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17 March 2011

heil_pr35_frnt copyAll heil the king of rejection – the PR 35 – the dynamic microphone that sounds like a condenser but doesn’t feed back.

Review: Mark Woods

Vocal mics have the most demanding job in live audio and while most singers would bristle at being labelled ‘conservative’ they often stick with the ageing technology of yesteryear when choosing stage mics. The time-honoured dynamic vocal microphones, complete with muddy proximity-effected lows and presence peaks – but not much else above that – are still regularly seen on concert stages. ‘Predictable performance’, ‘reliability’ and ‘low cost’ are the usual reasons given, and there’s nothing wrong with that rationale per se, but times change, and in recent years competition, modern materials and manufacturing processes have produced new breeds of vocal mics that provide better sound quality without costing the proverbial arm and leg.


The development of handheld condenser microphones has raised the bar in terms of accuracy and detail but the best models are relatively expensive and potentially more fragile than dynamic designs. Condensers also have a wide and deep pickup pattern that often results in them hearing too much stage sound. This inevitably restricts how much signal can be fed to the front of house and foldback speakers – not ideal. Like all directional mics they have a pronounced proximity effect. Condensers also need phantom power to operate. Lots of audio channels need phantom power of course, but vocal mics in particular are more susceptible to having their leads accidentally pulled out by an over-enthusiastic singer – or fan – and I hate the noise that disconnection makes through the PA.


Enter the Heil Sound PR 35 dynamic microphone, designed and built by US manufacturer Heil Sound [its company owner, Bob Heil, played a pioneering role in the development of PAs in the ’60s and ’70s, and invented the Talk Box used by Joe Walsh and others]. The PR 35 is a very different type of microphone that combines elements of dynamic and condenser designs with a few tricks of its own. Better still, it sells at a price that shouldn’t frighten anyone away.


Physically the PR 35 is a big mic, though it’s not as heavy as it looks and it feels well balanced in the hand. The mic is finished in a matte black, non-slip paint and there’s a sunken, three-position HPF switch below the head assembly. But it’s under the foam-lined grille where the fun really begins. Squeezed inside the head assembly is the largest diaphragm I’ve seen in a dynamic mic, and which is the secret to the mic’s performance. The low-mass 1.5-inch aluminium diaphragm is claimed to be light enough to allow the accurate transmission of transients but tough enough to take extreme levels. Evenly spaced phasing plugs below the grille have been designed to ensure sound entering from the rear is out of phase with sound entering from the front, resulting in an extended frequency response with minimal proximity effect and a tight pickup pattern.


The first time I heard the PR 35 in action was through my PA at last year’s Maldon Folk Festival, months before any review of the mic had been arranged. The headline act was Celtic-rockers, Claymore, and here the singer Willie Hutton had his own Heil PR 35. During their setup I noticed how loud the vocal was in the foldback. My first thought was that Willie simply had a very loud voice. When the show started the vocal was so detailed I figured it had to be a condenser mic, but I kept looking at the desk and, no, there was no phantom power engaged on the singer’s channel. The other noticeable feature was the way the vocal sat easily out in front of the (loud) band and the almost disconcerting isolation of the vocal from the rest of the band. I spoke to the band’s mixer, John Boshua, afterwards and he was happy to enthuse about how good the mic was for that band.

When the PR 35 later arrived for review I had high expectations thanks to the Claymore show and it’s been fun getting to know the mic since. It’s very different to the usual vocal mic suspects, and it challenges preconceptions about what dynamic mics can sound like. It has a distinctive tone and some outstanding qualities, but like all mics, it suits some situations better than others.

Firing it up on stage, the first thing I noticed was the tight pickup pattern and the extreme rejection of sound arriving from the side, and particularly the rear. Don’t worry about the quality of the off-axis response; there isn’t any to speak of. As a result, this mic will run louder in the foldback than any other vocal mic I’ve yet come across. It loves a ‘check-one-two’, and I didn’t really want to find full volume as the wedges were starting to rattle before it wanted to howl. High stability in the foldback will be greatly appreciated I’m sure by singers who need lots in the wedges. In this respect it’s essentially the opposite of a condenser mic – while a condenser may sound good in the PA it usually sounds live and loose in the monitors. The PR 35’s output level is also hotter that normal, and given that it’s a dynamic mic it’s possible to hot-swap it with other dynamic mics for A/B comparison. If it weren’t so stable, performing this switcheroo might cause feedback problems, however, its stability simply means it’s just much louder than regular vocal mics when it’s swapped over.

