Award-winning microphone engineering from Michael Joly

- The Ultimate SDC Mod - For 603, 991, GXL1200, CM90, 180

~~$269.00~~ $229.00

Click to enlarge

Better Than $1600/pr KM 184? Listen for yourself below and hear why the "large vent" Ultimate SDC Mod has a been an OktavaMod top-seller since January 2009

"...The high end is sweet, clear and present, but never brittle - just what you would expect from a high-dollar transformerless mic such as, for example, a Schoeps. There's a solid low end that doesn't turn into mush like it does in the original MXL 603s..."

Mike Jasper, Tape Op Magazine, March / April '09

Inspired by a legend -

The condenser capsule used in the 603, 991, CM-54, CM-90, 1200, 180/185, M39, 404, v67n and SC-1 etc with 22 mm body diameter and tapered XLR connector (whew!!) is a decent clone-attempt of the legendary Neumann KM 84 small diaphragm capsule. "Attempt", because the designer of the MXL 603 told me his intention was to create a microphone based on the revered capsule used in both the KM 84 and KM 184 microphones - but his design was not properly implemented due to cost saving measures. After thinking about this conversation I had a Eureka! moment that led to the "Ultimate SDC Mod".

Close comparison of a Neumann KM 184 (below left) and stock MXL 603 (below right) reveals two flaws in the 603 capsule - the 603's diaphragm sits about 5mm away the grille (removed for clarity) creating a cavity that causes resonant chamber coloration. Also, the 603 capsule has a sharp front edge which causes diffraction coloration.

Neumann KM-184 (L), Stock MXL 603 (R)
For contrast, notice the close proximity of the Neumann KM 184 diaphragm to the front edge of its capsule housing. Also note the chamfered front edge of the KM 184 used to decrease edge diffraction. After studying the Neumann capsule design I've pushed my upgrades a step further with the OktavaMod "Ultimate SDC Mod".

This is Michael Joly writing, the founder of OktavaMod. Read on and find out if a mod to your MXL 603 (or look-a-like) is right for you. Then either buy the mod or contact me with your questions.

This upgrade reduces front-of-diaphragm AND back chamber resonance and diffraction coloration. Importantly, these modifications reduce high frequency brightness and provides a spectral balance more similar to the KM 84 as intended by the designer. And of course this mod to your popular SDC includes my field-proven Premium Electronics for improved transient response, detail and clarity.

Listen and judge for yourself -

Listen to the Neumann KM 184 and OktavaMod "Ultimate SDC Mod" - many people have written to say they prefer the OktavaMod sound, do you?

SOUND FILE: Neumann KM 184 Drum OH
SOUND FILE: OktavaMod "Ultimate MXL 603" Drum OH
Special thanks to monster drummer Alan Dossett

The following sound files are high quality 32bit floating point 96K - they will not open in Windows Media Player. Use suitable software (professional DAW or free "Audacity" program) to open.

SOUND FILE: Neumann KM 184 Breedlove acoustic guitar
SOUND FILE: OktavaMod MXL 603 Breedlove acoustic guitar

SOUND FILE: Neumann KM 184 Udu drum
SOUND FILE: OktavaMod MXL 603 Udu drum

SOUND FILE: KM 184 Breedlove acoustic 2
SOUND FILE: OktavaMod MXL 603 Breedlove acoustic 2

SOUND FILE: Neumann KM184 Assorted Shakers
SOUND FILE: OktavaMod MXL 603 Assorted Shakers

SOUND FILE: Neumann KM 184 Speaking voice
SOUND FILE: OktavaMod MXL 603 Speaking voice

If you've taken a few minutes to listen to these files you were probably surprised to hear how great the modified 603 can sound. Like, "lets go to a Neumann shoot out party!" great, right?

The Premium Electronics Upgrade -

The "84-inspired" capsule in these popular SDC mics drives a classic Schoeps-design impedance converter with transformerless output. But to save on production costs, poor-sounding ceramic and under-sized capacitors are used in critical signal path locations along with some circuit topology compromises that limit performance.

I attack these limitations by substituting components and topology field-proven in the OktavaMod "Premium Electronics" mods. These component upgrades and topology changes extend bass while reducing graininess, harshness and mid-to-high frequency distortion. You'll hear how sweet this mic can be in your critical small diaphragm mic applications.

Excessive brightness reduced using a Neumann-proven technique

"Although the KM 184 has the same capsule as the KM 84, the...KM 184 has a gentle rise at about 9 kHz...this difference was achieved with just a slight change of the capsule’s rear opening" (source: Neumann KM 184 web site). In other words, Neumann made the capsule back venting narrower in the KM 184 relative to the KM 84 to impart an on-axis high frequency boost to the KM 184. In my "Ultimate SDC Mod" I reverse this tactic - the vents are enlarged to reduce high frequency peaking at 7.5kHz.

"Ultimate SDC Mod" reduces narrow-band 7kHz peak and adds top end "air" (blue trace). Note: This is a simultaneous comparison of a stock CM-90 and "Ultimate" mod'd CM-90 using program material - not a flat noise spectrum.

The Modification Process -

KM 84-inspired large side vents, close-front diaphragms and rounded front edges.
To deliver these benefits your SDC will be completely disassembled. The PC is board removed and upgraded with superior components including a faster FET with less capsule loading for improved transient response and greater sparkle. All capsule parts (screen, diaphragm, spacer, backplate, spacer and retaining ring) will removed from their housing and safely stored.

The capsule housing of your SDC will be re-machined to eliminate front-of-diaphragm resonance and the front edge radiused to eliminate diffraction coloration. Finally the venting of the mic body will be opened and greater open-area percentage grilles installed to restore a flatter, more "'84-like" spectral balance. When re-assembled all capsules are tuned to an ideal capacitance specification for greatest sensitivity and capsule-to-capsule match.

Enjoy great sound and save money too -

In today's economy its important to get the best return possible from your equipment buying budget. One way to do this is to leverage your existing SDC mics. With just a small additional investment you'll have a beautiful sounding set of small diaphragm mics for drum OH, acoustic guitar, piano and anywhere else you would use high quality small diaphragm mics like the Neumann KM 84.

"Ultimate SDC Mod" top, KM 184 center & KM 84 bottom
(Modified 603 has large vent area like KM 84 for reduced brightness)
Please note - I'm not claiming this mod will turn your mic into a KM 84, there are differences - the '84 is a transformer-coupled mic for starters, but this mod does deliver top flight SDC sound that would be right at home on any hit recording - including one of yours you'll tell me about!

Ordering is Easy -

Click "Add to Cart" to purchase the OktavaMod "Ultimate SDC Mod" for your mic - only $229 (introductory price) for each mic you send to me. You'll get an immediate acknowledgment of your order with my mailing address. By the close of the next business day you'll receive a personal email with your scheduled modification and return ship dates. We'll tell you when your mic has arrived and we'll confirm we've return shipped your upgraded mic on the day we've promised. Questions? Just click "Contact Me" - best, Michael

PLEASE NOTE: Due to internal space restrictions, this modification is not available for the two-switch (low cut & pad) version of these mics such as the MXL 604.

New MJE-K47H Large Diaphragm capsule head for SDC bodies

Award-winning Microphone Design by
Michael Joly

Current Reviews: 11

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