The Definitive AKG C451 B Review

The bright open mic with the silkiest highs
AKG C451 B Review hero image

Reviewed by: Paul Narang
Review date: May 2024
Current price: Between around $400-$600

AKG C451 B cardioid small diaphragm microphone
AKG C451 B cardioid small diaphragm microphone
AKG C451B Review
Pros:Cons:
Bright sound with silky top end
Extremely versatile
Compact and durable
2 attenuation pads
Low cut filters
Prone to plosives on vocals
Fixed cardioid polar pattern

AKG C451 B Review

The AKG C451B is a small-diaphragm condenser mic that delivers a balanced and detailed sound. Its bright yet silky presence makes it an excellent choice for capturing the nuances of acoustic guitars, drums, stringed instruments, pianos and more.


What is it?

AKG Acoustics is an Austrian pro audio company founded in 1947 in Vienna by physicist Dr. Rudolf Goerike and engineer Ernst Pless. From the beginning, their focus was on developing high-quality dynamic and condenser microphones for recording, broadcast and live sound applications.

The cardioid C451B pencil mic is AKG’s most popular small-diaphragm condenser, an extremely popular staple in both professional recording studios and live settings.

AKG C451 B is a great mic for studio and live use
AKG C451 B is a great mic for studio and live use

The C451 series which dates back to the late 1960s with the release of the C451E and C451EB models, which were much favoured by many established recording engineers until they were discontinued in the 80s and 90s, when brighter mics became less popular due to digital recording.

These old models had interchangeable capsules for different polar patterns like cardioid, omni and figure-8. But this modularity came at the expense of some durability issues that have now been addressed in the latest C 451 B, which is a fixed polar design. And of course bright mics are firmly back on the map as a stylistic choice.

You can also buy the C451 B as a matched pair, where both mics are manufactured at same place around the same time. They come in a hard carrying case with the inclusion of a stereo mounting bar. C451 Bs are now made in Hungary rather than Vienna, but I’m not sure it makes much difference!

AKG C 451 B in the foam padded case
AKG C 451 B in the foam padded case

In the box

As well as the microphone, the C451B ships with:

  • Stand adapter (SA60)
  • 5/8 to 3/8” thread adaptor
  • Foam wind shield (W90)
  • Padded case
AKG C451 B outer packaging

AKG C451 B Polar pattern

The AKG C451 B has a fixed cardioid pickup pattern, which forms a heart shaped area in front of the mic. It works as you’d expect a mic to work – picking up most of the sound from the front, but far less from the back and sides.

Condenser mics like the AKG C451 B often have a cardioid pattern
Cardioid pickup pattern

The cardioid pattern is a great choice for home studios where there hasn’t been much acoustic treatment. It will pick up the sound of the vocalist or instrumentalist in front of the mic, while rejecting the sound of the room.

AKG C451 B with stand mount and foam windshield
AKG C451B pick up pattern at different frequencies

Take a look at the diagram below to see how the cardioid pattern changes on the 451, depending on the frequency of the sound being recorded.

Note that the heart shape is most pronounced in the midrange, but at 8kHz it becomes very slightly more omnidirectional. At 16 kHz there is slightlty more pick up at the back of the mic.

AKG C451B pick up pattern at different frequencies
AKG C451B pick up pattern at different frequencies

The development of the C451B

The C451B, reviewed here was released in 2004. It’s the newly revived incarnation of the original C451 series from the 60s and 70s. The C451 B was designed as a more robust and roadworthy fixed-capsule design, aiming to maintain the classic sound of an old C451 E and the later C451 EB with a CK1 capsule

The old series of C451 models used threaded capsules which screwed together. This was a system that many engineers liked as they could swap out the capsule into an omnidirectional (CK2), hypercardioid (CK3) figure of eight (CK4), and shotguns (CK8 or CK9) to suit their needs at the time.

You could also screw in an attenuator if the sound source was too loud, or a high pass filter, if you were recording hi hats. The trouble with this system was that the connecting parts weren’t particularly robust, and were prone to debris build up, needing regular cleaning to maintain their sound without crackle or noise.

The C 451 B was AKG’s answer to these problems. They redesigned the CK1 capsule as an electret capsule, and removed the transformer from the amplifier stage. This resulted in a better transient response and lower self noise.

