Posts Tagged 'headphones'

Impedance, Hi-Fi, Headphones and Guitars

Impedance is an important part of audio technology, all the way from plugging your guitar into your amp, your amp into your cab, the cabinet microphone into the preamp and all the downstream connections, both digital and analogue, right the way to your listening experience, from speakers to plugging headphones into your mp3 player. However, how much do we know as producers and music listeners, and how much do we need to?

In all actuality, most of us don’t really need to know that much about it, previous generations of telecom, audio and electrical engineers have addressed a lot of the issues for us and, generally, if we plug something into something else, everything has been designed so that it will just work. There may, however, be a couple of things you may want to consider…

What is impedance?

For those of an electrical persuasion, impedance (Z) represents the total resistance of a particular circuit including, not just the resistors, but also the resistive contributions of other components such as capacitors and inductors. Like resistance, it is measured in Ohms. Voltage (V), current (I) and resistance (R) are related following Ohm’s law: V=IR; power (P) is the product of the voltage and the current so P=VI or P=V^2/R if we do a bit of substituting and rearranging. From that, we can see that resistance/impedance can affect our power output. And that is probably as far as we need to go here.

What does this mean for my hi-fi?

Most hi-fi separates equipment that connects using RCA/phono connectors has been designed with appropriate output and input impedances, so there isn’t usually anything to worry about. However, there might be one area where it pays to think about impedance: you can generally ignore marketing copy that tells you to spend a fortune on hugely expensive speaker cables, for most purposes, using thick, 2-core mains cable will be fine. What you are aiming to do is to reduce the resistance of the cable to ensure maximum power transfer to your speakers. Resistance is proportional to the length of the wire and inversely proportional to the cross-sectional area, the thicker the wire, the lower the resistance. The cheap doorbell cables that come with a lot of mini systems is often quite high resistance, and you lose a lot of the power as heat. Most hi-fi separates equipment that connects using RCA/phono connectors has been designed with appropriate output and input impedances, so there isn’t usually anything to worry about.

What does this mean for my headphones?

Something you may have seen in the specifications list while headphone shopping is the impedance rating. Generally speaking, higher impedance headphones will be quieter for a given volume setting on your device than lower impedance headphones. However, you do need to consider the efficiency of the driver (you may see it in the specifications as a number followed by dB/mW). Generally though, if you have your mp3 player at 100% volume with the included earbuds (possible around 16 or 32 Ohms, you’ll probably deafen yourself, but plug in some 250 Ohm ‘phones, and you may find you’re able to listen quite comfortably. You’ll also draw less current (as V=IR), so the battery might last longer, but remember you’re trading off volume: you don’t get something for nothing.

Higher impedance headphones are often used for more ‘professional’ audio applications. The increased number of turns of wire can lead to a better ‘motor system’ in dynamic headphones, improving the general sound; also, the reduced current draw can reduce distortion in the amplifier. So, for ‘pro’ applications when you’re plugged into a powerful amp, high impedance is the way to go, for portable devices go with low impedance if you like volume.

What does this mean for my guitar?

If you’re recording your guitar DI, then make sure that you are plugged into a high-impedance (Hi-Z) input. A good rule of thumb is an input impedance of more than ten times the output impedance. Guitar pickups usually quote the DC resistance figure (there is a lot of wire when you start to add a lot of turns!) and are also inductive. Direct inputs for guitars are often rated to 1 mega ohm and higher to present a large load. Additionally, make sure that you use a reasonable quality guitar cable, as some cables can exhibit sufficiently high capacitance to cause problems. And what are these problems? A loss of high end frequencies (the output impedance and cable capacitance act as a high-cut filter) and a reduction in the guitarist’s beloved sustain.

The other area the guitarist needs to pay attention is when plugging a speaker cabinet into their valve amplifier. Valve amplifiers can be very sensitive to inappropriate loads on the output transformer. Without an appropriate load on the secondary coil, the energy in the magnetic field of the primary coil can’t be completely transferred, collapses back and sends that energy back to the valve as a ‘flyback’ voltage. This is usually not good. For that reason, use appropriately rated amps and cabs (a number of amps have different rated outputs for connecting to different cabs) and contact the manufacturer if you are unsure.

Beyerdynamic DT 880 Pro Headphones Review

DT-880 Pros are pretty well reviewed already –they’ve been around for a while, after all- so why should you read this one? Well, first of all it’s another opinion and, secondly, as far as I can find, no-one has talked about their suitability for house music production on the road using an Apogee One as an interface. I’ll assume that you’ve read some other reviews and product descriptions, so I’ll not repeat all of the basics and just concentrate on my experience with these headphones.

DT 880 Pro: Build Quality, Comfort and Appearance

Let’s start with comfort. Despite being a bit heavier than its main competitors, the Sennheiser HD650s and the AKG K701s, these are comfortable ‘phones. There isn’t too much downward pressure on the top of your head; the inward pressure feels reassuring, with a feeling of closeness without causing any discomfort, even after long listening sessions. The material used for the padding is smooth and soft, and doesn’t make your head too sweaty, which is always a bonus.

Appearance is pretty good too. The ‘phones come in a nice foam-lined zip up case and look the part. If I have any complaints, it’s that the cradles that support the cups look like a bit of a design afterthought, and the exposed cabling looks thin and fragile, but then, these headphones are cheaper than both the AKGs and the Sennheisers.

Build quality and potential long-term functionality is where I start to have issues. First off, the cable is non-detachable, being moulded into the bottom of one of the cups, so any wiring issues are going to be complicated to resolve, with higher repair bills, as described in this review. If I’m being honest, I don’t think any phones at this price point should have moulded cables, particularly those with ‘Pro’ in the name.

