a large diaphram dynamic mic thoughts and opinions wanted

[pucho812]

So I been doing some lite DIY stuff and some mods. gotta start somewhere. Was thinking one what makes a 57 sound how it sounded so I took one apart. It is basicly a capsule and a trafo. My original mad scientist idea was to stick a tube in there and still kicking that idea around. but back to the point.
I am thinking one could diy a large diaphram Mic in a similar fashion to design of a 57 using say a peluso capsule and a trafo. Not a new design, nothing fancy, just straight simple to the point. THe only real differnce is that fact it is a large diphram.
Any thoughts or opinions on this?

 

[tk@halmi]

Can you clarify what you are proposing?
You want to see a large dynamic element?
OR
You want to hook up a large diaphram condenser to a transformer without active electronics?

 

[Bear]

You can get off the shelf dynamic elements, but I don't know what the quality of them is. Most of the stuff in mass production is not designed for music or pro audio, but for stuff like telecom, so only a handful of components are likely to be of interest.

Keep in mind that unlike the condensor mic elements, most of which are single membrane and with the porting already set in the backplate for the pattern (if I understand this correctly). The difficulty in doing the DIY dynamic is probably going to be in the porting. Unless you have an element voiced for omni and do a true pressure gradient setup. But when used EV 635a's are so cheap, that seems like a lot of work.

Bear

 

[pucho812]

Can you clarify what you are proposing?

Sure

basicly it's like this. the SM57 is mearly a capsule and a trafo. but the SM57 is a small diaphram(capsule). So what I have in mind is a mic much similar to a 57 design but large body and large capsule. So what came to mind was getting a good capsule like a peluso 47 knockoff and wiring it up directly to a trafo. No active electronics thus negating the need for 48Volts phantom. Basicly a 57 ripoff but instead of being small diaphram large diaphram. Picture it like this a u-47 but on the inside the capsule is wired to the trafo point to point and then to the XLR jack(Ala SM57 design)

opinions thoughts?

 

[soundguy]

Im not mic guru or anyhting, but a condenser capsule does not work like a dynamic, there has to be a charge present on the capsule in order for it to work... There arent passive condenser mics for a reason. Conversely, the "active" ribbon mic isnt "active" at all, there's just a fet buffer stuck on the output of it, the mic itself is still passive. You can put that fet buffer on any ribbon mic.

dave

 

[pucho812]

not mic guru or anyhting, but a condenser capsule does not work like a dynamic, there has to be a charge present on the capsule in order for it to work...

:thumb:

my microphone 101 is comming back to me. dam how much one can forget with lack of sleep.
The idea was/is to have a dynamic mic much like a 57 design but in a 47 type body and larger mic capsule. thus having the look but not the cost. after my reminder of condenser capsules, I am now thinking like an EV Re20 capsule connected to a trafo point to point out to XLR jack.
thoughts comments?

 

[Bear]

That sounds alot like a Stedman N-90. Rugged Neuman-esque housing, large EV-made dynamic mic element. Not a bad mic. Shouldn't have to pay more than $150 for one on ebay ever.

Bear

 

[pucho812]

my buddy has a stedman n-90. Not bad by any means. I didn't think the steadman was that simple. He got it for fixing some dudes computer. I wanted to take it apart but dam was impossible to get into I couldn't get the base to unscrew. So yeah something like that but in a longer 47 esq body for look or even RCA body for look.

 

[PRR]

The SM57 capsule is not "merely" a capsule, but a complex system. So are condenser "capsules", just different details (like how it turns motion to electricity).

Sure, big-diaphragm dynamics are everywhere. Wire a table-radio speaker to a transformer, step 8 ohms up to 200 ohms. In a box it is omni in the bass and significantly directional in the highs. Left wide open it is nearly bi-di over most of the audio band.

The problem is the frequency response. I believe the enclosed dynamic will fall 6dB/oct above resonance. With a very-very small box you might get more 500Hz but less below that. To flatten the response you need Acoustic Resistance. In an EV635A, they pack felt very close to the rear of the diaphragm, and adjust the packing at the factory.

The open dynamic may actually be flat over most of the audio band, or up to around 2KHz for a 4-inch. It may get very ratty at higher frequencies, or the shadowing effect of the magnet may smooth that out to a gentle droop.

If Radio Shack still has the $2 1K:8Ω 100mW transformer, that would be fine. Use it backward and use half of the secondary for about 250Ω output. At low levels it is flat 80Hz-8KHz, and I don't think that will get in the way of initial experiments.

Headphone "capsules" also work as dynamic mikes. The way they tune headphones today, I don't want to guess what their reciprocal response is.

Actually, there is a simple way to get a "flat" dynamic. Take a speaker that is "flat" (or flat-enough) when driven with a voltage source (which is how we drive speakers). Connect it to a "zero impedance" input with a 6dB/oct rising response. The microphone frequency response and directivity will be identical to the speaker response. Yes, if you want a mike that sounds-like and beams-like Altec Voice Of The Theaters, just use Altec VOTs with a very custom transformer. (Talk about your big microphones....)

 

[pucho812]

Headphone "capsules" also work as dynamic mikes. The way they tune headphones today, I don't want to guess what their reciprocal response is.

:thumb:
I have done that as well as wired up a speaker for such a purpose b4.

For real fun grab a dead speaker larger the better and wire it to the wall socket. totally kills it. But if you place it on the groud you can watch it dance. :wink: