Bob Heil on large-diaphragm dynamic mics

Tuesday, July 15th, 2008 | by

Working on the Heil pages of the mic database the other day, I got to wondering exactly how a dynamic mic could be described as “large diaphragm.” Was it simply a matter of the voice coil being an inch or more in diameter? I’d seen a handful of “large-diaphragm dynamic” mics, but the qualification had never been explained.

I put the question to the man who could answer it best — Bob Heil, father of the new line of large-diaphragm dynamic mics that are getting great reviews for everything from live vocals to studio drums.

Mr. Heil was gracious enough to not only answer my question, but to tell the birth story of this line of microphones and even give a little tour of the catalog, too.

Bob wrote,

“Yes, most every dynamic microphone is 1/2'' to 3/4'' in diameter. The technology has not really changed in over 30 years and we did not have the magnet strength nor material to make large diaphragms ‘behave’ … thus, the market has been stuck with mushy, mundane-sounding dynamic microphones.

“Joe Walsh was the instigator here. My friend of nearly 40 years and an avid ham radio buddy, he asked me a few years ago to build him a better microphone — as he was standing beside one of his 7' high radio transmitters. Looking up at the top of it he said, “You know, Bob, the bigger things are, the better they sound. Build me a big microphone.” Almost in jest, I did just that. I wound a large 1.5'' diameter dynamic, but of course, I discovered quickly why no one else had done this. It had no dynamic range, ridiculous frequency response — it was not good. But when talking about the reasons with Joe, we figured it out, made some corrections and improvements and bingo, the PR 30 was born.

“To achieve better dynamic range with the large diaphragm, we needed a stronger magnet. I discovered that by mixing several components together we could get a super magnet. In order to keep the large diaphragm intact, we made the outer surface lighter than the inner. The result was dynamic range and frequency response rivaling condensers costing five times as much.

“I then started working on [rear] rejection. Not a single dynamic ever had good rejection and we absolutely know that overly sensitive condenser mics will not have any control from the rear, or very little. Leaning back on my knowledge of building massive antenna arrays, monsterous 16' speaker horns, voicing and tuning large Wurlitzer theatre pipe organs and spending time with my mentor Paul Klipsch who taught me so much about tuning and phasing, I was able to come up with a very special microphone design that gets -40 to -45 dB of rear rejection from our dynamic microphones. That’s unheard of, until now.

Heil Sound PR-30“The PR 30 is fast becoming the ‘go-to’ microphone for live sound stages. It is superb on guitar cabs as it will handle 145 dB of SPL, has this incredible amount of side and rear rejection, and frequency response equal to or better than some condensers. Just what the doctor ordered for overheads! Now instead of the microphone hearing everything from the 5th row to the back stage wall, you hear just gorgeous cymbals. Immediately, the sound is so clean and clear. It is being used in many award-winning studios by Grammy-winning producers. It is used in hundreds of network broadcast stations and replacing overhead condensers by the dozens each week once the engineers get over the feeling of actually getting rid of their condensers.

Heil Sound PR-40“The PR 40 is very similar with the addition that it will get down to 28Hz and stay out to 18K. It truly is a remarkable microphone for kick drum, bass guitar, and is used in over 1,000 broadcast and podcast stations. Thanks to Joe, all of the new HEIL PR series have this gorgeous articulation. Every [other] microphone out there has a 2K [presence] peak. That is not where the human ear needs to have great speech and vocal articulation. 2K is a nasal sound. I moved it out an octave — exactly where the ear is listening to hear the difference from a p or b, f or s.

Heil Sound PR 22“Take a look at the new PR 22. This is replacing the usually 40 year old ball mic by scores each day. It is has the widest frequency range, the most incredible articulation, and absolutely no handling noise. This is an amazing vocal mic but yet is being heralded as the best snare drum microphone — ever.

Heil Sound Handi Mic Pro Plus“The Handi mic is an amazing product. Only 4.5'' long, it fits inside Leslie speakers, in and around toms and cymbals and sounds terrific.