The tough metal body and grille of the C451 B
The tough metal body and grille of the C451 B

The new C451 B was contained within a fixed body, which eliminated the potential noise issues while making it more resistant to humidity, and temperature changes. AKG also claim that it is more resistant to being dropped.

To replace the screw in attenuators and high pass filters, the C451 B has integrated switches, offering all the capabilities of the old C451 EB – bass cuts at 75 and 150 Hz, and attenuation of either 10dB or 20dB.

Phantom power for the AKG C451 B?

As a condenser microphone, the AKG C451B will need phantom power.  Phantom power is low voltage current sent to the microphone from a microphone preamp, mixing desk, or audio interface, sent through the XLR cable to the microphone.

If your audio interface or mixer doesn’t provide phantom power, there is another solution: connect your mic to an external 48 volt phantom supply. Then connect the output of the phantom supply to the mixer, or audio interface.

XLR connection on the back end of the C451 B
XLR connection on the back end of the C451 B

Connecting the C451 B

The C451B uses an XLR cable to connect directly to the audio interface or mixer. XLR is the standard connector for professional studio equipment. An XLR connector is ‘balanced’, which means the cable is shielded from interference and carries a higher signal than unbalanced cables.

XLR cables are the only cables capable of carrying phantom power to the mic.

More about cables here

The AKG C451 B Design and Build

The C 451 B is a small discreet pencil mic packed with features, and housed in a sturdy metal case. It has a recognisable look, with the smooth satin nickel finish and two bright orange switches along the body.

Inside the mic is AKG’s CK1’s electret cardioid capsule, paired with a transformerless preamp circuit, which offers a clean transient response.

It uses surface-mount technology (SMT), where the components are attached and connected on the surface of the circuit board using a more efficient process than the normal way of inserting components through-holes and soldering. As well as being able to fit more into a small space, SMT produces higher reliability.

The two switchable filters providing attenuation and high-pass options are both indented, so there’s no possibility of accidentally changing the settings while setting up, or playing live.

C451 B Pre-attenuation Pad Switch

AKG C451 B Pre-attenuation switch, offering 0, -10db or -20db

The pre-attenuation pad prevents distortion when miking extremely loud sources or driving preamps or mixers with limited headroom. You can switch it to cut 10dB or 20dB as needed. The max SPL without attenuation is on the lower side at 135 dB, but with a 20dB cut, you can increase that to a healthy 155dB SPL for a high overload limit

C451 B High Pass Filter Switch

AKG C451 B high pass filter  switch, offering bass roll off at 75 Hz of 150 Hz

The high pass filter has 12dB per octave slopes of 150Hz, or 75Hz to minimise low frequency rumble, air conditioning, wind noise or traffic noise reaching the capsule. This helps ensure the cleanest sound capture at source.

I found the 75 Hz seemed to suit many recording scenarios, and always engaged the 150Hz setting for hi-hats and cymbals and other very high frequency instruments.

AKG C451 B Dimensions and Weight

AKG C451 B Dimensions and Weight
AKG C451 B Dimensions and Weight
  • Dimensions: 160mm (6.3″) x 19mm (0.7″)
  • Weight 125g (4.4 oz)

The compact size and very light weight make the C451 B an unobtrusive mic, good for getting into tight spaces, and light enough to put on the end of a long boom arm without causing it to droop. You could also carry several of these to a location recording in a small back pack.

AKG C451 B frequency response

The C451 B has a full frequency range of 20Hz – 20kHz, typical for a quality small-diaphragm condenser mic. First of all, the C 451 B is an unashamedly bright mic, but that doesn’t mean harsh, or clinical sounding.

AKG C451 B frequency response with both bass roll off settings
AKG C451 B frequency response with both bass roll off settings

Looking at the frequency chart, there’s a gentle 2-3dB lift starting at 5kHz which gives the C451 B its characteristic silky, detailed and open top end. This is what makes it so popular for acoustic guitars, classical guitar, other plucked or bowed strings, and drums. Apart from that it has a reasonably flat, balanced response through the midrange frequencies.

Without any high pass filters engaged, the bass rolls off smoothly below 100Hz to minimise an exaggerated proximity effect and low frequency rumble. I did try speaking very close to the mic, and there was a clear increase in the bass, but it sounded very natural.

AKG C451 B has a detailed and open top end
AKG C451 B has a detailed and open top end

AKG C451 B Sensitivity and Impedance

Microphone sensitivity gives us an indication of how well the capsule is translating sound pressure levels into electrical output levels. The more efficient it is, the more sensitive the mic.

The C451B’s sensitivity of 9mV/Pa is very high, especially when you consider its a small-diaphragm condenser mic which can handle pretty high SPLs (up to 155dB) with the pad engaged.

This high sensitivity allows it to capture extremely quiet and nuanced sounds, but there’s pros and cons to having a very sensitive microphone:

High sensitivity vs low sensitivity mics

Highly sensitive microphones are able to pick up a lot of detail, and capture sounds from quieter sound sources. These mics are often used to make more ambient room recordings in jazz and classical music. They can also be great for capturing the fine detail of a vocal or instrumental performance in the studio.

The downside is that they’ll also pick up a lot of ambient detail So as well the fines nuances of your vocals, there may be some background noise or room reflections.  This isn’t a problem if you’re recording in a well-isolated, acoustically treated studio space.  But for most of us, who record at home, this simply isn’t possible. 

The AKG C 451 B is a high sensitivity condenser mic
The AKG C 451 B is a high sensitivity condenser mic

The AKG C451B impedance level

The C 451 B has a low impedance of under 200 ohms, which is typical for modern condenser mics. This allows for long cable runs without signal degradation, or high frequency roll-off.

The low impedance design maximises headroom and maintains a flat frequency response when connected to a high impedance input, common to an audio interface or mixer. The C451B’s impedance gives it the flexibility to be used across a wide range of mic preamps without any issues.

AKG C451 B abstract illustration

AKG C451 B Sound Quality

I was really looking forward to getting my hands on a C451 B for testing. I’ve used them before, along with the older C451 EB models, (which sounded very similar) and remember being very impressed.

Just as expected, the C451 B is a bright sounding mic, with an extraordinarily natural sound. It seemed to capture the essence of any instruments I put it in front of, though I’ll describe in detail later how it responded to particular instruments, including vocals.

Recording acoustic guitar with the C451 B

The C 451 B has a slightly scooped, although finely balanced sound. Its forte certainly includes acoustic guitars, where just one mic is capable of achieving a 3 dimensional hyper realistic reproduction – silky smooth sparkling highs, balanced with full low-mids.

The 2-3dB gentle presence boost in the top end provides an airy sound, drawing out detail, articulation and attack without being harsh or brittle. Yet when listening back, it simply sounds uncoloured and unprocessed – very much like I heard it with my own ears.

For recording acoustic guitar, I placed the C451 B 6 inches away aimed at the 14th fret. I angled it slightly towards the guitar body to capture the lows and more resonance. A stereo pair would work well here too, for a wider stereo spread.

The distinctive metal grille of the C451B
The distinctive metal grille of the C451B

Recording piano with the C 451 B

I tried the C 451 B with a mini Eavestaff piano, which has quite a delicate, warm and thin sound. It sounded excellent placed in several positions, brightening up any hint of dullness, especially at the top end. The piano actually sounded a lot better than it does in real life.

I’m not sure how it would respond to a modern grand piano, though I’ve been reliably told it’s a good mic for recording pianos. For this scenario, I’d want a pair of C451s, one covering the bass and the other over the mid section.

Recording vocals with the C451 B

You may not associate the AKG C451 B with recording vocals, but they have a long association with voice overs and singers.

Madonna and Joni Mitchell and other prominent singers recorded with the older (but very similar sounding) C451s, and they could be seen on TV productions throughout the 70s and 80s, from shows and interviews to news desks.

With a dynamic range of 117dB (A-weighted), I found the C 451 B to respond beautifully to my own male voice while recording voice overs, and I particularly liked the sound of the proximity effect when I spoke very close to the mic. Using it with the foam windshield dampened the highs very slightly, and is worth experimenting with.

AKG C451 B with attached foam wind shield
AKG C451 B with attached foam wind shield

Recording drums with the AKG C451 B

The AKG C451 B is a natural and popular choice for recording hi hats, cymbals, and shakers, as well as drum overheads, especially in stereo pairs. It has a knack of bringing out the highs without any harshness. An old trick is to combine a 451 with a Shure SM57 on snare for a sound which captures both the body and the detailed highs simultaneously.

The ‘self noise’, noise generated by its own mechanics on the C451 B is 18 dB-A which is a little noisier than some other similar mics, such as the Neumann KM 184 at 13 dB-A. But that’s not something to be concerned about, as I wasn’t aware of it at all until reading the specs. Make sure to use it with a high quality pre amp for decent results.

The sound of the 451 B is suited to a variety of instruments: drums and guitars, as well as the less obvious – pianos, violins, violas, cellos and vocals. Its actually a mic worth considering for any instrument if you know that it will need to cut through the final mix.

I’d describe the sound of the AKG C451 B as being open and realistic, bright yet smooth. It excels in producing clarity and detail within the fine textures and resonant overtones.

AKG C451 B in the recording studio

The AKG C451 is a nice compact size to have in the studio, as it makes mike placement simple in a cluttered space. There’s all the easily accessible filters to make sure you’re getting the right sound at source.

For instance, with the 75Hz high pass filter applied, you’re cutting out any potential rumble, without affecting the fullness of the low end. And engaging the 150 Hz high pass filter will ensure clean cymbal and hi hat recordings.

AKG C451 B with attached windshield and stand mount
AKG C451 B with attached windshield and stand mount

The noise-rejection casing combined with a very light diaphragm means you can handle the C 451 B without any problems. This is useful if you want to hold it for recording vocals, though I’d suggest using a pop filter to control any plosives.

When I tested everything apart from vocals, the single mic was placed on a stand with its own stand adaptor.

The AKG C451 B - slim and unobtrusive in the studio
The AKG C451 B – slim and unobtrusive in the studio

The cardioid polar pattern of the C451 B did a good job of rejecting sound from the sides of the microphone. It was also very good at rejecting sounds from the rear, which might be helpful for you if your recording environment is compromised.

Condenser vs dynamic microphone

The two most common types of microphones are dynamic microphones like the Shure SM57 (reviewed here) and condenser microphones like the AKG C414 (reviewed here).  These two types of mics each have pros and cons and both are useful in different ways.

Dynamic microphones

The mechanism inside a dynamic microphone is more durable and sturdy than a condenser, making them ideal for live gigs. They’re also less likely to be damaged during the rough and tumble of touring life.  Dynamic mics are generally less sensitive than condenser microphones, and better at rejecting background noise and feedback.  But the lack of sensitivity means they aren’t capable of reproducing as much nuance or dynamic detail, especially in the higher frequencies.

Condenser microphones

By contrast, condenser microphones have quite a delicate mechanism, so you’ll need to take good care of them.  They’re able to record with greater detail and clarity than dynamic mics, often with a bright and sparkly top end.  This is often just what you need for studio recordings, which is where you’ll find the majority of condenser mics.

The full C451 B kit - windshield and stand adaptor
The full C451 B kit – windshield and stand adaptor

With the main benefits of the AKG C451 B being the prominent silky high end, it wouldn’t make sense to swap it out with a dynamic mic, as you simply wouldn’t be able to achieve similar results.

AKG C451 B vs Neumann KM184

AKG C451 B vs Neumann KM184
AKG C451 B vs Neumann KM184

If you’re a guitarist, you’ll be fully aware of the debate between the AKG C451B and the Neumann KM184. They’re both been considered classic guitar mics for a long time, and are both capable of phenomenal results. In general they’re rather similar sounding small diaphragm mics with a bright sound, and a gentle lift at around 5 kHz. But there are some important differences.

The KM184 is better for midfield and long field miking, and can be extremely sensitive to plosives if you’re singing into it. Whereas the C451 B sounds great when close miking, as well as a distance away. And it suits some vocals very well.

The Neumann KM184 has an SPL of 138 dB, which is on the low side, but won’t be a concern for midfield recording. Whereas the AKG C 451 B has built in attenuation controls, so it can switch between 135dB, 145 dB and 155 dB if needed, for close miking loud instruments. It also has the addition of bass roll off switches which help to get a clean sound without the risk of rumble. In contrast, the KM 184 has no switches or controls at all.

They’re both light mics, with the KM184 considerably shorter and slightly thicker than the C451 B. But the C451 B is slightly brighter in sound. In a direct comparison, to my ears, the C451 B sounds like an EQ’ed version of the KM184. It has more of a delicate, refined, scooped sound, with a sparkling airy top. It’s instantly balanced, so you won’t have to mess around with EQ too much in the mix.

Whereas he Neumann KM184 his a fuller sound across the frequency spectrum. You could describe this as warmer, darker, or even muddier, depending on what you’re recording, or the mix its going into. With that warmer sound though, it does open up the possibility of recording a larger variety of bright instruments, such as horns, trumpets or saxophones.

Both mics have minimal off axis coloration, but the KM 184s have slightly less ‘self noise’. They rate at an impressive 13 dB-A rather than the 18dB-A of the C451s. They both perform well as stereo pairs on drums, but the Neumann will have more uses as a midfield stereo pair in recording choirs and orchestral sections. The C451 Bs may be too bright for this, unless of course the choir’s dull sounding and you need a dose of that classic 451 ‘sizzle’.

Read the full Neumann KM 184 review here

AKG C451 B vs Shure SM81

AKG C451 B vs Shure SM81
AKG C451 B vs Shure SM81

The Shure SM81 is another small diaphragm condenser microphone with a cardioid polar pattern, also popular for recording acoustic guitar and drums. It has a largely flat frequency response, compared to the 5kHz peak of the brighter C451 B.

Like the AKG C451 B, the Shure SM81 also has switchable high pass filters, but at different frequencies. Where as the C451 has the options to switch in 12dB per octave slopes of 75Hz and 150Hz, the SM81 has switches at 8 dB per octave at 80 Hz, and 6 dB per octave at 100 Hz.

Both mics aim to give you two options with these switches – one setting for very low noise and rumble, and the other setting to cut out any lower frequency sounds while recording sounds such as hi hats and cymbals. The SM81 is more susceptible to the proximity effect, so the high pass filters come in very handy to mitigate the rise in bass frequencies.

The SM81 has a very slightly lower self noise at 16 dB which is just 2 dB less than the C 451 B, and they share the same frequency range of 20 Hz to 20 kHz. The two mics also have very similar max SPLs – 136 dB on the SM81 compared to 135dB on the C451B.

But both mics also offer attenuation options too. In the case of the Shure SM81, you can cut 10 dB, effectively raising the SPL to 146 dB. But it’s a complicated process – you have to unscrew the grille and make some changes inside before putting it back together again.

The AKG C451 B has the much easier option of switching in a 10dB cut or a 20dB cut from a switch on the side when you need it. THis effectively raises the max SPL to 155 dB, 9 dB higher than the SM81.

Both microphones are robust, and can handle very harsh conditions, including temperature changes and humid atmospheres. The SM81 is heavier at 230 grams compared to the 125g of the C 451 B, and it’s also longer at 212 mm (8.34 in) and thicker in diameter 23.5 mm (0.92 in).

I would consider the Shure SM-81 to be a solid choice as a small diaphragm cardioid condenser, especially if you’re on a budget, but to my ears, it lacks the sparkle and shimmer of the C451 B.

Coming soon – the full Shure SM81 review.

What else do you need?

The AKG C451 B only comes with a stand-mount, so if you’re adding one to your mic locker, you might have to also consider these accessories:

  • Pop filter

A pop filter is a ‘must have’ if you’re thinking of recording vocals or voiceovers. It will eliminate plosives – those short bursts of air which can add ruin a recording. You can make one yourself out of an old pair of tights, or easily pick up an inexpensive one.

  • Microphone stand

Studio condenser mics like the AKG C451 B are normally mounted on a stand, to reduce any handling noise. Try a good quality boom stand, with a tripod base like the K&M 210/2

  • XLR cable

If you’re investing in condenser microphones for your studio, start getting into the habit of using good quality cables. That way, when you add more high quality mics, you can use the same cables. If you want the best quality XLR cables, try these. Go for the shorter lengths where possible.

The AKG C451 B - a beautiful sounding workhorse for the studio
The AKG C451 B – a beautiful sounding workhorse for the studio

Conclusion

The AKG C451B is an outstanding small-diaphragm condenser microphone that I found impressive on many levels. It’s a good all rounder, but really excels in producing high quality guitars and drum recordings, where you need a bright, beautiful and inspirational sound.


AKG C451 B Frequently Asked Questions

Does the AKG C451 B need phantom power?

The AKG C451 B is a condenser microphone, so it does require phantom power. You can receive power from the mixing desk, audio interface or a stand-alone unit

Can you use condenser mics on stage?

Condenser mics are a great choice for stage use as long as they have been designed specifically for live use. They’ll deliver a higher quality sound than dynamic mics.

What instruments is the AKG C451 B good for?

The AKG C451 B is an extremely versatile mic, widely used for hi hats, cymbals, drum overheads, violin, viola, cello and piano. It also suits some vocals

Read about our pick of the best mics for recording vocals