It’s a big sound too. The frequency response is flat across the midrange, with a slight rise above 2kHz and a peak between 5 and 6kHz – higher than the usual 2 to 4kHz presence peak found in many vocal mics. The idea here is that the relatively nasally, sometimes harsh bark of regular vocal mics is replaced by a shinier and more pleasing presence. There’s also a surprising amount of detail all the way up to10kHz and beyond, and this high-frequency fidelity is partly what gives the PR 35 its condenser-like quality. Despite its presence peak being in a higher frequency range sibilance is not unduly exaggerated. At the other end of the scale the low-frequency response is rich and deep with the –3dB point quoted at 40Hz. For close vocals, and with the HPF disengaged, the low-end loads up slightly but when switched to the –3dB position the thickness all but disappears. In the –6dB position the HPF delivers an accurate and uncoloured low-end. Less appealing is the slightly higher than normal handling noise and prominent plosives that that are not so effectively removed by the HPF.


In use, the PR 35 is certainly different to other mics. Performers who tried the mic at gigs while I was testing it usually noticed the difference straight away. I used it on vocals for a lot of different acts and found it evoked a range of responses. Most were fine with it once they became used to it, but twice I had singers try it and within seconds say, no, they didn’t like it – “not warm enough” – and didn’t want to use it. Others tried it in the foldback, heard the level and clarity and said, “Yes please.”

From my FOH perspective I had to get used to it as well but the noisier the act the more I appreciated the way the mic put a voice in its own space, separate to the rest of the band and with no apparent limit to how loud it would go. I found rich, weak, or dull, male vocals seemed to benefit most, with improved articulation and easy level. The lack of proximity effect left some vocalists sounding a little thin however, which made me realise just how much some singers rely on a microphone’s proximity effect for fullness in their tone.

I didn’t like it as much on vocals for quiet, delicate acts. Here the mids tended to push too far forward. So too the presence peak sitting higher than normal offered mixed results. While it removed bark from some voices, 6kHz is a risky area, especially for female vocals, and with a sharp voice it could cut your head off. Conversely, I liked it a lot when the going got tough. If you have to hear the vocal as loudly and clearly as possible, with maximum articulation, this mic could quite easily be the best you’ve tried. I did one small-PA-in-a-large-room show, and here – surprise surprise – the singer with the PR 35 was the only one I could hear clearly; the normal vocal mics were muddy and indistinct by comparison.

More than any other vocal mic I can recall using, the PR 35 suited some voices better than others. An example was a show with three pop/rock bands where I used the PR 35 on each of the lead singers. The first band’s singer had a deep and husky voice, and sounded great with the desk channel run ‘flat’ – it would have been muddy without the Heil mic and I’m certain I would have had lots of low-end wound out on the channel. The second band was younger and noisier, and during this gig the singer/guitarist couldn’t keep still while he was playing. As he moved across and away from the mic the level would rise and fall noticeably and unpleasantly. When he was in front and up and close to the mic it sounded great, but as soon as he moved away it would drop in level precariously and suddenly. We’d talked about it at soundcheck but it was the same throughout the show – the singer’s problem you might argue – and here a mic with a wider pickup pattern would have been a better fit. The male vocalist in the third band had a high voice, and while the PR 35 worked reasonably well, I found I was pulling 5kHz out of his channel to reduce hardness.


When I wasn’t using it as a vocal mic I tried the Heil on various instruments with good results. It’s a natural on drums with its tight pattern, good snap of the stick on skins and deep lows. Unusually, it also works well on cymbals, and is great at isolating what you want to hear without the washy sound of the overheads amplifying the whole stage sound. Stringed instruments were good too; the restrained proximity effect, excellent isolation and detailed highs combining well to define and lift the instruments in the mix.

In the studio I gave it a try as a vocal mic for recording. I used it for guide vocals but, as I suspected, it wasn’t a full enough sound for me to want to try it for the lead part. It did, however, make a cracking good snare mic and if I’d had lots of them and wanted to close-mic the drums, I could have used them on all the toms, the kick drum, and the overheads.

Overall I liked this mic a lot and came to look at it as both a problem solver and a viable alternate to the commonly used dynamic vocal mics. It excelled in situations where articulation is important and has the potential to improve the sound of most rock bands by improving the singer’s diction and reducing spill into the vocal mic. It would also make an excellent broadcasting mic – even callers at race meetings and users of public address systems would be better understood if they used this mic. Finally, being a dynamic mic, it also gives performers with dodgy leads (where phantom power would prove problematic), or powered speakers without phantom power, the opportunity to use a mic with similar detail to a condenser. The PR 35 ships in a padded carry case with a clip and windsock and retails for a very reasonable $379.


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