I need advice on what set of headphones will work best as a mobile practice rig using the Phil Jones BigHead Pro HA-2 headphone amp (300 mW, impedance 16-64 ohms).
I set out to replace my aging Vox Amplug Bass and found what I thought were second hand gems in the portable practice rig market.
- Phil Jones HA-2 Bighead Pro - €170 shipped
- AKG K702 (62ohm) - €60 shipped
My verdict is that this combo is severely underwhelming.
I assume there's the possibility of a mismatch with the K702, since the specs for the BigHead are lacking.
For starters, the K702 aren't exactly what I'd consider "portable" given they're open back headphones. Even if you're not using them outside with a very obviously high noise floor, just not using them at home is enough either. Take my HD600 as an example - the bass levels sound completely different at 7pm with the windows open vs 10pm with the windows closed.
The relaxed fit doesn't always help either, more so if they're used. Clamp force affects how far the drivers are from your ears as well as compressing the pads (or not) thereby potentially increasing their density and not allowing the sound being produced by the drivers to dissipate too easily. It's sort of like having the windows open or not in a car - it's not just the ambient noise and what the listener hears, in bass race competitions closed windows is the standard for when they put a mic inside to measure the output vs when the same cars are just showing off at the parking lot and they may have them open since some of the people that they're being shown off to don't exactly have their own dB meter (and can look at other indicators first, which may even be the chassis more than the subwoofer output, like flexing steel panels on the cars).
I wear my HD600 with about the same adjustment on it (including bending the steel frame) to mimic having broken in an AKG self-adjusting headband on my own head and the bass is sufficient for me...but then here's another problem: what if that used AKG either self-adjusted to a guy with a bigger head/has a thicker 'fro or something or he loosened it up on a stack of books to fit his skull or his hairdo. And then decided the bass was too weak then and sold it for a bargain.
Easy way to test if this might be the problem in your case: press the earcups harder against your head (you'd have to listen to recorded music instead of your bass guitar though). If the bass improves, then maybe clamping it by setting it between two stacks of books and then pushing one against it might make it tighter over time. You can't over do this with that method or by hand though since plastic can snap, unlike the steel frame on Sennheisers.
The AKG have less punch than the Sennheiser HD280 pro they replaced
The K702 are 93dB/1mW sensitivity, the HD280 Pro are 113dB/1V...which given it's 64ohms is roughly 103dB/1mW. For the same amount of power, the HD280 Pro will be 10dB louder. That doesn't just affect the overall volume, it will affect how well you can hear "punch" in music.
Think of it like a Toyota Corolla weighing ~3000lbs and a Lotus Elise weighing ~1200lbs using the same engine (as in literally, Lotus uses Toyota engines) and then you punch the accelerator to overtake in either. The British sports car chassis will feel faster than the Japanese sedan chassis. Similarly, you'll pull more G's in corners (ie you go faster in corners) and finish a lap faster in the Lotus.
Even the power rating on the PBJ isn't very clear. It just says,
| Power Output | 300mW/ channel, Headphone Impedance: 16-64 OHMS |
|---|
I'm not saying they're definitely lying and I'm absolutely sure, but it sounds like plausible deniability if they get actually get asked about the actual power at a given impedance. See, power changes depending on current and voltage, and the output can change depending on the load impedance. For example, here's how Schiit rates my Asgard3:
Maximum Power, 16 ohms: 5W RMS per channel
Maximum Power, 32 ohms: 3.5W RMS per channel
Maximum Power, 50 ohms: 2.5W RMS per channel
Maximum Power, 300 ohms: 600mW RMS per channel
Maximum Power, 600 ohms: 300mW RMS per channel
I mean you don't have to phrase it exactly like this, but you still have to note at what impedance it delivers that power and make it clear that that's what you mean, not state the output then just list a load impedance range because for all I know those specs can mean it can deliver "300mW per channel into 16ohms, 150mW into 32ohms, 75ohms into 64ohms, so don't use any impedance above that because it will suck; and uh, don't use any impedance lower than 16ohms either... (because power vs distortion ratio gets way worse)."
Note that you can absolutely design a circuit that can deliver the same amount of power into a relatively wide range (ie up to 4X the low range, 16x4=64), kind of like how some car audio amps deliver the same power into 4ohms to 8ohms or 2ohms to 8ohms, but that's not a better guess at what exactly those stated specs mean.
...although what they lack in bass presence is made up for in a natural and wide sound (vs. the boxy Sennheisers.)
