Blue Spark SL Condenser Microphone Quick Test with Acoustic Guitars

Blue’s new Spark SL Large Diaphragm Condenser Mic is the entry level model of the world famous, award winning “bottle” design microphone whose higher end versions are vastly used in professional studios worldwide.

Blue Mics are renowned for they warm full, yet detailed sound. Their flagship iconic blue valve mic lists for around €4k.

The Spark SL

Promising professional quality at an affordable price, this “Red Blue” retains the famous design of its more illustrious siblings, while listing for €195 (at the time of writing) at Thomann.

Coming in a very nice red wooden box, the Spark SL tries to convey a feeling of “affordable luxury” from the very beginning of your experience with it. It also comes with a very nicely designed shock mount, which allows for various orientations of the microphone itself but feels a little “wobbly” .. not very safe.

Spark SL wooden box

The mic itself is very lightweight but feels solidly built.

It features two switches on the front: a 100hz High Pass filter used to remove some “rumble” out of the bottom end, and a -20db “pad” for high sound pressure levels.

Blue positions the Spark SL as a super versatile mic: you can use it for vocals, electric and acoustic guitars, pianos, winds… you name it.

I personally ran a quick test of the mic with acoustic guitar, which is one of the most critical instrument to record. It is very tough to capture all the nuance, depth and dimension of a great acoustic guitar sound.

Guitars I used

  • Bourgeois OMC Vintage Adirondack
    A beautiful, boutique Cutaway OM with a solid Adirondack Spruce top, solid East Indian Rosewood back and sides. Strung with Elixir strings .012 – .053
  • Martin Custom 00-18 DB
    A rare smaller (00 size) Martin with a deeper body for extra bass oomph. Solid sitka spruce top, solid mahogany back and sides. Strung with D’addario EXP .012 – .053

The Test

This test is a quick test. I recorded in an untreated room, placing a single mic at the usual “acoustic guitar” spot: 50-60 cm away from the point where the neck joins the body of the guitar (14th fret in this case).

I tilted the mic about 15 degrees towards the soundhole because it felt like this gave me the most balanced sound. Acoustic guitars can be a little boomy and mic positioning is critical. As for all good mics, Spark SL is very sensitive to minimal changes in position. It requires some time for experimentation and adjustment.

I recorded the same clip with both guitars so to make comparison easier.

For both guitars, I recorded the clip twice: once with the Hi-Pass filter engaged, once with the Hi-Pass filter deactivated. 

Overall, I feel that the hi-pass filter enables the guitar to shine a little bit better on the high end of the frequency spectrum.

On to the results!

Bourgeois OMC, High Pass filter Active.


Bourgeois OMC, High Pass filter NOT Active.


Martin Custom 00 DB, High Pass filter Active


Martin Custom 00 DB, High Pass filter NOT Active


All the clips have been recorded straight to an Apogee Duet Firewire interface, with no EQ, no compression, no limiting. I exported the files in 24 bit WAV format and converted them to 320kbs MP3 using LAME codec.

Do you like the sounds? Do you feel like they are “realistic” given the recording conditions?
Would you like to hear more?

Drop me a line in the comments below!

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