How does diaphragm size/polar pattern relate to mic applications?

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Hello Harve Master Gee, is it at all possible to increase the diaphragm size of the mic thru DIY means and change the coloring of the mic via store bought electronics?


In other words, I have a cheap Radio Whack cardiod Mic; can I alter the specifications of mic using current technology and components found in upper grade mics. I have been doing some
experimentation with this and a COBY omni and was wondering if
it can be upgraded and is it worth it?

Thx!
 
I just got on these boards and stumbled upon this thread... which is pure gold. I am only in the very beginnings, but I would hate to see this thread buried. *bump!*
 
Ok, so I found this thread and loaded all 5 megabytes of it to my palm pilot. I have missed much PreCal and English (im a junior in high school) thanks to you bastards. I'm only on page 10, yet i already feel ready to mic the world. umm............................................................... bump.
 
Wonderful Reading.

Harvey, one more thanks from another newbie. Reading this entire thread has been very enlightening. I am sure I will refer back to it time and time again.

In reading the thread I noticed you didn't have much to say at that time about Rode's NTK or NT1000. Have you considered giving them another try? With your knowledge and experience I am interested in your opinion of these microphones. I find nothing but praise. Hype or good marketing?
 
I tried to avoid being too microphone specific, since tastes and techniques often change over time.

The simple answer is that I've never heard any of the Rode mics, except for the NT-1 (and it was one of the very early units). I thought it was excessively bright at the time.

I haven't heard any of the new models, so I can't really comment about them.
 
Hey Harvey....

Any chance you might get your hands on an NTK for a trial run and review?

There's a whole lot of us NTK owners who would be interested in your "highly regarded" opinions on it.

BTW, your old neighborhood on the West side is making a nice comeback! ;)
 
I got a nice letter from the US Rode distributor about a year ago, saying that he hoped I wouldn't judge the whole line of Rode mics based on my one experience with an early Rode NT-1 and he encouraged me to try some of the other models.

I replied that I hadn't heard any of the newer models and I would be glad to give them a listen. I also told him that I'm very careful to point out in any posting I make about Rodes mics, that I've only listened to one early Rode NT-1 and that I haven't heard any of the newer models.

I think I offered to give them a listen if he wanted to ship me some test units, but that one post is the only communication I've had with anyone from Rode. He never answered my return post, and that's where it was left at.
 
I've been reading through this thread recently. Wow!

This is incredibly useful stuff.

Thanks a lot Harvey!

And yeah, this should be sticky! :)

And now for a question... Sorry if you've covered this ground already and I missed it but...

Harvey, I have a Roland VS2480 DAW, and I recently bought an AKG C3000B (which I have since seen you describe as sounding like "singing into a cardboard box" :( :D) to use with it.

As you may or may not know, the VS2480 has a mic modelling algorithm - the idea being that you can use a lower end mic to simulate a range of higher end mics. However, obviously, to do this, the algorithm has to know the characteristics of the low end mic - so there is only a few specific mics you can use for this. And one of the lower end mics that you can use to do the modelling is the AKG C3000B (this, combined with the fact that it was on sale :) was partly why I went for this mic).

As well as using the C3000B to simulate higher end mics, you can also bring it to flat line (i.e. flat response curve). I haven't had a chance to try out this properly yet (and even if I had, not having had any experience with the particular mics it models, I wouldn't be able to say how accurate it is).

I just wondered what your opinion was on the concept of mic modelling. Do you think this is a good way to go (given that I can't afford these expensive mocs)? Do you think that mic modelling as a concept is worthwhile, am I just being silly? :) I don't know enough about mics to know how successfully modelling of this sort can be done - e.g. whether it's possible to make a C3000B sound like it has a flat response curve etc.

Any ideas?
 
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I'm not sure that I have a good answer for your question. Mic modeling can only go just so far, even in theory, let alone in practice. It can compensate for "some" of the problems in a microphone, but things like resonances (which are time domain problems) can not be completely eliminated by eqing the response (frequency domain fixes). Differences in off axis response can not be taken into account either.

But in many cases, it can help (or at least, it couldn't hurt) when you're dealing with less than ideal mics anyway as your source.

If the mic you're using as a source is less than ideal, it's possible to use mic modeling to improve at least the on-axis response and wind up with a usable end product. At least, in theory anyway.

Maybe I should explain that whole "resonance/time domain vs. eq/frequency domain" bit, since it has broader implications than just microphone modeling.

Resonances are buildups of certain frequencies caused by sympathetic vibrations at those frequencies. Blowing across a Coke bottle is the classic example. The air in the bottle combined with the bottle opening creates a Helmholtz resonator which produces a specific pitch when excited.

Any thing which has a suspended mass (that's somewhat free to move) has a natural resonant point. The air column in a wind instrument has a natural resonant frequency, but trumpets, trombones, flutes, etc. get around this by adding devices that let the players adjust the length of the air column, thereby changing notes. Pipe organs simply have a separate air column for each desired note - each pipe has its own note.

Even rooms resonate, and you'll often hear people complaining about their room causing problems at different frequencies. But the important point to remember is that it takes some time to get something to resonate, and it takes time for the resonance to die away. It's a buildup/die down problem - over time. Resonances don't start the instant a specific frequency is played and it doesn't completely stop when the exciting force is removed. It builds up and dies down slowly.

