How to Build an Iso Cab

We've had a number of folks ask about iso cabs so I tapped my good friend Chad Smith. He was happy to tell us more about building a custom isolation cabinet to get the smooth tone without the high volume.

It’s the phrase that every electric guitarist dreads hearing from his sound tech or, worse, senior pastor… “you HAVE to turn down the guitar amp!” We all know that the best tone from a tube amp comes when those tubes are nice and warm, but that tone often comes at a decibel level greater than most church auditoriums can handle. It's not just about the subjective volume preference of the musicians, FOH team, or little old ladies in the front row.  It's about actually trying to blend the tone and volume of a live stage amp with the rest of the band coming through the mains.

As much as church musicians love amp modelers, we all know true, high-volume tube tone is tough to beat. Since most church buildings can't handle too much volume,a guitar amp isolation cabinet can be a real tone (and job) saver. The basic idea is to have a place for your speaker cabinet to reside that’s sonically insulated so the outside world can’t hear the actual “loudness” going on. In a pinch, you can use something like a rolling tour box large enough for your cabinet. This just may not get as much “isolation” as a cabinet built to fit your specific needs with actual acoustic dampening foam.

Below you’ll find a video, parts list, and instructions on how to build a custom guitar amp isolation cabinet that will allow you to keep your tone warm while keeping the overall volume of your stage setup manageable. In the example below, our iso-cab reduced overall volume from roughly 98-110db down to about 70db!

*Full disclosure -- this was a rough measurement taken with several iPhone DB meters, not an industry-recognized scientific instrument of measurement.  Your results could be even better with precise measurements!

A few things to keep in mind when building your guitar iso cab:

  -  The method outlined here works for separate amp head isolation cabinets. Please don’t put your pristine Matchless Chieftan combo in a completely enclosed box! The actual tubes and/or amp head need air or you could be dealing with an actual fire. There are ways to partially isolate a combo amp but they should NOT be sealed so they will still have a significant volume leak.

 - Remember your mic setup. When you build your custom iso-cab, you will now obviously need a way to mic your amp cabinet. Keep that in mind when determining dimensions and think about what kind of mic/stand or hanging mic you will be using.

  -  Your volume-reduction results will vary based on materials. This list of parts/materials builds TWO matching guitar amp iso cabinets. The dimensions are cut to fit the cab we were trying to isolate, which was an Egnater Tweaker 112. Adjust your dimensions to fit your speaker cab needs, microphones, cables, etc. 

Parts List

- (2) 4x8 sheets of 3/4" MDF

- 8 Castors

- 16 Right Angle Brackets

- Locking Draw Hatch

- 4 Hinges

- 2 Weather Stripping For Screen Door

- Silicone

- Audio Foam (Auralex is the best option but pricey)

- Screws