SM 57 impedance mods

A little while back I listened to a Home Recording Show episode all about impedance matching (check that episode out here http://www.homerecordingshow.com/2011/08/show-130-microphone-impedance-adjustment-and-more/).

Basically the gist is that some dynamic microphones (like the SM 57) have a much lower impedance than most modern preamps or interfaces. The theory is that this mismatch of resistances between the preamp and mic cause a loss of performance in the mic itself. The SM 57 seems to be the victim of choice because it’s so universal; everyone has one pretty much and knows that while it’s a great sounding mic in just about every single situation, most wish that it could do a bit better. This “mod” basically helps match the impedance a little closer and allows the mic to shine through in it’s full glory. At least that’s the theory.

There are much more complex and expensive mods out there, like replacing or removing the transformer (ie http://www.diyrecordingequipment.com/4001/shure-sm57-sm58-mods/) but this one will only cost about 15$ in total. All it takes is either a short length of dedicated XLR cable or one of the female to male XLR adaptors as well as a resistor of a value which you can determine for yourself. By wrapping the resistor around pins 2 and 3 of the XLR cable/adaptor this changes the impedance value going through the chain.

This article: http://www.recordingmag.com/resources/resourceDetail/330.html goes into much greater detail about the modification and shows you the formula to determine what value of resistor you will need.

Anyways, all of this is good and well in theory, how does it actually sound? In the HRS episode they do a quick shoot out, it uses a “Vari-ohm” which is a device that lets you pick your impedance using a potentiometer which is a lot quicker than swapping resistors in and out the end of an XLR cable, but hey, use whatcha got.

For my test, which isn’t all that scientific by any means, I set up my two SM 57s on my old fender 15 watt bass combo, one going straight into my interface, the other going through an adaptor with 1 of 3 different resistors I tried.  I did one take for each resistor value, giving me one clean, unmodded take and one modded take that would be exactly the same. I dont have a reamp box, so I couldn’t just pump the exact same take out each time. That would have been the ideal way to go about it, but again, use whatcha got.

I got my resistor values by using the formula provided at the end of the the article I posted above. I started by going for about 600 ohms of overall impedance, which gave me a resistor value of 638 ohms (the closest I had was 680 ohms) to go against the 10k ohms of my interface.

The second value was achieved by going for an overall impedance of 310 ohms, the listed impedance of an SM 57 on their website, which gave me a value of 320 ohms. The third value was 25 ohms which matched the value I got by checking my SM 57s with my multimeter. I’m not entirely sure why my 57s seem to have such a low impedance, but I figured I would just give it a shot and see what would happen.

I knew SOMETHING was happening right away because the 25ohm test required a lot of extra gain, nearly 25% more, the 320 ohm test required a little extra (maybe 10% at most) and the 600 ohm test was just about even for both.

I wont say what I thought of each result, I’d like you (if there’s anyone reading this) to make up your mind for yourself. I’ll just say that during a blind test, I didn’t always pick correctly.

Here’s a link to all the audio files, complete with screencaps of each EQ curve (you can see slight differences between the takes in each test, but I dont think that they should be the basis of your decision.

http://www.mediafire.com/?g4rqgxzs9vgb2

Halfway update

So a week ago I left Montreal to depart for Calgary to hang out with my friends from Fall City Fall. We met a few years ago when they were on tour with Breaking the Fourth Wall across Canada. We all immediately hit it off and have remained friends since then.

I decided around Christmas time that I needed to make the most of the most of my time in the coming year and a bit (at the very least) so I got in touch with FCF to come for a visit. They told me they planned on recording in March and that would be the best time to come down. Best part, they were heading to record in Vancouver. I was immediately sold, I’ve never been to Vancouver, or anywhere else in BC before so to get the chance to go there and hang out while they record their new album seemed perfect to me. A few weeks later they let me know that they needed someone to track the bass on the album. Things just seemed to get even better, not only was I gonna get to go on this sweet trip with some awesome friends, I would get to put my stamp on their album.

Fast forward a few weeks, here I sit in Jordon’s basement just south of Calgary watching him play video games and listening to Meat Loaf waiting to go for one final jam before we depart from Vancouver in the van later tonight. I’ve been here for 6 days and had a ton of fun exploring Calgary, eating at Tubby Dog (awesome jumbo hot dog place) and Galaxie Dinner 24 hour breakfast, having 20 cent wings, drinking way too much Tim Hortons (gotta love Roll Up the Rim season) and hanging out in good company.

Best part of all of this, just about wherever I am in the city, if I look out to the west, the Rocky Mountains are there towering in the distance. Walking down the hill out of Keenan and Nathan’s new house north of the city is quite possibly one of the coolest things I’ve seen in a long time. You’re looking out over the suburbs, followed by a some plains and rolling hills and then the stone grey, white tipped wall of mountains reminiscent of the scenery in Lord of the Rings (nerdy, I realize, but that’s what I think every time I see it).

A sight one could definitely get used to. (If only I hadnt forgotten to bring a friggin camera!)

After tonight, I’ll be in the van, on the road to Vancouver for a week taking in a sunrise in the Rocky Mountains. I don’t think it could get much better.