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AKG P4 and D40 Dynamic Instrument Mics

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AKG P4 and D40 Dynamic Instrument Mics

Postby Wonks » Fri Oct 26, 2018 3:39 pm

I've been buying a few low-cost instrument mics recently to amuse myself. Some have been pretty awful. The AKG P4 was recommended to me in another mic review by The Elf (Paul Ward), as a decent budget mic for electric guitar, so I bought one to try out. Like the majority of AKG mics now, it's an Austrian design but made in China.

Because of its similarity in shape and size to the slightly more expensive AKG D40, I had wondered if they were the same mics. So, I also ended up with a D40 in order to compare them. I'm comparing the two mics here, as others may find it useful. I bought the P4 for £43, the D40 for £60.

As you can see from the photo, they share the same housing, mounting arrangement and grille, varying only in colouring, with the P4 finished all over in a satin black. The D40 has a slightly lighter 'midnight blue' satin finish on the body, and a black grille with a silver band around it.

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Both come with a protective pouch and an adaptor to allow the mounting on the mic directly to the rim of a drum.

Both have the same clever dual thread mic stand adapter that accommodates both 5/8" and 3/8" threads (though if your 3/8" thread stands have a locking ring on them, this will need to be removed in order to screw the mic on securely. With the stand adapter an inherent part of the mic, you won't be searching for a suitable mic clip.

A quick removal of the grilles shows that they are not the same mic under the skin, as the capsules are very different. You can clearly see this from the photos.

P4:
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D40:
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Manufacturer's details of the AKG dynamic Performance (P) range are very basic; there are no polar or frequency response graphs and the P4 is described as a cardioid pattern mic, which seems to be the case.

The D40 is also described as having a cardioid polar pattern, but AKG do provide a polar chart for this mic, which shows a very non-cardioid polar pattern, with only a slightly reduced pickup from a very large rear lobe, with between 6dB and 12dB of attenuation at best. This polar chart seemed to be accurate from results during the testing (more on this later).

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So with the mics re-assembled, I did a comparative frequency response test using white noise through a Genelec M040 speaker, with each mic positioned at the same distance away from the monitor and positioned halfway between the LF and HF drivers. The output was recorded for a minute and then I used Melda’s Manalyzer in its infinite average mode for the whole of the minute’s recording to obtain a response curve for the mics. Note that this is not an accurate means of getting the mics’ frequency response, but it does show up the differences in the mics’ frequency response. You can see the responses obtained here (D40 top, P4 bottom).

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Both mics had a similar overall output level. (The average RMS value of the D40 was 0.5dB down on the P4, which in practice is nothing at all). The D40 is quoted at having a neodymium magnet, which I can well believe, as its output was significantly hotter than that of an SM58 used for comparison. The P4’s magnet type isn’t given by AKG, but for that output level, it must also be a neodymium magnet, which is a rarity at its price-point.

The mics both have a similar quoted maximum SPL of around 150dB, which is very loud indeed! I had no way to test this. The quoted frequency ranges are similar, with the D40 having a slightly higher upper frequency limit than the P4, which is shown in my comparative frequency test. But from a practical point of view for the intended main applications of guitar cabs and toms, this isn’t an issue. Even for other instruments, most HF drivers on PA systems top out at about 16kHz, so for live use, frequency-wise they would both be fine for miking up a horn section.

I then did a speech test through each mic, direct monitoring through the Genelecs at a reasonable volume so I could hear the result.

The P4 sounded clear and detailed, not a million miles away from an SM58 I used for a comparison. The bass end isn’t hyped at all, whilst proximity effect seemed minimal. The polar pattern seemed tight and as feedback resistant as the SM58. Whilst its compact configuration and built-in stand clip preclude its use as a hand-held vocal mic, handling noise was minimal, and it seemed as pop-resistant than any other good vocal mic. So, using its drum rim clip instead of the stand adapter shouldn’t cause any nasty problems, though stand mounting is probably safer - if less convenient.

I then swapped the P4 for the D40. Whoa, feedback city! Lots of low frequency feedback, probably around the 150Hz hump that’s evident from the frequency response test, and any input into the mic just made the feedback worse. I turned the monitor level down, but any speech into the mic caused low frequency blooming/ringing. Just touching the mic caused the same ringing. And this was with the mic facing away from the speakers.

I switched to headphones, and the D40 then behaved as it should, albeit with a much greater level of handling noise than the P4. So, the AKG polar chart seemed correct, and it was a lot closer in operation to an omni than a cardioid. I recorded both mics for handling noise, just tapping the casing with my finger, and the D40 definitely produced a much louder, lower frequency ‘thud’ than the P4 did.

Where the D40 does beat the P4 is with its greater bass response. I switched over to recording some guitar through an amp (Strat into a Two Rock set for a slight break-up), with both mics recording at the same time and positioned in identical locations, either side of the speaker; initially angled at 45° pointing directly at the speaker dome and the grille almost touching the speaker cloth, then both at 90° pointing about 3” out from the centre of the cone.

With the initial positioning, whilst the P4 track sounded good, the D40’s extra bass-end and wider polar pattern helped the track to sound a lot fuller than the P4 recording. Moving the mics to a position between the centre and edge of the speaker evened things up significantly. It’s a position where there is more bass and less treble produced, and unlike the 45° position, the P4 was picking up al the bass-end present, whereas its tighter polar pattern meant it would be picking up far less from the cone when angled, and the slightly brighter sound of the P4 meant that it made up for the extra treble picked up off-axis by the D40. There was nothing here that a bit of EQ couldn’t compensate for.

So, whilst AKG promote the D40 as both a recording a stage mic, for me it really isn’t going to work on stage. The wide polar pattern means that it’s going to be very prone to feedback, and if used on toms, it’s also going to be picking up a lot of sound from the cymbals. If you are miking up the toms then you’ve almost certainly going to be using overheads as well on the kit, which could mean that the sound becomes too cymbal-heavy. Also, I feel that the handling noise is too excessive to allow rim mounting, so you’ll need to stand-mount the mic.

The P4 is promoted as a stage mic, but it can do a very good job of recording guitar if positioned sensibly. The lower level of bass picked up can also be useful in a busy mix, so the guitar doesn’t clash with the bass or kick. You might have to add a few dB of bass to beef the sound up on low pitched toms – but I haven’t got a kit handy to try them on to know exactly what they’d be like on those.

Ideally the P4 would have the extra bass of the D40; then it would be near-perfect. But as it is, it is still a very good mic, especially considering its low price, compact design, rugged construction (and you won’t knock the mic off its clip if you accidentally hit it with a drumstick when it’s doing tom or even snare duties).

The D40 is more of a disappointment given its extra cost over the P4. Yes, it has the slightly greater frequency range, and the extra bass does give that fuller sound, but the polar pattern does really limit its use to the studio, but even then, thought must be given to positioning to avoid excessive spill from other instruments. It’s not a true omni, so it’s off-axis sounds are going to be coloured to some degree.

So overall, a convincing win on points for the P4!
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Wonks
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