Well that's really the selling point of the AKGs. Although with my Meier Cantate.2 there really isn't a night and day difference between the K701 and more so the K702 vs the HD600.
I would have picked the K70x normally but apart from a used HD600 popping up for a good price...
The PBJ headphone amp is less loud and does an outright poor job of amplifying a bass. The literal example of "you only had one job"...
...since I got the HD600 at a time when I didn't know I could score a Meier Cantate.2 (that I sent back to our other home in another country so I'm currently using a comparable peformance Asgard3), 300ohms was safer than relatively finicky 62ohms because lower impedance loads can have a problem with a high output impedance amp output stage. For reference, my Asgard3 is under 1ohm, my Cantate.2 is under 5ohms, and my NAD 304 integrated amp's headphone output is around 138ohms and my old Little Dot MkII is around 120ohms. The latter two make the K701 sound like tin cans.
Now I can't be sure if there's an impedance mismatch, but if they didn't publish what the output impedance is and you have this problem, then it's probably too high for that AKG. It's probably too high for the HD280 Pro too but impedance mismatches like this can go either way. For example, the Little Dot MkII made my Grado SR225 sound like a mudslide (it still sounds like a total tin can on the NAD though).
...I needed full Vol and full Gain plus 75% and 75% treble to get a decent sound that keeps up with a backing track (Indie pop, rock, prog rock, disco songs).
Plus the HD280 Pro had one thing going for it: much higher sensitivity. Even if it does deliver 300mW into a 62ohm load you're basically squeezing the amp like flooring it on a Corolla to overtake before you have a head-on collision. I mean, sure, it can still violate freeway speed limits, but the acceleration isn't exactly like when the same engine is in a Lotus chassis; or when you're in a twin-turbo V8 Audi.
By today's standards, you can look at the AKG two ways. Its sensitivity is high if you compare it to some older headphones as well as some current or not too long ago phased out planars, plus the availability of amps that can deliver 512mW+++ into a 62ohm load; however its sensitivity is kind of low once you start considering how Grados have 99dB/1mW, most IEMs are over 100dB/1mW and some are waaaaaay past that, or driving it with something that has to run off a battery. That said...
It struggles, and does so at a high price tag.
...
IF it actually delivers 300mW into that wide an impedance range and your problem turns out to be more of the loose fit than the impedance, the price you paid for wasn't bad. I'd probably use it too...just not with the AKG still. Maybe more of like the OG HE400se since that one had a 98dB/1mW sensitivity and 24ohm impedance. And that assumes its input sensitivity works with a guitar pick up's output that hasn't gone through a preamp because, yeah, this is another variable. Although I'm going to assume it was probably made for that, but then again, some pick ups aren't all the same (kind of like how some tubes have higher gain, so that affects the sound on an amp or preamp, whether for home use or for a guitar).
It struggles, and does so at a high price tag.
I tested the setup with a variety of basses: MIM P with G&L MFD, US Std. P, Lakland 55AJ, and Lakland DJ4.
What I would have liked to have, is similar volume and presence as the Rolls PM351 in a wall-wart-free package, but I have been undone by my ignorance of reading spec sheets and maybe having unrealistic expectations.
I have read that the HA-1 had issues driving headphones, and I get the sense the Ha-2 suffers the same shortcomings. After much research I landed on the AKG K702, but a tiny bit more research illumined their 'current hungry nature' and a need to have an amp despite the low Ohmage.
Needless to say I am frustrated, as I have a big production to prepare for and this duo is an expensive lateral step to my previous setup, plus the time waste of research + buying is an exacerbating fact.
Have others had similar issues? Can this be solved with another pair of headphones?
I need to have the ability to practice away from a power source, so anything wired will not work.
Like I said there might be other things going on, but even if a lot of it is due to the looser fit on the K702, if you've got a production to prepare for, you may not have time to bend the plastic back or even to get a replacement from AKG and then install it considering the time it takes for them to get it to you (which isn't exactly Amazon).
I'd probably just get a different headphone. Maybe closed back, like the DT770 32ohm. Problem is at 32ohms if the output impedance on that amp is a bit high you still have a problem, not to mention even the DT770 (96dB/1mW at 1000hz) one has markedly lower sensitivity compared to your HD280 Pro.
Alternately, there's the Superlux HD660. It's only rated for 93dB/1mW,
but that's at 1000hz. It's waaaaaaay louder in the lower frequencies. One downside: it's 150ohms. But hey, it's $60. Might be worth a shot.
