u/Akirainmission

The Full Story & Theory:

I have a vintage U87 P48 that recently underwent a botched repair. Here is my theory and planned tactical fix:

​The Issue (Thickness Mismatch): After a non-original reskin on the front side, the output dropped by ~10dB. I suspect this sensitivity loss is due to a thickness/tension mismatch between the new front membrane and the original rear membrane.

​The Observation: Upon inspection, the rear membrane and backplate are still the original Neumann components and appear to be in good condition.

​The Tactical Swap: Since the capsule leads are secured by screw terminals (no soldering required), I plan to physically swap the front and rear diaphragm wires.

​The Goal: By reversing the leads, when I select Cardioid mode, the microphone will effectively be using the original Neumann rear-side as its primary pickup.

​My Question to the Experts:

If my theory about the thickness mismatch is correct, will this "flip" restore the original Neumann sensitivity and frequency response for cardioid tracking? Are there any hidden pitfalls (such as backplate polarization issues) that would prevent the rear side from performing exactly like the original front side once the leads are swapped?

Hi everyone,

​Greetings. I’m an engineer returning to the field after a 5-year hiatus—a period I spent immersed in Theological studies. I am now returning to production with a focus on all-around musicality and sonic depth.

​I am currently building a "Sonic Sanctuary" within a very challenging 100sqft (approx. 9sqm) footprint. This studio is located in a high-density urban environment, and the decision to operate within this specific size is a strategic one, aimed at ensuring long-term sustainability by strictly managing rental costs in an extreme real estate market. The studio is a subdivided unit built with solid brick walls. Because of this rigid structure and the proximity of neighbors, low-volume monitoring is a mechanical necessity for sustainable operation.

​It is important to note that I am setting up this space with a very limited budget, utilizing a collection of legacy gear saved from my previous studio sessions. I am looking for the best tactical ways to use what I already have, rather than purchasing new equipment.

​My mission is to fit both a dedicated Isolation Booth (for both Vocals and Guitar tracking) and a full 32-channel Hybrid Analog/Digital mixing station into this single brick-walled room. My goal is to produce international-standard results using a hardware-centric workflow despite these extreme physical, acoustic, and financial constraints.

​The Space & Tactical Setup:

​The Booth (110cm x 140cm): Designed as a multi-purpose space. For Vocals, it serves as a traditional dry booth. For Electric Guitars, it's an "Amp Closet" housing a Kemper Kone.

​The 120cm (4ft) Mixing Corner: Adjacent to the booth, I am surrounding the mixing position on three sides with 60mm (2.4") thick high-density rock wool panels to combat intense early reflections.

​The Monitoring Triad: iLoud MTMs (with built-in ARC DSP calibration), cross-checked with Audio-Technica ATH-R70x and AKG K702 open-back headphones.

​The Hybrid Infrastructure :

​DAW System: Pro Tools HD Native with 32-Out routing & wave plugin

​Console: D&R Vision Analog Console (32-channel onboard analog summing/mixing).

​Dynamics: Stam Audio SA4000 (SSL-style), Black Lion Audio AGB (Diode Bridge), and Vintage Audio va76 FET Compressor.

​Effects (Hardware): Yamaha & TC Electronic Reverb Units, BBE Sonic Maximizer, 1970s Tandberg TCD 420 A Cassette Deck(peramp for coloring) .

​Recording & Tone Tools (The Front-End):

​Microphones: old u87i, Stam Audio 47fet, Lewitt LCT 840 (Tube), AKG C214, Audio-Technica AT4040.

​Preamps: Great River ME-1NV, Universal Audio 710 Twin-Finity.

​Guitar/bass Processing: Marshall JMP-1 (Tube Preamp), sansamp + Kemper Profiler + Kemper Kone.

​My Questions for the Veterans:

​Question 1 (Mixing Corner Acoustics): In a tight 120cm (4ft) mixing corner, I have surrounded the position on three sides with 60mm high-density rock wool acoustic panels.Is this "three-sided" absorption sufficient to manage low-mid accumulation and early reflections, or am I fighting a losing battle with standing waves in such a small, rigid space?

​Question 2 (The Monitoring Strategy): Due to the subdivided unit and neighbor constraints, I must monitor at low volumes. Do you think the ARC-corrected MTMs combined with the R70x/K702 headphones is a reliable enough triad for critical master-bus decisions? Without the ability to "push air" in the room, how should I balance my reliance between the speakers and the headphones to ensure the low-end translates?

​Question 3 (The Guitar "Blend" Strategy): For tracking electric guitars in the booth, I am planning a dual-signal blend: capturing the physical "thump" of the Kemper Kone via microphones while simultaneously tracking a Line Out utilizing Kemper’s internal IR. Do you see any major phase or frequency cancellation issues with this hybrid approach? Any tips for a cohesive blend?

​Question 4 (Booth Acoustics for Vocals & Amps): In the 110x140cm booth, will 60mm rock wool suffice for vocal clarity, or will it suffer from boxy resonance? Should I go 100% "dead," or leave some strategic reflective surfaces to maintain some liveness in such a tiny footprint?

Question 5, any other equipment suggestions or recommendations on the space are welcome, thank you.

​Thanks for your time and wisdom!

​The Situation:

I have a vintage Neumann U 87 P 48 that is currently suffering from extremely low output (approx. 50% lower than normal). I have discovered that the microphone's history involves several questionable repairs, and I suspect the circuit may have been tampered with.

​Detailed Timeline:

​The Original Issue: The mic initially had minor noise, which seemed like a simple loose contact or "scratchy" connection.

​First Repair: The technician decided to replace the capacitors. After this, the microphone worked well for a short period.

​The Failure: Shortly after the capacitor replacement, the mic developed massive, overwhelming noise and static, making it completely unusable.

​Second Repair & Deception: A second technician claimed the capsule was dead and charged for a replacement. The noise disappeared, but the output volume dropped by half.

Current Status: The noise is gone, but the output volume has dropped by approximately 50%. Upon inspection, I can see the original Neumann backplate is still there, but with one new membrane and one original membrane.

What should i do now?