I’m also not sure about running that thin little cable from one cup to the other by tucking it under the detachable headband. Those cables seem very delicate, and I’m genuinely quite concerned about them snagging on something at somepoint, having them pulling out of the cups, and expensive repair bills resulting. Not sure that this feeling of breakability inspires confidence in a pair of working headphones. Compared with my Sennheiser HD555s, which were a third of the price, this cup to cup cabling arrangement seems poor.

The size adjustment is also a bit clunky, with the cup, brackets sliding back and forth in not a particularly smooth way. This is something I expect to be doing a lot of, as, with the ‘phones fitted to my head, putting them back in the case means that the moulded cable is at quite an extreme angle, and under a lot of stress, due to the snug fit in the case, so, to minimise that, I have to push the brackets back in again. Then, every time I resize, I’m concerned I’m going to catch the cables with my fingers.

DT 880 Pro: Sound

The sound performance is where the DT 880 Pros redeem themselves. These are the best ‘phones, from an accuracy perspective, that I’ve heard. The HD650s are perhaps more exciting to listen to, with the more ‘hyped’ bass response, but for critical mix decisions, I’d feel more comfortable trusting these; everything just seems more flat, and ‘egalitarian’ in the mix. Bass is low and extended, but feels well controlled. These are exceptionally good sounding headphones for the money.

Listening through an Apogee One after allowing a good length of burn in time, playing a variety of tracks showed this to be a good, reliable performer, from Alison Krauss to Maya Jane Coles, via KT Tunstall, Teenage Fanclub, Jacqueline du Pre and The Pretenders. I enjoyed the level of detail, accurate soundstage and the depth of the mix that was presented. Great performers.

DT 880 Pro: Deep House Production

So, the real reason for using these ‘phones, those late night deep house production sessions when using monitors is out of the question. After firing up Ableton Live 8, plugin 112 dB’s excellent Redline Monitor plugin into the master effects, I got to work. I can’t remember the last time I found it this easy to dial in a good kick sound. I usually layer two or three, and filter and eq to get them working together, then compress. I had a sound I was happy with in next to no time. Balancing and eqing my layered clap and snare hits was a breeze, and before I knew where I was, I had the bass sitting comfortably in a hole and, to me at least, a reasonably complete groove going on.

As I’ve discussed in a previous post, I would rather mix on good headphones than cheap monitors in an untreated room; these ‘phones have raised the bar as to what good monitors in a good room are. I can see myself spending a lot more time mixing on these, the level of detail available to make those critical decisions and hear those little distortions is fantastic. Combined with the Redline plugin, I really do have the confidence to make mix decisions on these.

DT 880 Pro: Summary

Well, the sound is spectacular, I feel happy mixing on these, and would much rather mix on these than speakers that are getting to a less than modest price point. The issue for me really is that feeling of delicacy, and, if there is a problem, a large repair bill. Despite the protective case, I can’t picture myself travelling with these ‘phones, which is a shame as it would be fantastic not to have to waste hours remixing everything when I get back to the studio. Unfortunately, I think I’ll stick to my K271 mkIIs for the road, even with their lack of bass response, purely as they feel more robust and have a detachable cable. Oh, and their closed back so I’ll annoy fewer people in coffee shops!

Update- For the Price of Cheap Monitors

After writing the aforementioned blog, I came across a post in the IDMf site, which reminded me of an article I had seen in Sound on Sound magazine (my go to source for all things audio tech). While looking searching for the article I was sure I had seen and not just imagined, I came across these two articles:

Should I mix on high-end headphones or low-end monitors?

Mixing on headphones

And thought that, given my recent blog, that it made sense to advertise their sage advice here. I have to say, you rarely go wrong with SoS!

For the Price of Cheap Monitors

When it comes to choosing a first pair of monitors, today’s producer is spoiled for choice. The number options around the £250-£350 mark is almost overwhelming. When I was getting into production again a couple of years ago, I thought that a pair of monitors was one of the first things I had to have, so rushed out for a pair of KRK Rokits.

They did the job I suppose. The bright yellow cones certainly gave my ‘studio’ as it was then some gravitas; but now, with hindsight, I’m not certain that was the best way to spend the money… While I’m well aware that all of this advice is subjective, and that five people may well give you five different answers, I’m tempted to say this: If your budget is under about £300/$500, don’t buy monitors, buy headphones.

Now, as with all rules, there are exceptions. If your room is already acoustically treated, or it’s full of soft furniture, irregularly stacked book cases and heavy curtains, you might be fine to go and spend your whole budget on monitors, but, with my room at least, coupled with the fact I needed to know how far down the low end of that kick drum went, I wouldn’t have gone with small monitors, I’d have bought a pair of Sennheiser HD650s from the outset.

Yes, headphones have their shortcomings: they exaggerate the stereo field for example, you might pan more conservatively than you would on speakers, and reverb decisions might be different as you won’t get the benefit of your room reflections. Plugins like 112 dB’s Redline Monitor can help, as can a headphone amp like SPL’s Phonitor or 2Control, which can feed some of the left signal to the right, to simulate the ‘crosstalk’ you would get from speakers. Although, with the amount the SPL units cost, you could invest in some good monitors and acoustic treatment! Still on my wishlist for late night production though.

A set of monitors will make your studio look more like a studio, but you need to be aware of the limitations of cheap monitors in untreated rooms: limited bass extension, problems with flutter echoes and reflections, peaks and troughs in the level of various frequencies across the room. All those things can be compromising your mixing decisions. Now, that’s not to say that you can’t get around some of these limitations by spending a lot of time listening to commercial mixes and learning how your room sounds. In my, albeit humble, opinion, however, at low budgets headphones have fewer cons than monitors. Try out a pair of HD650s or Beyer-Dynamic DT-880s one day and see how you get on…

This post was first published as a news item for NowThenRecords.