How To Build An Iso Cab

Tube Tone Without The Volume

We've had a number of folks ask about this so I tapped my good friend Chad Smith from and he was happy to oblige.

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. The only problem is, that nice, warm tone often comes at a decibel level greater than most church auditoriums can handle. We’re not really talking about the subjective volume preference of the musicians, FOH team or little old ladies in the front row, but the attempt to actually blend 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. Unfortunately most church buildings can't handle that much volume so using an 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 could use something like a rolling tour box large enough for your cabinet but it 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 build video, parts list & instructions on how to build a custom isolation cabinet that will allow you to keep your tone warm but keep the overall volume of your stage setup at manageable levels. In the example below, our iso-cab reduced overall volume from roughly 98-110db down to ~70db! (full disclosure, this was a rough measurement taken with several iPhone DB meters… not exactly an industry recognized scientific instrument of measurement.)

Here are a few things to keep in mind:

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

-When you build your iso-cab, you will now obviously need a way to mic your amp cab so keep that in mind when determining dimensions. i.e. What kind of mic/stand or hanging mic will you be using?

 -Your volume-reduction results will vary based on materials. 

This list of parts/materials builds TWO matching iso cabinets. The dimensions are cut to fit the cab we were trying to isolate…an Egnater Tweaker 112. Adjust your dimensions to fit your speaker cab needs, microphones, 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 


How To Build An Iso Cab

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So, some of our amps are tube-based. Do you just cut some vents in the lid for the heat?