Just lowering the level of a specific note won't do anything to solve the time delay problem, it just reduces the level at which the resonant peak is heard, but the time smear is still there, and very short bass notes will suffer, since they are reduced as well, and may not have been long enough duration to even excite the resonance, so you're screwing with some notes that didn't need any help, but the eq doesn't know that.

That's why it's not a good idea to try to tune a control room by using an equalizer. You fix problems in the frequency domain, but it does nothing to really stop time domain problems, and it only "helps" at one specific point in the room. Move a foot in any direction and you may have made the problems far worse.

It's the same problem with microphones - they have time domain resonance problems that simple eq can't fix.

But if using the mic modelers makes the sound "better" to your ears, go for it. It may not be the perfect solution, but if it works, it's a good solution.
 
Thanks Harvey!

I understand what you're saying about time domain vs frequency domain.

I don't know whether the mic modelling algorithm in the VS2480 is simply using EQ, or whether there's any more sophisticated processing in there to adjust the characteristics of the microphone.

I'll mainly be using it for vocals, anyway, so it'll be on-axis, and relatively close up. I'll also be recording trumpet, and possibly some sax, as well some percussion (individual drums etc. not a full kit) - and maybe some acoustic & electric guitars. How the mic (with or without modelling) will fare recording guitars, remains to be seen.
 
Hi Harvey, got a question for you,

If you take an SM57 and wrap a piece of tape (or anything) around the plastic piece that rotates blocking off the time delay back access to the diagphram, will that turn the SM57 into an omni mic? If so, will it be any good as an omni?

I got to wondering because I want to record an organ in a church and I have two SM57s and don't yet have enough money saved up to get two SP B3s so I was wondering if it would be worth the time and effort to try using the SM57s. The reason I want to use omnis is because there are antiphonal speakers at the front of the church which make a great deal of difference in the sound than when they are turned off and using the SM57s as made, being fairly directional, they wouldn't pick up much of the antiphonal speakers. Thanks a lot.

Tom
 
Tomcat,

Yes, it will work, kinda. It might also create some other resonances that aren't pleasant. Can you give it a test run with the covered SM57s a few days before your session?

What about using a pair of $35 Behringer ECM8000?
 
Hi Harvey,

I'm the church organist and go up and practice at night, so I've got all the time I need. It isn't a critical project so it can take as long as I want. I intend to eventually get a pair of SP B3s but I got to wondering about the SM57s as something to maybe try just for fun and learning in the meantime but didn't want to waste my time if it was a totally absurd thing to do. Thanks for your reply.

By the way, just as an aside; from reading your posts over the months I had visualized you as probably a congenial heavier set Willy Nelson and I finally looked at your studio site and I was damn close!

Thanks for caring enough to take the time to do all you do for people learning recording. I'm 68, retired and having as much fun as I've ever had playing around with recording, but it will never be on a professional basis. However, that doesn't mean I don't want to know as much as possible about it.

Tom
 
Tom,

Is this an electronic organ or a pipe organ? SM-57s won't make you sound like E. Power Biggs, but they should give you a very servicable recording, if they're placed right.
 
It's a current top of the line two manual Rodgers Trillium 807 electronic that sounds amazingly like a real pipe organ but without the reeds going bad all the time and without the temperature pitch changes. There are two sets of three speakers about 15 feet apart at the front railing of the choir loft and then two, one on each side, antiphonal speakers at the front of the church about 70 to 80 feet away from the rear speakers.

I have thought about setting the mics up at the front of the church pointed to the rear in order to pick up both sets of speakers but am certainly open to suggestions for best placement. Thanks again.

Tom
 
Since I'm basically lazy, my first question would be, "Does the organ have a stereo line out, and what does that sound like?". You might wanna just record that and add some room ambience mics to fill it out.

If you want to go the all miked routine, I'd get another organist in there, and while he/she is playing, walk around the room, looking for "sweet spots" to place your mics. For starters move in close to the main speakers and then back away till you hear a nice balance between the direct sound and the reverberation in the room. That may be anywhere from 1/3 of the room away to 2/3 of the room.

Too much reverb will produce a muddy, indistinct recording, while too little reverb will create a dry, clinical sound. Look for a good balance between those two extremes. Go for a little less reverb than you think sounds right (a little reverb goes a very long way).
 
The organ is fully midied and has a little black box called a PR300 which allows me to start recording, set the pistons I want, then record whatever I play and store it on floppy. I can then play it back on looped and go downstairs and listen to it anywhere in the church, over and over as long as I want.

I was really amazed when they finished the installation and I played back the demo disk I got and walked around the entire church because there was no dead spot! It sounds very even all over the church from back to front and left to right; there isn't even very much volume difference right under the rear speakers from what there is at the front (if the antiphonals are on). The Rodgers folks did a very, very good installation. The guy who did most of the installation was George Kirkwood, who worked for Rodgers for over 30 years and retired as head designer and chief of the design department. He had been the organ caretaker for Virgil Fox and went on tour with him to make sure the organ was always in top notch condition in addition to having designed "black beauty", the organ Fox played. George is a year older than I and was "encouraged" to retire at 65, ie, he was given a bonus and sent out the door!

George told me that those particular speakers have an ellipsoid sound pattern aligned with their long axis so four of the back speakers are vertically oriented as two pair one on top of the other and the other two come off the middle of the pair and are horizontal, ie there are two vertical and one horizontal on each side of the choir loft. That way they cover the church space more evenly.

The organ does have a line out, but I don't particularly care for the sound as it's pretty sterile. The ring time in the church is about 2 seconds so it has a good ambience and doesn't get very muddy.

Tom
 
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