier sound. The HD668b bass cloud makes the overall sound more like our HiFi speakers - surprisingly like them in low-to-mid tonality.

The treble, although seemingly much more pronounced than the HD668b, does seem to sound more articulate, if for want of a better term.

2-ply tissue is not enough to make the treble soft enough - there is a lot of it!
Donald Fagen's The Nightfly, whilst we know it's sterile sounding is all a bit much ... those snare hits ...
The graphs from Oratory1990 reddit seem to agree with how I hear these - an upward tilt. A +3 dB Low shelf @ 250 Hz and -4 dB High shelf @ 4 kHz (with 2-ply tissue) helps.

Form a limited first impression, HD668b = HiFi 'warm' tonality / HD681 = unforgiving 'nearfield' monitor sound. Both require EQ / mods to deal with the treble though.
I guess the shortcoming is going to be the mid-through-treble quality, which only more refined headphones will deliver.

Would be interesting to measure these two pairs somehow, alas shipping costs would be amusing.

 

[markanini]

It might be an issue that the HD681 treble peak is at 5kHz while the HD668B is at 6Khz, that 1kHz difference does at lot IME.

 

[L5730]

Maybe, but there seems to be utterly tonnes more treble than the HD668b.
I've the same 2-ply tissue paper installed and I am still wanting to drop the HF by 4 dB - it really is that much!
The treble quality does seem to sound more refined than the 668b though, even if there way too much. Maybe something might change with a bit more playing in - doubtful but it has kind of been mentioned.

 

[OnLyTNT]

Form a limited first impression, HD668b = HiFi 'warm' tonality / HD681 = unforgiving 'nearfield' monitor sound. Both require EQ / mods to deal with the treble though.
I guess the shortcoming is going to be the mid-through-treble quality, which only more refined headphones will deliver.

I wonder, when they are EQed, is it worth to get HD681 over HD668b?

 

[solderdude]

Both have a similar treble peak level but notice how there is approx 3-5dB more lows/warmth which kind of 'masks' the treble peak a little.
EQ the HD668B to about the same levels below 2kHz and they are both piercing.

Notice how 20Hz is down -1dB compared to 1kHz and in Oratory measurement it is down -15dB.
explanation is here:

Seal breach. When they are removed from their awful packaging (shrink-wrap sealed carton) the pads are crushed locally and will not seal on the hard surface of a dummy head.
So... do not EQ bass based on Oratory measurements and fit some Superlux velvet pads (order them along with the headphones).
The pads on this measurement have been 'massaged' in the intended shape after which it seals fine.

FWIW I have re-measured the HD681 a few times over the years and never noticed any difference in the treble peak nor distortion.

When EQ-ing both to the same target I would say price, comfort (clamping force/headband) and replaceable cable or fixed cable should determine what one buys.