Heil Sound PR-35“… and then the PR 35. Each day we hear of yet another music icon laying down their 40 year old technology for this incredible microphone. 1.5'' diaphragm mounted in an internal shock mount of this gorgeous feeling hand microphone. Again, -40 dB of rear rejection and the best articulation of any dynamic microphone.

“The best part of all Heil microphones is that little, if any, EQ is ever needed. It catches a lot of engineers off guard as they have never had a microphone that performed like the Heil PR line-up.”

Bob Heil, you rock! Thank you.

To clear up a possibly confusing point: Bob was relating the birth story of the largest of the Heil large-diaphragm mics, the PR30 and PR35, whose coils measure 1.5'' in diameter. In a sense, the PR30 was a second-generation large-diaphragm design.

But the first generation was also instigated by Joe Walsh, who requested a pro-audio version of Heil’s ham-radio mic, the Goldline:

Bob Heil

This new PRO division started when Joe asked me to build him a better microphone. One that had wider frequency response, move that usual 2K nasal peak out an octave to produce some of that natural articulation of our communication mics and extend it to 18K. The PR 20 was born.

The PR-20, formerly called the Goldline Pro, had a 1.125'' coil and had been on the market for about a year when the PR-30 was released.

Anyway, I’m not sure I’m ready to believe in dynamic mics for drum overheads, but I will absolutely try them out in my next drum mic shootout. Stay tuned.

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Posted in Interviews, Microphones | 6 Comments »

6 Responses to “Bob Heil on large-diaphragm dynamic mics”

  1. tom fields

    July 11th, 2014 at 3:53 pm

    i managed to aquire a bunch of old odd mics one of them being a stromberg carlson the mic was intact with an aluminum diaphragm which was pretty beat up it has a 3/4″ voice coil and a completely flat back plate. I’m finding almost impossible to even find remanufactured parts. is there any one out there who could help me.

  2. phil

    November 3rd, 2014 at 3:44 pm

    I host a gig once a week at a local pub. the unusual thing about this gig is that we don’t get on stage. we sit around a table and play acoustic instruments and sing with no amplification. the unique ambiance this creates has been a huge success but there’s a problem. when the room gets too full of people or has a loud table not paying attention to the music we get drowned out. I’m thinking of plopping a mic in the center of the table and running it into the back of a couple of powered monitors. would the PR 30 do the trick? will it pick up the music from all sides if its sitting on a mini mic stand pointing straight up? thanks

  3. matthew mcglynn

    November 3rd, 2014 at 5:41 pm

    @Phil, that won’t work at all. The PR30 is Cardioid, if not Supercardioid. That means you’d be miking the ceiling. The microphone would hear a lot of low-fi reflected sound from you and the entire room.

    It would, of course, pick up sound from the sides, although there would be at least a 6dB loss in sensitivity at 90 degrees — and possibly more if the mic’s pattern is narrower than Cardioid.

    You could use an omnidirectional mic on the table, but I doubt it would sound good as it too would be hearing the entire room.

    Given that you’re sitting in the midst of a loud audience, I think your only options are to either stay acoustic and deal with the fact that you sometimes get overpowered, or to close-mic every instrument and use a mixing board to set relative levels for playback through the PA.

    If there was more separation between audience and performers, or if the audience were listening rather than competing with you, then you might have other options.

  4. colleen varlow

    July 23rd, 2015 at 4:06 pm

    I am wanting to mic a choir of around 20 people, would the PR30 do the trick? Where would I place the mic, overhead or just in front?

  5. matthew mcglynn

    July 23rd, 2015 at 7:56 pm

    @Colleen, I would not recommend the PR30 or any dynamic mic for any sort of ambient/live recording. Dynamics might work as a soloist mic or spot mic, but would need to be positioned close to the singer or instrument.

    For live recording of a choir or ensemble, use a condenser microphone, or preferably two. You would have to experiment with positioning to determine what sounds good in the specific space where you’re recording.

  6. Barrett Abney

    December 8th, 2016 at 7:08 am

    Matthew, you placed the PR 30 outside the bounds of good choir micing? Why? Bob has stated over and over that this mic is perfect for Choirs.

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